- ID:
- ivo://CDS.VizieR/J/A+A/593/A86
- Title:
- Arp 220 LOFAR radio images at 150MHz
- Short Name:
- J/A+A/593/A86
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We analyse new observations with the International Low Frequency Array (LOFAR) telescope, and archival data from the Multi-Element Radio Linked Interferometer Network (MERLIN) and the Karl G. Jansky Very Large Array (VLA). We model the spatially resolved radio spectrum of Arp 220 from 150MHz to 33GHz. We present an image of Arp 220 at 150MHz with resolution 0.65"x0.35", sensitivity 0.15mJy/beam, and integrated flux density 394+/-59mJy. More than 80% of the detected flux comes from extended (6"~2.2kpc) steep spectrum (alpha=-0.7) emission, likely from star formation in the molecular disk surrounding the two nuclei. We find elongated features extending 0.3" (110pc) and 0.9" (330pc) from the eastern and western nucleus respectively, which we interpret as evidence for outflows. The extent of radio emission requires acceleration of cosmic rays far outside the nuclei. We find that a simple three component model can explain most of the observed radio spectrum of the galaxy. When accounting for absorption at 1.4GHz, Arp 220 follows the FIR/radio correlation with q=2.36, and we estimate a star formation rate of 220M_{sun}_/yr. We derive thermal fractions at 1GHz of less than 1% for the nuclei, which indicates that a major part of the UV-photons are absorbed by dust. International LOFAR observations shows great promise to detect steep spectrum outflows and probe regions of thermal absorption. However, in LIRGs the emission detected at 150MHz does not necessarily come from the main regions of star formation. This implies that high spatial resolution is crucial for accurate estimates of star formation rates for such galaxies at 150MHz.
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Search Results
- ID:
- ivo://CDS.VizieR/J/A+A/445/465
- Title:
- ATCA 18.5 and 22GHz fluxes of Kuehr 5GHz sample
- Short Name:
- J/A+A/445/465
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We discuss our ATCA 18.5 and 22GHz flux density measurements of Southern extragalactic sources in the complete 5GHz sample of Kuehr et al. (1981, Cat. <VIII/5>). The high frequency (5-18.5GHz) spectral indices of steep-spectrum sources for which we have 18.5GHz data (66% of the complete sample) are systematically steeper than the low frequency (2.7-5GHz) ones, and there is evidence of an anti-correlation of high-frequency spectral index with luminosity. The completeness of 18.5GHz data is much higher (89%) for flat-spectrum sources (mostly quasars), which also exhibit a spectral steepening. Taking advantage of the almost complete redshift information on flat-spectrum quasars, we have estimated their 5GHz luminosity function in several redshift bins. The results confirm that their radio luminosity density peaks at z_peak about 2.5 but do not provide evidence for deviations from pure luminosity evolution as hinted at by other data sets. A comparison of our 22GHz flux densities with WMAP K-band data for flat-spectrum sources suggests that WMAP flux densities may be low by a median factor of about 1.2. The extrapolations of 5GHz counts and luminosity functions of flat-spectrum radio quasars using the observed distribution of the 5-18.5GHz spectral indices match those derived directly from WMAP data, indicating that the high frequency WMAP survey does not detect any large population of FSRQs with anomalous spectra.
- ID:
- ivo://CDS.VizieR/VIII/63
- Title:
- ATESP radio survey. II.
- Short Name:
- VIII/63
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The ATESP survey is a radio survey accomplished with the Australia Telescope Compact Array (ATCA) at 1.4 GHz over a region of 26 square degrees centered at -40 and ranging in RA from 22h30m to 01h15m. The survey consists of 16 radio mosaics with 8x14 arcsec resolution and uniform sensitivity (1 sigma noise = 79 microJy). The final 6 sigmas catalogue contains 2960 sources down to a detection limit of 0.5 mJy. This region is superposed to the redshift survey ESO Slice Project (ESP) and is partly covered by the EIS survey (Patch A; see Cat. J/A+AS/130/323). Table 3 summarizes the main parameters for the final 16 mosaics: for each mosaic are listed the number of fields composing it (columns x rows), the tangent point (sky position used for geometry calculations) and the synthesized beam (size and position angle). The spatial resolution can vary from mosaic to mosaic depending on the particular array (6A, 6C or 6D) used in the observations. The mean value for the synthesized beam is 8"x14". The last three columns of Table 3 show the results of the noise analysis. For each mosaic we report the minimum (negative) flux (S_min) recorded on the image (typically |S_min| is of the order of 0.5 mJy, corresponding to the value at which we have stopped the cleaning) and the noise level. This has been evaluated either as the FWHM of the Gaussian fit to the flux distribution of the pixels (in the range +/-S_min), in order to check for correlated noise (sigma_fit), or as the standard deviation of the average flux in several source-free sub-regions of the mosaics, in order to verify uniformity (<sigma>).
- ID:
- ivo://CDS.VizieR/J/MNRAS/476/2717
- Title:
- AT20G-MWACS catalogue
- Short Name:
- J/MNRAS/476/2717
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a new broad-band radio frequency catalogue across 0.12GHz<={nu}<=20GHz created by combining data from the Murchison Widefield Array Commissioning Survey, the Australia Telescope 20GHz survey, and the literature. Our catalogue consists of 1285 sources limited by S_20GHz_>40mJy at 5{sigma}, and contains flux density measurements (or estimates) and uncertainties at 0.074, 0.080, 0.119, 0.150, 0.180, 0.408, 0.843, 1.4, 4.8, 8.6, and 20GHz. We fit a second-order polynomial in log-log space to the spectral energy distributions of all these sources in order to characterize their broad-band emission. For the 994 sources that are well described by a linear or quadratic model we present a new diagnostic plot arranging sources by the linear and curvature terms. We demonstrate the advantages of such a plot over the traditional radio colour-colour diagram. We also present astrophysical descriptions of the sources found in each segment of this new parameter space and discuss the utility of these plots in the upcoming era of large area, deep, broad-band radio surveys.
- ID:
- ivo://CDS.VizieR/J/MNRAS/417/2651
- Title:
- AT20G-optical catalogue
- Short Name:
- J/MNRAS/417/2651
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Our current understanding of radio-loud active galactic nuclei (AGN) comes predominantly from studies at frequencies of 5GHz and below. With the recent completion of the Australia Telescope 20GHz (AT20G) survey, we can now gain insight into the high-frequency radio properties of AGN. This paper presents supplementary information on the AT20G sources in the form of optical counterparts and redshifts. Optical counterparts were identified using the SuperCOSMOS data base and redshifts were found from either the 6dF Galaxy Survey or the literature. We also report 144 new redshifts. For AT20G sources outside the Galactic plane, 78.5% have optical identifications and 30.9% have redshift information. The optical identification rate also increases with increasing flux density. Targets which had optical spectra available were examined to obtain a spectral classification.
- ID:
- ivo://CDS.VizieR/J/MNRAS/473/4523
- Title:
- ATLAS/FUSION SWIRE CDFS and ELAIS-S1 fields
- Short Name:
- J/MNRAS/473/4523
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Cross-identifying complex radio sources with optical or infrared (IR) counterparts in surveys such as the Australia Telescope Large Area Survey (ATLAS) has traditionally been performed manually. However, with new surveys from the Australian Square Kilometre Array Pathfinder detecting many tens of millions of radio sources, such an approach is no longer feasible. This paper presents new software (LRPY - Likelihood Ratio in PYthon) to automate the process of cross-identifying radio sources with catalogues at other wavelengths. lrpy implements the likelihood ratio (LR) technique with a modification to account for two galaxies contributing to a sole measured radio component. We demonstrate lrpy by applying it to ATLAS DR3 and a Spitzer-based multiwavelength fusion catalogue, identifying 3848 matched sources via our LR-based selection criteria. A subset of 1987 sources have flux density values for all IRAC bands which allow us to use criteria to distinguish between active galactic nuclei (AGNs) and star-forming galaxies (SFG). We find that 936 radio sources (~=47 per cent) meet both of the Lacy and Stern AGN selection criteria. Of the matched sources, 295 have spectroscopic redshifts and we examine the radio to IR flux ratio versus redshift, proposing an AGN selection criterion below the Elvis radio-loud AGN limit for this dataset. Taking the union of all three AGNs selection criteria we identify 956 as AGNs (~= 48 per cent). From this dataset, we find a decreasing fraction of AGNs with lower radio flux densities consistent with other results in the literature.
- ID:
- ivo://CDS.VizieR/J/MNRAS/453/4020
- Title:
- ATLAS 1.4GHz Data Release 3
- Short Name:
- J/MNRAS/453/4020
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the third data release from the Australia Telescope Large Area Survey. These data combine the observations at 1.4GHz before and after upgrades to the Australia Telescope Compact Array reaching a sensitivity of 14{mu}Jy/beam in 3.6 deg^2^ over the Chandra Deep Field South (CDFS) and of 17{mu}Jy/beam in 2.7 deg^2^ over the European Large Area ISO Survey South 1 (ELAIS-S1). We used a variety of array configurations to maximize the uv coverage resulting in a resolution of 16 by 7-arcsec in CDFS and of 12 by 8-arcsec in ELAIS-S1. After correcting for peak bias and bandwidth smearing, we find a total of 3034 radio source components above 5{sigma} in CDFS, of which 514 (17 per cent) are considered to be extended. The number of components detected above 5{sigma} in ELAIS-S1 is 2084, of which 392 (19 per cent) are classified as extended. The catalogues include reliable spectral indices ({Delta}{alpha}<0.2) between 1.40 and 1.71GHz for ~350 of the brightest components.
- ID:
- ivo://CDS.VizieR/J/A+A/649/A94
- Title:
- A universal pattern in halo magnetic fields
- Short Name:
- J/A+A/649/A94
- Date:
- 22 Feb 2022
- Publisher:
- CDS
- Description:
- Magnetic fields in galaxy halos are in general very difficult to observe. Most recently, the Continuum HAlos in Nearby Galaxies - an EVLA Survey (CHANG-ES) collaboration investigated the radio halos of 35 nearby edge-on spiral galaxies in detail and detected large-scale magnetic fields in 16 of them. We used the CHANG-ES radio polarization data to create rotation measure (RM) maps for all galaxies in the sample and stack them with the aim of amplifying any underlying universal toroidal magnetic field pattern in the halo above and below the disk of the galaxy. We discovered a large-scale magnetic field in the central region of the stacked galaxy profile, which is attributable to an axial electric current that universally outflows from the center, both above and below the plane of the disk. A similar symmetry-breaking has also been observed in astrophysical jets, but never before in galaxy halos. This is an indication that galaxy halo magnetic fields are probably not generated by pure magnetohydrodynamic (MHD) processes in the central regions of galaxies. One such promising physical mechanism is the Cosmic Battery operating in the innermost accretion disk around the central supermassive black hole. We anticipate that our discovery will stimulate a more general discussion on the origin of astrophysical magnetic fields.
- ID:
- ivo://CDS.VizieR/J/MNRAS/415/3831
- Title:
- AzTEC/ASTE source catalogue
- Short Name:
- J/MNRAS/415/3831
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a 0.72deg^2^ contiguous 1.1-mm survey in the central area of the Cosmological Evolution Survey field carried out to a 1{sigma}~1.26mJy/beam depth with the AzTEC camera mounted on the 10-m Atacama Submillimeter Telescope Experiment. We have uncovered 189 candidate sources at a signal-to-noise ratio (S/N)>=3.5, out of which 129, with S/N>=4, can be considered to have little chance of being spurious (<~2 per cent). We present the number counts derived with this survey, which show a significant excess of sources when compared to the number counts derived from the ~0.5deg^2^ area sampled at similar depths in the Submillimetre Common-User Bolometer Array (SCUBA) HAlf Degree Extragalactic Survey (SHADES).
- ID:
- ivo://CDS.VizieR/J/MNRAS/423/529
- Title:
- AzTEC deep-field observations
- Short Name:
- J/MNRAS/423/529
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Instruments using arrays of many bolometers have become increasingly common in the past decade. The maps produced by such instruments typically include the filtering effects of the instrument as well as those from subsequent steps performed in the reduction of the data. Therefore interpretation of the maps is dependent upon accurately calculating the transfer function of the chosen reduction technique on the signal of interest. Many of these instruments use non-linear and iterative techniques to reduce their data because such methods can offer an improved signal-to-noise ratio over those that are purely linear, particularly for signals at scales comparable to that subtended by the array. We discuss a general approach for measuring the transfer function of principal component analysis on point sources that are small compared to the spatial extent seen by any single bolometer within the array. The results are applied to previously released AzTEC catalogues of the Cosmic Evolution Survey (COSMOS), Lockman Hole, Subaru XMM-Newton Deep Field, Great Observatories Origins Deep Survey (GOODS)-North and GOODS-South fields. Source flux density and noise estimates increase by roughly +10 per cent for fields observed while AzTEC was installed at the Atacama Submillimeter Telescope Experiment and +15-25 per cent while AzTEC was installed at the James Clerk Maxwell Telescope. Detection significance is, on average, unaffected by the revised technique. The revised photometry technique will be used in subsequent AzTEC releases.
