Intrinsic brightness of SDSS objects is similar at all redshifts in de Sitter space

SDSS surface photometry of M 31 with absorption corrections

The objective of this work is to obtain an extinction-corrected distribution of optical surface brightness and colour indices of the large nearby galaxy M 31 using homogeneous observational data and a model for intrinsic extinction. We process the Sloan Digital Sky Survey (SDSS) images in ugriz passbands and construct corresponding mosaic images, taking special care of subtracting the varying sky background. We apply the galactic model developed in Tempel et al. (2010) and far-infrared imaging to correct the photometry for intrinsic dust effects. We obtain observed and dust-corrected distribut…

A unified picture of breaks and truncations in spiral galaxies from SDSS and S^{4}G imaging

The mechanism causing breaks in the radial surface brightness distribution of spiral galaxies is not yet well known. Despite theoretical efforts, there is not a unique explanation for these features and the observational results are not conclusive. In an attempt to address this problem, we have selected a sample of 34 highly inclined spiral galaxies present both in the Sloan Digital Sky Survey and in the Spitzer Survey of Stellar Structure in Galaxies. We have measured the surface brightness profiles in the five Sloan optical bands and in the 3.6$μm$ Spitzer band. We have also calculated the c…

Selection Effects in the SDSS Quasar Sample: The Filter Gap Footprint

In the Sloan Digital Sky Survey (SDSS) quasars are targeted using colors and anything that can cause the identifying characteristics of the colors to disappear can create problems in the source selection process. Quasar spectra contain strong emission lines that can seriously affect the colors in photometric systems in which the transmission characteristics vary abruptly and significantly with redshift. When a strong line crosses a gap between two filter passbands the color effects induced by the line change abruptly, and there is also a dimming in apparent brightness compared to those redshif…

Large-scale clustering of Lyman-alpha emission intensity from SDSS/BOSS

(Abridged) We detect the large-scale structure of Lya emission in the Universe at redshifts z=2-3.5 by measuring the cross-correlation of Lya surface brightness with quasars in SDSS/BOSS. We use a million spectra targeting Luminous Red Galaxies at z<0.8, after subtracting a best fit model galaxy spectrum from each one, as an estimate of the high-redshift Lya surface brightness. The quasar-Lya emission cross-correlation we detect has a shape consistent with a LambdaCDM model with Omega_M =0.30^+0.10-0.07. The predicted amplitude of this cross-correlation is proportional to the product of the me…

Subaru Spectroscopy of SDSS-II Supernovae

The Sloan Digital Sky Survey II (SDSS-II) Supernova Survey discovered Type Ia supernovae (SNe Ia) in an almost unexplored intermediate redshift range of $0.05 < z < 0.4$ and provided densely sampled multi-color light curves for SN candidates. Followup spectroscopy of this survey was carried out with the Subaru telescope and spectra of 71 SN Ia candidates were obtained. One spectrum was observed per candidate except for a peculiar variable. This paper presents the method for processing these spectra. The observed wavelength ranges of our spectra are 4000 to 9000 Å for Year 2005 and 3600 to 9000…

Assessing Cosmic Acceleration with the Alcock-Paczynski Effect in the SDSS-IV Quasar Catalog

The geometry of the Universe may be probed using the Alcock-Paczynski (AP) effect, in which the observed redshift size of a spherical distribution of sources relative to its angular size varies according to the assumed cosmological model. Past applications of this effect have been limited, however, by a paucity of suitable sources and mitigating astrophysical factors, such as internal redshift-space distortions and poorly known source evolution. In this Letter, we introduce a new test based on the AP effect that avoids the use of spatially bound systems, relying instead on sub-samples of quasa…

Revisiting the low-luminosity galaxy population of the NGC 5846 group with SDSS

Low-luminosity galaxies are known to outnumber the bright galaxy population in poor groups and clusters of galaxies. Yet, the investigation of low-luminosity galaxy populations outside the Local Group remains rare and the dependence on different group environments is still poorly understood. Previous investigations revealed photometric scaling relations for early-type dwarfs and a strong dependence of morphology with environment. The present study aims to analyse the photometric and spectroscopic properties of the low-luminosity galaxy population in the nearby, well-evolved and early-type domi…

Colour gradients within SDSS DR7 galaxies: hints of recent evolution

The evolutionary path followed by a galaxy shapes its internal structure, and, in particular, its internal colour variation. We present a study of the internal colour variation within galaxies from the Seventh Data Release of the Sloan Digital Sky Survey (SDSS DR7). We statistically study the connection between the internal colour variation and global galactic properties, looking for hints of the recent galactic evolution. Considering only galaxies with good photometry and spectral measurements, we define four luminosity-threshold samples within the redshift range 0.01<z<0.17, each containing …

Searching for Dust Reddening in SDSS Spectra with Damped Lyman $α${} Systems

We searched for evidence of reddening of background SDSS QSO spectra due to dust in intervening DLA systems. We utilise the Data Releases 5 and 7 to arrive at sample sizes of 475 (DR5) and 676 (DR7) absorbers, based on two different published lists of SDSS DLAs. Both samples span roughly the redshift range of 2.2 < z_abs < 5.2, with a mean of z~3.0, and the majority of the DLAs (75%) below z=3.3. We construct geometric mean spectra in the absorber restframes ranging from 1240 to ~2800 A, and composite spectra of samples matching the 'DLA' QSOs in i band magnitude and emission redshift z_em, bu…

The Faint End of the Luminosity Function and Low Surface Brightness Galaxies

SHELS (Smithsonian Hectospec Lensing Survey) is a dense redshift survey covering a 4 square degree region to a limiting R = 20.6. In the construction of the galaxy catalog and in the acquisition of spectroscopic targets, we paid careful attention to the survey completeness for lower surface brightness dwarf galaxies. Thus, although the survey covers a small area, it is a robust basis for computation of the slope of the faint end of the galaxy luminosity function to a limiting M_R = -13.3 + 5logh. We calculate the faint end slope in the R-band for the subset of SHELS galaxies with redshif ts in…

Photometric properties of intermediate redshift Type Ia Supernovae observed by SDSS-II Supernova Survey

We have analyzed multi-band light curves of 328 intermediate redshift (0.05 <= z < 0.24) type Ia supernovae (SNe Ia) observed by the Sloan Digital Sky Survey-II Supernova Survey (SDSS-II SN Survey). The multi-band light curves were parameterized by using the Multi-band Stretch Method, which can simply parameterize light curve shapes and peak brightness without dust extinction models. We found that most of the SNe Ia which appeared in red host galaxies (u - r > 2.5) don't have a broad light curve width and the SNe Ia which appeared in blue host galaxies (u - r < 2.0) have a variety of light cur…

Discovery of Nine Intermediate Redshift Compact Quiescent Galaxies in the Sloan Digital Sky Survey

We identify nine galaxies with dynamical masses of M_dyn>10^10 M_sol as photometric point sources, but with redshifts between z=0.2 and z=0.6, in the Sloan Digital Sky Survey (SDSS) spectro-photometric database. All nine galaxies have archival Hubble Space Telescope (HST) images. Surface brightness profile fitting confirms that all nine galaxies are extremely compact (with circularized half-light radii between 0.4 and 6.6 kpc and the median value of 0.74 kpc) for their velocity dispersion (110<sigma<340 km/s; median sigma=178 km/s). From the SDSS spectra, three systems are dominated by very yo…

The Color Variability of Quasars

We quantify quasar color-variability using an unprecedented variability database - ugriz photometry of 9093 quasars from SDSS Stripe 82, observed over 8 years at ~60 epochs each. We confirm previous reports that quasars become bluer when brightening. We find a redshift dependence of this blueing in a given set of bands (e.g. g and r), but show that it is the result of the flux contribution from less-variable or delayed emission lines in the different SDSS bands at different redshifts. After correcting for this effect, quasar color-variability is remarkably uniform, and independent not only of …

基于Copula Entropy的测光红移

Photometric Redshifts with Copula Entropy

本文提出利用Copula Entropy（CE）测量测光数据与红移的相关性以筛选特征，在SDSS quasar数据上验证表明该方法提升了测光红移精度且模型具可解释性。