- ID:
- ivo://CDS.VizieR/J/A+A/363/141
- Title:
- Radio-loud galaxies in the ROSAT survey. IV.
- Short Name:
- J/A+A/363/141
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present multi-frequency radio data for 741 extragalactic sources with a 5GHz integrated flux density of >100mJy. These sources have been selected from a cross-correlation of an early ROSAT All-Sky Survey source list with a list of compact radio sources of the 5GHz Green Bank northern sky survey (RGB sample, Cat. <VIII/52>). The majority of sources were quasi-simultaneously observed with the Effelsberg 100-m telescope at 11cm, 6cm, and 2.8cm. We have determined the spectrum, size and linear polarization properties of these sources. We compare the radio data with ROSAT measurements and optical data. We find that the X-ray selected radio sources, when compared with unbiased radio source samples, are on average slightly more compact, show a higher fractional polarization, a higher absolute rotation measure (RM), and have flatter spectra. Absolute RMs are larger for steep spectrum than for flat spectrum sources and for extended than for compact sources. The average redshift increases with the radio flux density, which indicates that the X-ray selected radio sources have a larger fraction of beamed radio emission. All source characteristics of the sample are in accordance with present unification schemes for AGN, where X-ray selected sources are preferably looked at face on.
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Search Results
- ID:
- ivo://CDS.VizieR/J/A+AS/134/221
- Title:
- Radio-loud ROSAT sources near NEP
- Short Name:
- J/A+AS/134/221
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- A deep and large-area survey of the North Ecliptic Pole region was made with the ROSAT All-Sky Survey and the VLA to elucidate the population of radio-loud extragalactic objects. A region of 29.3 square degrees was surveyed with sensitivities around 5x10^-14^erg/s/cm^2^ in the soft X-ray band and 1mJy at 1.5GHz. Optical counterparts were sought on digitized Schmidt plates from POSS-I and II. Seventy-four reliable RASS-VLA sources were found. The sample is a heterogeneous mixture of Seyfert galaxies, quasars, BL Lac objects, galaxy clusters and groups containing a radio galaxy. Optical magnitudes range from B=~14 to B>22. Three results are noteworthy: (1) the bimodality in the ratio of radio to optical emission seen in optically- and X-ray-selected AGN samples is also evident in the ROSAT-VLA objects; (2) X-ray and radio selection is an effective method for locating poor galaxy clusters and groups; and (3) a considerable population of optically faint but X-ray/radio-bright objects is present. This last group may be either distant clusters with radio galaxies or "red quasars".
- ID:
- ivo://CDS.VizieR/J/ApJ/903/132
- Title:
- Radio & optical observations of supernova SN2020oi
- Short Name:
- J/ApJ/903/132
- Date:
- 15 Mar 2022
- Publisher:
- CDS
- Description:
- We report the discovery and panchromatic follow-up observations of the young Type Ic supernova (SNIc) SN2020oi in M100, a grand-design spiral galaxy at a mere distance of 14Mpc. We followed up with observations at radio, X-ray, and optical wavelengths from only a few days to several months after explosion. The optical behavior of the supernova is similar to those of other normal SNeIc. The event was not detected in the X-ray band but our radio observations revealed a bright mJy source (L_{nu}_~1.2x10^27^erg/s/Hz). Given the relatively small number of stripped envelope SNe for which radio emission is detectable, we used this opportunity to perform a detailed analysis of the comprehensive radio data set we obtained. The radio-emitting electrons initially experience a phase of inverse Compton cooling, which leads to steepening of the spectral index of the radio emission. Our analysis of the cooling frequency points to a large deviation from equipartition at the level of {epsilon}_e_/{epsilon}_B_>~200, similar to a few other cases of stripped envelope SNe. Our modeling of the radio data suggests that the shock wave driven by the SN ejecta into the circumstellar matter (CSM) is moving at ~3x10^4^km/s. Assuming a constant mass loss from the stellar progenitor, we find that the mass-loss rate is M~1.4x10^-4^M{sun}/yr for an assumed wind velocity of 1000km/s. The temporal evolution of the radio emission suggests a radial CSM density structure steeper than the standard r-2.
- ID:
- ivo://CDS.VizieR/J/other/PPMtO/17B.1
- Title:
- Radio properties of ROSAT sources
- Short Name:
- J/other/PPMtO/17
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- A cross-identification of the southern-sky objects with the ROSAT All-Sky Survey (Cat. <IX/10>) and Parkes-MIT-NRAO (PMN) Radio (5GHz) Survey (Cat. <VIII/38>) yields a list of 642 sources. Subsequential optical identification for all these coincidences has been taken to form a large sample of galaxies and Active Galactic Nuclei (AGNs). As a result, 311 (52%) were previously optically identified as extragalactic objects. The fluxes detected from X-ray, optical, and radio bands for them are compiled. This database allows an investigation on broad band energy distribution and other possible correlations among spectral indices and luminosities for various types of extragalactic objects.
- ID:
- ivo://CDS.VizieR/J/ApJ/882/69
- Title:
- Radio relic merging galaxy cluster substructures
- Short Name:
- J/ApJ/882/69
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Golovich et al. (2019, J/ApJS/240/39) present an optical imaging and spectroscopic survey of 29 radio relic merging galaxy clusters. In this paper, we study this survey to identify substructure and quantify the dynamics of the mergers. Using a combined photometric and spectroscopic approach, we identify the minimum number of substructures in each system to describe the galaxy populations and estimate the line-of-sight velocity difference between likely merging subclusters. We find that the line-of-sight velocity components of the mergers are typically small compared with the maximum 3D relative velocity (usually <1000km/s and often consistent with zero). We also compare our systems to n-body simulation analogs and estimate the viewing angle of the clean mergers in our ensemble. We find that the median system's separation vector lies within 40{deg} (17{deg}) at a 90% (50%) confidence level. This suggests that the merger axes of these systems are generally in or near the plane of the sky, matching findings in magnetohydrodynamical simulations. In 28 of the 29 systems we identify substructures in the galaxy population aligned with the radio relic(s) and presumed associated merger-induced shock. From this ensemble, we identify eight systems to include in a "gold" sample that is prime for further observation, modeling, and simulation study. Additional papers will present weak-lensing mass maps and dynamical modeling for each merging system, ultimately leading to new insight into a wide range of astrophysical phenomena at some of the largest scales in the universe.
- ID:
- ivo://CDS.VizieR/J/MNRAS/378/995
- Title:
- Radio survey of the 1H XMM/Chandra field
- Short Name:
- J/MNRAS/378/995
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the results of a deep 610-MHz survey of the 1^H^ XMM-Newton/Chandra survey area with the Giant Metre-wave Radio Telescope. The resulting maps have a resolution of ~7arcsec and an rms noise limit of 60Jy. To a 5{sigma} detection limit of 300Jy, we detect 223 sources within a survey area of 64arcmin in diameter. We compute the 610-MHz source counts and compare them to those measured at other radio wavelengths.
- ID:
- ivo://CDS.VizieR/J/MNRAS/298/692
- Title:
- Radio Survey of X-ray sources
- Short Name:
- J/MNRAS/298/692
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a radio survey of X-ray sources in the Large and Small Magellanic clouds with the Australia Telescope Compact Array at 6.3 and 3.5 cm. Specifically, we have observed the fields of five LMC and two SMC supersoft X-ray sources, the X-ray binaries LMC X-1, X-2, X-3 & X-4, the X-ray transient Nova SMC 1992, and the soft gamma-ray repeater SGR 0525-66. None of the targets are detected as point sources at their catalogued positions. In particular, the proposed supersoft jet source RXJ 0513-69 is not detected, placing constraints on its radio luminosity compared to Galactic jet sources. Limits on emission from the black hole candidate systems LMC X-1 and X-3 are consistent with the radio behaviour of persistent Galactic black hole X-ray binaries, and a previous possible radio detection of LMC X-1 is found to almost certainly be due to nearby field sources. The SNR N49 in the field of SGR 0525-66 is mapped at higher resolution than previously, but there is still no evidence for any enhanced emission or disruption of the SNR at the location of the X-ray source. No radio point sources were detected at any wavelength at the catalogued locations of the target sources. In most cases a noise level of 50 microJy or so was achieved, making the 3-sigma upper limits very stringent indeed. The noise levels for LMC X-1 and SGR 0525-66 are considerably worse, due to their locations in radio-bright regions.
- ID:
- ivo://CDS.VizieR/J/A+AS/109/267
- Title:
- Radio to X-Ray distribution of BL Lac Objects
- Short Name:
- J/A+AS/109/267
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- (no description available)
- ID:
- ivo://CDS.VizieR/J/A+A/472/805
- Title:
- Radio-X-ray sources in the HDF(N) region.
- Short Name:
- J/A+A/472/805
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- This catalogue lists the properties of 62 radio sources in the Hubble Deep Field (North) and Flanking Fields (HDFN) which were also detected by the Chandra X-ray satellite (see Alexander et al., 2003, Cat. <J/AJ/126/539>, file cdfn). This includes 55/92 sources brighter than 40uJy detected by MERLIN+VLA at 1.4GHz (see Muxlow et al., 2005, Cat. <J/MNRAS/358/1159>, Richards, 2000, Cat. <J/ApJ/533/611>); some were also detected by the VLA at 8.4GHz (Richards et al., 1998AJ....116.1039R) including 7 selected at this frequency. The cross-matching, derivation of properties and analysis are described fully in the paper. The radio data have a positional accuracy of 15 mas with respect to the ICRS (Muxlow et al., 2005, Cat. <J/MNRAS/358/1159>) but data using the GOODS HST ACS (Giavalisco et al., 2004, Cat. <II/261>) positions requires a shift of -342mas in Declination for alignment with the ICRS. We use measurements taken from the radio observations and from the literature to compile the flux densities, sizes and spectral/photon indices of the cross-matched radio+X-ray sources and their redshifts (where available), enabling us to derive the rest-frame luminosities. The 1.4-GHz detections are all resolved at 0.2-2arcsec resolution. The radio emission was classified using the source morphologies and radio spectral indices; optical and IR information was used as supporting evidence only. On this basis, starbursts outnumber radio AGN 3:1. The high-redshift starbursts have typical sizes of 5-10kpc and star formation rates of around 1000 Msun/yr, an order of magnitude more extended and intense than in the local universe. The X-ray sources are unresolved but their luminosity and spectral indices allows X-ray AGN and obscured (Type II) AGN to be identified (2004A&A...424..545P). In this way, we can distinguish between the origins of radio and X-ray emission from the same object. There is no obvious correlation between radio and X-ray luminosities nor spectral indices at z>1.3. About 70% of both the radio-selected AGN and the starburst samples were detected by Chandra. The X-ray luminosity indicates the presence of an AGN in at least half of the 45 cross-matched radio starbursts. Eleven of these are type-II AGN, of which 7 are at z>1.5. This distribution overlaps closely with the X-ray detected radio sources which were also detected by SCUBA. Almost all extended radio starbursts at z>1.3 host X-ray selected obscured AGN. The radio emission from most of these ultra-luminous objects is dominated by star formation although the highest redshift (z=4.424) source has a substantial AGN contribution. Star-formation appears to contribute less than 1/3 of their X-ray luminosity. Our results support the inferences from SCUBA and IR data, that at z>1.5, star formation is observably more extended and more copious, it is closely linked to AGN activity and it is triggered differently, compared with star formation at lower redshifts.
740. RASS AGN sample
- ID:
- ivo://CDS.VizieR/J/A+AS/139/575
- Title:
- RASS AGN sample
- Short Name:
- J/A+AS/139/575
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the first results of a program to identify the unknown bright active galactic nuclei (AGN) in the ROSAT All Sky Survey Bright Source Catalog (RASS-BSC). We have used logC+0.4R as an alternative expression for log(f_X_/f_opt_), where C is X-ray count rate and R stands for R magnitude. Then a high X-ray-to-optical flux ratio criterion has been used to select an AGN sample with 165 unidentified X-ray sources for optical spectroscopy. Those 165 X-ray sources have been identified in the following classes: 115 emission line AGN (QSOs and Seyferts), 2 BL Lac objects and 4 BL Lac candidates, 22 clusters of galaxies, 12 Galactic stars and 10 objects remain unidentified. This represent a success rate of about 73% for detecting AGN using our selection criteria. Plausibility is based upon the optical classification and X-ray characteristics of the sources.