Revisiting narrow-line Seyfert 1 galaxies and their place in the Universe

9 Apr 2018, 09:30 → 13 Apr 2018, 16:00 Europe/Rome

Orto Botanico di Padova

Marco Berton (Dipartimento di Fisica e Astronomia, Università di Padova)

Although more than 30 years have passed since their discovery, narrow-line Seyfert 1 galaxies (NLS1s) still present challenges for unified models of active galactic nuclei (AGN). Sources of electromagnetic emission at all frequencies, their physical properties and role in galaxy evolution remain poorly understood. The aim of this workshop is to present and to discuss developments in the field over the seven years since the most recent NLS1 conference (Milano 2011). The main topics of the workshop will include the multiwavelength properties of these objects from radio wavelengths to gamma rays, their role in AGN evolution, their relationship to other classes of AGN, and their place in the framework of AGN unified models. The workshop will be held at the Orto Botanico di Padova (Italy), the world's oldest academic botanical garden. During the event, a one-hour session will be devoted to the topic of gender balance in astrophysics. This session will be dedicated to Lucrezia Cornaro of the University of Padova, the first woman in the world to obtain a Ph.D. degree. We will commemorate the 340th anniversary of this event.

Topics:

• What is the true physical nature of NLS1s?
• What can we learn from NLS1s with jets?
• What are NLS1s multiwavelength properties?
• What are the cosmological implications of NLS1s?

 

 

      

RadioNet has received funding from the European Union’s Horizon 2020 research and innovation programme under grant agreement No 730562 [RadioNet]

MAPPA_ORTO.pdf

Monday, 9 April

14:30 → 17:00 Early registration

15:45 → 16:30 Visit to Museo La Specola

16:30 → 17:15 Visit to Museo La Specola

Tuesday, 10 April

09:00 → 09:30 Registration

09:30 → 09:50 Welcome

09:50 → 10:10 Polarization in the broad lines of NLSy 1 galaxies

One of the characteristics of NLSy1 optical spectra is the narrower broad lines (FWHM~2000 km/s) and presence of strong Fe II lines around Hbeta. Additionally, very often, Hbeta and Halpha broad lines show Lorentzian like profile, that can indicate some specific kinematics of the broad line region (BLR). Polarization in broad lines can indicate the BLR kinematics (see e.g. Smith et al. 2005, MNRAS, 359, 846; Afanasiev et al. 2014, MNRAS, 440, 519; Afanasiev & Popovic 2015, ApJ, 800L, 35). Here we explore a group of NLSy1 galaxies (Mkn 335, Mkn 1501, Mkn 10,NGC 4051, Akn 564, Zw1, and PG0844+349), in order to constrain a dominant kinematics in the BLR. We found that in all observed NLSy1 the Kepelrian motion in the BLR is dominant. Using the method given in Afanasiev & Popovic 2015, we measure the masses of the central black hole in this sample of NLSy1 galaxies.

Speaker: Prof. Luka C. Popovic (Astronomical Observatory, Belgrade, Serbia)

10:10 → 10:30 Narrow-line Seyfert 1s: what is wrong in a name

Narrow-line Seyferts (NLSy1s) are an ill-defined class. Work done over the past 20 years as well as recent analyses show a continuity in properties (e.g., Balmer line profiles, blueshifts of high-ionization lines) between sources with FWHM above and below 2000 km/s, the defining boundary of NLSy1s. This finding alone suggests that comparisons between samples of NLSy1s and rest of broad-line AGNs are most likely biased. NLSy1s can be properly contextualized by their location on the quasar main sequence originally defined by Sulentic et al. 2000. At one end, NLSy1s encompass sources with strong FeII emission and associated with high Eddington ratio that hold the promise of becoming useful distance indicators; at the other end, at least some of them are sources with broad profiles seen face-on. Any rigid FWHM limit gives rise to some physical ambiguity, as the FWHM of low-ionization lines depends in a complex way on mass, Eddington ratio, orientation, and luminosity. In addition, if the scaling derived from luminosity and virial dynamics apply to the broad line regions, NLSy1s at luminosity higher than 10^47 erg/s become physically impossible. Therefore, in a broader context, a proper subdivision of two distinct classes of AGNs and quasars may be achieved by the distinction between Pop. A and B with boundary at 4000 km/s in samples at z <1, or on the basis of spectrophotometric properties which may ultimately be related to differences in accretion modes if high-luminosity quasars are considered.

Speaker: Paola Marziani (Istituto Nazionale di Astrofisica (INAF))

10:30 → 10:50 Narrow Line Seyfert 1 galaxies in the era of large surveys

Narrow Line Seyfert 1 (NLSy1) galaxies are a peculiar class of active galactic nuclei (AGN) that show strong Fe II emission, harbor low mass black holes and have high Eddington ratio compared to the broad line Seyfert 1 galaxies. The nature of this class remains unknown as most of the previous studies are limited by the small sample since only 2011 NLSy1 galaxies were known. We have carried out a systematic analysis of sources classified as QSOs in SDSS-DR12. Our systematic study has yielded a new sample of about 11,101 NLSy1 galaxies, a factor of five increase than the previously known NLSy1 galaxies. We have studied multi-wavelength properties of this large sample; radio properties using FIRST, X-ray using ROSAT, optical variability using CRTS and infrared variability using WISE. New findings of these studies will be discussed.

Speaker: Suvendu Rakshit (Seoul National University)

10:50 → 11:10 Probing narrow-line Seyfert 1 galaxies in the southern hemisphere

In this talk, I will present a new accurate catalog of narrow-line Seyfert 1 galaxies (NLS1s) in the southern hemisphere from the Six-degree Field Galaxy Survey (6dFGS) final data release, which is currently the most extensive spectroscopic survey available in the southern sky whose database has not yet been systematically explored. We classified 167 sources as NLS1s based on their optical spectral properties. We derived flux-calibrated spectra for the first time that the 6dFGS indeed does not provide. By analyzing these spectra, we obtained strong correlations between the monochromatic luminosity at 5100 Angstrom and the luminosity of H$\beta$ and [O III]$\lambda$5007 lines. The estimated central black hole mass and Eddington ratio have an average value of $9.55 \times 10^{6} M_{\odot}$ and $0.90 L_{Edd}$ respectively, which is a typical value for NLS1s. In the sample, 23 (13.8$\%$) NLS1s were detected at radio frequencies, and 10 (6.0$\%$) of them are radio-loud. Our results confirmed that radio-loud sources tend to have higher redshift, more massive black hole, and higher radio and optical luminosity than radio-quiet sources.

In this work, we increased the number of NLS1 galaxies and confirmed some well known properties of this class of AGN. This new NLS1 sample can be carried out with advanced telescopes in the southern hemisphere, such as the Extremely Large Telescope (ELT), the Atacama Large Millimeter/submillimeter Array (ALMA), and the Square Kilometre Array (SKA), for the purpose of investigating the peculiarity of NLS1s, with respect to other AGN.

Speaker: Sina Chen (University of Padova)

11:10 → 11:40 Coffee Break

11:40 → 12:00 Models of optical emission lines to investigate Narrow Line Seyfert 1 galaxies in spectroscopic databases

Since their first identification as Type 1 Active Galactic Nuclei (AGNs) with unusually narrow permitted optical lines, Narrow Line Seyfert 1s (NLS1s) represented an intriguing challenge to Astrophysicists, due to the several peculiarities of their family. Knowing that the broadening of their optical lines is caused by the Doppler effect resulting from the projected velocity distribution of their ionized gas, two competing interpretations have been classically proposed to explain their features. On the one hand, it has been suggested that these objects might be flattened systems supported by orbital motions and systematically observed at very low inclinations, thus leading to small radial velocity distributions. On the other, there is increasing evidence supporting that they could be AGNs powered by accretion of matter on a relatively low mass black hole ($M_\bullet \approx 10^6$ up to ${\sim} 10^8\, {\rm M}_\odot$) at a high rate (${>} 0.1$ times the Eddington limit), with respect to more typical Seyfert galaxies and Quasi Stellar Objects (QSOs, $M_\bullet \geq 10^8\, {\rm M}_\odot$ and $\dot{M} / \dot{M}_{Edd} \leq 0.1$).

The execution of extensive spectroscopic surveys of the sky led to the opportunity to identify several members of this family and to investigate their properties over a large range of frequencies in the electromagnetic spectrum. The interpretation of their nature, however, is still hampered by the statistical uncertainties related to the way in which NLS1 candidates are selected. In this contribution we present a study to detect and to model emission lines in optical spectra extracted from the Sloan Digital Sky Survey (SDSS), adopting the most proper strategy to identify the source of line excitation and to produce a detailed model with measurement of several emission line parameters. We show the application of this technique to explore fundamental questions, such as the presence of dust in the core of AGNs and the spectral energy distribution of their ionizing radiation, and we discuss the results obtained on a sample of NLS1 spectra collected in the SDSS. We finally summarize the potentials of this approach to identify NLS1s in present day and future spectroscopic surveys and we further consider the implications of multi-frequency data analysis for the solution of the debate concerning the NLS1 intrinsic nature.

Speaker: Giovanni La Mura (Università degli Studi di Padova)

12:00 → 12:20 Fe II reverberation in narrow-line Seyfert 1 galaxies

We present new results on the variability of the optical Fe II emission lines in 10 NLS1s observed by the Yunnan Observatory 2.4m telescope during 2012--2013. We detect statistically significant time lags, relative to the AGN continuum, in nine of the sources. This accurate measurement is achieved by using a sophisticated spectral fitting scheme that allows for apparent flux variations of the host galaxy, and several narrow lines, due to the changing observing conditions. Six of the newly detected lags are indistinguishable from the Hbeta lags measured in the same sources. Two are significantly longer and one is slightly shorter. Combining with Fe II lags reported in previous studies, we find a Fe II radius--luminosity relationship similar to the one for Hbeta, although our sample by itself shows no clear correlation. The results support the idea that Fe II emission lines originate in photoionized gas which, for the majority of the newly reported objects, is indistinguishable from the Hbeta-emitting gas. We also present a tentative correlation between the lag and intensity of Fe II and Hbeta and comment on its possible origin.

Speaker: Dr Chen Hu (Institute of High Energy Physics, Chinese Academy of Sciences)

12:20 → 12:40 Fe II velocity shifts in optical spectra of type 1 AGN

Here we present a critical view of practical problems in the analysis of optical FeII emission lines of Type 1 AGN spectra. Besides the very complex and unclear physical interpretation of the FeII template shape, there are other issues that might affect the results of FeII contribution as well (like the S/N, the AGN continuum component modelling, the complex shapes of other broad and narrow emission lines that are blending the same part of the spectrum, the galactic host stellar component that could lead to mimicking of the FeII template shape on some parts of spectrum, etc.). In this paper we concentrate particularly on the claims of possibility that in some objects FeII could be strongly shifted to the red. We examine the effects in the fitting procedure that could artificially lead to such results, discuss possible physical interpretations that could be inferred if such shifts were real.

Speaker: Dr Edi Bon (Astronomical Observatory in Belgrade)

12:40 → 14:30 Lunch

14:30 → 14:50 Reverberation Mapping and Implications for Narrow-Line Seyfert 1 Galaxies

Reverberation mapping is the principal method for determining the masses of the central black holes that power AGNs. I will discuss recent reverberation mapping results in the context of how these affect our understanding of narrow-line Seyfert 1 galaxies. I will argue that NLS1s are,for the most part, the low-luminosity extremes of a class of objects that should be defined by accretion rate rather than simply by line width.

Speaker: Dr Bradley Peterson (STScI / Ohio State Univ.)

14:50 → 15:10 Reverberation mapping of narrow-line Seyfert 1 galaxies: shortened Hbeta lags

We are carrying out a long-term reverberation mapping campaign to spectroscopically monitor narrow-line Seyfert 1 galaxies, which potentially host supermassive black holes with high accretion rates, in order to investigate the physics of their BLRs and measure their black hole masses. One of the striking new results of our campaign is that those objects deviate significantly from the canonical R_Hbeta – L_5100 relation in exhibiting systematically shorter lags for a given luminosity. I will present the latest progress of our observations and some results about the BLR geometry and kinematics.

Speaker: Dr Pu Du (Institute of High Energy Physics, Chinese Academy of Sciences)

15:10 → 15:30 Modeling time-dependence of continuum and polarized optical-UV emission in AGN

The structure and geometry of the innermost regions of AGN are still unknown. Several methods have been used to infer the size of the regions surrounding the accretion disk, otherwise unresolvable with current instruments. Polarization is one of them and it is probably one of the best tools to probe the unresolved AGN parts. In the pioneering work of Gaskell and Goosmann (2012), the authors successfully achieved a polarization reverberation mapping study of the Seyfert-1 nucleus NGC 45151. Using cross-correlation analyses, it was possible to constrain the reprocessing mechanism and radial geometry of this source, putting a clear limit on the inner radius of the broad line region. In our current work, we use the radiative transfer code STOKES to simulate the spectroscopic, polarimetric and timing behavior of any AGN, including the enigmatic narrow lines Seyfert-1s. We explore different equatorial and polar scattering regions in order to test a large model space phase. The goal of our research is to use the technique of reverberation between the total and polarized continuum emission to constrain the geometry of the innermost scattering regions in a large sample of AGN.

Speaker: Ms Andrea Rojas Lobos (Observatoire astronomique de Strasbourg)

15:30 → 15:50 Saturated luminosity of slim accretion disks in narrow line Seyfert 1 galaxies

Classical model of slim accretion disks predicts saturated luminosity which only linearly proportional to the accreting black hole mass. We show the evidence for this luminosity from the Lijiang reverberation mapping campaigns of narrow line Seyfert 1 galaxies. This lends an opportunity of using super-Eddington accreting massive black holes as cosmic candles for expansion history of the Universe.

Speaker: Jian-Min Wang (Institute of High Energy Physics, Chinese Academy of Sciences)

15:50 → 16:10 Changing-look NLS1s?

Two major challenges to unification schemes for AGN activity are the existence of NLS1s and the existence of “changing-look” (CL) AGNs. It is therefore important to look at the relationship between these two phenomena. AGNs can drastically change their spectral appearance in the optical (changing Seyfert type) and/or in the X-ray region. We illustrate the CL phenomenon with our multi-wavelength monitoring of the typical CL object NGC 2617 and discuss its properties compared with NLS1s. There are only a few examples of CL NLS1s and they are mostly changing look only in the X-ray region. Only one NLS1, PS16D (Blanchard et al. 2017), is known to have changed to a broad-line Seyfert1 (BLS1). It has been proposed that this could be a case of a tidal-disruption event (TDE). Low-ionization BLRs have a flat geometry (Gaskell 2009). If, NLS1s are flattened BLR geometries seen face-on (e.g., Decarli et al. 2011), then we will see a changing look only if the orientation of the BLR and accretion disc changes because of a major disruption such as a TDE or a close passage of a secondary black hole. If, as we have suggested (Oknyansky et al. 2015), the hot dust is in a bi-conical outflow, several observational tests can be proposed. Firstly, for NLS1s the lags of H beta and the near IR behind optical/UV continuum variability will be similar, rather than the IR lag being a factor of 3 – 10 times larges as seen in normal BLS1s. The IR response functions should not show the double peaks that are found for some BLS1s. We predict that NLS1s showing a changing look in the optical should be very rare; only X-ray or TDE CL cases should be seen, as seems to be the case. An interesting problem is why NLS1 are less variable in UV and optical regions yet strongly variable in X-ray (Klimek et al. 2004). If NLS1s include both high Eddington rate accretion and low-inclination AGNs (e.g., Peterson 2011) then a significant fraction of NLS1s could be obscured and would not be identified as NLS1s. CL cases might happen more often if there is dust sublimation following a strong increase in the optical luminosity that causes some obscured NLS1s to become unobscured.

Speaker: Dr Victor L. Oknyansky (SAI MSU)

16:10 → 16:40 Coffee Break

16:40 → 17:00 Interrogating narrow-line regions: Spatially probing metallicity and the radiation field

Maps of the gas-phase metallicity are presented for four nearby Seyfert galaxies selected from the optical S7 IFU survey, including the (obscured) narrow-line Seyfert 1 galaxy Mrk 573. We also measure the ionisation parameter, the hardness of the ionising continuum "E_peak", and the pressure across the large-scale extended narrow-line regions (ENLRs). These three parameters were constrained simultaneously with the metallicity using the new code NebulaBayes and a grid of photoionisation models. We observe metallicity gradients in a double ionisation cone, an inverse metallicity gradient, and in Mrk 573 we find a uniformly high metallicity. The near-constant ionisation parameters but steeply radially-declining pressures together imply that radiation pressure regulates the ISM density structure on large scales in all of the ENLRs in our sample. The peak of the ionising continuum, E_peak, is determined by the nuclear spectrum and the absorbing column between the nucleus and the observed nebula. Our measurements of E_peak cannot differentiate between variation in this intrinsic E_peak and spectral contamination by shock or HII-region emission. Nevertheless the E_peak measurements give insight into the excitation of the ENLRs, and the measurements could potentially be used to diagnose spectral contamination.

Speaker: Adam Thomas (Australian National University)

17:00 → 17:20 Radio and X-ray variability of the NLSy1 Mkn 110

The structure and energetics of the innermost regions of black holes are still matter of debate. In particular a lot of the attention is given to the understanding of the radiative mechanisms in coronal plasma around the black hole, as well as its connection to the accretion disk and the outflowing material in winds and jets. The simultaneity of the radio and X-ray monitoring is fundamental to obtain meaningful correlations between the two bands, and for seeking a possible common origin. We have identified the NLSy1 Mkn110 as an ideal laboratory to investigate this issue. We present our results from the multi-frequency campaign of this source, in the effort of establishing a connection between the inflow and the outflow.

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

17:20 → 17:40 Long-term spectral optical monitoring of Ark 564

Here we present the 12-year spectral optical monitoring campaign of the NLSy1 galaxy
Ark 564. The research was focused on the analysis of line and continuum light curves
with the aim to study the physics of the broad line region. Special attention was given
to the analysis of the ionized iron emission, since in this object these lines are strong
and can be distinguished from other near-by emission lines. Some interesting results are
outlined, such as the lack of correlation between the broad Balmer lines, or different
degrees of correlation between the continuum flux and Fe II emission from different spectral
multiplets.

Speaker: Dragana Ilic (Department of Astronomy, Faculty of Mathematics, University of Belgrade)

17:50 → 18:50 Guided tour: Botanical garden

Wednesday, 11 April

09:30 → 10:10 Invited Talk: Optical and high-energy properties of radio-loud Narrow-line Seyfert 1 galaxies

Radio-loud Narrow-line Seyfert 1 (NLS1) galaxies are important new laboratories
for studying the mechanism of radio-jet formation at high accretion rates and low black hole
masses, in a regime very different from classical blazars. Their strong thermal and non-thermal
spectral components shed new light on the jet-disk connection, through spectral and
SED modelling, while the gamma-ray detection severeal radio-loud NLS1s informs us about the
emission processes of gamma-rays in the central engine of low-mass AGN.
While NLS1 galaxies have been studied thoroughly at optical and X-ray energies
for decades, the populations of radio-loud, and gamma-ray emitting NLS1 galaxies
have only emerged recently. This talk provides a review of the optical and high-energy
properties of this intriguing class of AGN, including implications for NLS1 models, large-scale
ionized gas outflows, and multi-wavelength emission mechanisms.

Speaker: Dr S. Komossa (MPIfR, NAOC)

10:10 → 10:30 On the multi-wavelength properties and black hole mass estimation of several Gamma-ray detected NLS1s

The RL NLS1s hosting powerful relativistic jets revealed by gamma-ray emissions are very interesting. I report the discoveries of two new such objects SDSS J211852.96-073227.5 with flaring gamma-ray radiation (Hui Yang et al. 2018) and SDSS J122222.55+041315.7 with highest redshift by far (Su Yao et al. 2015a). We discuss their multi-wavelength properties and variability properties, along with the prototype 1H 0324+342 (Su Yao et al. 2015b). Moreover, we also present independent estimation on the black hole (BH) mass of the RL NLS1 1H 0324+342 using the X-ray timing method. We find a low BH mass of 10^7 Msun, which is consistent with that derived from the viral method using the optical broad emission lines.

Speaker: Mr Hui Yang (National Astronomical Observatories, Chinese Academy of Sciences )

10:30 → 10:50 A close look at the gamma-ray emitting NLSy1 FBQS J1644+2619

FBQS J1644+2619 is one of the most recently discovered gamma-ray emitting NLSy1s. In this talk I will present a multiwavelength analysis of this source, focussing on a recent 80 ks X-ray observation with XMM-Newton. The spectral energy distribution of the source is similar to the other gamma-ray NLSy1s, confirming its blazar-like nature. The X-ray spectrum is characterised by a hard photon index (Gamma = 1.66) above 2 keV and a soft excess at lower energies. The hard photon index provides clear evidence that inverse Compton emission from the jet dominates the spectrum, while the soft excess can be explained by a contribution from the underlying Seyfert emission. This contribution can be fitted by reflection of emission from the base of the jet, as well as by Comptonisation in a warm, optically thick corona. I also compare these results with X-ray observations of other gamma-ray NLSy1s. The majority of the sources have similar X-ray spectra, with properties intermediate between blazars and radio-quiet NLSy1s.

Speaker: Dr Josefin Larsson (KTH Royal Institute of Technology, Stockholm)

10:50 → 11:10 The gamma-ray emitting NLS1 1H 0323+342 and the disc-jet connection

The Fermi Gamma-Ray Space Telescope has detected gamma-ray emission from a rare sub-set of radio-loud narrow-line Seyfert 1 (NLS1) galaxies, confirming the presence of blazar-like jets. This discovery has challenged the paradigm that powerful, relativistic jets are only associated with large, elliptical galaxies hosting the most massive central black holes. The small population of gamma-ray emitting NLS1s extends the blazar population down to low black hole masses and so allows us to investigate how jets scale with black hole mass.

We have performed a detailed analysis of the comprehensive multi-wavelength data set assembled for the lowest-redshift gamma-ray emitting NLS1, 1H 0323+342. This involves application of accretion flow and jet emission models to explore the disc-jet connection in greater depth than previously possible. We show that standard scaling relations vastly overpredict the jet power of this source. That gamma-ray emitting NLS1s appear to host such low-powered jets may go some way to explaining why so few have been detected to date.

Speaker: Mr Daniel Kynoch (Durham University)

11:10 → 11:40 Coffee Break

11:40 → 12:00 Optical and radio polarisation properties of gamma-ray emitting NLSy1s

Since the first detection of gamma-ray emission from NLSy1 by Fermi, we have been systematically been studying their jet emission with emphasis on the radio bands. In Foschini et al 2012 and in Angelakis et al 2015 we presented the first analysis that showed the presence of mildly relativistic jets not different from what we see in typical blazars. In the latter we conduct a thorough analysis of the variability and we present estimates of the jet power in support of this claim. Subsequently, we focused on the polarised emission. We have been conducting a long term multi-frequecny radio and R-band optical polarisation monitoring that has revealed vey interesting behaviour from this class of sources.

Here we will review the findings of the polarisation monitoring with emphasis on the optical band that has shown a very interesting behaviour. On the basis of this analysis we will hypothesise on the physical processes at the source and the temporal behaviour of their magnetic fields.

Speaker: Emmnouil Angelakis (Max-Planck-Institut für Radioastronomie)

12:00 → 12:20 Fermi LAT Flare Advocate seeds for the NLSy1 multi-wavelength science blossom

Since August 2008 the Fermi Flare Advocate service (also known as all-sky Gamma-ray Sky Watcher, FA-GSW) is providing for a quick look and review of the gamma-ray sky observed day by day by the Fermi Large Area Telescope (LAT). The FA-GSW duty is based on high level software pipelines with shifter-driven analysis and summaries about the gamma-ray sources of the day, their status and multi-frequency checks of sources whenever needed.

The service results in alerts and communication to the external community for potentially new gamma-ray sources, interesting transients and flares, for example through the Fermi multiwavelength mailing list, Astronomer's Telegrams and Gamma-ray Coordinates Network notes.

Target of opportunity observing programs to other satellites are also performed by the on duty shifter. Statistics and a summary of more than 9.5 years of FA-GSW service are here presented citing, in particular, the cases where the FA-GSW duty was successful in the prompt address for potential interesting flares and brightening of gamma-ray NLSy1 galaxies.

Speaker: Dr Stefano Ciprini

12:20 → 12:40 Prospects for gamma-ray observations of narrow-line Seyfert-1 galaxies with the Cherenkov Telescope Array

Gamma-ray emitting narrow-line Seyfert-1 (g-NLSy1) galaxies are jetted sources,
harbour a relative low-mass black hole (10$^6$ - 10$^8$ Solar masses) which accretes
close to the Eddington limit. g-NLSy1 galaxies show characteristics similar
to those of blazars, such as flux and spectral variability in the gamma-ray energy
band and radio properties which indicate the presence of a relativistic jet.
These characteristics make them an intriguing class of sources to be investigated
by the Cherenkov Telescope Array (CTA), the next-generation ground-based
gamma-ray observatory.
CTA will cover the 20 GeV - 300 TeV energy range, with an average differential
sensitivity a factor 5-20 better with respect to the current imaging atmospheric
Cherenkov telescope (IACT) arrays. For transients/flaring events (time-scales
of ~1 day or shorter) CTA will be about two orders of magnitude more sensitive with
respect to Fermi-LAT at the overlapping energy of 25 GeV, allowing an unprecedented
opportunity to investigate flaring g-NLSy1 galaxies.
We present preliminary results obtained by simulating a few g-NLSy1 galaxies
by means of the CTA public ctools software and the public instrument response files,
investigating their possible detection and spectral properties, taking into
account both the effect of the extra-galactic background light in the
propagation of gamma-rays and intrinsic absorption components.

Speaker: Dr Patrizia Romano (Istituto Nazionale di Astrofisica (INAF))

12:40 → 14:30 Lunch

14:30 → 15:10 Invited talk: Radio Properties of Narrow-Line Seyfert 1 Galaxies

The last decade has witnessed a flurry of observational studies
concerning the rare class of radio loud narrow-line Seyfert 1 galaxies
(RL-NLSY1), of which several hundred are currently known. Much of
this activity was sparked by the unexpected detection of several
RL-NLSY1 by the Fermi gamma-ray observatory in 2009. The flux
variability seen in gamma-rays suggested the presence of a powerful,
aligned relativistic jet, which has subsequently been confirmed in
several cases by VLBA milliarcsecond-scale radio imaging. In this
review I discuss several outstanding issues raised by recent pc- and
kpc-scale radio observations of RL-NLSY1s. Specifically these involve
how low black hole mass, high accretion rate systems can produce
powerful jets, the potential for unifying RL-NLSY1s with other AGN
types on the basis of orientation, the possible contamination of
radio flux in RL-NLSY1s from star formation, and whether these rare
objects may represent a young AGN population. I will additionally
present updated pc-scale jet kinematics analyses of several RL-NLSY1s
from the MOJAVE VLBA monitoring program.

Speaker: Matthew Lister (Purdue University)

15:10 → 15:30 Parsec-scale Nuclear Radio Structures in Seyfert Galaxies

I will present results from multi-frequency Very Long Baseline
Interferometry (VLBI) observations of Seyfert galaxies. These observations
are probing the parsec-scale nuclear structures in these spiral galaxies. They
are revealing the presence of a variety of weak radio outflows in these galaxies
and the tentative presence of dual radio cores which could be dual accreting
supermassive black holes, in one of them. The properties of some of the weak
outflows are more consistent with being bases of coronal winds rather than
synchrotron self-absorbed bases of relativistic jets. I will discuss the different
parsec-scale radio structures that we observe in these low luminosity AGN.

Speaker: Preeti Kharb (NCRA-TIFR)

15:30 → 15:50 High-frequency radio properties of NLS1 galaxies

37 GHz observations performed at Metsähovi Radio Observatory show that NLS1 galaxies are not as radio-quiet as usually presumed. The detection rate at 37 GHz is around 19%. Furthermore, high-frequency radio emission is also detected from sources classified as radio-silent; that is from sources that have no counterpart in the VLA FIRST survey at 1.4 GHz. This means that at the time of the survey, there was no active jet in the sources, and the jet was launched or activated later. We have also started to look at the radio morphologies and host galaxies of NLS1 sources to find out whether the jets are generated in spiral galaxies, or in disturbed or interacting systems. Unbiased samples of NLS1 galaxies, independent of, for example, their radio loudness parameter which is often used for searching characteristics such as gamma-ray emission, are needed to look at the population as a whole, and to arrive at meaningful conclusions of their evolution and place in the AGN zoo.

Speaker: Anne Lahteenmaki (Aalto University Metsahovi Radio Observatory & Dept of Electronics and Nanoengineering)

15:50 → 16:10 VLBI study of the jets in radio-loud narrow-line Seyfert 1 galaxies

Narrow-line Seyfert 1 galaxies have relatively small black hole masses, and high accretion rates, thus are thought to be young AGNs. Radio-loud narrow line Seyfert 1 galaxies (RLNLS1s) are very special, because some of them show blazar-like characteristics, while others resemble compact steep-spectrum sources. Relativistic jets were shown to exist in a few RLNLS1s based on VLBI observations and confirmed by the gamma-ray flaring of some of them. These properties are unexpected, in light of the low black hole masses, high accretion rates, and possible spiral hosts of these RLNLS1s. With their remarkable multi-wavelength properties and extreme location in AGN parameter space, RLNLS1s allow us to re-address some of the key questions regarding the physics of jet formation, for example, the physical conditions under which a jet can be launched. In this talk, we will present our series of work on the compact radio structure of radio-loud narrow line Seyfert 1 galaxies based on VLBA observations, including the sample study for a sample of 33 RLNLS1s, the multi-band VLBA studies on two gamma-ray sources (J1443+4725 and J2118-0732), and multi-epoch variability and kinematic study on several sources. The implications on the jet formation are discussed based on the pc-scale jet properties.

Speaker: Dr Minfeng Gu (Shanghai Astronomical Observatory)

16:10 → 16:40 Coffee Break

16:40 → 17:00 The JVLA view of NLS1

I will present the results of the largest radio survey to date dedicated to narrow-line Seyfert 1 galaxies (NLS1). We observed 72 objects with JVLA in A-configuration, obtaining high-resolution maps with unprecedented sensitivity. The sample includes both formally radio-quiet and radio-loud NLS1s, confirming a substantial morphological difference between these two classes at fixed flux sensitivity. Furthermore, I will show how, unlike classical blazars, flat-spectrum radio-loud NLS1s do not show strong diffuse emission, suggesting that NLS1s have underdeveloped radio lobes, possibly because of their young age. Finally, I will discuss these results in the frame of an orientation-based unification of young radio-loud AGN.

Speaker: Marco Berton (Università di Padova)

17:00 → 17:20 The strange case of Mrk 783

Narrow-line Seyfert 1 galaxies (NLS1s) are a class of active galactic nuclei (AGN) characterized by narrow permitted emission lines, low [O III]/H$\beta$ ratio and the presence of Fe II multiplets in the spectrum, indicating that the inner part of the AGN is not obscured. Even though they have been discovered almost 30 years ago, their nature is still under debate and, for these reasons, new observational campaigns have been recently carried out specifically to study the properties of NLS1s.

In a recent VLA radio survey of NLS1s at 5 GHz, we discovered an object with very interesting properties. This galaxy, Mrk 783, showed an emission with a maximum extension of 14 kpc characterized by very steep spectral indexes, which has been tentatively classified as a relic due to intermittent activity of the AGN.

However, this source shows even more peculiar properties than the extended radio emission. SDSS images show the presence of extended structures, likely spiral arms or tidal tails, and of a compact emission 1.5" West with respect to the position of the AGN, which becomes more and more evident moving towards redder filters. Those features might be a hint of a recent interaction of the object with a companion. A preliminary spectroscopic follow-up in the optical band (Congiu et al. 2017c) also discovered a very extended emission that seemed to be aligned (at least partially) to the radio one. The [O III] emission line can be traced up to $\sim $ 30 kpc from the nucleus, making Mrk 783 one of the first NLS1s with an extended narrow-line region (ENLR) and the object with the larger ENLR discovered so far. From the preliminary analysis, the emission seems to be caused mainly by gas ionized by the AGN, but traces of star formation have been observed.

What is happening in this galaxy? How the AGN is related to the peculiar properties of this object? In this talk I will try to answer these questions presenting the final results of the analysis of the data, discussing their implication in the characterization of the AGN and of its host galaxy and how Mrk 783 is related to the class of the NLS1 galaxies.

Speaker: Enrico Congiu (Dipartimento di Fisica e Astronomia "Galileo Galilei", Università di Padova)

17:20 → 17:40 Kpc-scale radio-jets in narrow-line Seyfert 1 galaxies

Narrow line Seyfert 1 galaxies (NLS1s) are a subclass of active galactic nuclei (AGN) that show broad permitted optical emission lines of widths relatively narrower (FWHM $<$ 2000 km s$^{-1}$) than that are usually seen in normal AGN. In general, NLS1s are believed to be radio-quiet and possess smaller super-massive black boles with higher accretion rates. Contrary to the conventional paradigm we discover several new NLS1s with kpc-scale jet-lobe radio structures. The discovery of these rare AGN allows us to probe the jet production in hitherto unexplored parameter space of black hole mass and accretion rate. In this talk I shall discuss the jet production efficiency in NLS1s.

Speaker: Dr Veeresh Singh (Physical Research Laboratory, Ahmedabad, India)

20:00 → 23:00 Social Dinner

Time and location TBC

Thursday, 12 April

09:30 → 10:10 Invited: Narrow Line Seyfert 1 galaxies in the context of Quasar Main Sequence

NLS1 galaxies are considered to be high Eddington ratio sources. But in the context of Quasar Main Sequence, high Eddington rate sources are those which have weak [OIII] lines and strong Fe II lines. There is an overlap between the two populations, but they are not identical. I will discuss this issue from the point of view of the broad band SED, emission line shape modelling, Fe II pseudo-continuum strength, and the level of X-ray variability. I will also discuss the issue of the viewing angle and the insight we gain from spectro-polarimetric observations.

Speaker: Prof. Bozena Czerny (Center for Theoretical Physics, Warsaw)

10:10 → 10:30 The nature of the gamma-ray emitting PKS 2004-447: CSS or NLS1?

PKS 2004-447 has been one of the five radio-loud Narrow-Line Seyfert 1 (NLS1) galaxies that were first discovered to carry a powerful relativistic jet. Despite being the radio-loudest among the original gamma-ray emitting NLS1 sample it is also among the most disputed NLS1s because its classification is not unambiguously clear. We show new results from a large multiwavelength program from radio to gamma-rays spanning more than five years from 2011 until 2017. We studied the longterm broadband spectral evolution of this unique object using a series of spectral energy distributions and parsec-scale resolution VLBI observations. The source continues to be unique among gamma-ray emitting NLS1 and intriguing in comparison to other radio-loud AGN as the multiwavelength data exhibit typical blazar-like characteristics while the radio data reveal a powerful one-sided and a consistent radio spectrum. The radio proerties are consistent with CSS sources, a class of radio-loud AGN that is usually associated with young radio sources.

Speaker: Annika Kreikenbohm (University of Wuerzburg)

10:30 → 10:50 Relativistic spectroscopy of the extreme NLS1 IRAS 13224

I will review results from the 2016 observing campaign on the most X-ray variable AGN, IRAS 13224. This source shows both extreme relativistic reflection from the inner accretion disk and an ultra-fast outflow, both variable on timescales of under an hour. As no other absorption features are present in the spectrum, we have a clean view of the inner accretion disk and the relativistic physics exhibited there. I will also discuss the implications of these results, and potential next steps for expanding our knowledge of accretion and outflows using NLS1s.

Speaker: Michael Parker (ESA/ESAC)

10:50 → 11:10 The variability of soft X-ray excess and UV emission : a case study of a NLS1 II Zw 177

Narrow Line Seyfert 1 (NLS1) galaxies are a unique class of active galactic nuclei. This class shows rapid variability in the X-ray and the UV/optical bands. Normally, the NLS1 consists of strong soft excess below ~2 keV and the broad / narrow iron lines near 6 keV along with dominating power-law continuum in the X-ray band. The origin of the soft X-ray excess is a mystery since its discovery in 1990's. We present the results from our own ~130 ks and an old ~13 ks XMM-Newton observations of a NLS1 II Zw 177. We found strong soft excess below 2 keV in both observations and we applied physical models such as the blurred reflection from inner ionized accretion disk and the optically thick, cool Comptonization to investigate the origin of soft excess. Our study reveals that soft X-ray excess is described very well by the blurred reflection from the partially ionized disk as well as by the optically thick, cool Comptonization. Interestingly, time resolved spectroscopy with U band exposures and corresponding X-ray favors that the soft X-ray excess is likely due to the blurred reflection phenomenon. The changes in the UV emission is possibly related to the variations in the accretion flow.

Speaker: Mr Main Pal (Physical Research Laboratory)

11:10 → 11:40 Coffee Break

11:40 → 12:40 Gender balance session

12:40 → 14:30 Lunch

14:30 → 15:10 Invited: X-ray perspective of Narrow line Seyfert 1 galaxies

The X-ray regime is arguably where NLS1s exhibit their most extreme characteristics. In the past decade, X-ray observations of NLS1s have revealed reverberation lags, enhanced Fe La and Fe Ka relativistic emission, dynamic coronae, and ultrafast outflows. I will review recent work on famous sources like IRAS 13224-3809, 1H 0707-495, and Mrk 335, highlighting their most interesting properties. I will attempt to describe the NLS1 phenomenon into context of general AGN behavior.

Speaker: Luigi Gallo

15:10 → 15:30 Ionized outflows in the NLSy1 IZw1: departing from the classical picture

NLSy1s often present complex systems of ionized absorption both in the X-ray and UV band. Absorption by dust of unclear origin (from within the ionized absorber or from dusty merging events), ultrafast outflows and finally warm absorbers with peculiar variability.
We present a simultaneous spectroscopy campaign using XMM-Newton and HST-COS on the bright NLSy1 IZw1.
This source already displayed peculiar behaviour in past observations (Costantini et al. 2007), showing multi-component UV-X warm absorber in apparent constant non-equilibrium and a variable iron K alpha line (Gallo et al. 2007).
Our recent campaign casts a new light on the warm absorber behaviour, showing a clear link between the low-, the high- ionization and the UV gas components as well as a variable column density (Silva, Costantini et al. A&A submitted).
These observational elements clearly challenge the classical conical-shaped outflow in ionization equilibrium. The observational evidences strongly favour episodes of plasma ejection, possibly from the accretion disk.

Speaker: Dr Elisa Costantini (SRON, Netherlands Institute for Space Research)

15:30 → 15:50 Narrow Line Seyfert 1s in the IBISCO Sample

I will present the broad-band soft and hard X-ray spectral analysis of 8 Narrow Line Seyfert 1 galaxies extracted from the IBISCO Sample. The study also focuses on the properties of the NLS1 in our sample in relation to those of the IBISCO parent Seyfert population. The IBISCO sample comprises 57 AGN selected from the INTEGRAL IBIS AGN catalogue (in the 20-100 keV band), with z<0.05 and covering a wide range of luminosities, BH masses and absorption and all characterised by CO measurements. The main goal of this analysis is to accurately determine the X-ray continuum emission, the presence of absorption features around 7 keV (indicative of the presence of outflows) and study the accretion parameters of the eight IBISCO NLS1, in order to study the accretion mechanisms and investigate the feeding and feedback cycle in these peculiar AGN. I will discuss our preliminary results, showing that NLS1 tend to have higher Eddington ratios and larger molecular gas fractions than their parent Seyfert population in the IBISCO sample. Finally, I will discuss the nuclear (AGN) vs. host galaxy properties scaling relations of NLSY1 in relation to the parent Seyfert population.

Speaker: Dr Manuela Molina (INAF OAS Bologna)

15:50 → 16:10 Testing strong gravity with RELXILL_NK and the black hole in Ark 564

Einstein's gravity has been extensively tested in the weak field regime, mainly with experiments in the Solar System and observations of binary pulsars, and current data well agree with theoretical predictions. On the contrary, strong gravity is largely unexplored and there are a number of theories beyond Einstein's gravity having the same predictions for weak fields and presenting deviations only when gravity becomes strong. The best laboratory for testing strong gravity is the spacetime around astrophysical black holes. X-ray reflection spectroscopy can be a powerful tool to probe the strong gravity region around astrophysical black holes and test the nature of these objects. In this talk, I will introduce RELXILL_NK, which is the first XSPEC reflection model to test Einstein's gravity in the strong field regime, and I will present the constraints on possible deviations from Einstein's gravity that I have obtained by analyzing Suzaku data of Ark 564.

Speaker: Mr Ashutosh Tripathi (Fudan University)

16:10 → 16:40 Coffee Break

16:40 → 17:00 The nature of X-ray spectral variability in MCG-6-30-15

The flux-flux plot (FFP) method is a model-independent way that allows to extract stable components from the X-ray spectra of AGNs showing strong variability. I will present in my talk the results obtained by applying this method to simultaneous XMM-Newton and NuSTAR observations of MCG-6-30-15 and we were able to identify a constant (over >4.5 days) component of the X-ray emission in this source. In addition, we identified the variable spectral component in this source that is consistent with a primary plus relativistic reflection that are modified by warm absorption. Instead, the constant emission consists of a blackbody (kT ~ 0.1 keV) responsible of the constant soft excess and a neutral reflection, from distant neutral material, dominating at energies above ~1.6 keV.

Speaker: Elias Kammoun (SISSA - Trieste)

17:00 → 17:20 On the underlying physics of NLS1

The X-ray spectra of NLS1 are very exciting and controversial. They can be fit with a compact (less than $1R_g$) X-ray source close to the event horizon of an extreme spin black hole (lamppost), where reflected emission from the inner disc can dominate over the intrinsic emission due to lightbending. This has exciting implications for observing extreme gravity. The same X-ray spectra can also be fit by absorption in a clumpy wind from the inner disc, where the material is outflowing at $\sim 0.2c$, with no constraint on black hole spin. This alternative explanation has exciting implications for observing AGN feedback via winds. Including multiwavelength data strongly supports the winds interpretation, as the optical/UV continuum seen from some of these sources requires that the accretion flow is superEddington. Strong winds must be produced from such flows, and orientation with respect to a clumpy wind can explain the difference between NLS1 which show 'complex' X-ray spectra and rapid variability (e.g 1H0707-495) and 'simple' ones (e.g RXJ0439.6-5311) which show neither of these properties despite having identical optical/UV spectra (including Hbeta line profiles) i.e. have the same black hole mass and mass accretion rate. These objects are all very radio weak, and the high spin constraints from reflection models were the major reason for abandoning the spin paradigm for highly relativisitic jets. Strong supporting evidence for this simple model comes from a large SDSS sample of all types of AGN. This opens the way for a quantatative model of AGN jets to understand their feedback on the host galaxy.

Speaker: Prof. Chris Done (University of Durham)

Friday, 13 April

09:30 → 09:50 The Polar Dust in ESO 323-G77

The dusty torus in AGN unification has long been thought as the source of obscuration in AGN. However, until recently, we did not have the capability to directly observe this dusty structure. Advancements in the field of IR interferometry have finally allowed us to get a glimpse of the warm and hot dust structure on the scale of the putative torus. Interferometric studies of the brightest local Seyfert galaxies (z < 0.05) have been undertaken and of those with enough data to discern the angular dependence of the dust distribution, we do not see a simple equatorially-extended structure in the mid-IR. Instead, strong extended dust emission from the polar region is detected in most of the objects, with a subdominant compact or disk-like component in the plane of the accretion disk. In this talk, we will report results of ESO 323-G77, the first Narrow Line Sy1 galaxy (as classified by Sani et al. 2009) to be studied in detail with IR interferometry. While we do find strongly polar-elongated dust emission (axis ratio 3:1) as in other Seyfert galaxies, it is contributing only about 40% to the total mid-IR emission, and thus not dominant. 60% of the 12um flux originates from an unresolved source. Using full IR SED and the 3D radiative transfer model CAT3D-WIND, we interpret that this unresolved mid-IR emission is the Rayleigh-Jeans tail of hot dust emission from the inner part of a dusty disk close to the sublimation radius. These results indicate strong similarities of the NLS1 ESO 323-G77 with the compact emission seen in two quasars (Kishimoto et al. 2011) and suggests evolution of the dust distribution with Eddington ratio.

Speaker: James Leftley (ESO)

09:50 → 10:10 Hot Dust in the Narrow Line Seyfert 1 Galaxy ESO323-G77

We are currently undertaking an optical and near-infrared (IR) monitoring campaign of a sample of nearby AGN. One of the aims of the study is to understand whether the dusty environment surrounding the black hole depends on the physical properties of the AGN, such as luminosity or accretion rate. The dust in this region is commonly referred to as the 'torus' and serves as a reservoir for accretion and provides the angle-dependent obscuration required in the unification scheme. ESO323-G77 is the only narrow-line Seyfert 1 galaxy in the sample and serves as a proxy for highly accreting objects. The time lag between the optical and near-IR emission is a measure of the physical size of the innermost hot dust around the AGN. For ESO323-G77, we measure $73^{+3}_{-5}$ days or ~0.061 pc, which is consistent with the lag-luminosity relation found for normal Seyfert galaxies. The transfer function between the optical and near-IR variability shows that the hot dust distribution is also very similar to other Seyfert galaxies. Therefore, we can conclude that the properties of hot dust in a normal AGN at the same luminosity are comparable to this narrow line Seyfert 1.

Speaker: Bella Boulderstone (University of Southampton)

10:10 → 10:30 What is in a radio loud NLS1?

In many of radio loud NLS1 galaxies has been found evidence of disturbed
host morphology, in some cases hinting for merger processes, that are
putative sources of gas replenishment. We have been investigating the
less known radio loud NLS1 population, in the relatively nearby Universe (z<1),
that have flat radio spectrum, assumed to be the manifestation of the presence
of a radio jet. In a fraction of the objects the infrared emission is well
fitted by a combination of an AGN component and an "active" host galaxy
component like M82, the estimate SFR being in the LIRG/ULIRG range
(10-500 Msolar/yr). In order to better characterise that component we have been investing the submillimetre emission of these sources, something that has never been tested at our
knowledge, using APEX. Here we present the results concerning a pilot
sample of 3 representative objects.

Speaker: Sonia Anton (CIDMA - Univ Aveiro)

10:30 → 10:50 X-ray variability plane using NLSy1 and Sy1: Importante of obscuration

Scaling relations are the most powerful astrophysical tools to set constraints to the physical mechanisms of astronomical sources and to infer properties for objects where they cannot be accessed directly. We have re-investigated one of these scaling relations using NLSy1 and Sy1; the so-called X-ray variability plane (or mass-luminosity-timescale relation, McHardy et al. 2006). This relation links the power-spectral density (PSD) break frequency with the SMBH mass and the bolometric luminosity. We used all available XMM-Newton observations of a sample of 22 Sy1 and NLSy1 to study the PSD and spectra in short segments within each observation. This allows us to report for the first time that the PSD break frequency varies for each object, showing variations in 19 out of the 22 AGN analyzed. Our analysis of the variability plane confirms the relation between the break frequency and the SMBH mass and finds that the obscuration along the line of sight (or the variations on the obscuration using its standard deviation) is also a required parameter. We constrain a new variability plane of the form: $\rm{log(\nu_{Break})}$ = -A log($\rm{M_{BH}}$) + B log($\rm{N_H}$) - C (or $\rm{log(\nu_{Break})}$ = -A log($\rm{M_{BH}}$) +B $\rm{\Delta(log(N_H}$))+ C). The X-ray variability plane found by McHardy et al. (2006) is roughly recovered when we use unobscured segments. We speculate the PSD shape is related with the outflowing wind close to the accretion disk in NLSy1 and Sy1.

Speaker: Omaira Gonzalez-Martin (IRyA)

10:50 → 11:10 The mass of NLS1 black holes: reconciling accretion disk and virial estimates

We present a new catalog of spectral properties for a sample of 55 radio-loud NLS1 observed at optical and UV wavelengths, providing emission line luminosities and widths, continuum luminosities and slopes.

We used this catalog to estimate the black hole masses of the sample by means of the accretion disk modeling technique. The obtained masses are systematically larger than those derived with the virial method by a factor of ~5, and the Eddington ratios are correspondingly lower.

Finally, we discuss a possible way to reduce the discrepancies, and reconcile the estimates provided by the two techniques, exploiting an alternative accretion disc model that reliably describes the emission of a highly accreting, radiatively inefficient disc.

Speaker: Dr Giorgio Calderone (INAF-OATs)

11:10 → 11:40 Coffee Break

11:40 → 12:00 The host galaxies of radio-loud vs. gamma-loud Narrow-Line Seyfert 1s

The production of intense levels of gamma-rays requires a powerful relativistic jet in order to accelerate particles up to the highest energies. In the current AGN paradigm, powerful jets are exclusively launched from elliptical galaxies. We present first results from our near-IR host galaxy imaging survey of radio-loud (but not gamma-ray detected) Narrow-line Seyfert 1 galaxies (NLSy1). With structural modelling and colour information, we characterize their host galaxies, and compare their properties with those of gamma-loud NLSy1s, and high- and low-luminosity blazars (FSRQs and BL Lacs), previously studied by us (Kotilainen et al. 2016; Olguin-Iglesias et al. 2016,2017). This allows us to statistically investigate whether non-bulge dominated, evolutionarily young galaxies are able to launch relativistic jets powerful enough to shine at gamma-rays.

Speaker: Jari Kotilainen

12:00 → 12:20 Host galaxies of jetted narrow-line Seyfert 1 galaxies

Host galaxy morphology studies of jetted narrow-line Seyfert 1 galaxies (NLS1) are scarce; so far only three of them have been investigated in detail. Though all three are hosted by late-type galaxies the sample size is too small to establish a preferred host galaxy type for jetted NLS1 sources; increasing the sample size is crucial to achieve statistically significant results. To this end we observed the host galaxies of nine NLS1 sources in near-infrared using NOTCam at the Nordic Optical Telescope. Seven of these sources are jetted based on the 37 GHz observations at Metsähovi Radio Observatory (see A. Lähteenmäki's talk). To determine the morphological types of the hosts we performed photometric decomposition of the near-infrared images using GALFIT. Here we present the results of the host galaxy modeling, discuss the importance of this study to our understanding of the nature of the diverse NLS1 population, as well as its significance and implications for active galactic nuclei research in general.

Speaker: Emilia Järvelä (Metsähovi Radio Observatory)

12:20 → 12:50 Final remarks and goodbyes