- ID:
- ivo://CDS.VizieR/J/A+A/618/A152
- Title:
- Abell 1795 GMRT and Chandra maps
- Short Name:
- J/A+A/618/A152
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- In this paper we analyze AGN activity signatures in the rich nearby galaxy cluster Abell 1795 aiming to confirm and characterize the long-term feedback history in the system. We combine radio observations at 610 and 235MHz from the Giant Metrewave Radio Telescope (GMRT) with 3.4Msec X-ray data from the Chandra Observatory. Extracting radial temperature profiles, as well as Xray and radio surface brightness profiles in three directions showing major morphological disturbances, we highlight the signatures of activity in the system. For the first time we observe radio emission corresponding to the NW X-ray depression, which provides evidence in favor of the classification of the depression as a cavity. We identify two other X-ray cavities situated NW and SW of the AGN. While the central radio emission corresponding to the inner cavities shows a flatter spectral index, the radio extensions associated with the farthest X-ray cavities consist of aged plasma. All observed signatures both in radio and X-ray are consistent with several consecutive episodes of AGN activity, which gave rise to the observed morphology NW and SW from the core. In the southern region, we confirm the cooling wake hypothesis for the origin of the long tail. The deep X-ray data also allows us to distinguish significant distortions in the tail's inner parts, which we attribute to the activity of the AGN.
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- ID:
- ivo://CDS.VizieR/J/A+A/649/A37
- Title:
- Abell 1775 radio images
- Short Name:
- J/A+A/649/A37
- Date:
- 22 Feb 2022
- Publisher:
- CDS
- Description:
- Thermal gas in the center of galaxy clusters can show substantial motions that generate surface brightness and temperature discontinuities known as cold fronts. The motions may be triggered by minor or o-axis mergers that preserve the cool-core of the system. The dynamics of the thermal gas can also generate radio emission from the intra-cluster medium (ICM) and impact the evolution of clusters radio sources. We study the central region of Abell 1775, a system in an ambiguous dynamical state at z=0.072 which is known to host an extended head-tail radio galaxy, with the aim of investigating the connection between thermal and non-thermal components in its center. We made use of a deep (100ks) Chandra observation accompanied by LOFAR 144MHz, GMRT 235MHz and 610MHz, and VLA 1.4GHz radio data. We find a spiral-like pattern in the X-ray surface brightness that is mirrored in the temperature and pseudo-entropy maps. Additionally, we characterize an arc-shaped cold front in the ICM. We interpret these features in the context of a slingshot gas tail scenario. The structure of the head-tail radio galaxy "breaks" at the position of the cold front, showing an extension that is detected only at low frequencies, likely due to its steep and curved spectrum. We speculate that particle re-acceleration is occurring in the outer region of this tail, that in total covers a projected size of 800kpc. We also report the discovery of revived fossil plasma with ultra-steep spectrum radio emission in the cluster core together with a central diffuse radio source that is bounded by the arc-shaped cold front. The results reported in this work demonstrate the interplay between thermal and non-thermal components in the cluster center and the presence of ongoing particle re-acceleration in the ICM on different scales.
- ID:
- ivo://CDS.VizieR/J/MNRAS/277/1477
- Title:
- A catalogue of BL Lacertae objects
- Short Name:
- J/MNRAS/277/1477
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a catalogue of 233 BL Lacertae objects compiled through an extensive bibliographic search updated to mid-1995. A large fraction of the sources listed in the catalogue belongs to well-defined samples and can be used for statistical purposes. A smaller fraction consists of miscellaneous (but confirmed) BL Lacs and of objects classified as BL Lac candidates. We discuss the selection criteria of the different samples, report the discovery of two previously unnoticed BL Lacs in the Palomar-Green survey, and comment on the possible association of some of the still unidentified high galactic latitude gamma-ray (EGRET, see Thompson et al., =1995ApJS..101..259T) sources with BL Lacs. Some statistical properties of the catalogue are also briefly discussed.
- ID:
- ivo://CDS.VizieR/V/138
- Title:
- A catalogue of cross-matched radio/infrared/X-ray sources
- Short Name:
- V/138
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a catalog of cross-correlated radio, infrared and X-ray sources using a very restrictive selection criteria with an IDL-based code developed by us. The significance of the observed coincidences was evaluated through Monte Carlo simulations of synthetic sources following a well-tested protocol. We found 3320 coincident radio/X-ray sources with a high statistical significance characterized by the sum of error-weighted coordinate differences. For 997 of them, 2MASS counterparts were found. The percentage of chance coincidences is less than 1%. X-ray hardness ratios of well-known populations of objects were used to provide a crude representation of their X-ray spectrum and to make a preliminary diagnosis of the possible nature of unidentified X-ray sources. The results support the fact that the X-ray sky is largely dominated by Active Galactic Nuclei at high galactic latitudes (|b|>=10deg). At low galactic latitudes (|b|<=10deg) most of unidentified X-ray sources (~94%) lie at |b|>=2deg. This result suggests that most of the unidentified sources found toward the Milky Way plane are galactic objects. Well-known and unidentified sources were classified in different tables with their corresponding radio/infrared and X-ray properties. These tables are intended as a useful tool for researchers interested in particular identifications.
- ID:
- ivo://CDS.VizieR/J/ApJS/243/21
- Title:
- A complete sample of broad-line AGN from SDSS-DR7
- Short Name:
- J/ApJS/243/21
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- A new, complete sample of 14584 broad-line active galactic nuclei (AGNs) at z<0.35 is presented, which are uncovered homogeneously from the complete database of galaxies and quasars observed spectroscopically in the Sloan Digital Sky Survey Seventh Data Release. The stellar continuum is properly removed for each spectrum with significant host absorption line features, and careful analyses of the emission line spectra, particularly in the H{alpha} and H{beta} wavebands, are carried out. The broad Balmer emission line, particularly H{alpha}, is used to indicate the presence of an AGN. The broad H{alpha} lines have luminosities in a range of 10^38.5^-10^44.3^erg/s, and line widths (FWHMs) of 500-34000km/s. The virial black hole masses, estimated from the broad-line measurements, span a range of 10^5.1^-10^10.3^M_{sun}_, and the Eddington ratios vary from -3.3 to 1.3 in logarithmic scale. Other quantities such as multiwavelength photometric properties and flags denoting peculiar line profiles are also included in this catalog. We describe the construction of this catalog and briefly discuss its properties. The catalog is publicly available online. This homogeneously selected AGN catalog, along with the accurately measured spectral parameters, provides the most updated, largest AGN sample data, which will enable further comprehensive investigations of the properties of the AGN population in the low-redshift universe.
- ID:
- ivo://CDS.VizieR/J/other/Ap/62.147
- Title:
- Activity types of ROSAT/SDSS galaxies
- Short Name:
- J/other/Ap/62.14
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- In this study we carry out detailed spectral classification of 173 AGN candidates from the Joint HRC/BHRC sample, which is a combination of HRC (Hamburg-ROSAT Catalogue) and BHRC (Byurakan-Hamburg-ROSAT Catalogue). These objects were revealed as optical counterparts for ROSAT X-ray sources, however spectra for 173 of them are given in SDSS without definite spectral classification. We studied these 173 objects using the SDSS spectra and revealed the detailed activity types for them. Three diagnostic diagrams and direct examination of the spectra were used to have more confident classification. We also made identification of these sources in other wavelength ranges and calculated some of their parameters.
- ID:
- ivo://CDS.VizieR/J/ApJS/212/21
- Title:
- A deep Chandra ACIS survey of M83
- Short Name:
- J/ApJS/212/21
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have obtained a series of deep X-ray images of the nearby galaxy M83 using Chandra, with a total exposure of 729ks. Combining the new data with earlier archival observations totaling 61ks, we find 378 point sources within the D_25_ contour of the galaxy. We find 80 more sources, mostly background active galactic nuclei (AGNs), outside of the D_25_contour. Of the X-ray sources, 47 have been detected in a new radio survey of M83 obtained using the Australia Telescope Compact Array. Of the X-ray sources, at least 87 seem likely to be supernova remnants (SNRs), based on a combination of their properties in X-rays and at other wavelengths. We attempt to classify the point source population of M83 through a combination of spectral and temporal analysis. As part of this effort, we carry out an initial spectral analysis of the 29 brightest X-ray sources. The soft X-ray sources in the disk, many of which are SNRs, are associated with the spiral arms, while the harder X-ray sources, mostly X-ray binaries (XRBs), do not appear to be. After eliminating AGNs, foreground stars, and identified SNRs from the sample, we construct the cumulative luminosity function (CLF) of XRBs brighter than 8x10^35^erg/s. Despite M83's relatively high star formation rate, the CLF indicates that most of the XRBs in the disk are low mass XRBs.
- 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/MNRAS/473/4937
- Title:
- AllWISE ctp to ROSAT/2RXS & XMMSLEW2 catalogs
- Short Name:
- J/MNRAS/473/4937
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We release the AllWISE counterparts and Gaia matches to 106573 and 17665 X-ray sources detected in the ROSAT 2RXS and XMMSL2 surveys with |b|>15{deg}. These are the brightest X-ray sources in the sky, but their position uncertainties and the sparse multi-wavelength coverage until now rendered the identification of their counterparts a demanding task with uncertain results. New all-sky multi-wavelength surveys of sufficient depth, like AllWISE and Gaia, and a new Bayesian statistics based algorithm, NWAY, allow us, for the first time, to provide reliable counterpart associations. NWAY extends previous distance and sky density based association methods and, using one or more priors (e.g. colours, magnitudes), weights the probability that sources from two or more catalogues are simultaneously associated on the basis of their observable characteristics. Here, counterparts have been determined using a Wide-field Infrared Survey Explorer (WISE) colour-magnitude prior. A reference sample of 4524 XMM/Chandra and Swift X-ray sources demonstrates a reliability of 94.7 per cent (2RXS) and 97.4 per cent (XMMSL2). Combining our results with Chandra-COSMOS data, we propose a new separation between stars and AGN in the X-ray/WISE flux-magnitude plane, valid over six orders of magnitude. We also release the NWAY code and its user manual. NWAY was extensively tested with XMM-COSMOS data. Using two different sets of priors, we find an agreement of 96 per cent and 99 per cent with published Likelihood Ratio methods. Our results were achieved faster and without any follow-up visual inspection. With the advent of deep and wide area surveys in X-rays (e.g. SRG/eROSITA, Athena/WFI) and radio (ASKAP/EMU, LOFAR, APERTIF, etc.) NWAY will provide a powerful and reliable counterpart identification tool. See for all the options the Nway manual at https://github.com/JohannesBuchner/nway/raw/master/doc/nway-manual.pdf
- ID:
- ivo://CDS.VizieR/J/ApJS/241/37
- Title:
- 1.4 and 5GHz deep JVLA radio survey of M33
- Short Name:
- J/ApJS/241/37
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have performed new 1.4 and 5 GHz observations of the Local Group galaxy M33 with the Jansky Very Large Array. Our survey has a limiting sensitivity of 20{mu}Jy (4{sigma}) and a resolution of 5.9" (FWHM), corresponding to a spatial resolution of 24pc at 817kpc. Using a new multiresolution algorithm, we have created a catalog of 2875 sources, including 675 with well-determined spectral indices. We detect sources at the position of 319 of the X-ray sources in the Tullmann+ (2011, J/ApJS/193/31) Chandra survey of M33, the majority of which are likely to be background galaxies. The radio source coincident with M33 X-8, the nuclear source, appears to be extended. Along with numerous HII regions or portions of HII region complexes, we detect 155 of the 217 optical supernova remnants (SNRs) included in the lists of Long+, 2010, J/ApJS/187/495 and Lee & Lee, 2014, J/ApJ/793/134, making this by far the largest sample of remnants at known distances with multiwavelength coverage. The remnants show a large dispersion in the ratio of radio to X-ray luminosity at a given diameter, a result that challenges the current generation of models for synchrotron radiation evolution in SNRs.