Large amount of observational spectroscopic data are recently available from different observational projects, like Sloan Digital Sky Survey. It's become more urgent to identify white dwarfs stars based on data itself i.e. without modelling white dwarf atmospheres. In particular, existing methods of white dwarfs identification presented in Kleinman et al. (2004) and in Eisenstein et al. (2006) did not allow to find all the white dwarfs in examined data. We intend to test various criteria of searching for white dwarf candidates, based on photometric and spectral features.
We report on the discovery of a new AM CVn candidate from the Sloan Digital Sky Survey, Data Release 1. Our first spectroscopic follow-up in the optical is presented and discussed briefly.
I summarize the scientific goals and current status of the Sloan Digital Sky Survey, briefly describe the Early Data Release, and discuss some recent scientific results obtained from commissioning data which are apposite to the distribution of luminous and dark matter in the Universe.
We present a spectral analysis of 16 DAO white dwarfs from the Sloan Digital Sky Survey Data Release 4. With our NLTE H+He model grid, we derived photospheric parameters for these objects. We compare our new results to literature values and divide the DAOs into two distinct groups: post-AGB and EHB progenitors.
The Sloan Digital Sky Survey (SDSS) is a project to definitively map $π$ steradians of the local Universe. An array of CCD detectors used in drift-scan mode will digitally image the sky in five passbands to a limiting magnitude of $r' \sim 23$. Selected from the imaging survey, $10^6$ galaxies and $10^5$ quasars will be observed spectroscopically. I describe the current status of the survey, which is due to begin observations early in 1997, and its prospects for constraining models for dark matter in the Universe.
Photometric and spectroscopic observations reveal the Sloan Digital Sky Survey cataclysmic variable SDSS J132723.39+652854.2 to be a likely SW Sex star with an orbital period of P = 3.28 hours. The Sloan Digital Sky Survey spectrum shows strong HeI, HeII and Balmer emission lines. Time resolved spectra acquired at Apache Point Observatory reveal absorption-line structure within the emission lines near phase 0.5. Photometric data obtained at Manastash Ridge Observatory using Harris V and B filters reveal a high inclination system (i = 80 degrees) with deep (~ 2 mag.) eclipses. The orbital perio…
This paper describes the Third Data Release of the Sloan Digital Sky Survey (SDSS). This release, containing data taken up through June 2003, includes imaging data in five bands over 5282 deg^2, photometric and astrometric catalogs of the 141 million objects detected in these imaging data, and spectra of 528,640 objects selected over 4188 deg^2. The pipelines analyzing both images and spectroscopy are unchanged from those used in our Second Data Release.
While the strategy for the first applications of weak lensing has been to ``go deep'' it is equally interesting to use one's telescope time to instead ``go wide''. The Sloan Survey (SDSS) provides a natural framework for a very wide area weak lensing survey.
Following Paper I, we provide extended tables of bolometric corrections, extinction coefficients, stellar isochrones, and integrated magnitudes and colours of single-burst stellar populations, for the Sloan Digital Sky Survey (SDSS) ugriz photometric system. They are tested on comparisons with DR1 data for a few stellar systems, namely the Palomar 5 and NGC 2419 globular clusters and the Draco dSph galaxy.
We present results on over 100 high-redshift quasars found in the Sloan Digital Sky Survey (SDSS), using automated selection algorithms applied to SDSS imaging data and with spectroscopic confirmation obtained during routine spectroscopic operations of the Sloan 2.5-m telescope. The SDSS spectra cover the wavelength range 3900--9200 Angstroms at a spectral resolution of 1800, and have been obtained for 116 quasars with redshifts greater than 3.94; 92 of these objects were previously uncataloged, significantly increasing the current tally of published z>4 quasars. The paper also reports observa…
The Sloan Digital Sky Survey (SDSS) will carry out a digital photometric and spectroscopic survey over pi steradians in the northern Galactic cap. An array of CCD detectors used in drift-scan mode will image the sky in five passbands to a limiting magnitude of r' ~ 23. Selected from the imaging survey, 10^6 galaxies, 10^5 quasars and selected samples of stars will be observed spectroscopically. I describe the current status of the survey, which recently saw first light, and its prospects for constraining models for dark matter in the Universe.
Current X-ray observatories, archival X-ray data, and the Sloan Digital Sky Survey (SDSS) represent a powerful combination for addressing key questions about active galactic nuclei (AGN). We describe a few selected issues at the forefront of X-ray AGN research and the relevance of the SDSS to them. Bulk X-ray/SDSS AGN investigations, X-ray weak AGN, red AGN, hard X-ray selected AGN, high-redshift AGN demography, and future prospects are all briefly discussed.
Automated techniques have been developed to automate the process of classification of objects or their analysis. The large datasets provided by upcoming spectroscopic surveys with dedicated telescopes urges scientists to use these automated techniques for analysis of such large datasets which are now available to the community. Sloan Digital Sky Survey (SDSS) is one of such surveys releasing massive datasets. We use Probabilistic Neural Network (PNN) for automatic classification of about 5000 SDSS spectra into 158 spectral type of a reference library ranging from O type to M type stars.
We present template spectra of low-mass (M0-L0) dwarfs derived from over 4,000 Sloan Digital Sky Survey (SDSS) spectra. These composite spectra are suitable for use as medium-resolution (R ~ 1,800) radial velocity standards. We report mean spectral properties (molecular bandhead strengths,equivalent widths) and use the templates to investigate the effects of magnetic activity and metallicity on the spectroscopic and photometric properties of low-mass stars.
The Sloan Digital Sky Survey has obtained 450 square degrees of photometric scan data, in five bands (u',g',r',i',z'), which we use to identify clusters of galaxies. We illustrate how we do star-galaxy separation, and present a simple and elegant method of detecting overdensities in the galaxy distribution, using the Voronoi Tessellation.
The quasar Q0353-383 has long been known to have extremely strong nitrogen intercombination lines at 1486 and 1750 Angstroms, implying an anomalously high nitrogen abundance of ~15 times solar. A search for similar nitrogen-rich quasars in the Sloan Digital Sky Survey First Data Release catalog has yielded 20 candidates, including four with nitrogen emission as strong or stronger than that seen in Q0353-383. Our results indicate that only about 1 in 1700 of quasars have nitrogen abundances similar to Q0353-383, while up to 1 in 130 may be in the process of extreme nitrogen enrichment.
The Sloan Digital Sky Survey (SDSS) will provide the data to support detailed investigations of the distribution of luminous and non- luminous matter in the Universe: a photometrically and astrometrically calibrated digital imaging survey of pi steradians above about Galactic latitude 30 degrees in five broad optical bands to a depth of g' about 23 magnitudes, and a spectroscopic survey of the approximately one million brightest galaxies and 10^5 brightest quasars found in the photometric object catalog produced by the imaging survey. This paper summarizes the observational parameters and data…
The Sloan Digital Sky Survey has validated and made publicly available its First Data Release. This consists of 2099 square degrees of five-band (u, g, r, i, z) imaging data, 186,240 spectra of galaxies, quasars, stars and calibrating blank sky patches selected over 1360 square degrees of this area, and tables of measured parameters from these data. The imaging data go to a depth of r ~ 22.6 and are photometrically and astrometrically calibrated to 2% rms and 100 milli-arcsec rms per coordinate, respectively. The spectra cover the range 3800--9200 A, with a resolution of 1800--2100. Further ch…
The Sloan Digital Sky Survey (SDSS) will carry out a digital photometric and spectroscopic survey over pi steradians in the northern Galactic cap. An array of CCD detectors used in drift-scan mode will image the sky in five passbands to a limiting magnitude of r' ~ 23. Selected from the imaging survey, 10^6 galaxies, 10^5 quasars and selected samples of stars will be observed spectroscopically. In addition, a smaller (225 deg^2), deeper, southern survey will reach ~2.0 magnitudes fainter and will contain a wealth of information about variable sources, supernovae and proper motions. We describe…
We have identified 7 new magnetic DA white dwarfs in the Early Data Release of the Sloan Digital Sky Survey. Our selection strategy has also recovered all the previously known magnetic white dwarfs contained in the SDSS EDR, KUV03292+0035 and HE0330-0002. Analysing the SDSS fibre spectroscopy of the magnetic DA white dwarfs with our state-of-the-art model spectra, we find dipole field strengths 1.5<=B_d<=63MG and effective temperatures 8500<=Teff<=39000K. As a conservative estimate, we expect that the complete SDSS will increase the number of known magnetic white dwarfs by a factor 3.
Galactic extinction is tested using galaxy number counts at low Galactic latitude obtained from five band photometry of the Sloan Digital Sky Survey. The spatial variation of galaxy number counts for low extinction regions of $E(B-V) < 0.15$ is consistent with the all-sky reddening map of Schlegel, Finkbeiner, & Davis (1998) and the standard extinction law. For higher extinction regions of $E(B-V) > 0.15$, however, the map of Schlegel et al.(1998) overestimates the reddening by a factor up to 1.4, which is likely ascribed to the departure from proportionality of reddening to infrared emissivit…
We present deep Hubble Space Telescope ACS and NICMOS images of six bright Lyman-break galaxy candidates that were previously discovered in the Sloan Digital Sky Survey. We find that five of the objects are consistent with unresolved point sources. Although somewhat atypical of the class, they are most likely LoBAL quasars, perhaps FeLoBALs. The sixth object, J1147, has a faint companion galaxy located ~0.8 arcsec to the southwest. The companion contributes ~8% of the flux in the observed-frame optical and infrared. It is unknown whether this companion is located at the same redshift as J1147.
We report the discovery of 27 quasars with redshifts between 3.58 and 4.49. The objects were identified as high-redshift candidates based on their colors in Sloan Digital Sky Survey commissioning data. The redshifts were confirmed with low resolution spectra obtained at the Hobby-Eberly Telescope. The quasars' $i^*$ magnitudes range from 18.55 to 20.97. Nearly 60% of the quasar candidates observed are confirmed spectroscopically as quasars. Two of the objects are Broad Absorption Line quasars, and several other quasars appear to have narrow associated absorption features.
The ``AGN Physics with the Sloan Digital Sky Survey'' conference was held at Princeton University in July 2003 to bring together groups working inside and outside of the SDSS collaboration at radio through X-ray wavelengths to discuss the common goal of better understanding the physics of Active Galactic Nuclei (AGN). Although we still do not have a full understanding of AGN, much progress has been made in recent years. In this conference summary, we concentrate on those topics discussed at the meeting where we believe that there has been significant change or where there is a new standard of …
The Sloan Digital Sky Survey (SDSS) is the largest and most ambitious optical CCD survey undertaken to date. It will ultimately map out one quarter of the sky with precision photometry in five bands, high-quality astrometry, and spectra of all galaxies and quasars brighter than certain limiting magnitudes. The scientific potential of the SDSS is enormous and addresses a wide variety of astrophysical key questions. After a proprietary period the reduced and calibrated data are made available to the astronomical community as a whole. The SDSS is run by an international consortium involving unive…
This paper describes the fourth data release of the Sloan Digital Sky Survey (SDSS), including all survey-quality data taken through June 2004. The data release includes five-band photometric data for 180 million objects selected over 6670 deg^2, and 673,280 spectra of galaxies, quasars, and stars selected from 4783 deg^2 of that imaging data using the standard SDSS target selection algorithms. These numbers represent a roughly 25% increment over those of the Third Data Release. The Fourth Data Release also includes an additional 131,840 spectra of objects selected using a variety of alternati…
Astronomy is changing. Large projects, large collaborations, and large budgets are becoming the norm. The Sloan Digital Sky Survey (SDSS) is one example of this new astronomy, and in operating the original survey, we put in place and learned many valuable operating principles. Scientists sometimes have the tendency to invent everything themselves but when budgets are large, deadlines are many, and both are tight, learning from others and applying it appropriately can make the difference between success and failure. We offer here our experiences well as our thoughts, opinions, and beliefs on wh…
We report on a novel search for radio gravitational lenses. Using the Very Large Array, we imaged ten candidates with both dual redshifts in Sloan Digital Sky Survey spectra and 1.4 GHz radio flux >2 mJy in the FIRST survey. The VLA maps show that in each case the radio emission is associated with the foreground galaxy rather than being lensed emission from the background galaxy, although at least four of our targets are strong lenses at optical wavelengths. These SDSS dual-redshift systems do not have lensed radio emission at the sensitivity of current radio surveys.
We have examined the radial velocity data for stars spectroscopically observed by the Sloan Digital Sky Survey (SDSS) more than once to investigate the incidence of spectroscopic binaries, and to evaluate the accuracy of the SDSS stellar radial velocities. We find agreement between the fraction of stars with significant velocity variations and the expected fraction of binary stars in the halo and thick disk populations. The observations produce a list of 675 possible new spectroscopic binary stars and orbits for eight of them.
We collected a sample of 661 confirmed and 361 possible BL Lac candidates from the recent catalog of BL Lac objects (Veron-Cetty & Veron 2006). We searched these sources in the recent data release DR5 of the Sloan Digital Sky Survey (SDSS) and found spectra were available for 169 and 109 confirmed and possible BL Lac candidates respectively. We found 32 candidates from confirmed and 19 candidates from possible BL Lac lists have non featureless spectra and are thus possibly not BL Lac candidates. We report here the preliminary results from our analysis of a sample of 278 BL Lac objects.
We present the identification of 13 DB + dM binaries and 2 DC + dM binaries from the Sloan Digital Sky Survey (SDSS). Before the SDSS only 2 DB + dM binaries and 1 DC + dM binary were known. At least three, possibly 8, of the new DB + dM binaries seem to have white dwarf temperatures well above 30000 K which would place them in the so called DB-gap. Finding these DB white dwarfs in binaries may suggest that they have formed through a different evolutionary channel than the ones in which DA white dwarfs transform into DB white dwarfs due to convection in the upper layers.
A search for fossil groups in the Sloan Digital Sky Survey was performed using virtual observatory tools. A cross-match of the positions of all SDSS Luminous Red Galaxies (with r < 19 and measured spectroscopic redshifts) with sources in the ROSAT All-Sky Survey catalog resulted in a list of elliptical galaxies with extended X-ray emission (with a galaxy/ROSAT-source distance of less than 0.5 arcmin in all cases). A search for neighbors of the selected elliptical galaxies within a radius of $0.5 h_{70}^{-1}$ Mpc was conducted taking into account the r-band magnitudes and spectroscopic or photo…
We present the results of a novel new search of the first data-release from the Sloan Digital Sky Survey (SDSS-DR1) for the spectra of supernovae. The use of large spectroscopic galaxy surveys offers the prospect of obtaining improved estimates of the local supernova rate, with the added benefit of a very different selection function to that of conventional photometric surveys. In this Letter we present an overview of our search methodology and the details of 19 Type Ia supernovae found in SDSS--DR1. The supernovae sample is used to make a preliminary estimate, Gamma_Ia = 0.4 +/- 0.2 h^2 SNu, …
While most of the microwave background fluctuations on angular scales greater than a few arcminutes were generated at z > 800, the low redshift universe does distort the microwave background. Since the Sloan Digital Sky Survey (SDSS) traces the structures in the low-redshift universe, we can gain additional insights into the physics of the low-redshift universe by cross-correlating microwave background maps with template maps produced from the SDSS. We present a formalism for cross-correlating data from the Microwave Anisotropy Probe (MAP) with the Sloan Survey for the thermal Sunyaev-Zel'dovi…
Using photometric selection criteria, and in a final step visual inspection of spectra, we find 65 DQ white dwarfs in the Data Release 4 of the Sloan Digital Sky Survey. 37 of these are new identifications, three more are reclassified DQ from DC, the other 25 have been described as DQ before in the literature. We derive effective temperatures and carbon abundances for 60 of these stars. The results confirm the main conclusions of Dufour et al.(2005). The majority of stars defines a clear sequence in the C abundance vs. Teff diagram, with high abundances found at high Teff and vice versa. We al…
The astrometric calibration of the Sloan Digital Sky Survey is described. For point sources brighter than r ~ 20 the astrometric accuracy is 45 milliarcseconds (mas) rms per coordinate when reduced against the USNO CCD Astrograph Catalog, and 75 mas rms when reduced against Tycho-2, with an additional 20 - 30 mas systematic error in both cases. The rms errors are dominated by anomalous refraction and random errors in the primary reference catalogs. The relative astrometric accuracy between the r filter and each of the other filters (u g i z) is 25 - 35 mas rms. At the survey limit (r ~ 22), th…
We present a catalog of galaxy clusters selected using the maxBCG redsequence method from Sloan Digital Sky Survey photometric data. This catalog includes 13,823 clusters with velocity dispersions greater than 400 km/s, and is the largest galaxy cluster catalog assembled to date. They are selected in an approximately volume-limited way from a 0.5 Gpc^3 region covering 7500 square degrees of sky between redshifts 0.1 and 0.3. (ABRIGDED)
The Sloan Digital Sky Survey (SDSS) is making a multi-colour, three dimensional map of the nearby Universe. The survey is in two parts. The first part is imaging one quarter of the sky in five colours from the near ultraviolet to the near infrared. In this imaging survey we expect to detect around 50 million galaxies to a magnitude limit g ~ 23. The second part of the survey, taking place concurrently with the imaging, is obtaining spectra for up to 1 million galaxies and 100,000 quasars. From these spectra we obtain redshifts and hence distances, in order to map out the three-dimensional dist…
The Early Data Release of the Sloan Digital Sky Survey (SDSS) contains 150 Narrow-Line Seyfert 1 (NLS1) galaxies, most of them previously unknown. We present here the study of the X-ray emission from two of these active galaxies (SDSS J030639.57+000343.2 and SDSS J141519.50-003021.6), based upon XMM-Newton observations. The spectral and timing characteristics of the two sources are presented and compared against the typical properties of known NLS1 galaxies. We found that these two NLS1 are within the dispersion range of the typical values of this class of AGN, although with some interesting f…
This paper describes spectra of quasar candidates acquired during the commissioning phase of the Low-Resolution Spectrograph of the Hobby-Eberly Telescope. The objects were identified as possible quasars from multicolor image data from the Sloan Digital Sky Survey. The ten sources had typical r' magnitudes of 19-20, except for one extremely red object with r' of approximately 23. The data, obtained with exposure times between 10 and 25 minutes, reveal that the spectra of four candidates are essentially featureless and are not quasars, five are quasars with redshifts between 2.92 and 4.15 (incl…
We have constructed a Main galaxy subsample with redshifts in the range 0.08<=z<=0.12 from SDSS Data Release 3 (SDSS DR3), and refer to this subsample as "MGSU"(It contains 67777 galaxies). By cluster analysis, two isolated Main galaxy samples are extracted from this subsample. It turns out that two isolated Main galaxy samples identified at different radii have the same properties. Additionally, we also find that early-type galaxies in isolated Main galaxy samples are fewer than that in close double galaxy sample.
We present a weak lensing analysis of the Coma Cluster using the Sloan Digital Sky Survey (SDSS) Data Release Five. Complete imaging of a ~ 200 square degree region is used to measure the tangential shear of this cluster. The shear is fit to an NFW model and we find a virial radius of r_{200}=1.99_{-0.22}^{+0.21}h^{-1}Mpc which corresponds to a virial mass of M_{200}=1.88_{-0.56}^{+0.65}\times10^{15}h^{-1}M_{\odot}. We additionally compare our weak lensing measurement to the virial mass derived using dynamical techniques, and find they are in agreement. This is the lowest redshift, largest ang…
We present spectroscopic observations with the 3.6m ESO telescope of two emission-line galaxies, J2104-0035 and J0113+0052, selected from the Data Release 4 (DR4) of the Sloan Digital Sky Survey (SDSS). From our data we determine the oxygen abundance of these systems to be respectively 12+logO/H = 7.26+/-0.03 and 7.17+/-0.09, making them the two most metal-deficient galaxies found thus far in the SDSS and placing them among the five most metal-deficient emission-line galaxies ever discovered. Their oxygen abundances are close to those of the two most metal-deficient emission-line galaxies know…
We find evidence for dust in the intervening QSO absorbers from the spectra of QSOs in the Sloan Digital Sky Survey Data Release 1. No evidence is found for the 2175 A feature which is present in the Milky Way dust extinction curve. The extinction curve resembles the SMC extinction curve. The observed Delta(g-i) excess for QSOs with strong absorption systems appears to be a result of the reddening due to dust in the intervening absorbers.
The next-generation astronomy archives will cover most of the universe at fine resolution in many wavelengths. One of the first of these projects, the Sloan Digital Sky Survey (SDSS) will create a 5-wavelength catalog over 10,000 square degrees of the sky. The 200 million objects in the multi-terabyte database will have mostly numerical attributes, defining a space of 100+ dimensions. Points in this space have highly correlated distributions. The archive will enable astronomers to explore the data interactively. Data access will be aided by multidimensional spatial indices. The data will be pa…
We investigate the sample of 1175 new nonmagnetic DA white dwarfs with the effective temperatures T_eff > 12000 K, which were extracted from the Data Release 1 of the Sloan Digital Sky Survey. We determined masses, radii, and bolometric luminosities of stars in the sample. The above parameters were derived from the effective temperatures T_eff and surface gravities log g published in the DR1, and the new theoretical M - R relations for carbon-core and oxygen-core white dwarfs. Mass distribution of white dwarfs in this sample exhibits the peak at M = 0.562 M_sol (carbon core stars), and the tai…
A search for nitrogen-rich quasars in the Sloan Digital Sky Survey Early Data Release (SDSS EDR) catalog has yielded 16 candidates, including five with very prominent emission, but no cases with nitrogen emission as strong as in Q0353-383. The quasar Q0353-383 has long been known to have extremely strong nitrogen intercombination lines at lambda 1486 and lambda 1750 Angstroms, implying an anomalously high nitrogen abundance of about 15 times solar. It is still the only one of its kind known. A preliminary search through the EDR using the observed property of the weak C IV emission seen in Q035…
We have constructed samples of low-ionization metal absorption-line systems selected for the strength of their MgII lambda2796 lines from the SDSS EDR. There are 640 absorption systems in our unbiased sample with lambda2796 REW > 1.0 A detected at 5 sigma and with redshifts 0.37 < z < 2.27. This sample is an order of magnitude larger than previous similarly selected samples. In this contribution, we present preliminary results on the statistical properties of the sample.
We present 5 filter photometry of 21 carbon stars, 15 asteroids, 15 cataclysmic variables, 6 metal-poor stars, 5 Cepheids, 1775 field stars, blue horizontal branch (BHB) stars and RR Lyrae stars in the globular clusters M 15 and M 2, two primary standards, and 19 secondary standards. The photometry was carried out using a filter set identical to that which will be used for the Sloan Digital Sky Survey. We find that carbon stars, CVs, R-type, J-type, and V-type asteroids, BHB stars, and RR Lyr stars should be identifiable on the basis of SDSS photometry alone, while Cepheids, metal-poor stars, …
SDSS (DR1 and DR2) has recently proposed 7 new DO white dwarfs as well as 6 new PG1159 stars. This is a significant increase in the known number of DOs and PG1159 stars. Our spectral analyses provide stellar parameters which can then be used to derive constraints for the evolution of H-deficient white dwarfs. A comprehensive understanding of these objects is still severely hampered by low-number statistics.
We re-examine the evidence for a violation of large-scale statistical isotropy in the distribution of projected spin vectors of spiral galaxies. We have a sample of $\sim 37,000$ spiral galaxies from the Sloan Digital Sky Survey, with their line of sight spin direction confidently classified by members of the public through the online project Galaxy Zoo. After establishing and correcting for a certain level of bias in our handedness results we find the winding sense of the galaxies to be consistent with statistical isotropy. In particular we find no significant dipole signal, and thus no evide…
The Sloan Digital Sky Survey has discovered a population of broad absorption line quasars with various extreme properties. Many show absorption from metastable states of FeII with varying excitations; several objects are almost completely absorbed bluewards of MgII; at least one shows stronger absorption from FeIII than FeII, indicating temperatures T>35000 K in the absorbing region; and one object even seems to have broad H-beta absorption. Many of these extreme BALs are also heavily reddened, though `normal' BALs (particularly LoBALs) from SDSS also show evidence for internal reddening.
We analyze the photometric redshift catalog of the Sloan Digital Sky Survey Data Release 5 (SDSS DR5) to estimate the Fisher information in the galaxy angular power spectrum with the help of the Rimes-Hamilton technique. It is found that the amount of Fisher information contained in the galaxy angular power spectrum is saturated at lensing multipole scale 300<= l <= 2000 in the redshift range 0.1<= photo-z <0.5. At l=2000, the observed information is two orders of magnitude lower than the case of Gaussian fluctuations. This supports observationally that the translinear regime of the density po…
We report the discovery of the coolest field dwarf yet known, selected as a stellar object with extremely red colors from commissioning imaging data of the Sloan Digital Sky Survey. Its spectrum from 0.8 to 2.5 microns is dominated by strong bands of H_2 O and CH_4. Its spectrum and colors over this range are very similar to those of Gliese 229B, the only other known example of a methane dwarf. It is roughly 1.2 mag fainter than Gliese 229B, implying that it lies at a distance of roughly 10 pc. Such a cool object must have a mass well below the hydrogen-burning limit of 0.08 solar masses, and …
A new broad absorption line quasar (BAL) sample is derived from the first data released by the Sloan Digital Sky Survey. With 116 objects, it is the largest BAL sample yet assembled. Over the redshift range 1.8 < z < 3.8, the crude fraction with broad absorption in the CIV line is roughly 15%. This fraction may be subject to small selection-efficiency adjustments. There are also hints of redshift-dependence in the BAL fraction. The sample is large enough to permit the first estimate of the distribution of "balnicity index": subject to certain arbitrary parameters in the definition of this quan…
We report the discovery of the two-image gravitationally lensed quasar SDSS J133222.62+034739.9 (SDSS J1332+0347) with an image separation of Delta_theta=1.14". This system consists of a source quasar at z_s=1.445 and a lens galaxy at z_l=0.191. The agreement of the luminosity, ellipticity and position angle of the lens galaxy with those expected from lens model confirms the lensing hypothesis.
We summarize the plans for and the current status of the Sloan Digital Sky Survey, a digital imaging and spectroscopic survey of $π$ steradians in the northern Galactic cap. The CCD photometric survey will produce images in five bands to limiting magnitudes of order 23. The spectroscopic survey will obtain redshifts of $10^6$ galaxies (a complete sample to a limiting magnitude $r' \sim 18$) and $10^5$ quasars ($g' \sim 19$). Repeated imaging of a 200 deg$^2$ strip in the southern Galactic cap will yield information about variable objects and a co-added photometric catalog roughly two magnitude…
We explore the angular distribution of two samples of satellite galaxies orbiting isolated hosts extracted from the Sloan Digital Sky Survey Data Release 4. We find a clear alignment of the satellites along the major axis of their hosts when restricting the analysis to red hosts. The anisotropy is most pronounced for red satellites of red hosts. We find that the distribution of the satellites about blue, isolated hosts is consistent with isotropy. We show that under the assumption that the true, underlying distribution of satellites of blue hosts exhibits the same anisotropy as the satellites …
We present and describe a catalog of galaxy photometric redshifts (photo-z's) for the Sloan Digital Sky Survey (SDSS) Data Release 6 (DR6). We use the Artificial Neural Network (ANN) technique to calculate photo-z's and the Nearest Neighbor Error (NNE) method to estimate photo-z errors for ~ 77 million objects classified as galaxies in DR6 with r < 22. The photo-z and photo-z error estimators are trained and validated on a sample of ~ 640,000 galaxies that have SDSS photometry and spectroscopic redshifts measured by SDSS, 2SLAQ, CFRS, CNOC2, TKRS, DEEP, and DEEP2. For the two best ANN methods …
Traditional photometric redshift methods use only color information about the objects in question to estimate their redshifts. This paper introduces a new method utilizing colors, luminosity, surface brightness, and radial light profile to measure the redshifts of galaxies in the Sloan Digital Sky Survey (SDSS). We take a statistical approach: distributions of galaxies from the SDSS Large-Scale Structure (LSS; spectroscopic) sample are constructed at a range of redshifts, and target galaxies are compared to these distributions. An adaptive mesh is implemented to increase the percentage of the …
Supervised artificial neural networks are used to predict useful properties of galaxies in the Sloan Digital Sky Survey, in this instance morphological classifications, spectral types and redshifts. By giving the trained networks unseen data, it is found that correlations between predicted and actual properties are around 0.9 with rms errors of order ten per cent. Thus, given a representative training set, these properties may be reliably estimated for galaxies in the survey for which there are no spectra and without human intervention.
