- ID:
- ivo://CDS.VizieR/J/A+A/418/1
- Title:
- Radio continuum spectra in Virgo cluster region
- Short Name:
- J/A+A/418/1
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- New radio continuum observations of galaxies in the Virgo cluster region at 4.85, 8.6, and 10.55GHz are presented. These observations are combined with existing measurements at 1.4 and 0.6GHz. The sample includes 81 galaxies where spectra with more than two frequencies could be derived. Galaxies that show a radio-FIR excess exhibit central activity (HII, LINER,AGN). The four Virgo galaxies with the highest absolute radio excess are found within 2 degrees of the center of the cluster. Galaxies showing flat radio spectra also host active centers. There is no clear trend between the spectral index and the galaxy's distance to the cluster center.
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Search Results
- ID:
- ivo://CDS.VizieR/J/A+AS/111/311
- Title:
- Radio continuum study of the MC
- Short Name:
- J/A+AS/111/311
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- From observations with the Parkes radio telescope, we present catalogues of radio sources in the Large Magellanic Cloud at four frequencies: 1.40, 2.45, 4.75 and 8.55GHz, and an additional catalogue from a source analysis of the Parkes-MIT-NRAO survey at 4.85GHz. A total of 469 sources have been detected at least one of these frequencies, 132 of which are reported here for the first time as radio sources.
- ID:
- ivo://CDS.VizieR/J/A+AS/127/119
- Title:
- Radio continuum study of the MC
- Short Name:
- J/A+AS/127/119
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- By comparing Parkes telescope radio surveys with the X-ray ROSAT All-Sky Survey (RASS) we have found 71 discrete sources of both radio and X-ray emission in the Large Magellanic Cloud (LMC). These 71 sources are mainly supernova remnants (SNRs) and SNR candidates (36), and background sources (27). For six of the sources we have no proposed identification and the other two are HII regions. A source-intensity comparison of the radio and X-ray sources shows very little correlation, but we note that the strongest SNRs at both radio and X-ray frequencies are young SNRs from Population I. Six new LMC SNR candidates are proposed. From the radio flux density of the SNRs we have estimated the SNR birth rate to be one every 100 (+/-20) yr and the star-formation rate (SFR) to be 0.7 (+/-0.2)M_{sun}_/yr. A similar comparison was undertaken for the Small Magellanic Cloud (SMC), but instead of the RASS we used a roster of pointed observations made with the ROSAT Position Sensitive Proportional Counter (PSPC). This comparison resulted in 27 sources in common between the Parkes radio and ROSAT PSPC surveys. Two new SMC sources are proposed for SNR candidates. The SMC SNR birth rate was estimated to be one every 350 (+/-70)yr and the SFR was estimated to be 0.15 (+/-0.05)M_{sun}_/yr.
- ID:
- ivo://CDS.VizieR/J/A+AS/130/421
- Title:
- Radio continuum study of the MC
- Short Name:
- J/A+AS/130/421
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a study of discrete radio sources in the Magellanic Clouds (MCs) using the latest large-scale radio surveys made with the Parkes radio telescope between 1.4 and 8.55GHz. These surveys achieved higher sensitivity than previous surveys done with the Parkes telescope and so the number of discrete radio sources detected towards the MCs has increased by factor of five. Also, we have obtained improved positions, flux densities and radio spectral indices for all of these sources. A total of 483 sources towards the Large Magellanic Cloud (LMC) and 224 towards the Small Magellanic Cloud (SMC) have been detected at at least one radio frequency. Most of the MC's sources have been classified in one of three groups: SNRs, HII regions or background sources according to classification criteria established here. In total, 209 discrete radio sources in the LMC and the 37 sources in the SMC are classified here to be either HII regions or SNRs. We investigate their luminosity functions as well as the statistics of background sources behind the MCs. Also, we examine the distribution of SNRs and HII regions in the MCs.
- ID:
- ivo://CDS.VizieR/J/A+AS/120/77
- Title:
- Radio continuum study of the MC
- Short Name:
- J/A+AS/120/77
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a new catalogue of radio sources in the Large Magellanic Cloud (LMC) based on observations at 2.30GHz with the Parkes radio telescope. A total of 119 sources have been detected. We compare positions and flux densities of these sources with previously published radio results and find no significant positional displacement or flux discrepancies.
- ID:
- ivo://CDS.VizieR/J/AJ/152/82
- Title:
- Radio continuum survey of Kepler K2 mission Field 1
- Short Name:
- J/AJ/152/82
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the first dedicated radio continuum survey of a Kepler K2 mission field, Field 1, covering the North Galactic Cap. The survey is wide field, contemporaneous, multi-epoch, and multi-resolution in nature and was conducted at low radio frequencies between 140 and 200MHz. The multi-epoch and ultra wide field (but relatively low resolution) part of the survey was provided by 15 nights of observation using the Murchison Widefield Array (MWA) over a period of approximately a month, contemporaneous with K2 observations of the field. The multi-resolution aspect of the survey was provided by the low resolution (4') MWA imaging, complemented by non-contemporaneous but much higher resolution (20'') observations using the Giant Metrewave Radio Telescope (GMRT). The survey is, therefore, sensitive to the details of radio structures across a wide range of angular scales. Consistent with other recent low radio frequency surveys, no significant radio transients or variables were detected in the survey. The resulting source catalogs consist of 1085 and 1468 detections in the two MWA observation bands (centered at 154 and 185MHz, respectively) and 7445 detections in the GMRT observation band (centered at 148MHz), over 314 square degrees. The survey is presented as a significant resource for multi-wavelength investigations of the more than 21000 target objects in the K2 field. We briefly examine our survey data against K2 target lists for dwarf star types (stellar types M and L) that have been known to produce radio flares.
- ID:
- ivo://CDS.VizieR/J/A+A/472/785
- Title:
- Radio continuum survey of M33
- Short Name:
- J/A+A/472/785
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We study the exponential scale length of total radio emission, the spectral index distribution, and the linear radio polarization in the Scd galaxy M33. Observations were carried out using the 3.6cm dual channel and the 6.2cm four-channel receivers of the 100-m Effelsberg telescope along with the L-band VLA D-array at 20cm. High spatial resolution and sensitivity in both total and linearly polarized radio continuum emission from M33 were achieved. We found considerable extended emission, not only from the main arms IS and IN, but also from the weaker arms. The large-scale magnetic field exhibits well-ordered spiral structure with almost the same orientation as that of the optical spiral arms; however, it does not show a clear structural correlation or anti-correlation with the optical arms. There is a north-south asymmetry in polarization that is frequency-dependent. We found that the ring mean spectral index versus radius increases faster beyond R=4kpc. At each wavelength, the exponential scale length is larger inside than outside R=4kpc. From the larger scale lengths at R<4kpc, we conclude that star-forming regions are mainly spread over the region R<4kpc without a dominant nuclear concentration. Furthermore, at R>4kpc, a spatial correlation between cosmic rays and star-forming regions may exist. From the behavior of the mean spectral indices obtained from different pairs of the radio continuum data at 3.6, 6.2, and 20cm, we confirm that a decrease in the thermal fraction causes an increase in the spectral index.
- ID:
- ivo://CDS.VizieR/J/A+A/608/A21
- Title:
- Radio cubes of G82.65-2.00
- Short Name:
- J/A+A/608/A21
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The combination of line and continuum observations can provide vital insight into the formation and fragmentation of filaments and the initial conditions for star formation. We have carried out line observations to map the kinematics of an evolved, actively star forming filament G82.65-2.00. The filament was first identified from the Planck data as a region of particularly cold dust emission and was mapped at 100-500m as a part of the Herschel key program Galactic Cold Cores. The Herschel observations cover the central part of the filament, corresponding to a filament length of ~12pc at the assumed distance of 620pc. CO observations show that the filament has an intriguing velocity field with several velocity components around the filament. In this paper, we study the velocity structure in detail, to quantify possible mass accretion rate onto the filament, and study the masses of the cold cores located in the filament. We have carried out line observations of several molecules, including CO isotopologues, HCO^+^, HCN, and CS with the Osaka 1.85m telescope and the Nobeyama 45m telescope. The spectral line data are used to derive velocity and column density information.
- ID:
- ivo://CDS.VizieR/J/A+A/482/247
- Title:
- Radio detections of 3G sources
- Short Name:
- J/A+A/482/247
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- A considerable fraction of the gamma-ray sources discovered with the Energetic Gamma-Ray Experiment Telescope (EGRET) remain unidentified. The EGRET sources that have been properly identified are either pulsars or variable sources at both radio and gamma-ray wavelengths. Most of the variable sources are strong radio blazars. However, some low galactic-latitude EGRET sources, with highly variable gamma-ray emission, lack any evident counterpart according to the radio data available until now. The primary goal of this paper is to identify and characterise the potential radio counterparts of four highly variable gamma-ray sources in the galactic plane through mapping the radio surroundings of the EGRET confidence contours and determining the variable radio sources in the field whenever possible. We have carried out a radio exploration of the fields of the selected EGRET sources using the Giant Metrewave Radio Telescope (GMRT) interferometer at 21 cm wavelength, with pointings being separated by months.
- ID:
- ivo://CDS.VizieR/J/A+A/373/1032
- Title:
- Radio emission from planetary nebulae
- Short Name:
- J/A+A/373/1032
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have analysed the radio fluxes for 264 planetary nebulae for which reliable measurements of fluxes at 1.4 and 5 GHz, and of nebular diameters are available. For many of the investigated nebulae, the optical thickness is important, especially at 1.4 GHz. Simple models like the one specified only by a single optical thickness or spherical, constant density shells do not account satisfactorily for the observations. Also an r^-2^ density distribution is ruled out. A reasonable representation of the observations can be obtained by a two-component model having regions of two different values of optical thickness. We show that the nebular diameters smaller than 10" are uncertain, particularly if they come from photographic plates or Gaussian fitting to the radio profile. While determining the interstellar extinction from an optical to radio flux ratio, caution should be paid regarding optical thickness effects in the radio. We have developed a method for estimating the value of self absorption. At 1.4 GHz self absorption of the flux is usually important and can exceed a factor of 10. At 5 GHz self absorption is negligible for most of the objects, although in some cases it can reach a factor of 2. The Galactic bulge planetary nebulae when used to calibrate the Shklovsky method give a mean nebular mass of 0.14M_{sun}_. The statistical uncertainty of the Shklovsky distances is smaller than a factor of 1.5.
