P. S. Pellegrini

The Galaxy Luminosity Function at z ≤ 0.05: Dependence on Morphology

We investigate the dependence of the local galaxy luminosity function on morphology using 5404 galaxies from the recently enlarged Second Southern Sky Redshift Survey (SSRS2). Over the range -22 ≤ MB ≤ -14 (H0 = 100 km s-1 Mpc-1), the luminosity function of early-type galaxies is well fitted by a Schechter function with parameters M -->*=-19.37 -->−0.11+0.10, α=-1.00 -->−0.09+0.09, and * = 4.4 ± 0.8 × 10-3 Mpc-3. The spiral luminosity function is very similar and is well fitted by the parameters M -->*=-19.43 -->−0.08+0.08, α=-1.11 -->−0.06+0.07, and * = 8.0 ± 1.4 × 10-3 Mpc-3 over the same range in absolute magnitude. The flat faint end of the early-type luminosity function is consistent with earlier measurements from the CfA Redshift Survey (Marzke et al.) but is significantly steeper than the slope measured in the Stromlo-APM survey (Loveday et al.). Combined with the increased normalization of the overall LF measured from intermediate-redshift surveys, the flat faint-end slope of the E/S0 LF produces no-evolution models that reproduce the deep Hubble Space Telescope (HST) counts of early-type galaxies remarkably well. However, the observed normalization of the SSRS2 LF is consistent with the low value measured in other local redshift surveys. The cause of this low-redshift anomaly remains unknown. The luminosity function of irregular and peculiar galaxies in the SSRS2 is very steep: M -->*=-19.78 -->−0.50+0.40, α=-1.81 -->−0.24+0.24, and * = 0.2 ± 0.08 × 10-3 Mpc-3. The steep slope at the faint end is consistent with the LFs measured for Sm-Im galaxies in the CfA survey, UV-selected galaxies (Treyer et al.), star-forming field galaxies (Bromley et al.), and the bluest galaxies in the SSRS2 (Marzke & da Costa). As shown by Driver, Windhorst, & Griffiths, the steep LF reduces the observed excess of faint irregulars over no-evolution predictions but cannot explain it entirely.

New Techniques for Relating Dynamically Close Galaxy Pairs to Merger and Accretion Rates: Application to the Second Southern Sky Redshift Survey

The galaxy merger and accretion rates, and their evolution with time, provide important tests for models of galaxy formation and evolution. Close pairs of galaxies are the best available means of measuring redshift evolution in these quantities. In this study, we introduce two new pair statistics, which relate close pairs to the merger and accretion rates. We demonstrate the importance of correcting these (and other) pair statistics for selection effects related to sample depth and completeness. In particular, we highlight the severe bias that can result from the use of a flux-limited survey. The first statistic, Nc, gives the number of companions per galaxy within a specified range in absolute magnitude. Nc is directly related to the galaxy merger rate. The second statistic, Lc, gives the total luminosity in companions, per galaxy. This quantity can be used to investigate the mass accretion rate. Both Nc and Lc are related to the galaxy correlation function ξ and luminosity function (M) in a straightforward manner. Both statistics have been designed with selection effects in mind. We outline techniques that account for various selection effects and demonstrate the success of this approach using Monte Carlo simulations. If one assumes that clustering is independent of luminosity (which is appropriate for reasonable ranges in luminosity), then these statistics may be applied to flux-limited surveys. These techniques are applied to a sample of 5426 galaxies in the Second Southern Sky Redshift Survey (SSRS2). This is the first large, well-defined low-z survey to be used for pair statistics. Using close (5 h-1 kpc ≤ rp ≤ 20 h-1 kpc) dynamical (Δv ≤ 500 km s-1) pairs, we find Nc(-21 ≤ MB ≤ -18) = 0.0226 ± 0.0052 and Lc(-21 ≤ MB ≤ -18) = 0.0216 ± 0.0055 × 1010 h2 L☉ at z = 0.015. These are the first secure estimates of low-redshift pair statistics, and they will provide local benchmarks for ongoing and future pair studies. If Nc remains fixed with redshift, simple assumptions imply that ~6.6% of present day galaxies with -21 ≤ MB ≤ -18 have undergone mergers since z = 1. When applied to redshift surveys of more distant galaxies, these techniques will yield the first robust estimates of evolution in the galaxy merger and accretion rates.

Cluster versus Field Elliptical Galaxies and Clues on Their Formation

Using new observations for a sample of 931 early-type galaxies, we investigate whether the Mg2-σ0 relation shows any dependence on the local environment. The galaxies have been assigned to three different environments depending on the local overdensity (clusters, groups, and field); we used our complete redshift database to guide the assignment of galaxies. It is found that cluster, group, and field early-type galaxies follow almost identical Mg2-σ0 relations, with the largest Mg2 zero-point difference (clusters minus field) being only 0.007±0.002 mag. No correlation of the residuals is found with the morphological type or the bulge-to-disk ratio. Using stellar population models in a differential fashion, this small zero-point difference implies a luminosity-weighted age difference of only ~1 Gyr between the corresponding stellar populations, with field galaxies being younger. The mass-weighted age difference could be significantly smaller if minor events of late star formation took place preferentially in field galaxies. We combine these results with the existing evidence for the bulk of stars in cluster early-type galaxies having formed at very high redshift and conclude that the bulk of stars in galactic spheroids had to form at high redshifts (z3), no matter whether such spheroids now reside in low- or high-density regions. The cosmological implications of these findings are briefly discussed.

Southern sky redshift survey: clustering of local galaxies

We use the two-point correlation function to calculate the clustering properties of the recently completed SSRS2 survey, which probes two well-separated regions of the sky, allowing one to evaluate the sensitivity of sample-to-sample variations. Taking advantage of the large number of galaxies in the combined sample, we also investigate the dependence of clustering on the internal properties of galaxies. The redshift-space correlation function for the combined magnitude-limited sample of the SSRS2 is given by ?(s) = [s/(5.85 h-1 Mpc)]-1.60 for separations in the range 2 h-1 Mpc ? s ? 11 h-1 Mpc, while our best estimate for the real-space correlation function is ?(r) = [r/(5.36 h-1 Mpc)]-1.86. Both are comparable with previous measurements using surveys of optical galaxies over much larger and independent volumes. By comparing the correlation function calculated in redshift and real space, we find that the redshift distortion on intermediate scales is small. This result implies that the observed redshift-space distribution of galaxies is close to that in real space and that ? = ?0.6/b L*) are more clustered than sub-L* galaxies and that the luminosity segregation is scale-independent. We also find that early types are more clustered than late types. However, in the absence of rich clusters, the relative bias between early and late types in real space, bE+S0/bS ~ 1.2, is not as strong as previously estimated. Furthermore, both morphologies present a luminosity-dependent bias, with the early types showing a slightly stronger dependence on luminosity. We also find that red galaxies are significantly more clustered than blue ones, with a mean relative bias of bR/bB ~ 1.4, stronger than that observed for morphology. Finally, by comparing our results with the measurements obtained from the infrared-selected galaxies, we determine that the relative bias between optical and IRAS galaxies in real space is bo/bI ~ 1.4.

The southern sky redshift survey

The general characteristics of the space distribution of galaxies in the SSRS sample, covering the southern Galactic cap, are examined, and maps of the space distribution are presented. The sample consists of 2028 galaxies in an area of 1.75 sr with declination south of -17.5 deg and galactic latitude below -30 deg. The survey provides useful information on large-scale structure to a depth of 120/h Mpc. The galaxy distribution exhibits prominent filaments, sheets, and voids. Some large-scale structures are highly subclustered; others are much more diffuse. 21 references.

Photometric redshift analysis in the Dark Energy Survey science verification data

We present results from a study of the photometric redshift performance of the Dark Energy Survey (DES), using the early data from a Science Verification (SV) period of observations in late 2012 and early 2013 that provided science-quality images for almost 200 sq.~deg.~at the nominal depth of the survey. We assess the photometric redshift performance using about 15000 galaxies with spectroscopic redshifts available from other surveys. These galaxies are used, in different configurations, as a calibration sample, and photo-

Redshift-Distance Survey of Early-Type Galaxies: Spectroscopic Data

z

Southern sky redshift survey : the catalog

s are obtained and studied using most of the existing photo-

Redshift-Distance Survey of Early-Type Galaxies. I. Sample Selection, Properties, and Completeness*

z

The morphological catalogue of galaxies equatorial survey

codes. A weighting method in a multi-dimensional color-magnitude space is applied to the spectroscopic sample in order to evaluate the photo-