- ID:
- ivo://CDS.VizieR/J/MNRAS/454/3722
- Title:
- AGN in nearby low-mass galaxies
- Short Name:
- J/MNRAS/454/3722
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We investigated AGN activity in low-mass galaxies, an important regime that can shed light on to black hole (BH) formation and evolution, and their interaction with their host galaxies. We identified 336 AGN candidates from a parent sample of ~48000 nearby low-mass galaxies (M*<=10^9.5^M_{sun}_, z<0.1) in the Sloan Digital Sky Survey. We selected the AGN using the classical BPT diagram, a similar optical emission line diagnostic based on the HeII {lambda}4686 line, and mid-IR colour cuts. Different criteria select host galaxies with different physical properties such as stellar mass and optical colour and only 3 out of 336 sources fulfil all three criteria. This could be in part due to selection biases. The resulting AGN fraction of ~0.7 percent is at least one order of magnitude below the one estimated for more massive galaxies. At optical wavelengths, the HeII-based AGN selection appears to be more sensitive to AGN hosted in star-forming galaxies than the classical BPT diagram, at least in the low-mass regime. The archival X-ray and radio data available for some of the AGN candidates seem to confirm their AGN nature, but follow-up observations are needed to confirm the AGN nature of the rest of the sample, especially in the case of mid-IR selection. Our sample will be important for future follow-up studies aiming to understand the relation between BHs and host galaxies in the low-mass regime.
Number of results to display per page
Search Results
- ID:
- ivo://CDS.VizieR/J/MNRAS/380/1467
- Title:
- AGN in supercluster A901/2
- Short Name:
- J/MNRAS/380/1467
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present XMM data for the supercluster A901/2, at z~0.17, which is combined with deep imaging and 17-band photometric redshifts (from the COMBO-17 survey), two degree field (2dF) spectra and Spitzer 24um data, to identify active galactic nuclei (AGN) in the supercluster. The 90ks XMM image contains 139 point sources, of which 11 are identified as supercluster AGN with LX(0.5-7.5keV)>1.7x10^41^erg/cm^2^/s. The host galaxies have M_R_<-20 and only two of eight sources with spectra could have been identified as AGN by the detected optical emission lines. Using a large sample of 795 supercluster galaxies, we define control samples of massive galaxies with no detected AGN. The local environments of the AGN and control samples differ at >~98 per cent significance. The AGN host galaxies lie predominantly in areas of moderate projected galaxy density and with more local blue galaxies than the control sample, with the exception of one very bright type I AGN very near the centre of a cluster. These environments are similar to, but not limited to, cluster outskirts and blue groups. Despite the large number of potential host galaxies, no AGN are found in regions with the highest galaxy density (excluding some cluster cores where emission from the intra-cluster medium obscures moderate luminosity AGN). AGN are also absent from the areas with lowest galaxy density. We conclude that the prevalence of cluster AGN is linked to their environment.
- ID:
- ivo://CDS.VizieR/J/AJ/124/3465
- Title:
- AGN in the KISS-RASS sample
- Short Name:
- J/AJ/124/3465
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a study of the X-ray properties of a volume-limited sample of optically selected emission-line galaxies. The sample is derived from a correlation between the KPNO International Spectroscopic Survey (KISS), an H{alpha}-elected objective-prism survey of active galactic nuclei (AGNs) and starbursting galaxies, and the ROSAT All-Sky Survey (RASS). After elimination of all spurious matches, we identify 18 ROSAT-detected X-ray sources within the KISS sample in the 0.1-2.4keV band.
- ID:
- ivo://CDS.VizieR/J/A+A/487/119
- Title:
- AGN in XMM-Newton Hard Bright Survey
- Short Name:
- J/A+A/487/119
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We investigate here the X-ray luminosity function (XLF) of absorbed (N_H_ between 4x10^21^ and 10^24^cm^-2^) and unabsorbed (N_H_<4x10^21^cm^-2^) AGN, the fraction of absorbed AGN as a function of L_X_ (and z), the intrinsic N_H_ distribution of the AGN population, and the XLF of Compton thick (N_H>10^24^cm^-2^) AGN. To carry out this investigation, we have used the XMM-Newton Hard Bright Serendipitous Sample (HBSS), a complete sample of bright X-ray sources (f_x_>~7x10^-14^erg/cm^2^/s) at high galactic latitude (|b|>20{deg}) selected in the 4.5-7.5keV energy band. The HBSS sample is now almost completely identified (97% spectroscopic identifications) and it can be safely used for a statistical investigation. The HBSS contains 62 AGN out of which 40 are unabsorbed (or marginally absorbed; N_H_<4x10^21^cm^-2^) and 22 are absorbed (N_H_ between 4x10^21^ and ~10^24^cm^-2^).
- ID:
- ivo://CDS.VizieR/J/AJ/130/1418
- Title:
- AGN jet kinematics
- Short Name:
- J/AJ/130/1418
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present total and polarized intensity images of 15 active galactic nuclei obtained with the Very Long Baseline Array at 7mm (43GHz) wavelength at 17 epochs from 1998 March to 2001 April. At some epochs the images are accompanied by nearly simultaneous polarization measurements at 3mm (86GHz) with the Berkeley-Illinois-Maryland Association (BIMA) array (Hat Creek, California), 1.35/0.85mm (230/350GHz) with the James Clerk Maxwell Telescope (JCMT; using SCUBA and its polarimeter, and at the Steward Observatory 1.5m telescope (Mount Lemmon, Arizona) with the Two-Holer Polarimeter/Photometer over an effective wavelength range of ~6000-7000{AA}. Here we analyze the 7mm images to define the properties of the jets of two radio galaxies, five BL Lac objects, and eight quasars on angular scales >~0.1mas. We determine the apparent velocities of 106 features in the jets.
- ID:
- ivo://CDS.VizieR/J/AZh/93/605
- Title:
- AGN long-term variability
- Short Name:
- J/AZh/93/605
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Abstract-A complete sample of 104 bright active galactic nuclei (AGNs) from the "Planck" catalog (early results) were observed at 36.8GHz with the 22-m radio telescope of the Crimean Astrophysical Observatory (CrAO).Variability indices of the sources at this frequency were determined based on data from theWMAP space observatory, theMetsahovi RadioObservatory (Finland), and the CrimeanAstrophysical Observatory. New observational results confirm that the variability of these AGNs is stronger in the millimeter than at other radio wavelengths. The variability indices probably change as a result of the systematic decrease in the AGN flux densities in the transition to the infrared. Some radio sources demonstrate significant flux-density variations, including decreases, which sometimes cause them to fall out of the analysed sample. The change of the variability index in the millimeter is consistent with the suggestion that this variability is due to intrinsic processes in binary supermassive black holes at an evolutionary stage close to coalescence. All 104 of the sources studied are well known objects that are included in various radio catalogs and have flux densities exceeding 1Jy at 36.8GHz.
- ID:
- ivo://CDS.VizieR/J/ApJ/790/54
- Title:
- AGN models according to a UV to Mid-IR study
- Short Name:
- J/ApJ/790/54
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We classify the spectral energy distributions (SEDs) of 431,038 sources in the 9 deg^2^ Bootes field of the NOAO Deep Wide-Field Survey (NDWFS). There are up to 17 bands of data available per source, including ultraviolet (GALEX), optical (NDWFS), near-IR (NEWFIRM), and mid-infrared (IRAC and MIPS) data, as well as spectroscopic redshifts for ~20,000 objects, primarily from the AGN and Galaxy Evolution Survey. We fit galaxy, active galactic nucleus (AGN), stellar, and brown dwarf templates to the observed SEDs, which yield spectral classes for the Galactic sources and photometric redshifts and galaxy/AGN luminosities for the extragalactic sources. The photometric redshift precision of the galaxy and AGN samples are {sigma}/(1 + z) = 0.040 and {sigma}/(1 + z) = 0.169, respectively, with the worst 5% outliers excluded. On the basis of the {Chi}_{nu}^2^ of the SED fit for each SED model, we are able to distinguish between Galactic and extragalactic sources for sources brighter than I = 23.5 mag. We compare the SED fits for a galaxy-only model and a galaxy-AGN model. Using known X-ray and spectroscopic AGN samples, we confirm that SED fitting can be successfully used as a method to identify large populations of AGNs, including spatially resolved AGNs with significant contributions from the host galaxy and objects with the emission line ratios of "composite" spectra. We also use our results to compare with the X-ray, mid-IR, optical color, and emission line ratio selection techniques. For an F-ratio threshold of F > 10, we find 16,266 AGN candidates brighter than I = 23.5 mag and a surface density of ~1900 AGN deg^-2^.
- ID:
- ivo://CDS.VizieR/J/other/APh/26.282
- Title:
- AGN neutrino source candidates
- Short Name:
- J/other/APh/26.2
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The sensitivity of a search for sources of TeV neutrinos can be improved by grouping potential sources together into generic classes in a procedure that is known as source stacking. In this paper, we define catalogs of Active Galactic Nuclei (AGN) and use them to perform a source stacking analysis. The grouping of AGN into classes is done in two steps: first, AGN classes are defined, then, sources to be stacked are selected assuming that a potential neutrino flux is linearly correlated with the photon luminosity in a certain energy band (radio, IR, optical, keV, GeV, TeV). Lacking any secure detailed knowledge on neutrino production in AGN, this correlation is motivated by hadronic AGN models, as briefly reviewed in this paper. The source stacking search for neutrinos from generic AGN classes is illustrated using the data collected by the AMANDA-II high-energy neutrino detector during the year 2000. No significant excess for any of the suggested groups was found.
- ID:
- ivo://CDS.VizieR/J/A+A/596/A64
- Title:
- 4 AGN optical spectra
- Short Name:
- J/A+A/596/A64
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Intermediate-Mass Black Holes (IMBHs) are thought to be the seeds of early Supermassive Black Holes (SMBHs). While >~100 IMBH and small SMBH candidates have been identified in recent years, few have been robustly confirmed to date, leaving their number density in considerable doubt. Placing firmer constraints both on the methods used to identify and confirm IMBHs/SMBHs, as well as characterizing the range of host environments that IMBHs/SMBHs likely inhabit is therefore of considerable interest and importance. Additionally, finding significant numbers of IMBHs in metal-poor systems would be particularly intriguing, since such systems may represent local analogs of primordial galaxies, and therefore could provide clues of early accretion processes. Here we study in detail several candidate Active Galactic Nuclei (AGN) found in metal-poor hosts. We utilize new X-ray and optical observations to characterize these metal-poor AGN candidates and compare them against known AGN luminosity relations and well-characterized IMBH/SMBH samples.
- ID:
- ivo://CDS.VizieR/J/A+A/529/A135
- Title:
- AGN Opt/IR properties in Lockman Hole
- Short Name:
- J/A+A/529/A135
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the observed-frame optical, near-, and mid-infrared properties of X-ray-selected active galactic nuclei (AGN) in the Lockman Hole. Using a likelihood ratio method on optical, near-infrared or mid-infrared catalogues, we assigned counterparts to 401 out of the 409 X-ray sources of the XMM-Newton catalogue. Accurate photometry was collected for all the sources from U to 24um. We used X-ray and optical criteria to remove any normal galaxies, galactic stars, or X-ray clusters among them and studied the multi-wavelength properties of the remaining 377 AGN. We used a mid-IR colour-colour selection to understand the AGN contribution to the optical and infrared emission.
