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5831. SDSS J080434.20+510349.2 spectra and photometry
ID:
ivo://CDS.VizieR/J/A+A/549/A77
Title:
SDSS J080434.20+510349.2 spectra and photometry
Short Name:
J/A+A/549/A77
Date:
21 Oct 2021
Publisher:
CDS
Description:
This study of SDSS J080434.20+510349.2 (SDSS0804) is primarily concerned with the double-hump shape in the light curve and its connection with the accretion disk in this bounce-back system. Time-resolved photometric and spectroscopic observations were obtained to analyze the behavior of the system between superoutbursts. A qualitative geometric model of a binary system containing a disk with two outer annuli spiral density waves was applied to explain the light curve and the Doppler tomography. Observations were carried out during 2008-2009, after the object's magnitude decreased to V~17.7+/-0.1 from the March 2006 eruption. The light curve clearly shows a sinusoid-like variability with a 0.07mag amplitude and a 42.48min periodicity, which is half of the orbital period of the system. In September 2010, the system underwent yet another superoutburst and returned to its quiescent level by the beginning of 2012. This light curve once again showed a double-hump-shape, but with a significantly smaller (~0.01mag) amplitude. Other types of variability like a "mini-outburst" or SDSS1238-like features were not detected. Doppler tomograms, obtained from spectroscopic data during the same period of time, show a large accretion disk with uneven brightness, implying the presence of spiral waves. We constructed a geometric model of a bounce-back system containing two spiral density waves in the outer annuli of the disk to reproduce the observed light curves. The Doppler tomograms and the double-hump-shape light curves in quiescence can be explained by a model system containing a massive >=0.7M_{sun}_ white dwarf with a surface temperature of ~12000K, a late-type brown dwarf, and an accretion disk with two outer annuli spirals. According to this model, the accretion disk should be large, extending to the 2:1 resonance radius, and cool ~2500K. The inner parts of the disk should be optically thin in the continuum or totally void.
5832. SDSS low-metallicity blue compact dwarf galaxies
ID:
ivo://CDS.VizieR/J/ApJ/863/134
Title:
SDSS low-metallicity blue compact dwarf galaxies
Short Name:
J/ApJ/863/134
Date:
21 Oct 2021
Publisher:
CDS
Description:
We report a method of identifying candidate low-metallicity blue compact dwarf galaxies (BCDs) from the Sloan Digital Sky Survey (SDSS) imaging data, and present 3m Lick Observatory and 10m W.M. Keck Observatory optical spectroscopic observations of 94 new systems that have been discovered with this method. The candidate BCDs are selected from Data Release 12 (DR12) of SDSS on the basis of their photometric colors and morphologies. Using the Kast spectrometer on the 3m telescope, we confirm that the candidate low-metallicity BCDs are emission-line galaxies, and we make metallicity estimates using the empirical R and S calibration methods. Follow-up observations on a subset of the lowest-metallicity systems are made at Keck using the Low Resolution Imaging Spectrometer, which allow for a direct measurement of the oxygen abundance. We determine that 45 of the reported BCDs are low-metallicity candidates with 12+log(O/H)<=7.65, including six systems which are either confirmed or projected to be among the lowest-metallicity galaxies known, at 1/30 of the solar oxygen abundance, or 12+log(O/H)~7.20.
5833. 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.
5834. SDSS-2MASS-WISE stellar colour locus
ID:
ivo://CDS.VizieR/J/MNRAS/440/3430
Title:
SDSS-2MASS-WISE stellar colour locus
Short Name:
J/MNRAS/440/3430
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present the fiducial main-sequence stellar locus traced by 10 photometric colours observed by Sloan Digital Sky Survey (SDSS), Two Micron All Sky Survey (2MASS), and Wide-field Infrared Survey Explorer} (WISE). Median colours are determined using 1052 793 stars with r-band extinction less than 0.125. We use this locus to measure the dust extinction curve relative to the r band, which is consistent with previous measurements in the SDSS and 2MASS bands. The WISE band extinction coefficients are larger than predicted by standard extinction models. Using 13 lines of sight, we find variations in the extinction curve in H, Ks, and WISE bandpasses. Relative extinction decreases towards Galactic anticentre, in agreement with prior studies. Relative extinction increases with Galactic latitude, in contrast to previous observations. This indicates a universal mid-IR extinction law does not exist due to variations in dust grain size and chemistry with Galactocentric position. A preliminary search for outliers due to warm circumstellar dust is also presented, using stars with high signal-to-noise ratio in the W3 band. We find 199 such outliers, identified by excess emission in Ks-W3. Inspection of SDSS images for these outliers reveals a large number of contaminants due to nearby galaxies. Six sources appear to be genuine dust candidates, yielding a fraction of systems with infrared excess of 0.12+/-0.05 per cent.
5835. SDSS M, L, and T dwarfs
ID:
ivo://CDS.VizieR/J/AJ/123/3409
Title:
SDSS M, L, and T dwarfs
Short Name:
J/AJ/123/3409
Date:
21 Oct 2021
Publisher:
CDS
Description:
An extensive sample of M, L, and T dwarfs identified in the Sloan Digital Sky Survey (SDSS) has been compiled. The sample of 718 dwarfs includes 677 new objects (629 M dwarfs and 48 L dwarfs), together with 41 that have been previously published. All new objects and some of the previously published ones have new optical spectra obtained either with the SDSS spectrographs or with the Apache Point Observatory 3.5 m ARC telescope. Spectral types and SDSS colors are available for all objects; approximately 35% also have near-infrared magnitudes measured by 2MASS (Two Micron All Sky Survey) or on the Mauna Kea system. We use this sample to characterize the color-spectral type and color-color relations of late-type dwarfs in the SDSS filters and to derive spectroscopic and photometric parallax relations for use in future studies of the luminosity and mass functions based on SDSS data. We find that the i*-z* and i*-J colors provide good spectral type and absolute magnitude (Mi*) estimates for M and L dwarfs. Our distance estimates for the current sample indicate that SDSS is finding early M dwarfs out to ~1.5kpc, L dwarfs to ~100pc, and T dwarfs to ~20pc. The T dwarf photometric data show large scatter and are therefore less reliable for spectral type and distance estimation.
5836. 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.
5837. 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.
5838. SDSS new variables
ID:
ivo://CDS.VizieR/J/AJ/115/296
Title:
SDSS new variables
Short Name:
J/AJ/115/296
Date:
21 Oct 2021
Publisher:
CDS
Description:
The US Naval Observatory 0.2m Flagstaff Astrometric Scanning Transit Telescope (FASTT) was used to obtain astrometric information in 16 equatorial fields in support of the Sloan Digital Sky Survey (SDSS). Each field is approximately 7.6{deg}x3.2{deg} in size and was scanned ~10 times with overlapping CCD strip scans; star positions accurate to +/-50mas in each coordinate and magnitudes good to +/-0.011mag were determined. As an ancillary project, this database was searched for new variables, and the results of that search are presented here. Approximately 1500 new variables have been discovered, and accurate coordinates for ~100 previously identified variables and suspected variables are given.
5839. SDSS observations of Kuiper belt objects
ID:
ivo://CDS.VizieR/J/ApJ/749/10
Title:
SDSS observations of Kuiper belt objects
Short Name:
J/ApJ/749/10
Date:
21 Oct 2021
Publisher:
CDS
Description:
Colors of trans-Neptunian objects (TNOs) are used to study the evolutionary processes of bodies in the outskirts of the solar system and to test theories regarding their origin. Here I describe a search for serendipitous Sloan Digital Sky Survey (SDSS) observations of known TNOs and Centaurs. I present a catalog of SDSS photometry, colors, and astrometry of 388 measurements of 42 outer solar system objects. I find weak evidence, at the {approx} 2{sigma} level (per trial), for a correlation between the g - r color and inclination of scattered disk objects and hot classical Kuiper Belt objects. I find a correlation between the g - r color and the angular momentum in the z direction of all the objects in this sample. These findings should be verified using larger samples of TNOs. Light curves as a function of phase angle are constructed for 13 objects. The steepness of the slopes of these light curves suggests that the coherent backscatter mechanism plays a major role in the reflectivity of outer solar system small objects at small phase angles. I find weak evidence for an anticorrelation, significant at the 2{sigma} confidence level (per trial), between the g-band phase-angle slope parameter and the semimajor axis, as well as the aphelion distance, of these objects (i.e., they show a more prominent "opposition effect" at smaller distances from the Sun). However, this plausible correlation should be verified using a larger sample. I discuss the origin of this possible correlation and argue that if this correlation is real it probably indicates that "Sedna"-like objects have a different origin than other classes of TNOs. Finally, I identify several objects with large variability amplitudes.
5840. SDSS photometry in the field of L1457
ID:
ivo://CDS.VizieR/J/AJ/124/2164
Title:
SDSS photometry in the field of L1457
Short Name:
J/AJ/124/2164
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present a spectroscopic and photometric survey of a sample of field stars in the region of the molecular cloud L1457. High-quality coude feed spectra, together with five-band photometry in the Sloan Digital Sky Survey system and near-infrared archival data from the Two Micron All Sky Survey, are used to derive color excesses and distances for the stars. Based on these data, a new distance estimate of 360+/-30pc is derived for the cloud, supporting recent results by K.L. Luhman, 2001ApJ...560..287L. The data further indicate that the north-south velocity gradient seen in the millimeter-wave CO data is mirrored in a distance gradient, with the northern part of the cloud being closer to us. A second, less opaque, layer of extinction is detected at ~80pc. This distance is consistent with the earlier distance estimates to the cloud, based on Na I absorption. We identify this layer with the wall of the hot Local Bubble. Hence, the dense cloud is not, as previously thought, associated with the Local Bubble.