arXiv subjects

D. L. Tucker

Publications and source records attributed to D. L. Tucker.

161 records · Page 9Linked to original sources

arXiv2003

Merging Galaxies in the SDSS EDR

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 the component galaxies' radii. We discuss the characteristics of the sample in terms of completeness, pair separation, and the Holmberg effect. We also present an online atlas of images for the SDSS EDR pairs obtained using the corrected frames from the SDSS EDR database. The atlas images also include the relevant data for each pair member. This catalog will be useful for conducting studies of the general characteristics of merging galaxies, their environments, and their component galaxies. The redshifts for a subset of the interacting and merging galaxies and the distribution of angular sizes for these systems indicate the SDSS provides a much deeper sample than almost any other wide-area catalog to date.

astro-ph↗

arXiv2003

Las Campanas Loose Groups in the Supercluster-Void Network

We study the spatial distribution of loose groups from the Las Campanas Redshift Survey, comparing it with the supercluster-void network delineated by rich clusters of galaxies. We use density fields and the friends-of-friends algorithm to identify the members of superclusters of Abell clusters among the Las Campanas loose groups. We find that systems of loose groups tend to be oriented perpendicularly to the line-of-sight, and discuss possible reasons for that. We show that loose groups in richer systems (superclusters of Abell clusters) are themselves also richer and more massive than groups in systems without Abell clusters. Our results indicate that superclusters, as high density environments, have a major role in the formation and evolution of galaxy systems.

astro-ph↗

arXiv2003

Clusters and Superclusters in the Las Campanas Redshift Survey

Two-dimensional high-resolution density field of galaxies of the Las Campanas Redshift Survey (LCRS) with a smoothing length 0.8 Mpc/h is used to extract clusters and groups of galaxies, and a low-resolution field with a smoothing length 10 Mpc/h to find superclusters of galaxies. Properties of these density field (DF) clusters and superclusters are studied and compared with the properties of Abell clusters and superclusters, and LCRS loose groups. We calculate the DF-cluster luminosity function, and show that most luminous clusters in high-density environments are about ten times brighter than most luminous clusters in low-density environments. We present a catalogue of DF-superclusters and show that superclusters that contain Abell clusters are richer and more luminous than superclusters without Abell clusters. A pdf file of the paper with high-resolution figures is available in Tartu Observatory web-site (http://www.aai.ee/~maret/cosmoweb.html)

astro-ph↗

arXiv2002

Luminosity function and density field of the Sloan and Las Campanas Redshift Survey

The luminosity function of galaxies of the Early Data Release of the Sloan Digital Sky Survey (SDSS) and the Las Campanas Redshift Survey (LCRS) is calculated. The luminosity function depends on redshift, density of the environment and is different for the Norther and Southern slice of SDSS. Luminosity functions is used to derive the number and luminosity density fields of galaxies of the SDSS and LCRS surveys with a grid size of 1 h^{-1} Mpc for flat cosmological models with Ω_m=0.3 and Ω_Λ=0.7. We find that the luminosity function depends on the density of the environment: in high-density regions brightest galaxies are more luminous than in low-density regions by a factor up to 5.

astro-ph↗

arXiv2002

Clusters and Superclusters in the Sloan Digital Sky Survey

Two-dimensional high-resolution density field of galaxies of the Early Data Release of the Sloan Digital Sky Survey with a smoothing lengths 0.8 h^{-1} Mpc is applied to extract clusters of galaxies, and a low-resolution field with smoothing lengths 10^{-1} Mpc to extract superclusters of galaxies. We compare properties of density field clusters and superclusters with Abell clusters, and superclusters found on the basis of Abell clusters. We found that clusters in high-density environment have a luminosity a factor of about 5 higher than in low-density environment. There exists a large anisotropy between the SDSS Northern and Southern sample in the properties of clusters and superclusters: most luminous clusters and superclusters in the Northern sample are a factor of 2 more luminous than the respective systems in the Southern sample.

astro-ph↗

arXiv2002

Environmental Enhancement of Loose Groups around Rich Clusters of Galaxies

We have studied the properties of Las Campanas Loose Groups in the neighbourhood of rich (Abell, APM and X-ray) clusters of galaxies. These loose groups show strong evidence of segregation measured in terms of the group richness and the group velocity dispersion: loose groups in the neighbourhood of a rich cluster are typically 2.5 times more massive and 1.6 times more luminous than groups on average, and these loose groups havevelocity dispersions 1.3 times larger than groups on average. This is evidence that the large-scale gravitational field causing the formation of rich clusters enhances the evolution of neighbouring poor systems, a phenomenon recently established in numerical simulations of group and cluster formation.

astro-ph↗

arXiv2002

The mass function of the Las Campanas loose groups of galaxies

We have determined the mass function of loose groups of galaxies in the Las Campanas Redshift Survey. Loose groups of galaxies in the LCRS range in mass from $M \sim 10^{12} {\rm M}_{\sun}$ to $10^{15} {\rm M}_{\sun}$. We find that the sample is almost complete for masses in the interval $5\cdot 10^{13}-8\cdot 10^{14} {\rm M}_{\sun}$. Comparison of the observed mass function with theoretical mass functions obtained from N-body simulations shows good agreement with a CDM model with the parameters $Ω_m = 0.3$, $Ω_Λ = 0.7$ and the amplitude of perturbations about $σ_8=0.78-0.87$. For smaller masses the mass function of LCRS loose groups flattens out, differing considerably from the group mass function found by Girardi and Giuricin (2000) and from mass functions obtained by numerical simulations.

astro-ph↗

arXiv2002

Large Scale Structure in the SDSS Galaxy Survey

The Large Scale Structure (LSS) in the galaxy distribution is investigated using the Sloan Digital Sky Survey Early Data Release (SDSS EDR). Using the Minimal Spanning Tree technique we have extracted sets of filaments, of wall-like structures, of galaxy groups, and of rich clusters from this unique sample. The physical properties of these structures were then measured and compared with the expectations from Zel'dovich' theory. The measured characteristics of galaxy walls were found to be consistent with those for a spatially flat $Λ$CDM cosmological model with $Ω_m\approx$ 0.3 and $Ω_Λ\approx$ 0.7, and for Gaussian initial perturbations with a Harrison -- Zel'dovich power spectrum. Furthermore, we found that the mass functions of groups and of unrelaxed structure elements generally fit well with the expectations from Zel'dovich' theory, although there was some discrepancy for lower mass groups which may be due to incompleteness in the selected sample of groups. We also note that both groups and rich clusters tend to prefer the environments of walls, which tend to be of higher density, rather than the environments of filaments, which tend to be of lower density. Finally, we note evidence of systematic differences in the properties of the LSS between the Northern Galactic Cap stripe and the Southern Galactic Cap stripe -- in particular, in the physical properties of the walls, their spatial distribution, and the relative numbers of clusters embedded in walls. Because the mean separation of walls is $\approx$ 60 -- 70$h^{-1}$ Mpc, each stripe only intersects a few tens of walls. Thus, small number statistics and cosmic variance are the likely drivers of these systematic differences.

astro-ph↗

arXiv2002

The u'g'r'i'z' Standard Star Network

We present the 158 standard stars that define the u'g'r'i'z' photometric system. These stars form the basis for the photometric calibration of the Sloan Digital Sky Survey (SDSS). The defining instrument system and filters, the observing process, the reduction techniques, and the software used to create the stellar network are all described. We briefly discuss the history of the star selection process, the derivation of a set of transformation equations for the UBVRcIc system, and plans for future work.

astro-ph↗

arXiv2001

LOTIS, Super-LOTIS, SDSS and Tautenburg Observations of GRB 010921

We present multi-instrument optical observations of the High Energy Transient Explorer (HETE-2)/Interplanetary Network (IPN) error box of GRB 010921. This event was the first gamma ray burst (GRB) localized by HETE-2 which has resulted in the detection of an optical afterglow. In this paper we report the earliest known observations of the GRB010921 field, taken with the 0.11-m Livermore Optical Transient Imaging System (LOTIS) telescope, and the earliest known detection of the GRB010921 optical afterglow, using the 0.5-m Sloan Digital Sky Survey Photometric Telescope (SDSS PT). Observations with the LOTIS telescope began during a routine sky patrol 52 minutes after the burst. Observations were made with the SDSS PT, the 0.6-m Super-LOTIS telescope, and the 1.34-m Tautenburg Schmidt telescope at 21.3, 21.8, and 37.5 hours after the GRB, respectively. In addition, the host galaxy was observed with the USNOFS 1.0-m telescope 56 days after the burst. We find that at later times (t > 1 day after the burst), the optical afterglow exhibited a power-law decline with a slope of $α= 1.75 \pm 0.28$. However, our earliest observations show that this power-law decline can not have extended to early times (t < 0.035 day).

astro-ph↗

arXiv2001

Spectroscopic Target Selection for the Sloan Digital Sky Survey: The Luminous Red Galaxy Sample

We describe the target selection and resulting properties of a spectroscopic sample of luminous, red galaxies (LRG) from the imaging data of the Sloan Digital Sky Survey (SDSS). These galaxies are selected on the basis of color and magnitude to yield a sample of luminous, intrinsically red galaxies that extends fainter and further than the main flux-limited portion of the SDSS galaxy spectroscopic sample. The sample is designed to impose a passively-evolving luminosity and rest-frame color cut to a redshift of 0.38. Additional, yet more luminous, red galaxies are included to a redshift of 0.5. Approximately 12 of these galaxies per square degree are targeted for spectroscopy, so the sample will number over 100,000 with the full survey. SDSS commissioning data indicate that the algorithm efficiently selects luminous (M_g=-21.4), red galaxies, that the spectroscopic success rate is very high, and that the resulting set of galaxies is approximately volume-limited out to z=0.38. When the SDSS is complete, the LRG spectroscopic sample will fill over 1h^-3 Gpc^3 with an approximately homogeneous population of galaxies and will therefore be well suited to studies of large-scale structure and clusters out to z=0.5.

astro-ph↗

arXiv2000

Compact Groups of Galaxies in the Las Campanas Redshift Survey

We have recently extracted a catalog of compact groups of galaxies (CGs) from the Las Campanas Redshift Survey. This catalog of Las Campanas Compact Groups (LCCGs) contains 76 CGs with a median redshift of z_med = 0.08. The physical properties of these CGs are similar to those from the Hickson (1982) and the Barton et al. (1996) catalogs. Here, we present an atlas of our catalog and briefly describe its general properties.

astro-ph↗

arXiv2000

Loose Groups of Galaxies in the Las Campanas Redshift Survey

A ``friends-of-friends'' percolation algorithm has been used to extract a catalogue of dn/n = 80 density enhancements (groups) from the six slices of the Las Campanas Redshift Survey (LCRS). The full catalogue contains 1495 groups and includes 35% of the LCRS galaxy sample. A clean sample of 394 groups has been derived by culling groups from the full sample which either are too close to a slice edge, have a crossing time greater than a Hubble time, have a corrected velocity dispersion of zero, or contain a 55-arcsec ``orphan'' (a galaxy with a mock redshift which was excluded from the original LCRS redshift catalogue due to its proximity to another galaxy -- i.e., within 55 arcsec). Median properties derived from the clean sample include: line-of-sight velocity dispersion sigma_los = 164km/s, crossing time t_cr = 0.10/H_0, harmonic radius R_h = 0.58/h Mpc, pairwise separation R_p = 0.64/h Mpc, virial mass M_vir = (1.90x10^13)/h M_sun, total group R-band luminosity L_tot = (1.30x10^11)/h^2 L_sun, and R-band mass-to-light ratio M/L = 171h M_sun/L_sun; the median number of observed members in a group is 3.

astro-ph↗

arXiv1999

The Universe on Very Large Scales: A View from the Las Campanas Redshift Survey

The Las Campanas Redshift Survey (LCRS) is among the first galaxy redshift surveys to sample a reasonably fair volume of the local Universe. On the largest scales (>> 100/h Mpc), the galaxy distribution appears smooth; on relatively small scales (<10/h Mpc), the LCRS tends to confirm the clustering characteristics observed in previous, shallower surveys. Here, however, we concern ourselves primarily with clustering on scales near the transition to homogeneity (50-200/h Mpc). We conclude that the general evidence tends to support enhanced clustering on ~ 100/h Mpc scales, but that this result should be confirmed with additional analyses of the LCRS dataset (especially 2D analyses) and with investigations of new and upcoming large-scale surveys covering different regions and/or having different selection effects.

astro-ph↗

arXiv1997

Groups of Galaxies in the Las Campanas Redshift Survey

A "friends-of-friends" percolation algorithm has been used to extract a catalogue of drho/rho = 80 density enhancements (groups) from the six slices of the Las Campanas Redshift Survey (LCRS). The full catalogue contains 1495 groups and includes 35% of the LCRS galaxy sample. A statistical sample of 394 groups has been derived by culling groups from the full sample which either are too close to a slice edge, have a crossing time greater than a Hubble time, have a corrected velocity dispersion of zero or less, or contain a 55 arcsec "orphan" (a galaxy with a "faked" redshift excluded from the original LCRS redshift catalogue due to its proximity --- i.e., within 55 arcsec --- of another galaxy). Median properties derived from the statistical sample include: line-of-sight velocity dispersion sigma_los = 164 km/s, crossing time t_cr = 0.10/H_0, harmonic radius R_h = 0.58/h Mpc, pairwise separation R_p = 0.64/h Mpc, virial mass M_vir = (1.90x10^13)/h M_sun, total group R-band luminosity L_tot = (1.40x10^11)/h^2 L_sun, and R-band mass-to-light ratio M/L = 153h M_sun/L_sun.

astro-ph↗

arXiv1997

ROSAT Public PSPC Observations in the Las Campanas Redshift Survey

The Las Campanas Redshift Survey, an optically selected survey which contains 26,418 galaxy redshifts, has been correlated with ``The First ROSAT Source Catalogue of Pointed Observations with the PSPC,'' which contains 50,408 sources from 2876 ROSAT pointed observations. Ten matches were found. The optical spectra of most of the ten matches show weak narrow emission lines. Due to their high x-ray luminosities, their high x-ray--to--optical flux ratios, and the evidence of rapid x-ray variability in the two brightest matches, we interpret the majority of these objects to be narrow-line Seyfert galaxies or ``hidden'' active galactic nuclei. Of the ten matches, only one galaxy shows the characteristics of a bona fide starburst.

astro-ph↗

arXiv1996

The Las Campanas Redshift Survey Galaxy-Galaxy Autocorrelation Function

Presented are measurements of the observed redshift-space galaxy-galaxy autocorrelation function, xi(s), for the Las Campanas Redshift Survey (LCRS). For separations 2.0/h Mpc < s < 16.4/h Mpc, xi(s) can be approximated by a power law with slope of -1.52 +/- 0.03 and a correlation length of s_0 = (6.28 +\- 0.27)/h Mpc. A zero-crossing occurs on scales of roughly 30 - 40/h Mpc. On larger scales, xi(s) fluctuates closely about zero, indicating a high level of uniformity in the galaxy distribution on these scales. In addition, two aspects of the LCRS selection criteria - a variable field-to-field galaxy sampling rate and a 55 arcsec galaxy pair separation limit - are tested and found to have little impact on the measurement of xi(s). Finally, the LCRS xi(s) is compared with those from numerical simulations; it is concluded that, although the LCRS xi(s) does not discriminate sharply among modern cosmological models, redshift-space distortions in the LCRS xi(s) will likely provide a strong test of theory.

astro-ph↗