The Third National Workshop on the SKA Project - The Italian Route to the SKAO Revolution

4 Oct 2021, 14:30 → 8 Oct 2021, 13:00 Europe/Rome

Virtual

The Italian National Institute for Astrophysics (INAF) invites the astrophysical community to attend the “The Third National Workshop  on the SKA Project - The Italian Route to the SKAO Revolution”, that will be held on 4-8 October 2021.

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Important Deadlines:

Call for abstracts: 15 July 2021

Registration: 15 September 2021

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Programme: A preliminary version of the programme is now available. See "Timetable". All indicated times are CEST.

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Workshop description and aims

The establishment of the SKA Observatory (SKAO) in February 2021 has formally started the process leading to the construction of one of the mega-science facilities of the 21st Century, with full operations planned by 2030. With nearly 200 dishes in South Africa and more than 130,000 antennas in Western Australia operating across the radio spectrum, the SKAO’s telescopes will transform our understanding of the Universe. 

Awaiting the SKAO’s telescopes, radio astronomy is rapidly advancing under the impulse of a number of new, state-of-the-art facilities, collectively known as precursors and pathfinders. In particular, the advent of LOFAR, and more recently ASKAP and MeerKAT, has considerably broadened the observational parameter space, and opened new windows on several astrophysical areas. The SKA project (and to some extent its precursors) will enable a wealth of unique discoveries in areas as diverse as the formation of Earth-like planets, the detection of gravitational waves, the origin of cosmic magnetic fields, the formation and growth of stars, galaxies and black holes, as well as large scale structures, back to the epoch of reionization and cosmic dawn. In fact the SKAO’s telescopes will revolutionize our knowledge in all fields of modern astrophysics and cosmology, and will have important scientific applications also in the field of general and astro-particle physics.

The SKAO’s telescopes are designed to be survey instruments, and it is envisaged that a large fraction of their observing time will be dedicated to the execution of large surveys, organized in international Key Science Projects (KSPs). Nevertheless a fraction of the observing time will be available to PI-led proposals. The SKA project science case is expected to evolve rapidly in the near future, thanks to the new results from precursors and pathfinders. The exploitation of these facilities will naturally lead to the definition of the SKA KSPs, to the development of new data analysis skills, and ultimately to the formation of international KSP teams. 

Italy, through INAF, has been involved in the project since the establishment of the SKA Organization (2012) and it is one of the six countries that founded the new born SKA Observatory. On the way to SKAO operations, INAF joined the International LOFAR Telescope (ILT) in 2018 and the MeerKAT+ project (an extension of MeerKAT) in 2020. In addition to this, INAF is working towards the establishment of a dedicated data analysis facility which will join the so-called SKA Regional Centers (SRC): a distributed network of data centers housing high-end computing facilities for data processing and long-term archiving. SRCs are also expected to provide proposal preparation and data handling support to SKA users.

The main goals of this Third National Conference are:

a) to review the ongoing scientific activities in Italy in preparation for the future SKA surveys. Particular emphasis will be given to results from precursors and pathfinders, SKA-related theoretical/simulations studies, as well as ideas for synergistic use of other facilities.

b) to present and coordinate ongoing activities towards the development of an Italian SKA Regional Center, as part of the INAF Computing Facility. Data analysis expertise is essential for strong and competitive KSP teams under Italian leadership. 

c) to discuss a national scientific roadmap towards full exploitation of SKA surveys with the broader astrophysical community, and start to organize the future SKA KSP teams.

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The SKA Observatory from an Italian Perspective Session_04MonAft

Monday 4 October

The SKA Observatory from an Italian Perspective: chair G. Umana

Recording

1 Welcome - Introduction from INAF President

Speaker: Marco Tavani (INAF)

2 SKAO: Current Status

Speaker: Philip Diamond (SKAO)

Phil Diamond - SKA Status Italy 4Oct2021.pdf

3 SKAO from an Italian perspective

Speaker: Isabella Prandoni (INAF-IRA)

Prandoni_SKA_Italy2021print.pdf

4 SKA Regional Centres - Italian Contribution

Speaker: Andrea Possenti (INAF - OA Cagliari)

Italian_role_in_SRC_Possenti_ok.pdf

15:50 Break

The SKA Observatory from an Italian Perspective: chair F. Govoni

Recording

5 The LOFAR International Telescope - Italian Involvement

Speaker: Gianfranco Brunetti (INAF - IRA)

LOFAR-It_SHORT_Brunetti.pdf

6 Mid-frequency SKA Precursors - Italian Involvement and opportunities

Speaker: Grazia Umana (INAF - OA Catania)

Umana_ska_2021.pdf

7 Italian development for SKAlow

Italy and in particular INAF played a very important role in the design and development of SKA-low, with a working group that includes colleagues from INAF, CNR-IEIIT, UNIBO, UNFI and Politecnico di Torino. participated in all phases of the project from its conception in 2002 to today.
INAF’s participation in the various consortia started with SKADS, in which the embryonic ideas of the technology still used today were developed (like RF over Fibre – RFoF and digital beamforming), and continued with the international consortia (Aperture Array Verification Program and Aperture Array Design Consortium) including the current bridging phase. This path culminated with the development of almost full know-how of the receiving chain for the SKA-low antenna.
At the present stage we are working with our national industrial partners to prepare for the production phase: this phase will guarantee the transfer of cutting-edge technologies as well as a geographical return of the SKA investments.

Speakers: Jader Monari (Istituto Nazionale di Astrofisica (INAF)), Dr Giulia Macario (Istituto Nazionale di Astrofisica (INAF))

Italian_Development_SKALow_Monari_Macario.pdf

8 Italian contributions to SKA Control Software

The Square Kilometre Array (SKA) project is too large to be managed with simple approaches and tools, due to the ensemble of interacting hardware and software which make the control and monitor task extremely complex. We have now identified the right tools to solve this task, and the current challenge is to find the smartest strategies to implement the whole SKA project by using those tools.

The current efforts performed by the three Italian teams working on this software challenge are presented here. Four main areas of work are involved:
1)Hardware control in the Low telescope aperture array beamformer (LFAA)
2) Monitoring and control of the CSP (Central Signal Processing) and of its interactions with Telescope Manager and real processing HW sub-elements.
3) Development of a flexible and easy-to-use tool for quickly creating engineering user interfaces for TANGO devices monitoring and control (Taranta).
4) Implementation of continuous integration and continuous delivery (CI/CD) practices for the SKA software, including services (monitoring, logging) for the life-cycle control and maintenance.

Speaker: Giovanni Comoretto (Istituto Nazionale di Astrofisica (INAF))

Italian_role_in_SKA_SAFE_Comoretto_Baffa.pdf

9 Development of Phased Array Feeds - Italian contribution

Speaker: Alessandro Navarrini (INAF - OA Cagliari)

Navarrini_PAF_SKA-Italy_4Oct2021.pdf

Tuesday 5 October

Pulsars: chair A. Possenti

Recording

10 Pulsar Science with MeerKAT

In this talk I will report on the MeerKAT key science projects related to pulsars, and on the leading role that the italian scientific community is playing in these programs. I will, in particular, summarise the discoveries (50, at the time of writing, and counting) already done as part of the TRAPUM KSP, a project aimed at searching for new interesting pulsars in a series of targeted observations. I will also report on the timing results obtained in the MeerTime project, whose aim is to exploit the clock-like nature of pulsars to use them as laboratories for fundamental physics. The results obtained so far, along with the observing and data reduction strategies adopted, are paving our way towards a successful exploitation of the SKA.

Speaker: Marta Burgay (Istituto Nazionale di Astrofisica (INAF))

Burgay.pdf

11 Pulsars in globular clusters with the SKA precursors and pathfinders

Globular clusters (GC) are spherical, self-gravitating collections of stars that orbit our Milky Way. Thanks to their extreme stellar densities, which favor frequent gravitational interactions between the stars, GCs are prolific factories for generating millisecond pulsars, exotic binary systems and pulsars with unusual, and often extreme, properties. All of this makes GCs outstanding laboratories, and their pulsars can be exploited for a large variety of experiments: they can be used to test General Relativity, study binary evolution, probe the cluster's gravitational potential in search of non-luminous matter, detect possible intra-cluster ionized gas, study the Galactic magnetic field, and more.

The advent of the MeerKAT radio telescope, a precursor of the SKA1-mid, has recently given a major upturn in the science of pulsars in GCs. Being 4-6 times more sensitive than the Parkes radio telescope and up to 2 times more sensitive than the Green Bank Telescope, MeerKAT has been providing us with an entirely new view of the southern sky. Since the beginning of our observing programme, started in 2019, 34 new pulsars have been discovered in 11 different clusters. A few of these show interesting characteristics that are worthy of attention. Moreover, several of the previously known pulsars have been re-observed with MeerKAT, resulting in new studies made with unprecedented details.

GCs have also been observed with NenuFAR, an SKA pathfinder. The extremely low frequencies at which this telescope can observe pose several challenges both from an observational and computational standpoint, which need to be overcome to successfully detect the faint and fast pulsar of GCs.

In this talk, I will report on the GC pulsar observing programmes currently ongoing at MeerKAT and NenuFAR. Besides producing high-impact scientific results, these activities are essential to gain the necessary experience to fully exploit the outstanding capabilities that the SKA1-mid and SKA1-low will offer for the science of pulsars in GCs.

Speaker: Alessandro Ridolfi (Istituto Nazionale di Astrofisica (INAF))

Ridolfi.pdf

12 Pulsar Timing Arrays and the SKA

One of the top science goals for SKA is the study of pulsars, and in particular using pulsars in so-called pulsar timing arrays (PTAs) to detect low-frequency gravitational waves (GWs). The regular monitoring (or timing) of a large number of millisecond pulsars (MSPs) is essential to making a GW detection. Pulsar surveys with SKA1 will reveal a large new population of millisecond pulsars (MSPs): we expect a total of 700-900 new MSPs with SKA-MID and 400-900 MSPs with SKA-LOW. The large scale SKA1-MID will allow the high precision timing of many known MSPs for GW detection and should lead to a GW detection within 2 to 6 years. Pulsar timing with the SKA will build on the current MeerKAT capabilities and the MeerTime pulsar timing program, whose results are very encouraging for future SKA1 capabilities. Pulsar timing data from MeerKAT and the SKA will also be merged with pulsar timing data from the International Pulsar Timing Array (IPTA) which includes the European Pulsar Timing Array (EPTA) collaboration. The SKA’s southern position is strategic and nicely complements the other PTA telescopes around the world. In Italy, we have observing and theoretical expertise with pulsars, PTAs and SKA. A few members of the INAF-Osservatorio Astronomico di Cagliari pulsar group are members of the SKA working groups on pulsars. Additionally, several members are part of the EPTA and the Large European Array for Pulsars (LEAP) which combines the simultaneous data from the five European EPTA telescopes, including the Sardinia Radio Telescope, and already has SKA1 capabilities; we also have theoretical expertise on PTAs at the Universita di Milano-Bicocca, as well as expertise on combining PTA and Gaia data at INAF-Torino. All of this places us in a strategic position to develop SKA capabilities for pulsars and to analyze and exploit future SKA pulsar data for GW detection.

Speaker: Delphine Perrodin (Istituto Nazionale di Astrofisica (INAF))

PTA_SKA_Perrodin.pdf

13 Advantages of the Inclusion of Globular Cluster Millisecond Pulsars in Pulsar Timing Arrays

Pulsar Timing Arrays (PTAs) are collecting years of data by constantly monitoring the radio emission from the most stable millisecond pulsars (MSPs) across the sky in order to detect variation between the observed time of arrival of each pulse and the one expected from the timing model (i. e. the timing residual) that can be induced by gravitational waves (GWs). This technique, called pulsar timing, is the only one that allows to ``hear'' ultra-low frequency GWs, that may be generated by sources relevant for cosmology (e. g. cosmic strings) and astrophysics (e. g. super-massive black hole binaries) and form the gravitational wave background (GWB). In spite of the fact that PTAs should already have the potential to detect the GWB, by finding a quadrupolar correlation in the timing residuals, the goal has not been achieved yet.

The GW-induced timing residual depends on the difference between the metric perturbation at the position of the observer (called Earth term) and the metric perturbation at the position of the pulsar (called pulsar term). This implies that the GW-induced timing residual of pulsars located in almost the same position is expected to be approximately equivalent. Such effect can be only observed in a globular cluster (GC), where tens of MSPs are confined within a very small distance from the center.

We suggest the possibility of including GC MSPs in PTAs. Currently, these MSPs cannot be timed with a precision adequate for the detection of GW-induced variations on timing residual, mainly because of the effects induced on the MSPs dynamics by the gravitational potential. Nevertheless, we expect that the situation will change in the near future thanks to new powerful detectors, like the Five hundred meter Aperture Spherical Telescope (FAST), the MeerKAT radio telescope and the Square Kilometre Array (SKA). SKA, in particular, will certainly play a crucial role in ultra-low frequency GW detection. With its unprecedented sensitivity it will be possible to time significantly better the GC MSPs, opening, within the next decade, the possibility of adopting the strategy proposed in this work.

The interest in GC MSPs is well motivated by the fact that each of them respond in a very similar way to a GW, that would give an additional ``smoking gun'' for the GW detection. Moreover, the globular cluster distance is often known with great precision and this allows to take into account the pulsar term which, in current analysis, is treated as an additional noise source because of the difficulties in the determination of the precise distance of the isolated pulsars. It has to be noticed that including the pulsar term in the analysis is relevant since it depends on the angular coordinates of the GW source and must be considered in order to estimate its position. Finally, since in some cases the inter-pulsar distance is extremely small, the random contribution to the timing residuals can be reduced by an opportune averaging procedure.

Speaker: Michele Maiorano (Università del Salento)

Maiorano.pdf

10:50 Break

Transients & Gravitational Waves: chair G. Bernardi

14 Prepping up for the SKA Fast Radio Bursts era using the Northern Cross

Fast Radio Bursts are enigmatic, millisecond-long, bright (typically 1-100 Jy) radio flashes of (mostly) cosmological origin (up to z ~ 2). At the time of writing, a few hundreds of events have been observed with a large range of properties in terms of fluences, spectra, time smearing and characteristics of the host galaxies - when localized. Their origin remains indeed largely debated, although an unmistakable connection between magnetars and (some) FRBs has been established recently. In the future, the SKA will provide observability over two frequency decades with simultaneous, superb localization, ie. FRB cosmology.
In this talk I will review the Northern Cross FRB project, the ongoing effort to equip and use the Northern Cross (NC), the oldest Italian radio telescope, to observe FRBs. The NC North-South arm has been upgraded with state-of-the-art electronics and backends suitable for FRB observations. Commissioning activities started in 2019. I will present the current project status, highlighting the first FRB detections. Finally I will describe the future path, including the equipment of the 64 cylinders of the North-South arm that will lead to a low frequency telescope similar to CHIME and, therefore, an effective Italian FRB survey machine that will be able to give the Italian FRB community a leading role in the SKA era.

Speaker: Maura Pilia (Istituto Nazionale di Astrofisica (INAF))

MPilia_SKA3.pdf

15 HIGH-RESOLUTION AND HIGH-SENSITIVITY WANTED: THE IMPACT OF SKA ON GRBs

Gamma-Ray Bursts (GRBs) are the most powerful explosions in the Universe. They are thought to be generated by the collapse of a massive star (long GRBs) or a NS-NS or NS-BH merger (short GRBs). Regardless of the progenitor's nature, a spinning, stellar mass BH or a highly magnetized NS is eventually produced, and this central engine launches a jet of ionized matter which interacts with the circum-burst medium, producing the so-called afterglow emission. The radio band and in particular VLBI already proved to be unique tools to investigate the superluminal motion, the expansion and the structure of the jet. However, high-sensitivity, high-resolution facilities are needed to detect radio afterglows and to resolve the host galaxy contribution out. In this talk I will discuss two representative cases: GRB 201015A and GRB 200716C. The former has been studied thanks to the high resolution of e-MERLIN and EVN, which allowed us to distinguish the proper afterglow emission from the host galaxy contribution, but a higher sensitivity could have strongly improved the modeling. On the other hand, the host galaxy of GRB 200716C shows an unusual spectrum which can be explained with an incredibly high star formation rate, a weak AGN or a combination of them. Since the galaxy has not been resolved yet, the high resolution provided by VLBI would solve the conundrum. These two cases are the tip of the iceberg of a population that could easily be studied with the SKA, thanks to its sensitivity, angular resolution, and surveying capabilities.

Speaker: Stefano Giarratana (Istituto Nazionale di Astrofisica (INAF))

Giarratana.pdf

16 Combining gravitational waves with SKAO observations

I will review the possibility to combine galaxy and intensity mapping observations from the SKAO with gravitational waves (GW) detected by laser interferometers. Cross-correlating Large Scale Structure (LSS) data with GWs it will be possible to test the existence and abundance of primordial black holes and perform innovative tests of gravity. Finally, I will explore new ideas for testing the physics of the early Universe by combining LSS SKAO data with GWs.

Speaker: Alvise Raccanelli (Universita' di Padova)

Cosmology: chair S. Camera

Recording

17 Intensity Mapping in the post-reionization era

I will review the theoretical challenges to model the HI content in the post-reionization universe. I will address both astrophysical and cosmological questions that can be addressed by exploiting the 21 cm signal with SKA.

Speaker: Prof. Viel Matteo

VIEL_SKAO.pdf

18 Blind Foreground Subtraction Challenge for SKAO HI Intensity Mapping: methods used and perspectives

HI Intensity Mapping (IM) surveys with the telescopes (and precursors) of the SKA Observatory are a promising, independent, and insightful way of studying the large-scale of the Universe. However, strong astrophysical foregrounds contaminate the signal, and their coupling with instrumental systematics further increases the complexity of the data cleaning. As an effort of the HI IM Focus Group of the SKAO Cosmology Science Working Group, we have performed the first Foreground Subtraction Blind Challenge for HI single dish IM.
We asked: if we were given some actual data today, what could we achieve using the available pipelines? Nine different cleaning pipelines joined the Challenge: based on statistical learning techniques (PCA, ICA, GMCA), on a new hybrid algorithm (mixGMCA), on a blind polynomial fitting method, and a more astrophysical-informed parametric fit to foregrounds. We performed the cleaning on realistic data cubes for both a MeerKAT and a SKAO1-MID set-up, with no knowledge of the ground truth or the beam's full shape. Here, I discuss the pipelines that joined the Challenge and compare their cleaned maps against the input maps. We found a large scatter in the results among methods, observational set-ups, and pre-processing steps. We particularly stress how mixGMCA, devised ad-hoc for IM, outperforms the methods from which it stems. Blind Challenges are an excellent tool for testing methods and best practices, and learning as a community.

Speaker: Isabella Paola Carucci

carucci_TNW.pdf

Cosmology: chair S. Camera

Recording

19 Multiwavelength Cosmology with SKAO

I will discuss the cosmological constraints from the combination and cross-correlation of radio, optical, and microwave cosmological observations in order to obtain precise measurements of perturbations on large scales.
Specifically I will show that a conservative combination of an SKAO-MID HI intensity mapping survey with the galaxy clustering from two photometric galaxy surveys (Euclid- and LSST-like), and with CMB lensing from CMB-S4, could reach tight uncertainties for primordial non-Gaussianity parameters and total neutrino mass.

Speaker: Mario Ballardini (Istituto Nazionale di Astrofisica (INAF))

Ballardini.pdf

20 RadioLensfit: an HPC Tool for Accurate Galaxy Shape Measurement with SKA

The new generation radio telescopes, such as the Square Kilometre Array (SKA), are expected to reach sufficient sensitivity and resolution to provide large number densities of resolved faint sources, and therefore to open weak gravitational lensing observations to the radio band. In this talk I will present RadioLensfit, an open-source tool for an efficient and fast galaxy shape measurement for radio weak lensing shear. It performs a single source model fitting in the Fourier domain, after isolating the source visibilities with a sky model and a faceting technique. This approach makes real sized radio datasets accessible to an analysis in this domain, where data is not yet affected by the systematics introduced by the non-linear imaging process. The code is also able to exploit multi-node HPC infrastructures by a hybrid parallelization MPI+OpenMP for accelerating the computation and dealing with very large datasets, that possibly cannot entirely be stored in the memory of a single processor. Using SKA-MID simulated datasets, I will present performance results both in terms of code scalability and measurement accuracy at the expected SKA1 source density, showing that results are comparable with a joint fitting approach but with a computational time highly reduced. Finally I will discuss the work that is on-going with the data of the UK e-MERLIN legacy project SuperCLASS, a precursor weak lensing survey performed combining the SKA pathfinder telescopes e-MERLIN and JVLA.

Speaker: Dr Marzia Rivi (Istituto Nazionale di Astrofisica (INAF))

Rivi_talk.pdf

Epoch of Reionization: chair A. Mesinger

21 Learning about the first galaxies with 21-cm: the first results from HERA

The cosmic 21-cm signal observed by the Square Kilometre Array (SKA) will open a new window to the early Universe. 21-cm fluctuations encode the properties of the unseen first galaxies as well as physical cosmology. I will showcase our fully Bayesian inference framework, capable of forward-modeling 4D realizations of cosmic 21-cm lightcones. I will demonstrate how this framework was recently applied to preliminary results from the Hydrogen Epoch of Reionization Arrays (HERA). The preliminary HERA limits already allowed us to constrain the IGM thermal evolution and X-ray luminosities of the first galaxies. In particular, we find that the first galaxies must have been more X-ray efficient (with a higher X-ray luminosity to star formation rate) than local ones, consistent with theoretical predictions of High Mass X-ray Binaries (HMXBs) in low metalicity environments.

Speaker: Dr Qin Yuxiang (University of Melbourne)

HERA.pdf

22 Chasing the Cosmic Dawn with LEDA

Total-power radiometry with individual meter-wave antennas is a potentially effective way to study the Cosmic Dawn ($z\sim20$) through measurement of the sky brightness arising from the $21$~cm transition of neutral hydrogen, provided this can be disentangled from much stronger Galactic and extra-galactic foregrounds. In the process, measured spectra of integrated sky brightness temperature can be used to quantify the foreground emission properties.
In this talk, I present results from a subset of data from the Large-aperture Experiment to Detect the Dark Age (LEDA) in the $50-87$~MHz range. I will present the constraints on the foreground spectral index $\beta$ in the northern sky visible from mid-latitudes, focusing on two zenith-directed LEDA radiometers, and discuss how estimates of $\beta$ vary with local sidereal time (LST). Combining all data gathered during the extended campaign between mid-2018 to mid-2019, I will discuss the progress made in the quest for a cosmological signal.

Speaker: Marta Spinelli (Istituto Nazionale di Astrofisica (INAF))

Spinelli_LEDA.pdf

15:50 Break

Epoch of Reionization: chair A. Mesinger

23 Forward-Modelling SKA Beam Errors in 21cm Parameter Estimation Experiment

Detection of signals from the Epoch of Reionization (EoR) is one of the new frontiers in observational cosmology. However, predictions of the ability of 21-cm experiments to discriminate EoR signal models are typically limited by the simplicity of data models, in which the effects of foregrounds and characteristics of the instrument are often neglected. Current experiments have shown that these components are crucial in determining the detection prospect of the EoR because their presence can introduce unwanted structures in the observation data. To move towards more realistic scenarios, we had previously added a simple foreground and instrumental model and showed their effects on reionization constraints. Currently, we are exploring the effects of applying a realistic perturbed beam model and the ability to discriminate the EoR astrophysical parameters. We use 21cmFAST to efficiently generate the brightness temperature fluctuations from the EoR and the publicly available OSKAR package to generate the beam of the future Square Kilometre Array. We also extend the current prescriptions of the plug-in code, py21cmMC_fg, to account for beam perturbation and earth rotation synthesis. The analysis framework we develop is useful for upcoming 21cm experiments, providing insights into the effects of beam perturbation in the presence of foregrounds on astrophysical parameter estimation.

Speaker: Ainulnabilah Nasirudin (Scuola Normale Superiore)

talk_ABNASIRUDIN.pdf

24 Optimal compression of the cosmological 21cm signal

With the Square Kilometre Array (SKA), through the cosmic 21cm signal, we will soon have images of the first billion years of our Universe. Inferring the (unknown) UV and X-ray properties of the first galaxies from the highly non-Gaussian patterns of such images is a challenging problem where there is no obvious choice of a summary statistic (image compression). For this purpose, neural networks (NN) have proven as a viable and important tool, as they adaptively select a summary that maximizes their ability to recover astrophysical and cosmological parameters. Here, besides convolutional NNs, we introduce the recursive NN architectures, which can optimally take advantage of the correlation in the cosmic signal between neighboring frequency bins. Using realistic 3D mock data, including SKA noise as well as foreground dominated wedge excision, we demonstrate that constructed networks outperform other commonly used architectures, enabling precise parameter recovery even in the presence of strong foregrounds. Moreover, we use NNs to optimally compress the cosmological 21cm signal and find a summary which maximizes extracted information. Using likelihood free inference, we are able to recover Bayesian posterior of the astrophysical properties encoded in the signal.

Speaker: David Prelogovic

Prelogovic_optimal_compression.pdf

Magnetism: chair V. Vacca

25 Large-scale magnetic fields unveiled by LOFAR

Background Faraday-rotation studies have proven to be excellent tools for the detection and the study of large-scale magnetic fields. As an SKA pathfinder, LOFAR is exploring the low-frequency regime, where polarization observations are crucial to unveil the weak magnetic field outside galaxy clusters. As a uniform grid of Faraday-rotation measures (i.e., radio galaxies) is becoming a reality, the study of large-scale magnetic fields is able to obtain more stringent constraints on the magnetization of the cosmic web. In this talk I will present the results of two background Faraday-rotation studies: othe first is based on the detection of polarized emission from the lobes of giant radio galaxies, while the other is based on a statistical study of the Faraday-rotation in the background of optically identified cosmic web filaments.

Speaker: Chiara Stuardi (Istituto Nazionale di Astrofisica (INAF))

SKAOita_Stuardi.pdf

26 MeerKAT and ASKAP synergies: the discovery of a depolarizing HI tail in the western lobe of Fornax A

The MeerKAT Fornax survey (MFS, P.I. Paolo Serra) will observe the galaxy cluster Fornax including the in-falling group of Fornax A. This project has two primary goals: to study the evolution of galaxies throughout the associated HI emission and to determine the intracluster magnetic field thanks to the polarization properties of cluster-embedded and background radio sources.
In the context of the MFS activities, we found a spatial coincidence between tidal HI material, T$_{N}$ in Kleiner et al. 2021, detected with MeerKAT in the western lobe of Fornax A and a depolarized structure observed with the Australian Square Kilometre Array Pathfinder (ASKAP) at 1.2 GHz. We analyzed the properties of the rotation measure images obtained with ASKAP data along the HI tail location and in the neighborhoods. According to our analysis the HI tail is carrying its own magnetic field across the western Fornax A lobe with a strength of the order of $\sim$11 $\mu$ G. This is the first observed evidence of a magnetic field driven throughout a radio galaxy lobe.

Speaker: Francesca Loi (Istituto Nazionale di Astrofisica (INAF))

LOI_Francesca.pdf

27 Spectral index of synchrotron emission: insights from the diffuse and magnetised interstellar medium

The interpretation of Galactic synchrotron observations is complicated by the degeneracy between the strength of the magnetic field perpendicular to the line of sight (LOS), $B_\perp$, and the cosmic-ray electron (CRe) spectrum. Depending on the observing frequency, an energy-independent spectral energy slope $s$ for the CRe spectrum is usually assumed: $s=-2$ at frequencies below $\simeq$400 MHz and $s=-3$ at higher frequencies.
Motivated by the high angular and spectral resolution of current facilities such as the LOw Frequency ARray (LOFAR) and future telescopes such as the Square Kilometre Array (SKA), we aim to understand the consequences of taking into account the energy-dependent CRe spectral energy slope on the analysis of the spatial variations of the brightness temperature spectral index, $\beta$, and on the estimate of the average value of $B_\perp$ along the LOS.
We use 3D magnetohydrodynamic simulations of the diffuse, magnetised, multiphase, turbulent, and neutral atomic interstellar medium (ISM) as input for the magnetic field to study the variation of $\beta$ over a wide range of frequencies ($\simeq0.1-10$ GHz).
We find that the common assumption of an energy-independent $s$ is only valid in special cases. We show that for typical magnetic field strengths of the diffuse ISM ($\simeq$2$-$20 $\mu$G), at frequencies of 0.1$-$10 GHz, the electrons that are mainly responsible for the synchrotron emission have energies in the range $\simeq$100 MeV$-$50 GeV. This is the energy range where the spectral slope of CRe varies to the greatest extent. We also show that the polarisation fraction can be much smaller than the maximum value of $\simeq 70\%$ because the orientation of ${\bf B}_\perp$ varies across the beam of the telescope and along the LOS.
Finally, we present a look-up plot that can be used to estimate the average value of $B_\perp$ along the LOS from a set of values of $\beta$ measured at different frequencies, for a given CRe spectrum. This plot turns out to be particularly useful for SKA and a number of its pathfinders and precursors (HERA, MWA, MeerKAT, LOFAR, and ASKAP).

Speaker: Marco Padovani (Istituto Nazionale di Astrofisica (INAF))

Padovani.pdf

Wednesday 6 October

Non-Thermal Processes in Galaxy Clusters: chair G. Brunetti

Recording

28 The physical fate and observable properties of fossil radio electrons in large-scale structures

Low-frequency observations with SKA's precursors and pathfinders are unveiling an exciting new variety of complex radio morphologies, associated with ageing and re-accelerated plasmas injected by radiogalaxies.
It is becoming increasingly evident that we need to better model the evolution of such "fossil" electrons, in order to understand the reservoir of electrons which accretion phenomena use to produce large-scale diffuse radio emissions, which the SKA will observe with unprecedented detail and statistics.

I will present recent numerical modelling of the evolution of radiogalaxies and of their remnant lobes long after their release into the intracluster medium (Vazza et al. 2021 A&A https://arxiv.org/pdf/2102.04193.pdf), as tool to better interpret existing low-frequency radio observations, and prepare for the modelling of future deeper SKA data.

Speaker: Franco Vazza (Istituto Nazionale di Astrofisica (INAF))

Vazza.pdf

29 The LOFAR LBA sky survey: learned lessons

The LOFAR Low Band Antenna (LBA) system makes LOFAR a case-of-study for the exploration of ultra-low frequencies (<100 MHz). Understanding how to collect, store, reduce and analyse LOFAR LBA data, is key to have a fast track towards SKA-low science.

In this talk I will give an overview of the LOFAR Sky Surveys with emphasis on the LOFAR LBA Sky Survey, describing the planning, status, data analysis process, and data releases. The survey aims to cover the northern sky in the frequency range 42-66 MHz, reaching the sensitivity of 1 mJy/b at the resolution of 15 arcsec. Thanks to this experience we have now a set of proven-working multi-beam observing schemes, as well as simulation and data reduction codes that can be directly applied to SKA-low observations.

As an example science case, I will present how such data can be used to examine the ultra-low frequency radio emission from low-energy populations of cosmic rays in galaxy clusters giving an overview on the on-going research.

Speaker: Francesco De Gasperin (Istituto Nazionale di Astrofisica (INAF))

deGasperin.pdf

30 Galaxy clusters in the LOFAR Two-meter Sky Survey

The LOFAR Two-meter Sky Survey (LoTSS) is an on-going survey aimed at imaging the entire northern sky at 120-168 MHz with unprecedented resolution and sensitivity in this frequency range. It had its first data release in 2019 and a new, second data release is forthcoming. LoTSS-DR2 will comprise images for 5700 square degrees of the northern sky, where more than 4 million radio sources have been detected. One of the main goals of this survey is to study diffuse synchrotron sources in galaxy clusters, such as radio halos, mini-halos, relics, and AGN with extended emission. In this talk, I will present the results from the analysis of all the 309 galaxy clusters detected by the Planck satellite that reside in the LoTSS-DR2 area. I will discuss the challenges faced during the analysis of this large sample and summarize the properties of the sources observed, showing how LoTSS observations are allowing us to expand the parameter space of galaxy cluster studies. This project represents the largest search for diffuse synchrotron sources in the intra-cluster medium performed to date and the first statistical study dealing with hundreds of clusters covered by deep low-frequency radio observations.

Speaker: Andrea Botteon (Leiden Observatory)

Botteon.pdf

31 A renewed look at the impact of jetted AGN in the SKA era

In recent years the unprecedented sensitivities provided by SKA precursors/pathfinders have started revolutionising our view even of previously well-known objects such as jetted AGN. In particular, observations in the MHz-frequency regime are able to unveil the oldest plasma injected by AGN jets in their surrounding medium, providing new insights into the jet duty-cycle and feedback, as well as into their interaction with the external medium over very long timescales. Here, I will present some spectacular systems, where we have detected old AGN plasma with complex filamentary morphology, which is interacting with the surrounding gas. These are clearly showing how the particles injected by AGN jets into their environment can get transported and distributed across the entire host system.
In particular, I will focus on a unique galaxy group called Nest200047, which we have investigated using LOFAR observations at 53 and 144 MHz combined with eROSITA data in the 0.5-2 keV-band. Here we have detected the late evolution of multiple generations of cosmic-ray AGN bubbles with an extraordinary level of detail. These have first transformed into toroidal (‘mushroom-shaped') structures and are now in the process of getting shredded into a multitude of filamentary substructures. Interestingly, despite a long and apparently rather complicated evolution, even the oldest radio plasma is not yet thoroughly mixed with the thermal plasma after hundreds of million years, likely under the action of magnetic fields. However, this lack of mixing by no means seems to reduce the efficiency of the AGN feedback, suggesting that the energy exchange between the bubbles and the surrounding medium happens without a thermal coupling between the two phases.
Overall, all these systems clearly anticipate the major role SKA will play in the advancement of our understanding on the impact of AGN jets on their surrounding environment.

Speaker: Marisa Brienza (Istituto Nazionale di Astrofisica (INAF))

brienza-ska-oct6.pdf

10:50 Break

Non-Thermal Processes in Galaxy Clusters: chair R. Cassano

Recording

32 Ultra-steep diffuse emission outside the cluster core observed with LOFAR at 144 MHz in cool-core galaxy clusters

Diffuse radio emission at the center of galaxy clusters is observed with different size and properties.
Gian halos are Mpc-size sources predominantly found in massive merging clusters and are likely due to the re-acceleration of particles by turbulence injected in the intra cluster medium (ICM) during major merger. Mini halos are 100-500 kpc-size sources found in relaxed clusters with a cool-core.
Their origin is still unclear, they could be either due to re-acceleration of particles by turbulence connected with the sloshing of the cluster core after a minor merger, or to the continuous injection of electrons by inelastic collisions of relativistic cosmic-ray protons with the cluster thermal proton population.
Giant halos and mini halos are thought to be distinct classes of sources. However, recent observations have revealed the presence of diffuse emission on Mpc scales in clusters that are relaxed.
These sources suggest that minor mergers – while not sufficiently energetic to disrupt the cool-core – could still trigger particle acceleration in the ICM on scales of hundreds of kpc, generating ultra-steep spectrum emission ($\alpha\ge1.5$).
To test this hypothesis and the occurrence of this emission, we observed with the SKA precursor LOFAR (LOw Frequency ARray) at 144 MHz a sample of eleven clusters with a cool-core and some level of dynamical disturbances, estimated from X-ray observations.
In this talk, I will present the results we have obtained from LOFAR observations: we found that these sources are rare, three clusters ($\sim27\%$) present both a bright central mini halo and a fainter diffuse emission extending beyond the cluster core.
We characterized the spectrum of these sources using follow-up observations, founding the emission outside the cluster core is ultra-steep, and we made a comparison between radio and X-ray emission.

Speaker: Nadia Biava (Istituto Nazionale di Astrofisica (INAF))

Biava_SKA.pdf

33 Cluster Palaeontology in Abell 3266: Fossils, Relics, and Remnants revealed by EMU and the ATCA

Clusters of galaxies provide ideal physical laboratories for studying a wide range of physical processes associated with hot gas (thermal components) and magnetic fields (non-thermal components). However, studying cluster magnetic fields in detail is difficult, due to the wide variety of physical processes undergone by clusters during their lifetime. Diffuse radio sources (such as the canonical relics and haloes) and tailed radio galaxies (which are frequently found in clusters) can provide key signposts to these physical processes, and thus help us understand the magnetic field topography. Abell 3266 is a rich, Southern cluster undergoing a particularly complex merger event, and as such provides a golden opportunity to study the thermal and non-thermal properties of the intracluster medium (ICM) on a broad variety of scales. In this talk, I will present the results of new, deep radio observations performed with the Australia Telescope Compact Array (ATCA) and Australian Square Kilometre Array Pathfinder (ASKAP). These observations reveal a plethora of previously-unseen diffuse, steep-spectrum radio sources associated with the ICM; additionally, we detect a multitude of active and remnant radio galaxies that are now resolved in unprecedented detail. Using our exquisite new radio data in conjunction with X-ray observations from XMM-Newton and eROSITA, I will discuss the properties of these newly-discovered sources, and what we can learn from them -- both about their nature and the dynamical history of Abell 3266 -- as well as what this means for upcoming cluster surveys with ASKAP.

Speaker: Christopher Riseley (Universita di Bologna)

Riseley.pdf

34 Insight into intracluster magnetic fields by wideband polarimetry of radio relics

Merging galaxy clusters host diffuse megaparsec-scale radio emission in the form of radio relics. These synchrotron sources are usually found at the cluster outskirts and originate from cosmic-ray electrons which are (re-)accelerated by merger-driven shocks in the intracluster medium (ICM). These merger-induced shocks are believed to ''order” magnetic fields, causing the synchrotron emission to be highly polarized. However, the actual strength and topology of these magnetic fields is still poorly understood. The new generation of radio telescopes permits wide band polarimetric observations with unprecedented sensitivity and spatial resolution. This allows us for the first time to investigate the finest details of the magnetic field distribution in these sources. Here, I present a detailed analysis of wideband polarimetric data of the spectacular radio relic in the complex galaxy cluster MACS J0717.5+3745. We find that Rotation Measure and depolarization vary strongly across the relic, consistent with an intervening magnetized screen that arises from the dense ICM. I will discuss the consequences of the resulting Rotation Measure distribution and the depolarization for the ICM magnetic fields. The advent of SKA will boost this kind of studies over wide frequency ranges and will provide crucial insights into the ICM magnetic field properties, leading ultimately to a comprehensive and unified picture of the magnetic field structure and underlying particle acceleration mechanisms in galaxy clusters.

Speaker: Dr Kamlesh Rajpurohit

Rajpurohit.pdf

35 The Coma cluster at LOFAR frequencies

In this talk, I will present new results from LOFAR observations of the Coma cluster. Low frequency and high sensitivity data allow us to map the emission in detail, discover new emission associated to the large-scale structure around the cluster, and constrain particle acceleration mechanisms in the halo, birdge, and relic.

Speaker: Annalisa Bonafede (Bologna University & INAF)

Bonafede.pdf

36 New LOFAR detection in the galaxy cluster A1413: connection between non-thermal and thermal emission

Clusters of galaxies are the largest virialized systems in the Universe and thus are ideal laboratories to study the formation and evolution of cosmic structures. The baryonic matter of clusters consists of stars and galaxies, and of the intracluster medium (ICM). At the same time, radio observations have proved that the ICM is mixed with a non-thermal component, i.e. highly relativistic particles and large-scale magnetic fields, detected through their synchrotron emission.
Studying the connection between the cluster dynamical state and the properties of the diffuse radio emission is one of the main approaches to understand the origin of relativistic particles in galaxy clusters. In the last years, with the advent of new generation low-frequency radio telescopes, the classical dichotomy that connects merging events with giant halos and relaxed cool-core systems with mini-halos, has started to be questioned.
The galaxy cluster Abell 1413 is a very interesting example, of a peculiar galaxy cluster hosting a non-common radio emission. It was studied with two main goals: (i) to characterize separately the thermal and non-thermal properties of the cluster; (ii) to understand the origin of the radio-emitting electrons through a combined radio and X-ray analysis.
By performing a dedicated 2D spectral analysis of archived XMM-Newton observations, we examine the dynamical state of the cluster. The general properties derived for A1413 suggest that this system is a weak cool core cluster, i.e., not a completely relaxed system. determine the type and the properties of the extended radio emission hosted by the cluster.
The radio data allows to discover a new radio diffuse emission,more extended than previously know and constisting in a superposition of two different sources: the more compact mini-halo emission, at the cluster centre; surrounded by a low-brightness giant-halo on larger scales.
Finally, we carried out a point-to-point correlation between the physical quantities of the thermal emission and the radio surface brightness of A1413 to shed light on the connection between the re-acceleration processes, which give rise to radio emission, and the cluster dynamical state.

Speaker: Giulia Lusetti (University of Bologna)

Lusetti.pdf

Our Galaxy & Cradle of Life: chair A. Ingallinera

37 The Impact of SKA on Galactic Science: a glimpse at the Galactic plane with SKA precursors.

About 50-70% of the first five years of SKA operations will be devoted to KSPs, and probably also to Generic Surveys that maximize commensality to a wide range of scientific objectives. There are already several proposed KSPs focused on Galactic Science and we foresee many other KSP concepts being submitted under the breadth of Our Galaxy SWG.
SKA, providing better sensitivity and angular resolution than any of ongoing/planned surveys of the Galactic plane, will give the opportunity to create a sensitive wide-field atlas of Galactic radio emission and to address several topics in the field of Galactic radioastronomy.
The Galactic plane has always been a formidable challenge for radio interferometers. A concentration of extended sources and the Galactic diffuse emission makes it difficult to obtain a radio map devoid of imaging artefacts. This hampers the imaging performance of the instrument, reducing the quality of the final images (in terms of signal-to-noise ratio) and makes data reduction and analysis a particularly demanding task.

In this paper, we summarize our ongoing work aimed at achieving skills and expertise in the run-up to the development of the full SKA to be ready and competitive for leading and participating in a SKA KSP dedicated to a survey of the Galactic plane and for full exploitation of the survey data.

Our scientific goal is to use state of art radio surveys of the Galactic plane, complemented by targeted observations, to understand the cycle of matter between components of our Galaxy, from star formation in the densest regions of the ISM to the replenishment of the ISM with matter and energy released in the last phases of stellar evolution.

We are currently using radio data from the SCORPIO project (a pathfinder to the EMU an approved ASKAP legacy survey) and from the SARAO MeerKAT Galactic plane survey (SMGPS), from the MWA public survey and from a series of targeted observational projects, carried out with current radio facilities, aimed at testing their feasibility and placing the results in the context of the foreseen capabilities of the SKA.

Major results have been already obtained from the observations of the SCORPIO field conducted in the ASKAP early-science. The comparison with the same areas of the Galactic plane, previously observed with other radio facilities, demonstrates the ASKAP capability of mapping complex sources, at different angular scales, with a trade-off between sensitivity to extended emission and the ability to reveal the finest details.
The SCORPIO project has been designed to forecast the scientific impact of SKA precursors on our view of the Milky Way. At the same time, SCORPIO has been considered as a test-bed to identify, and overcome, technical issues arising from the complex structure of the Galactic plane.
The SCORPIO project has accomplished both its scientific and technical tasks.

Speaker: Francesco Cavallaro (Istituto Nazionale di Astrofisica (INAF))

Cavallaro_SKA_2021.pdf

38 BEYOND ALMA: SKA UNVEILING THE GAS COMPOSITION OF THE MIDPLANE OF PROTOSTELLAR DISKS ON A SOLAR SYSTEM SCALE

The ingredients for the recipe to make a “habitable” planet like our own Earth are: a relatively small rocky planet at the right distance from the host star for water to be in the liquid state, and with a not-too-thick atmosphere organic-rich in volatiles and capable of developing organic molecules chemistry. Searches for exoplanets have shown a large degree of diversity in the planetary systems, and as yet it is unclear how common a System like our own is. Understanding the formation of planetary systems and the chemical processing of the volatiles that will form their atmospheres is key to understanding the origins of the Solar System. More specifically, key questions still to be addressed are: how chemically organic complex are the volatiles delivered to the pristine planetary atmospheres? What molecules are passed from the large-scale envelope to the disk in which planets, comets, and asteroids form? Where do organic complex species form? These are also key questions in the context of the SKA WG Cradle of Life.

Class 0 (10^4-10^5 yr) protostars are becoming more important in the study of planet formation because evidence is mounting that the chemical composition of the final planetary system objects is highly influenced by the chemical composition during the earliest phases. An example is provided by the Solar System comets, whose ices have a chemical composition similar to that found in the inner (< 100 au), hot (> 100 K) region around the protostar. In addition, ALMA observations of gaps/rings in disks around <1 Myr protostars provide direct clues of planet formation at an earlier stage than previously thought. However, ALMA is unable to survey the chemistry of the protostellar disk midplane where planets will eventually form, because the line emission is absorbed by the optically thick continuum at (sub)mm-wavelengths. An instructive example is provided by the protostellar disk around HH212-mm as observed by ALMA down to 10 au scales: the continuum shows a dark equatorial lane due to high dust opacity, plus an interstellar complex organic molecules (iCOMs) gas. These molecules are associated with the rotating disk on a Solar System scale, but they are tracing only the outer upper and lower surface disk layers. Either (i) the iCOMs gas abundance dramatically decreases in the equatorial disk, or (ii) the iCOMs detection is hampered by the high-opacity continuum. This is a limit of the ALMA datasets that further sub-mm observations will never overcome. Only high spatial resolution (< 10 au) observations at much lower frequencies, at cm wavelengths, where the dust continuum is more likely to be optically thin, will be able to provide the answer. We will discuss how the HH212 case is driving the SKA Band 6 science goals to observe at unprecedented sensitivity the midplanes of protostellar disks, and consequently to derive their chemical content.

Speaker: Claudio Codella (Istituto Nazionale di Astrofisica (INAF))

Codella_SKA_Oct21.pdf

39 Unveiling hot corinos nature at cm wavelengths: A new era with SKA

Hot corinos, central planet-forming regions of Solar-like protostars enriched in interstellar Complex Organic Molecules (iCOMs), are the likely analogues of the early Solar System.
Deceivingly, after almost 20 years of hunting, only less than twenty hot corinos are known. Surprisingly, many of them are binaries with the two components showing different millimeter molecular spectra. There are two possible explanations for why hot corinos are so difficult to find and why the millimeter spectra of coeval objects are so different: 1) the dust is so optically thick that hides the molecular lines; 2) the different observed spectra reflect an intrinsic chemical diversity probably due to the different composition of the grain mantles, formed in the prestellar phase.

In order to test and verify these two possibilities, centimeter observations are the key as i) we can observe iCOMs at wavelengths where the dust opacity is negligible; ii) we can simultaneously observe two major grain mantle components, methanol (CH$_3$OH, also the simplest iCOMs) and ammonia (NH$_3$). With pilot projects performed using JVLA observations of CH$_3$OH and NH$_3$ toward a sample of objects in Perseus, we could demonstrate that indeed dust hides the hot corino with the largest dust content, that abundances derived at sub-mm regimes can be severely underestimated, and that ices can be different. These studies, that I will present in this contribution, pave the way to the Square Kilometre Array (SKA) observatory that is the perfect and only facility capable to overcome the current limits, thanks to its high sensitivity and high angular resolution, as it will allow to observe more complex iCOMs with abundances lower than the CH$_3$OH one (of at least few order of magnitude) at small angular scales ($<$10 au) fully sampling the planet-forming hot corino region.

Speaker: Marta De Simone (Univ. Grenoble Alpes - IPAG - INAF Arcetri)

SKA_2021_Ita_MDeSimone.pdf

40 The chemistry of planet-forming disks with SKA: the inner 50 au

In the last six years ALMA revolutionised our comprehension of planet formation. The first breakthrough was delivered by the impactful images of rings and gaps in the dust distribution of young disks, the first direct probe of planet formation at work in disks of age less than 1 Myr. In parallel, ALMA is revolutionising also our comprehension of the disk chemistry, delivering the first inventory of molecules in disks. This is crucial to answer another key question about planet formation: what chemical composition do planets inherit from their natal environment? To answer this question is one of the goal of the SKA WG “Cradle of Life”.

To characterise the molecular content of planet-forming disks, we recently started the ALMA-DOT chemical survey of young disks in the nearby star-forming region of Taurus (140 pc). ALMA-DOT allowed us to reveal the radial and vertical distribution of several molecules at 15-50 au scales (CO, CN, CS, H2CO, H2CS, SO, SO2) and to detect methanol (CH3OH), the simplest complex organic molecule (COM) and a key brick for the formation of pre-biotic molecules. The ALMA-DOT observations also highlighted the limits of ALMA for the study of the disk chemistry: (1) ALMA is blind to molecular emission in the inner 50 au of young disks, because this is suppressed by optically thick dust emission; (2) COMs are hard to detect in disks.
To overcome these limits and detect COMs on a <50 au scale (i.e. the Solar-System scale) we crucially need to observe at cm wavelengths, where the continuum is optically thin, and a unique combination of very high sensitivity and angular resolution. This can be obtained only with deep SKA observations in band 6. A pilot project to map the H2CO snowline in disks with JVLA is ongoing to test the project feasibility and set the sensitivity requirements for SKA observations. These observations will be key to characterise the molecular content of the inner 50 au of planet-forming disks, and to infer the location of molecular snowlines. These in turn are key to understand chemical processes in disks, planet formation, and chemical inheritance of the planets atmospheres.

Speaker: Linda Podio (Istituto Nazionale di Astrofisica (INAF))

LPodio_3rdSKA-IT_Oct2021.pdf

15:50 Break

Our Galaxy & Cradle of Life: chair C. Trigilio

41 SKA to explore the chemical content of forming Sun-like protostars: the missing evidence of large carbon chains

The formation of a solar type planetary system is characterized by several physical processes that start with the collapse of a cold (≤ 10 K) and dense (≥ 10$^5$cm$^{-3}$) prestellar core into a protostar, a protoplanetary disk and, eventually, a planetary system. These stages are also accompanied by the evolution of the chemical composition (e.g. Caselli & Ceccarelli 2012), which is a powerful diagnostic tool to recover the past and present conditions of a source.

The vast majority of the observations that led the recognition the chemical variety of solar type protostars has been obtained via millimeter wavelengths telescopes, where several relatively light molecules, like the iCOMs or the small carbon chains have their peak of emission. In contrast, the lines of heavy molecules (e.g. chains with more than seven C-atoms) at mm wavelengths are substantially weaker. Their observation could add an important piece of the overall puzzle as they might have a crucial role in the heritage of organic material from the pre- and proto- stellar phase to the objects of the newly formed planetary system, like asteroids and comets (e.g. Mumma & Charnley 2011, McGuire et al. 2019).

We will report the results obtained in a pilot study proposed using GBT to observe several crucial C-bearing chains in the 8.0 – 11.5 GHz and 14.0 – 15.4 GHz intervals, in L1544 and IRAS16293-2422, which are the two archetypes of prestellar cores and protostars, respectively. GBT observations, covering part of the frequency range of the future SKA1-MID, reveal an impressive molecular richness of C-chains (e.g. C$_4$H, C$_6$H, HC$_7$N, HC$_9$N, C$_3$S) and a chemical differentiation between the two sources at large angular scales. These preliminary results stress the importance of SKA observations to image the spatial distribution of the observed C-chains and to understand if large carbon chains and iCOMs coexist in the planets formation region.

Speaker: Eleonora Bianchi (Univ. Grenoble Alpes, CNRS, IPAG / INAF - Osservatorio Astrofisico di Arcetri)

SKA-IT2021-Bianchi.pdf

42 ANOMALOUS MICROWAVE EMISSION AS SEEN BY SKA

The emission budget from astrophysical sources at microwave frequencies is mostly dominated by the well-studied and well-understood free-free, synchrotron, and thermal dust emission. Nevertheless, observations mainly carried out in our Galaxy have revealed an unexpected excess of emission (Anomalous Microwave Emission, AME) in the microwave band that cannot be explained by standard emission mechanisms or in terms of the cosmic microwave background (CMB). Its physical origin is not fully understood yet, but the most convincing models predict that AME is dominated by electric dipole emission from rapidly rotating small dust grains, spinning dust, although current observations remain inconclusive.

With the extension of SKA1-MID beyond 15GHz, at frequencies where AME appears to increase with frequency and peak, we have a unique possibility to shed light on AME mechanisms using high angular resolution, polarization and spectroscopic informations which cannot be reached otherwise. Also, while waiting for the approval of band 6, and given the angular resolution achievable by SKA, a striking scientific goal would be the observation of AME in redshifted sources up to z=1 or 2. This would be observable with MID Band 5a (4.6 - 8.5 GHz) or 5b (8.3 - 15.3 GHz). It should be stressed, in fact, that Inter Stellar Medium structures emit over a wide range of scales allowing SKA1-MID observations to focus, with its high angular resolution, on regions with signifcant dust column densities. This will be possible taking advantage of the exibility in terms of u-v coverage (including both short and long baselines) of SKA. Among possible targets that would fit the extended band 6 SKA1-MID in terms of frequency and baseline coverage, we list: molecular clouds, photodissociation regions, dense pre-stellar cores, proto-planetary circumstellar disks, as well as external galaxies.

Progress in this field requires new observations of large heterogeneous samples of AME detections covering ~1-30 GHz, where AME spectrum rises. To this end, we foresee synergies with existing facilities monitoring different angular scales with different resolutions such as the SRT already used for AME science and that could represent the pathfinder for possible extended SKA1-MID follow-up observations.

Speaker: Elia Stefano Battistelli (Sapienza, University of Rome)

SKA4AME.pdf

Nearby Universe: chair C. Trigilio

43 SKA continuum observations to study star formation in nearby galaxies

One of the challenges in star formation studies is to link the intra-cloud understanding of the processes, obtained in the Milky Way, to the picture of kpc-scale relations usually studied in external galaxies.
Nearby galaxies are the ideal laboratory for this investigation since they allow the study of star formation processes on large-scale, while still being close enough to reveal the local details, if high resolution and sensitivity are achieved.
Images of the molecular emission at tenths of pc scales from nearby galaxies are now routinely produced thanks to ALMA's unprecedented capabilities. The SKA, with its high sensitivity and sub-arcsec resolution, will be as well a transformational instrument in the study of star formation and accretion activity in nearby galaxies, through radio continuum observations.
SKA will allow to decompose nearby galaxies in their compact radio source population, including accretion dominated AGN as well as tracers of early stages of star formation, like HII regions, super star clusters, supernova remnants. The comparison of their radio continuum emission, both thermal and non-thermal, with the molecular counterpart will give useful information on the role of the different interstellar medium components in the star formation processes.

Speaker: Rosita Paladino (Istituto Nazionale di Astrofisica (INAF))

ska_2021_paladino.pdf

44 DustPedia & MeerKAT: Focus on the HI gas in the star formation process

The interstellar medium (ISM) is of vital importance for the lifecycle of galaxies thanks to its ability to condense and form stars, and to be regenerated by stellar evolution. Only a large and coherent dataset of all components of the ISM (dust, atomic and molecular gas, metals) can provide a definitive view of the ISM in galaxies. Thanks to a sample of ~400 DustPedia late-type galaxies, we found -for the first time- that the total dust mass correlates better with HI mass than with the molecular one (derived from CO). The strong dust-HI correlation is opposite to what is typically observed at small scales in the ISM, where dust and molecular gas are strongly associated in the star formation (SF) process, while the HI gas is not directly involved with it.

We will present the results of an ongoing analysis dedicated to the complete high-resolution (sub-kpc/kpc scales) characterization of the ISM in a sample of 18 nearby spiral DustPedia galaxies covering heterogeneous peculiarities (e.g., bars, AGN, interactions). In particular, we will focus on the galaxy NGC 1365 showing its MeerKAT HI map and comparing it with the CO (ALMA) and dust (DustPedia) ones. Stellar mass and star formation rate maps and metallicity information are also available thanks to the DustPedia database. While at global scales the primary role of the atomic gas is well-defined, high-resolution HI maps are allowing us to re-define it at intrinsic scales of the SF process, where the atomic gas may not be so marginal as was believed until now.

Exploring the cosmic evolution of the gas content of galaxies is a key science driver for SKA. The synergy between DustPedia and MeerKAT is supporting this providing a first important step in understanding how the cold ISM is related to the dust content, and to galaxy capability to form stars.

Speaker: Viviana Casasola (Istituto Nazionale di Astrofisica (INAF))

Casasola.pdf

45 Comparing APERTIF HI statistics with baryonic scaling relations in the Local Universe

We present estimates of the atomic gas mass MHI in galaxies within the APERTIF SNS survey region. To do this, we have relied on empirical gas scaling relations based on stellar mass and star-formation rate established in the Local Universe. From the inferred HI masses, we derive HI mass functions (HIMFs), and find reasonable agreement with HIMFs derived observationally. The comparison with APERTIF HI content shows that HI-selected samples and optically- or mass-selected samples behave differently. The details of these differences will help constrain future predictions and inform models of galaxy evolution.

Speaker: Leslie Kipp Hunt (Istituto Nazionale di Astrofisica (INAF))

lhunt_SKAItaly2021.pdf

Thursday 7 October

Nearby Universe: chair I. Prandoni

46 LeMMINGS: the eMERLIN radio legacy survey of nearby galaxies

I will present the high-resolution 1.5-GHz radio observations of 280
nearby galaxies with the eMERLIN array, part of the LeMMINGs survey.
The sample consists of active and non-active galaxies, taken from
the Palomar sample. The radio images reveal a broad variety of
morphologies: one/two-sided jets, double-lobed jets, complex
structures and star formation regions on a typical scale of ~100 pc,
down to a radio luminosity of ~10^19 W/Hz. The most important result
is the detection of pc-scale jetted structures associated with black
hole masses down to 10^6 solar mass. By dividing the sample into
optical classes, LINERs show more core-brightened radio morphologies
and appear to be the scaled-down version of FRI radio galaxies;
Seyferts show less collimated jets than LINERs; HII galaxies and
Absorption-line galaxies are a mixed populationof weakly active and
silent black holes. In addition, by including new Chandra X-ray
data, I will explore their disc-jet connection and the origin of
their nuclear emission in low-luminosity AGN and inactive galaxies.

Speaker: Ranieri Diego Baldi (Istituto Nazionale di Astrofisica (INAF))

Baldi_Lemmings-SKAit.pdf

47 The cold gas component and jet-ISM interplay in nearby low-excitation radio galaxies

Low excitation radio galaxies (LERGs) are a class of AGN accreting gas at low rates (<< 1% of the Eddington limit) and producing almost entirely kinetic (i.e. jet-induced) feedback. LERGs are, by number, the dominant radio galaxy population in the local Universe, preferentially hosted by massive nearby early-type galaxies (ETGs). Despite their prevalence, the powering mechanisms of these objects and associated AGN feedback processes are still poorly understood. We are carrying out for the first time a spatially-resolved, multi-phase (stars, hot/warm/cold gas, dust and radio jets) study of a volume- and flux-limited sample of eleven LERGs in the southern sky. The results obtained so far adds to the developing picture of LERGs as unexpectedly complex systems. The analysis of ALMA CO(2-1) data of nine sample sources demonstrates that the majority of them contain surprisingly large masses of molecular gas in the form of rotating discs confined on (sub-)kpc scales. The bulk of this gas appears to be in ordered rotation and stable orbits, possibly explaining the relatively low accretion rates of these objects. Nevertheless, subtle kinematic perturbations are ubiquitous and can be attributed either to interactions with the jets or to settling effects. The comparison between matched-resolution JVLA 10 GHz continuum and the ALMA CO data allows us to perform a full 3D study of the relative orientations of jet and disc rotation axes in four sample objects. Results from this analysis indicate that there is no simple relation between the rotation axis of the gas and the axis of the radio jets and provide further evidence for a jet-cold gas interaction in two sample sources. Follow-up ALMA observations of multiple molecular gas tracers in one of these two object, NGC 3100, demonstrate jet-induced modifications in the physics (i.e. optically thin conditions and high-excitation temperatures) and kinematics (i.e. low-velocity gas outflow) of the molecular gas on sub-kpc scales. Recently-acquired ATCA HI observations, along with other multi-wavelength indicators, hint to an external cold gas origin in sample sources with nearby companions, supporting an environment-dependent scenario for the cold gas accretion mechanisms in LERGs. Overall, the results obtained so far provide important constraints on the details of jet–cold gas interactions, fuelling and feedback processes in these systems. The high resolution and sensitivity provided by SKA will be crucial to simultaneously look at the HI and radio continuum components of our sample sources with unprecedented details and get further insights on these issues.

Speaker: Ilaria Ruffa (Istituto Nazionale di Astrofisica (INAF))

IRuffa_SKA_Italy_talk.pdf

48 Cold gas in nearby radio galaxies

The SKA precursors and pathfinders (e.g. MeerKAT, ASKAP) opened a new era of investigation of neutral atomic (HI) gas studies in nearby galaxies. The possibility of reaching high spatial ($\sim 10-30$’’) and spectral resolution ($\sim ~4 - 20$ km s$^{-1}$) with short ($\sim 10$ hrs) observations, combined with a large field of view ($\sim 1^\circ$), now enables us to investigate the presence of low-column density ($<5\times 10^{19}$ cm$^{-2}$) HI in all types of galaxies in different environments, from isolated objects to groups and clusters. For example, observing low-column density HI from the macro (hundreds of kpc) to the micro scale (a few kpc) in active galactic nuclei (AGNs) allows us to trace not only signatures of AGN-feedback (i.e. gaseous outflows) but also phenomena of cold gas accretion.

In this talk, I will show how using both neutral hydrogen and high spatial resolution observation of the radio continuum emission of AGNs we can connect the presence of HI with the history of the nuclear activity occurred in the galaxy. I will present the results from different recent deep HI observations ($<5\times 10^{19}$ cm$^{-2}$) from the Australia Telescope Compact Array and MeerKAT projects (i.e. Meerkat Fornax Survey, Mhongoose, open-time) of a handful of nearby AGNs ($D_{\rm L}<50$ Mpc) representative of different radio powers and optical luminosities. I will focus on the role of the neutral hydrogen in the accretion and feeding of the nuclear activity. These results demonstrate how HI observations allow us to distinguish between 'external' accreting phenomena (i.e. mergers and interactions) and 'internal' phenomena (i.e. cold chaotic accretion, secular events). I will highlight the crucial synergy with high resolution molecular and ionised gas observations to understand what mechanisms regulate the life-cycle of radio AGNs.

Speaker: Filippo Maccagni (Istituto Nazionale di Astrofisica (INAF))

Maccagni-SKA-Italy-2021.pdf

49 Galaxy dynamics in the era of large HI surveys

The HI emission line at 21 cm is arguably the best tool to trace the internal dynamics of galaxies and was indeed pivotal to establish the dark matter problem. The HI emission typically traces rotating gas disks that extend further out than the stellar component of galaxies, so one can measure extended rotation curves out to large radii, where the dark matter effect becomes predominant. Current HI samples of galaxies, however, are limited to a few hundreds objects at low redshift and are rather heterogeneous in nature (e.g., the SPARC database; Lelli et al. 2016, AJ), limiting our ability of testing galaxy formation models in a LCDM context as well as alternative theories. The SKA observatory and its pathfinders will revoluzionaze the study of galaxy dynamics, providing spatially resolved HI data for several thousands of galaxies, possibly up to high redshifts. Given the unprecedented amount of data, it will be crucial to have fast, automated, and reliable tools to model galaxy dynamics in an efficient way. In preparation to wide-field next-generation HI surveys, we started a major data-modeling project called BHINGO (Barolo HI Nearby Galaxy Overview). We collected about 1000 HI datacubes from several public archives and analized them in a homogeneous fashion using the 3D-Barolo software (Di Teodoro & Fraternali 2015). For all these galaxies, BHINGO provides HI moment maps as well as ready-to-use advanced data products, such as gas surface density profiles and rotation curves. BHINGO will increase the size of existing HI samples by a factor of about five: this is a necessary intermediate step to get ready to the order-of-magnitude increase in sample sizes expected from SKA precursors. I will also discuss how the same data-modeling techniques are currently being applied to pilot HI data from the ASKAP telescope as part of the kinematic pipeline of the WALLABY survey.

Speaker: Federico Lelli (Istituto Nazionale di Astrofisica (INAF))

Lelli_SKA-Italy.pdf

10:50 Break

Nearby Universe & Galaxy Evolution: chair P. Serra

50 The MeerKAT Fornax Survey: Rapid HI removal in dwarf galaxies

I will present some of the first results from the MeerKAT Fornax Survey (MFS), that show that dwarf galaxies rapidly lose their cool gas once they have entered into the cluster. The MFS is now 25% complete, and thanks to the exquisite sensitivity and resolution of the MeerKAT telescope, we are exploring a new observational parameter space and have detected HI in a population of dwarf (Mr > -18.5) galaxies down to a HI mass of 10^6 Msol. Only 14 out of 300 dwarfs in the current mosaic are detected in HI, showing that the majority of dwarfs in the Fornax cluster have already lost their HI. For the dwarfs with HI, a dichotomy exists - either the dwarf has a regular amount of HI or the dwarf is extremely HI poor given its luminosity. As we do not detect dwarf galaxies in between (i.e. transitioning from HI-normal to HI-poor) these two HI mass-to-luminosity ratios, this suggests that a dwarf galaxy with HI will very rapidly lose it’s HI, even before the first pericentric passage. We also find that the majority of dwarfs with HI are at least 80 kpc away from the closest, massive galaxy. This may be evidence that pre-processing assists in the removal of HI from dwarf satellites, accelerating the loss of HI while infalling to and within the cluster.

Speaker: Dane Kleiner (Istituto Nazionale di Astrofisica (INAF))

Dane_Kleiner_SKA_Italy.pdf

51 ISM stripping or starvation? The formation of an S0 galaxy in the Fornax cluster

The MeerKAT Survey of the Fornax galaxy cluster, which is 25% complete, revealed the presence of a HI-rich S0 galaxy in the center (∼0.4 Rvir) of Fornax: NGC 1436. This finding provides us with a good opportunity to test the current hypotheses of starvation and ISM stripping often invoked to account for the formation of S0 galaxies in clusters.
Our MeerKAT data (N(HI )∼10^18 cm−2) show a truncated HI disc confined within the stellar body of NGC 1436. Star formation is still on-going within the truncated HI disc, as shown by optical, radio continuum and molecular gas images.
Using MUSE data, we are estimating the star formation history in the inner and outer part of NGC 1436 to understand the cause of the HI disc truncation and evaluate how rapidly the galaxy has used/lost its cold gas reservoir. Our ultimate goal is to determine whether starvation or ISM stripping is the main process which has shaped the HI content of NGC 1436.

Speaker: Alessandro Loni (Istituto Nazionale di Astrofisica (INAF))

Loni_SKA_it.pdf

52 Finding Jellyfish Galaxies with MeerKAT

Deep galaxy surveys have shown that the star formation rate (SFR) decreases with redshift.
The cause of the decline in star formation activity is not yet completely understood. However, it can be studied by investigating how the acquisition and removal of the star-forming gas affect galaxies.
The GAs Stripping Phenomena (GASP) survey is conducting this investigation by selecting galaxies that show signs of gas removal due to ram-pressure stripping by their host galaxy clusters. The so-called jellyfish galaxies represent an extreme example of rapid galaxy transformation due to their environment.
The work presented here will focus on the neutral gas (HI) phase in the prototypical jellyfish galaxies within various clusters observed as part of the MeerKAT Galaxy Cluster Legacy Survey. In this presentation, we discuss HI content in these galaxies to determine the onset of gas stripping in different cluster environments.

Speaker: Dr Mpati Ramatsoku (Rhodes University and INAF-OAC)

M_Ramatsoku_SKA_Italy_2021.pdf

53 GAEA: a cosmological model for the HI content of galaxies and halos.

I will present results based on our GAlaxy Evolution and Assembly (GAEA) state-of-the-art semi-analytic model. GAEA follows the star formation, metallicity and black hole accretion history of galaxies in cosmological volumes, and includes an explicit partition of the cold gas content of galaxies in its molecular and atomic components. I will focus, in particular, on our studies of the HI content of galaxies and dark matter halos as a function of cosmic epochs and galaxy environments. I will also illustrate our ongoing activities aimed at creating dedicated mock catalogs that contain both physical properties of galaxies and information on the background dark matter structure, as well as a modelling of the HI line profile.

Speaker: Gabriella De Lucia (Istituto Nazionale di Astrofisica (INAF))

skaIII_delucia.pdf

54 Unveiling HI galaxy scaling relations at z~0.4 with spectral stacking applied to MeerKAT datacubes

Neutral hydrogen (HI) is a key ingredient in the baryonic picture of our Universe and understanding its abundance, redshift evolution, phenomenology and role in astrophysical and cosmological processes on different scales is currently the subject of an intense observational and theoretical effort by the community. In particular, HI is regarded to play a major role in galaxy evolution, being the basic constituent of molecular hydrogen and thus of paramount importance for triggering star formation. Furthermore, its abundance and distribution are strongly sensitive to the large-scale structure of the Universe (LSS), being therefore potentially an excellent proxy for the galaxies-LSS connection. In this scenario, galaxy scaling relations involving HI have been thoroughly explored in the Local Universe (z<0.1), finding tight trends linking HI mass, stellar mass and SFR. However, they have remained largely unexplored at z>0.1 due to the intrinsic faintness of the 21cm line and the consequent difficulty in performing direct detections for a statistically complete sample of galaxies. To this end, spectral stacking have been widely resorted to as a cheap and efficient technique to increase the signal-to-noise ratio and perform a mean HI mass detection, at the expense of information on single galaxies.
In two forthcoming papers, we investigate (i) the impact of technical and instrumental aspects (e.g. source confusion, primary beam correction and weighting schemes, among others) on HI mass estimates derived through stacking of sources with realistic spatial distribution in mock datacubes mimicking real MeerKAT observations (Sinigaglia et al. 2021c, in prep.) and (ii) perform a measure of galaxy scaling relations in the HI mass-stellar mass-SFR plane at a mean redshift z~0.4, possibly addressing the potential evolution of such relations from z=0.5 to z=0 using MIGHTEE-HI MeerKAT real datacubes (Sinigaglia et al. 2021d, in prep.). In particular, in (ii) we select a sample of ~13000 galaxies in the COSMOS and XMM-LSS fields at z<0.6, with spectroscopic redshift known from literature and stellar mass and SFR estimates obtained through CIGALE SED-fitting. We argue that such studies are in position of setting new standards of data exploitation in the context of the future SKAO and its pathfinders.

Speaker: Francesco Sinigaglia (Università degli Studi di Padova)

HI_stacking_meerkat_sinigaglia.pdf

Galaxy Evolution and AGN: chair M. Giroletti

55 Clues on the evolving infrared-radio correlation towards the SKA era

Understanding what drives the observed correlation between total infrared and GHz-radio emission in galaxies ("infrared-radio correlation", IRRC) is a major quest in extra-galactic astronomy, in order to calibrate radio emission as a star formation rate (SFR) indicator. We have recently calibrated the IRRC in the COSMOS field by exploiting deep VLA and MeerKAT continuum surveys, combined with exquisite multi-wavelength ancillary data. Starting from a sample of $>$400,000 star-forming galaxies selected in stellar mass (M$_{\star}$), we investigate how the IRRC varies as a function of both M$_{\star}$ and redshift, out to z$\sim$4. We stack deep radio and infrared images in different (M$_{\star}$, z) bins, carefully removing radio-excess AGN candidates via a recursive approach. We find that more massive galaxies are radio brighter at fixed infrared luminosity than less massive counterparts, at all redshifts. I will discuss possible physical interpretations of these findings. Our study provides a leap forward in understanding the radio-SFR relation at different M$_{\star}$ and cosmic epochs, which will prove crucial in future ultra-deep SKA surveys to convert radio detections into accurate SFR measurements.

Speaker: Ivan Delvecchio (Istituto Nazionale di Astrofisica (INAF))

SKA_Ivan_Delvecchio.pdf

56 A new analysis of low-frequency radio luminosity as a star-formation tracer in the Lockman Hole region using LOFAR deep observations

In preparation for the deep and wide continuum extra-galactic surveys that will be carried out by the SKA, we have exploited LOFAR deep observations of the Lockman Hole field at 150MHz to investigate the relation between the radio luminosity of star-forming galaxies (SFGs) and their star formation rates (SFRs), as well as its dependence on stellar mass and redshift. The adopted source classification, star formation rate (SFR) and stellar mass estimates are consensus estimates based on a combination of four different SED fitting methods. We note a flattening of radio spectra of a substantial minority of such sources below ~1.4 GHz. Such sources have thus a lower “radio-loudness” level at 150MHz than expected from extrapolations from 1.4 GHz using the average spectral index. We found a weak trend towards a lower SFR/L$_{150MHz}$ ratio for higher stellar mass. We argue that such a trend may account for most of the apparent redshift evolution of the L$_{150MHz}$/SFR ratio, in line with previous work. Our data indicate a weaker evolution than found by some previous analyses. We have derived luminosity functions at 150MHz of both SFGs and radio-quiet (RQ) AGN at various redshifts. Our results are in very good agreement with the T-RECS simulations and with literature estimates. We also present explicit estimates of SFR functions of SFGs and RQ AGN at several redshifts derived from radio survey data. In the talk, a comparison with the analysis by Bonato et al. (2021) of deep WSRT observations of a fraction of the field will be presented as well.

Speaker: Matteo Bonato (Istituto Nazionale di Astrofisica (INAF))

Bonato.pdf

57 Variation of the radio spectral slopes on and off the Main Sequence: new constraints on internal galaxies physical processes

We present the results of a VLA pilot program to measure the radio slope in a sample of z=2 starforming galaxies from the COSMOS field. From the radio slope we will infer the relative fraction of thermal and non-thermal emission from young stellar populations, which can be directly related to the upper mass limit of the IMF. We probe the different galaxy evolutionary phases by selecting 20 main sequence objects (constituting our control sample) and 30 off-main sequence starbursts with specific star formation rate >4 times higher. We obtained 16 GHz VLA observations of the targets to complement existing VLA 1.4 GHz data at the same spatial resolution, providing an extended frequency range unaffected by free-free absorption to allow a robust determination of the radio slope. We show that the selected number of objects in each subsample (off and on main-sequence) is sufficient to fairly well estimate and soundly compare their median radio slopes. We interpret our findings as a potential evidence at high redshift for a non-universal high-mass end of the IMF.

Speaker: Giulia Rodighiero (University of Padova)

rodighiero_SKA2021_B.pdf

58 LOFAR Observations of the Euclid Deep Field North

I present the results obtained from the first set (about 70 hours) of LOFAR HBA observations of the Euclid Deep Field North (EDFN). EDFN is becoming the highest priority deep field for LOFAR and has been awarded further 320 hours of observations that will be carried out in the next semesters. This first set of observations has been reduced and analyzed in Italy by the LOFAR-IT collaboration
using the Occam Supercomputer.I will summarize the data reduction challenges, the data products obtained from the data analysis and I will show some preliminary results obtained from the inclusion of the international stations that allow to sharpen the angular resolution from 6 arcsec to 0.3 arcsec.

Speaker: Marco Bondi (Istituto Nazionale di Astrofisica (INAF))

3rdska-bondi.pdf

15:50 Break

Galaxy Evolution and AGN: chair T. Venturi

59 The turbulent youth of a proto-cluster at z=1.7 in the J1030 field

We are collecting deep multi-wavelength data on the field hosting the QSO J1030+0524 at z=6.3. This includes two of the deepest Chandra and JVLA (1.5 GHz) surveys to date. I will present the X-ray/radio properties of a large-scale structure at z=1.7 assembling around a powerful FRII, that dominates the center of the field. Extended X-ray emission has been detected around the FRII. Remarkably, four of the protocluster members lie in an arc-like shape around the main X-ray extended emission. We propose that such emission originates from an expanding bubble of gas shock heated by the FRII jet, that is promoting the star formation on nearby galaxies by compression of their ISM. If confirmed, this would be the first evidence of positive AGN feedback on multiple galaxies on hundreds-kpc scales. New LOFAR (150 MHz) observations reveal extended radio emission around the FRII lobes, likely linked to the diffuse X-ray structures. Exploiting the JVLA and LOFAR data we built the spectral index map, which reveals signatures of re-acceleration of the plasma in the outskirts of the lobes, possibly induced by interactions with the ICM. Finally, based on ALMA observations of the CO(2-1) transition, we recently discovered three new gas-rich galaxies belonging to the proto-cluster, in addition to a large molecular gas reservoir ($M_{H2}$~$2 \times 10^{11}$ $M_\odot$) around the FRII host galaxy. Under simple assumptions, we show that the system will evolve into a ≳ $10^{14}$ $M_\odot$ cluster at z=0 and that the FRII is the likely progenitor of the future BCG.
I will conclude presenting the X-ray/radio properties of the faint radio population in the overall field (~1300 radio sources down to $S_{1.5 ~\mathrm{GHz}}$ ~ 10 $\mu$Jy), focusing on the AGN component.

Speaker: Quirino D'Amato (Alma Mater Studiorum - Università di Bologna)

SKA_Quirino_Damato.pdf

60 Exploring the population of Radio-Loud AGNs at high redshift with the RACS survey

We present the first results of a recently started project focused on radio-loud (RL) Active Galactic Nuclei (AGNs) at high redshift which exploits the new Rapid ASKAP Continuum Survey (RACS). Thanks to its unprecedented combination of area and sensitivity, this survey is the perfect starting point to push the study of RL AGNs at the highest redshift currently explored (z>6), allowing for the discovery of statistically significant samples. Soon after the first data release of the RACS we uncovered the second most distant RL AGN currently known (z=6.44). From a first radio follow-up of the source we found that the source has a peaked radio spectrum, with the peak around 5 GHz, suggesting that we are observing a newly born jet ($\sim$100 yrs) in the early Universe. Moreover, we also present the discovery of two new very promising z>6 RL AGNs discovered as part of a systematic search for new high-z RL objects from the combination of the RACS survey with wide-area optical surveys currently available.

Speaker: Luca Ighina (Istituto Nazionale di Astrofisica (INAF))

SKA_Ita_ighina_Luca.pdf

61 The GRACE project: giant radio galaxies and their duty cycle

Giant radio galaxies (GRG) are one of the most spectacular manifestation of astrophysical jets, showing plasma ejecta with an extension up to Mpc. However, the conditions allowing such a growth are still unclear, and may be linked to a particularly favourable environment, to peculiar accretion/ejection conditions allowing a very long and continuous radio activity, or to more than one radio cycle. The aim of the GRACE project is to study the radio duty cycle in a sample of giant radio galaxies selected from high energies (hard X-rays) catalogues produced by the INTEGRAL/IBIS and Swift/BAT space missions. This sample presents a high fraction of restarted GRG, either in the form of a young radio source in their core, or from their morphology. We will present the results of an extensive campaign from the X-ray to radio band, including the latest data from the LOFAR Two-metre Sky Survey (LoTSS).

Speaker: Dr Gabriele Bruni (INAF - Istituto di Astrofisica e Planetologia Spaziali)

Bruni.pdf

62 Spectral analysis of spatially-resolved 3C295(sub-arcsecond resolution) with theInternational LOFAR Telescope

3C295 is a bright, compact steep spectrum source with a well-studied integrated radio spectral energy distribution (SED) from 132 MHz to 15 GHz.
However, spatially resolved spectral studies have been limited due to a lack of high resolution images at low radio frequencies.
These frequencies are crucial for measuring absorption processes, and anchoring the overall spectral modelling of the radio SED. In this paper, we use International LOFAR (LOw-Frequency ARray) Telescope (ILT) observations of 3C295 to study its spatially resolved spectral properties with sub-arcsecond resolution at 132 MHz.

Combining our new 132 MHz observation with archival data at 1.6 GHz, 4.8 GHz, and 15 GHz, we are able to carry out a resolved radio spectral analysis. The spectral properties of the hotspots provides evidence for low frequency flattening. In contrast, the spectral shape across the lobes is consistent with a JP spectral ageing model.
Using the integrated spectral information for each component, we then fit low-frequency absorption models to the hotspots, finding that both free-free absorption and synchrotron self-absorption models provide a better fit to the data than a standard power law.
Although we can say there is low-frequency absorption present in the hotspots of 3C295, future observations with the Low Band Antenna of the ILT at 55 MHz may allow us to distinguish the type of absorption.

Speaker: Etienne Bonnassieux (Istituto Nazionale di Astrofisica (INAF))

Bonnassieux - Resolved Spectral Analysis of 3C925 with the ILT.pdf

63 Numerical models of synchrotron emission from AGN jets: the role of the host environment.

Synchrotron emission (SE) is one of the most important diagnostic tools of the physical state of AGNs relativistic jets, mostly because of its ubiquitous presence. However, modelling SE from jets is not free of ambiguities: different models often can provide equally good spectral fits in the observed ranges. In this work we start from a series of high-resolution AMR numerical models of radiolobes, varying the inclination of successive jet generations according to different prescriptions (from always straight, to limited within a cone, to completely random), to derive synchrotron spectra and images at different radio frequencies and study how the disentanglement of different features depends on the distance (redshift) and intrinsic evolution of the sources themselves. We restrict ourselves to blazar-like sources (l.o.s. of the jets within 6 degrees), and focus on the role of the host ICM/IGM thermodynamic state in shaping the properties of the observed SE. We demonstrate that on average jets propagating in an equilibrium medium (e.g. 1-st generation jets) have distinct observational signatures from 2-nd and 3rd generation jets, and similar differences are noticed in the relationship between SE and gamma-ray emission.

Speaker: Vincenzo Antonuccio (Istituto Nazionale di Astrofisica (INAF))

BL-Lac-simulations.pdf

Friday 8 October

SKA Data Center - related activities: chair F. Govoni

64 Innovative data processing solutions in the perspective of the SKA Regional Centres.

The SKA Regional Centres (SRC) are expected to provide essential functions like computational capacity for data reprocessing and science analysis, provision of a SKA Science Archive and local user support. The SRC Steering Commettee (SRCSC) is currently operating to define and create a long term operational partnership between the SKA Observatory and an ensemble of independently resourced SRC. The SRCSC is carrying out its work through subgroups to focus on specific areas.

We will report on the activity of one of these working groups (WG6), that has the identification of use cases to run on proto-SRCs as one of the main objectives. The use cases have to challenge the current available infrastructures identifying the requirements to effectively handle the SKA data in terms of computing, network, archiving and software. In particular, software has to be improved in order to i) exploit high performance computing solutions to cope with large data ii) exploit innovative numerical solutions to increase accuracy and, at the same time, minimize human supervision, impossible for such huge data volumes. Machine learning solutions are currently among the most promising from both points of view. Their potential for radio astronomy data are currently under investigation adopting LOFAR and ASKAP prototype data products. An overview of our achievements will be presented.

Speaker: Claudio Gheller (Istituto Nazionale di Astrofisica (INAF))

SKASRC-It-Gheller.pdf

65 Visualization and source analysis services for the SKA Regional Centers

New developments in data analysis and visualization are nowadays critical to deal with the increased size and complexity of SKA and precursor data. Such efforts should be oriented to enable extraction of science information from the data in a mostly automated way, possibly exploiting the capabilities offered by modern computing infrastructures. In this context, looking at the experiences gained with the ASKAP and MeerKAT Galactic plane data, we realized that the integration of source analysis algorithms into data visualization tools could significantly improve and speed up the cataloguing process of large area surveys, boosting astronomer productivity and shortening publication times.
With this motivation, also following the design activities ongoing within the SKA Regional Center WGs, we are carrying out different SKA-related projects (such as CIRASA and NEANIAS) at INAF-OACT, in collaboration with other INAF institutes and external partners, to develop and integrate a set of cloud services for source analysis (e.g. extraction, classification), archive data retrieval, and data visualization into a common visual analytic platform. Services are being tested on a prototype European Open Science Cloud (EOSC) infrastructure, provided by GARR and also backed by INAF resources. Details on the activities will be reported at the workshop.

Speaker: Dr Simone Riggi (Istituto Nazionale di Astrofisica (INAF))

SRiggi-SKAItalyMeeting2021.pdf

66 Scientific Exploration of Spectral Cubes and catalogs using Immersive Technology: paving the way to the SKA

With the advent of the SKA and other exascale science facilities, data storage and data visualisation present the scientific community with new challenges. The Inter-University Institute for Data-Intensive Astronomy (IDIA) Visualisation Lab at the University of Cape Town (https://vislab.idia.ac.za) is thus exploring new approaches to handle the exploration and detailed interrogation of multi-parametric astronomical datasets in preparation for the SKA era. Our talk presents the beta release of a new Virtual Reality software for data cube exploration named iDaVIE-v. iDaVIE-v, developed in collaboration with INAF-OACT, combines virtual reality (VR) technology and custom-built software to work with particle and volumetric datasets, enabling user-interaction and immersive exploration of 3D data, and it was specifically designed to explore HI spectral cubes from radio interferometers. The software has been developed through the Unity game engine using the SteamVR plugin and is compatible with all commercial headsets. It is now ready for its beta release and is already showing capabilities that will serve the astronomy community at large (e.g. enabling the immersive exploration of redshift catalogues, cosmological simulations, etc.). In our talk, we will introduce the system and its current capabilities, show some recent examples in which it was used to analyse MeerKAT data and outline our plans for its future development.

Speaker: Lucia Marchetti (University of Cape Town / INAF-IRA)

Marchetti-3rdSKAItalyWorkshop-2021.pdf

67 The Ilifu Cloud Computing Facility: Enabling MeerKAT Science

The Ilifu cloud computing facility is a data intensive research facility developed by the Inter-University Institute for Data Intensive Astronomy (IDIA) and whose main aim is to facilitate the reduction and the scientific exploitation of MeerKAT data. Ilifu not only supports the data reduction of most MeerKAT Large Survey Projects and Open Time Projects but also provides a platform to collaboratively develop a variety of scientific analysis and visualization tools into a fully-fledged environment for the effective exploitation of radio surveys in a multi-wavelength context. In my talk I will introduce the rationale for Ilifu, its design and development to date. I will then detail the projects it supports and the services it provides and outline a vision for a federated South African Data Intensive Research Cloud that empowers researchers to work with and collaborate on big data science projects.

Speaker: Prof. Mattia Vaccari (University of the Western Cape)

mattia-vaccari-ilifu-at-ska-italy-20211008.pdf

68 SKA SRC - a data-centric point of view

Building a regional center for SKA poses a number of challenges that are revolving around the core of the business, namely the data products that will be made available from the SKAO facilities in South Africa and Australia. There are different scenarios that involve present and future infrastructure, software and hardware bottlenecks that will be discussed in order to provide an in-depth insight of how an SRC will potentially deal with such issues.

Speaker: Matteo Stagni (Istituto Nazionale di Astrofisica (INAF))

MatteoStagni_SKA_2021.pdf

11:10 Break

Plenary Discussion: Round Table - G. Brunetti, F. Govoni, A. Possenti, I. Prandoni, M. Tavani, G. Umana, F. Zerbi

SKA-Italy2021_Discussion_v3.pdf

69 Concluding Remarks

Speaker: Filippo Zerbi (INAF)