- 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/318/333
- Title:
- Extended ROSAT Bright Cluster Sample
- Short Name:
- J/MNRAS/318/333
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a low-flux extension of the X-ray-selected ROSAT Brightest Cluster Sample (BCS) published in Paper I of this series. Like the original BCS and employing an identical selection procedure, the BCS extension is compiled from ROSAT All-Sky Survey (RASS) data in the northern hemisphere ({delta}>=0{deg}) and at high Galactic latitudes (|b|>=20{deg}). It comprises 99 X-ray-selected clusters of galaxies with measured redshifts z<=0.3 (as well as eight more at z>0.3) and total fluxes between 2.8x10^-12^ and 4.4x10^-12^erg/cm^2^/s in the 0.1-2.4keV band (the latter value being the flux limit of the original BCS). The extension can be combined with the main sample published in 1998 to form the homogeneously selected extended BCS (eBCS), the largest and statistically best understood cluster sample to emerge from the RASS to date. The nominal completeness of the combined sample (defined with respect to a power-law fit to the bright end of the BCS logN-logS distribution) is relatively low at 75per cent (compared with 90per cent for the high-flux sample of Paper I). However, just as for the original BCS, this incompleteness can be accurately quantified, and thus statistically corrected for, as a function of X-ray luminosity and redshift. In addition to its importance for improved statistical studies of the properties of clusters in the local Universe, the low-flux extension of the BCS is also intended to serve as a finding list for X-ray-bright clusters in the northern hemisphere which we hope will prove useful in the preparation of cluster observations with the next generation of X-ray telescopes such as Chandra and XMM-Newton.
- ID:
- ivo://CDS.VizieR/J/MNRAS/452/1171
- Title:
- Extended X-ray sources in CFHTLenS footprint
- Short Name:
- J/MNRAS/452/1171
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The chameleon gravity model postulates the existence of a scalar field that couples with matter to mediate a fifth force. If it exists, this fifth force would influence the hot X-ray emitting gas filling the potential wells of galaxy clusters. However, it would not influence the clusters weak lensing signal. Therefore, by comparing X-ray and weak lensing profiles, one can place upper limits on the strength of a fifth force. This technique has been attempted before using a single, nearby cluster (Coma, z=0.02). Here we apply the technique to the stacked profiles of 58 clusters at higher redshifts (0.1<z<1.2), including 12 new to the literature, using X-ray data from the XMM Cluster Survey and weak lensing data from the Canada-France-Hawaii-Telescope Lensing Survey. Using a multiparameter Markov chain Monte Carlo analysis, we constrain the two chameleon gravity parameters ({beta} and {phi}_{inf}_). Our fits are consistent with general relativity, not requiring a fifth force. In the special case of f_R_ gravity (where {beta}=sqrt(1/6)), we set an upper limit on the background field amplitude today of |f_R0_|<6x10^-5^ (95 percent CL). This is one of the strongest constraints to date on |f_R0_| on cosmological scales. We hope to improve this constraint in future by extending the study to hundreds of clusters using data from the Dark Energy Survey.
- ID:
- ivo://CDS.VizieR/J/A+AS/135/571
- Title:
- Extragalactic radio sources polarization
- Short Name:
- J/A+AS/135/571
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present linear polarization measurements of 154 extragalactic radio sources at {lambda}6.3cm, as part of a continuing effort to expand and improve our Faraday rotation determinations of radio galaxies and quasars. The excellent telescope optics of the Effelsberg 100 m telescope at this wavelength, combined with a matrix method we applied for calibrating out all components of the instrumental polarization enables us to achieve better than average accuracy in the determinations of linear polarization degree and position angle. In the absence of thermal noise errors, these are repeatable to better than 0.2% and 0.1{deg} respectively, for the prime calibrator, 3C 286.
- ID:
- ivo://CDS.VizieR/J/MNRAS/436/718
- Title:
- Extremely faint planetary nebulae in SDSS
- Short Name:
- J/MNRAS/436/718
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Using ~1700000 target- and sky-fibre spectra from the Sloan Digital Sky Survey (SDSS), we have carried out a systematic search for Galactic planetary nebulae (PNe) via detections of the [OIII] {lambda}{lambda}4959, 5007 lines. Thanks to the excellent sensitivity of the SDSS spectroscopic surveys, this is by far the deepest search for PNe ever taken, reaching a surface brightness of the [OIII] {lambda}5007 line down to about 29.0mag/arcsec^2^. The search leads to the recovery of 13 previously known PNe in the Northern and Southern Galactic Caps. In total, 44 new PN candidates are identified, including seven candidates of multiple detections and 37 candidates of single detection. The seven candidates of multiple detections are all extremely large (between 21 and 154arcmin) and faint, located mostly in the low Galactic latitude region and with a kinematics similar to disc stars. After checking their images in H{alpha} and other bands, three of them are probably HII regions, one is probably associated with a new supernova remnant, another one is possibly a true PN and the remaining two could be either PNe or supernova remnants. Based on sky positions and kinematics, seven candidates of single detection probably belong to the halo population. If confirmed, they will increase the number of known PNe in the Galactic halo significantly. All the newly identified PN candidates are very faint, with a surface brightness of the [OIII] {lambda}5007 line between 27.0-30.0mag/arcsec^2^, and very challenging to be discovered with previously employed techniques (e.g. slitless spectroscopy, narrow-band imaging), and thus may greatly increase the number of `missing' faint PNe. Our results demonstrate the power of large-scale fibre spectroscopy in hunting for ultrafaint PNe and other types of emission line nebulae. Combining the large spectral data bases provided by the SDSS and other on-going projects (e.g. the LAMOST Galactic surveys), it is possible to build a statistically meaningful sample of ultrafaint, large, evolved PNe, thus, improving the census of Galactic PNe.
- ID:
- ivo://CDS.VizieR/J/MNRAS/235/827
- Title:
- Faint galaxy redshift survey
- Short Name:
- J/MNRAS/235/827
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Using the fibre optic coupler at the Anglo-Australian Observatory, we have completed a new faint galaxy redshift survey. Intermediate dispersion spectra with resolution ~4{AA} have been gathered for over 200 field galaxies selected in apparent magnitude slices between 20.0<b_J_<21.5mag in five high-latitude fields. Redshift completeness is 85% and the mean redshift agrees well from field to field.
- ID:
- ivo://CDS.VizieR/J/MNRAS/352/1245
- Title:
- Faint 1.4GHz radio sources in 2dFGRS
- Short Name:
- J/MNRAS/352/1245
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have used the Australia Telescope Compact Array (ATCA) to search for faint radio sources in a ~3deg^2^ region of sky covered by the 2dF Galaxy Redshift Survey (2dFGRS, Cat. <VII/226>). Over the region surveyed, the 1{sigma} noise level at 1.4GHz ranges from 20Jy to 1mJy. The survey region includes 365 2dFGRS galaxies, of which 316 have good-quality spectra (176 early-type galaxies or active galactic nuclei, and 140 star-forming galaxies). The fraction of 2dFGRS galaxies detected as radio sources in our survey rises from ~4% at a 3{sigma} detection limit of 0.3mJy to 12% at 75{mu}Jy, with roughly equal numbers of star-forming galaxies and active galactic nuclei (AGNs) being detected.
- ID:
- ivo://CDS.VizieR/J/MNRAS/451/4193
- Title:
- Fermi/non-Fermi blazars jet power and accretion
- Short Name:
- J/MNRAS/451/4193
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We study the relationship between jet power and accretion for Fermi and non-Fermi blazars. We also compare the relevant parameter. Our main results are: (i) Fermi and non-Fermi blazars have significant differences in red shift, black hole mass and broad line luminosity. (ii) Fermi blazars have a higher average core-dominance parameter than non-Fermi blazars, which suggests that Fermi blazars have a strong beaming effect. (iii) We find a significant correlation between broad line emission and jet power for Fermi and non-Fermi blazars, which suggests a direct tight connection between jet and accretion. (iv) The accretion and black hole mass may have a different contribution to jet power for Fermi and non-Fermi blazars.
- ID:
- ivo://CDS.VizieR/J/MNRAS/393/1467
- Title:
- Field early-type galaxies at 0.2<z<0.8
- Short Name:
- J/MNRAS/393/1467
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We explore the properties of 24 field early-type galaxies in the redshift range 0.20<z<0.75 down to M_B<=-19.30 in a sample extracted from the FORS Deep Field and the William Herschel Deep Field. Target galaxies were selected on the basis of a combination of luminosity, spectrophotometric type, morphology and photometric redshift or broad-band colours. High signal-to-noise intermediate-resolution spectroscopy has been acquired at the Very Large Telescope, complemented by deep high-resolution imaging with the Advanced Camera for Surveys onboard the HST and additional ground-based multi-band photometry. All galaxy spectra were observed under sub-arcsecond conditions and allow to derive accurate kinematics and stellar population properties of the galaxies. To clarify the low level of star formation detected in some galaxies, we identify the amount of active galactic nuclei (AGN) activity in our sample using archive data of Chandra and XMM-Newton X-ray surveys. None of the galaxies in our sample were identified as secure AGN sources based on their X-ray emission. The rest-frame B and K-band scaling relations of the Faber-Jackson relation and the Fundamental Plane display a moderate evolution for the field early-type galaxies. Lenticular (S0) galaxies feature on average a stronger luminosity evolution and bluer rest-frame colours which can be explained that they comprise more diverse stellar populations compared to elliptical galaxies. The evolution of the FP can be interpreted as an average change in the dynamical (effective) mass-to-light ratio of our galaxies as <{Delta}log(M/L_B_)/z>=-0.74+/-0.08. The M/L evolution of these field galaxies suggests a continuous mass assembly of field early-type galaxies during the last 5Gyr, that gets support by recent studies of field galaxies up to z~1. Independent evidence for recent star formation activity is provided by spectroscopic (OII emission, Hdelta) and photometric (rest-frame broad-band colors) diagnostics. Based on the Hdelta absorption feature we detect a weak residual star formation for galaxies that accounts for 5%-10% in the total stellar mass of these galaxies. The co-evolution in the luminosity and mass of our galaxies favours a downsizing formation process. We find some evidence that our galaxies experienced a period of star formation quenching, possible triggered by AGN activity that is in good agreement with recent results on both observational and theoretical side.
- ID:
- ivo://CDS.VizieR/J/MNRAS/368/1411
- Title:
- Flat-spectrum symmetric radio sources
- Short Name:
- J/MNRAS/368/1411
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The radio sources listed below were selected from the Jodrell-VLA Astrometric Survey and the Cosmic-Lens All-Sky Survey (part 1) and constitute a (non-complete) parent sample for the selection of flat-spectrum symmetric object candidates (the ones which show structure, when their VLA-A 8.4GHz data are analysed). The parent sample contains northern hemisphere objects with 8.4GHz flux densities greater than 100mJy, galactic latitudes greater than 10 degrees and 1.40-to-4.85GHz spectral indices (when known; if not, the source is kept in the sample) smaller than 0.50 (flat). The most relevant properties of the parent sample are listed in the Table.
