The presence of ionized gas in Active Galactic Nuclei is revealed by the observed emission lines, which imply a wide range of ionization states, densities, geometries and kinematics. Dense, fast gas occurs on sub-pc scales (Broad Line Region), while slow tenuous gas appears at scales from pc to kpc (Narrow Line Region). Despite this varied phenomenology, very clear predictions can be derived...
The primary emission in Actve Galactic Nuclei (AGN) is widely believed to be due to Comptonization of the thermal radiation from the accretion disk in a "corona" of hot electrons. The resulting spectra can, in the first approximation, be modelled with a cut-off power law.
Taking advantage of MoCA, a Monte Carlo code calculating spectral and polarization properties of the coronal emission, we...
I will show the results of the hot corona parameters of active galactic nuclei (AGN) that have been recently measured with NuSTAR in collaboration with other X-rays observatories. In the work I will present, we analyzed values taken from the literature of a sample of 19 bright local Seyfert galaxies to look for correlations between coronal parameters, such as the photon index and cut-off...
The Shakura-Sunyaev model is the mostly adopted description of the thermal emission produced by the accretion disk around a black hole and infers rough estimates of the disk luminosity and the black hole mass. More advanced models have been developed in order to account for general relativistic effects, including the role of the black hole spin. My aim here is to describe and compare two...
We present results from broad-band (UV to hard X-rays) monitoring campaigns, carried out in recent years, on three different AGNs: a prototypical Seyfert 1 (NGC 4593), a broad-line radio galaxy (3C 382), and a highly accreting Seyfert 1 (HE 1143-1810). In all cases, the campaigns consisted of five joint XMM-Newton/NuSTAR observations, plus VLBA joint observations for 3C 382. The high-energy...
An accreting super massive black hole lurks at the center of AGNs and QSOs. Measuring its mass is not trivial due to the very small size of the sphere of influence, and the high luminosity of the AGN itself when compared to the stars in the host galaxy.
I will review the currently available methods to measure the black hole mass of Type 1 AGNs (reverberation mapping, virial methods,...
Virial–based methods for estimating active supermassive black hole masses are commonly used on extremely large spectroscopic quasar catalogs. Most spectral analyses, though, do not pay enough attention to the detailed continuum decomposition. To understand how this affects virial mass estimates, I tested the influence of host galaxy light on them by means of a detailed spectral analysis with...
We performed a spectroscopic analysis of a SDSS DR7 sample of >12000 quasars as a function of their orientation with respect to the line of sight, as indicated by the equivalent width (EW) of the [OIII] line. This confirmed the presence of orientation effects in both the narrow and the broad lines, thus providing information on the geometry and kinematics of the Narrow Line Region and the...
Back in the late eighties - early nineties, Mkn 590 was ingesting mass at a rate that only NLSy1s do. Consequently, its permitted optical broad emission lines (BELs) were narrow (FWHM~2500 km/s) and its soft X-ray spectrum rather steep. Twenty five or so year later, the source had dramatically slowed down eating (factor of 100) and both its BELs and soft X-ray excess (SXE) had disappeared,...
The August 2014 NuSTAR observation of the Seyfert 2 galaxy NGC 1068 allowed us to discover a hard X-ray flux excess with respect to observations performed 20 months earlier and 6 months later. This variability was ascribed to an unveiling event during which Compton-thick material moved temporarily out of our line of sight enabling us to unveil the direct nuclear radiation of this buried AGN....
We report on an optical (SDSS) and X-ray (XMM-Newton) study of an optically selected
sample of four dual AGN systems at projected separations of 30–60 kpc. Six of eight objects are obscured in X-rays with NH~10^23 cm-2; three of those, whose X-ray spectrum is dominated by a reflection component, are likely Compton-thick. This finding is in agreement with the hypothesis that galaxy encounters...
