- ID:
- ivo://CDS.VizieR/J/A+A/530/A42
- Title:
- X-ray properties of AGNs in XBS
- Short Name:
- J/A+A/530/A42
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- X-ray surveys are a key instrument in the study of active galactic nuclei (AGN). Thanks to their penetrating ability, X-rays are able to map the innermost regions close to the central super massive black hole (SMBH) as well as to detect and characterize its emission up to high redshift. We present here a detailed X-ray spectral analysis of the AGN belonging to the XMM-Newton bright survey (XBS). The XBS is composed of two flux-limited samples selected in the complementary 0.5-4.5 and 4.5-7.5keV energy bands and comprising more than 300 AGN up to redshift ~2.4. We performed an X-ray analysis following two different approaches: by analyzing individually each AGN X-ray spectrum and by constructing average spectra for different AGN types.
Number of results to display per page
Search Results
- ID:
- ivo://CDS.VizieR/J/MNRAS/504/5556
- Title:
- X-ray properties of 26 high-luminosity quasars
- Short Name:
- J/MNRAS/504/5556
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present an investigation of the interdependence of the optical-to-X-ray spectral slope (aox), the HeII equivalent-width (EW), and the monochromatic luminosity at 2500{AA} (L2500). The values of {alpha}_ox_ and HeII EW are indicators of the strength/shape of the quasar ionizing continuum, from the ultraviolet (UV; 1500-2500{AA}), through the extreme ultraviolet (EUV;300-50{AA}), to the X-ray (2keV) regime. For this investigation, we measure the HeII EW of 206 radio-quiet quasars devoid of broad absorption lines that have high-quality spectral observations of the UV and 2keV X-rays. The sample spans wide redshift (z~0.13-3.5) and luminosity (logL_2500_~29.2-32.5erg/s/Hz) ranges. We recover the well-known {alpha}_ox_-L_2500_ and HeII EW-L_2500_ anti-correlations, and we find a similarly strong correlation between {alpha}_ox_ and HeII EW, and thus the overall spectral shape from the UV, through the EUV, to the X-ray regime is largely set by luminosity. A significant {alpha}_ox_-HeII EW correlation remains after removing the contribution of L_2500_ from each quantity, and thus the emission in the EUV and the X-rays are also directly tied. This set of relations is surprising, since the UV, EUV, and X-ray emission are expected to be formed in three physically distinct regions. Our results indicate the presence of a redshift-independent physical mechanism that couples the continuum emission from these three different regions, and thus controls the overall continuum shape from the UV to the X-ray regime.
- ID:
- ivo://CDS.VizieR/J/ApJ/713/L11
- Title:
- X-ray properties of Seyfert 1 galaxies
- Short Name:
- J/ApJ/713/L11
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We use publicly available XMM-Newton data to systematically compare the hard X-ray photon indices, {Gamma}_2-10keV_, and the iron K{alpha} emission lines of narrow- and broad-line Seyfert 1 (NLS1 and BLS1) galaxies. We compile a flux-limited (f_2-10keV_>=1x10^-12^erg/s/cm^2^) sample including 114 radio-quiet objects, with the 2-10keV luminosity ranging from 10^41^ to 10^45^erg/s. 86 out of these 114 AGNs are included in the CAIXA catalogue (Bianchi et al. 2009, Cat. J/A+A/495/421). The redshift range of the present sample is z<0.37, with only seven objects having z>0.2.
- ID:
- ivo://CDS.VizieR/J/A+A/350/805
- Title:
- X-ray selected ROSAT AGN spectra
- Short Name:
- J/A+A/350/805
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the emission line properties of a sample of 76 bright soft X-ray selected ROSAT Active Galactic Nuclei. All optical counterparts are Seyfert 1 galaxies with rather narrow permitted lines, strong optical FeII line blends, and weak forbidden lines. By selection, they also have steep soft X-ray spectra when compared with typical Seyfert 1 galaxies. We discuss possible origins of these peculiar trends employing detailed correlation analyses, including a Principal Component Analysis. The optical spectra are presented in the Appendix.
- ID:
- ivo://CDS.VizieR/J/ApJS/212/9
- Title:
- X-ray sources in Hickson Compact Groups
- Short Name:
- J/ApJS/212/9
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present Chandra X-ray point source catalogs for 9 Hickson Compact Groups (HCGs, 37 galaxies) at distances of 34-89Mpc. We perform detailed X-ray point source detection and photometry and interpret the point source population by means of simulated hardness ratios. We thus estimate X-ray luminosities (L_X_) for all sources, most of which are too weak for reliable spectral fitting. For all sources, we provide catalogs with counts, count rates, power-law indices ({Gamma}), hardness ratios, and L_X_, in the full (0.5-8.0keV), soft (0.5-2.0keV), and hard (2.0-8.0keV) bands. We use optical emission-line ratios from the literature to re-classify 24 galaxies as star-forming, accreting onto a supermassive black hole (AGNs), transition objects, or low-ionization nuclear emission regions. Two-thirds of our galaxies have nuclear X-ray sources with Swift/UVOT counterparts. Two nuclei have L_X,0.5-8.0keV_>10^42^erg/s, are strong multi-wavelength active galactic nuclei (AGNs), and follow the known {alpha}_OX_-{nu}L_{nu}(nearUV)_ correlation for strong AGNs. Otherwise, most nuclei are X-ray faint, consistent with either a low-luminosity AGN or a nuclear X-ray binary population, and fall in the "non-AGN locus" in {alpha}_OX_-{nu}L_{nu}(nearUV)_ space, which also hosts other normal galaxies. Our results suggest that HCG X-ray nuclei in high specific star formation rate spiral galaxies are likely dominated by star formation, while those with low specific star formation rates in earlier types likely harbor a weak AGN. The AGN fraction in HCG galaxies with M_R_<=-20 and L_X,0.5-8.0keV_>=10^41^erg/s is 0.08_-0.01_^+0.35^, somewhat higher than the ~5% fraction in galaxy clusters.
- ID:
- ivo://CDS.VizieR/J/MNRAS/446/911
- Title:
- X-ray sources in the AKARI NEP deep field
- Short Name:
- J/MNRAS/446/911
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present data products from the 300ks Chandra survey in the AKARI North Ecliptic Pole (NEP) deep field. This field has a unique set of 9-band infrared photometry covering 2-24 micron from the AKARI Infrared Camera, including mid-infrared (MIR) bands not covered by Spitzer. The survey is one of the deepest ever achieved at ~15 micron, and is by far the widest among those with similar depths in the MIR. This makes this field unique for the MIR-selection of AGN at z~1. We design a source detection procedure, which performs joint Maximum Likelihood PSF fits on all of our 15 mosaicked Chandra pointings covering an area of 0.34 square degree. The procedure has been highly optimized and tested by simulations. We provide a point source catalog with photometry and Bayesian-based 90 per cent confidence upper limits in the 0.5-7, 0.5-2, 2-7, 2-4, and 4-7keV bands. The catalog contains 457 X-ray sources and the spurious fraction is estimated to be ~1.7 per cent. Sensitivity and 90 per cent confidence upper flux limits maps in all bands are provided as well. We search for optical MIR counterparts in the central 0.25 square degree, where deep Subaru Suprime-Cam multiband images exist. Among the 377 X-ray sources detected there, ~80 per cent have optical counterparts and ~60 per cent also have AKARI mid-IR counterparts. We cross-match our X-ray sources with MIR-selected AGN from Hanami et al. Around 30 per cent of all AGN that have MID-IR SEDs purely explainable by AGN activity are strong Compton-thick AGN candidates.
- ID:
- ivo://CDS.VizieR/J/ApJ/874/54
- Title:
- X-ray sources in the USS 1558-003 protocluster
- Short Name:
- J/ApJ/874/54
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The incidence of active galactic nuclei (AGNs) within the local environment is a potentially valuable probe of the mechanisms that trigger and provide fuel for accretion onto supermassive black holes. While the correlation between AGN fraction and environment has been well-studied in the local universe, AGN fractions have been measured for relatively few dense environments at high redshift. In this paper, we present a measurement of the X-ray AGN fraction in the USS 1558-003 protocluster associated with the z=2.53 radio galaxy 4C-00.62. Our measurement is based on a 100-ks Chandra observation, follow-up spectroscopy from the Multi-Object Double Spectrograph on the Large Binocular Telescope, and broad and narrowband photometry. These data are sensitive to AGNs more luminous than L_X_>2x10^43^erg/s in the rest-frame hard X-ray band (2-10keV). We have identified two X-ray AGNs at the redshift of USS 1558-003, one of which is the radio galaxy. We have determined that 2.0_-1.3_^+2.6^% of the H{alpha} emitters in the protocluster are X-ray AGNs. Unlike most other high-redshift cluster progenitors studied with similar techniques, USS1558-003 does not have a significantly higher fraction of AGNs than field galaxies at similar redshifts. This lower AGN fraction is inconsistent with the expectation that the higher gas fractions at high redshift, combined with the high galaxy densities and modest relative velocities in protoclusters, should produce higher AGN fractions.
- ID:
- ivo://CDS.VizieR/J/MNRAS/443/1999
- Title:
- X-ray spectral analysis of AGNs
- Short Name:
- J/MNRAS/443/1999
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the results from an X-ray spectral analysis of active galactic nuclei (AGN) in the Chandra Deep Field-South, All-wavelength Extended Groth-strip International Survey (AEGIS)-Deep X-ray survey (XD) and Chandra-Cosmic Evolution Surveys (COSMOS), focusing on the identification and characterization of the most heavily obscured, Compton thick (CT, NH>10^24^cm^-2^) sources. Our sample is comprised of 3184 X-ray selected extragalactic sources, which has a high rate of redshift completeness (96.6 per cent), and includes additional spectroscopic redshifts and improved photometric redshifts over previous studies. We use spectral models designed for heavily obscured AGN which self-consistently include all major spectral signatures of heavy absorption. We validate our spectral fitting method through simulations, identify CT sources not selected through this method using X-ray colours and take considerations for the constraints on NH given the low count nature of many of our sources. After these considerations, we identify a total of 100 CT AGN with best-fitting NH >10^24^cm^-2^ and NH constrained to be above 10^23.5^cm^-2^ at 90 per cent confidence. These sources cover an intrinsic 2-10keV X-ray luminosity range of 10^42^-3x10^45^erg/s and a redshift range of z=0.1-4. This sample will enable characterization of these heavily obscured AGN across cosmic time and to ascertain their cosmological significance. These survey fields are sites of extensive multiwavelength coverage, including near-infrared Cosmic Assembly Near-infrared Deep Extragalactic Legacy Survey (CANDELS) data and far-infrared Herschel data, enabling forthcoming investigations into the host properties of CT AGN. Furthermore, by using the torus models to test different covering factor scenarios, and by investigating the inclusion of the soft scattered emission, we find evidence that the covering factor of the obscuring material decreases with LX for all redshifts, consistent with the receding torus model, and that this factor increases with redshift, consistent with an increase in the obscured fraction towards higher redshifts. The strong relationship between the parameters of obscuration and LX points towards an origin intrinsic to the AGN; however, the increase of the covering factor with redshift may point towards contributions to the obscuration by the host galaxy. We make NH, {GAMMA} (with uncertainties), observed X-ray fluxes and intrinsic 2-10keV luminosities for all sources analysed in this work publicly available in an online catalogue.
- ID:
- ivo://CDS.VizieR/J/ApJ/763/111
- Title:
- X-ray spectral analysis of Swift/BAT AGNs
- Short Name:
- J/ApJ/763/111
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a detailed X-ray spectral analysis of the non-beamed, hard X-ray selected active galactic nuclei (AGNs) in the northern Galactic cap of the 58 month Swift Burst Alert Telescope (Swift/BAT) catalog, consisting of 100 AGNs with b>50{deg}. This sky area has excellent potential for further dedicated study due to a wide range of multi-wavelength data that are already available, and we propose it as a low-redshift analog to the "deep field" observations of AGNs at higher redshifts (e.g., CDFN/S, COSMOS, Lockman Hole). We present distributions of luminosity, absorbing column density, and other key quantities for the catalog. We use a consistent approach to fit new and archival X-ray data gathered from XMM-Newton, Swift/XRT, ASCA, and Swift/BAT. We probe to deeper redshifts than the 9 month BAT catalog (<z>=0.043 compared to <z>=0.03 for the 9 month catalog), and uncover a broader absorbing column density distribution. The fraction of obscured (logN_H_>=22) objects in the sample is ~60%, and 43%-56% of the sample exhibits "complex" 0.4-10keV spectra. We present the average 1-10keV spectrum for the sample, which reproduces the 1-10keV X-ray background slope as found for the brighter 9 month BAT AGN sample.
- ID:
- ivo://CDS.VizieR/J/ApJ/865/43
- Title:
- X-ray stacking analysis of Chandra-COSMOS gal.
- Short Name:
- J/ApJ/865/43
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present an X-ray stacking analysis of ~75000 star-forming galaxies between 0.1<z<5.0 using the Chandra COSMOS-Legacy survey to study the X-ray emission of low-luminosity active galactic nuclei (AGN) and its connection to host galaxy properties. The stacks at z<0.9 have luminosity limits as low as 10^40^-10^41^erg/s, a regime in which X-ray binaries (XRBs) can dominate the X-ray emission. Comparing the measured luminosities to established XRB scaling relations, we find that the redshift evolution of the luminosity per star formation rate (SFR) of XRBs depends sensitively on the assumed obscuration and may be weaker than previously found. The XRB scaling relation based on stacks from the Chandra Deep Field South overestimates the XRB contribution to the COSMOS high specific SFR stacks, possibly due to a bias affecting the CDF-S stacks because of their small galaxy samples. After subtracting the estimated XRB contribution from the stacks, we find that most stacks at z>1.3 exhibit a significant X-ray excess indicating nuclear emission. The AGN emission is strongly correlated with stellar mass but does not exhibit an additional correlation with SFR. The hardness ratios of the high-redshift stacks indicate that the AGN are substantially obscured (N_H_~10^23^cm^-2^). These obscured AGN are not identified by IRAC color selection and have L_X_~10^41^-10^43^erg/s, consistent with accretion at an Eddington rate of ~10^-3^ onto 10^7^-10^8^M_{sun}_ black holes. Combining our results with other X-ray studies suggests that AGN obscuration depends on stellar mass and an additional variable, possibly the Eddington rate.
