- ID:
- ivo://CDS.VizieR/J/A+AS/116/43
- Title:
- Emission-line galaxies nearby voids.
- Short Name:
- J/A+AS/116/43
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the observational results of our search for emission-line galaxies (ELG) towards nearby voids. In order to find ELG, we started a survey using the IIIa-J objective prism plates from the Hamburg QSO Survey. The plates are digitized and an automatic procedure was applied to select the candidates. Digitized direct plates were used to determine coordinates and to reject overlaps between spectra. The accuracy of the coordinates is +/-2". A total area of 1248deg^2^ was scanned, distributed in four different regions. All the selected objects were observed with follow-up spectroscopy. We have obtained a final sample of 203 objects, of which 196 are emission-line galaxies, four are galaxies with absorption lines and three are QSOs. Almost half of our objects are newly discovered ones and three quarters of the given redshifts are new. Our sample contains mainly high ionization galaxies and is less sensitive in the detection of low-ionization objects. The apparent magnitudes, as derived from the objective prism plates, range between 15.0<=B<=19.5. The sample is dominated by nearby galaxies, with a peak in the redshift distribution at cz=4500 km/s.
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Search Results
- ID:
- ivo://CDS.VizieR/J/A+AS/137/83
- Title:
- ESO Imaging Survey. VII.
- Short Name:
- J/A+AS/137/83
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- In this paper the list of candidate clusters identified from the I-band images of the ESO Imaging Survey (EIS) is completed using the data obtained over a total area of about 12 square degrees (EIS Patches C and D). 248 new cluster candidates are presented. Together with the data reported earlier the total I-band coverage of EIS is 17 square degrees, which has yielded a sample of 302 cluster candidates with estimated redshift in the range 0.2<=z<=1.3 and a median redshift of z=0.5. This is the largest optically-selected sample currently available in the Southern Hemisphere. It is also well distributed in the sky thus providing targets for a variety of VLT programs nearly year round.
- ID:
- ivo://CDS.VizieR/J/MNRAS/275/1102
- Title:
- Evolution of quasar luminosity function
- Short Name:
- J/MNRAS/275/1102
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- In an earlier paper (Hawkins & Veron, 1993MNRAS.260..202H) we presented quasar luminosity functions in three redshift bins, derived from a variability selected sample. Here we provide a major extension to this survey, with a view to improving statistics and completeness, and extending the redshift range. The luminosity functions for redshifts of less than 2.2 show a featureless power law of the form {phi}=10^{beta}(M-M_0_)^, with no sign of a 'break'. The quasar luminosity function is also derived by the redshift range 2.2<z<3.2, which again shows a featureless power law, but with a steeper slope. When the data are combined with a new sample of bright quasars, the quasar luminosity functions in all four redshift ranges are consistent with a single power law of index {beta}=0.63. Plots of quasar space density as a function of redshift in three luminosity bins are also presented and show strong evolution at low redshift but nearly constant space density beyond a redshift of 2.
- 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.
- 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/464/3431
- Title:
- Extremely red quasars in BOSS
- Short Name:
- J/MNRAS/464/3431
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Red quasars are candidate young objects in an early transition stage of massive galaxy evolution. Our team recently discovered a population of extremely red quasars (ERQs) in the Baryon Oscillation Spectroscopic Survey (BOSS) that has a suite of peculiar emission-line properties including large rest equivalent widths (REWs), unusual 'wingless' line profiles, large NV/Ly{alpha}, NV/CIV, SiIV/CIV and other flux ratios, and very broad and blueshifted [OIII] {lambda}5007. Here we present a new catalogue of CIV and NV emission-line data for 216188 BOSS quasars to characterize the ERQ line properties further. We show that they depend sharply on UV-to-mid-IR colour, secondarily on REW(CIV), and not at all on luminosity or the Baldwin Effect. We identify a 'core' sample of 97 ERQs with nearly uniform peculiar properties selected via i-W3>=4.6(AB) and REW(CIV)>=100{AA} at redshifts 2.0-3.4. A broader search finds 235 more red quasars with similar unusual characteristics. The core ERQs have median luminosity <logL(ergs/s)>~47.1, sky density 0.010deg^-2^, surprisingly flat/blue UV spectra given their red UV-to-mid-IR colours, and common outflow signatures including BALs or BAL-like features and large CIV emission-line blueshifts. Their SEDs and line properties are inconsistent with normal quasars behind a dust reddening screen. We argue that the core ERQs are a unique obscured quasar population with extreme physical conditions related to powerful outflows across the line-forming regions. Patchy obscuration by small dusty clouds could produce the observed UV extinctions without substantial UV reddening.
- 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.
