Improved Background Subtraction for the Sloan Digital Sky Survey Images

Blanton, Michael R.; Kazin, Eyal; Muna, Demitri; Weaver, B. A.; Price-Whelan, Adrian M.

doi:10.1088/0004-6256/142/1/31

Cited by 551 publications

(552 citation statements)

References 28 publications

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“…The photometric catalogue of detected objects was used to identify the targets for spectroscopy: a) the main galaxy sample (Strauss et al 2002), with a target magnitude limit of m r,Petrosian < 17.77 mag corrected for Galactic dust extinction; and b) the Baryon Oscillation Spectroscopic Survey (BOSS; Dawson et al 2013), which uses a new spectrograph (Smee et al 2013) to obtain spectra of galaxies with 0.15 < z < 0.8 and quasars with 2.15 < z < 3.5, which is useful to reject background objects in our study. The data are processed using automatic pipelines (Blanton et al 2011). …”

Section: Methodsmentioning

confidence: 99%

The AMIGA sample of isolated galaxies

Argudo-Fernández

Verley

Bergond

et al. 2013

A&A

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Context. To understand the evolution of galaxies, it is necessary to have a reference sample where the effect of the environment is minimized and quantified. In the framework of the AMIGA project (Analysis of the interstellar Medium of Isolated GAlaxies), we present a revision of the environment for galaxies in the Catalogue of Isolated Galaxies (CIG, Karachentseva 1973, Astrof. Issledovaniia Byu. Spec. Ast. Obs., 8, 3) using the ninth data release of the Sloan Digital Sky Survey (SDSS-DR9). Aims. The aims of this study are to refine the photometric-based AMIGA sample of isolated galaxies and to provide an improvement of the quantification of the isolation degree with respect to previous works, using both photometry and spectroscopy. Methods. We developed an automatic method to search for neighbours within a projected area of 1 Mpc radius centred on each primary galaxy to revise the CIG isolation criteria introduced by Karachentseva (1973). The local number density at the fifth nearest neighbour and the tidal strength affecting the CIG galaxy were estimated to quantify the isolation degree. Results. Of the 636 CIG galaxies considered in the photometric study, 426 galaxies fulfil the CIG isolation criteria within 1 Mpc, taking into account projected neighbours. Of the 411 CIG galaxies considered in the spectroscopic study, 347 galaxies fulfil the CIG isolation criteria when a criterion about redshift difference is added. The available redshifts allow us to reject background neighbours and thus improve the photometric assessment. On average, galaxies in the AMIGA sample show lower values in the local number density and the tidal strength parameters than galaxies in denser environments such as pairs, triplets, compact groups, and clusters. Conclusions. For the first time, the environment and the isolation degree of AMIGA galaxies are quantified using digital data. The use of the SDSS database permits one to identify fainter and smaller-size satellites than in previous AMIGA works. The AMIGA sample is improved by this study, because we reduced the sample of isolated galaxies used in previous AMIGA works by about 20%. The availability of the spectroscopic data allows us to check the validity of the CIG isolation criteria, which is not fully efficient. About 50% of the neighbours considered as potential companions in the photometric study are in fact background objects. We also find that about 92% of the neighbour galaxies that show recession velocities similar to the corresponding CIG galaxy are not considered by the CIG isolation criteria as potential companions, which may have a considerable influence on the evolution of the central CIG galaxy.

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Section: Methodsmentioning

confidence: 99%

The AMIGA sample of isolated galaxies

Argudo-Fernández

Verley

Bergond

et al. 2013

A&A

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“…To facilitate a detailed investigation of how the observed CGM absorption properties depend on galaxy properties, we also made use of available measurements of rest-frame UV luminosities and stellar mass from the NASA-Sloan At- las 2 (Blanton et al 2005;Blanton et al 2011). This public atlas contains 145,155 galaxies with known redshifts at z < ∼ 0.05.…”

Section: A Public Sample Of Galaxy-qso Pairsmentioning

confidence: 99%

“…This public atlas contains 145,155 galaxies with known redshifts at z < ∼ 0.05. For each galaxy, it includes optical and UV photometric measurements from the SDSS Data Release 8 (Blanton et al 2011) and GALEX Data Release 6 (Schiminovich et al 2007), as well as derived quantities such as stellar mass (Mstar) and rest-frame UV and optical absolute magnitudes computed by the K-correct code (Blanton & Roweis 2007). The rest-frame UV absolute magnitudes allows us to estimate an unobscured star formation rate (SFR) for each galaxy based on the calibration coefficient of Kennicutt & Evans (2012).…”

Section: A Public Sample Of Galaxy-qso Pairsmentioning

confidence: 99%

Mining circumgalactic baryons in the low-redshift universe

Liang

Chen

2014

Monthly Notices of the Royal Astronomical Society

142

229

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This paper presents an absorption-line study of the multiphase circumgalactic medium (CGM) based on observations of Lyα, C II, C IV, Si II, Si III, and Si IV absorption transitions in the vicinities of 195 galaxies at redshift z < 0.176. The galaxy sample is established based on a cross-comparison between public galaxy and QSO survey data and is characterized by a median redshift of z = 0.041, a median projected distance of d = 362 kpc to the sightline of the background QSO, and a median stellar mass of log (M star /M ) = 9.7 ± 1.1. Comparing the absorber features identified in the QSO spectra with known galaxy properties has led to strong constraints for the CGM absorption properties at z < ∼ 0.176. First, abundant hydrogen gas is observed out to d ∼ 500 kpc, well beyond the dark matter halo radius R h of individual galaxies, with a mean covering fraction of ≈ 60%. In contrast, no heavy elements are detected at d > ∼ 0.7 R h from either low-mass dwarfs or high-mass galaxies. The lack of detected heavy elements in low-and high-ionization states suggests that either there exists a chemical enrichment edge at d ≈ 0.7 R h or gaseous clumps giving rise to the observed absorption lines cannot survive at these large distances. Considering all galaxies at d > R h leads to a strict upper limit for the covering fraction of heavy elements of ≈ 3% (at a 95% confidence level) over d = (1 − 9) R h . At d < R h , differential covering fraction between low-and high-ionization gas is observed, suggesting that the CGM becomes progressively more ionized from d < 0.3 R h to larger distances. Comparing CGM absorption observations at low and high redshifts shows that at a fixed-fraction of R h the CGM exhibits stronger mean absorption at z = 2.2 than at z ∼ 0 and that the distinction is most pronounced in low-ionization species traced by C II and Si II absorption lines. We discuss possible pseudo-evolution of the CGM as a result of misrepresentation of halo radius, and present a brief discussion on the implications of these findings.

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“…Besides this, the modeled light of the BGGs was subtracted from the original images, and the magnitudes of all other galaxies were obtained by running SExtractor in the resulting images. SDSS photometry suffers from both deblending and overestimation of sky levels near bright galaxies (Blanton et al 2011). …”

Section: Fossilness Determinationmentioning

confidence: 99%

Fossil group origins

Zarattini¹,

Barrena²,

Girardi³

et al. 2014

A&A

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Context. Virialized halos grow by the accretion of smaller ones in the cold dark matter scenario. The rate of accretion depends on the different properties of the host halo. Those halos for which this accretion rate was very fast and efficient resulted in systems dominated by a central galaxy surrounded by smaller galaxies that were at least two magnitudes fainter. These galaxy systems are called fossil systems, and they can be the fossil relics of ancient galaxy structures. Aims. We started an extensive observational program to characterize a sample of 34 fossil group candidates spanning a broad range of physical properties. Methods. Deep r-band images were obtained with the 2.5-m Isaac Newton Telescope and Nordic Optic Telescope. Optical spectroscopic observations were performed at the 3.5-m Telescopio Nazionale Galileo for ∼1200 galaxies. This new dataset was completed with Sloan Digital Sky Survey Data Release 7 archival data to obtain robust cluster membership and global properties of each fossil group candidate. For each system, we recomputed the magnitude gaps between the two brightest galaxies (Δm 12 ) and the first and fourth ranked galaxies (Δm 14 ) within 0.5 R 200 . We consider fossil systems to be those with Δm 12 ≥ 2 mag or Δm 14 ≥ 2.5 mag within the errors. Results. We find that 15 candidates turned out to be fossil systems. Their observational properties agree with those of non-fossil systems. Both follow the same correlations, but the fossil systems are always extreme cases. In particular, they host the brightest central galaxies, and the fraction of total galaxy light enclosed in the brightest group galaxy is larger in fossil than in non-fossil systems. Finally, we confirm the existence of genuine fossil clusters. Conclusions. Combining our results with others in the literature, we favor the merging scenario in which fossil systems formed from mergers of L * galaxies. The large magnitude gap is a consequence of the extreme merger ratio within fossil systems and therefore it is an evolutionary effect. Moreover, we suggest that at least one fossil group candidate in our sample could represent a transitional fossil stage. This system could have been a fossil in the past, but not now owing to the recent accretion of another group of galaxies.

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Improved Background Subtraction for the Sloan Digital Sky Survey Images

Cited by 551 publications

References 28 publications

The AMIGA sample of isolated galaxies

The AMIGA sample of isolated galaxies

Mining circumgalactic baryons in the low-redshift universe

Fossil group origins

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