- ID:
- ivo://CDS.VizieR/J/ApJ/634/L89
- Title:
- 4.8GHz observations of SGR 1806-20
- Short Name:
- J/ApJ/634/L89
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The 2004 December 27 giant {gamma}-ray flare detected from the magnetar SGR 1806-20 created an expanding radio nebula that we have monitored with the Australia Telescope Compact Array and the Very Large Array. These data indicate that there was an increase in the observed flux 25 days after the initial flare that lasted for 8 days, which we believe is the result of ambient material swept up and shocked by this radio nebula.
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- ID:
- ivo://CDS.VizieR/J/AJ/142/3
- Title:
- 1.4GHz observations of Stripe 82
- Short Name:
- J/AJ/142/3
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a high-resolution radio survey of the Sloan Digital Sky Survey (SDSS) Southern Equatorial Stripe, a.k.a. Stripe 82. This 1.4GHz survey was conducted with the Very Large Array primarily in the A-configuration, with supplemental B-configuration data to increase sensitivity to extended structure. The survey has an angular resolution of 1.8" and achieves a median rms noise of 52{mu}Jy/beam over 92deg^2^. This is the deepest 1.4GHz survey to achieve this large of an area, filling a gap in the phase space between small, deep and large, shallow surveys. It also serves as a pilot project for a larger high-resolution survey with the Expanded Very Large Array. We discuss the technical design of the survey and details of the observations, and we outline our method for data reduction. We present a catalog of 17969 isolated radio components, for an overall source density of ~195sources/deg^2^. The astrometric accuracy of the data is excellent, with an internal check utilizing multiply observed sources yielding an rms scatter of 0.19" in both right ascension and declination. A comparison to the SDSS-DR7 Quasar Catalog further confirms that the astrometry is well tied to the optical reference frame, with mean offsets of 0.02+/-0.01" in right ascension, and 0.01+/-0.02" in declination. A check of our photometry reveals a small, negative CLEAN-like bias on the level of 35{mu}Jy. We report on the catalog completeness, finding that 97% of FIRST-detected quasars are recovered in the new Stripe 82 radio catalog, while faint, extended sources are more likely to be resolved out by the resolution bias. We conclude with a discussion of the optical counterparts to the catalog sources, including 76 newly detected radio quasars.
- ID:
- ivo://CDS.VizieR/J/MNRAS/344/1
- Title:
- 22GHz observations of VX Sgr
- Short Name:
- J/MNRAS/344/1
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We used MERLIN to observe 22-GHz H_2_O maser emission from the red supergiant VX Sgr in 1994 and 1999. The masers lie in a region 300-400mas in diameter. The angular size and the velocity distribution of the masers are similar at both epochs, although the total flux density in 1999 is only half of that seen in 1994.
- ID:
- ivo://CDS.VizieR/J/ApJ/777/157
- Title:
- 90GHz obs. of high-mass star-forming regions
- Short Name:
- J/ApJ/777/157
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The chemical changes of high-mass star-forming regions provide a potential method for classifying their evolutionary stages and, ultimately, ages. In this study, we search for correlations between molecular abundances and the evolutionary stages of dense molecular clumps associated with high-mass star formation. We use the molecular line maps from Year 1 of the Millimetre Astronomy Legacy Team 90GHz (MALT90) Survey. The survey mapped several hundred individual star-forming clumps chosen from the ATLASGAL survey to span the complete range of evolution, from prestellar to protostellar to H II regions. The evolutionary stage of each clump is classified using the Spitzer GLIMPSE/MIPSGAL mid-IR surveys. Where possible, we determine the dust temperatures and H_2_ column densities for each clump from Herschel/Hi-GAL continuum data. From MALT90 data, we measure the integrated intensities of the N_2_H^+^, HCO^+^, HCN and HNC(1-0) lines, and derive the column densities and abundances of N_2_H^+^ and HCO^+^. The Herschel dust temperatures increase as a function of the IR-based Spitzer evolutionary classification scheme, with the youngest clumps being the coldest, which gives confidence that this classification method provides a reliable way to assign evolutionary stages to clumps. Both N_2_H^+^ and HCO^+^ abundances increase as a function of evolutionary stage, whereas the N_2_H^+^(1-0) to HCO^+^(1-0) integrated intensity ratios show no discernable trend. The HCN(1-0) to HNC(1-0) integrated intensity ratios show marginal evidence of an increase as the clumps evolve.
- ID:
- ivo://CDS.VizieR/J/ApJ/614/607
- Title:
- 8.4GHz obs. of scintillating sources
- Short Name:
- J/ApJ/614/607
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We compare the milliarcsecond-scale morphology of scintillating and nonscintillating sources. The scintillating sources are drawn from those flat-spectrum extragalactic radio sources discovered, by the Micro-Arcsecond Scintillation-Induced Variability Survey (MASIV, Lovell et al, 2003AJ....126.1699L), to have flux density variability at 5GHz on timescales from hours to days. Intrinsic source structure information is obtained from previously published and/or publicly available 8.4GHz Very Long Baseline Array images. A sample of low flux density (S_{nu}=5GHz_<0.3Jy) scintillating sources was compared with a sample of high flux density (S_{nu}=5GHz_~1Jy) scintillators, as well as a sample of high flux density nonscintillators.
- ID:
- ivo://CDS.VizieR/J/ApJ/750/170
- Title:
- 6.035GHz OH observations of two IRAS
- Short Name:
- J/ApJ/750/170
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We report the discovery of 6.035GHz hydroxyl (OH) maser flares toward the massive star-forming region IRAS 18566+0408 (G37.55+0.20), which is the only region known to show periodic formaldehyde (4.8GHz H_2_CO) and methanol (6.7GHz CH_3_OH) maser flares. The observations were conducted between 2008 October and 2010 January with the 305m Arecibo Telescope in Puerto Rico. We detected two flare events, one in 2009 March and one in 2009 September to November. The OH maser flares are not simultaneous with the H_2_ CO flares, but may be correlated with CH_3_ OH flares from a component at corresponding velocities. A possible correlated variability of OH and CH_3_ OH masers in IRAS 18566+0408 is consistent with a common excitation mechanism (IR pumping) as predicted by theory.
- ID:
- ivo://CDS.VizieR/J/A+A/482/483
- Title:
- GHz-peaked spectrum (GPS) sources
- Short Name:
- J/A+A/482/483
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Gigahertz-peaked spectrum (GPS) sources and high frequency peakers (HFPs) are among the smallest of active galactic nuclei currently believed to represent the earliest phases in the evolution of extragalactic radio sources. Recently there has been evidence of contamination by other types of radio sources among the GPS and HFP samples, but the confirmed GPS sources or HFPs also seem to form a very heterogeneous population. We study the statistical clustering of the GPS sources and the HFPs by taking as many source parameters as possible to find homogeneous groups among the sources. We expect the clustering to give us insight into the physical parameters that play a role in different source populations. We have collected a sample of 206 GPS sources and HFPs from the literature and gathered a massive database of various source properties, such as the redshift, the size, the polarization, the magnitudes, and the properties of the radio continuum. To visualize and to cluster these multidimensional data we used self-organising maps (SOM), which are neural networks trained by an unsupervised algorithm. We have classified the sources with an auxiliary classification to trace the locations of different types of radio continuum spectra on the map.
- ID:
- ivo://CDS.VizieR/J/A+AS/131/303
- Title:
- GHz-Peaked-Spectrum radio sources
- Short Name:
- J/A+AS/131/303
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We define a complete sample of thirty-three GHz-Peaked-Spectrum (GPS) radio sources based on their spectral properties. We present measurements of the radio spectra and polarization of the complete sample and a list of additional GPS sources which fail one or more criteria to be included in the complete sample. The majority of the data have been obtained from quasi-simultaneous multi-frequency observations at the Very Large Array (VLA) during 3 observing sessions. Low frequency data from the Westerbork Synthesis Radio Telescope (WSRT) and from the literature have been combined with the VLA data in order to better define the spectral shape. The objects presented here show a rather wide range of spectral indices at high and low frequencies, including a few cases where the spectral index below the turnover is close to the theoretical value of 2.5 typical of self-absorbed incoherent synchrotron emission. Faint and diffuse extended emission is found in about 10% of the sources. In the majority of the GPS sources, the fractional polarization is found to be very low, consistent with the residual instrumental polarization of 0.3%.
- 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.
- ID:
- ivo://CDS.VizieR/J/MNRAS/380/1449
- Title:
- 1.4GHz radio sources in Lynx and Hercules fields
- Short Name:
- J/MNRAS/380/1449
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- With the goal of identifying high-redshift radio galaxies with Fanaroff-Riley class I (FR I) classification, here are presented high-resolution, wide-field radio observations, near-infrared and optical imaging and multi-object spectroscopy of two fields of the Leiden-Berkeley Deep Survey. These fields, Hercules.1 and Lynx.2, contain a complete sample of 81 radio sources with S(1.4GHz)>0.5mJy within 0.6deg^2^. This sample will form the basis for a study of the population and cosmic evolution of high-redshift, low-power, FR I radio sources which will be presented in Paper II. Currently, the host galaxy identification fraction is 86 per cent with 11 sources remaining unidentified at a level of r'>=25.2mag (Hercules; 4 sources) or r'>=24.4mag (Lynx; 7 sources) or K>=20mag. Spectroscopic redshifts have been determined for 49 per cent of the sample and photometric redshift estimates are presented for the remainder of the sample.
