DanielJ.Eisenstein,Jam esAnnis,Jam esE.G unn,AlexanderS.Szalay,Andrew J.Connolly, R.C.Nichol,Neta A.Bahcall,M ariangela Bernardi,ScottBurles,Francisco J.Castander, M asataka Fukugita,David W .Hogg, Zeljko Ivezi c,G .R.K napp,RobertH.Lupton, Vijay Narayanan,M arcPostm an,DanielE.Reichart,M ichaelRichm ond Donald P.Schneider, David J.Schlegel,M ichaelA.Strauss,M ark SubbaRao,DouglasL.Tucker,DanielVanden Berk, M ichaelS.Vogeley,David H.W einberg,Brian Yanny

ABSTRACT The rest-frame far to extreme ultraviolet (UV) colour–redshift relationship has been constructed from data on over $480\, 000$ quasars carefully cross-matched between SDSS Data Release 14 and the final GALEX photometric catalogue. UV matching and detection probabilities are given for all the quasars, including dependencies on separation, optical brightness, and redshift. Detection limits are also provided for all objects. The UV colour distributions are skewed redward at virtually all redshifts, especially when detection limits are accounted for. The median GALEX far-UV minus near-UV (FUV − NUV) colour–redshift relation is reliably determined up to z ≈ 2.8, corresponding to rest-frame wavelengths as short as 400 Å. Extreme UV (EUV) colours are substantially redder than found previously, when detection limits are properly accounted for. Quasar template spectra were forward modelled through the GALEX bandpasses, accounting for intergalactic opacity, intrinsic reddening, and continuum slope variations. Intergalactic absorption by itself cannot account for the very red EUV colours. The colour–redshift relation is consistent with no intrinsic reddening, at least for SMC-like extinction. The best model fit has a FUV continuum power-law slope αν, FUV = −0.34 ± 0.03 consistent with previous results, but an EUV slope αν, EUV = −2.90 ± 0.04 that is much redder and inconsistent with any previous composite value (all ≳ −2.0). The EUV slope difference can be attributed in part to the tendency of previous studies to preferentially select UV brighter and bluer objects. The weak EUV flux suggests quasar accretion disc models that include outflows such as disc winds.

We describe here the most ambitious survey currently planned in the optical, the Large Synoptic Survey Telescope (LSST). The LSST design is driven by four main science themes: probing dark energy and dark matter, taking an inventory of the solar system, exploring the transient optical sky, and mapping the Milky Way. LSST will be a large, wide-field ground-based system designed to obtain repeated images covering the sky visible from Cerro Pachón in northern Chile. The telescope will have an 8.4 m (6.5 m effective) primary mirror, a 9.6 deg 2 field of view, a 3.2-gigapixel camera, and six filters ( ugrizy ) covering the wavelength range 320–1050 nm. The project is in the construction phase and will begin regular survey operations by 2022. About 90% of the observing time will be devoted to a deep-wide-fast survey mode that will uniformly observe a 18,000 deg 2 region about 800 times (summed over all six bands) during the anticipated 10 yr of operations and will yield a co-added map to r ∼ 27.5. These data will result in databases including about 32 trillion observations of 20 billion galaxies and a similar number of stars, and they will serve the majority of the primary science programs. The remaining 10% of the observing time will be allocated to special projects such as Very Deep and Very Fast time domain surveys, whose details are currently under discussion. We illustrate how the LSST science drivers led to these choices of system parameters, and we describe the expected data products and their characteristics.

Max Tegmark, Michael A. Strauss, Michael R. Blanton, Kevork Abazajian, Scott Dodelson, Havard Sandvik, Xiaomin Wang, David H. Weinberg, Idit Zehavi, Neta A. Bahcall, Fiona Hoyle, David Schlegel, Roman Scoccimarro, Michael S. Vogeley, Andreas Berlind, Tamás Budavari, Andrew Connolly, Daniel J. Eisenstein, Douglas Finkbeiner, Joshua A. Frieman, James E. Gunn, Lam Hui, Bhuvnesh Jain, David Johnston, Stephen Kent, Huan Lin, Reiko Nakajima, Robert C. Nichol, Jeremiah P. Ostriker, Adrian Pope, Ryan Scranton, Uroš Seljak, Ravi K. Sheth, Albert Stebbins, Alexander S. Szalay, István Szapudi, Yongzhong Xu, James Annis, J. Brinkmann, Scott Burles, Francisco J. Castander, Istvan Csabai, Jon Loveday, Mamoru Doi, Masataka Fukugita, Bruce Gillespie, Greg Hennessy, David W. Hogg, Željko Ivezić, Gillian R. Knapp, Don Q. Lamb, Brian C. Lee, Robert H. Lupton, Timothy A. McKay, Peter Kunszt, Jeffrey A. Munn, Liam O’Connell, John Peoples, Jeffrey R. Pier, Michael Richmond, Constance Rockosi, Donald P. Schneider, Christopher Stoughton, Douglas L. Tucker, Daniel E. Vanden Berk, Brian Yanny, Donald G. York Department of Physics, University of Pennsylvania, Philadelphia, PA 19104, USA; Dept. of Physics, Massachusetts Institute of Technology, Cambridge, MA 02139; Center for Cosmology and Particle Physics, Department of Physics, New York University, 4 Washington Place, New York, NY 10003; Princeton University Observatory, Princeton, NJ 08544, USA; Department of Physics, Drexel University, Philadelphia, PA 19104, USA; Department of Astronomy, Ohio State University, Columbus, OH 43210, USA; Fermi National Accelerator Laboratory, P.O. Box 500, Batavia, IL 60510, USA; Center for Cosmological Physics and Department of Astronomy & Astrophysics, University of Chicago, Chicago, IL 60637, USA; Department of Physics and Astronomy, The Johns Hopkins University, 3701 San Martin Drive, Baltimore, MD 21218, USA; University of Pittsburgh, Department of Physics and Astronomy, 3941 O’Hara Street, Pittsburgh, PA 15260, USA; Department of Astronomy, University of Arizona, Tucson, AZ 85721, USA; Department of Physics, 5000 Forbes Avenue, Carnegie Mellon University, Pittsburgh, PA 15213, USA; Institute for Astronomy, University of Hawaii, 2680 Woodlawn Drive, Honolulu, HI 96822, USA; Apache Point Observatory, 2001 Apache Point Rd, Sunspot, NM 88349-0059, USA; Institut d’Estudis Espacials de Catalunya/CSIC, Gran Capita 2-4, 08034 Barcelona, Spain; Sussex Astronomy Centre, University of Sussex, Falmer, Brighton BN1 9QJ, UK; Institute of Astronomy, Univ. of Tokyo, Kashiwa 277-8582, Japan; U.S. Naval Observatory, Flagstaff Station, Flagstaff, AZ 86002-1149, USA; Dept. of Physics, Univ. of Michigan, Ann Arbor, MI 48109-1120, USA; Physics Dept., Rochester Inst. of Technology, 1 Lomb Memorial Dr, Rochester, NY 14623, USA; Dept. of Astronomy and Astrophysics, Pennsylvania State University, University Park, PA 16802, USA; Enrico Fermi Institute, University of Chicago, Chicago, IL 60637, USA; Theoretical Division, MS B285, Los Alamos National Laboratory, Los Alamos, New Mexico 87545, USA;

We studied dust reddening and [O II] emission in 1730 Mg II associated absorption systems (AAS; relative velocity with respect to QSOs, <= 3000 km s(-1); in units of velocity of light, beta, <= 0.01) with 0.4 <= Z(abs) <= 2 in the Sloan Digital Sky Survey DR7, focusing on their dependence on the radio and other QSO properties. We used control samples, several with matching radio properties, to show that (1) AAS in radio-detected (RD) Q50s cause 2.6 +/- 0.2 times higher dust extinction than those in radio-undetected (RUD) ones, which in turn cause 2.9 +/- 0.7 times the dust extinction in the intervening systems; (2) AAS in core-dominated QSOs cause 2.0 +/- 0.1 times higher dust extinction than those in lobe-dominated QSOs; (3) the occurrence of AAS is 2.1 +/- 0.2 times more likely in RD QSOs than in RUD QSOs and 1.8 +/- 0.1 time more likely in QSOs having black holes with masses larger than 1.23 x10(9) M-circle dot than in those with lower-mass black holes; and (4) there is excess flux in [O H])lambda 3727 emission in the composite spectra of the AAS samples compared with those of the control samples, which is at the emission redshift. The presence of AAS enhances the O II emission from the active galactic nucleus and/or the host galaxy. This excess is similar for both RD and RUD samples and is 2.5 +/- 0.4 times higher in lobe-dominated samples than in core-dominated samples. The excess depends on the black hole mass and Eddington ratio. All these point to the intrinsic nature of the AAS except for the systems with z(abs) > z(em), which could be infalling galaxies.

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 3800–9200Å, with a resolution of 1800–2100. Further characteristics of the data are described, as are the data products themselves. Subject headings: Atlases—Catalogs—Surveys Enrico Fermi Institute, The University of Chicago, 5640 S. Ellis Ave., Chicago, IL 60637 Lawrence Berkeley National Laboratory, One Cyclotron Rd., Berkeley CA 94720-8160 Astronomy Centre, University of Sussex, Falmer, Brighton BN1 9QJ, United Kingdom Department of Physics, University of Michigan, 500 East University Ave., Ann Arbor, MI 48109 Institute for Astronomy Royal Observatory Blackford Hill Edinburgh EH9 3HJ Scotland Department of Physics, University of Pennsylvania, Philadelphia, PA 19104 Department of Physics, Applied Physics, and Astronomy, Rensselaer Polytechnic Institute, Troy, NY 12180 Lucent Technologies, 2701 Lucent Lane, Lisle, IL 60532 Department of Astronomy and Research Center for the Early Universe, School of Science, University of Tokyo, 7-3-1 Hongo, Bunkyo, Tokyo 113-0033, Japan Joseph Henry Laboratories, Princeton University, Princeton, NJ 08544 School of Natural Sciences, Institute for Advanced Study, Einstein Drive, Princeton, NJ 08540 Physics Department, Rochester Institute of Technology, 85 Lomb Memorial Drive, Rochester, NY 14623-5603 Department of Astronomy and Astrophysics, the Pennsylvania State University, University Park, PA 16802 University of Zagreb, Department of Physics, Bijenička cesta 32, 10000 Zagreb, Croatia Institute for Astronomy, 2680 Woodlawn Road, Honolulu, HI 96822 University of Wyoming, Dept. of Physics & Astronomy, Laramie, WY 82071 Department of Physics, Drexel University, Philadelphia, PA 19104 Max-Planck-Institut für extraterrestrische Physik, Giessenbachstrasse 1, D-85741 Garching, Germany Department of Astronomy, Ohio State University, Columbus, OH 43210

Fitting the continuum component of a quasar spectrum in UV/optical band is challenging due to contamination of numerous emission lines. Traditional fitting algorithms such as the least-square fitting and the Levenberg-Marquardt algorithm (LMA) are fast but are sensitive to initial values of fitting parameters. They cannot guarantee to find global optimum solutions when the object functions have multiple minima. In this work, we attempt to fit a typical quasar spectrum using the Covariance Matrix Adaptation Evolution Strategy (CMA-ES). The spectrum is generated by composing a number of real quasar spectra from the Sloan Digital Sky Survey (SDSS) quasar catalog data release 3 (DR3) so it has a higher signal-to-noise ratio. The CMA-ES algorithm is an evolutionary algorithm that is designed to find the global rather than the local minima. The algorithm we implemented achieves an improved fitting result than the LMA and unlike the LMA, it is independent of initial parameter values. We are looking forward to implementing this algorithm to real quasar spectra in UV/optical band.

We present HST-COS spectra of ten quasars located behind M31, selected to investigate the properties of gas associated with its extended disk and high velocity clouds (HVCs). The sightlines have impact parameters ranging between b= 13 kpc and 112 kpc. No absorption is detected in the four sightlines beyond b=57 kpc. Of the six remaining sightlines, all of which lie at b<32 kpc and within the N(HI)= 2E18 cm^{-2} boundary of the HI disk of M31, we detect low-ionization absorption at M31 velocities along four of them (three of which include MgII absorption). We also detect MgII absorption from an HVC. We find that along sightlines where both are detected, the velocity location of the low-ion gas tracks the peak in 21 cm emission. High-ionization absorption is detected along the three inner sightlines, but not along the three outer sightlines, for which CIV data exist. As inferred from 21 cm emission line maps, only one sightline may have a damped Ly-alpha system. This sightline has b= 17.5 kpc, and we detect both low- and high-ion absorption lines associated with it. The impact parameters through M31 are similar to the impact parameters of galaxies identified with MgII absorbers at redshifts 0.1<z<1.0 in a 2011 study by Rao et al. However, the M31 MgII2796 rest equivalent width values are significantly smaller. In comparison, moderate-to-strong MgII absorption from Milky Way gas is detected along all ten sightlines. Thus, this study indicates that M31 does not present itself as an absorbing galaxy which is typical of higher-redshift galaxies inferred to give rise to moderate-strength quasar absorption lines. M31 also appears not to possess an extensive large gaseous cross section, at least not along the direction of its major axis. (Abridged.)

We have studied a sample of 1084 intervening absorption systems with 2.156 zab 65.2, having log(NHI) > 20.0 in the spectra of QSOs in Sloan Digital Sky Survey (SDSS) data release 7 (DR7), with the aim of understanding the nature and abundance of the dust and the chemical abundances in the DLA absorbers. Composite spectra were constructed for the full sample and several subsamples, chosen on the basis of absorber and QSO properties. Average extinction curves were obtained for the samples by comparing their geometric mean composite spectra with those of two samples of QSOs, matching in zem and i magnitude with the DLA sample, one sample without any absorbers along their lines of sight and the other without any DLAs along their lines of sight irrespective of the presence of other absorption systems. We also derived relative extinction curves of several pairs of subsamples. While the average reddening in the DLA sample is small, we find definite e vidence for the presence of dust in subsamples based on absorber properties, in particular the strength of metal absorption lines. DLAs along lines of sight to QSOs which are not colour selected are found to be more dusty compared to those along the lines of sight to the more numerous colour selected QSOs. From these studies and from the strengths of absorption lines in the composite spectra, we conclude that 6 10% of the DLAs in SDSS DR7 cause significant reddening, have stronger absorption lines and have higher abundances as compared to the rest of the sample. The rest of the sample shows little reddening. While due to the dominant color selection method used to target QSOs in the SDSS DR7, this fraction of 10% likely represents a lower limit for the global fraction of dusty DLAs at high-z, it is also possib le that the dust grain sizes at high redshifts are larger, giving rise to a flat extinction cu rve over the observed range of wavelengths.

We have compiled a catalog of optically selected quasars with simultaneous observations in UV/optical and X-ray bands by the Swift Gamma-ray Burst Explorer. Objects in this catalog are identified by matching the Swift pointings with the Sloan Digital Sky Survey Data Release 5 quasar catalog. The final catalog contains 843 objects, among which 637 have both Ultraviolet Optical Telescope (UVOT) and X-Ray Telescope (XRT) observations and 354 of which are detected by both instruments. The overall X-ray detection rate is similar to 60% which rises to similar to 85% among sources with at least 10 ks of XRT exposure time. We construct the time-averaged spectral energy distribution (SED) for each of the 354 quasars using UVOT photometric measurements and XRT spectra. From model fits to these SEDs, we find that the big blue bump contributes about similar to 0.3 dex to the quasar luminosity. We re-visit the alpha(ox)-L-2500 angstrom relation by selecting a clean sample with only Type 1 radio-quiet quasars; the dispersion of this relation is reduced by at least 15% compared with studies that use non-simultaneous UV/optical and X-ray data. We only found a weak correlation between L-bol/L-Edd and alpha(UV). We do not find significant correlations between alpha(x) and alpha(ox), alpha(ox) and alpha(UV), and alpha(x) and log L(0.3-10 keV). The correlations between alpha(UV) and alpha(x), alpha(ox) and alpha(x), alpha(ox) and alpha(UV), L-bol/L-Edd and alpha(x), and L-bol/L-Edd and alpha(ox) are stronger among low-redshift quasars, indicating that these correlations are likely driven by the changes of SED shape with accretion state.

A search for emission lines in foreground galaxies in quasar spectra (zgal < zQSO) of the Sloan Digital Sky Survey data release 5 reveals 23 examples of quasars shining through low redshift, foreground galaxies at small impact parameters (<10 kpc). About 74 000 quasar spectra were examined by searching for narrow Hα emission lines at z < 0.38, at a flux level greater than 5 × 10−17 erg cm−2 s−1, and then confirming that other expected emission lines of the H ii regions in the galaxy are detected. The galaxies were deblended from the quasar images to get colours and morphologies. For cases that allow the galaxy and the quasar to be deblended, the galaxies are blue (0.95 < (u−r) < 1.95). Extinction and reddening through the galaxies are determined from the (g−i) colour excess of the quasars. These reddening values are compared with the flux ratio of Hα to Hβ, which reflect the extinction for an undetermined fraction of the sightline through each galaxy. No trends were found relating E(B−V)(g−i), impact parameter (b), and (u−r) for the galaxies or between E(B−V) derived from (g−i) and that derived from Hα/Hβ. Comparison with previous studies of quasar absorption systems indicates that our sample is more reddened, suggesting disc-dominated absorber galaxies. Measurement or limits on galactic, interstellar Ca ii and Na i absorption lines are given from the quasar spectrum. No trends were found relating the Ca ii equivalent width W (Ca ii) or the Na i equivalent width W (Na i) to b, but a correlation of rs=−0.77 (α= 0.05) was found relating W (Ca ii) and E(B−V)(g−i).

We present ultraviolet (UV) and optical photometry of 26 Type Ia supernovae (SNe Ia) observed from 2005 March to 2008 March with the NASA Swift Ultraviolet and Optical Telescope (UVOT). The dataset consists of 2133 individual observations, making it by far the most complete study of the UV emission from SNe Ia to date. Grouping the SNe into three subclasses as derived from optical observations, we investigate the evolution of the colors of these SNe, finding a high degree of homogeneity within the normal subclass, but dramatic differences between that group and the subluminous and SN 2002cx-like groups. For the normal events, the redder UV filters on UVOT (u, uvw1) show more homogeneity than do the bluer UV filters (uvm2, uvw2). Searching for purely UV characteristics to determine existing optically based groupings, we find the peak width to be a poor discriminant, but we do see a variation in the time delay between peak emission and the late, flat phase of the light curves. The UV light curves peak a few days before the B band for most subclasses (as was previously reported by Jha et al.), although the SN 2002cx-like objects peak at a very early epoch in the UV. That group also features the bluest emission observed among SNe Ia. As the observational campaign is ongoing, we discuss the critical times to observe, as determined by this study, in order to maximize the scientific output of future observations.

At present, the precision of deep ultraviolet photometry is somewhat limited by the dearth of faint ultraviolet standard stars. In an effort to improve this situation, we present a uniform catalog of eleven new faint (u sim17) ultraviolet standard stars. High-precision photometry of these stars has been taken from the Sloan Digital Sky Survey and Galaxy Evolution Explorer and combined with new data from the Swift Ultraviolet Optical Telescope to provide precise photometric measures extending from the Near Infrared to the Far Ultraviolet. These stars were chosen because they are known to be hot (20,000 < T_eff < 50,000 K) DA white dwarfs with published Sloan spectra that should be photometrically stable. This careful selection allows us to compare the combined photometry and Sloan spectroscopy to models of pure hydrogen atmospheres to both constrain the underlying properties of the white dwarfs and test the ability of white dwarf models to predict the photometric measures. We find that the photometry provides good constraint on white dwarf temperatures, which demonstrates the ability of Swift/UVOT to investigate the properties of hot luminous stars. We further find that the models reproduce the photometric measures in all eleven passbands to within their systematic uncertainties. Within the limits of our photometry, we find the standard stars to be photometrically stable. This success indicates that the models can be used to calibrate additional filters to our standard system, permitting easier comparison of photometry from heterogeneous sources. The largest source of uncertainty in the model fitting is the uncertainty in the foreground reddening curve, a problem that is especially acute in the UV.

We examine the absolute magnitudes and light-curve shapes of 14 nearby (redshift z = 0.004–0.027) Type Ia supernovae (SNe Ia) observed in the ultraviolet (UV) with the Swift Ultraviolet/Optical Telescope. Colors and absolute magnitudes are calculated using both a standard Milky Way extinction law and one for the Large Magellanic Cloud that has been modified by circumstellar scattering. We find very different behavior in the near-UV filters (uvw1rc covering ∼2600–3300 Å after removing optical light, and u ≈ 3000–4000 Å) compared to a mid-UV filter (uvm2 ≈2000–2400 Å). The uvw1rc − b colors show a scatter of ∼0.3 mag while uvm2−b scatters by nearly 0.9 mag. Similarly, while the scatter in colors between neighboring filters is small in the optical and somewhat larger in the near-UV, the large scatter in the uvm2 − uvw1 colors implies significantly larger spectral variability below 2600 Å. We find that in the near-UV the absolute magnitudes at peak brightness of normal SNe Ia in our sample are correlated with the optical decay rate with a scatter of 0.4 mag, comparable to that found for the optical in our sample. However, in the mid-UV the scatter is larger, ∼1 mag, possibly indicating differences in metallicity. We find no strong correlation between either the UV light-curve shapes or the UV colors and the UV absolute magnitudes. With larger samples, the UV luminosity might be useful as an additional constraint to help determine distance, extinction, and metallicity in order to improve the utility of SNe Ia as standardized candles.