- ID:
- ivo://CDS.VizieR/J/MNRAS/439/1212
- Title:
- Deep 20GHz survey of CDFS and SDSS Stripe 82
- Short Name:
- J/MNRAS/439/1212
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a source catalogue and first results from a deep, blind radio survey carried out at 20GHz with the Australia Telescope Compact Array, with follow-up observations at 5.5, 9 and 18GHz. The Australia Telescope 20GHz (AT20G) deep pilot survey covers a total area of 5deg^2^ in the Chandra Deep Field South and in Stripe 82 of the Sloan Digital Sky Survey. We estimate the survey to be 90% complete above 2.5mJy. Of the 85 sources detected, 55percent have steep spectra ({alpha}_1.4_^20^<-0.5) and 45% have flat or inverted spectra ({alpha}_1.4_^20^>=-0.5). The steep-spectrum sources tend to have single power-law spectra between 1.4 and 18GHz, while the spectral indices of the flat- or inverted-spectrum sources tend to steepen with frequency. Among the 18 inverted-spectrum ({alpha}_1.4_^20^>=0.0) sources, 10 have clearly defined peaks in their spectra with {alpha}_1.4_^5.5^>0.15 and {alpha}_9_^18^<-0.15. On a 3-yr time-scale, at least 10 sources varied by more than 15percent at 20GHz, showing that variability is still common at the low flux densities probed by the AT20G-deep pilot survey.
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Search Results
- ID:
- ivo://CDS.VizieR/J/ApJS/150/417
- Title:
- Deep, high-resolution survey at 74MHz
- Short Name:
- J/ApJS/150/417
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a 74MHz survey of a 165deg^2^ region located near the north Galactic pole. This survey has an unprecedented combination of both resolution (25" FWHM) and sensitivity ({sigma} as low as 24mJy/beam). We detect 949 sources at the 5{sigma} level in this region, enough to begin exploring the nature of the 74MHz source population. We present differential source counts, spectral index measurements, and the size distribution as determined from counterparts in the high-resolution FIRST 1.4GHz survey, Cat. <VIII/71>.
- ID:
- ivo://CDS.VizieR/J/MNRAS/391/1384
- Title:
- Deep MERLIN 5GHz radio sources in M82
- Short Name:
- J/MNRAS/391/1384
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The results of an extremely deep, 8-d long observation of the central kpc of the nearby starburst galaxy M82 using Multi-Element Radio Linked Interferometer Network (MERLIN) at 5GHz are presented. The 17{mu}Jy/beam rms noise level in the naturally weighted image makes it the most sensitive high-resolution radio image of M82 made to date. Over 50 discrete sources are detected, the majority of which are supernova remnants, but with 13 identified as H ii regions. Sizes, flux densities and radio brightnesses are given for all of the detected sources, which are all well resolved with a majority showing shell or partial shell structures. Those sources within the sample which are supernova remnants have diameters ranging from 0.3 to 6.7pc, with a mean size of 2.9pc.
- ID:
- ivo://CDS.VizieR/J/MNRAS/383/75
- Title:
- Deep 610MHz survey of ELAIS-N1 sources
- Short Name:
- J/MNRAS/383/75
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Observations of the ELAIS-N1 field taken at 610MHz with the Giant Metrewave Radio Telescope are presented. Nineteen pointings were observed, covering a total area of 9 square degrees with a resolution of 6x5arcsec^2^, PA=45deg. Four of the pointings were deep observations with an rms of ~40uJy before primary beam correction, with the remaining fifteen pointings having an rms of ~70uJy. The techniques used for data reduction and production of a mosaicked image of the region are described, and the final mosaic, along with a catalogue of 2500 sources detected above 6{sigma}, are presented. This work complements the large amount of optical and infrared data already available on the region. For further details of the surveys and data analysis procedures please refer to the published paper.
- ID:
- ivo://CDS.VizieR/J/MNRAS/371/963
- Title:
- Deep VLA survey in Lockman Hole, HDFN, ELAIS N2
- Short Name:
- J/MNRAS/371/963
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present catalogues of faint 1.4-GHz radio sources from extremely deep Very Large Array pointings in the Lockman Hole, the Hubble Deep Field-North (HDF-N) and the European Large Area ISO Survey (ELAIS) N2 field. Our analysis of the HDF-N data has produced maps that are significantly deeper than those previously published, and we have used these to search for counterparts to submillimetre sources. For each of the fields, we have derived normalized differential source counts and in the case of the HDF-N find no evidence for the previously reported underdensity of sources; our counts are entirely consistent with those found for the majority of other fields. The catalogues are available as an online supplement to this paper and the maps are also available for download.
- ID:
- ivo://CDS.VizieR/J/AJ/115/1253
- Title:
- Deep X-Ray Radio Blazar Survey (DXRBS). I.
- Short Name:
- J/AJ/115/1253
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have undertaken a survey, the Deep X-Ray Radio Blazar Survey (DXRBS), of archived, pointed ROSAT Position Sensitive Proportional Counter data for blazars by correlating the ROSAT WGACAT database with several publicly available radio catalogs, restricting our candidate list to serendipitous flat radio spectrum sources ({alpha}_r_<=0.70, where S_{nu}_{prop}{nu}^-{alpha}_r_^). We discuss our survey methods, identification procedure, and first results. Our survey is found to be 95% efficient at finding flat-spectrum radio-loud quasars (FSRQs; 59 of our first 85 identifications) and BL Lacertae objects (22 of our first 85 identifications), a figure that is comparable to or greater than that achieved by other radio and X-ray survey techniques. The identifications presented here show that all previous samples of blazars (even when taken together) did not representatively survey the blazar population, missing critical regions of (LX, LR) parameter space within which large fractions of the blazar population lie. Particularly important is the identification of a large population of FSRQs (>=25% of DXRBS FSRQs) with ratios of X-ray to radio luminosity >=10^-6^({alpha}_rx_<=0.78). In addition, as a result of our greater sensitivity, the DXRBS has already more than doubled the number of FSRQs in complete samples with 5GHz (radio) luminosities between 10^31.5^ and 10^33.5^ergs/s/Hz, and fills in the region of parameter space between X-ray-selected and radio-selected samples of BL Lac objects. The DXRBS is the very first sample to contain statistically significant numbers of blazars at low luminosities, approaching what should be the lower end of the FSRQ luminosity function.
- ID:
- ivo://CDS.VizieR/J/MNRAS/323/757
- Title:
- Deep X-Ray Radio Blazar Survey (DXRBS). II.
- Short Name:
- J/MNRAS/323/757
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have searched the archived, pointed ROSAT Position Sensitive Proportional Counter data for blazars by correlating the WGACAT X-ray data base with several publicly available radio catalogues, restricting our candidate list to serendipitous X-ray sources with a flat radio spectrum ({alpha}_r_<=0.70, where S_{nu}_~{nu}^-{alpha}^). his makes up the Deep X-ray Radio Blazar Survey (DXRBS). Here we present new identifications and spectra for 106 sources, including 86 radio-loud quasars, 11 BL Lacertae objects, and nine narrow-line radio galaxies. Together with our previously published objects and already-known sources, our sample now contains 298 identified objects: 234 radio-loud quasars [181 flat-spectrum quasars: FSRQ ({alpha}_r_<=0.50) and 53 steep-spectrum quasars: SSRQ], 36 BL Lacs and 28 narrow-line radio galaxies. Redshift information is available for 96 per cent of these. Thus our selection technique is ~90 per cent efficient at finding radio-loud quasars and BL Lacs. Reaching 5-GHz radio fluxes ~50mJy and 0.1-2.0keV X-ray fluxes a few W10-14erg/cm^2^/s, DXRBS is the faintest and largest flat-spectrum radio sample with nearly complete (~85 per cent) identification.
- ID:
- ivo://CDS.VizieR/J/ApJ/665/1194
- Title:
- Dense cores in the Orion A cloud survey
- Short Name:
- J/ApJ/665/1194
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have carried out an H^13^CO^+^ (J=1-0) core survey in a large area of 1.5degx0.5deg, covering the whole region of the Orion A molecular cloud, using the Nobeyama 45m radio telescope with the 25 Beam Array Receiver System (BEARS). This survey is unique in that a large area (~48pc^2^) of the cloud was covered with a high spatial resolution of 21" (0.05pc) and with a deep integration (1sigma~0.1K in T*_A_), resulting in a core mass detection of 1.6M_{sun}_. The morphology of the H^13^CO^+^ (J=1-0) emission is very similar to that of the 850um continuum emission. We identified 236 dense cores from our data with the clumpfind algorithm. The cores are close to virial equilibrium, independent of whether they are thermal or turbulent.
- ID:
- ivo://CDS.VizieR/J/ApJ/691/1560
- Title:
- Dense core survey in the Orion B cloud
- Short Name:
- J/ApJ/691/1560
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have carried out an H^13^CO^+^(J=1-0 at 86.75433GHz) core survey in a large area of 1deg^2^, covering most of the dense region in the Orion B molecular cloud, using the Nobeyama 45m radio telescope with the 25-BEam Array Receiver System. We cataloged 151 dense cores using the clumpfind method. The cores have mean radius, velocity width, and mass of 0.10+/-0.02pc, 0.53+/-0.15km/s, and 8.1+/-6.4M_{sun}_, respectively, which are very similar to those in the Orion A cloud. We examined the spatial relation between our H^13^CO^+^ cores and the 850um cores observed by Johnstone and colleagues in 2001 (Cat. J/ApJ/559/307) and 2006 (Cat. J/ApJ/639/259), and found that there are two types of spatial relationships: H^13^CO^+^ cores with and without the 850um cores. Since the mean density of the 850um cores is higher than that of the H^13^CO^+^ cores, we can interpret the H^13^CO^+^ cores with 850um cores as being more centrally concentrated and hence more evolved, compared with those without.
- ID:
- ivo://CDS.VizieR/J/A+AS/124/385
- Title:
- Dense molecular cores. V.
- Short Name:
- J/A+AS/124/385
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present results of the observations of 17 molecular clouds associated with bright FIR sources in the NH_3_ (1, 1) and (2, 2) lines with the 100-m radio telescope in Effelsberg. The lines were detected in 11 clouds and 10 of them have been mapped in these lines. The kinetic temperatures, sizes, masses and mean densities of the ammonia cores have been derived. For most of the detected clouds the masses derived under the assumption of a relative ammonia abundance of {chi}(NH_3_)=3x10^-8^ are close to virial masses. However, in S 88 B the ratio M/M_vir_ is only ~0.1 and in a few other cases this ratio is significantly lower than unity which may indicate ammonia underabundance. Almost all objects with the signs of underabundance are among the most luminous IR sources in our sample. Most of the mapped cores are elongated with noticeable velocity gradients along the major axis. The most prominent example is S 255. S 87 has a two-component structure with 2 distinct velocity components which overlap partly spatially. In about half of the mapped sources the NH_3_ line widths increase near the peaks of the ammonia emission. The kinetic temperatures are centrally peaked. They reach 20-28K in the centre and drop to 15-20K at the edges of the ammonia emitting regions. In S 76 E a weak extended emission in the (1, 1) line at the velocity blue-shifted by ~5km/s relative to the core emission was detected. Hyperfine intensity anomalies in the (1, 1) transition were found in S 199 in addition to the known case of these anomalies in S 87.