- ID:
- ivo://CDS.VizieR/J/MNRAS/434/2877
- Title:
- Extended radio sources in ATLBS
- Short Name:
- J/MNRAS/434/2877
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a study of the environments of extended radio sources in the Australia Telescope Low-Brightness Survey (ATLBS). The radio sources were selected from the ATLBS Extended Source Sample, which is a well defined sample containing the most extended of radio sources in the ATLBS sky survey regions. The environments were analysed using 4-m Cerro-Tololo Inter-American Observatory Blanco telescope observations carried out for ATLBS fields in the Sloan Digital Sky Survey r' band. We have estimated the properties of the environments using smoothed density maps derived from galaxy catalogues constructed using these optical imaging data. The angular distribution of galaxy density relative to the axes of the radio sources has been quantified by defining anisotropy parameters that are estimated using a new method presented here. Examining the anisotropy parameters for a subsample of extended double radio sources that includes all sources with pronounced asymmetry in lobe extents, we find good evidence for environmental anisotropy being the dominant cause for lobe asymmetry in that higher galaxy density occurs almost always on the side of the shorter lobe, and this validates the usefulness of the method proposed and adopted here. The environmental anisotropy parameters have been used to examine and compare the environments of Fanaroff-Riley Class I (FRI) and Fanaroff-Riley Class II (FRII) radio sources in two redshift regimes (z<0.5 and z>0.5). Wide-angle tail sources and head-tail sources lie in the most overdense environments. The head-tail source environments (for the HT sources in our sample) display dipolar anisotropy in that higher galaxy density appears to lie in the direction of the tails. Excluding the head-tail and wide-angle tail sources, subsamples of FRI and FRII sources from the ATLBS appear to lie in similar moderately overdense environments, with no evidence for redshift evolution in the regimes studied herein.
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Search Results
- ID:
- ivo://CDS.VizieR/J/MNRAS/453/4244
- Title:
- Faint radio source population at 15.7GHz
- Short Name:
- J/MNRAS/453/4244
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- A complete, flux density limited sample of 96 faint (>0.5mJy) radio sources is selected from the 10C survey at 15.7GHz in the Lockman Hole. We have matched this sample to a range of multi-wavelength catalogues, including Spitzer Extragalactic Representative Volume Survey, Spitzer Wide-area Infrared Extragalactic survey, United Kingdom Infrared Telescope Infrared Deep Sky Survey and optical data; multi-wavelength counterparts are found for 80 of the 96 sources and spectroscopic redshifts are available for 24 sources. Photometric redshifts are estimated for the sources with multi-wavelength data available; the median redshift of the sample is 0.91 with an interquartile range of 0.84. Radio-to-optical ratios show that at least 94 per cent of the sample are radio loud, indicating that the 10C sample is dominated by radio galaxies. This is in contrast to samples selected at lower frequencies, where radio-quiet AGN and star-forming galaxies are present in significant numbers at these flux density levels. All six radio-quiet sources have rising radio spectra, suggesting that they are dominated by AGN emission. These results confirm the conclusions of that the faint, flat-spectrum sources which are found to dominate the 10C sample below ~1mJy are the cores of radio galaxies. The properties of the 10C sample are compared to the Square Kilometre Array Design Studies Simulated Skies; a population of low-redshift star-forming galaxies predicted by the simulation is not found in the observed sample.
- ID:
- ivo://CDS.VizieR/J/AJ/131/1216
- Title:
- Faint radio sources in the CDF-S ACS field
- Short Name:
- J/AJ/131/1216
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present optical and X-ray identifications for the 64 radio sources in the Great Observatories Origins Deep Survey (GOODS) in Chandra Deep Field-South Advanced Camera for Surveys (ACS) field revealed in the Australia Telescope Compact Array 1.4GHz survey of the Chandra Deep Field-South. Optical identifications are made using the ACS images and catalogs, while the X-ray view is provided by the Chandra X-Ray Observatory 1Ms observations. Redshifts for the identified sources are drawn from publicly available catalogs of spectroscopic observations and multiband photometric-based estimates. Using this multiwavelength information we provide a first characterization of the faint radio source population in this region.
- ID:
- ivo://CDS.VizieR/J/ApJ/806/52
- Title:
- 8 Fermi GRB afterglows follow-up
- Short Name:
- J/ApJ/806/52
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The Fermi Gamma-ray Space Telescope has greatly expanded the number and energy window of observations of gamma-ray bursts (GRBs). However, the coarse localizations of tens to a hundred square degrees provided by the Fermi GRB Monitor instrument have posed a formidable obstacle to locating the bursts' host galaxies, measuring their redshifts, and tracking their panchromatic afterglows. We have built a target-of-opportunity (TOO) mode for the intermediate Palomar Transient Factory (iPTF) in order to perform targeted searches for Fermi afterglows. Here, we present the results of one year of this program: 8 afterglow discoveries out of 35 searches. Two of the bursts with detected afterglows (GRBs 130702A and 140606B) were at low redshift (z=0.145 and 0.384, respectively) and had spectroscopically confirmed broad-line Type Ic supernovae. We present our broadband follow-up including spectroscopy as well as X-ray, UV, optical, millimeter, and radio observations. We study possible selection effects in the context of the total Fermi and Swift GRB samples. We identify one new outlier on the Amati relation. We find that two bursts are consistent with a mildly relativistic shock breaking out from the progenitor star rather than the ultra-relativistic internal shock mechanism that powers standard cosmological bursts. Finally, in the context of the Zwicky Transient Facility, we discuss how we will continue to expand this effort to find optical counterparts of binary neutron star mergers that may soon be detected by Advanced LIGO and Virgo.
- ID:
- ivo://CDS.VizieR/J/A+AS/131/197
- Title:
- F, G and K stars BVRI photometry
- Short Name:
- J/A+AS/131/197
- Date:
- 15 Dec 2021 08:12:40
- Publisher:
- CDS
- Description:
- We present accurate BV(RI)c photometry for a sample of F, G and K stars detected in selected areas of the ROSAT all-sky survey (RASS). We have used the photometry, in addition to low-resolution spectroscopy, to estimate spectral classifications, distances and X-ray luminosities. The log(L_X_/L_V_) in the sample lies below -2. Although the sample contains also nearby, inactive stars, it is dominated by active objects. The median X-ray luminosity in our sample is <L_X_>=29.88 and the mean value of the hardness ratios <HR1>=0.13+/-0.35. We compare the derived X-ray luminosity function with similar functions obtained from the serendipitous samples of the Einstein Observatory medium sensitivity survey (EMSS, Cat. <IX/15>) and EXOSAT (Cat. <J/A+AS/115/41>). Our sample is completely consistent with the EMSS sample of solar type stars, indicating that both our sources and the EMSS sources are representative of the high galactic latitude X-ray stellar population. We do not find extremely active stars (log(L_X_)>=32), as are found in the EMSS sample, and we argue that these objects are rare.
- ID:
- ivo://CDS.VizieR/J/MNRAS/370/1034
- Title:
- FIRST-APM-SDSS survey for high-z radio QSOs
- Short Name:
- J/MNRAS/370/1034
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We selected from the VLA FIRST survey a sample of 94 objects with star-like counterparts in the Sloan Digital Sky Survey (SDSS), and with APM POSS-I colour O-E>=2, i.e. consistent with their being high-redshift quasars. 78 of the 94 candidates can be classified spectroscopically on the basis of either published data (mainly SDSS) or the observations presented here. The fractions of QSOs (51 out of 78) and redshift z>3 QSOs (23 out of 78, 29 per cent) are comparable to those found in other photometric searches for high-redshift QSOs. We confirm that selecting colour O-E>=2 ensures inclusion of all QSOs with 3.7<=z<=4.4. The fraction of 2<=z<=4.4 QSOs with broad absorption lines (BALs) is 27+/-10 per cent (7/26) and the estimated BAL fraction for radio-loud QSOs is at least as high as for optically selected QSOs (~13 per cent). Both the high BAL fraction and the high fraction of low-ionization BALs among BALs (four to five out of seven) in our sample, compared to previous work, are likely due to the red colour selection O-E>=2.
- ID:
- ivo://CDS.VizieR/J/ApJ/757/51
- Title:
- FIRST-2MASS dust-reddened QSO spectra
- Short Name:
- J/ApJ/757/51
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a sample of 120 dust-reddened quasars identified by matching radio sources detected at 1.4GHz in the Faint Images of the Radio Sky at Twenty Centimeters survey (FIRST) with the near-infrared Two Micron All Sky Survey catalog (2MASS) and color-selecting red sources. Optical and/or near-infrared spectroscopy provide broad wavelength sampling of their spectral energy distributions that we use to determine their reddening, characterized by E(B-V). We demonstrate that the reddening in these quasars is best described by Small-Magellanic-Cloud-like dust. This sample spans a wide range in redshift and reddening (0.1<~z<~3, 0.1<~E(B-V)<~1.5), which we use to investigate the possible correlation of luminosity with reddening. At every redshift, dust-reddened quasars are intrinsically the most luminous quasars. We interpret this result in the context of merger-driven quasar/galaxy co-evolution where these reddened quasars are revealing an emergent phase during which the heavily obscured quasar is shedding its cocoon of dust prior to becoming a "normal" blue quasar. When correcting for extinction, we find that, depending on how the parent population is defined, these red quasars make up <~15%-20% of the luminous quasar population. We estimate, based on the fraction of objects in this phase, that its duration is 15%-20% as long as the unobscured, blue quasar phase.
- ID:
- ivo://CDS.VizieR/J/ApJ/607/60
- Title:
- FIRST-2MASS faint sources
- Short Name:
- J/ApJ/607/60
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have constructed a sample of bright near-infrared sources that are detected at radio wavelengths but undetected on the first-generation Palomar Observatory Sky Survey (POSSI) plates in order to search for a population of dust-obscured quasars. Optical and infrared spectroscopic follow-up of the sample has led to the discovery of 17 heavily reddened quasars (B-K>6.5), 14 of which are reported here for the first time. This has allowed us to define a region in the R-K, J-K color plane in which 50% of the radio-selected objects are highly reddened quasars. We compare the surface density of this previously overlooked population to that of ultraviolet-excess radio-selected quasars, finding that they make up ~20% of the total quasar population for K<~15.5.
- ID:
- ivo://CDS.VizieR/J/ApJ/667/673
- Title:
- FIRST-2MASS red quasar survey
- Short Name:
- J/ApJ/667/673
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Combining radio observations with optical and infrared color selection, demonstrated in our pilot study to be an efficient selection algorithm for finding red quasars, we have obtained optical and infrared spectroscopy for 120 objects in a complete sample of 156 candidates from a sky area of 2716deg^2^.
- ID:
- ivo://CDS.VizieR/J/AJ/130/1977
- Title:
- FIRST-Optical-VLA survey for lensed radio lobes
- Short Name:
- J/AJ/130/1977
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present results from a survey for gravitationally lensed radio lobes. Lensed lobes are a potentially richer source of information about galaxy mass distributions than lensed point sources, which have been the exclusive focus of other recent surveys. Our approach is to identify radio lobes in the Faint Images of the Radio Sky at Twenty cm (FIRST, Cat. <VIII/71>) catalog and then search optical catalogs for coincident foreground galaxies, which are candidate lensing galaxies. We then obtain higher resolution images of these targets at both optical and radio wavelengths and obtain optical spectra for the most promising candidates. We present maps of several radio lobes that are nearly coincident with galaxies. We have not found any new and unambiguous cases of gravitational lensing. One radio lobe in particular, FOV J0743+1553, has two hot spots that could be multiple images produced by a z=0.19 spiral galaxy, but the lensing interpretation is problematic.
