Point Source Catalog Redshift Survey Research Articles

THE ROLE OF MAJOR GAS-RICH MERGERS ON THE EVOLUTION OF GALAXIES FROM THE BLUE CLOUD TO THE RED SEQUENCE

ABSTRACT With the aim of exploring the fast evolutionary path from the blue cloud of star-forming galaxies to the red sequence of quiescent galaxies in the local universe, we select a local advanced merging infrared luminous and ultraluminous galaxy (adv-merger (U)LIRGs) sample and perform careful dust extinction corrections to investigate their positions in the star formation rate–M *, u − r, and NUV − r color–mass diagrams. The sample consists of 89 (U)LIRGs at the late merger stage, obtained from cross-correlating the Infrared Astronomical Satellite Point Source Catalog Redshift Survey and 1 Jy ULIRGs samples with the Sloan Digital Sky Survey DR7 database. Our results show that of adv-merger (U)LIRGs are localized above the 1σ line of the local star-forming galaxy main sequence. We also find that all adv-merger (U)LIRGs are more massive than and as blue as the blue cloud galaxies after corrections for Galactic and internal dust extinctions, with and of them outside the blue cloud on the u − r and NUV − r color–mass diagrams, respectively. These results, combined with the short timescale for exhausting the molecular gas reservoir in adv-merger (U)LIRGs ( to years), imply that the adv-merger (U)LIRGs are likely at the starting point of the fast evolutionary track previously proposed by several groups. While the number density of adv-merger (U)LIRGs is only of the blue cloud star-forming galaxies in the local universe, this evolutionary track may play a more important role at high redshift.

Observational evidence for the evolution of nuclear metallicity and star formation rate with the merger stage

We investigate the evolution of nuclear gas-phase oxygen abundance and star formation rate (SFR) of local far-infrared selected star-forming galaxies along the merger sequence, as traced by their optical morphologies. The sample was drawn from a cross-correlation analysis of the IRAS Point Source Catalog Redshift Survey and 1 Jy ultraluminous infrared galaxy sample with the Sloan Digital Sky Survey Data Release 7 database. The investigation is done by comparing our sample to a control sample matched in the normalized redshift distribution in two diagnostics, which are the nuclear gas-phase metallicity vs. stellar mass and the nuclear SFR vs. stellar mass diagrams. Galaxies with different morphological types show different mass-metallicity relations (MZRs). Compared to the MZR defined by the control sample, isolated spirals have comparable metallicities with the control sample at a given stellar mass. Spirals in pairs and interacting galaxies with projected separations of rp > 20 kpc show a mild metallicity dilution of 0.02–0.03 dex. Interacting galaxies with rp < 20 kpc, pre-mergers and advanced mergers are underabundant by ∼ 0.06, ∼ 0.05 and ∼ 0.04 dex, respectively. This shows an evolutionary trend that the metallicity is increasingly depressed as the merging proceeds and it is diluted most dramatically when two galaxies are closely interacting. Afterwards, the interstellar medium (ISM) is enriched when the galaxies coalesce. This is the first time that such ISM enrichment at the final coalescence stage has been observed, which demonstrates the importance of supernova explosions in affecting the nuclear metallicity. Moreover, the central SFR enhancement relative to the control sample evolves simultaneously with the nuclear gas-phase oxygen abundance. Our results support the predictions from numerical simulations.

2MTF – V. Cosmography, β, and the residual bulk flow

Using the Tully-Fisher relation, we derive peculiar velocities for the 2MASS Tully-Fisher Survey and describe the velocity field of the nearby Universe. We use adaptive kernel smoothing to map the velocity field, and compare it to reconstructions based on the redshift space galaxy distributions of the 2MASS Redshift Survey (2MRS) and the IRAS Point Source Catalog Redshift Survey (PSCz). With a standard $\chi^2$ minimization fit to the models, we find that the PSCz model provides a better fit to the 2MTF velocity field data than does the 2MRS model, and provides a value of $\beta$ in greater agreement with literature values. However, when we subtract away the monopole deviation in the velocity zeropoint between data and model, the 2MRS model also produces a value of $\beta$ in agreement with literature values. We also calculate the `residual bulk flow': the component of the bulk flow not accounted for by the models. This is $\sim 250$ km/s when performing the standard fit, but drops to $\sim 150$ km/s for both models when the aforementioned monopole offset between data and models is removed. This smaller number is more in line with theoretical expectations, and suggests that the models largely account for the major structures in the nearby Universe responsible for the bulk velocity.

What size haloes do local LIRGs live in?

This work investigates the preferred environment of local Luminous IR Galaxies (LIRGs) in terms of the host halos that they inhabit, and in comparison to a control galaxy sample. The LIRGs are drawn from the IRAS Point Source Catalogue redshift survey (PSCz), while the control sample is drawn from the 2MASS redshift survey (2MRS). A friends-of-friends algorithm was run on the 2MRS sample to identify galaxies living in the same dark matter halos and the PSCz galaxies were then associated with these identified halos. We show that the relative probability of finding local LIRGs with respect to 2MASS galaxies is largest in approximately group size halos (Mhalo~10^13M_sun), and declines both in the cluster regime and in smaller halos. This confirms, using a different technique than in previous work, that local LIRGs are indeed more abundant in group environments than elsewhere. We also find a trend between the LIR values of LIRGs and their location within their host dark matter halos, such that the average location of LIRGs with high IR luminosity is closer to the halo centre than for low IR luminosity galaxies. Moreover, this trend does not seem to depend on halo mass.

A comparison of the galaxy peculiar velocity field with the PSCz gravity field - a Bayesian hyper-parameter method

We constructed a Bayesian hyper-parameter statistical method to quantify the difference between predicted velocities derived from the observed galaxy distribution in the IRAS-PSCz (Point Source Catalogue Redshift) survey and peculiar velocities measured using different distance indicators. In our analysis, we find that the model–data comparison becomes unreliable beyond 70 h−1 Mpc because of the inadequate sampling by the IRAS survey of prominent, distant superclusters, like the Shapley Concentration. On the other hand, the analysis of the velocity residuals shows that the PSCz gravity field provides an adequate model to the local, ≤70 h−1 Mpc, peculiar velocity field. The hyper-parameter combination of ENEAR, SN, A1SN and SFI++ catalogues in the Bayesian framework constrains the amplitude of the linear flow to be β = 0.53 ± 0.014. For an rms density fluctuation in the PSCz galaxy number density , we obtain an estimate of the growth rate of density fluctuations fσ8(z ∼ 0) = 0.42 ± 0.033, which is in excellent agreement with independent estimates based on different techniques.

Cosmic flows in the nearby universe from Type Ia supernovae

Peculiar velocities are one of the only probes of very large-scale mass density fluctuations in the nearby Universe. We present new "minimal variance" bulk flow measurements based upon the "First Amendment" compilation of 245 Type Ia supernovae (SNe) peculiar velocities and find a bulk flow of 249 +/- 76 km/s in the direction l= 319 +/- 18 deg, b = 7 +/- 14 deg. The SNe bulk flow is consistent with the expectations of \Lambda CDM. However, it is also marginally consistent with the bulk flow of a larger compilation of non-SNe peculiar velocities (Watkins, Feldman, & Hudson 2009). By comparing the SNe peculiar velocities to predictions of the IRAS Point Source Catalog Redshift survey (PSCz) galaxy density field, we find \Omega_{m}^{0.55} \sigma_{8,lin} = 0.40 +/- 0.07, which is in agreement with \Lambda CDM. However, we also show that the PSCz density field fails to account for 150 +/- 43 km/s of the SNe bulk motion.

The environments of local luminous infrared galaxies: star formation rates increase with density

This work studies the environments and star formation relationships of local luminous infrared galaxies (LIRG) in comparison to other types of local and distant (z~1) galaxies. The infrared (IR) galaxies are drawn from the IRAS sample. The density of the environment is quantified using 6dF and Point Source Catalogue redshift survey (PSCz) galaxies in a cylinder of 2h^-1 Mpc radius and 10h^-1 Mpc length. Our most important result shows the existence of a dramatic density difference between local LIRGs and local non-LIRG IR galaxies. LIRGs live in denser environments than non-LIRG IR galaxies implying that L_IR=10^11 h^-2 L_sun marks an important transition point among IR-selected local galaxies. We also find that there is a strong correlation between the densities around LIRGs and their L_IR luminosity, while the IR-activity of non-LIRG IR galaxies does not show any dependence on environment. This trend is independent of mass-bin selection. The SF-density trend in local LIRGs is similar to that found in some studies of blue cloud galaxies at z~1 which show a correlation between star formation and local density (the reversal of the relation seen for local galaxies). This, together with the rapid decline of the number count of LIRGs since z~1, could mean that local LIRGs are survivors of whatever process transformed blue cloud galaxies at z~1 to the present day or local LIRGs came into existence by similar process than high redshift LIRGs but at later stage.

KOREA INSTITUTE FOR ADVANCED STUDY VALUE-ADDED GALAXY CATALOG

We present the Korea Institute for Advanced Study Value-Added Galaxy Catalog (KIAS VAGC), a catalog of galaxies based on the Large Scale Structure (LSS) sample of New York University Value-Added Galaxy Catalog (NYU VAGC) Data Release 7. Our catalog supplements redshifts of 10,497 galaxies with 10 ＜ rP ≤ 17.6 (1455 with 10 ＜ rP ≤ 14.5) to the NYU VAGC LSS sample. Redshifts from various existing catalogs such as the Updated Zwicky Catalog, the IRAS Point Source Catalog Redshift Survey, the Third Reference Catalogue of Bright Galaxies, and the Two Degree Field Galaxy Redshift Survey have been put into the NYU VAGC photometric catalog. Our supplementation significantly improves spectroscopic completeness: the area covered by the spectroscopic sample with completeness higher than 95% increases from 2.119 to 1.737 sr. Our catalog also provides morphological types of all galaxies that are determined by the automated morphology classification scheme of Park & Choi (2005), and related parameters, together with fundamental photometry parameters supplied by the NYU VAGC. Our catalog contains matches to objects in the Max Planck for Astronomy (MPA) & Johns Hopkins University (JHU) spectrum measurements (Data Release 7). This new catalog, the KIAS VAGC, is complementary to the NYU VAGC and MPA-JHU catalog.

Infrared Galaxies in the Nearby Universe

We used the Sloan Digital Sky Survey (SDSS) Data Release 5 (DR5) to study the morphological properties of 1137 nearby infrared (IR) galaxies, most of which are brighter than 15.9 mag in r-band. This sample was drawn from a cross-correlation of the Infra-Red Astronomical Satellite (IRAS) point source catalog redshift survey with DR5 at z 0.08. Based on this IR galaxy sample, we constructed five volume-limited sub-samples with IR luminosity ranging from 109.5L⊙ to 1012L⊙. By deriving the IR luminosity functions (LF) for different morphological types, we found that normal spiral galaxies are the dominant population below LIR~8×1010 L⊙; while the fraction of barred spiral galaxies increases with increasing IR luminosity and becomes dominant in spiral galaxies beyond LIR5×1010L⊙. As the IR luminosity decreases, the IR galaxies become more compact and have lower stellar masses. The analysis also shows that normal spiral galaxies give the dominant contribution to the total comoving IR energy density in the nearby universe, while, in contrast, the contribution from peculiar galaxies is only 39%.

Gaseous versus Stellar Velocity Dispersion in Emission-Line Galaxies

We compare the ionized gas velocity dispersion σgas with the stellar velocity dispersion σ∗ in star-forming galaxies, composite galaxies, Low Ionization Nuclear Emission-line Regions (LINERs) and Seyfert 2s, compiled from a cross-identification of Sloan Digital Sky Survey Fourth Data Release (SDSS DR4) and Point Source Catalogue Redshift Survey (PSCz). We measure σgas from the FWHMs of emission lines (Hα, [NII]λλ6548, 6583 and [SII]λλ6716, 6731). A significant correlation between the gas and stellar velocity dispersion exists, despite substantial scatter. The mean value of the gas to stellar velocity dispersion ratio is close to unity. This suggests that gas velocity dispersion can substitute for the stellar velocity dispersion as a tracer of the gravitational potential well for all the four types of galaxies, but the involved uncertainties are different from type to type. We also studied gas/σ∗ as a function of the redshift and the axial ratio to test the effects of aperture and galaxy inclination, and found that both effects are weak. Finally we checked the trend of gas/σ∗ with the infrared luminosity and found no significant correlation.

The PSCz dipole revisited

We re-examine the gravitational acceleration (dipole) induced on the Local Group of galaxies by the Infrared Astronomical Satellite (IRAS) galaxy distribution of the Point Source Catalogue redshift survey (PSCz). We treat the cirrus-affected low galactic latitudes by utilizing a spherical harmonic expansion of the galaxy surface density field up to the octapole order. We find strong indications for significant contributions to the Local Group motion from depths up to $\sim 185$ $h^{-1}$ Mpc and possible contribution even from $\sim 210$ $h^{-1}$ Mpc, in agreement with the recent analysis of Kocevski & Ebeling of a whole sky X-ray cluster survey.What changes with respect to the previous PSCz dipole analyses is: (a) the large-scale dipole contributions and (b) an increase of the overall dipole amplitude due to the important contribution of the local volume ($\mincir 4 h^{-1}$Mpc), which we now take into account. This results in a lower value of the $\beta (\equiv \Omega_{\rm m}^{0.6}/b)$ parameter, which we find to be $\beta_{\rm IRAS} \simeq 0.49$ in real space. Therefore, for the concordance cosmological model ($\Omega_{\rm m}=1-\Omega_{\Lambda}=0.3$) the IRAS galaxies bias factor is $b_{\rm IRAS}\simeq 1$ which means that IRAS galaxies are good traces of the underlying matter distribution.

A full-sky prediction of the Sunyaev-Zeldovich effect from diffuse hot gas in the local universe and the upper limit from theWMAPdata

We use the Point Source Catalogue Redshift Survey galaxy redshift catalogue combined with constrained simulations based on the IRAS 1.2-Jy galaxy density field to estimate the contribution of hot gas in the local universe to the Sunyaev‐Zeldovich (SZ) effect on a large scale. We produce a full-sky HEALPIX map predicting the SZ effect from clusters as well as diffuse hot gas within 80 h −1 Mpc. Performing cross-correlation tests between this map and the WMAP data in pixel, harmonic and wavelet space we can put an upper limit on the effect. We conclude that the SZ effect from diffuse gas in the local universe cannot be detected in current cosmic microwave background (CMB) data and is not a large-scale contaminating factor ( �< 60) in studies of CMB angular anisotropies. We derive an upper limit for the mean temperature

The redshift-space two-point correlation function of ELAIS-S1 galaxies

We investigate the clustering properties of galaxies in the recently completed ELAIS-S1 redshift survey through their spatial two-point autocorrelation function. We used a subsample of the ELAIS-S1 catalogue covering approximately 4 deg2 and consisting of 148 objects selected at 15 μm with a flux >0.5 mJy and a redshift z < 0.5. We detected a positive signal in the correlation function that in the range of separations 1–10 h−1 Mpc is well approximated by a power law with a slope γ= 1.4 ± 0.25 and a correlation length s0= 5.4 ± 1.2 h−1 Mpc, at the 90 per cent significance level. This result is in good agreement with the redshift-space correlation function measured in more local samples of mid-infrared-selected galaxies such as the IRAS Point Source Catalog (PSCz) redshift survey. This suggests a lack of significant clustering evolution of infrared-selected objects out to z= 0.5 that is further confirmed by the consistency found between the correlation functions measured in a local (z < 0.2) and a distant (0.2 < z < 0.5) subsample of ELAIS-S1 galaxies. We also confirm that optically selected galaxies in the local redshift surveys, especially those of the SDSS sample, are significantly more clustered than infrared objects.

New York University Value-Added Galaxy Catalog: A Galaxy Catalog Based on New Public Surveys

Here we present the New York University Value-Added Galaxy Catalog (NYU-VAGC), a catalog of local galaxies (mostly below z ≈ 0.3) based on a set of publicly released surveys matched to the Sloan Digital Sky Survey (SDSS) Data Release 2. The photometric catalog consists of 693,319 galaxies, QSOs, and stars; 343,568 of these have redshift determinations, mostly from the SDSS. Excluding areas masked by bright stars, the photometric sample covers 3514 deg2, and the spectroscopic sample covers 2627 deg2 (with about 85% completeness). Earlier, proprietary versions of this catalog have formed the basis of many SDSS investigations of the power spectrum, correlation function, and luminosity function of galaxies. Future releases will follow future public releases of the SDSS. The catalog includes matches to the Two Micron All Sky Survey Point Source Catalog and Extended Source Catalog, the IRAS Point Source Catalog Redshift Survey, the Two-Degree Field Galaxy Redshift Survey, the Third Reference Catalogue of Bright Galaxies, and the Faint Images of the Radio Sky at Twenty cm survey. We calculate and compile derived quantities from the images and spectra of the galaxies in the catalogs (for example, K-corrections and structural parameters for the galaxies). The SDSS catalog presented here is photometrically calibrated in a more consistent way than that distributed by the SDSS Data Release 2 Archive Servers and is thus more appropriate for large-scale structure statistics, reducing systematic calibration errors across the sky from ~2% to ~1%. We include an explicit description of the geometry of the catalog, including all imaging and targeting information as a function of sky position. Finally, we have performed eyeball quality checks on a large number of objects in the catalog in order to flag errors (such as errors in deblending). This catalog is complementary to the SDSS Archive Servers in that NYU-VAGC's calibration, geometric description, and conveniently small size are specifically designed for studying galaxy properties and large-scale structure statistics using the SDSS spectroscopic catalog.

Streaming motions of galaxy clusters within 12 000 km s−1- V. The peculiar velocity field

We analyse in detail the peculiar velocity field traced by 56 clusters within 120 h−1 Mpc in the ‘Streaming Motions of Abell Clusters’ (SMAC) sample. The bulk flow of the SMAC sample is 687 ± 203 km s−1, toward l= 260°± 13°, b= 0°± 11°. We discuss possible systematic errors and show that no systematic effect is larger than half of the random error. The flow does not drop off significantly with depth, which suggests that it is generated by structures on large scales. In particular, a Great Attractor as originally proposed by Lynden-Bell et al. cannot be responsible for the SMAC bulk flow. The SMAC data suggest infall into an attractor at the location of the Shapley Concentration, but the detection is marginal (at the 90 per cent confidence level). We find that distant attractors in addition to the Shapley Concentration are required to explain the SMAC bulk flow. A comparison with peculiar velocities predicted from the IRAS Point Source Catalogue redshift (PSCz) survey shows good agreement with a best-fitting value of βI=Ω0.6m/bI= 0.39 ± 0.17. However, the PSCz density field is not sufficient to account for all of the SMAC bulk motion. We also detect, at the 98 per cent confidence level, a residual bulk flow of 372 ± 127 km s−1 toward l= 273°, b= 6° which must be generated by sources not included in the PSCz catalogue, that is, either beyond 200 h−1 Mpc, in the zone of avoidance or in superclusters undersampled by IRAS. Finally, we compare the SMAC bulk flow with other recent measurements. We argue that, at depths ranging from 60 to 120 h−1 Mpc, flows of order 600 km s−1 are excluded by multiple data sets. However, convergence to the cosmic microwave background frame by a depth of 60 h−1 Mpc is also excluded by multiple data sets. We suggest that a bulk flow of 225 km s−1 toward l= 300°, b= 10° at depths greater than 60 h−1 Mpc is consistent with all peculiar velocity surveys, when allowance is made for sparse sampling effects.

Spatial and Dynamical Biases in Velocity Statistics of Galaxies

We present velocity statistics of galaxies and their biases inferred from the statistics of the underlying dark matter using a cosmological hydrodynamic simulation of galaxy formation in low-density and spatially flat (Ohm(0) = 0.3 and lambda(0) = 0.7) cold dark matter cosmogony. Our simulation is based on a particle-particle-particle-mesh ((PM)-M-3) N-body Poisson solver and smoothed particle hydrodynamics. Galaxies in our simulation are identified as clumps of cold and dense gas particles and classified as young and old galaxies according to their formation epochs. We find that the pairwise velocity dispersion (PVD) of all galaxies is significantly lower than that of the dark matter particles and that the PVD of the young galaxies is lower than that of the old types, and even of all galaxies together, especially at small separations. These results are in reasonable agreement with the recent measurements of PVDs in the Las Campanas redshift survey, the IRAS Point Source Catalogue Redshift Survey, and the Sloan Digital Sky Survey data. We also find that the low PVD of young galaxies is due to the effects of dynamical friction as well as the different spatial distribution, while the difference in the PVD between all galaxies and dark matter can be mostly ascribed to their different spatial distributions. We also consider the mean infall velocity and the POTENT density reconstruction that are often used to measure the cosmological parameters, and investigate the effects of spatial bias and dynamical friction. In our simulation, the mean infall velocity of young galaxies is significantly lower than that of all the galaxies or of the old galaxies, and the dynamical bias becomes important on scales less than 3 h(-1) Mpc. The mass density field reconstructed from the velocity field of young galaxies using the POTENT-style method suffers in accuracy from both the spatial bias and the dynamical friction on the smoothing scale of R-s = 8 h(-1) Mpc. On the other hand, in the case of R-s = 12 h(-1) Mpc, which is typically adopted in the actual POTENT analysis, the density reconstruction based on various tracers of galaxies is reasonably accurate. We also analyze the motions of central galaxies and the velocity dispersion of galaxies within halos and discuss their implications for the motion of cD galaxies and the determination of the mass of galaxy groups.

The real-space power spectrum of the PSCzsurvey from 0.01 to 300 h Mpc−1

We report a measurement of the real-space (not redshift-space) power spectrum of galaxies over four and a half decades of wavenumber, 0.01 to 300 h Mpc - 1 , from the IRAS Point Source Catalog Redshift Survey (PSCz). Sinceestimates of power are highly correlated in the non-linear regime, we also report results for the pre-whitened power spectrum, which is less correlated. The inferred bias between optically selected APM and IRAS-selected PSCz galaxies is about 1.15 at linear scales ≤0.3 h Mpc - 1 , increasing to about 1.4 at non-linear scales ≥1 h Mpc - 1 . The non-linear power spectrum of PSCz shows a near power-law behaviour to the smallest scales measured, with possible mild upward curvature in the broad vicinity of k 2 h Mpc - 1 . Contrary to the prediction of unbiased dark matter models, there is no prominent inflection at the linear to non-linear transition scale, and no turnover at the transition to the virialized regime. The non-linear power spectrum of PSCz requires scale-dependent bias: all Dark Matter models without scale-dependent bias are ruled out with high confidence.

Voids in the Point Source Catalogue Survey and the Updated Zwicky Catalog

We describe an algorithm to detect voids in galaxy redshift surveys. The method is based on the void finder algorithm of El-Ad & Piran. We apply a series of tests to determine how accurately we are able to recover the volumes of voids using our detection method. We simulate voids of different ellipticity and find that if voids are approximately spherical, our algorithm will recover 100% of the volume of the void. The more elliptical the void, the smaller the fraction of the volume we can recover. We insist that voids lie completely within the survey. Voids close to the edge of the survey will therefore be underestimated in volume. By considering a deeper sample, we estimate that the maximal sphere diameters are correct to within 30%. We apply the algorithm to the Point Source Catalog redshift (PSCz) survey and the Updated Zwicky Catalog (UZC). The PSCz survey is an almost all-sky survey with objects selected from the IRAS catalog. The UZC covers a smaller area of sky but is optically selected and samples the structures more densely. We detect 35 voids in the PSCz and 19 voids in the UZC with diameter larger than 20 h-1 Mpc. Using this minimum size threshold, we find that voids have an average effective diameter of 29.8 ± 3.5 h-1 Mpc (PSCz) and 29.2 ± 2.7 h-1 Mpc (UZC) and that they are underdense regions with δρ/ρ values of -0.92 ± 0.03 (PSCz) and -0.96 ± 0.01 (UZC), respectively. Using this quite stringent threshold for void definition, voids fill up to 40% of the volume of the universe.

Detection of Galaxy Spin Alignments in the Point Source Catalog Redshift Survey Shear Field

We report the first direct observational evidence for the alignment of galaxy spin axes with the local tidal shear field. We measure quantitatively the strength of this directional correlation of disk galaxies from the Tully catalog, with the local shear field reconstructed from Point Source Catalog Redshift survey galaxies. We demonstrate that the null hypothesis of random galaxy alignments relative to the shear frame can be ruled out with more than 99.98% confidence. The observed intrinsic correlation averaged over the censored samples that have detected nonzero signals is measured in terms of the alignment parameter = 0.17 ± 0.04, which includes only statistical errors of the censored data but not the cosmic variance error. The reconstruction procedure is likely to underestimate systematically. Our result is consistent with the linear tidal-torque model and supports the idea that the present galaxy spins may be used as a probe of primordial tidal shear and mass density fields. The intrinsic alignments of galaxy spins dominate over weak gravitational lensing for shallow surveys such as the Sloan Digital Sky Survey, while it should be negligible for deeper surveys at z ~ 1.

Spatial Correlation Functions and the Pairwise Peculiar Velocity Dispersion of Galaxies in the Point Source Catalog Redshift Survey: Implications for the Galaxy Biasing in Cold Dark Matter Models

We report on the measurement of the two-point correlation function and the pairwise peculiar velocity of galaxies in the IRAS Point Source Catalog Redshift (PSCz) Survey. We compute these statistics first in redshift space and then obtain the projected functions that have simple relations to the real-space correlation functions on the basis of the method developed earlier in analyzing the Las Campanas Redshift Survey (LCRS) by Jing, Mo, & Borner. We find that the real space two-point correlation function can be fitted to a power law xi(r) = (r(o)/r)(gamma) with gamma = 1.69 and r(o) = 3.70 h(-1) Mpc. The pairwise peculiar velocity dispersion (PVD) sigma(12)(r(p)) is close to 400 km s(-1) at r(p) = 3 h(-1) Mpc and decreases to about 150 km s(-1) at r(p) approximate to 0.2 h(-1) Mpc. These values are significantly lower than those obtained from the LCRS. In order to understand the implications of those measurements on the galaxy biasing, we construct mock samples for a low-density spatially flat cold dark matter model (Omega(o) = 0.3, lambda(o) = 0.7, Gamma = 0.2, sigma(8) = 1), using a set of high-resolution N-body simulations in a box size of 100, 300, and 800 h(-1) Mpc. Applying a stronger cluster underweight biasing (proportional toM(-0.25)) than for the LCRS (proportional toM(-0.08)), we are able to reproduce these observational data, except for the strong decrease of the pairwise peculiar velocity at small separations. This is qualitatively ascribed to the different morphological mixture of galaxies in the two catalogs. Disk-dominated galaxy samples drawn from the theoretically constructed GIF catalog yield results rather similar to our mock samples with the simple cluster underweight biasing. We further apply the phenomenological biasing model in our N-body mock samples, which takes account of the density-morphology relation of galaxies in clusters. The model does not reduce the velocity dispersions of galaxies to the level measured in the PSCz data either. Thus, we conclude that the PVDs of the PSCz galaxies require a biasing model that substantially reduces the PVD on small scales relative to their spatial clustering.