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3221. SDSS Luminous Red Galaxies
ID:
ivo://CDS.VizieR/J/MNRAS/377/787
Title:
SDSS Luminous Red Galaxies
Short Name:
J/MNRAS/377/787
Date:
21 Oct 2021
Publisher:
CDS
Description:
The data are taken from the Luminous Red Galaxy sample of the Sloan Digital Sky Survey Data Release 4. From the SDSS spectra we compute the five indices Hbeta, Hgamma_F_, Dn(4000), [MgFe]', [Mg1Fe]'. These are matched indices from a synthetic library of spectra containing 31000 different star formation scenarios. From this we can infer probability distributions for a number of properties, such as age, metallicity, etc. The results are presented here as the 5th, 16th, 50th (median), 86th and 95th percentiles of the relevant distribution. The 4391 LRG properties presented here are chosen from the redshift range 0.15<z<0.4 and require all 5 of the above indices to have well-measured values (i.e. no contamination from skylines, bad pixels) Also given are a number of properties that come directly from the SDSS database, such as redshift, velocity dispersion etc. For the luminosity distance calculation (and subsequent mass estimates), we assume a FRW metric, with omega_m_=0.25, omega_lambda_=0.75 and H_0_=73km/s/Mpc.
3222. SDSS luminous red galaxies concentrations
ID:
ivo://CDS.VizieR/J/ApJ/769/52
Title:
SDSS luminous red galaxies concentrations
Short Name:
J/ApJ/769/52
Date:
21 Oct 2021
Publisher:
CDS
Description:
The best gravitational lenses for detecting distant galaxies are those with the largest mass concentrations and the most advantageous configurations of that mass along the line of sight. Our new method for finding such gravitational telescopes uses optical data to identify projected concentrations of luminous red galaxies (LRGs). LRGs are biased tracers of the underlying mass distribution, so lines of sight with the highest total luminosity in LRGs are likely to contain the largest total mass. We apply this selection technique to the Sloan Digital Sky Survey and identify the 200 fields with the highest total LRG luminosities projected within a 3.5' radius over the redshift range 0.1<=z<=0.7. The redshift and angular distributions of LRGs in these fields trace the concentrations of non-LRG galaxies. These fields are diverse; 22.5% contain one known galaxy cluster and 56.0% contain multiple known clusters previously identified in the literature. Thus, our results confirm that these LRGs trace massive structures and that our selection technique identifies fields with large total masses. These fields contain two to three times higher total LRG luminosities than most known strong-lensing clusters and will be among the best gravitational lensing fields for the purpose of detecting the highest redshift galaxies.
3223. SDSS & MMT obs. of extremely massive QSOs & gal.
ID:
ivo://CDS.VizieR/J/ApJ/871/57
Title:
SDSS & MMT obs. of extremely massive QSOs & gal.
Short Name:
J/ApJ/871/57
Date:
21 Oct 2021
Publisher:
CDS
Description:
Black hole mass scaling relations suggest that extremely massive black holes (EMBHs) with M_BH_>~10^9.4^M_{sun}_ are found in the most massive galaxies with M_star_>~10^11.6^M_{sun}_, which are commonly found in dense environments, like galaxy clusters. Therefore, one can expect that there is a close connection between active EMBHs and dense environments. Here, we study the environments of 9461 galaxies and 2943 quasars at 0.24<~z<~0.40, among which 52 are extremely massive quasars with log(M_BH_/M_{sun}_)>=~9.4, using Sloan Digital Sky Survey and MMT Hectospec data. We find that, on average, both massive quasars and massive galaxies reside in environments more than ~2 times as dense as those of their less massive counterparts with log(M_BH_/M_{sun}_)<~9.0. However, massive quasars reside in environments about ~2 times less dense than inactive galaxies with log(M_BH_/M_{sun}_)>=9.4, and only about one third of massive quasars are found in galaxy clusters, while about two thirds of massive galaxies reside in such clusters. This indicates that massive galaxies are a much better signpost for galaxy clusters than massive quasars. The prevalence of massive quasars in moderate to low density environments is puzzling, considering that several simulation results show that these quasars appear to prefer dense environments. Several possible reasons for this discrepancy are discussed, although further investigation is needed to obtain a definite explanation.
3224. SDSS nearby galaxies morphologies
ID:
ivo://CDS.VizieR/J/MNRAS/446/3749
Title:
SDSS nearby galaxies morphologies
Short Name:
J/MNRAS/446/3749
Date:
21 Oct 2021
Publisher:
CDS
Description:
We investigate box/peanut and bar structures in image data of edge-on and face-on nearby galaxies taken from the Sloan Digital Sky Survey (SDSS) to present catalogues containing the surface brightness parameters and the morphology classification. About 1700 edge-on galaxies and 2600 face-on galaxies are selected from SDSS DR7 in the g, r and i-bands. The images of each galaxy are fitted with the model of two-dimensional surface brightness of the Sersic bulge and exponential disk. After removing some irregular data, the box/peanut, bar and other structures are easily distinguished by eye using residual (observed minus model) images. We find 292 box/peanut structures in the 1329 edge-on samples and 630 bar structures in 1890 face-on samples in the i-band, after removing some irregular data. The fraction of box/peanut galaxies is about 22 per cent against the edge-on samples, and that of bar galaxies is about 33 per cent (about 50 per cent if 629 elliptical galaxies are removed) against the face-on samples. Furthermore the strengths of the box/peanuts and bars are evaluated as strong, standard or weak. We find that the strength increases slightly with increasing B/T (bulge-to-total flux ratio), and that the fraction of box/peanuts is generally about a half of that of bars, irrespective of the strength and B/T. Our result supports the idea that a box/peanut is a bar seen edge-on.
3225. SDSS peculiar galaxy pairs list
ID:
ivo://CDS.VizieR/J/MNRAS/443/3528
Title:
SDSS peculiar galaxy pairs list
Short Name:
J/MNRAS/443/3528
Date:
21 Oct 2021
Publisher:
CDS
Description:
We applied computational tools for automatic detection of peculiar galaxy pairs. We first detected in Sloan Digital Sky Survey DR7 ~400000 galaxy images with i magnitude <18 that had more than one point spread function, and then applied a machine learning algorithm that detected ~26000 galaxy images that had morphology similar to the morphology of galaxy mergers. That data set was mined using a novelty detection algorithm, producing a short list of 500 most peculiar galaxies as quantitatively determined by the algorithm. Manual examination of these galaxies showed that while most of the galaxy pairs in the list were not necessarily peculiar, numerous unusual galaxy pairs were detected. In this paper, we describe the protocol and computational tools used for the detection of peculiar mergers, and provide examples of peculiar galaxy pairs that were detected.
3226. SDSS photometry of HI-selected galaxies
ID:
ivo://CDS.VizieR/J/MNRAS/394/340
Title:
SDSS photometry of HI-selected galaxies
Short Name:
J/MNRAS/394/340
Date:
21 Oct 2021
Publisher:
CDS
Description:
We have used the Parkes Multibeam system and the Sloan Digital Sky Survey to assemble a sample of 195 galaxies selected originally from their HI signature to avoid biases against unevolved or low surface brightness objects. For each source nine intrinsic properties are measured homogeneously, as well as inclination and an optical spectrum. The sample, which should be almost entirely free of either misidentification or confusion, includes a wide diversity of galaxies ranging from inchoate, low surface brightness dwarfs to giant spirals. Despite this diversity there are five clear correlations among their properties. They include a common dynamical mass-to-light ratio within their optical radii, a correlation between surface brightness and luminosity and a common HI surface density. Such correlation should provide strong constrains on models of galaxy formation and evolution.
3227. SDSS photometry of interacting galaxies
ID:
ivo://CDS.VizieR/J/AJ/139/1212
Title:
SDSS photometry of interacting galaxies
Short Name:
J/AJ/139/1212
Date:
21 Oct 2021
Publisher:
CDS
Description:
We have used the Galaxy Evolution Explorer (GALEX) ultraviolet telescope to study stellar populations and star formation morphology in a well-defined sample of 42 nearby optically selected pre-merger interacting galaxy pairs. Galaxy interactions were likely far more common in the early universe than in the present; thus our study provides a nearby well-resolved comparison sample for high-redshift studies. We have combined the GALEX near-ultraviolet (NUV) and far-ultraviolet images with broadband optical maps from the Sloan Digitized Sky Survey to investigate the ages and extinctions of the tidal features and the disks.
3228. SDSS photometry of luminous red galaxies
ID:
ivo://CDS.VizieR/J/MNRAS/387/1323
Title:
SDSS photometry of luminous red galaxies
Short Name:
J/MNRAS/387/1323
Date:
21 Oct 2021
Publisher:
CDS
Description:
We report on the AAT-AAOmega LRG Pilot observing run to establish the feasibility of a large spectroscopic survey using the new AAOmega instrument. We have selected luminous red galaxies (LRGs) using single epoch SDSS riz-photometry to i<20.5 and z<20.2. We have observed in three fields including the COSMOS field and the COMBO-17 S11 field, obtaining a sample of ~600 redshift z>~0.5 LRGs. Exposure times varied from 14h to determine the minimum exposure for AAOmega to make an essentially complete LRG redshift survey in average conditions. We show that LRG redshifts to i<20.5 can be measured in >>1.5h exposures and present comparisons with 2SLAQ and COMBO-17 (photo)redshifts. Crucially, the riz selection coupled with the three to four times improved AAOmega throughput is shown to extend the LRG mean redshift from z=0.55 for 2SLAQ to z=0.681+/-0.005 for riz-selected LRGs. This extended range is vital for maximizing the signal-to-noise ratio for the detection of the baryon acoustic oscillations (BAOs). Furthermore, we show that the amplitude of LRG clustering is s_0_=9.9+/-0.7h^-1^Mpc, as high as that seen in the 2SLAQ LRG Survey. Consistent results for this clustering amplitude are found from the projected and semi-projected correlation functions. This high amplitude is consistent with a long-lived population whose bias evolves as predicted by a simple 'high-peak' model. We conclude that a redshift survey of 360000 LRGs over 3000deg^2^, with an effective volume some four times bigger than previously used to detect BAO with LRGs, is possible with AAOmega in 170 nights.
3229. SDSS post-merger galaxies HI data
ID:
ivo://CDS.VizieR/J/MNRAS/478/3447
Title:
SDSS post-merger galaxies HI data
Short Name:
J/MNRAS/478/3447
Date:
10 Dec 2021 00:08:38
Publisher:
CDS
Description:
We present a detailed assessment of the global atomic hydrogen gas fraction (f_gas_=log[M_HI_/M*) in a sample of post-merger galaxies identified in the Sloan Digital Sky Survey (SDSS). Archival HI measurements of 47 targets are combined with new Arecibo observations of a further 51 galaxies. The stellar mass range of the post-merger sample, our observing strategy, detection thresholds and data analysis procedures replicate those of the extended GALEX Arecibo SDSS Survey (xGASS) which can therefore be used as a control sample. Our principal results are (1) the post-merger sample shows a ~50 per cent higher HI detection fraction compared with xGASS; (2) accounting for non-detections, the median atomic gas fraction of the post-merger sample is larger than the control sample by 0.3-0.6dex; and (3) the median atomic gas fraction enhancement ({Delta}f_gas_), computed on a galaxy-by-galaxy basis at fixed stellar mass, is 0.51dex. Our results demonstrate that recently merged galaxies are typically a factor of ~3 more HI rich than control galaxies of the same M* If the control sample is additionally matched in star formation rate, the median H I excess is reduced to {Delta}f_gas_=0.2dex, showing that the enhanced atomic gas fractions in post-mergers are not purely a reflection of changes in star formation activity. We conclude that merger-induced starbursts and outflows do not lead to prompt quenching via exhaustion/expulsion of the galactic gas reservoirs. Instead, we propose that if star formation ceases after a merger, it is more likely due to an enhanced turbulence which renders the galaxy unable to effectively form new stars.
3230. SDSSRC3 sample morphological classifications
ID:
ivo://CDS.VizieR/J/MNRAS/433/2986
Title:
SDSSRC3 sample morphological classifications
Short Name:
J/MNRAS/433/2986
Date:
21 Oct 2021
Publisher:
CDS
Description:
Galaxies grow primarily via accretion-driven star formation in discs and merger-driven growth of bulges. These processes are implicit in semi-analytical models of galaxy formation, with bulge growth in particular relating directly to the hierarchical build-up of haloes and their galaxies. In this paper, we consider several implementations of two semi-analytical models. Focusing on implementations in which bulges are formed during mergers only, we examine the fractions of elliptical galaxies and both passive and star-forming disc galaxies as functions of stellar and halo mass, for central and satellite systems. This is compared to an observational cross-matched Sloan Digital Sky Survey+Third Reference Catalog of Bright Galaxies z~0 sample of galaxies with accurate visual morphological classifications and M*>10^10.5^M_{sun}_. The models qualitatively reproduce the observed increase of elliptical fraction with stellar mass, and with halo mass for central galaxies, supporting the idea that observed ellipticals form during major mergers. However, the overall elliptical fraction produced by the models is much too high compared with the z~0 data. Since the 'passive' - i.e. non-star-forming - fractions are approximately reproduced, and since the fraction which are star-forming disc galaxies is also reproduced, the problem is that the models overproduce ellipticals at the expense of passive S0 and spiral galaxies. Bulge growth implementations (tuned to reproduce simulations) which allow the survival of residual discs in major mergers still destroy too much of the disc. Increasing the lifetime of satellites, or allowing significant disc regrowth around merger remnants, merely increases the fraction of star-forming disc galaxies. Instead, it seems necessary to reduce the mass ratios of merging galaxies, so that most mergers produce modest bulge growth in disc galaxy remnants instead of ellipticals. This could be a natural consequence of tidal stripping of stars from infalling satellite galaxies, a process not considered in our models. However, a high efficiency of quenching during and/or subsequent to minor mergers is still required to keep the passive fraction high.

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