arXiv subjects

R. Maiolino

Publications and source records attributed to R. Maiolino.

382 records · Page 22Linked to original sources

arXiv1998

Heavy obscuration in X-ray weak AGNs

We present observations in the 0.1-100 keV spectral band of 8 Seyfert 2 galaxies, obtained by means of BeppoSAX. These sources were selected according to their [OIII] optical emission line flux, to avoid biases against obscuration on the pc scale. All sources were detected. All of them are weak X-ray emitters, and most of them are characterized by prominent iron lines at 6.4-7 keV (EW > 500 eV) and by a flat continuum, indicative of heavy obscuration along our line of sight (N_H > 10^25 cm^-2 in most cases). These results 1) provide further evidence in favor of the unified scenario, and 2) indicate that the average obscuration of type 2 AGNs is very likely much higher than deduced by former X-ray surveys. These findings have important implications for the synthesis of the X-ray background.

astro-ph↗

arXiv1997

Seyfert Activity and Nuclear Star Formation in the Circinus Galaxy

We present high angular resolution (0".15-0".5) near infrared images and spectroscopy of the Circinus galaxy, the closest Seyfert 2 galaxy known. The data reveal a non-stellar nuclear source at 2.2 microns. The coronal line region and the hot molecular gas emission extend for 20-50 pc in the ionization cone. The data do not show evidence for a point-like concentration of dark mass; we set an upper limit of 4*10^6 Mo to the mass of a putative black hole. We find evidence for a young nuclear stellar population, with typical ages between 4*10^7 and 1.5*10^8 yrs. The luminosity of the starburst inside a few hundred pc is comparable to the intrinsic luminosity of the Seyfert nucleus, and the two of them together account for most of the observed bolometric luminosity of the galaxy. Within the central 12 pc the starburst has an age of about 7*10^7 yrs and radiates about 2% of the luminosity of the active nucleus. We discuss the implications of these results for models that have been proposed for the starburst-AGN connection.

astro-ph↗

arXiv1997

Hard X--ray detection of NGC 1068 with BeppoSAX

We report on the first detection above ~10 keV of the archetypal Compton-thick Seyfert 2 galaxy NGC 1068. This detection, obtained with the PDS instrument onboard BeppoSAX in the 20-100 keV range, confirms the hardness of the X--ray spectrum above a few keV (as indicated by ASCA observations and supports models envisaging a mixture of both neutral and ionized reflections of an otherwise invisible nuclear continuum, the neutral reflection component being the dominant one in hard X-rays.

astro-ph↗

arXiv1997

X-ray detections of weak Seyfert2's with BeppoSAX

We report the detection in the X rays of two weak Seyfert2's (NGC3393 and NGC4941) with the Italian-Dutch satellite BeppoSAX. These are among the first sources observed in a sample of 12 Seyfert2's which are being studied within the BeppoSAX core program, in an effort to probe the putative torus at high X-ray energies, calibrate an isotropic luminosity indicator for absorbed nuclei, and determine the distribution of torus thicknesses, Nh. Both a Compton thick spectrum, with a reflected power law and a large equivalent width iron line, and a Compton thin spectrum, with the intrinsic power law transmitted through a large column density absorber, provide acceptable fits to both sources, with some preference for the latter model in the case of NGC4941. The high initial detection rate in our program points to a large final X-ray sample.

astro-ph↗