- ID:
- ivo://CDS.VizieR/J/AJ/130/1373
- Title:
- Radio observations of the HDFS region. II
- Short Name:
- J/AJ/130/1373
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- This paper is part of a series describing the results from the Australia Telescope Hubble Deep Field-South (ATHDFS) survey obtained with the Australia Telescope Compact Array. This survey consists of observations at 1.4, 2.5, 5.2, and 8.7GHz, all centered on the Hubble Deep Field-South. Here we present the first results from the extended observing campaign at 1.4GHz. A total of 466 sources have been cataloged to a local sensitivity of 5{sigma} (11{mu}Jy rms). A source extraction technique is developed that (1) successfully excludes spurious sources from the final source catalogs and (2) accounts for the nonuniform noise in our image. A source catalog is presented, and the general properties of the 1.4GHz image are discussed. We also present source counts derived from our ATHDFS 1.4GHz catalog.
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Search Results
- ID:
- ivo://CDS.VizieR/J/ApJ/746/23
- Title:
- Radio observations of ultracool dwarf stars
- Short Name:
- J/ApJ/746/23
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a new radio survey of about 100 late-M and L dwarfs undertaken with the Very Large Array. The sample was chosen to explore the role of rotation in the radio activity of ultracool dwarfs. As part of the survey we discovered radio emission from three new objects, 2MASS J0518113-310153 (M6.5), 2MASS J0952219-192431 (M7), and 2MASS J1314203+132001 (M7), and made an additional detection of LP 349-25 (M8). Combining the new sample with results from our previous studies and from the literature, we compile the largest sample to date of ultracool dwarfs with radio observations and measured rotation velocities.
- ID:
- ivo://CDS.VizieR/J/ApJ/833/288
- Title:
- Radio obs. of NGC 6251 jet
- Short Name:
- J/ApJ/833/288
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The structure of the NGC 6251 jet on the milliarcsecond scale is investigated using images taken with the European VLBI Network and the Very Long Baseline Array. We detect a structural transition of the jet from a parabolic to a conical shape at a distance of (1-2)x10^5^ times the Schwarzschild radius from the central engine, which is close to the sphere of gravitational influence of the supermassive black hole (SMBH). We also examine the jet pressure profiles with the synchrotron minimum energy assumption to discuss the physical origin of the structural transition. The NGC 6251 jet, together with the M87 jet, suggests a fundamental process of structural transition in the jets of active galactic nuclei (AGNs). Collimated AGN jets are characterized by their external galactic medium, showing that AGN jets interplay with the SMBH and its host galaxy.
- ID:
- ivo://CDS.VizieR/J/A+A/520/A62
- Title:
- Radio-optical scrutiny of compact AGN
- Short Name:
- J/A+A/520/A62
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We study the correlations between the VLBA (Very Long Baseline Array) radio emission at 15GHz, extended emission at 151MHz, and optical nuclear emission at 5100{AA} for a complete sample of 135 compact jets. We use the partial Kendall's tau correlation analysis to check the link between radio properties of parsec-scale jets and optical nuclear luminosities of host active galactic nuclei (AGN).
- ID:
- ivo://CDS.VizieR/J/A+A/560/A23
- Title:
- Radio properties of faint BL Lacs
- Short Name:
- J/A+A/560/A23
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The advent of Fermi is changing our understanding on the radio and gamma-ray emission in Active Galactic Nuclei. Contrary to pre-Fermi ideas, BL Lac objects are found to be the most abundant emitters in the gamma-ray band. However, since they are relatively weak radio sources, most of their parsec-scale structure and their multi-frequency properties are poorly understood and/or have not been investigated in a systematically fashion. Our main goal is to analyze the radio and gamma-ray emission properties of a sample of 42 BL Lacs selected, for the first time in the literature, with no constraint on their radio and gamma-ray flux densities/emission. Thanks to new Very Long Baseline Array observations at 8 and 15GHz for the whole sample, we present here fundamental parameters such as radio flux densities, spectral index information, and parsec-scale structure. Moreover, we search for gamma-ray counterparts using data reported in the Second Catalog of Fermi Gamma-ray sources. Parsec-scale radio emission is observed in the majority of the sources at both frequencies. Gamma-ray counterparts are found for 14/42 sources. The comparison between our results in radio and gamma-ray bands points out the presence of a large number of faint BL Lacs showing "non classical" properties such as low source compactness, core dominance, no gamma-ray emission and steep radio spectral indexes. A deeper multiwavelength analysis will be needed.
- 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/ApJ/703/370
- Title:
- Radio SNRs in nearby galaxies
- Short Name:
- J/ApJ/703/370
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We compile radio supernova remnant (SNR) samples from the literature for 19 nearby galaxies ranging from the SMC to Arp 220, and use this data to constrain the SNR luminosity function (LF) at 20cm. We find that radio SNR populations are strikingly similar across galaxies. The LF can be described as a power law with constant index and scaling proportional to a galaxy's star formation rate (SFR). Unlike previous authors, we do not find any dependence of SNR luminosity on a galaxy's global interstellar medium density. The observed correlation between the luminosity of a galaxy's brightest SNR and a galaxy's SFR can be completely explained by statistical effects, wherein galaxies with higher SFR more thoroughly sample the high-luminosity end of the SNR LF. The LF is well fitted by a model of SNR synchrotron emission which includes diffusive shock acceleration and magnetic field amplification, if we assume that all remnants are undergoing adiabatic expansion, the densities of star-forming regions are similar across galaxies, and the efficiency of cosmic ray production is constant.
- ID:
- ivo://CDS.VizieR/J/ApJ/686/859
- Title:
- Radio sources at 0.327, 1.4, 4.5, 8.5GHz
- Short Name:
- J/ApJ/686/859
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present an analysis of the energetics and particle content of the lobes of 24 radio galaxies at the cores of cooling clusters. The radio lobes in these systems have created visible cavities in the surrounding hot, X-ray-emitting gas, which allow direct measurement of the mechanical jet power of radio sources over six decades of radio luminosity, independently of the radio properties themselves. We find that jet (cavity) power increases with radio synchrotron power approximately as P_jet_~L^{beta}^_radio_, where 0.35<={beta}<=0.70 depending on the bandpass of measurement and state of the source. Furthermore, we place limits on the magnetic field strengths and particle content of the radio lobes using a variety of X-ray constraints. We find that the lobe magnetic field strengths vary between a few to several tens of microgauss depending on the age and dynamical state of the lobes.
- ID:
- ivo://CDS.VizieR/J/AZh/80/978
- Title:
- Radio sources identifications at DE=10-12.5deg
- Short Name:
- J/AZh/80/978
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The results of 0.97, 2.3, 3.9, 7.7, 11.1 and 21.7GHz observations of a complete sample of radio sources obtained on the RATAN-600 radio telescope are presented. The sample is comprised of sources from the 4.85-GHz MGB survey, and contains all sources at declinations 10-12.5 degrees (J2000) with galactic latitudes |b|>15 degrees and flux densities S(4.85)>200mJy. Optical identifications have been obtained for about 86% of the radio sources with flat spectra and 59% of those with steep spectra.
- ID:
- ivo://CDS.VizieR/J/ApJS/125/427
- Title:
- Radio sources in HH 7-11 region
- Short Name:
- J/ApJS/125/427
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Using the Very Large Array, a sensitive radio survey at 6 and 3.6 cm was carried out in the HH 711 region. The data were acquired in 10 observing runs between 1991 and 1998 with several VLA configurations, and the angular resolutions are about 4-5". A total of 44 radio sources were detected in the 8'x8' region centered at this HH complex. The majority of these sources, at least 26 of them, are believed to be associated with young objects in the cloud.
