- ID:
- ivo://CDS.VizieR/J/ApJ/517/282
- Title:
- Atomic carbon observations of H II regions
- Short Name:
- J/ApJ/517/282
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We report observations of atomic carbon (C I [^3^P - ^3^P_0_]) for a sample of 49 southern hemisphere H II regions using the Antarctic Submillimeter Telescope and Remote Observatory. The sources are compact and isolated members of the Wilson et al. (1970) H109{alpha} radio recombination line (RRL) catalog. The fourth Galactic quadrant is well covered by the sample. Atomic carbon emission is detected toward all of the regions, with multiple C I emission components found toward most sources. The RRL velocity is used to identify the C I emission associated with the H II region. We measure the mean velocity difference between the C I and RRL emission to be 0.8{+/-}2.8 km s^-1^. Within the measurement errors this is exact agreement in velocity; we conclude that all H II regions have associated C I emission. The mean C I line temperature of these components is 2.4{+/-}1.8 K, compared with 0.7{+/-}0.7 K for the C I emission components not associated with the H II region. This suggests that C I intensity is dominated by local heating. The FWHM line width of C I gas associated with H II regions also is marginally greater than that found for unassociated gas (6.7{+/-}3.0, compared with 4.8{+/-}2.4 km s-1).
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Search Results
- 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/402/2403
- Title:
- Australia Telescope 20GHz Survey Catalog, AT20G
- Short Name:
- J/MNRAS/402/2403
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The Australia Telescope 20GHz Survey (AT20G) is a blind radio survey carried out at 20GHz with the Australia Telescope Compact Array (ATCA) from 2004 to 2008, and covers the whole sky south of declination 0{deg}. The AT20G source catalogue presented here is an order of magnitude larger than any previous catalogue of high-frequency radio sources, and includes 5890 sources above a 20GHz flux-density limit of 40mJy. All AT20G sources have total intensity and polarisation measured at 20GHz, and most sources south of declination -15{deg} also have near-simultaneous flux-density measurements at 5 and 8GHz. A total of 1559 sources were detected in polarised total intensity at one or more of the three frequencies.
- ID:
- ivo://CDS.VizieR/J/MNRAS/426/3334
- Title:
- Australia Telescope Large Area Survey
- Short Name:
- J/MNRAS/426/3334
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The Australia Telescope Large Area Survey (ATLAS) has surveyed 7 square degrees of sky around the Chandra Deep Field South and the European Large Area ISO Survey-South 1 fields at 1.4GHz. ATLAS aims to reach a uniform sensitivity of 10uJy/beam rms over the entire region with first data release currently reaching ~30uJy/beam rms. Here we present 466 new spectroscopic redshifts for radio sources in ATLAS as part of our optical follow-up programme. Of the 466 radio sources with new spectroscopic redshifts, 142 have star-forming optical spectra, 282 show evidence for active galactic nuclei (AGN) in their optical spectra, 10 have stellar spectra and 32 have spectra revealing redshifts, but with insufficient features to classify.
- ID:
- ivo://CDS.VizieR/J/ApJ/762/16
- Title:
- Australia Telescope Low-brightness Survey (ATLBS)
- Short Name:
- J/ApJ/762/16
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The Australia Telescope Low-brightness Survey (ATLBS) regions have been mosaic imaged at a radio frequency of 1.4GHz with 6" angular resolution and 72{mu}Jy/beam rms noise. The images (centered at RAJ2000=00:35:00, DEJ2000=-67:00:00 and RAJ2000=00:59:17, DEJ2000=-67:00:00) cover 8.42deg^2^ sky area and have no artifacts or imaging errors above the image thermal noise. Multi-resolution radio and optical r-band images (made using the 4m CTIO Blanco telescope) were used to recognize multi-component sources and prepare a source list; the detection threshold was 0.38mJy in a low-resolution radio image made with beam FWHM of 50". Radio source counts in the flux density range 0.4-8.7mJy are estimated, with corrections applied for noise bias, effective area correction, and resolution bias. The resolution bias is mitigated using low-resolution radio images, while effects of source confusion are removed by using high-resolution images for identifying blended sources. Below 1mJy the ATLBS counts are systematically lower than the previous estimates. Showing no evidence for an upturn down to 0.4mJy, they do not require any changes in the radio source population down to the limit of the survey. The work suggests that automated image analysis for counts may be dependent on the ability of the imaging to reproduce connecting emission with low surface brightness and on the ability of the algorithm to recognize sources, which may require that source finding algorithms effectively work with multi-resolution and multi-wavelength data. The work underscores the importance of using source lists --as opposed to component lists-- and correcting for the noise bias in order to precisely estimate counts close to the image noise and determine the upturn at sub-mJy flux density.
- ID:
- ivo://CDS.VizieR/J/MNRAS/422/1527
- Title:
- Australia Telescope PMN follow-up survey
- Short Name:
- J/MNRAS/422/1527
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a source catalogue derived from high-resolution observations of a selection of PMN sources with the Australia Telescope Compact Array (ATCA). The catalogue lists 8385 sources with flux-density measurements at 4.8 and 8.6GHz, derived from observations of all fields in the declination range -87{deg}<DE<-38.5{deg} (exclusive of galactic latitudes |b|<2{deg{) with PMN flux-density S_4850_>70mJy (50mJy south of DE=-73{deg}). We assess the quality of the data, which was gathered in 1992-1994, and the resulting source parameters. We describe the population of catalogued sources, and compare it to samples from complementary catalogues. In particular we find 126 radio sources with probable association with gamma-ray sources observed by the orbiting Fermi Large Area Telescope.
- ID:
- ivo://CDS.VizieR/J/AJ/104/704
- Title:
- A VLA Search for Young Galactic Supernova Remnants
- Short Name:
- J/AJ/104/704
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- In the attempt to identify very young galactic supernova remnants (SNRs), 290 known compact (<2') galactic plane radio sources were observed at 20cm using the VLA in its 36 km configuration. The VLA observations described could detect supernovae with diameters between 5 and 20"; these would have an age of between 25 and 100 yr. Compact structure was detected in 168 (58%) of the 290 different sources observed; 73 sources (25%) were unresolved or slightly resolved point sources, 21 (7%) were single-well resolved, 56 (19%) were double, 18 (6%) were triple or complex. The large scale structure was completely resolved out for 122 (42%) of sources. Additional observations at 6cm with the VLA in the 11 km configuration were made of 14 sources with apparent shell structures that might have been characteristic of young SNRs. Low resolution observations were made at 20cm of 62 fields where the source was completely resolved out in the high resolution images. Only one source, G25.5+0.2, is a possible very young SNR. New H66_alpha recombination line observations place severe constrains on any thermal interpretation for this object.
- ID:
- ivo://CDS.VizieR/J/AJ/154/252
- Title:
- A VLA survey of magnetic CVs. I. The data
- Short Name:
- J/AJ/154/252
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The Jansky Very Large Array was used to observe 121 magnetic cataclysmic variables (MCVs). We report radio detections of 18 stars. Thirteen are new radio sources, increasing the number of MCVs that are radio sources by more than twofold, from 8 to 21. Most detections are at 8.7 GHz (X-band) with a lesser number at 5.4 and 21.1 GHz (C- and K-bands). With the exception of AE Aqr, whose flux density is typically >5 mJy, the flux densities are in the range of 24-780 {mu}Jy. Thirteen of the detections show highly circularly polarized emission, which is characteristic of electron-cyclotron maser emission. The data suggest that MCVs could possibly be divided into two classes of radio emitters: those dominated by weakly polarized gyrosynchrotron emission and those by highly polarized electron-cyclotron maser emission.
- ID:
- ivo://CDS.VizieR/J/MNRAS/426/1845
- Title:
- AzTEC survey of the SHADES fields. II.
- Short Name:
- J/MNRAS/426/1845
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The Astronomical Thermal Emission Camera (AzTEC) 1.1mm survey of the two SCUBA HAlf Degree Extragalactic Survey (SHADES) fields is the largest (0.7deg^2^) blank-field millimetre-wavelength (mm-wavelength) survey undertaken to date at a resolution of 18arcsec and a depth of 1mJy. We have used the deep optical to radio multiwavelength data in the SHADES Lockman Hole East and SXDF/UDS fields to obtain galaxy identifications for 64 per cent (80 per cent including tentative identifications) of the 148 AzTEC-SHADES 1.1mm sources reported by Austermann et al., exploiting deep radio and 24um data complemented by methods based on 8um flux density and red optical-infrared (i-K) colour.
- ID:
- ivo://CDS.VizieR/J/PASP/132/K4102
- Title:
- Beamed and unbeamed emission of gamma-ray blazars
- Short Name:
- J/PASP/132/K4102
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- A two-component model of radio emission has been used to explain some radio observational properties of Active Galactic Nuclei (AGNs) and, in particular, of blazars. In this work, we extend the two-component idea to the {gamma}-ray emission and assume that the total {gamma}-ray output of blazars consists of relativistically beamed and unbeamed components. The basic idea leverages the correlation between the radio core-dominance parameter and the {gamma}-ray beaming factor. To do so, we evaluate this correlation for a large sample of 584 blazars taken from the fourth source catalog of the Fermi Large Area Telescope (Fermi-LAT) and correlated their {gamma}-ray core-dominance parameters with radio core-dominance parameters. The {gamma}-ray beaming factor is then used to estimate the beamed and unbeamed components. Our analysis confirms that the {gamma}-ray emission in blazars is mainly from the beamed component.