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Artículo escrito por un elevado número de autores, solo se referencian el que aparece en primer lugar, los autores pertenecientes a la UAM y el nombre del grupo de colaboración, si lo hubiere, We describe the Milky Way Survey (MWS) that will be undertaken with the Dark Energy Spectroscopic Instrument (DESI) on the Mayall 4 m telescope at the Kitt Peak National Observatory. Over the next 5 yr DESI MWS will observe approximately seven million stars at Galactic latitudes ∣b∣ > 20°, with an inclusive target selection scheme focused on the thick disk and stellar halo. MWS will also include several high-completeness samples of rare stellar types, including white dwarfs, low-mass stars within 100 pc of the Sun, and horizontal branch stars. We summarize the potential of DESI to advance understanding of the Galactic structure and stellar evolution. We introduce the final definitions of the main MWS target classes and estimate the number of stars in each class that will be observed. We describe our pipelines for deriving radial velocities, atmospheric parameters, and chemical abundances. We use ≃500,000 spectra of unique stellar targets from the DESI Survey Validation program (SV) to demonstrate that our pipelines can measure radial velocities to ≃1 km s−1 and [Fe/H] accurate to ≃0.2 dex for typical stars in our main sample. We find the stellar parameter distributions from ≈100 deg2 of SV observations with ≳90% completeness on our main sample are in good agreement with expectations from mock catalogs and previous surveys, This equipment was funded by MoE, NSTC, and National Tsing Hua University. C.A.P. acknowledges financial support from the Spanish Ministry of Science and Innovation (MICINN) projects AYA2017-86389-P and PID2020-117493GB-I00. C.J.M. acknowledges financial support from Imperial College London through an Imperial College Research Fellowship grant. M.V. and L.B.e.S. acknowledge support from NASA-ATP award 80NSSC20K0509. The work of A.D. and J.N. is supported by NOIRLab, which is managed by the Association of Universities for Research in Astronomy (AURA) under a cooperative agreement with the National Science Foundation. T.S.L. acknowledges financial support from the Natural Sciences and Engineering Research Council of Canada (NSERC) through grant RGPIN-2022-04794. B.T. G. was supported by grant ST/T000406/1 from the Science and Technology Facilities Council (STFC). This project has received funding from the European Research Council under the European Unionʼs Horizon 2020 research and innovation program (grant agreement No. 101020057). This research made use of computing time available on the high-performance computing system at the Instituto de Astrofisica de Canarias

Full list of authors: Hahn, ChangHoon; Wilson, Michael J.; Ruiz-Macias, Omar; Cole, Shaun; Weinberg, David H.; Moustakas, John; Kremin, Anthony; Tinker, Jeremy L.; Smith, Alex; Wechsler, Risa H.; Ahlen, Steven; Alam, Shadab; Bailey, Stephen; Brooks, David; Cooper, Andrew P.; Davis, Tamara M.; Dawson, Kyle; Dey, Arjun; Dey, Biprateep; Eftekharzadeh, Sarah; Eisenstein, Daniel J.; Fanning, Kevin; Forero-Romero, Jaime E.; Frenk, Carlos S.; Gaztanaga, Enrique; Gontcho, Satya Gontcho; Guy, Julien; Honscheid, Klaus; Ishak, Mustapha; Juneau, Stephanie; Kehoe, Robert; Kisner, Theodore; Lan, Ting-Wen; Landriau, Martin; Le Guillou, Laurent; Levi, Michael E.; Magneville, Christophe; Martini, Paul; Meisner, Aaron; Myers, Adam D.; Nie, Jundan; Norberg, Peder; Palanque-Delabrouille, Nathalie; Percival, Will J.; Poppett, Claire; Prada, Francisco; Raichoor, Anand; Ross, Ashley J.; Safonova, Sasha; Saulder, Christoph; Schlafly, Eddie; Schlegel, David; Sierra-Porta, David; Tarle, Gregory; Weaver, Benjamin A.; Yeche, Christophe; Zarrouk, Pauline; Zhou, Rongpu; Zhou, Zhimin; Zou, Hu.--This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted reuse, distribution, and reproduction in any medium, provided the original work is properly cited., Over the next 5 yr, the Dark Energy Spectroscopic Instrument (DESI) will use 10 spectrographs with 5000 fibers on the 4 m Mayall Telescope at Kitt Peak National Observatory to conduct the first Stage IV dark energy galaxy survey. At z < 0.6, the DESI Bright Galaxy Survey (BGS) will produce the most detailed map of the universe during the dark-energy-dominated epoch with redshifts of >10 million galaxies spanning 14,000 deg2. In this work, we present and validate the final BGS target selection and survey design. From the Legacy Surveys, BGS will target an r < 19.5 mag limited sample (BGS Bright), a fainter 19.5 < r < 20.175 color-selected sample (BGS Faint), and a smaller low-z quasar sample. BGS will observe these targets using exposure times scaled to achieve homogeneous completeness and cover the footprint three times. We use observations from the Survey Validation programs conducted prior to the main survey along with simulations to show that BGS can complete its strategy and make optimal use of "bright" time. BGS targets have stellar contamination 80% fiber assignment efficiency. Finally, BGS Bright and BGS Faint will achieve >95% redshift success over any observing condition. BGS meets the requirements for an extensive range of scientific applications. BGS will yield the most precise baryon acoustic oscillation and redshift-space distortion measurements at z < 0.4. It presents opportunities for new methods that require highly complete and dense samples (e.g., N-point statistics, multitracers). BGS further provides a powerful tool to study galaxy populations and the relations between galaxies and dark matter. © 2023. The Author(s). Published by the American Astronomical Society., C.H. is supported by the AI Accelerator program of the Schmidt Futures Foundation. M.J.W., O.R.-M., S.M.C., C.S.F., and P.N. acknowledge STFC support (grant ST/T000244/1). D.H.W. is supported by NSF grant AST-2009735. This research is supported by the Director, Office of Science, Office of High Energy Physics of the U.S. Department of Energy under contract No. DE-AC02-05CH11231, and by the National Energy Research Scientific Computing Center, a DOE Office of Science User Facility under the same contract; additional support for DESI is provided by the U.S. National Science Foundation, Division of Astronomical Sciences under contract No. AST-0950945 to the NSF's National Optical-Infrared Astronomy Research Laboratory; the Science and Technologies Facilities Council of the United Kingdom; the Gordon and Betty Moore Foundation; the Heising-Simons Foundation; the French Alternative Energies and Atomic Energy Commission (CEA); the National Council of Science and Technology of Mexico (CONACYT); the Ministry of Science and Innovation of Spain (MICINN); and the DESI Member Institutions: https://www.desi.lbl.gov/collaborating-institutions. The complete acknowledgments can be found at https://www.legacysurvey.org/., With funding from the Spanish government through the "Severo Ochoa Centre of Excellence" accreditation (CEX2021-001131-S).

With just a month of data, JWST is already transforming our view of the universe, revealing and resolving starlight in unprecedented populations of galaxies. Although “HST-dark” galaxies have previously been detected at long wavelengths, these observations generally suffer from a lack of spatial resolution, which limits our ability to characterize their sizes and morphologies. Here we report on a first view of starlight from a subset of the HST-dark population that is bright with JWST/NIRCam (4.4 μm < 24.5 mag) and very faint or even invisible with HST (μm). In this Letter we focus on a dramatic and unanticipated population of physically extended galaxies (≳0.″25). These 12 galaxies have photometric redshifts 2 < z < 6, high stellar masses M ⋆ ≳ 1010 M ⊙, and significant dust-attenuated star formation. Surprisingly, the galaxies have elongated projected axis ratios at 4.4 μm, suggesting that the population is disk dominated or prolate and we hence refer to them as ultrared flattened objects. Most of the galaxies appear red at all radii, suggesting significant dust attenuation throughout. With R e (F444W) ∼ 1–2 kpc, the galaxies are similar in size to compact massive galaxies at z ∼ 2 and the cores of massive galaxies and S0s at z ∼ 0. The stellar masses, sizes, and morphologies of the sample suggest that some could be progenitors of lenticular or fast-rotating galaxies in the local universe. The existence of this population suggests that our previous censuses of the universe may have missed massive, dusty edge-on disks, in addition to dust-obscured starbursts.

Abdurro’uf et al., This paper documents the seventeenth data release (DR17) from the Sloan Digital Sky Surveys; the fifth and final release from the fourth phase (SDSS-IV). DR17 contains the complete release of the Mapping Nearby Galaxies at Apache Point Observatory (MaNGA) survey, which reached its goal of surveying over 10,000 nearby galaxies. The complete release of the MaNGA Stellar Library accompanies this data, providing observations of almost 30,000 stars through the MaNGA instrument during bright time. DR17 also contains the complete release of the Apache Point Observatory Galactic Evolution Experiment 2 survey that publicly releases infrared spectra of over 650,000 stars. The main sample from the Extended Baryon Oscillation Spectroscopic Survey (eBOSS), as well as the subsurvey Time Domain Spectroscopic Survey data were fully released in DR16. New single-fiber optical spectroscopy released in DR17 is from the SPectroscipic IDentification of ERosita Survey subsurvey and the eBOSS-RM program. Along with the primary data sets, DR17 includes 25 new or updated value-added catalogs. This paper concludes the release of SDSS-IV survey data. SDSS continues into its fifth phase with observations already underway for the Milky Way Mapper, Local Volume Mapper, and Black Hole Mapper surveys., This publication uses data generated via the Zooniverse.org platform, development of which is funded by generous support, including a Global Impact Award from Google, and by a grant from the Alfred P. Sloan Foundation. This publication makes use of data products from the Two Micron All Sky Survey, which is a joint project of the University of Massachusetts and the Infrared Processing and Analysis Center/California Institute of Technology, funded by the National Aeronautics and Space Administration and the National Science Foundation. This work has made use of data from the European Space Agency (ESA) mission Gaia (https://www.cosmos.esa.int/gaia), processed by the Gaia Data Processing and Analysis Consortium (DPAC; https://www.cosmos.esa.int/web/gaia/dpac/consortium). Funding for the DPAC has been provided by national institutions, in particular the institutions participating in the Gaia Multilateral Agreement.

The Sloan Extension for Galactic Understanding and Exploration 2 (SEGUE-2) obtained 128,288 low-resolution spectra (R ∼ 1800) of 118,958 unique stars in the first year of the Sloan Digital Sky Survey III (2008–2009). SEGUE-2 targeted prioritized distant halo tracers (blue horizontal-branch stars, K giants, and M giants) and metal-poor or kinematically hot populations. The main goal of SEGUE-2 was to target stars in the distant halo and measure their kinematics and chemical abundances to learn about the formation and evolution of the Milky Way. We present the SEGUE-2 field placement and target selection strategies. We discuss the success rate of the targeting based on the SEGUE-2 spectra and other spectroscopic and astrometric surveys. We describe the final SEGUE-2/SDSS-III improvements to the stellar parameter determinations based on the SEGUE Stellar Parameter Pipeline. We report a (g − i) color−effective temperature relation calibrated to the IRFM. We evaluate the accuracy and uncertainties associated with these stellar parameters by comparing with fundamental parameters, a sample of high-resolution spectra of SEGUE stars analyzed homogeneously, stars in well-studied clusters, and stars observed in common by the APOGEE survey. The final SEGUE spectra, calibration data, and derived parameters described here were released in SDSS-III Data Release 9 and continue to be included in all subsequent SDSS Data Releases. Because of its faint limiting magnitude and emphasis on the distant halo, the public SEGUE-2 data remain an important resource for the spectroscopy of stars in the Milky Way.

The Active Optics System of the Vera C. Rubin Observatory (Rubin) uses information provided by four wave front sensors to determine deviations between the reconstructed wave front and the ideal wave front. The observed deviations are used to adjust the control parameters of the optical system to maintain image quality across the 3.°5 field of view. The baseline approach from the project is to obtain amplitudes of the Zernike polynomials describing the distorted wave front from out-of-focus images collected by the wave front sensors. These Zernike amplitudes are related via an “influence matrix” to the control parameters necessary to correct the wave front. In this paper, we use deep-learning methods to extract the control parameters directly from the images captured by the wave front sensors. Our neural net model uses anti-aliasing pooling to boost performance, and a domain-specific loss function to aid learning and generalization. The accuracy of the control parameters derived from our model exceeds Rubin requirements even in the presence of full-moon background levels and mis-centering of reference stars. Although the training process is time consuming, model evaluation requires only a few milliseconds. This low latency should allow for the correction of the optical configuration during the readout and slew interval between successive exposures.

The DESI Milky Way Survey (MWS) will observe $\ge$8 million stars between $16 < r < 19$ mag, supplemented by observations of brighter targets under poor observing conditions. The survey will permit an accurate determination of stellar kinematics and population gradients; characterize diffuse substructure in the thick disk and stellar halo; enable the discovery of extremely metal-poor stars and other rare stellar types; and improve constraints on the Galaxy's 3D dark matter distribution from halo star kinematics. MWS will also enable a detailed characterization of the stellar populations within 100 pc of the Sun, including a complete census of white dwarfs. The target catalog from the preliminary selection described here is public., 4 pages, 1 figure; published in Res. Notes AAS

In preparation for deep extragalactic imaging with the James Webb Space Telescope, we explore the clustering of massive halos at $z=8$ and $10$ using a large N-body simulation. We find that halos with masses $10^9$ to $10^{11}$ $h^{-1}\;M_\odot$, which are those expected to host galaxies detectable with JWST, are highly clustered with bias factors ranging from 5 and 30 depending strongly on mass, as well as on redshift and scale. This results in correlation lengths of 5--10$h^{-1}\;{\rm Mpc}$, similar to that of today's galaxies. Our results are based on a simulation of 130 billion particles in a box of $250h^{-1}\;{\rm Mpc}$ size using our new high-accuracy ABACUS simulation code, the corrections to cosmological initial conditions of (Garrison et al. 2016, 2016MNRAS.461.4125G), and the Planck 2015 cosmology. We use variations between sub-volumes to estimate the detectability of the clustering. Because of the very strong inter-halo clustering, we find that surveys of order 25$h^{-1}\;{\rm Mpc}$ comoving transverse size may be able to detect the clustering of $z=8$--$10$ galaxies with only 500-1000 survey objects if the galaxies indeed occupy the most massive dark matter halos.

Understanding the nature of distant Lyα nebulae, aka blobs, and connecting them to their present-day descendants requires constraining their number density, clustering, and large-scale environment. To measure these basic quantities, we conduct a deep narrowband imaging survey in four different fields, Chandra Deep Field South (CDFS), Chandra Deep Field North (CDFN), and two COSMOS subfields, for a total survey area of 1.2 deg2. We discover 25 blobs at z = 2.3 with Lyα luminosities of L Lyα= (0.7-8) × 1043 erg s–1 and isophotal areas of A iso = 10-60 . The transition from compact Lyα emitters (LAEs; A iso ~ a few ) to extended Lyα blobs (A iso > 10 ) is continuous, suggesting a single family perhaps governed by similar emission mechanisms. Surprisingly, most blobs (16/25) are in one survey field, the CDFS. The six brightest, largest blobs with L Lyα 1.5×1043 erg s–1 and A iso > 16 lie only in the CDFS. These large, bright blobs have a field-to-field variance of σ v 1.5 (150%) about their number density n ~1.0+1.8 –0.6× 10–5 Mpc–3. This variance is large, significantly higher than that of unresolved LAEs (σ v ~ 0.3 or 30%), and can adversely affect comparisons of blob number densities and luminosity functions (LFs) among different surveys. Our deep, blind survey allows us to construct a reliable blob LF. We compare the statistics of our blobs with dark matter halos in a 1 h –1 Gpc cosmological N-body simulation. At z = 2.3, n implies that each bright, large blob could occupy a halo of M halo 1013 M ☉ if most halos have detectable blobs. The predicted variance in n is consistent with that observed and corresponds to a bias of ~7. Blob halos lie at the high end of the halo mass distribution at z = 2.3 and are likely to evolve into the ~1014 M ☉ halos typical of galaxy clusters today. On larger scales of ~10 comoving Mpc, blobs cluster where compact LAEs cluster, indicating that blobs lie in coherent, highly overdense structures.

We present the 24 micron rest-frame luminosity function (LF) of star-forming galaxies in the redshift range 0.0 < z < 0.6 constructed from 4047 spectroscopic redshifts from the AGN and Galaxy Evolution Survey of 24 micron selected sources in the Bootes field of the NOAO Deep Wide-Field Survey. This sample provides the best available combination of large area (9 deg^2), depth, and statistically complete spectroscopic observations, allowing us to probe the evolution of the 24 micron LF of galaxies at low and intermediate redshifts while minimizing the effects of cosmic variance. In order to use the observed 24 micron luminosity as a tracer for star formation, active galactic nuclei (AGNs) that could contribute significantly at 24 micron are identified and excluded from our star-forming galaxy sample based on their mid-IR spectral energy distributions or the detection of X-ray emission. The evolution of the 24 micron LF of star-forming galaxies for redshifts of z < 0.65 is consistent with a pure luminosity evolution where the characteristic 24 micron luminosity evolves as (1+z)^(3.8+/-0.3). We extend our evolutionary study to encompass 0.0 < z < 1.2 by combining our data with that of the Far-Infrared Deep Extragalactic Legacy Survey. Over this entire redshift range the evolution of the characteristic 24 micron luminosity is described by a slightly shallower power law of (1+z)^(3.4+/-0.2). We find a local star formation rate density of (1.09+/-0.21) x 10^-2 Msun/yr/Mpc^-3, and that it evolves as (1+z)^(3.5+/-0.2) over 0.0 < z < 1.2. These estimates are in good agreement with the rates using optical and UV fluxes corrected for the effects of intrinsic extinction in the observed sources. This agreement confirms that star formation at z, Comment: ApJ, in press, 16 pages 9 figures

This paper describes the Seventh Data Release of the Sloan Digital Sky Survey (SDSS), marking the completion of the original goals of the SDSS and the end of the phase known as SDSS-II. It includes 11663 deg^2 of imaging data, with most of the roughly 2000 deg^2 increment over the previous data release lying in regions of low Galactic latitude. The catalog contains five-band photometry for 357 million distinct objects. The survey also includes repeat photometry over 250 deg^2 along the Celestial Equator in the Southern Galactic Cap. A coaddition of these data goes roughly two magnitudes fainter than the main survey. The spectroscopy is now complete over a contiguous area of 7500 deg^2 in the Northern Galactic Cap, closing the gap that was present in previous data releases. There are over 1.6 million spectra in total, including 930,000 galaxies, 120,000 quasars, and 460,000 stars. The data release includes improved stellar photometry at low Galactic latitude. The astrometry has all been recalibrated with the second version of the USNO CCD Astrograph Catalog (UCAC-2), reducing the rms statistical errors at the bright end to 45 milli-arcseconds per coordinate. A systematic error in bright galaxy photometr is less severe than previously reported for the majority of galaxies. Finally, we describe a series of improvements to the spectroscopic reductions, including better flat-fielding and improved wavelength calibration at the blue end, better processing of objects with extremely strong narrow emission lines, and an improved determination of stellar metallicities. (Abridged), Comment: 20 pages, 10 embedded figures. Accepted to ApJS after minor corrections

To obtain an unbiased sample of bright LyA blobs [L(LyA) > 10^43 ergs/s], we have undertaken a blind, wide-field, narrow-band imaging survey in the NOAO Deep Wide Field Survey Bootes field with the Steward Bok-2.3m telescope. After searching over 4.82 sq. degrees at z=2.3, we discover four LyA blobs with L(LyA) = 1.6-5.3 x 10^43 ergs/s, isophotal areas of 28-57 sq. arcsec, and broad LyA line profiles (FWHM = 900-1250 km/s). In contrast with the extended Lyman alpha halos associated with high-z radio galaxies, none of our four blobs are radio-loud. The X-ray luminosities and optical spectra of these blobs are diverse. Two blobs (3 and 4) are X-ray-detected with L_X(2-7 keV) = 2-4 x 10^44 ergs/s and have broad optical emission lines (C IV) characteristic of AGN, implying that 50% of our sample blobs are associated with strong AGN. The other 50% of blobs (1 and 2) are not X-ray or optically-detected as AGN down to similar limits. The number density of the four blobs is ~3 x 10^{-6} Mpc^{-3}, comparable to that of galaxy clusters at similar redshifts and 3x lower than that found in the SSA22 proto-cluster at z=3.1, even after accounting for the over-density of that region. The two X-ray undetected blobs are separated by only 70" (550 kpc) and have almost identical redshifts (< 360 kpc along the line-of-sight), suggesting that they are part of the same system. Given the rarity of the blobs and our discovery of a close pair, we speculate that blobs occupy the highest density regions and thus may be precursors of today's rich cluster galaxies.

We study the nature of faint, red-selected galaxies at z ~ 2-3 using the Hubble Ultra Deep Field (HUDF) and Spitzer IRAC photometry. We detect candidate galaxies to H 1.0 mag color selection, 16 of which have unblended [3.6um] and [4.5um] IRAC photometry. We derive photometric redshifts, masses, and stellar population parameters for these objects. We find that the selected objects span a diverse range of properties over a large range of redshifts, 1 2.5 objects that are dominated by evolved stellar populations have a space density at most one-third that of z ~ 0 red, early-type galaxies. Therefore, at least two-thirds of present-day early-type galaxies assemble or evolve into their current configuration at redshifts below 2.5. We find a dearth of candidates for low-mass galaxies at 1.5 < z < 3 that are dominated by passively evolving stellar populations even though the data should be sensitive to them; thus, at these redshifts, galaxies whose light is dominated by evolved stellar populations are restricted to only those galaxies that have assembled high stellar mass.[Abridged]

We built an optimal basis of low resolution templates for galaxies over the wavelength range from 0.2 to 10 $\mu$m using a variant of the algorithm presented by Budavari et al. (2000). We derived them using eleven bands of photometry from the NDWFS, FLAMEX, zBo\"otes and IRAC Shallow surveys for 16033 galaxies in the NDWFS Bo\"otes field with spectroscopic redshifts measured by the AGN and Galaxy Evolution Survey. We also developed algorithms to accurately determine photometric redshifts, K corrections and bolometric luminosities using these templates. Our photometric redshifts have an accuracy of $\sigma_z/(1+z) = 0.04$ when clipped to the best 95%. We used these templates to study the spectral type distribution in the field and to estimate luminosity functions of galaxies as a function of redshift and spectral type. In particular, we note that the 5-8$\mu$m color distribution of galaxies is bimodal, much like the optical g--r colors.

We report the first results of our systematic search for strongly lensed quasars using the spectroscopically confirmed quasars in the Sloan Digital Sky Survey (SDSS). Among 46,420 quasars from the SDSS Data Release 3 (~4188 deg^2), we select a subsample of 22,683 quasars that are located at redshifts between 0.6 and 2.2 and are brighter than the Galactic extinction corrected i-band magnitude of 19.1. We identify 220 lens candidates from the quasar subsample, for which we conduct extensive and systematic follow-up observations in optical and near-infrared wavebands, in order to construct a complete lensed quasar sample at image separations between 1'' and 20'' and flux ratios of faint to bright lensed images larger than 10^{-0.5}. We construct a statistical sample of 11 lensed quasars. Ten of these are galaxy-scale lenses with small image separations (~1''-2'') and one is a large separation (15'') system which is produced by a massive cluster of galaxies, representing the first statistical sample of lensed quasars including both galaxy- and cluster-scale lenses. The Data Release 3 spectroscopic quasars contain an additional 11 lensed quasars outside the statistical sample., Comment: 15 pages, 4 figures, 5 tables, accepted for publication in AJ; see http://www-utap.phys.s.u-tokyo.ac.jp/~sdss/sqls/ for supplemental information

We discuss the effects of non-linear structure formation on the signature of acoustic oscillations in the late-time galaxy distribution. We argue that the dominant non-linear effect is the differential motion of pairs of tracers separated by 150 Mpc. These motions are driven by bulk flows and cluster formation and are much smaller than the acoustic scale itself. We present a model for the non-linear evolution based on the distribution of pairwise Lagrangian displacements that provides a quantitative model for the degradation of the acoustic signature, even for biased tracers in redshift space. The Lagrangian displacement distribution can be calibrated with a significantly smaller set of simulations than would be needed to construct a precise power spectrum. By connecting the acoustic signature in the Fourier basis with that in the configuration basis, we show that the acoustic signature is more robust than the usual Fourier-space intuition would suggest because the beat frequency between the peaks and troughs of the acoustic oscillations is a very small wavenumber that is well inside the linear regime. We argue that any possible shift of the acoustic scale is related to infall on 150 Mpc scale, which is O(0.5%) fractionally at first-order even at z=0. For the matter, there is a first-order cancellation such that the mean shift is O(10^{-4}). However, galaxy bias can circumvent this cancellation and produce a sub-percent systematic bias., Comment: 27 pages, LaTeX. Submitted to the Astrophysical Journal

A Spitzer Space Telescope survey in the NOAO Deep Wide Field in Bootes provides a complete, 8 μm-selected sample of galaxies to a limiting (Vega) magnitude of 13.5. In the 6.88 deg2 field sampled, 79% of the 4867 galaxies have spectroscopic redshifts, allowing an accurate determination of the local (z < 0.3) galaxy luminosity function. Stellar and dust emission can be separated on the basis of observed galaxy colors. Dust emission (mostly PAH) accounts for 80% of the 8 μm luminosity, stellar photospheres account for 19%, and AGN emission accounts for roughly 1%. A subsample of the 8 μm-selected galaxies have blue, early-type colors, but even most of these have significant PAH emission. The luminosity functions for the total 8 μm luminosity and for the dust emission alone are both well fit by Schechter functions. For the 8 μm luminosity function, the characteristic luminosity is νLν*;(8.0 μm) = 1.8 × 1010 L ⊙, while for the dust emission alone it is 1.6 × 10 10 L⊙. The average 8 μm luminosity density at z < 0.3 is 3.1 × 107 L⊙ Mpc-3, and the average luminosity density from dust alone is 2.5 × 107 L⊙ Mpc-3. This luminosity arises predominantly from galaxies with 8 μm luminosities (νLν) between 2 × 109 and 2 × 1010 L⊙, i.e., normal galaxies, not luminous or ultraluminous infrared galaxies (LIRGs/ULIRGs). © 2007. The American Astronomical Society. All rights reserved.

NICMOS observations of the resolved object fluxes in the Hubble Deep Field North and the Hubble Ultra Deep Field are significantly below the fluxes attributed to a 1.4 - 1.8 microns Near InfraRed Background Excess (NIRBE) from previous low spatial resolution NIRS measurements. Tests placing sources in the NICMOS image with fluxes sufficient to account for the NIRBE indicate that the NIRBE flux must be either flat on scales greater than 100 arc second or clumped on scales of several arc minutes to avoid detection in the NICMOS image. A fluctuation analysis of the new NICMOS data shows a fluctuation spectrum consistent with that found at the same wavelength in deep 2MASS calibration images. The fluctuation analysis shows that the majority of the fluctuation power comes from resolved galaxies at redshifts of 1.5 and less and that the fluctuations observed in the earlier deep 2MASS observations can be completely accounted for with normal low redshift galaxies. Neither the NICMOS direct flux measurements nor the fluctuation analysis require an additional component of near infrared flux other than the flux from normal resolved galaxies in the redshift range between 0 and 7. The residual fluctuations in the angular range between 1 and 10 arc seconds is 1-2 nW m-2 sr-1 which is at or above several predictions of fluctuations from high redshift population III objects, but inconsistent with attributing the entire NIRBE to high redshift galaxies., Comment: Accepted for publication in the Astrophysical Journal

We present a Fourier analysis of the clustering of galaxies in the combined main galaxy and LRG SDSS DR5 sample. The aim of our analysis is to consider how well we can measure the cosmological matter density using the signature of the horizon at matter-radiation equality embedded in the large-scale power spectrum. The new data constrain the power spectrum on scales 100-600 h-1 Mpc with significantly higher precision than previous analyses of just the SDSS main galaxies, due to our larger sample and the inclusion of the LRGs. This improvement means that we can now reveal a discrepancy between the shape of the measured power and linear CDM models on scales 0.01 h Mpc-1 < k < 0.15 h Mpc-1, with linear model fits favoring a lower matter density (ΩM = 0.22 ± 0.04) on scales 0.01 h Mpc-1 < k < 0.06 h Mpc-1 and a higher matter density (ΩM = 0.32 ± 0.01) when smaller scales are included, assuming a flat ΛCDM model with h = 0.73 and ns = 0.96. This discrepancy could be explained by scale-dependent bias, and by analyzing subsamples of galaxies, we find that the ratio of small-scale to large-scale power increases with galaxy luminosity, so all of the SDSS galaxies cannot trace the same power spectrum shape over 0.01 h Mpc-1 < k < 0.2 h Mpc-1. However, the data are insufficient to clearly show a luminosity-dependent change in the largest scale at which a significant increase in clustering is observed, although they do not rule out such an effect. Significant scale-dependent galaxy bias on large scales, which changes with the r-band luminosity of the galaxies, could potentially explain differences in our ΩM estimates and differences previously observed between 2dFGRS and SDSS power spectra and the resulting parameter constraints.

We study the distribution of Eddington luminosity ratios, L_bol/L_edd, of active galactic nuclei (AGNs) discovered in the AGN and Galaxy Evolution Survey (AGES). We combine H-beta, MgII, and CIV line widths with continuum luminosities to estimate black hole (BH) masses in 407 AGNs, covering the redshift range z~0.3-4 and the bolometric luminosity range L_bol~10^45-10^47 erg/s. The sample consists of X-ray or mid-infrared (24 micron) point sources with optical magnitude R

We use the NICMOS Treasury and ACS HUDF images to measure the extinction corrected star formation history for 4681 galaxies in the region common to both images utilizing the star formation rate distribution function and other techniques similar to those employed with the NICMOS and WFPC2 images in the HDFN. Unlike the HDFN the NICMOS region of the HUDF appears to lack highly luminous and high star formation rate galaxies at redshifts beyond 3. The HUDF provides a region that is completely uncorrelated to the HDFN and therefore provides and independent measure of the star formation history of the universe. The combined HUDF and HDFN star formation rates show an average star formation rate of 0.2 solar masses per yer per cubic megaparsec. The average SFR of the combined fields at z = 1-3 is 0.29 solar masses per year per cubic megaparsec while the average at z = 4-6 is 1.2 solar masses per year per cubic megaparsec. The SFRs at all redshifts are within 3 sigma of the average over all redshifts.

We present the discovery of three z>5 quasars in the AGN and Galaxy Evolution Survey (AGES) spectroscopic observations of the NOAO Deep Wide-Field Survey (NDWFS) Bootes Field. These quasars were selected as part of a larger Spitzer mid-infrared quasar sample with no selection based on optical colors. The highest redshift object, NDWFS J142516.3+325409, z=5.85, is the lowest-luminosity z>5.8 quasar currently known. We compare mid-infrared techniques for identifying z>5 quasars to more traditional optical techniques and show that mid-infrared colors allow for selection of high-redshift quasars even at redshifts where quasars lie near the optical stellar locus and at z>7 where optical selection is impossible. Using the superb multi-wavelength coverage available in the NDWFS Bootes field, we construct the spectral energy distributions (SEDs) of high-redshift quasars from observed Bw-band to 24 microns (rest-frame 600 Angstroms - 3.7 microns). We show that the three high-redshift quasars have quite similar SEDs, and the rest-frame composite SED of low-redshift quasars from the literature shows little evolution compared to our high-redshift objects. We compare the number of z>5 quasars we have discovered to the expected number from published quasar luminosity functions. While analyses of the quasar luminosity function are tenuous based on only three objects, we find that a relatively steep luminosity function with Psi L^(-3.2) provides the best agreement with the number of high-redshift quasars discovered in our survey., Comment: 9 page, 7 figures. Accepted for publication in AJ

We present a spectroscopic survey using the MMT/Hectospec fiber spectrograph of 24 micron sources selected with the Spitzer Space Telescope in the Spitzer First Look Survey. We report 1296 new redshifts for 24 micron sources, including 599 with f(24micron) > 1 mJy. Combined with 291 additional redshifts for sources from the Sloan Digital Sky Survey (SDSS), our observing program was highly efficient and is ~90% complete for i' < 21 mag and f(24micron) > 1 mJy, and is 35% complete for i' < 20.5 mag and 0.3 mJy < f(24micron) < 1 mJy. Our Hectospec survey includes 1078 and 168 objects spectroscopically classified as galaxies and QSOs, respectively. Combining the Hectospec and SDSS samples, we find 24 micron-selected galaxies to z < 0.98 and QSOs to z < 3.6, with mean redshifts of = 0.27 and =1.1. As part of this publication, we include the redshift catalogs and the reduced spectra; these are also available online (http://mips.as.arizona.edu/~papovich/fls) and through the NASA/IPAC Infrared Science Archive (http://irsa.ipac.caltech.edu)., Accepted for publication in the Astronomical Journal, AASTEX format, 23 pages, 7 figures (some in color). This replacement is the accepted version, and includes minor changes from previous version. Data tables and spectra available at http://mips.as.arizona.edu/~papovich/fls or at http://irsa.ipac.caltech.edu

In this paper we present the first results of a deep spectroscopic survey of faint quasars in the Sloan Digital Sky Survey (SDSS) Southern Survey, a deep survey carried out by repeatedly imaging a 270 deg^2 area. Quasar candidates were selected from the deep data with good completeness over 02.0) at the faint end, indicating a break in the QLF slope. Using a luminosity-dependent density evolution model, we find that the quasar density at M_{g}, Comment: 25 pages, 13 figures, accepted for publication in AJ

We describe the serendipitous discovery in the spectroscopic data of the Sloan Digital Sky Survey of a star-like object, SDSSJ103913.70+533029.7, at a heliocentric radial velocity of +1012 km/s. Its proximity in position and velocity to the spiral galaxy NGC 3310 suggests an association with the galaxy. At this distance, SDSSJ103913.70+533029.7 has the luminosity of a super star cluster and a projected distance of 17 kpc from NGC 3310. Its spectroscopic and photometric properties imply a mass of > 10^6 solar masses and an age close to that of the tidal shells seen around NGC 3310, suggesting that it formed in the event which formed the shells., Accepted by AJ: 4 figures (1 color)

A sample of white dwarfs is selected from SDSS DR3 imaging data using their reduced proper motions, based on improved proper motions from SDSS plus USNO-B combined data. Numerous SDSS and followup spectra (Kilic et al. 2005) are used to quantify completeness and contamination of the sample; kinematic models are used to understand and correct for velocity-dependent selection biases. A luminosity function is constructed covering the range 7 < M_bol < 16, and its sensitivity to various assumptions and selection limits is discussed. The white dwarf luminosity function based on 6000 stars is remarkably smooth, and rises nearly monotonically to M_bol = 15.3. It then drops abruptly, although the small number of low-luminosity stars in the sample and their unknown atmospheric composition prevent quantitative conclusions about this decline. Stars are identified that may have high tangential velocities, and a preliminary luminosity function is constructed for them.

We report on i-band snapshot observations of 157 Sloan Digital Sky Survey (SDSS) quasars at 4 -3.8 (3 sigma), assuming a break in the quasar luminosity function at M_1450^star=-24.5. This constraint is considerably stronger than the limit of beta>-4.63 obtained from the absence of lensing in four z>5.7 quasars. Such constraints are important for our understanding of the true space density of high-redshift quasars and the ionization state of the early universe.

We report the discovery of a new two-image gravitationally lensed quasar, SDSS J024634.11-082536.2 (SDSS J0246-0825). This object was selected as a lensed quasar candidate from the Sloan Digital Sky Survey (SDSS) by the same algorithm that was used to discover other SDSS lensed quasars (e.g., SDSS J0924+0219). Multicolor imaging with the Magellan Consortium's Walter Baade 6.5-m telescope and the spectroscopic observations using the W. M. Keck Observatory's Keck II telescope confirm that SDSS J0246-0825 consists of two lensed images ($\Delta{\theta}=$1\farcs04) of a source quasar at z=1.68. Imaging observations with the Keck telescope and the Hubble Space Telescope reveal an extended object between the two quasar components, which is likely to be a lensing galaxy of this system. From the absorption lines in the spectra of quasar components and the apparent magnitude of the galaxy, combined with the expected absolute magnitude from the Faber-Jackson relation, we estimate the redshift of the lensing galaxy to be z=0.724. A highly distorted ring is visible in the Hubble Space Telescope images, which is likely to be the lensed host galaxy of the source quasar. Simple mass modeling predicts the possibility that there is a small (faint) lensing object near the primary lensing galaxy.

We study the relationship between galaxy luminosity, color, and environment in a cosmological simulation of galaxy formation. We compare the predicted relationship with that found for SDSS galaxies and find that the model successfully predicts most of the qualitative features seen in the data, but also shows some interesting differences. Specifically, the simulation predicts that the local density around bright red galaxies is a strong increasing function of luminosity, but does not depend much on color at fixed luminosity. Moreover, we show that this is due to central galaxies in dark matter halos whose baryonic masses correlate strongly with halo mass. The simulation also predicts that the local density around blue galaxies is a strong increasing function of color, but does not depend much on luminosity at fixed color. We show that this is due to satellite galaxies in halos whose stellar ages correlate with halo mass. Finally, the simulation fails to predict the luminosity dependence of environment observed around low luminosity red galaxies. However, we show that this is most likely due to the simulation's limited resolution. A study of a higher resolution, smaller volume simulation suggests that this dependence is caused by the fact that all low luminosity red galaxies are satellites in massive halos, whereas intermediate luminosity red galaxies are a mixture of satellites in massive halos and central galaxies in less massive halos., 8 pages including 5 figures (emulateapj). Submitted to ApJ

We examine the relationship between environment and the luminosities, surface brightnesses, colors, and profile shapes of luminous galaxies in the Sloan Digital Sky Survey (SDSS). For the SDSS sample, galaxy color is the galaxy property most predictive of the local environment. Galaxy color and luminosity jointly comprise the most predictive pair of properties. At fixed luminosity and color, density is not closely related to surface brightness or to Sersic index -- the parameter in this study that astronomers most often associate with morphology. In the text, we discuss what measureable residual relationships exist, generally finding that at red colors and fixed luminosity, the mean density decreases at the highest surface brightnesses and Sersic indices. In general, these results suggest that the morphological properties of galaxies are less closely related to galaxy environment than are their masses and star-formation histories.

Fifty-two magnetic white dwarfs have been identified in spectroscopic observations from the Sloan Digital Sky Survey (SDSS) obtained between mid-2002 and the end of 2004, including Data Releases 2 and 3. Though not as numerous nor as diverse as the discoveries from the first Data Release, the collection exhibits polar field strengths ranging from 1.5MG to ~1000MG, and includes two new unusual atomic DQA examples, a molecular DQ, and five stars that show hydrogen in fields above 500MG. The highest-field example, SDSSJ2346+3853, may be the most strongly magnetic white dwarf yet discovered. Analysis of the photometric data indicates that the magnetic sample spans the same temperature range as for nonmagnetic white dwarfs from the SDSS, and support is found for previous claims that magnetic white dwarfs tend to have larger masses than their nonmagnetic counterparts. A glaring exception to this trend is the apparently low-gravity object SDSSJ0933+1022, which may have a history involving a close binary companion., Comment: 20 pages, 4 figures Accepted for publication in the Astronomical Journal

This paper describes the observations and data reduction techniques for the version 2.0 images and catalog of the NICMOS Ultra Deep Field Treasury program. All sources discussed in this paper are based on detections in the combined NICMOS F110W and F160W bands only. The NICMOS images are drizzled to 0.09 arc second pixels and aligned to the ACS UDF F850LP image which was rebinned to the same pixel scale. These form the NICMOS version 2.0 UDF images. The catalog sources are chosen with a conservative detection limit to avoid the inclusion of numerous spurious sources. The catalog contains 1293 objects in the 144 x 144 arc sececonds NICMOS subfield of the UDF. The 5 sigma signal to noise level is an average 0.6 arc second diameter aperture AB magnitude of ~27.7 at 1.1 and 1.6 microns. The catalog sources, listed in order of right ascension, satisfy a minimum signal to noise criterion of 1.4 sigma in at least 7 contiguous pixels of the combined F110W and F160W image

We report the discovery of 11 new variable DA white dwarf (ZZ Ceti) stars. Candidates were selected by deriving temperatures from model fits to spectra obtained from the Sloan Digital Sky Survey (SDSS). We also find objects whose temperatures and gravities indicate they lie within the instability strip for pulsation but were not observed to vary. Although the temperatures are based on relatively low signal-to-noise ratio spectra, an impure strip is unexpected, which if confirmed, has implications for DA asteroseismology. This work brings the total number of published variable DA white dwarf stars to 82.

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., 14 pages, including 2 postscript figures. Submitted to AJ. Data available at http://www.sdss.org/dr3

We have detected likely z~7-8 galaxies in the 144"x144" NICMOS observations of the Hubble Ultra Deep Field. Objects are required to be >3 sigma detections in both NICMOS bands, J and H. The selection criteria for this sample are (z-J)>0.8, (z-J) > 0.66 (J-H)+0.8, (J-H)

The z=3.02 quasar SDSS J095253.83+011421.9 exhibits broad metal-line emission (CIV FWHM=9000 km/s), but broad Ly-alpha emission is not present. Instead, only a narrow Ly-alpha line is observed (FWHM=1140 km/s). The large CIV/Ly-alpha ratio in the broad-line region (BLR) emission from this object can be matched most closely by a BLR dominated by gas at very high densities (10^15 cm^-3), which suppresses the Ly-alpha emission, and illuminated by an incident power-law extending to ~200 micron, which yields increased emission from purely collisionally excited coolant lines (such as CIV, NV and OVI) but not from recombination lines like Ly-alpha. However, the strong CIII emission predicted by this model is not observed, and the observed broad CIII] emission must come from a lower-density BLR component and should be accompanied by broad Ly-alpha emission which is not observed. The least unlikely explanation for this spectrum seems to be that any intrinsic broad Ly-alpha emission is removed by smooth NV absorption in the red wing of the Ly-alpha emission line and by smooth Ly-alpha absorption in the blue wing of the Ly-alpha emission line. This postulated smooth absorption would be in addition to the strong, associated, narrow absorption seen in numerous ions. Smooth absorption in Ly-alpha, NV and OVI but not in CIV would be unusual, but not impossible, although it is suspicious that the postulated absorption must almost exactly cancel the postulated intrinsic broad emission. We conclude that the spectrum of SDSS J0952+0114 appears unique (among ~3600 SDSS spectra of quasars at z>2.12) because of some_combination_ of unusual parameters, and we discuss possible observations to determine the combination of circumstances responsible for the spectrum.

The Sloan Digital Sky Survey has validated and made publicly available its Second Data Release. This data release consists of 3324 square degrees of five-band (u g r i z) imaging data with photometry for over 88 million unique objects, 367,360 spectra of galaxies, quasars, stars and calibrating blank sky patches selected over 2627 degrees of this area, and tables of measured parameters from these data. The imaging data reach a depth of r ~ 22.2 (95% completeness limit for point sources) and are photometrically and astrometrically calibrated to 2% rms and 100 milli-arcsec rms per coordinate, respectively. The imaging data have all been processed through a new version of the SDSS imaging pipeline, in which the most important improvement since the last data release is fixing an error in the model fits to each object. The result is that model magnitudes are now a good proxy for point spread function (PSF) magnitudes for point sources, and Petrosian magnitudes for extended sources. The spectroscopy extends from 3800 A to 9200 A at a resolution of 2000. The spectroscopic software now repairs a systematic error in the radial velocities of certain types of stars, and has substantially improved spectrophotometry. All data included in the SDSS Early Data Release and First Data Release are reprocessed with the improved pipelines, and included in the Second Data Release. The data are publically available as of 2004 March 15 via the web sites http://www.sdss.org/dr2 and http://skyserver.sdss.org ., 24 pages, submitted to AJ. See ftp://ftp.astro.princeton.edu/strauss/sdss/dr2.ps for high-resolution figures

We present estimates of cosmological parameters from the application of the Karhunen-Loeve transform to the analysis of the 3D power spectrum of density fluctuations using Sloan Digital Sky Survey galaxy redshifts. We use Omega_m*h and f_b = Omega_b/Omega_m to describe the shape of the power spectrum, sigma8 for the (linearly extrapolated) normalization, and beta to parametrize linear theory redshift space distortions. On scales k < 0.16 h/Mpc, our maximum likelihood values are Omega_m*h = 0.264 +/-0.043, f_b = 0.286 +/- 0.065, sigma8 = 0.966 +/- 0.048, and beta = 0.45 +/- 0.12. When we take a prior on Omega_b from WMAP, we find Omega_m*h = 0.207 +/- 0.030, which is in excellent agreement with WMAP and 2dF. This indicates that we have reasonably measured the gross shape of the power spectrum but we have difficulty breaking the degeneracy between Omega_m*h and f_b because the baryon oscillations are not resolved in the current spectroscopic survey window function., LaTeX, 8 pages, 3 figures; figures updated, references added, minor changes to text; accepted by ApJ

We measure the large-scale real-space power spectrum P(k) using a sample of 205,443 galaxies from the Sloan Digital Sky Survey, covering 2417 square degrees with mean redshift z~0.1. We employ a matrix-based method using pseudo-Karhunen-Loeve eigenmodes, producing uncorrelated minimum-variance measurements in 22 k-bands of both the clustering power and its anisotropy due to redshift-space distortions, with narrow and well-behaved window functions in the range 0.02 h/Mpc < k < 0.3h/Mpc. We pay particular attention to modeling, quantifying and correcting for potential systematic errors, nonlinear redshift distortions and the artificial red-tilt caused by luminosity-dependent bias. Our final result is a measurement of the real-space matter power spectrum P(k) up to an unknown overall multiplicative bias factor. Our calculations suggest that this bias factor is independent of scale to better than a few percent for k

We report on the i-dropouts detected in two exceptionally deep ACS fields (B_{435}, V_{606}, i_{775}, and z_{850} with 10 sigma limits of 28.8, 29.0, 28.5, and 27.8, respectively) taken in parallel with the UDF NICMOS observations. Using an i-z>1.4 cut, we find 30 i-dropouts over 21 arcmin^2 down to z_AB=28.1, or 1.4 i-dropouts arcmin^{-2}, with significant field-to-field variation (as expected from cosmic variance). This extends i-dropout searches some ~0.9^m further down the luminosity function than was possible in the GOODS field, netting a ~7x increase in surface density. An estimate of the size evolution for UV bright objects is obtained by comparing the composite radial flux profile of the bright i-dropouts (z

We present a catalog of 49 spectroscopic strong gravitational lens candidates selected from a Sloan Digital Sky Survey sample of 50996 luminous red galaxies. Potentially lensed star-forming galaxies are detected through the presence of background oxygen and hydrogen nebular emission lines in the spectra of these massive foreground galaxies. This multiline selection eliminates the ambiguity of single-line identification and provides a very promising sample of candidate galaxy-galaxy lens systems at low to intermediate redshift, with foreground redshifts ranging from 0.16 to 0.49 and background redshifts from 0.25 to 0.81. Any lenses confirmed within our sample would be important new probes of early-type galaxy mass distributions, providing complementary constraints to those obtained from currently known lensed high-redshift quasars., 23 pages; to appear in The Astronomical Journal, 2004 April. Version with full-resolution figures available at http://web.mit.edu/bolton/www/speclens.ps.gz (PostScript) or http://web.mit.edu/bolton/www/speclens.pdf (PDF)

We discuss 18 white dwarfs, one of which (G227-5) was previously known, whose SDSS spectra show lines of neutral and/or singly ionized carbon. At least two and perhaps four show lines of neutral or singly ionized oxygen. Apart from the extremely hot PG 1159 stars, these are the first white dwarfs with photospheric oxygen detected in their optical spectra. The photometry strongly suggests that these stars lie in the 11,000–30,000 K temperature range of the helium-atmosphere DB white dwarfs, though only one of them shows weak neutral helium lines in the spectrum. Trigonometric parallaxes are known for G227-5 and another, previously known white dwarf (G35-26) showing atomic carbon lines, and they indicate that both are massive stars. Theoretical arguments suggest that all members of this class of rare white dwarfs are massive (~1 M⊙), and this finding could explain the paucity of massive DB white dwarfs.

We report the discovery of a new gravitationally lensed quasar from the Sloan Digital Sky Survey, SDSS J090334.92+502819.2. This object was targeted for SDSS spectroscopy as a Luminous Red Galaxy (LRG), but manual examination of the spectrum showed the presence of a quasar at z= 3.6 in addition to a red galaxy at z=0.388, and the SDSS image showed a second possible quasar image nearby. Follow-up imaging and spectroscopy confirmed the lensing hypothesis. In images taken at the ARC 3.5-meter telescope, two quasars are separated by 2.8 arc-seconds; the lensing galaxy is clearly seen and is blended with one of the quasar images. Spectroscopy taken at the Keck II telescope shows that the quasars have identical redshifts of z=3.6 and both show the presence of the same broad absorption line-like troughs. We present simple lens models which account for the geometry and magnifications. The lens galaxy lies near two groups of galaxies and may be a part of them. The models suggest that the groups may contribute considerable shear and may have a strong effect on the lens configuration.

Beyond its goals related to the extragalactic universe, the Sloan Digital Sky Survey (SDSS) is an effective tool for identifying stellar objects with unusual spectral energy distributions. Here we report on the 53 new magnetic white dwarfs discovered during the first two years of the survey, including 38 whose data are made public in the 1500 square-degree First Data Release. Discoveries span the magnitude range 16.3 3 MG and g > 15. The new objects nearly double the total number of known magnetic white dwarfs, and include examples with polar field strengths B > 500 MG as well as several with exotic atmospheric compositions. The improved sample statistics and uniformity indicate that the distribution of magnetic white dwarfs has a broad peak in the range ~5-30 MG and a tail extending to nearly 10^9 G. Degenerates with polar fields B > 50 MG are consistent with being descendents of magnetic Ap/Bp main-sequence stars, but low- and moderate-field magnetic white dwarfs appear to imply another origin. Yet-undetected magnetic F-type stars with convective envelopes that destroy the ordered underlying field are attractive candidates.

Using photometry and spectroscopy of 183,487 galaxies from the Sloan Digital Sky Survey, we present bivariate distributions of pairs of seven galaxy properties: four optical colors, surface brightness, radial profile shape as measured by the Sersic index, and absolute magnitude. In addition, we present the dependence of local galaxy density (smoothed on 8 h(-1) Mpc scales) on all of these properties. Several classic, well-known relations among galaxy properties are evident at extremely high signal-to-noise ratio: the color-color relations of galaxies, the color-magnitude relations, the magnitude-surface brightness relation, and the dependence of density on color and absolute magnitude. We show that most of the i-band luminosity density in the universe is in the absolute magnitude and surface brightness ranges used: - 23.5 < M-0,M-1i < - 17.0 mag and 17 < mu(0.1i) < 24 mag in 1 arcsec(2) [ the notation (z)b represents the b band shifted blueward by a factor (1 + z)]. Some of the relationships between parameters, in particular the color-magnitude relations, show stronger correlations for exponential galaxies and concentrated galaxies taken separately than for all galaxies taken together. We provide a simple set of fits of the dependence of galaxy properties on luminosity for these two sets of galaxies and other quantitative details of our results.

We report the discovery of a new gravitationally lensed quasar from the Sloan Digital Sky Survey, SDSS J092455.87+021924.9 (SDSS J0924+0219). This object was selected from among known SDSS quasars by an algorithm that was designed to select another known SDSS lensed quasar (SDSS 1226-0006A,B). Five separate components, three of which are unresolved, are identified in photometric follow-up observations obtained with the Magellan Consortium's 6.5m Walter Baade telescope at Las Campanas Observatory. Two of the unresolved components (designated A and B) are confirmed to be quasars with z=1.524; the velocity difference is less than 100 km sec^{-1} according to spectra taken with the W. M. Keck Observatory's Keck II telescope on Mauna Kea. A third stellar component, designated C, has the colors of a quasar with redshift similar to components A and B. The maximum separation of the point sources is 1.78". The other two sources, designated G and D, are resolved. Component G appears to be the best candidate for the lensing galaxy. Although component D is near the expected position of the fourth lensed component in a four image lens system, its properties are not consistent with being the image of a quasar at z~1.5. Nevertheless, the identical redshifts of components A and B and the presence of component C strongly suggest that this object is a gravitational lens. Our observations support the idea that a foreground object reddens the fourth lensed component and that another unmodeled effect (such as micro- or milli-lensing) demagnificates it, but we cannot rule out the possibility that SDSS0924+0219 is an example of the relatively rare class of ``three component'' lens systems., 24 pages, 6 figures, accepted by AJ

We present measurements of parameters of the 3-dimensional power spectrum of galaxy clustering from 222 square degrees of early imaging data in the Sloan Digital Sky Survey. The projected galaxy distribution on the sky is expanded over a set of Karhunen-Loeve eigenfunctions, which optimize the signal-to-noise ratio in our analysis. A maximum likelihood analysis is used to estimate parameters that set the shape and amplitude of the 3-dimensional power spectrum. Our best estimates are Gamma=0.188 +/- 0.04 and sigma_8L = 0.915 +/- 0.06 (statistical errors only), for a flat Universe with a cosmological constant. We demonstrate that our measurements contain signal from scales at or beyond the peak of the 3D power spectrum. We discuss how the results scale with systematic uncertainties, like the radial selection function. We find that the central values satisfy the analytically estimated scaling relation. We have also explored the effects of evolutionary corrections, various truncations of the KL basis, seeing, sample size and limiting magnitude. We find that the impact of most of these uncertainties stay within the 2-sigma uncertainties of our fiducial result.

A magnitude limited sample of nearly 9000 early-type galaxies, in the redshift range 0.01 ≤ z ≤ 0.3, was selected from the Sloan Digital Sky Survey using morphological and spectral criteria. The sample was used to study how early-type galaxy observables, including luminosity L, effective radius Ro, surface brightness Io, color, and velocity dispersion σ, are correlated with one another. Measurement biases are understood with mock catalogs which reproduce all of the observed scaling relations and their dependences on fitting technique. At any given redshift, the intrinsic distribution of luminosities, sizes and velocity dispersions in our sample are all approximately

A magnitude limited sample of nearly 9000 early-type galaxies, in the redshift range 0.01 < z < 0.3, was selected from the Sloan Digital Sky Survey using morphological and spectral criteria. The Fundamental Plane relation in this sample is R_o ~ sigma^{1.49\pm 0.05} I_o^{-0.75\pm 0.01} in the r* band. It is approximately the same in the g*, i* and z* bands. Relative to the population at the median redshift in the sample, galaxies at lower and higher redshifts have evolved only little. If the Fundamental Plane is used to quantify this evolution then the apparent magnitude limit can masquerade as evolution; once this selection effect has been accounted for, the evolution is consistent with that of a passively evolving population which formed the bulk of its stars about 9 Gyrs ago. One of the principal advangtages of the SDSS sample over previous samples is that the galaxies in it lie in environments ranging from isolation in the field to the dense cores of clusters. The Fundamental Plane shows that galaxies in dense regions are slightly different from galaxies in less dense regions.

A sample of nearly 9000 early-type galaxies, in the redshift range 0.01 < z < 0.3, was selected from the Sloan Digital Sky Survey using morphological and spectral criteria. This paper describes how the sample was selected, presents examples of images and seeing corrected fits to the observed surface brightness profiles, describes our method for estimating K-corrections, and shows that the SDSS spectra are of sufficiently high quality to measure velocity dispersions accurately. It also provides catalogs of the measured photometric and spectroscopic parameters. In related papers, these data are used to study how early-type galaxy observables, including luminosity, effective radius, surface brightness, color, and velocity dispersion, are correlated with one another.