- ID:
- ivo://CDS.VizieR/J/MNRAS/449/1536
- Title:
- New damped Ly{alpha} absorbers
- Short Name:
- J/MNRAS/449/1536
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Quasar damped Ly{alpha} (DLA) absorption-line systems with redshifts z<1.65 are used to trace neutral gas over approximately 70 percent of the most recent history of the Universe. However, such systems fall in the UV and are rarely found in blind UV spectroscopic surveys. Therefore, it has been difficult to compile a moderate-sized sample of UV DLAs in any narrow cosmic time interval. However, DLAs are easy to identify in low-resolution spectra because they have large absorption rest equivalent widths. We have performed an efficient strong-Mg ii-selected survey for UV DLAs at redshifts z=[0.42,0.70] using Hubble Space Telescope's low-resolution ACS-HRC-PR200L prism. This redshift interval covers ~1.8Gyr in cosmic time, i.e. t~[7.2,9.0]Gyr after the big bang. A total of 96 strong MgII absorption-line systems identified in Sloan Digital Sky Survey spectra were successfully observed with the prism at the predicted UV wavelengths of Ly{alpha} absorption. We found that 35 of the 96 systems had a significant probability of being DLAs. One additional observed system could be a very high N_HI_ DLA (N_HI_~2x10^22^atoms/cm^2^ or possibly higher), but since very high N_HI_ systems are extremely rare, it would be unusual for this system to be a DLA given the size of our sample. Here we present information on our prism sample, including our best estimates of N_HI_ and errors for the 36 systems fitted with DLA profiles. This list is valuable for future follow-up studies of low-redshift DLAs in a small redshift interval, although such work would clearly benefit from improved UV spectroscopy to more accurately determine their neutral hydrogen column densities.
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Search Results
- ID:
- ivo://CDS.VizieR/J/MNRAS/430/1746
- Title:
- 90 new SNIa from SDSS DR7
- Short Name:
- J/MNRAS/430/1746
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Using a method to discover and classify supernovae (SNe) in galaxy spectra, we find 90 Type Ia SNe (SNe Ia) and 10 Type II SNe among the ~700000 galaxy spectra in the Sloan Digital Sky Survey Data Release 7 that have star-formation histories (SFHs) derived with the VErsatile SPectral Analysis code (VESPA). We use the SN Ia sample to measure SN Ia rates per unit stellar mass.
- ID:
- ivo://CDS.VizieR/J/MNRAS/391/369
- Title:
- New z>=3.6 QSOs from FIRST-SDSS DR5
- Short Name:
- J/MNRAS/391/369
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We aim to obtain a complete sample of redshift z>=3.6 radio quasi-stellar objects (QSOs) from the Faint Images of the Radio Sky at Twenty cm survey (FIRST) sources (S_1.4GHz_>1mJy) having star-like counterparts in the Sloan Digital Sky Survey (SDSS) Data Release 5 (DR5) photometric survey (r_AB_<=20.2). Our starting sample of 8665 FIRST-DR5 pairs includes 4250 objects with spectra in DR5, 52 of these being z>=3.6 QSOs. We found that simple supervised neural networks, trained on the sources with DR5 spectra, and using optical photometry and radio data, are very effective for identifying high-z QSOs in a sample without spectra. For the sources with DR5 spectra the technique yields a completeness (fraction of actual high-z QSOs classified as such by the neural network) of 96 per cent, and an efficiency (fraction of objects selected by the neural network as high-z QSOs that actually are high-z QSOs) of 62 per cent. Applying the trained networks to the 4415 sources without DR5 spectra we found 58 z>=3.6 QSO candidates. We obtained spectra of 27 of them, and 17 are confirmed as high-z QSOs. Spectra of 13 additional candidates from the literature and from SDSS Data Release 6 (DR6) revealed seven more z>=3.6 QSOs, giving an overall efficiency of 60 per cent (24/40).
- ID:
- ivo://CDS.VizieR/J/A+AS/119/499
- Title:
- NGC 628 and companions photometric distances
- Short Name:
- J/A+AS/119/499
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Based on photometry of the brightest blue stars we derived distance moduli for NGC 628 and its dwarf irregular companions: DDO 13, UGC 1171, UGC 1104, and K 10. The mean modulus of the group is estimated to be 29.46 mag with a formal (internal) error of 0.11. The total mass to luminosity ratio of 40M_{sun}_/L_{sun}_ seems sufficient for NGC 628 to keep its companions in bound orbits.
- ID:
- ivo://CDS.VizieR/J/MNRAS/384/1502
- Title:
- NIR photometry of X-ray luminous BCGs
- Short Name:
- J/MNRAS/384/1502
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We investigate the near-infrared evolution of brightest cluster galaxies (BCGs) from a sample of rich galaxy clusters since z~1. By employing an X-ray selection of LX>10^44^erg/s, we limit environmental effects by selecting BCGs in comparably high-density regions. We find a positive relationship between X-ray and near-infrared luminosity for BCGs in clusters with LX>5x10^44^erg/s. Applying a correction for this relation, we reduce the scatter in the BCG absolute magnitude by a factor of 30 per cent. The near-infrared J-K colour evolution demonstrates that the stellar population in BCGs has been in place since at least z=2, and that we expect a shorter period of star formation than that predicted by current hierarchical merger models. We also confirm that there is a relationship between 'blue' J-K colour and the presence of BCG emission lines associated with star formation in cooling flows.
- ID:
- ivo://CDS.VizieR/J/MNRAS/385/2097
- Title:
- NUV-J colours of red-sequence galaxies
- Short Name:
- J/MNRAS/385/2097
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present GALEX near-ultraviolet (NUV) and Two-Micron All-Sky Survey J-band photometry for red-sequence galaxies in local clusters. We define quiescent samples according to a strict emission threshold, removing galaxies with very recent star formation. We analyse the NUVJ colour-magnitude relation (CMR) and find that the intrinsic scatter is an order of magnitude larger than for the analogous optical CMR (~0.35 rather than 0.05mag), in agreement with previous studies. Comparing the NUVJ colours with spectroscopically derived stellar population parameters, we find a strong (>5.5sigma) correlation with metallicity, only a marginal trend with age, and no correlation with the alpha/Fe ratio. We explore the origin of the large scatter and conclude that neither aperture effects nor the UV upturn phenomenon contribute significantly. We show that the scatter could be attributed to simple 'frosting' by either a young or a low-metallicity subpopulation.
237. NVSS radio quasars
- ID:
- ivo://CDS.VizieR/J/other/AcApS/20.366
- Title:
- NVSS radio quasars
- Short Name:
- J/other/AcApS/20
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have searched 11304 quasars from the NVSS catalog for radio emission and obtained 2626 positive detections, of which 301 are new radio detections. We made statistical studies of the radio spectral index, radio luminosity and the fraction of radio-loud quasars versus absolute B magnitude and redshift. We found that the fraction rises between M_B_=-22 and -30 and that it increases at z=0.0 until z=0.8, then goes down at z=1.5. The degree of polarization shows no dependence on redshift.
- ID:
- ivo://CDS.VizieR/J/MNRAS/460/1758
- Title:
- Optical emission lines in galaxy cluster cores 1
- Short Name:
- J/MNRAS/460/1758
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present an Integral Field Unit survey of 73 galaxy clusters and groups with the VIsible Multi Object Spectrograph on the Very Large Telescope. We exploit the data to determine the H{alpha} gas dynamics on kpc scales to study the feedback processes occurring within the dense cluster cores. We determine the kinematic state of the ionized gas and show that the majority of systems (~2/3) have relatively ordered velocity fields on kpc scales that are similar to the kinematics of rotating discs and are decoupled from the stellar kinematics of the brightest cluster galaxy. The majority of the H{alpha} flux (>50 per cent) is typically associated with these ordered kinematics and most systems show relatively simple morphologies suggesting they have not been disturbed by a recent merger or interaction. Approximately 20 per cent of the sample (13/73) have disturbed morphologies which can typically be attributed to active galactic nuclei activity disrupting the gas. Only one system shows any evidence of an interaction with another cluster member. A spectral analysis of the gas suggests that the ionization of the gas within cluster cores is dominated by non-stellar processes, possibly originating from the intracluster medium itself.
- ID:
- ivo://CDS.VizieR/J/other/PABei/30.106
- Title:
- Optical identification of ROSAT AGN
- Short Name:
- J/other/PABei/30
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The completeness of sample is especially important for the research of quasar and using data in one wavelength, such as in radio, infrared, optical or X-ray selection, to make candidate selection always suffers significant selection effect to some extent. Fortunately, some large area surveys have become increasingly prevalent across all wavelengths over the past decade, such as SDSS, NVSS, FIRST, RASS, etc. These surveys make it possible to select candidates in multiple wavelengths and the resulting sample is more complete.
- ID:
- ivo://CDS.VizieR/J/A+AS/115/11
- Title:
- Optical identifications of radio sources
- Short Name:
- J/A+AS/115/11
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- CCD images of the fields of 115 radio sources from the 1Jy, S4 and S5 catalogues are presented. New optical counterparts have been found for a total of 34 sources, a large fraction of which had as yet only been described as empty fields on Sky Survey Plates. Of the 54 radio sources with previously published identifications, 50 optical counterparts have been confirmed while for 4 sources new identifications are proposed. R band magnitudes, derived from the CCD images, are provided for all but a few identified optical counterparts. The fields at the positions of 27 radio sources are still empty down to a limiting magnitude of at least m_R_=22mag, requiring much deeper optical as well as additional infrared images for establishing their optical counterparts.
