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71. AGNs with composite spectra. II.
ID:
ivo://CDS.VizieR/J/A+AS/135/437
Title:
AGNs with composite spectra. II.
Short Name:
J/A+AS/135/437
Date:
21 Oct 2021
Publisher:
CDS
Description:
We have compiled from the literature 88 emission-line galaxies for which the published line-ratios give indication of a "transition spectrum"; selected objects are located north of {delta}~-20{deg}, are brighter than B=17 and have z<0.1. We have observed 53 of these galaxies with the spectrograph CARELEC, attached to the OHP 1.93m telescope. The observations were carried out during several runs in May, June and July 1996 and January, March, October and November 1997. The journal of observations is given in Table 5. The spectra (R~1800) were analysed in terms of Gaussians to search for the presence of multiple line-components, coming from kinematically and spatially distinct regions - "composite spectra". The results of the fitting analysis are given in Table 6.
72. AGNs with double-peaked [OIII] lines
ID:
ivo://CDS.VizieR/J/ApJ/705/L76
Title:
AGNs with double-peaked [OIII] lines
Short Name:
J/ApJ/705/L76
Date:
21 Oct 2021
Publisher:
CDS
Description:
Double-peaked [OIII] profiles in active galactic nuclei (AGNs) may provide evidence for the existence of dual AGNs, but a good diagnostic for selecting them is currently lacking. Starting from ~7000 active galaxies in Sloan Digital Sky Survey DR7, we assemble a sample of 87 type 2 AGNs with double-peaked [OIII] profiles. The nuclear obscuration in the type 2 AGNs allows us to determine redshifts of host galaxies through stellar absorption lines. We typically find that one peak is redshifted and another is blueshifted relative to the host galaxy. We find a strong correlation between the ratios of the shifts and the double peak fluxes. The correlation can be naturally explained by the Keplerian relation predicted by models of co-rotating dual AGNs. The current sample statistically favors that most of the [OIII] double-peaked sources are dual AGNs and disfavors other explanations, such as rotating disk and outflows. These dual AGNs have a separation distance at ~1kpc scale, showing an intermediate phase of merging systems. The appearance of dual AGNs is about ~10^-2^, impacting on the current observational deficit of binary supermassive black holes with a probability of ~10^-4^ (Boroson & Lauer, 2009Natur.458...53B).
73. AGN Torus model comparison of AGN in the CDFS
ID:
ivo://CDS.VizieR/J/A+A/564/A125
Title:
AGN Torus model comparison of AGN in the CDFS
Short Name:
J/A+A/564/A125
Date:
21 Oct 2021
Publisher:
CDS
Description:
Active Galactic Nuclei are known to have complex X-ray spectra that depend on both the properties of the accreting supermassive black hole (e.g. mass, accretion rate) and the distribution of obscuring material in its vicinity (i.e. the "torus"). Often however, simple and even unphysical models are adopted to represent the X-ray spectra of AGN, which do not capture the complexity and diversity of the observations. In the case of blank field surveys in particular, this should have an impact on e.g. the determination of the AGN luminosity function, the inferred accretion history of the Universe and also on our understanding of the relation between AGN and their host galaxies. We develop a Bayesian framework for model comparison and parameter estimation of X-ray spectra. We take into account uncertainties associated with both the Poisson nature of X-ray data and the determination of source redshift using photometric methods. We also demonstrate how Bayesian model comparison can be used to select among ten different physically motivated X-ray spectral models the one that provides a better representation of the observations. This methodology is applied to X-ray AGN in the 4 Ms Chandra Deep Field South. For the ~350 AGN in that field, our analysis identifies four components needed to represent the diversity of the observed X-ray spectra: (1) an intrinsic power law, (2) a cold obscurer which reprocesses the radiation due to photo-electric absorption, Compton scattering and Fe-K fluorescence, (3) an unabsorbed power law associated with Thomson scattering off ionised clouds, and (4) Compton reflection, most noticeable from a stronger-than-expected Fe-K line. Simpler models, such as a photo-electrically absorbed power law with a Thomson scattering component, are ruled out with decisive evidence (B>100). We also find that ignoring the Thomson scattering component results in underestimation of the inferred column density, N_H_, of the obscurer. Regarding the geometry of the obscurer, there is strong evidence against both a completely closed (e.g. sphere), or entirely open (e.g. blob of material along the line of sight), toroidal geometry in favour of an intermediate case. Despite the use of low-count spectra, our methodology is able to draw strong inferences on the geometry of the torus. Simpler models are ruled out in favour of a geometrically extended structure with significant Compton scattering. We confirm the presence of a soft component, possibly associated with Thomson scattering off ionised clouds in the opening angle of the torus. The additional Compton reflection required by data over that predicted by toroidal geometry models, may be a sign of a density gradient in the torus or reflection off the accretion disk. Finally, we release a catalogue of AGN in the CDFS with estimated parameters such as the accretion luminosity in the 2-10keV band and the column density, N_H_, of the obscurer.
74. AGN torus models. SED library
ID:
ivo://CDS.VizieR/J/A+A/583/A120
Title:
AGN torus models. SED library
Short Name:
J/A+A/583/A120
Date:
21 Oct 2021
Publisher:
CDS
Description:
We assume that dust near active galactic nuclei (AGNs) is distributed in a torus-like geometry, which can be described as a clumpy medium or a homogeneous disk, or as a combination of the two (i.e. a two-phase medium). The dust particles considered are fluffy and have higher submillimeter emissivities than grains in the diffuse interstellar medium. The dust-photon interaction is treated in a fully self-consistent three-dimensional radiative transfer code. We provide an AGN library of spectral energy distributions (SEDs). Its purpose is to quickly obtain estimates of the basic parameters of the AGNs, such as the intrinsic luminosity of the central source, the viewing angle, the inner radius, the volume filling factor and optical depth of the clouds, and the optical depth of the disk midplane, and to predict the flux at yet unobserved wavelengths. The procedure is simple and consists of finding an element in the library that matches the observations. We discuss the general properties of the models and in particular the 10um silicate band. The AGN library accounts well for the observed scatter of the feature strengths and wavelengths of the peak emission. AGN extinction curves are discussed and we find that there is no direct one-to-one link between the observed extinction and the wavelength dependence of the dust cross sections. We show that objects in the library cover the observed range of mid-infrared colors of known AGNs. The validity of the approach is demonstrated by matching the SEDs of a number of representative objects: Four Seyferts and two quasars for which we present new Herschel photometry, two radio galaxies, and one hyperluminous infrared galaxy. Strikingly, for the five luminous objects we find that pure AGN models fit the SED without needing to postulate starburst activity.
75. AGN 2.5-11um spectroscopy
ID:
ivo://CDS.VizieR/J/A+A/357/839
Title:
AGN 2.5-11um spectroscopy
Short Name:
J/A+A/357/839
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present observations over the 2.5-11{mu}m range, with the ISOPHOT-S spectrometer and the ISOCAM imaging camera, of a sample of 57 AGNs and one non-active SB galaxy. The sample is about equally divided into type I (<=1.5; 28 sources) and type II (>1.5; 29 sources) objects.
76. AGN UV luminosity function
ID:
ivo://CDS.VizieR/J/MNRAS/488/1035
Title:
AGN UV luminosity function
Short Name:
J/MNRAS/488/1035
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present lists of more than 80000 mostly UV-optical colour-selected AGN from 12 data sets, homogenised with respect to the assumed cosmology, magnitude system, and bandpass correction (if possible). We also present the selection functions for each of the 12 data sets, similarly homogenised. The total sample spans redshifts from z=0 to 7.5. The paper presents a detailed description of the combined sample and determinations of the AGN UV luminosity function throughout this redshift range. The code for developing and analysing AGN luminosity functions is available on GitHub (https://github.com/gkulkarni/QLF). The inferred UV luminosity functions can also be used to derive the contribution of AGN to the cosmic UV background and its effect on the intergalactic medium (IGM). The GitHub repository also includes code for this. Here we also present the luminosity functions in redshift bins, luminosity function evolution models from the paper, the 912{AA} and 1450{AA} volume emissivity of AGN from z=0 to 15, and the hydrogen photoionization rate contribution by AGN in this redshift range.
77. AGN vs. host galaxy properties in COSMOS field
ID:
ivo://CDS.VizieR/J/A+A/602/A123
Title:
AGN vs. host galaxy properties in COSMOS field
Short Name:
J/A+A/602/A123
Date:
21 Oct 2021
Publisher:
CDS
Description:
The coeval AGN and galaxy evolution and the observed local relations between SMBHs and galaxy properties suggest some connection or feedback between SMBH growth and galaxy build-up. We looked for correlations between properties of X-ray detected AGN and their FIR detected host galaxies, to find quantitative evidences for this connection, highly debated in the latest years. We exploit the rich multi-wavelength data set available in the COSMOS field for a large sample (692 sources) of AGN and their hosts, in the redshift range 0.1<z<4. We use X-ray data to select AGN and determine their properties (intrinsic luminosity and nuclear obscuration), and broad-band SED fitting to derive host galaxy properties (stellar mass M* and star formation rate SFR). We find that the AGN 2-10keV luminosity (LX) and the host 8-1000um star formation luminosity (LSFIR) are significantly correlated. However, the average host LSFIR has a flat distribution in bins of AGN LX, while the average AGN LX increases in bins of host LSFIR, with logarithmic slope of ~0.7, in the redshifts range 0.4<z<1.2. We also discuss the comparison between the distribution of these two quantities and the predictions from hydro-dynamical simulations. Finally we find that the average column density (NH) shows a positive correlation with the host M*, at all redshifts, but not with the SFR (or LSFIR). This translates into a negative correlation with specific SFR. Our results are in agreement with the idea that BH accretion and SF rates are correlated, but occur with different variability time scales. The presence of a positive correlation between NH and host M* suggests that the X-ray NH is not entirely due to the circum-nuclear obscuring torus, but may also include a contribution from the host galaxy.
78. AGN with WISE. II. The NDWFS Bootes field
ID:
ivo://CDS.VizieR/J/ApJ/772/26
Title:
AGN with WISE. II. The NDWFS Bootes field
Short Name:
J/ApJ/772/26
Date:
21 Oct 2021
Publisher:
CDS
Description:
Stern et al. (2012ApJ...753...30S, Paper I) presented a study of Wide-field Infrared Survey Explorer (WISE) selection of active galactic nuclei (AGNs) in the 2deg^2^ COSMOS field, finding that a simple criterion W1-W2>=0.8 provides a highly reliable and complete AGN sample for W2<15.05, where the W1 and W2 passbands are centered at 3.4{mu}m and 4.6{mu}m, respectively. Here we extend this study using the larger 9deg^2^ NOAO Deep Wide-Field Survey Bootes field which also has considerably deeper WISE observations than the COSMOS field, and find that this simple color cut significantly loses reliability at fainter fluxes. We define a modified selection criterion combining the W1-W2 color and the W2 magnitude to provide highly reliable or highly complete AGN samples for fainter WISE sources. In particular, we define a color-magnitude cut that finds 130+/-4deg^-2^ AGN candidates for W2<17.11 with 90% reliability. Using the extensive UV through mid-IR broadband photometry available in this field, we study the spectral energy distributions of WISE AGN candidates. We find that, as expected, the WISE AGN selection can identify highly obscured AGNs, but that it is biased toward objects where the AGN dominates the bolometric luminosity output. We study the distribution of reddening in the AGN sample and discuss a formalism to account for sample incompleteness based on the step-wise maximum-likelihood method of Efstathiou et al. The resulting dust obscuration distributions depend strongly on AGN luminosity, consistent with the trend expected for a receding torus. At L_AGN_~3x10^44^erg/s, 29%+/-7% of AGNs are observed as Type 1, while at ~4x10^45^erg/s the fraction is 64%+/-13%. The distribution of obscuration values suggests that dust in the torus is present as both a diffuse medium and in optically thick clouds.
79. AGN X-ray variability in the 4Ms catalog
ID:
ivo://CDS.VizieR/J/ApJ/748/124
Title:
AGN X-ray variability in the 4Ms catalog
Short Name:
J/ApJ/748/124
Date:
21 Oct 2021
Publisher:
CDS
Description:
The 4 Ms Chandra Deep Field-South (CDF-S) and other deep X-ray surveys have been highly effective at selecting active galactic nuclei (AGNs). However, cosmologically distant low-luminosity AGNs (LLAGNs) have remained a challenge to identify due to significant contribution from the host galaxy. We identify long-term X-ray variability (~month-years, observed frame) in 20 of 92 CDF-S galaxies spanning redshifts z{approx}0.08-1.02 that do not meet other AGN selection criteria. We show that the observed variability cannot be explained by X-ray binary populations or ultraluminous X-ray sources, so the variability is most likely caused by accretion onto a supermassive black hole (SMBH). The variable galaxies are not heavily obscured in general, with a stacked effective power-law photon index of {Gamma}_stack_{approx}1.93+/-0.13, and are therefore likely LLAGNs. The LLAGNs tend to lie a factor of {approx}6-80 below the extrapolated linear variability-luminosity relation measured for luminous AGNs.
80. AKARI 2.5-5um spectra of nearby Type-1 AGNs
ID:
ivo://CDS.VizieR/J/ApJS/216/17
Title:
AKARI 2.5-5um spectra of nearby Type-1 AGNs
Short Name:
J/ApJS/216/17
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present 2.5-5.0{mu}m spectra of 83 nearby (0.002<z<0.48) and bright (K<14mag) type-1 active galactic nuclei (AGNs) taken with the Infrared Camera on board AKARI. The 2.5-5.0{mu}m spectral region contains emission lines such as Br{beta} (2.63{mu}m), Br{alpha} (4.05{mu}m), and polycyclic aromatic hydrocarbons (3.3{mu}m), which can be used for studying the black hole (BH) masses and star formation activity in the host galaxies of AGNs. The spectral region also suffers less dust extinction than in the ultra violet (UV) or optical wavelengths, which may provide an unobscured view of dusty AGNs. Our sample is selected from bright quasar surveys of Palomar-Green and SNUQSO, and AGNs with reverberation-mapped BH masses from Peterson et al. Using 11 AGNs with reliable detection of Brackett lines, we derive the Brackett-line-based BH mass estimators. We also find that the observed Brackett line ratios can be explained with the commonly adopted physical conditions of the broad line region. Moreover, we fit the hot and warm dust components of the dust torus by adding photometric data of SDSS, 2MASS, WISE, and ISO to the AKARI spectra, finding hot and warm dust temperatures of ~1100K and ~220K, respectively, rather than the commonly cited hot dust temperature of 1500K.