- ID:
- ivo://CDS.VizieR/J/MNRAS/474/1873
- Title:
- Classification of LAMOST DR4 galaxies
- Short Name:
- J/MNRAS/474/1873
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We study the classification and composite spectra of galaxies in the fourth data release (DR4) of the Large Sky Area Multi-Object Fibre Spectroscopic Telescope (LAMOST). We select 40182 spectra of galaxies from LAMOST DR4, which have photometric information but no spectroscopic observations in the Sloan Digital Sky Survey (SDSS). These newly observed spectra are recalibrated and classified into six classes - passive, H{alpha}-weak, star-forming, composite, LINER and Seyfert - using the line intensity (H{beta}, [OIII] 5007, H{alpha} and [NII] 6585). We also study the correlation between spectral class and morphological type through three parameters: concentration index, (u-r) colour and D4000n index. We calculate composite spectra of high signal-to-noise ratio (S/N) for six spectral classes and, using these composites, we pick out some features that can differentiate the classes effectively, including H{beta}, Fe5015, H{gamma}A, HK and the Mg2 band. In addition, we compare our composite spectra with the SDSS ones and analyse their differences. A galaxy catalogue of 40182 newly observed spectra (36601 targets) and the composite spectra of the six classes are available online (http://sciwiki.lamost.org/downloads/wll).
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Search Results
- ID:
- ivo://CDS.VizieR/J/AJ/131/1674
- Title:
- Close binary systems from SDSS DR4
- Short Name:
- J/AJ/131/1674
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a spectroscopic sample of 746 detached close binary systems from the Sloan Digital Sky Survey (SDSS) Fourth Data Release (2006ApJS..162...38A). The majority of these binaries consist of a white dwarf primary and a low-mass secondary (typically M dwarf) companion. We have determined the temperature and gravity for 496 of the white dwarf primaries and the spectral type and magnetic activity properties for 661 of the low-mass secondaries. We have estimated the distances for each of the white dwarf-main-sequence star binaries and use white dwarf evolutionary grids to establish the age of each binary system from the white dwarf cooling times.
- ID:
- ivo://CDS.VizieR/J/ApJS/199/34
- Title:
- Clusters of galaxies in SDSS-III
- Short Name:
- J/ApJS/199/34
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Using the photometric redshifts of galaxies from the Sloan Digital Sky Survey III (SDSS-III), we identify 132684 clusters in the redshift range of 0.05<=z<0.8. Monte Carlo simulations show that the false detection rate is less than 6% for the whole sample. The completeness is more than 95% for clusters with a mass of M_200_>1.0x10^14^M_{sun}_ in the redshift range of 0.05<=z<0.42, while clusters of z>0.42 are less complete and have a biased smaller richness than the real one due to incompleteness of member galaxies. We compare our sample with other cluster samples, and find that more than 90% of previously known rich clusters of 0.05<=z<0.42 are matched with clusters in our sample. Richer clusters tend to have more luminous brightest cluster galaxies (BCGs). Correlating with X-ray and the Planck data, we show that the cluster richness is closely related to the X-ray luminosity, temperature, and Sunyaev-Zel'dovich measurements. Comparison of the BCGs with the SDSS luminous red galaxy (LRG) sample shows that 25% of LRGs are BCGs of our clusters and 36% of LRGs are cluster member galaxies. In our cluster sample, 63% of BCGs of r_petro_<19.5 satisfy the SDSS LRG selection criteria.
- ID:
- ivo://CDS.VizieR/J/AJ/142/126
- Title:
- CN and CH in SDSS Galactic globular clusters
- Short Name:
- J/AJ/142/126
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a homogeneous survey of the CN and CH band strengths in eight Galactic globular clusters observed during the course of the Sloan Extension for Galactic Understanding and Exploration sub-survey (SEGUE) of the Sloan Digital Sky Survey. We confirm the existence of a bimodal CN distribution among red giant branch (RGB) stars in all of the clusters with metallicity greater than [Fe/H]=-1.7; the lowest metallicity cluster with an observed CN bimodality is M53, with [Fe/H]~=-2.1. There is also some evidence for individual CN groups on the subgiant branches of M92, M2, and M13, and on the RGBs of M92 and NGC 5053. Finally, we quantify the correlation between overall cluster metallicity and the slope of the CN band strength-luminosity plot as a means of further demonstrating the level of CN enrichment in cluster giants. Our results agree well with previous studies reported in the literature.
- ID:
- ivo://CDS.VizieR/J/ApJ/766/109
- Title:
- Color/age/metallicity gradients of E galaxies
- Short Name:
- J/ApJ/766/109
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- In order to understand the past merging history of elliptical galaxies, we studied the optical-near-infrared (NIR) color gradients of 204 elliptical galaxies. These galaxies are selected from the overlap region of the Sloan Digital Sky Survey (SDSS) Stripe 82 and the UKIRT Infrared Deep Sky Survey (UKIDSS) Large Area Survey (LAS). The use of optical and NIR data (g, r, and K) provides large wavelength baselines, and breaks the age-metallicity degeneracy, allowing us to derive age and metallicity gradients. The use of the deep SDSS Stripe 82 images makes it possible for us to examine how the color/age/metallicity gradients are related to merging features. We find that the optical-NIR color and the age/metallicity gradients of elliptical galaxies with tidal features are consistent with those of relaxed ellipticals, suggesting that the two populations underwent a similar merging history on average and that mixing of stars was more or less completed before the tidal features disappeared. Elliptical galaxies with dust features have steeper color gradients than the other two types, even after masking out dust features during the analysis, which can be due to a process involving wet merging. More importantly, we find that the scatter in the color/age/metallicity gradients of the relaxed and merging feature types decreases as their luminosities (or masses) increase at M>10^11.4^M_{sun}_ but stays large at lower luminosities. Mean metallicity gradients appear nearly constant over the explored mass range, but a possible flattening is observed at the massive end.
- ID:
- ivo://CDS.VizieR/J/A+A/423/755
- Title:
- Color-Induced Displacement double stars in SDSS
- Short Name:
- J/A+A/423/755
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We report the first successful application of the astrometric color-induced displacement technique (CID, the displacement of the photocenter between different band-passes dur to a varying contribution of differently colored components to the total light), originally proposed by Wielen (1996A&A...314..679W) for discovering unresolved binary stars.
- ID:
- ivo://CDS.VizieR/J/AJ/139/1808
- Title:
- Colors and kinematics of SDSS L dwarfs
- Short Name:
- J/AJ/139/1808
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a sample of 484 L dwarfs, 210 of which are newly discovered from the Sloan Digital Sky Survey (SDSS) Data Release 7 spectroscopic database. We combine this sample with known L dwarfs to investigate their izJHKS colors. We present photometric distance relations based on i-z and i-J colors and derive distances to our L dwarf sample. We combine the distances with SDSS/2MASS proper motions in order to examine the tangential velocities.
- ID:
- ivo://CDS.VizieR/J/AJ/137/4436
- Title:
- Coma cluster VLA survey
- Short Name:
- J/AJ/137/4436
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present deep 1.4GHz Very Large Array radio continuum observations of two ~0.5{deg}^2^ fields in the Coma cluster of galaxies. The two fields, "Coma 1" and "Coma 3", correspond to the cluster core and southwest infall region and were selected on account of abundant preexisting multiwavelength data. In their most sensitive regions the radio data reach 22uJy rms per 4.4" beam, sufficient to detect (at 5{sigma}) Coma member galaxies with L_1.4GHz_=1.3x10^20^W/Hz. The full catalog of radio detections is presented herein and consists of 1030 sources detected at >=5{sigma}, 628 of which are within the combined Coma 1 and Coma 3 area. We also provide optical identifications of the radio sources using data from the Sloan Digital Sky Survey. The depth of the radio observations allows us to detect active galactic nucleus in cluster elliptical galaxies with M_r_<-20.5 (AB magnitudes), including radio detections for all cluster ellipticals with M_r_<-21.8. At fainter optical magnitudes (-20.5<M_r_~<-19), the radio sources are associated with star-forming galaxies with star formation rates as low as 0.1M_{sun}_/yr.
- ID:
- ivo://CDS.VizieR/J/MNRAS/478/4336
- Title:
- Coma galaxies UV and opt. view
- Short Name:
- J/MNRAS/478/4336
- Date:
- 10 Dec 2021 00:56:54
- Publisher:
- CDS
- Description:
- The Coma supercluster (100h^-1^Mpc) offers an unprecedented contiguous range of environments in the nearby Universe. In this paper, we present a catalogue of spectroscopically confirmed galaxies in the Coma supercluster detected in the ultraviolet (UV) wavebands. We use the arsenal of UV and optical data for galaxies in the Coma supercluster covering ~500deg^2^ on the sky to study their photometric and spectroscopic properties as a function of environment at various scales. We identify the different components of the cosmic-web: large-scale filaments and voids using Discrete Persistent Structures Extractor, and groups and clusters using Hierarchical Density-based spatial clustering of applications with noise, respectively. We find that in the Coma supercluster the median emission in H{alpha} inclines, while the g-r and FUV-NUV colours of galaxies become bluer moving further away from the spine of the filaments out to a radius of ~1Mpc. On the other hand, an opposite trend is observed as the distance between the galaxy and centre of the nearest cluster or group decreases. Our analysis supports the hypothesis that properties of galaxies are not just defined by its stellar mass and large-scale density, but also by the environmental processes resulting due to the intrafilament medium whose role in accelerating galaxy transformations needs to be investigated thoroughly using multiwavelength data.
- ID:
- ivo://CDS.VizieR/J/ApJ/720/723
- Title:
- Compact galaxies in the local universe
- Short Name:
- J/ApJ/720/723
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We set out to test the claim that the recently identified population of compact, massive, and quiescent galaxies at z~2.3 must undergo significant size evolution to match the properties of galaxies found in the local universe. Using data from the Sloan Digital Sky Survey (SDSS; Data Release 7), we have conducted a search for local red sequence galaxies with sizes and masses comparable to those found at z~2.3. The SDSS spectroscopic target selection algorithm excludes high surface brightness objects; we show that this makes incompleteness a concern for such massive, compact galaxies, particularly for low redshifts (z<~0.05). We have identified 63 M_*_>10^10.7^M_{sun}_ (~5x10^10^M_{sun}_) red sequence galaxies at 0.066<z_spec_<0.12 which are smaller than the median size-mass relation by a factor of 2 or more. Consistent with expectations from the virial theorem, the median offset from the mass-velocity dispersion relation for these galaxies is 0.12 dex. We do not, however, find any galaxies with sizes and masses comparable to those observed at z~2.3, implying a decrease in the comoving number density of these galaxies, at fixed size and mass, by a factor of >~5000. This result cannot be explained by incompleteness: in the 0.066<z<0.12 interval, we estimate that the SDSS spectroscopic sample should typically be >~75% complete for galaxies with the sizes and masses seen at high redshift, although for the very smallest galaxies it may be as low as ~20%. In order to confirm that the absence of such compact massive galaxies in SDSS is not produced by spectroscopic selection effects, we have also looked for such galaxies in the basic SDSS photometric catalog, using photometric redshifts. While we do find signs of a slight bias against massive, compact galaxies, this analysis suggests that the SDSS spectroscopic sample is missing at most a few objects in the regime we consider.
