We have used the Parkes Multibeam system and the Sloan Digital Sky Survey (SDSS) to assemble a sample of 195 galaxies selected originally from their HI signature to avoid biases against unevolved or low surface brightness objects. For each source 9 intrinsic properties are measured homogeneously, as well as inclination and an optical spectrum. The sample, which should be almost entirely free of either misidentification or confusion, includes a wide diversity of galaxies ranging from inchoate, low surface brightness dwarfs to giant spirals. Despite this diversity there are 5 clear correlations among their properties. They include a common dynamical mass-to-light ratio within their optical radii, a correlation between surface-brightness and Luminosity and a common HI surface-density. Such correlation should provide strong constrains on models of galaxy formation and evolution.
We have constructed a Main galaxy subsample with redshifts in the range 0.08<=z<=0.12 from SDSS Data Release 3 (SDSS DR3), and refer to this subsample as "MGSU"(It contains 67777 galaxies). By cluster analysis, two isolated Main galaxy samples are extracted from this subsample. It turns out that two isolated Main galaxy samples identified at different radii have the same properties. Additionally, we also find that early-type galaxies in isolated Main galaxy samples are fewer than that in close double galaxy sample.
We present here the VO access to the results of an analysis of the spectra of Sloan Digital Sky Survey (SDSS) galaxies performed with the STARLIGHT code by Cid Fernandes et al. (2005). The results include for each galaxy the original SDSS spectrum, the best-fit synthetic spectrum, the star formation history, the pure emission line spectrum corrected from underlying stellar population (in SDSS emission line galaxies) and the intensity of several emission/absorption lines. The database will be accessible from the PGos3 at the end of summer 2007.
We calculate the oxygen abundances for ~45,000 star-forming galaxies selected from the SDSS using nine popular `strong-line' metallicity diagnostics. We find that individual galaxies can have metallicities which differ by factors of up to ~4, depending on the choice of abundance diagnostic. The resulting mass-metallicity relations subsequently exhibit significant offsets, with a range of 0.5 dex in metallicity at a given mass. This demonstrates that different metallicity diagnostics should not be used interchangeably for determining oxygen abundances. We also show that SDSS spectra are dominat…
Based on the catalog of merging galaxies in the Early Data Release (EDR) of the Sloan Digital Sky Survey (SDSS), the differences of star formation history between merging galaxies and field galaxies are studied statistically by means of three spectroscopic indicators the 4000-Å break strength, the Balmer absorption-line index, and the specific star formation rate. It is found that for early-type merging galaxies the interactions will not induce significant enhancement of the star-formation activity because of its stability and lack of cool gas. On the other hand, late-type merging galaxies alw…
We present a new catalog of isolated galaxies obtained through an automated systematic search. These 2980 isolated galaxies were found in approximately 2099 sq deg of sky in the Sloan Digital Sky Survey Data Release 1 (SDSS DR1) photometry. The selection algorithm, implementing a variation on the criteria developed by Karachentseva in 1973, proved to be very efficient and fast. This catalog will be useful for studies of the general galaxy characteristics. Here we report on our results.
Using a volume-limited sample of Main Galaxies from the SDSS Data Release 5, we investigate the dependence of galaxy properties on local environment. For each galaxy, the local three-dimensional density is calculated. We find that galaxy morphologies strongly depend on local environment: galaxies in dense environments have predominantly early type morphologies, but other galaxy properties do not present significant dependence on local environment. Clearly, this puts a important constraint on proposed physical mechanisms.
The apparatus of correlation gamma function (Γ*(r)) is used to analyze volume-limited samples from the DR4 Main Galaxy Sample of the SDSS survey with the aim of determining the characteristic scales of galaxy clustering. Up to 20 h^{-1} Mpc (H_0 = 65 km s^{-1}Mpc^{-1}), the distribution of galaxies is described by a power-law density-distance dependence, Γ*(r) proportional to r^{-γ}, with an index γapproximately 1.0. A change in the state of clustering (a significant deviation from the power law) was found on a scale of 20-25 h^{-1}Mpc. The distribution of SDSS galaxies becomes homogeneous (γa…
We have cross-correlated X-ray catalogs derived from archival Chandra ACIS observations with a Sloan Digital Sky Survey (SDSS) Data Release 2 (DR2) galaxy catalog to form a sample of 42 serendipitously X-ray detected galaxies over the redshift interval 0.03 < z < 0.25. This pilot study will help fill in the "redshift gap" between local X-ray-studied samples of normal galaxies and those in the deepest X-ray surveys. Our chief purpose is to compare optical spectroscopic diagnostics of activity (both star-formation and accretion) with X-ray properties of galaxies. Our work supports a normalizatio…
We present a new catalog of merging galaxies obtained through an automated systematic search routine. The 1479 new pairs of merging galaxies were found in approximately 462 sq deg of the Sloan Digital Sky Survey Early Data Release (SDSS EDR; Stoughton et al. 2002) photometric data, and the pair catalog is complete for galaxies in the magnitude range 16.0 <= g* <= 20. The selection algorithm, implementing a variation on the original Karachentsev (1972) criteria, proved to be very efficient and fast. Merging galaxies were selected such that the inter-galaxy separations were less than the sum of …
We present a study of the connection between star-forming galaxies, AGN host galaxies, and normal early-type galaxies in the Sloan Digital Sky Survey (SDSS). Using the SDSS DR5 and DR4plus data, we select our early-type galaxy sample in the color versus color-gradient space, and we classify the spectral types of the selected early-type galaxies into normal, star-forming, Seyfert, and LINER classes, using several spectral line flux ratios. We investigate the slope in the fundamental space for each class of early-type galaxies and find that there are obvious differences in the slopes of the fund…
The distribution of satellite galaxies relative to isolated host galaxies in the Sloan Digital Sky Survey (SDSS) is investigated. Host-satellite systems are selected using three different methods, yielding samples of ~3300, ~1600, and \~950 satellites. In the plane of the sky, the distributions of all three samples show highly significant deviations from circular symmetry (> 99.99%, > 99.99%, and 99.79% confidence levels, respectively), and the degree of anisotropy is a strong function of the projected radius, r_p, at which the satellites are found. For r_p < 100 kpc, the SDSS satellites are a…
We discuss the serendipitous discovery of an extremely metal poor galaxy, SDSS 0809+1729, classified as a star in the Sloan Digital Sky Survey (SDSS). The galaxy has a redshift z = 0.0441 and a B-band absolute magnitude M_B = -17.1. With a metallicity of log(O/H)+12~7.44 or ~1/20 solar, this galaxy is among the 10 most metal poor emission-line galaxies known. SDSS 0809+1729 is a blue compact galaxy (BCG) with a stellar age of ~4.5 Myr, a star formation rate of 0.18 Msun/yr, and a large gas-phase electron density ~367/cm^3. Similar values of these parameters are common among other extremely met…
The current view of galaxy formation holds that all massive galaxies harbor a massive black hole at their center, but that these black holes are not always in an actively accreting phase. X-ray emission is often used to identify accreting sources, but for galaxies that are not harboring quasars (low-luminosity active galaxies), the X-ray flux may be weak, or obscured by dust. To aid in the understanding of weakly accreting black holes in the local universe, a large sample of galaxies with X-ray detections is needed. We cross-match the ROSAT All Sky Survey (RASS) with galaxies from the Sloan Di…
We select ~20000 metal-rich star-forming galaxies from the SDSS-DR2 to study the R23-P method suggested by Pilyugin et al. for metallicity estimates. The oxygen abundances derived from their revised R23-P method are ~0.19 dex lower than those derived from the previous one, and ~0.60 dex lower than the Bayesian abundances obtained by the MPA/JHU group. These abundance discrepancies strongly correlate with the P parameter and weakly depend on the log(R23) parameter.
We analyze the behaviors of reddening vectors in the SDSS photometric system for galaxies of different morphologies, ages, and redshifts. As seen in other photometric systems, the dependence of reddening on the spectral energy distribution (SED) and the nonlinearity of reddening are likewise non-negligible for the SDSS system if extinction is significant (~> 1 mag). These behaviors are most significant for the g filter, which has the largest bandwidth-to-central wavelength ratio among SDSS filters. The SDSS colors involving adjacent filters show greater SED-dependence and nonlinearity. A proce…
We analyse a subsample of the galaxy groups obtained by Merchán & Zandivarez (2005) from the SDSS DR3 to study the fundamental plane and the mass to light ratio of galaxy groups. We find a fundamental plane given by $L_R \propto R^{1.3} σ^{0.7}$. We do not find differences when different dynamical sates or redshift ranges are analysed. We find that the mass to light ratio increases with group mass as $M/L_R \propto M^{0.36}$.
Noisy distance estimates associated with photometric rather than spectroscopic redshifts lead to a mis-estimate of the luminosities, and produce a correlated mis-estimate of the sizes. We consider a sample of early-type galaxies from the SDSS DR6 and apply the generalization of the V_max method to correct for these biases. We show that our technique recovers the true redshift, magnitude and size distributions, as well as the true size-luminosity relation. Regardless the specific application outlined here, our method impacts a broader range of studies, when at least one distance-dependent quant…
Published galaxy power spectra from the 2dFGRS and SDSS are not in good agreement. We revisit this issue by analyzing both the 2dFGRS and SDSS DR5 catalogues using essentially identical technqiues. We confirm that the 2dFGRS exhibits relatively more large scale power than the SDSS, or, equivalently, SDSS has more small scale power. We demonstrate that this difference is due the r-band selected SDSS catalogue being dominated by more strongly clustered red galaxies, due to these galaxies having a stronger scale dependent bias. The power spectra of galaxies of the same rest frame colours from the…
As a test of general relativity on cosmological scales, we measure the γparameter for the growth rate of density perturbations using the redshift-space distortion of the luminous red galaxies in the Sloan Digital Sky Survey (SDSS). Assuming the cosmological constant model, which matches the results of the WMAP experiment, we find γ=0.62+1.8(σ_8-0.8) \pm 0.11 at 1-sigma confidence level, which is consistent with the prediction of general relativity, γ\simeq0.55\sim0.56. Rather high value of σ_8(\geq0.87) is required to be consistent with the prediction of the cosmological DGP model, γ\simeq0.68…
I review here past and present research on clusters and groups of galaxies within the Sloan Digital Sky Survey (SDSS). In particular, I discuss the C4 algorithm which is designed to search for clusters within a 7-dimensional data-space, i.e., simultaneous in both color & space. The C4 catalog has a well defined selection function based on mock SDSS galaxy catalogs constructed from the Hubble Volume simulation, and is >90% complete, with <10% contamination, for halos with M200 > 10^14 Msolar at z<0.14. Furthermore, the observed summed r-band luminosity of C4 clusters is linearly related to M200…
By providing homogeneous photometric and spectroscopic data of high quality for very large and objectively selected samples of galaxies, the Sloan Digital Sky Survey allows statistical studies of the physical properties of galaxies and AGN to be carried out at an unprecedented level of precision and detail. Here we publicly release catalogues of derived physical properties for 211,894 galaxies, including 33,589 narrow-line AGN. These are complete samples with well understood selection criteria drawn from the normal galaxy spectroscopic sample in the second SDSS public data release (DR2). We li…
We present a comprehensive study of the nature of the SDSS galaxies divided into various classes based on their morphology, colour, and spectral features. The SDSS galaxies are classified into early-type and late-type; red and blue; passive, HII, Seyfert, and LINER, returning a total of 16 fine classes of galaxies. We examine the luminosity dependence of seven physical parameters of galaxies in each class. We find that more than half of red early-type galaxies (REGs) have star formation or AGN activity, and that these active REGs have smaller axis ratio and bluer outside compared to the passiv…
Evolution of galaxies through cosmic time has been widely studied at high redshift, but there are a few studies in this field at lower redshifts. However, low-redshifts studies will provide important clues to the evolution of galaxies, furnishing the required link between local and high-redshift universe. In this work we focus on the metallicity of the gas in spiral galaxies at low redshift looking for signs of chemical evolution. We analyze the metallicity contents of star forming galaxies of similar luminosities at different redshifts, we studied the metallicity of star forming galaxies from…
Galaxies are seen from different viewing angles and their observed properties change as a function of viewing angle. In many circumstances we would rather know the intrinsic properties of galaxies - those properties that do not depend on viewing angle. For a large sample of galaxies it is possible to recover the intrinsic properties of galaxies, statistically, by looking for correlations with galaxy inclination, and then applying a correction to remove those dependencies. Studying the intrinsic properties of galaxies can give a different impression of the galaxy population and help avoid the m…
We improve strong lensing constraints on cosmological parameters in light of the new measurement of the velocity dispersion function of early-type galaxies based on the SDSS DR5 data and recent semi-analytical modeling of galaxy formation. Using both the number statistics of the CLASS statistical sample and the image separation distribution of the CLASS and the PANELS radio-selected lenses, we find the cosmological matter density $\Om = 0.25^{+0.12}_{-0.08}$ (68% CL) assuming evolutions of galaxies predicted by a semi-analytical model of galaxy formation and $\Om = 0.26^{+0.12}_{-0.08}$ assumi…
NIBLES is a Key Project proposed for the 100m-class Nancay Radio Telescope (NRT) in France. Its aim is a census of the HI gas content and dynamics of 4,000 Sloan Digital Sky Survey galaxies in the Local Volume (900<cz<12,000 km/s). The galaxies were selected based on their total stellar mass (absolute z-band magnitude Mz), and are distributed evenly over the entire range of Mz covered by local SDSS galaxies (-10 to -24 mag, for H0=70 km/s/Mpc). A pilot survey is being made of over 600 galaxies. NIBLES will be complementary to the ALFALFA and EBHIS blind HI surveys, which will detect a differen…
We present a statistical analysis of halo emission for a sample of 1047 edge-on disk galaxies imaged in five bands by the Sloan Digital Sky Survey (SDSS). Stacking the homogeneously rescaled images of the galaxies, we can measure surface brightnesses as deep as mu_r~31 mag/arcsec^2. The results strongly support the almost ubiquitous presence of stellar halos around disk galaxies, whose spatial distribution is well described by a power-law $ρ\propto r^{-3}$, in a moderately flattened spheroid (c/a~0.6). The colour estimates in g-r and r-i, although uncertain, give a clear indication for extreme…
We investigate the photometric properties of 456 bright galaxies using imaging data recorded during the commissioning phase of the Sloan Digital Sky Survey (SDSS). Morphological classification is carried out by correlating results of several human classifiers. Our purpose is to examine the statistical properties of color indices, scale lengths, and concentration indices as functions of morphology for the SDSS photometric system. We find that $u'-g'$, $g'-r'$, and $r'-i'$ colors of SDSS galaxies match well with those expected from the synthetic calculation of spectroscopic energy distribution o…
This proceedings contribution summarizes first results obtained from a systematic study of 2011 NLS1 galaxies, as presented in Zhou et al. (2006, ApJS 166, 128). The sample was compiled by examining the spectral parameters of galaxies and QSOs derived from SDSS DR3 data. We discuss some preliminary results on the statistic properties of the sample, such as the fraction of NLS1, the properties of broad and narrow emission lines, and emission in other wavebands. The black hole mass--velocity dispersion relation for NLS1s was re-examined using the velocity dispersion values estimated from the ste…
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 residu…
We present measurements of the redshift--space three-point correlation function of galaxies in the Sloan Digital Sky Survey (SDSS). For the first time, we analyze the dependence of this statistic on galaxy morphology, color and luminosity. In order to control systematics due to selection effects, we used $r$--band, volume-limited samples of galaxies, constructed from the magnitude-limited SDSS data ($14.5<r<17.5$), and further divided the samples into two morphological types (early and late) or two color populations (red and blue). The three-point correlation function of SDSS galaxies follow t…
Using the star formation rates from the SDSS galaxy sample, extracted using the MOPED algorithm, and the empirical Kennicutt law relating star formation rate to gas density, we calculate the time evolution of the gas fraction as a function of the present stellar mass. We show how the gas-to-stars ratio varies with stellar mass, finding good agreement with previous results for smaller samples at the present epoch. For the first time we show clear evidence for progressive gas loss with cosmic epoch, especially in low-mass systems. We find that galaxies with small stellar masses have lost almost …
We present a first morphometric investigation of a preliminary sample from the SDSS of 154287 galaxies with apparent magnitude 14.5<m_r<17.5 and redshift 0.001<z<0.4. We measure the Minkowski Functionals, which are a complete set of morphological descriptors. To account for the complicated wedge--like geometry of the present survey data, we construct isodensity contour surfaces from the galaxy positions in redshift space and employ two complementary methods of computing the Minkowski Functionals. We find that the observed Minkowski Functionals for SDSS galaxies are consistent with the predicti…
In order to explore the statistical properties of galaxy morphological types in compact groups (CGs), we construct a random group sample which has the same distributions of redshift and number of member galaxies as those of the CG sample. It turns out that the proportion of early-type galaxies in different redshift bins for the CG sample is statistically higher than that for random group sample, and with growing redshift z this kind of difference becomes more significant. This may be due to the existence of interactions and mergers within a significant fraction of SDSS CGs. We also compare sta…
We have identified a sample of 41 low-mass high--oxygen abundance outliers from the mass--metallicity relation of star-forming galaxies measured by Tremonti et al (2004). These galaxies, which have 8.6 < [12 + log(O/H)] < 9.3 over a range of -14.4 > M_B > -19.1 and 7.4 < log M_*/M_solar < 10, are surprisingly non-pathological. They have typical specific star formation rates, are fairly isolated and, with few exceptions, have no obvious companions. Morphologically, they are similar to dwarf spheroidal or dwarf elliptical galaxies. We predict that their observed high oxygen abundances are due to…
We analyse the environment of low redshift, z < 0.2, SDSS quasars using the spectral and photometric information of galaxies from the Sloan Digital Sky Survey Third Data Release (SDSS-DR3). We compare quasar neighbourhoods with field and high density environments through an analysis on samples of typical galaxies and groups. We compute the surrounding surface number density of galaxies finding that quasar environments systematically avoid high density regions. Their mean environments correspond to galaxy density enhancements similar to those of typical galaxies. We have also explored several g…
We explore the correlation between morphological types and mid-infrared (MIR) properties of an optically flux-limited sample of 154 galaxies from the Forth Data Release (DR4) of Sloan Digital Sky Survey (SDSS), cross-correlated with Spitzer SWIRE (Spitzer Wide-Area InfraRed Extragalactic Survey) fields of ELAIS-N1, ELAIS-N2 and Lockman Hole. Aperture photometry is performed on the SDSS and Spitzer images to obtain optical and MIR properties. The morphological classifications are given based on both visual inspection and bulge-disk decomposition on SDSS g- and r-band images. The average bulge-t…
We derive the Fundamental Plane (FP) relation for a sample of 1430 early-type galaxies in the optical (r band) and the near-infrared (K band), by combining SDSS and UKIDSS data. With such a large, homogeneous dataset, we are able to assess the dependence of the FP on the waveband. Our analysis indicates that the FP of luminous early-type galaxies is essentially waveband independent, with its coefficients increasing at most by 8% from the optical to the NIR. This finding fits well into a consistent picture where the tilt of the FP is not driven by stellar populations, but results from other eff…
We select the Luminous Infrared Galaxies by cross-correlating the Faint Source Catalogue (FSC) and Point Source Catalogue (PSC) of the IRAS Survey with the Second Data Release of the SDSS for studying their infrared and optical properties. The total number of our sample is 1267 for FSC and 427 for PSC by using 2$σ$ significance level cross-section. The "likelihood ratio" method is used to estimate the sample's reliability and for a more reliable subsample (908 for FSC and 356 for PSC) selection. Then a Catalog with both the infrared, optical and radio informations is presented and will be used…
A new method for a simultaneous search for clusters of galaxies in X-ray photon maps and optical galaxy maps is described. The merging of X-ray and optical data improves the source identification so that a large amount of telescope time for spectroscopic follow-up can be saved. The method appears thus ideally suited for the analysis of the recently proposed wide-angle X-ray missions like DUO and ROSITA. As a first application, clusters are extracted from the 3rd version of the ROSAT All-Sky Survey and the Early Date Release of the Sloan Digital Sky Survey (SDSS). The time-consuming computation…
The 2dF-SDSS LRG and QSO (2SLAQ) survey is a new survey of distant Luminous Red Galaxies (LRGs) and faint quasars selected from the Sloan Digital Sky Survey (SDSS) multi-color photometric data and spectroscopically observed using the 2dF instrument on the Anglo-Australian Telescope (AAT). In total, the 2SLAQ survey has measured over 11000 LRG redshifts, covering 180deg^2 of SDSS imaging data, from 87 allocated nights of AAT time. Over 90% of these galaxies are within the range 0.45<z<0.7 and have luminosities consistent with >=3L*. When combined with the lower redshift SDSS LRGs, the evolution…
We analyse $u-r$ colour distributions for several samples of galaxies in groups drawn from the Fourth Data Release of the Sloan Digital Sky Survey. For all luminosity ranges and environments considered the colour distributions are well described by the sum of two Gaussian functions. We find that the fraction of galaxies in the red sequence is an increasing function of group virial mass. We also study the evolution of the galaxy colour distributions at low redshift, $z\le0.18$ in the field and in groups for galaxies brighter than $M_r-5\log(h)=-20$, finding significant evidence of recent evolut…
We discuss the panchromatic properties of 99,088 galaxies selected from the SDSS Data Release 1 spectroscopic sample (a flux-limited sample for 1360 deg^2). These galaxies are positionally matched to sources detected by ROSAT, GALEX, 2MASS, IRAS, GB6, FIRST, NVSS and WENSS. We find strong correlations between the detection fraction at other wavelengths and optical properties such as flux, colors, and emission-line strengths. Using GALEX, SDSS, and 2MASS data, we construct the UV-IR broad-band spectral energy distributions for various types of galaxies, and find that they form a nearly one-para…
We study the environment of active galaxies and compare it with that of star forming and normal galaxies. We extracted from the Fourth Data Release (DR4) of the Sloan Digitaly Sky Survey (SDSS) the galaxies in the redshift range 0.05 \le z \le 0.095 and with M(r) \le -20.0 (that is M* + 1.45). Emission line ratios and/or widths are used to separate Active Galactic Nuclei (AGN) from Star-Forming Galaxies (SFGs); AGN are classified as Seyfert-1 and Seyfert-2 galaxies according to emission line widths. The environmental properties, as defined by a density parameter and the number of companions, a…
In the unusual intrinsic QSO redshift models, QSOs are ejected by active galaxies with periodic non-cosmological reshifts, thus QSOs are generally associated with active galaxies, and certain structures will be revealed in the QSO redshift distribution. As the largest homogeneous sample of QSOs and galaxies, SDSS data provide the best opportunity to examine this issue. We review the debates on this issue, focused on those based on SDSS and 2dF data, and conclude that there is no strong connection between foreground active galaxies and high-redshift QSOs. The existence of two dips in the SDSS Q…
We use a sample of galaxies from the Sloan Digital Sky Survey (SDSS) to search for correlations between the $λ$ spin parameter and the environment and mass of galaxies. In order to calculate the total value of $λ$ for each observed galaxy, we employed a simple model of the dynamical structure of the galaxies which allows a rough estimate of the value of $λ$ using only readily obtainable observables from the luminous galaxies. Use of a large volume limited sample (upwards of 11,000) allows reliable inferences of mean values and dispersions of $λ$ distributions. We find, in agreement with some N…
We study the dependence of the isophotal shape of early-type galaxies on their absolute B-band magnitude, their dynamical mass, and their nuclear activity and environment, using an unprecedented large sample of 847 early-type galaxies identified in the SDSS by Hao et al (2006). We find that the fraction of disky galaxies smoothly decreases with increasing luminosity. The large sample allows us to describe these trends accurately with tight linear relations that are statistically robust against the uncertainty in the isophotal shape measurements. There is also a host of significant correlations…
We present a sample of 42 high-mass low-metallicity outliers from the mass--metallicity relation of star-forming galaxies. These galaxies have stellar masses that span log(M_*/M_sun) ~9.4 to 11.1 and are offset from the mass--metallicity relation by -0.3 to -0.85 dex in 12+log(O/H). In general, they are extremely blue, have high star formation rates for their masses, and are morphologically disturbed. Tidal interactions are expected to induce large-scale gas inflow to the galaxies' central regions, and we find that these galaxies' gas-phase oxygen abundances are consistent with large quantitie…
We present the first analysis of three-dimensional genus statistics for the SDSS EDR galaxy sample. Due to the complicated survey volume and the selection function, analytic predictions of the genus statistics for this sample are not feasible, therefore we construct extensive mock catalogs from N-body simulations in order to compare the observed data with model predictions. This comparison allows us to evaluate the effects of a variety of observational systematics on the estimated genus for the SDSS sample, including the shape of the survey volume, the redshift distortion effect, and the radia…
The Millennium Galaxy Catalogue (MGC) is a deep ($μ_{\rm B,lim}=26$ mag arcsec$^{-2}$), wide field CCD imaging survey, covering 37.5deg$^2$ and is completely contained within the 2dFGRS and SDSS-EDR. We compare the photometry and completeness of the 2dFGRS and the SDSS-EDR with the MGC. We have also undertaken a photometric comparison to SCOS and SDSS-DR1 data. We find that $B_{MGC}-B_{2dF}=0.035$ mag with an uncertainty of 0.142 mag per galaxy, $B_{MGC}-B_{SCOS}=0.032$ mag with an uncertainty of 0.108 mag, $B_{MGC}-B_{SDSS-EDR}=0.032$ mag with an uncertainty of 0.094 mag, and $B_{MGC}-B_{SDSS…
We have analysed, for the first time, the clustering properties of Wolf-Rayet (W-R) galaxies, using a large sample of 846 W-R galaxies selected from the Data Release 4 (DR4) of the SDSS. We compute the cross-correlation function between W-R galaxies and a reference sample of galaxies drawn from the DR4. We compare the function to the results for control samples of non-W-R star-forming galaxies that are matched closely in redshift, luminosity, concentration, 4000-Åbreak strength and specific star formation rate (SSFR). On scales larger than a few Mpc, W-R galaxies have almost the same clusterin…
We summarize the detection rates at wavelengths other than optical for \~99,000 galaxies from the Sloan Digital Sky Survey (SDSS) Data Release 1 ``main'' spectroscopic sample. The analysis is based on positional cross-correlation with source catalogs from ROSAT, 2MASS, IRAS, GB6, FIRST, NVSS and WENSS surveys. We find that the rest-frame UV-IR broad-band galaxy SEDs form a remarkably uniform, nearly one parameter, family. As an example, the SDSS u and r band data, supplemented with redshift, can be used to predict K band magnitudes measured by 2MASS with an rms scatter of only 0.2 mag; when me…
We have constructed a large, uniform galaxy cluster catalog from the Sloan Digital Sky Survey data. By studying the morphology--cluster-centric-radius relation, we have found two characteristic environments where galaxy morphologies change dramatically, indicating there exist two different physical mechanisms responsible for the cluster galaxy evolution. We also found an unusual population of galaxies, which have spiral morphology but do not have any emission lines, indicating these spiral galaxies do not have any on-going star formation activity. More interestingly, these passive spiral galax…
We have quantified the average filamentarity of the galaxy distribution in seven nearly two dimensional strips from the SDSS DR5 using a volume limited sample in the absolute magnitude range -21 < M_r < -20. The average filamentarity of star forming (SF) galaxies, which are predominantly blue, is found to be more than that of other galaxies which are predominantly red. This difference is possibly an outcome of the fact that blue galaxies have a more filamentary distribution. Comparing the SF galaxies with only the blue other galaxies, we find that the two show nearly equal filamentarity. Separ…
We present our optical multicolor photometry for the nearby cluster of galaxies Abell 2255 with 13 intermediate filters in the BATC system. The spectral energy distributions (SEDs) in the optical band for more than 7000 sources are achieved down to V ~ 20 in a field of 58' x 58' centered on this rich cluster. Abell 2255 has been recently observed by the SDSS. A method of combining the SDSS photometric data in five broad bands and the BATC SEDs is then explored. The application of the technique of photometric redshift shows that the combined SEDs with higher resolution could lead to a more accu…
We consider nonlinear biasing models of galaxies with particular attention to a correlation between linear and quadratic biasing coefficients, b_1 and b_2. We first derive perturbative expressions for b_1 and b_2 in halo and peak biasing models. Then we compute power spectra and bispectra of dark matter particles and halos using N-body simulation data and of volume-limited subsamples of Sloan Digital Sky Survey (SDSS) galaxies, and determine their b_1 and b_2. We find that the values of those coefficients at linear regimes (k<0.2h/Mpc) are fairly insensitive to the redshift-space distortion an…
We investigate the environmental dependence of galaxy population properties in a complete volume-limited sample of 91566 galaxies in the redshift range 0.05 <= z <= 0.095 and with M_r <= -20.0, selected from the Sloan Digital Sky Survey (SDSS) Data Release 4. Our aim is to search for systematic variations in the properties of galaxies with the local galaxy density. In particular, we analize how the (u - r) color index and the morphological type of galaxies (the latter evaluated through the SDSS Eclass and FracDev parameters) are related to the environment and to the luminosity of galaxies, in …
The angular distribution of galaxies encodes a wealth of information about large scale structure. Ultimately, the Sloan Digital Sky Survey (SDSS) will record the angular positions of order 10^8 galaxies in five bands, adding significantly to the cosmological constraints. This is the first in a series of papers analyzing a rectangular stripe 2.5x90 degrees from early SDSS data. We present the angular correlation function for galaxies in four separate magnitude bins on angular scales ranging from 0.003 degrees to 15 degrees. Much of the focus of this paper is on potential systematic effects. We …
We compare the most successful and widely used map of Galactic dust extinction, provided by Schlegel, Finkbeiner & Davis (1998; hereafter SFD), to the galaxy number counts in the Sloan Digital Sky Survey (SDSS) photometric/spectroscopic DR4 sample. We divide the SDSS survey area into 69 disjoint subregions according to the dust extinction provided by SFD and compare the surface number density of galaxies in each subregion. As expected, the galaxy surface number density decreases with increasing extinction but only for SFD extinction values above about 0.1 to 0.2 magnitudes (depending on the ba…
We present ultraviolet photometry for a sample of morphologically early-type galaxies selected by matching the Sloan Digital Sky Survey Data Release 1 with the GALEX Medium and All-sky Imaging Surveys. We obtain a working sample of 1032 early-type galaxies with GALEX FUV detections, SDSS spectroscopy, and $z<0.2$. Using the SDSS spectra to identify galaxies with even weak star formation or evidence of AGN, and further removing galaxies with any evidence of non early-type morphology, we derive a final sample of 172 red quiescent early-type galaxies. We find that the $FUV-r$ color has a full ran…
