- ID:
- ivo://CDS.VizieR/J/ApJS/212/15
- Title:
- Polarized NVSS sources SEDs
- Short Name:
- J/ApJS/212/15
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- An understanding of cosmic magnetism requires converting the polarization properties of extragalactic radio sources into the rest-frame in which the corresponding polarized emission or Faraday rotation is produced. Motivated by this requirement, we present a catalog of multiwavelength linear polarization and total intensity radio data for polarized sources from the NRAO VLA Sky Survey. We cross-match these sources with a number of complementary measurements --combining data from major radio polarization and total intensity surveys such as AT20G, B3-VLA, GB6, NORTH6CM, Texas, and WENSS, together with other polarization data published over the last 50 years. For 951 sources, we present spectral energy distributions (SEDs) in both fractional polarization and total intensity, each containing between 3 and 56 independent measurements from 400MHz to 100GHz. We physically model these SEDs, and where available provide the redshift of the optical counterpart. For a superset of 25649 sources we provide the total intensity spectral index, {alpha}. Objects with steep versus flat {alpha} generally have different polarization SEDs: steep-spectrum sources exhibit depolarization, while flat-spectrum sources maintain constant polarized fractions over large ranges in wavelength. This suggests the run of polarized fraction with wavelength is predominantly affected by the local source environment, rather than by unrelated foreground magnetoionic material. In addition, a significant fraction (21%) of sources exhibit "repolarization," which further suggests that polarized SEDs are affected by different emitting regions within the source, rather than by a particular depolarization law. This has implications for the physical interpretation of future broadband polarimetric surveys.
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Search Results
- ID:
- ivo://CDS.VizieR/J/A+A/613/A58
- Title:
- Polarized point sources in LOTSS-HETDEX
- Short Name:
- J/A+A/613/A58
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have produced a catalog of 92 polarized radio sources at 150MHz at 4.3-arcmin resolution and 1mJy rms sensitivity, which is the largest catalog of polarized sources at such low frequencies. The data used was from the LOFAR Two-Meter Sky Survey (LOTSS) initial release (Shimwell et al., 2017, Cat. J/A+A/598/A104), (10h45m-15h30m right ascension, 45-57{deg} declination, 570 square degrees).
- ID:
- ivo://CDS.VizieR/J/AJ/142/89
- Title:
- Precise astrometry with VLBA (VIPS)
- Short Name:
- J/AJ/142/89
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present accurate positions for 857 sources derived from the astrometric analysis of 16 eleven-hour experiments from the Very Long Baseline Array imaging and polarimetry survey at 5GHz (VIPS). Among the observed sources, positions of 430 objects were not previously determined at milliarcsecond-level accuracy. For 95% of the sources the uncertainty of their positions ranges from 0.3 to 0.9mas, with a median value of 0.5mas. This estimate of accuracy is substantiated by the comparison of positions of 386 sources that were previously observed in astrometric programs simultaneously at 2.3/8.6GHz. Surprisingly, the ionosphere contribution to group delay was adequately modeled with the use of the total electron content maps derived from GPS observations and only marginally affected estimates of source coordinates.
- ID:
- ivo://CDS.VizieR/J/other/PASA/26.454
- Title:
- Precise positions of methanol masers
- Short Name:
- J/other/PASA/26.
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The Australia Telescope Compact Array (ATCA) has been used to determine positions for many southern methanol maser sites, with accuracy better than 1 arcsec. The results are presented here as a catalogue of more than 350 distinct sites, some of them new discoveries, and many others with positional precision 10-times better than existing published values. Clusters of 2 or 3 sites are occasionally found to account for single previously listed sources. This in turn reveals that the velocity range for each individual site is sometimes smaller than that of the originally tabulated (blended) source. Only a handful of examples then remain with a velocity range of more than 16km/s at a single compact (less than 2 arcsec) site. The precise methanol positions now allow apparent coincidences with OH masers to be confidently accepted or rejected; this has led to the important conclusion that, where a 1665-MHz OH maser lies in a massive star formation region, at more than 80 percent of the OH sites there is a precisely coincident methanol maser. The methanol precision achieved here will also allow clear comparisons with likely associated IR sources when the next generation of far-IR surveys produce precise positions.
- ID:
- ivo://CDS.VizieR/I/151
- Title:
- Precise Radio Source Positions from Mark III VLBI
- Short Name:
- I/151
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- This catalog contains observations from 600 Mark III VLBI experiments from conducted between 1979 to 1988. These experiments resulted in 237681 acceptable pairs of group delay and phase delay rate observations. These have been used to derive positions of 182 extra-galactic radio sources with typical formal standard errors less than 1 mas. The right ascension zero point of this reference frame has been aligned with the FK5 by using the optical positions of 28 extragalactic radio sources whose positions are on the FK5 system. Also included are the Mark III VLBI stations and a summary of the analysis configuration.
- ID:
- ivo://CDS.VizieR/J/A+A/475/359
- Title:
- Predicting radio fluxes of extrasolar planets
- Short Name:
- J/A+A/475/359
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Close-in giant extrasolar planets ("Hot Jupiters") are believed to be strong emitters in the decametric radio range. We present the expected characteristics of the low-frequency magnetospheric radio emission of all currently known extrasolar planets, including the maximum emission frequency and the expected radio flux. We also discuss the escape of exoplanetary radio emission from the vicinity of its source, which imposes additional constraints on detectability. We compare the different predictions obtained with all four existing analytical models for all currently known exoplanets. We also take care to use realistic values for all input parameters.
- ID:
- ivo://CDS.VizieR/J/ApJ/441/307
- Title:
- Proper motions and brightness of Cas A
- Short Name:
- J/ApJ/441/307
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The results of a multiple-epoch radio study of secular changes in the SNR Cassiopeia A are reported and used to construct a model for the dynamical evolution of diffuse and clumpy ejecta components in the remnant. To quantify the current dynamical status of various ejecta components, the proper motions and brightness evolution of a sample of 304 compact radio features have been accurately determined from high-quality interferometric observations of the remnant at lambda=6 and 20cm, spanning a total time baseline of 12yr. A simple model of homologous expansion does not provide a good fit to the measured proper motions of the radio knots. We find that a single estimate of the ejecta expansion age is not appropriate, as the expansion derived from compact features varies azimuthally and radially in the remnant and differs for subsets of knots segregated by brightness. We verify that the bulk of the radio-emitting plasma in Cas A has indeed been significantly decelerated by the current epoch; bulk expansion ages of 2.5-4 times the actual age of the remnant are measured . Based on these dynamical data, and information on the kinematics of the fast moving optical knots. we synthesize a model that directly relates the dynamics of ejecta components in Cas A to various radiative processes. This model is based on the premise that the emission from Cas A, at a variety of wavelengths, is deceleration-powered. If ejecta components are distributed over a range of internal densities, a sequential "turning-on" of components, in order of increasing density, should be observed. A model for the current emission distribution in Cas A, at radio, X-ray, and optical wavelengths, is outlined in terms of deceleration considerations.
- ID:
- ivo://CDS.VizieR/J/A+A/341/L79
- Title:
- Proper motions of faint ROSAT WTT stars
- Short Name:
- J/A+A/341/L79
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present proper motions of 59 stars of the ROSAT All-Sky Survey (RASS) located in direction of the Chamaeleon star forming region (SFR) in the magnitude range B=5.1-17mag. Proper motions of the fainter stars were newly derived utilizing survey Schmidt plates from the GSC~II plate archive and from a set of special plates taken with the ESO Schmidt telescope. The vector point diagram (VPD) indicates that the certified weak emission-line T Tauri (WTT) stars cluster away from the region occupied by the brighter pre-main-sequence stars (PMS) in Cha I. The distance to this new association is estimated at ~100pc, sensibly smaller than the 150pc generally assumed for the SFR. This yields an upper limit of 2km/s for the velocity dispersion of this new kinematic group. The de-reddened CM diagram of the group members suggest the WTT stars are still PMS objects, but older (3-30Myr) and less massive than previous determinations. These revised age estimates, the newly derived group peculiar velocity, and current distance estimates to the Cha~I/II/III complex would favour in-situ formation against that predicted by high velocity cloud models. Finally, based on a redetermination of the peculiar motions of stars and gas, we speculate that the whole SFR originated from the local Orion spur as a result of more classical mechanisms like interactions with the spiral arms.
- ID:
- ivo://CDS.VizieR/J/ApJ/899/159
- Title:
- Properties of 10 galaxies with Chandra
- Short Name:
- J/ApJ/899/159
- Date:
- 11 Mar 2022 14:27:52
- Publisher:
- CDS
- Description:
- We present an archival analysis of Chandra X-ray observations for 12 nearby early-type galaxies hosting radio sources with radio power >1023W/Hz at 1.4GHz, similar to the radio power of the radio source in NGC4261. Previously, in a similar analysis of eight nearby X-ray and optically bright elliptical galaxies, Werner et al. found that NGC4261 exhibited unusually low central gas entropy compared to the full sample. In the central 0.3kpc of NGC4261, the ratio of cooling time to freefall time (tcool/tff) is less than 10, indicating that cold clouds may be precipitating out of the hot ambient medium and providing fuel for accretion in the central region. NGC4261 also hosts the most powerful radio source in the original sample. Because NGC4261 may represent an important phase during which powerful feedback from a central active galactic nucleus (AGN) is fueled by multiphase condensation in the central kiloparsec, we searched the Chandra archive for analogs to NGC4261. We present entropy profiles of those galaxies, as well as profiles of tcool/tff. We find that one of them, IC4296, exhibits properties similar to NGC4261, including the presence of only single-phase gas outside of r~2kpc and a similar central velocity dispersion. We compare the properties of NGC4261 and IC4296 to hydrodynamic simulations of AGN feedback fueled by precipitation. Over the course of those simulations, the single-phase galaxy has an entropy gradient that remains similar to the entropy profiles inferred from our observations.
- ID:
- ivo://CDS.VizieR/J/MNRAS/497/2163
- Title:
- Properties of galaxy group sample
- Short Name:
- J/MNRAS/497/2163
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Our understanding of how active galactic nucleus feedback operates in galaxy clusters has improved in recent years owing to large efforts in multiwavelength observations and hydrodynamical simulations. However, it is much less clear how feedback operates in galaxy groups, which have shallower gravitational potentials. In this work, using very deep Very Large Array and new MeerKAT observations from the MIGHTEE survey, we compiled a sample of 247 X-ray selected galaxy groups detected in the COSMOS field. We have studied the relation between the X-ray emission of the intra-group medium and the 1.4GHz radio emission of the central radio galaxy. For comparison, we have also built a control sample of 142 galaxy clusters using ROSAT and NVSS data. We find that clusters and groups follow the same correlation between X-ray and radio emission. Large radio galaxies hosted in the centres of groups and merging clusters increase the scatter of the distribution. Using statistical tests and Monte Carlo simulations, we show that the correlation is not dominated by biases or selection effects. We also find that galaxy groups are more likely than clusters to host large radio galaxies, perhaps owing to the lower ambient gas density or a more efficient accretion mode. In these groups, radiative cooling of the intra-cluster medium could be less suppressed by active galactic nucleus heating. We conclude that the feedback processes that operate in galaxy clusters are also effective in groups.
