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1271. 1.4GHz obs. and optical ident. in A3558
ID:
ivo://CDS.VizieR/J/A+A/419/71
Title:
1.4GHz obs. and optical ident. in A3558
Short Name:
J/A+A/419/71
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present Very Large Array (VLA) 1.4GHz (21cm) observations of the region between the centres of A3558 and A3562, in the major cluster merger complex of the Shapley Concentration. Our final catalogue includes a total of 174 radio sources above the flux density limit of 0.25 mJy/b. By cross-correlation with optical and spectroscopic catalogues we found 33 optical counterparts belonging to the Shapley Concentration.
1272. 1.4GHz observations of bright early-type galaxies
ID:
ivo://CDS.VizieR/J/ApJ/731/L41
Title:
1.4GHz observations of bright early-type galaxies
Short Name:
J/ApJ/731/L41
Date:
21 Oct 2021
Publisher:
CDS
Description:
We have measured the radio continuum emission of 396 early-type galaxies brighter than K=9, using 1.4GHz imagery from the NRAO Very Large Array Sky Survey, Green Bank 300ft Telescope, and 64m Parkes Radio Telescope. For M_K_<-24 early-type galaxies, the distribution of radio powers at fixed absolute magnitude spans four orders of magnitude and the median radio power is proportional to K-band luminosity to the power 2.78+/-0.16. The measured flux densities of M_K_<-25.5 early-type galaxies are greater than zero in all cases. It is thus highly likely that the most massive galaxies always host an active galactic nucleus or have recently undergone star formation.
1273. 8.4GHz observations of compact starbursts
ID:
ivo://CDS.VizieR/J/ApJ/378/65
Title:
8.4GHz observations of compact starbursts
Short Name:
J/ApJ/378/65
Date:
21 Oct 2021
Publisher:
CDS
Description:
The 40 ultraluminous (log(LFIR/L_{sun}_>=11.25) galaxies in the IRAS Bright Galaxy Sample of sources stronger than S=5.24Jy at {lambda}=60{mu}m were mapped with approximately 0.25-arcsec resolution at 8.44GHz. Twenty-five contain diffuse radio sources obeying the FIR-radio correlation; these are almost certainly starburst galaxies. Fourteen other galaxies have nearly blackbody FIR spectra with color temperatures between 60 and 80K so their (unmeasured) FIR angular sizes must exceed approximately 0.25-arcsec, yet they contain compact (but usually resolved) radio sources smaller than this limit. The unique radio and FIR properties of these galaxies can be modeled by ultraluminous nuclear starbursts so dense that they are optically thick to free-free absorption at {nu}~1.49GHz and dust absorption at {lambda}~25{mu}m. Only one galaxy (UGC 08058 = Mrk 231) is a dominated by a variable radio source too compact to be an ultraluminous starburst; it must be powered by a 'monster'.
1274. 37 GHz observations of NLS1 galaxies
ID:
ivo://CDS.VizieR/J/A+A/603/A100
Title:
37 GHz observations of NLS1 galaxies
Short Name:
J/A+A/603/A100
Date:
21 Oct 2021
Publisher:
CDS
Description:
Observations performed at Metsahovi Radio Observatory at 37GHz are presented for a sample of 78 radio-loud and radio-quiet narrow-line Seyfert 1 (NLS1) galaxies, together with additional lower and higher frequency radio data from RATAN-600, Owens Valley Radio Observatory, and the Planck satellite. Most of the data have been gathered between February 2012 and April 2015 but for some sources even longer light curves exist. The detection rate at 37GHz is around 19%, which is comparable to other populations of active galactic nuclei presumed to be faint at radio frequencies, such as BL Lac objects. Variability and spectral indices are determined for sources with enough detections. Based on the radio data, many NLS1 galaxies show a blazar-like radio spectra exhibiting significant variability. The spectra at a given time are often inverted or convex. The source of the high-frequency radio emission in NLS1 galaxies, detected at 37GHz, is most probably a relativistic jet rather than star formation. Jets in NLS1 galaxies are therefore expected to be a much more common phenomenon than earlier assumed.
1275. 164 GHz-peaked spectrum sources
ID:
ivo://CDS.VizieR/J/other/AstBu/74.348
Title:
164 GHz-peaked spectrum sources
Short Name:
J/other/AstBu/74
Date:
21 Oct 2021
Publisher:
CDS
Description:
Gigahertz-Peaked spectrum (GPS) sources are compact active galactic nuclei, presumably young precursors of bright radio sources. The study of GPS radio properties provides information about the features of synchrotron radiation in extragalactic sources. Also in applied research, GPS sources are useful as compact stationary radio sources in the sky for astrometric purposes. This paper presents the results of a multifrequency GPS study based on quasi-simultaneous measurements with the RATAN-600 radio telescope during the 2006-2017 period. A catalog of GPS spectral flux densities at six frequencies - 1.1, 2.3, 4.8, 7.7/8.2, 11.2, and 21.7GHz - is obtained. In addition, for the analysis of radio spectra, data from low-frequency surveysGLEAM(GaLactic and Extragalactic AllskyMurchisonwidefield array survey) and TGSS (Tata institute for fundamental research GMRT Sky Survey) and high-frequency measurements from Planck survey are used. A total number of 164 GPS and candidates have been identified (17 of them are new discoveries), which makes up a small fraction of GPS in the initial sample of bright AGNs - about 2%. The physical properties and formation conditions of synchrotron radiation is found to be quite different in GPS of different AGNs types. The deficit of distant GPS (z>2) with low maximum frequencies (less than 1GHz) has been confirmed. The existing "size-peak frequency" anticorrelation is continuous. The continuum radio spectra are found to become statistically steeper with increasing redshift.
1276. 1.4GHz radio variability in FIRST & SDSS Stripe 82
ID:
ivo://CDS.VizieR/J/ApJ/769/125
Title:
1.4GHz radio variability in FIRST & SDSS Stripe 82
Short Name:
J/ApJ/769/125
Date:
21 Oct 2021
Publisher:
CDS
Description:
We report on a blind survey for extragalactic radio variability that was carried out by comparing two epochs of data from the Faint Images of the Radio Sky at Twenty centimeters survey with a third epoch from a new 1.4GHz survey of SDSS Stripe 82. The three epochs are spaced seven years apart and have an overlapping area of 60deg^2^. We uncover 89 variable sources down to the millijansky level, 75 of which are newly identified, and we find no evidence for transient phenomena. This new sample of variable sources allows us to infer an upper limit to the mean characteristic timescale of active galactic nucleus radio variability of 14yr. We find that only 1% of extragalactic sources have fractional variability f_var_>3, while 44% of Galactic sources vary by this much. The variable sample contains a larger fraction of quasars than a comparable non-variable control sample, though the majority of the variable sources appear to be extended galaxies in the optical. This implies that either quasars are not the dominant contributor to the variability of the sample, or that the deep optical data allow us to detect the host galaxies of some low-z quasars. We use the new, higher resolution data to report on the morphology of the variable sources. Finally, we show that the fraction of sources that are variable remains constant or increases at low flux densities. This may imply that next generation radio surveys with telescopes like Australian Square Kilometer Array Pathfinder and MeerKAT will see a constant or even increasing fraction of variable sources down into the sub-millijansky regime.
1277. 1.4 GHz source survey
ID:
ivo://CDS.VizieR/J/AJ/99/1071
Title:
1.4 GHz source survey
Short Name:
J/AJ/99/1071
Date:
21 Oct 2021
Publisher:
CDS
Description:
We report on 1.4GHz continuum observations for 56 contiguous VLA fields, using the D configuration, in a region devoid of nearby, rich galaxy clusters (at z<0.4). 354 continuum sources are tabulated, with fluxes down to about 1.5mJy, in an area of about 12degres^+2^. Only about seven of the 354 radio sources are associated with known rich galaxy clusters at z>0.4 (tabulated by Gunn, Hoessel, and Oke, 1986ApJ...306...30G). We compare source positions with those from an optical catalog (generated from a POSS plate with the use of the Minnesota Automated Plate Scanner) and find mild correlations on angular scales of order 1arcmin. This suggests some association of radio sources with galaxy groups (sizes of order 200 kpc) at redshifts of order z~0.1, even though there are no rich galaxy clusters in this redshift range.
1278. 1.4GHz survey in HDF region
ID:
ivo://CDS.VizieR/J/ApJ/533/611
Title:
1.4GHz survey in HDF region
Short Name:
J/ApJ/533/611
Date:
21 Oct 2021
Publisher:
CDS
Description:
We have conducted a deep radio survey with the Very Large Array at 1.4GHz of a region containing the Hubble Deep Field (HDF). This survey overlaps previous observations at 8.5GHz allowing us to investigate the radio spectral properties of microJansky sources to flux densities greater than 40{mu}Jy at 1.4GHz and greater than 8{mu}Jy at 8.5GHz. A total of 371 sources have been catalogued at 1.4GHz as part of a complete sample within 20 of the HDF.
1279. 5-GHz Survey of Bright Galaxies
ID:
ivo://CDS.VizieR/J/AJ/80/771
Title:
5-GHz Survey of Bright Galaxies
Short Name:
J/AJ/80/771
Date:
21 Oct 2021
Publisher:
CDS
Description:
The 1135 galaxies in the Reference Catalogue of Bright Galaxies (Cat. <VII/16>) with declinations between +10{deg} and +70{deg} were surveyed at 6-cm wavelength with a 3-sigma detection limit of about 30mf.u.; of these 149 were detected. For 90 of these galaxies, spectral indices were obtained. There is a suggestion that the elliptical galaxies have flat spectra more often than the spiral galaxies.
1280. Giant HII regions BOND abundances
ID:
ivo://CDS.VizieR/J/MNRAS/460/1739
Title:
Giant HII regions BOND abundances
Short Name:
J/MNRAS/460/1739
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present the Bayesian oxygen and nitrogen abundance determinations (bond) method. bond is a Bayesian code (available at: http://bond.ufsc.br) to simultaneously derive oxygen and nitrogen abundances in giant HII regions. It compares observed emission lines to a grid of photoionization models without assuming any relation between O/H and N/O. Our grid spans a wide range in O/H, N/O and ionization parameter U, and covers different starburst ages and nebular geometries. Varying starburst ages accounts for variations in the ionizing radiation field hardness, which arise due to the ageing of HII regions or the stochastic sampling of the initial mass function. All previous approaches assume a strict relation between the ionizing field and metallicity. The other novelty is extracting information on the nebular physics from semistrong emission lines. While strong lines ratios alone ([OIII]/H{beta}, [OII]/H{beta} and [NII]/H{beta}) lead to multiple O/H solutions, the simultaneous use of [ArIII]/[NeIII] allows one to decide whether an HII region is of high or low metallicity. Adding HeI/H{beta} pins down the hardness of the radiation field. We apply our method to HII regions and blue compact dwarf galaxies, and find that the resulting N/O versus O/H relation is as scattered as the one obtained from the temperature-based method. As in previous strong-line methods calibrated on photoionization models, the bond O/H values are generally higher than temperature-based ones, which might indicate the presence of temperature fluctuations or kappa distributions in real nebulae, or a too soft ionizing radiation field in the models.