- ID:
- ivo://CDS.VizieR/J/A+A/634/A4
- Title:
- 3 X-ray galaxy clusters radio images
- Short Name:
- J/A+A/634/A4
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- It is well established that particle acceleration by shocks and turbulence in the intra-cluster medium can produce cluster-scale synchrotron emitting sources. However, the detailed physics of these particle acceleration processes is still not well understood. One of the main open questions is the role of fossil relativistic electrons that have been deposited in the intracluster medium (ICM) by radio galaxies. These synchrotron-emitting electrons are very difficult to study as their radiative lifetime is only tens of Myr at gigahertz frequencies, and they are therefore a relatively unexplored population. Despite the typical steep radio spectrum due to synchrotron losses, these fossil electrons are barely visible even at radio frequencies well below the gigahertz level. However, when a pocket of fossil radio plasma is compressed, it boosts the visibility at sub-gigahertz frequencies, creating what are known as radio phoenices. This compression can be the result of bulk motion and shocks in the ICM due to merger activity. In this paper we demonstrate the discovery potential of low-frequency radio sky surveys to find and study revived fossil plasma sources in galaxy clusters. We used the 150MHz TIFR GMRT Sky Survey (TGSS) and the 1.4GHz NVSS sky survey to identify candidate radio phoenices. A subset of three candidates was studied in detail using deep multi-band radio observations (LOFAR and GMRT), X-ray observations (Chandra or XMM-Newton), and archival optical observations. Two of the three sources are new discoveries. Using these observations, we identified common observational properties (radio morphology, ultra-steep spectrum, X-ray luminosity, dynamical state) that will enable us to identify this class of sources more easily, and will help us to understand the physical origin of these sources.
« Previous |
981 - 990 of 990
|
Next »
Number of results to display per page
Search Results
- ID:
- ivo://CDS.VizieR/J/ApJ/892/18
- Title:
- X-ray & MIR luminosities of the GBT galaxies
- Short Name:
- J/ApJ/892/18
- Date:
- 19 Jan 2022 08:55:44
- Publisher:
- CDS
- Description:
- We present an investigation of the dependence of H_2_O maser detection rates and properties on the mid-IR active galactic nucleus (AGN) luminosity, L_AGN_, and the obscuring column density, N_H_, based on mid-IR and hard X-ray photometry. Based on spectral energy distribution fitting that allows for decomposition of the black hole accretion and star formation components in the mid-infrared, we show that the megamaser (disk maser) detection rate increases sharply for galaxies with 12{mu}m AGN luminosity L_12um_^AGN^ greater than 10^42^erg/s, from <~3% (<~2%) to ~12% (~5%). By using the ratio of the observed X-ray to mid-IR AGN luminosity as an indicator of N_H_, we also find that megamaser (disk maser) detection rates are boosted to 15% (7%) and 20% (9%) for galaxies with N_H_>=10^23^/cm^2^ and N_H_>=10^24^cm^-2^, respectively. Combining these column density cuts with a constraint for high L_12um_^AGN^ (>=10^42^erg/s) predicts further increases in the megamaser (disk maser) detection rates to 19% (8%) and 27% (14%), revealing unprecedented potential increases of the megamaser and disk maser detection rates by a factor of 7-15 relative to the current rates, depending on the chosen sample selection criteria. A noteworthy aspect of these new predictions is that the completeness rates are only compromised mildly, with the rates remaining at the level of ~95% (~50%) for sources with N_H_>=10^23^/cm^2^ (N_H_>=10^24^/cm^2^). Applying these selection methods to current X-ray AGN surveys predicts the detection of >~15 new megamaser disks.
- ID:
- ivo://CDS.VizieR/J/ApJS/226/20
- Title:
- X-ray, opt. & radio SEDs of Fermi blazars
- Short Name:
- J/ApJS/226/20
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- In this paper, multiwavelength data are compiled for a sample of 1425 Fermi blazars to calculate their spectral energy distributions (SEDs). A parabolic function, log({nu}F_{nu}_)=P_1_(log{nu}-P_2_)^2^+P_3_, is used for SED fitting. Synchrotron peak frequency (log{nu}_p_), spectral curvature (P_1_), peak flux ({nu}_p_F_{nu}p_), and integrated flux ({nu}F_{nu}_) are successfully obtained for 1392 blazars (461 flat-spectrum radio quasars [FSRQs], 620 BL Lacs [BLs], and 311 blazars of uncertain type [BCUs]; 999 sources have known redshifts). Monochromatic luminosity at radio 1.4GHz, optical R band, X-ray at 1keV and {gamma}-ray at 1GeV, peak luminosity, integrated luminosity, and effective spectral indices of radio to optical ({alpha}_RO_) and optical to X-ray ({alpha}_OX_) are calculated. The "Bayesian classification" is employed to log{nu}_p_ in the rest frame for 999 blazars with available redshift, and the results show that three components are enough to fit the log{nu}_p_ distribution; there is no ultra-high peaked subclass. Based on the three components, the subclasses of blazars using the acronyms of Abdo+ (2010, J/ApJ/716/30) are classified, and some mutual correlations are also studied.
- ID:
- ivo://CDS.VizieR/J/MNRAS/422/494
- Title:
- X-ray properties of optically selected ETGs
- Short Name:
- J/MNRAS/422/494
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We study the X-ray properties of 393 optically selected early-type galaxies (ETGs) over the redshift range of z~~0.0-1.2 in the Chandra Deep Fields (CDFs). To measure the average X-ray properties of the ETG population, we use X-ray stacking analyses with a subset of 158 passive ETGs (148 of which were individually undetected in X-ray). This ETG subset was constructed to span the redshift ranges of z=0.1-1.2 in the ~~4Ms CDF-South and ~~2Ms CDF-North and z=0.1-0.6 in the ~~250ks Extended-CDF-South where the contribution from individually undetected active galactic nuclei (AGN) is expected to be negligible in our stacking.
- ID:
- ivo://CDS.VizieR/J/A+A/434/385
- Title:
- X-ray/radio data of high energy peaked BL Lacs
- Short Name:
- J/A+A/434/385
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The fully identified complete sample including 150 extreme HBL BL Lacs is presented in Table 1 where we give the source name built with the catalog identification code SHBL (where S stands for "Sedentary" survey and HBL for High energy peaked BL Lacs) and the arcsecond precision optical coordinates of the source taken from the APM and COSMOS on-line services; we give also the RASS name, the X-ray flux (0.1-2.4keV), the radio flux (20cm, from the NVSS survey), and the optical apparent V magnitude (from APM and COSMOS) respectively; we give the redshift when available and the reference for the optical identification. In Table 2 we report properties for five bright elliptical galaxies/low luminosity HBLs in the original sample of high fX/fr sources of Paper I (Giommi et al., 1999MNRAS.310..465G). In Table 3 the 19 rejected emission line AGNs together with their properties are presented.
- ID:
- ivo://CDS.VizieR/IX/49
- Title:
- XXL Survey: First results
- Short Name:
- IX/49
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The quest for the cosmological parameters that describe our universe continues to motivate the scientific community to undertake very large survey initiatives across the electromagnetic spectrum. Over the past two decades, the Chandra and XMM-Newton observatories have sup- ported numerous studies of X-ray-selected clusters of galaxies, active galactic nuclei (AGNs), and the X-ray background. The present paper is the first in a series reporting results of the XXL-XMM survey; it comes at a time when the Planck mission results are being finalised. We present the XXL Survey, the largest XMM programme totaling some 6.9Ms to date and involving an international consortium of roughly 100 members. The XXL Survey covers two extragalactic areas of 25deg^2^ each at a point-source sensitivity of ~5x10^-15^erg/s/cm^2^ in the [0.5-2]keV band (completeness limit). The survey's main goals are to provide constraints on the dark energy equation of state from the space-time distribution of clusters of galaxies and to serve as a pathfinder for future, wide-area X-ray missions. We review science objectives, including cluster studies, AGN evolution, and large-scale structure, that are being conducted with the support of approximately 30 follow-up programmes. List of XXL papers: I. Scientific motivations - XMM-Newton observing plan - Follow-up observations and simulation programme. II. The bright cluster sample: catalogue and luminosity function. III. Luminosity-temperature relation of the bright cluster sample. IV. Mass-temperature relation of the bright cluster sample. VI. The 1000 brightest X-ray point sources. VII. A supercluster of galaxies at z = 0.43. VIII. MUSE characterisation of intracluster light in a z~0.53 cluster of galaxies. IX. Optical overdensity and radio continuum analysis of a supercluster at z=0.43. X. K-band luminosity - weak-lensing mass relation for groups and clusters of galaxies. XI. ATCA 2.1 GHz continuum observations. XII. Optical spectroscopy of X-ray-selected clusters and the frequency of AGN in superclusters. XIII. Baryon content of the bright cluster sample. XIV. AAOmega redshifts for the southern XXL field.
- ID:
- ivo://CDS.VizieR/J/ApJS/242/5
- Title:
- 40yr of geodetic/astrometric VLBI obs. of ICRF sources
- Short Name:
- J/ApJS/242/5
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Geodetic/astrometric very long baseline interferometry (VLBI) has been routinely observing using various global networks for 40yr, and it has produced more than 10 million baseline group delay, phase, and amplitude observables. These group delay observables are analyzed worldwide for geodetic and astrometric applications, for instance, to create the International Celestial Reference Frame (ICRF). The phase and amplitude observables are used in this paper, by means of closure analysis, to study intrinsic source structures and their evolution over time. The closure amplitude rms, CARMS, indicating how far away a source is from being compact in terms of morphology, is calculated for each individual source. The overall structure-effect magnitudes for 3417 ICRF radio sources are quantified. CARMS values larger than 0.3 suggest significant source structures and those larger than 0.4 indicate very extended source structures. The 30 most frequently observed sources, which constitute 40% of current geodetic VLBI observables, are studied in detail. The quality of ICRF sources for astrometry is evaluated by examining the CARMS values. It is confirmed that sources with CARMS values larger than 0.30 can contribute residual errors of about 15ps to geodetic VLBI data analysis and those with the CARMS values larger than 0.4 generally can contribute more than 20ps. We recommend CARMS values as an indicator of the astrometric quality for the ICRF sources and the continuous monitoring of the ICRF sources to update CARMS values with new VLBI observations as they become available.
- ID:
- ivo://CDS.VizieR/J/other/BSAO/45.136
- Title:
- Zelenchuk survey 9h<=RA<=12h, 0<=DE<=8{deg}
- Short Name:
- J/other/BSAO/45.
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Optical identification of Zelenchuk Survey radio sources at 3.9GHz from 9h to 12h in right ascension and between 0{deg} and 8{deg} in declination is reported in this paper. Some optical characteristics of identified radio sources are presented in the table.
- ID:
- ivo://CDS.VizieR/J/MNRAS/457/629
- Title:
- ZFOURGE catalogue of AGN candidates
- Short Name:
- J/MNRAS/457/629
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We investigate active galactic nuclei (AGN) candidates within the FourStar Galaxy Evolution Survey (ZFOURGE) to determine the impact they have on star formation in their host galaxies. We first identify a population of radio, X-ray, and infrared-selected AGN by cross-matching the deep Ks-band imaging of ZFOURGE with overlapping multiwavelength data. From this, we construct a mass-complete (log(M*/M_{sun}_)>=9.75), AGN luminosity limited sample of 235 AGN hosts over z=0.2-3.2. We compare the rest-frame U-V versus V-J (UVJ) colours and specific star formation rates (sSFRs) of the AGN hosts to a mass-matched control sample of inactive (non-AGN) galaxies. UVJ diagnostics reveal AGN tend to be hosted in a lower fraction of quiescent galaxies and a higher fraction of dusty galaxies than the control sample. Using 160{mu}m Herschel PACS data, we find the mean specific star formation rate of AGN hosts to be elevated by 0.34-/-0.07dex with respect to the control sample across all redshifts. This offset is primarily driven by infrared-selected AGN, where the mean sSFR is found to be elevated by as much as a factor of ~5. The remaining population, comprised predominantly of X-ray AGN hosts, is found mostly consistent with inactive galaxies, exhibiting only a marginal elevation. We discuss scenarios that may explain these findings and postulate that AGN are less likely to be a dominant mechanism for moderating galaxy growth via quenching than has previously been suggested.
- ID:
- ivo://CDS.VizieR/J/ApJ/854/158
- Title:
- z<0.5 PG quasars IR energy distributions
- Short Name:
- J/ApJ/854/158
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The interstellar medium is crucial to understanding the physics of active galaxies and the coevolution between supermassive black holes and their host galaxies. However, direct gas measurements are limited by sensitivity and other uncertainties. Dust provides an efficient indirect probe of the total gas. We apply this technique to a large sample of quasars, whose total gas content would be prohibitively expensive to measure. We present a comprehensive study of the full (1 to 500{mu}m) infrared spectral energy distributions of 87 redshift <0.5 quasars selected from the Palomar-Green sample, using photometric measurements from 2MASS, WISE, and Herschel, combined with Spitzer mid-infrared (5-40{mu}m) spectra. With a newly developed Bayesian Markov Chain Monte Carlo fitting method, we decompose various overlapping contributions to the integrated spectral energy distribution, including starlight, warm dust from the torus, and cooler dust on galaxy scales. This procedure yields a robust dust mass, which we use to infer the gas mass, using a gas-to-dust ratio constrained by the host galaxy stellar mass. Most (90%) quasar hosts have gas fractions similar to those of massive, star-forming galaxies, although a minority (10%) seem genuinely gas-deficient, resembling present-day massive early-type galaxies. This result indicates that "quasar mode" feedback does not occur or is ineffective in the host galaxies of low-redshift quasars. We also find that quasars can boost the interstellar radiation field and heat dust on galactic scales. This cautions against the common practice of using the far-infrared luminosity to estimate the host galaxy star formation rate.
