- ID:
- ivo://CDS.VizieR/J/AJ/142/108
- Title:
- Radio variability of compact, flat-spectrum AGNs
- Short Name:
- J/AJ/142/108
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The 4.9GHz Micro-Arcsecond Scintillation-Induced Variability (MASIV) Survey detected a drop in interstellar scintillation (ISS) for sources at redshifts z>~2, indicating an apparent increase in angular diameter or a decrease in flux density of the most compact components of these sources relative to their extended emission. This can result from intrinsic source size effects or scatter broadening in the intergalactic medium (IGM) in excess of the expected (1+z)^1/2^ angular diameter scaling of brightness temperature limited sources resulting from cosmological expansion. We report here 4.9GHz and 8.4GHz observations and data analysis for a sample of 140 compact, flat-spectrum sources which may allow us to determine the origin of this angular diameter-redshift relation by exploiting their different wavelength dependences. In addition to using ISS as a cosmological probe, the observations provide additional insight into source morphologies and the characteristics of ISS.
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- ID:
- ivo://CDS.VizieR/J/A+A/654/A169
- Title:
- Radio variability to identifying changing jets
- Short Name:
- J/A+A/654/A169
- Date:
- 16 Mar 2022 00:56:46
- Publisher:
- CDS
- Description:
- Supermassive black holes can launch highly relativistic jets with velocities reaching Lorentz factors of as high as {GAMMA}>50. How the jets accelerate to such high velocities and where along the jet they reach terminal velocity are open questions that are tightly linked to their structure as well as their launching and dissipation mechanisms. Changes in the beaming factor along the jets could potentially reveal jet acceleration, deceleration, or bending. We aim to (1) quantify the relativistic effects in multiple radio frequencies and (2) study possible jet velocity-viewing angle variations at parsec scales. We used the state-of-the-art code Magnetron to model light curves from the University of Michigan Radio Observatory and the Metsahovi Radio Observatory's monitoring programs in five frequencies covering about 25 years of observations in the 4.8 to 37GHz range for 61 sources. We supplement our data set with high-frequency radio observations in the 100-340GHz range from ALMA, CARMA, and SMA. For each frequency we estimate the Doppler factor which we use to quantify possible changes in the relativistic effects along the jets. The majority of our sources do not show any statistically significant difference in their Doppler factor across frequencies. This is consistent with constant velocity in a conical jet structure, as expected at parsec scales. However, our analysis reveals 17 sources where relativistic beaming changes as a function of frequency. In the majority of cases, the Doppler factor increases towards lower frequencies. Only 1253-053 shows the opposite behavior. By exploring their jet properties we find that the jet of 0420-014 is likely bent across the 4.8-340GHz range. For 0212+735, the jet is likely parabolic, and still accelerating in the 4.8-37GHz range. We discuss possible interpretations for the trends found in the remaining sources.
- 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.
- ID:
- ivo://CDS.VizieR/J/A+AS/87/1
- Title:
- RATAN-600 7.6 cm catalog of radio sources
- Short Name:
- J/A+AS/87/1
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- A catalog containing 840 radio sources obtained during the Experiment Cold-80 at 7.6 cm wavelength using RATAN-600 are presented. The completeness of the list in the central zone is about 0.7-0.8 for sources with flux density 7.5-15 mJy. For sources brighter than 15 mJy the completeness reaches one. The number of sources-flux density differential curve is constructed. Spectra are given for 230 sources.
- ID:
- ivo://CDS.VizieR/J/other/AstBu/72.150
- Title:
- RATAN COLD Reined (RCR) catalogue
- Short Name:
- J/other/AstBu/72
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the additional list of radio sources of the RCR (RATAN Cold Refined) catalog. The sources was obtained on the observation data of the COLD experiment which included a series of surveys carried out in 1980-1999 on the RATAN-600 radio telescope. This part of RCR catalogue contains the right ascensions, integrated flux densities at 7.6cm (3.94GHz) and their spectral indices 3.94 and 0.5GHz of 269 objects detected in the right-ascension interval 2h<R.A.<7h and also additional 24 radio sources found in only one survey and 3 transient candidates in the right-ascension interval 2h<R.A.<17h. We constructed radio spectra of the sources using data of the catalogues from CATS and VizieR databases which the strip of COLD surveys overlays, and, in cases of weak sources, for this purpose we used the flux density values estimated from VLSSr, GLEAM, TGSS, and GB6 survey maps. 6% of the sources, which are mostly weaker than 30 mJy at 3.94GHz, have flux density data only at two frequencies - 1.4 and 3.94GHz. About 30% of these sources have flat or inverse spectra (alpha>-0.5) at 3.94GHz. We verified the reliability of identifications of the sources detected in the scans by comparing the coordinates and integrated flux densities with the corresponding parameters of the sources of the NVSS catalogue. In the central 10'-part of the strip at 10mJy level completness of the catalogue is about 90% and we found no objects that lack in decimeter-wave catalogues.
- ID:
- ivo://CDS.VizieR/J/A+A/370/78
- Title:
- RATAN-600 NCP bright radio sources
- Short Name:
- J/A+A/370/78
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- A survey of the North Celestial Pole region using the RATAN-600 radio telescope at five frequencies in the range 2.3 to 21.7 GHz is described. Sources were chosen from the NVSS catalogue. The flux densities of 171 sources in the Declination range +75{deg} to +88{deg} are presented; typical flux density errors are 5-10 percent including calibration errors. About 20 percent of the sources have flat spectra or a flat component.
- ID:
- ivo://CDS.VizieR/J/other/BSAO/46.62
- Title:
- RATAN observations of Galactic SNRs
- Short Name:
- J/other/BSAO/46.
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present radio continuum spectra for 200 Galactic supernova remnants (SNRs) from 220 known and included in Green's (1998, Cat. VII/211) catalog. The spectra can be plotted only for 200 SNRs because about 20 remaining new and weak SNRs (Whiteoak and Green, 1996, Cat. J/A+AS/118/329; Gray, 1994MNRAS.270..847G) have only one-frequency flux density measurements. Spectrum plotting is an "on-line" procedure of the CATS database (Verkhodanov et al., 1997ASPCo.125..322V) created for some other multi-frequency catalogs. These spectra include most of the measurements available in literature, as well as multi-frequency measurements of nearly 120 SNRs with the RATAN-600 radio telescope in 1, 2 and 4 Galactic quadrants and from the Galactic plane survey at 960 and 3900MHz (Trushkin, 1986ATsir1453....4T, 1987AISAO..25...84T, 1989, Ph.D. Thesis. SAO, Nizhnij Arkhyz, 1996BSAO...41...64T, 1998BSAO...46...62T). The measurements have been placed on the same absolute flux density scale of Baars (1977A&A....61...99B) as in the paper by Kassim (1989ApJ...347..915K), using the correcting factor from the compiled catalog (Kuhr et al., 1981, Cat. VIII/5). The presented compilation has given a possibility of plotting quite accurate spectra with the thermal plasma free-free absorption in fitting the spectra accounted for.
- ID:
- ivo://CDS.VizieR/J/AZh/74/42
- Title:
- RATAN-600 radio sources spectra
- Short Name:
- J/AZh/74/42
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- A multifrequency deep survey of a band of sky with the declination of the source SS 433 ({delta}~5{deg}+/-20') was performed as part of the "Kholod" program on the RATAN-600 in 1987-1988. The right ascension intervals covered by the survey are 0h<{alpha}<14h and 18h<{alpha}<24h. The spectral properties of 400 sources from the RC catalog were determined for the first time by using only RATAN-600 data. The maximum in the flux density distribution for these sources at the central wavelength, {lambda}7.6cm, occurs at ~30mJy. The lower flux limits for the sample at wavelengths of 3.9, 7.6, 13.0, and 31.0cm are 16, 9, 37, and 61mJy, respectively. These observations provide the first flux estimates at 13.0 and 31.0cm for 90% of the sources. Spectra were measured for the first time for 112 sources (28%) and were revised for 90 sources (23%). The maximum in the spectral index distribution for the entire sample in the interval from {lambda}{lambda}7.6-31.0cm occurs at {alpha}=-0.86+/-0.04 (S_v_~{nu}^{alpha}^). The spectra of some 20 of the sample sources (5%) are peaked at roughly 1GHz, and about 40 spectra (10%) have low-frequency breaks. Roughly 70 sources (19%) have flat spectra ({alpha}>-0.5), and 64 (18%) have very steep spectra ({alpha}<-1.1).
- ID:
- ivo://CDS.VizieR/J/other/BSAO/40.128
- Title:
- RATAN-600 radio sources spectra
- Short Name:
- J/other/BSAO/40.
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- In accordance with the program "Cold" in 1987-1988 and in 1996 deep surveys of the sky strip at the declination of the source SS 433 ({delta}~5{deg}+/-20') were made at the radio telescope RATAN-600. For the first time spectral characteristics of 400 sources from the RC catalog have been determined using only the data obtained with the RATAN-600. The maximum of the flux density distributions at the central wavelength {lambda}7.6cm is ~30mJy. The lower flux limit in the sample of the sources at the wavelengths 3.9, 7.6, 13.0, 31.0cm is 16, 9, 37, 61mJy, respectively. Spectra of 112 sources (28%) have been obtained for the first time, spectra of 90 (23%) sources have been made more accurate. For the first time the fluxes at the wavelengths 2.7, 3.9, 13.0 and 31.0cm (90% of data) have been measured. The maximum of the distribution of spectral indices for the entire sample of sources in the interval {lambda}{lambda}7.6-31.0cm falls at {alpha}=-0.86+/-0.04 (S_{nu}_{prop.to}{nu}^alpha^). About 20 (5%) sources of the sample have a maximum of radiation at a frequency of about 1GHz (GHz-Peaked-Spectrum radio sources), about 40 (10%) have a low-frequency cut off of the spectrum. About 70 (19%) sources have flat spectra ({alpha}>-0.5), 64 (18%) very steep ({alpha}<-1.1) spectra.
- ID:
- ivo://CDS.VizieR/J/other/BSAO/40.5
- Title:
- RATAN-600 RC radio sources
- Short Name:
- J/other/BSAO/40.
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We use the RATAN-600 radio telescope for picking up the most distant objects in the Universe. As a first step, about 100 steep spectrum FRII radio galaxies (SS FRII RG) from the RATAN-600 RC catalog (Parijskij et al., 1991, Cat. <J/A+AS/87/1>; 1992A&AS...96..583P) were mapped by the VLA and identified with optical objects down to 24-25 R mag. All the VLA images and all the deep CCD images of the RC SS fields, collected up to now, are given. An updated list of calibrators with the known redshifts of the same SS FRII class RGs was compiled to estimate photometric redshifts, redshifts from angular size - redshift relations and by the radio "standard candle" method. The mean redshift of the RC SS FRII RG list happened to be greater than 2. BVRI photometry was made, and by standard model fittings we estimated "color" redshifts and the ages of stellar systems of the parent gE galaxies in 14 cases. Several objects were found in which active star formation began in the first billion years after the Big Bang. We believe that more than 10000 of such old active galaxies are available on the sky and all of them are in the range of present day optical and radio facilities.
