相关论文: X-ray absorption in Active Galactic Nuclei

In this proceedings paper, I overview the current status of the X-ray luminosity function of AGNs in the soft (0.5-2 keV) band, extended using XMM-Newton and Chandra survey data. We found that the number density of low luminosity AGNs peaks…

To provide insight into the apparent mismatch between the optical and X-ray absorption properties observed in 10-30 % of Active Galactic Nuclei (AGN), we have conducted a detailed study of two X-ray unabsorbed AGN with a type-2 optical…

Variable X-ray absorption has been observed in active galactic nuclei (AGN) on several time scales. Observations allow us to identify the absorber with clouds associated either with the clumpy torus (parsec scales, long timescales) or with…

Although soft X-ray absorption features in AGN were discovered almost ten years ago, the nature and location of the gas creating them has remained controversial. However, by making use of the newly-available high-resolution spectra provided…

The spectrum of the hard X-ray background records the history of accretion processes integrated over the cosmic time. Several pieces of observational and theoretical evidence indicate that a significant fraction of the energy density is…

We briefly review the synergy between X-ray and infrared observations for Active Galactic Nuclei (AGNs) detected in cosmic X-ray surveys, primarily with XMM-Newton, Chandra, and NuSTAR. We focus on two complementary aspects of this…

A number of emission and absorption features are expected to be visible in high energy resolution X-ray spectra of type 1 AGN with ionized gas along the line of sight (so called "warm absorbers"). Emission strongly depends on the…

We report on the performance of the statistical, X-ray absorption lines identification procedure XLINE-ID. As illustration, it is used to estimate the time averaged gas density $n_H(r)$ of a representative AGN's warm absorber ($T\approx…

We study the incidence of nuclear obscuration on a complete sample of 1310 AGN selected on the basis of their rest-frame 2-10 keV X-ray flux from the XMM-COSMOS survey, in the redshift range 0.3<z<3.5. We classify the AGN as obscured or…

We briefly review how X-ray observations of high-redshift active galactic nuclei (AGNs) at z = 4-7 have played a critical role in understanding their basic demographics as well as their physical processes; e.g., absorption by nuclear…

The most common observed feature of the X-ray outflows in active galactic nuclei (AGN) is their broad ionization distribution spanning up to $\sim$ 5 orders of magnitude in ionization levels. This feature is quantified in terms of…

Combining information on absorbing material in AGN from X-ray and the UV creates a powerful investigative tool. Here we give examples from both low and high redshift.

We have incorporated the description of the X-ray properties of Active Galactic Nuclei (AGNs) into a semi-analytic model of galaxy formation, adopting physically motivated scaling laws for accretion triggered by galaxy encounters. Our model…

We perform a detailed investigation of moderate-to-high quality X-ray spectra of ten of the most luminous active galactic nuclei (AGNs) known at z>4 (up to z~6.28). This study includes five new XMM observations and five archived X-ray…

We have used very deep XMM-Newton observations of the Chandra Deep Field-South to examine the spectral properties of the faint active galactic nucleus (AGN) population. Crucially, redshift measurements are available for 84% (259/309) of the…

The optical classification of a Seyfert galaxy and whether it is considered X-ray absorbed are often used interchangeably. But there are many borderline cases and also numerous examples where the optical and X-ray classifications appear to…

X-ray surveys have revealed a new class of active galactic nuclei (AGN) with a very low observed fraction of scattered soft X-rays, f_scat < 0.5%. Based on X-ray modeling these "X-ray new-type", or low observed X-ray scattering…

A fraction of active galactic nuclei do not show the classical Seyfert-type signatures in their optical spectra, i.e. they are optically "elusive". X-ray observations are an optimal tool to identify this class of objects. We combine new…

We present the results of optical spectroscopic identifications of a bright subsample of 2-10keV hard X-ray selected sources from the ASCA Medium Sensitivity Survey in the northern sky. The flux limit of the subsample is 3*10^-13 erg s^-1…

Multiwavelength identification of AGN is crucial not only to obtain a more complete census, but also to learn about the physical state of the nuclear activity (obscuration, efficiency, etc.). A panchromatic strategy plays an especially…