Ronald Olowin | Saint Mary's College of California (original) (raw)
Papers by Ronald Olowin
Astronomy & Astrophysics, 2011
The GALEX Ultraviolet Virgo Cluster Survey (GUViCS) is a complete blind survey of the Virgo clust... more The GALEX Ultraviolet Virgo Cluster Survey (GUViCS) is a complete blind survey of the Virgo cluster covering about 40 sq. deg. in the far UV (FUV, lambda_eff=1539A, Delta-lambda=442A) and about 120 sq. deg. in the near UV (NUV, lambda_eff=2316A, Delta-lambda=1060A). The goal of the survey is to study the ultraviolet (UV) properties of galaxies in a rich cluster environment, spanning a wide luminosity range from giants to dwarfs, and regardless of prior knowledge of their star formation activity. The UV data will be combined with those in other bands (optical: NGVS; far-infrared - submm: HeViCS; HI: ALFALFA) and with our multizone chemo-spectrophotometric models of galaxy evolution to make a complete and exhaustive study of the effects of the environment on the evolution of galaxies in high density regions. We present here the scientific objectives of the survey, describing the observing strategy and briefly discussing different data reduction techniques. Using UV data already in-hand for the central 12 sq. deg. we determine the FUV and NUV luminosity functions of the Virgo cluster core for all cluster members and separately for early- and late-type galaxies and compare it to the one obtained in the field and other nearby clusters (Coma, A1367). This analysis shows that the FUV and NUV luminosity functions of the core of the Virgo clusters are flatter (alpha about -1.1) than those determined in Coma and A1367. We discuss the possible origin of this difference
Astronomy & Astrophysics, 1995
The results of spectroscopic observations of five R greater than or equal to 1 clusters of galaxi... more The results of spectroscopic observations of five R greater than or equal to 1 clusters of galaxies from the Abell (1958) and Abell et al. (1989) (hereafter ACO) catalogs are presented. The observations were conducted at the ESO 3.6m telescope with the EFOSC spectrograph and PUMA hole-punch aperture plates. Two of the clusters (A2576 and A2628) had been identified as members of one candidate supercluster that appears particularly dense in projection, and the other three clusters (A3802, A3817, and A3834) were in another candidate supercluster, based on redshifts estimated from the magnitudes of tenth brightest galaxies. Our observations confirm very similar redshifts for A2576 and A2628 ( z = 0.1875 and z = 0.1858, respectively) and for A3802 and A3834 (z = 0.1579 and z = 0.1518). From the agreement in redshifts and the proximity on the sky, it is suggestive that both pairs are indeed components of superclusters, although redshifts of other nearby candidates must be measured to determine the significance of the structure present. The fifth cluster, A3817, has a mean redshift of z = 0.2115, and so appears to be background to any possible A3802/A3834 supercluster. We note that the complex of clusters around A2576 and A2628 is a region of high spatial density, even ignoring the many clusters with unmeasured redshift. The region is an exceptional opportunity for large-scale structure study.
Presented is the description of 55 bright close (z less than or equal to 0.1) clusters of galaxie... more Presented is the description of 55 bright close (z less than or equal to 0.1) clusters of galaxies as a homogeneous sample taken from a new effort to catalog galaxy clusters in the Southern Hemisphere. The positions of some 21,000 galaxies in clusters have been catalogued along with visual magnitudes, morphological types, position angles of extended objects and pertinent remarks. For all of the clusters, various cluster parameters have been determined and form the basis of comparative studies for these fundamental aggregates of matter in the universe. The aims of this study are to produce a homogeneous sample of galaxy clusters measured to a uniform limiting magnitude mv = 19.0 by means of a calibrated stepscale; catalogued with accurate positions relative to nearby astrometric standard stars; morphologically classified and population typed; and statistically analyzed in a uniform fashion to deduce certain cluster parameters. The cluster parameters of interest include an estimate of cluster distance, cluster center and cluster richness, galaxy distributions as a function of morphological type, magnitude distribution and core radius as determined by an isothermal gas sphere model.
Monthly Notices of The Royal Astronomical Society, 1973
Astronomical Journal, 2011
We present a current catalog of 21 cm HI line sources extracted from the Arecibo Legacy Fast Arec... more We present a current catalog of 21 cm HI line sources extracted from the Arecibo Legacy Fast Arecibo L-band Feed Array (ALFALFA) survey over ~2800 square degrees of sky: the alpha.40 catalog. Covering 40% of the final survey area, the alpha.40 catalog contains 15855 sources in the regions 07h30m < R.A. < 16h30m, +04 deg < Dec. < +16 deg and +24 deg < Dec. < +28 deg and 22h < R.A. < 03h, +14 deg < Dec. < +16 deg and +24 deg < Dec. < +32 deg. Of those, 15041 are certainly extragalactic, yielding a source density of 5.3 galaxies per square degree, a factor of 29 improvement over the catalog extracted from the HI Parkes All Sky Survey. In addition to the source centroid positions, HI line flux densities, recessional velocities and line widths, the catalog includes the coordinates of the most probable optical counterpart of each HI line detection, and a separate compilation provides a crossmatch to identifications given in the photometric and spectroscopic catalogs associated with the Sloan Digital Sky Survey Data Release 7. Fewer than 2% of the extragalactic HI line sources cannot be identified with a feasible optical counterpart; some of those may be rare OH megamasers at 0.16 < z < 0.25. A detailed analysis is presented of the completeness, width dependent sensitivity function and bias inherent in the current alpha.40 catalog. The impact of survey selection, distance errors, current volume coverage and local large scale structure on the derivation of the HI mass function is assessed. While alpha.40 does not yet provide a completely representative sampling of cosmological volume, derivations of the HI mass function using future data releases from ALFALFA will further improve both statistical and systematic uncertainties.
Astronomy Letters-a Journal of Astronomy and Space Astrophysics, 1993
The 3D 2-point correlation function xi(R) for a sample of 70 Abell clusters in the richness class... more The 3D 2-point correlation function xi(R) for a sample of 70 Abell clusters in the richness class 2 or greater and redshifts of z between 0.06 and 0.24 in the southern galactic hemisphere (southern semi-cone) is calculated. Redshifts for 30 clusters from the sample were measured directly; for other clusters, the Leir-van den Bergh estimates were used. The validity of the method used was tested on a previously used sample from the northern cone region. The correlation function has a peak of xi = 0.6 at R = 250(50/H) Mpc, as in the case of the Northern cone sample. The peak disappears when a larger sample including less rich Abell clusters of the same region is used. A list of 23 new values of z for Abell clusters in the southern galactic hemisphere, measured with a 6-m telescope, is also presented.
The southern extension of the Abell Catalogue of Rich Clusters of Galaxies has been completed (Ab... more The southern extension of the Abell Catalogue of Rich Clusters of Galaxies has been completed (Abell, Corwin and Olowin 1989, hereafter ACO) and for the most part is compatible with the survey done by Abell in 1957. The southern data have been collected from the ESO/SRC southern sky survey, using the UK 1.2-m Schmidt Telescope IIIa-J plates and films, and have been reduced to the systems defined by the northern data previously published by Abell (1958). A revised northern catalogue, including Bautz-Morgan types and redshifts where known, is also included in the new complilation. The new catalogue contains data on 4073 rich clusters of galaxies, each of which has at least 30 members within the magnitude range m 3 to m 3 +2, where m 3 is the magnitude of the third brightest cluster member, and with each cluster having a nominal redshift less than 0.2.
Astrophysical Journal, 1989
The distribution of rich clusters of galaxies in the new southern catalog of Abell, Corwin, and O... more The distribution of rich clusters of galaxies in the new southern catalog of Abell, Corwin, and Olowin (ACO, 1989) is examined. A comparison with the cluster distribution in the northern Abell catalog, published in 1958, is presented. The similarities as well as the differences between the catalogs are highlighted. The angular cluster correlation function of the ACO catalog is consistent with the Abell cluster correlation, showing strong superclustering to about 50/h Mpc. The correlation amplitude scales with depth, as expected for real spatial clustering. Plate-to-plate variation effects are investigated; no significant impact of the latter on the cluster correlation is observed.
Astrophysical Journal, 1989
Astrophysical Journal, 1999
We report the discovery of two highly extended filaments and one extremely high density knot with... more We report the discovery of two highly extended filaments and one extremely high density knot within the region of Aquarius. The supercluster candidates were chosen via percolation analysis of the Abell and ACO catalogs and include only the richest clusters (R >= 1). The region examined is a 10x45 degree strip and is now 87% complete in cluster redshift measurements to mag_10 = 18.3. In all, we report 737 galaxy redshifts in 46 cluster fields. One of the superclusters, dubbed Aquarius, is comprised of 14 Abell/ACO clusters and extends 110h^-1Mpc in length only 7 degrees off the line-of-sight. On the near-end of the Aquarius filament, another supercluster, dubbed Aquarius-Cetus, extends for 75h^-1Mpc perpendicular to the line-of-sight. After fitting ellipsoids to both Aquarius and Aquarius-Cetus, we find axis ratios (long-to- midlength axis) of 4.3 for Aquarius and 3.0 for Aquarius-Cetus. We fit ellipsoids to all N>=5 clumps of clusters in the Abell/ACO measured-z cluster sample. The frequency of filaments with axis ratios >=3.0 (~20%) is nearly identical with that found among `superclusters' in Monte Carlo simulations of random and random- clumped clusters, however, so the rich Abell/ACO clusters have no particular tendency toward filamentation. The Aquarius filament also contains a `knot' of 6 clusters at Z ~0.11, with five of the clusters near enough togeteher to represent an apparent overdensity of 150. There are three other R >= 1 cluster density enhancements similar to this knot at lower redshifts: Corona Borealis, the Shapely Concentration, and another grouping of seven clusters in Microscopium. All four of these dense superclusters appear near the point of breaking away from the Hubble Flow, and some may now be in collapse, but there is little evidence of any being virialized.
This talk covered material from two papers that have been submitted for publication elsewhere. Th... more This talk covered material from two papers that have been submitted for publication elsewhere. The first of these papers (Paper 1) was “The Distribution of Clusters in the Southern ACO Catalogue”, submitted to The Astrophysical Journal. The second (Paper 2) was “The Correlation Function of Southern Clusters”, The Astrophysical Journal (Letters), 333, L13 (1988). An extended abstract of each paper follows.
Astronomy & Astrophysics, 2011
The GALEX Ultraviolet Virgo Cluster Survey (GUViCS) is a complete blind survey of the Virgo clust... more The GALEX Ultraviolet Virgo Cluster Survey (GUViCS) is a complete blind survey of the Virgo cluster covering about 40 sq. deg. in the far UV (FUV, lambda_eff=1539A, Delta-lambda=442A) and about 120 sq. deg. in the near UV (NUV, lambda_eff=2316A, Delta-lambda=1060A). The goal of the survey is to study the ultraviolet (UV) properties of galaxies in a rich cluster environment, spanning a wide luminosity range from giants to dwarfs, and regardless of prior knowledge of their star formation activity. The UV data will be combined with those in other bands (optical: NGVS; far-infrared - submm: HeViCS; HI: ALFALFA) and with our multizone chemo-spectrophotometric models of galaxy evolution to make a complete and exhaustive study of the effects of the environment on the evolution of galaxies in high density regions. We present here the scientific objectives of the survey, describing the observing strategy and briefly discussing different data reduction techniques. Using UV data already in-hand for the central 12 sq. deg. we determine the FUV and NUV luminosity functions of the Virgo cluster core for all cluster members and separately for early- and late-type galaxies and compare it to the one obtained in the field and other nearby clusters (Coma, A1367). This analysis shows that the FUV and NUV luminosity functions of the core of the Virgo clusters are flatter (alpha about -1.1) than those determined in Coma and A1367. We discuss the possible origin of this difference
Astronomy & Astrophysics, 1995
The results of spectroscopic observations of five R greater than or equal to 1 clusters of galaxi... more The results of spectroscopic observations of five R greater than or equal to 1 clusters of galaxies from the Abell (1958) and Abell et al. (1989) (hereafter ACO) catalogs are presented. The observations were conducted at the ESO 3.6m telescope with the EFOSC spectrograph and PUMA hole-punch aperture plates. Two of the clusters (A2576 and A2628) had been identified as members of one candidate supercluster that appears particularly dense in projection, and the other three clusters (A3802, A3817, and A3834) were in another candidate supercluster, based on redshifts estimated from the magnitudes of tenth brightest galaxies. Our observations confirm very similar redshifts for A2576 and A2628 ( z = 0.1875 and z = 0.1858, respectively) and for A3802 and A3834 (z = 0.1579 and z = 0.1518). From the agreement in redshifts and the proximity on the sky, it is suggestive that both pairs are indeed components of superclusters, although redshifts of other nearby candidates must be measured to determine the significance of the structure present. The fifth cluster, A3817, has a mean redshift of z = 0.2115, and so appears to be background to any possible A3802/A3834 supercluster. We note that the complex of clusters around A2576 and A2628 is a region of high spatial density, even ignoring the many clusters with unmeasured redshift. The region is an exceptional opportunity for large-scale structure study.
Presented is the description of 55 bright close (z less than or equal to 0.1) clusters of galaxie... more Presented is the description of 55 bright close (z less than or equal to 0.1) clusters of galaxies as a homogeneous sample taken from a new effort to catalog galaxy clusters in the Southern Hemisphere. The positions of some 21,000 galaxies in clusters have been catalogued along with visual magnitudes, morphological types, position angles of extended objects and pertinent remarks. For all of the clusters, various cluster parameters have been determined and form the basis of comparative studies for these fundamental aggregates of matter in the universe. The aims of this study are to produce a homogeneous sample of galaxy clusters measured to a uniform limiting magnitude mv = 19.0 by means of a calibrated stepscale; catalogued with accurate positions relative to nearby astrometric standard stars; morphologically classified and population typed; and statistically analyzed in a uniform fashion to deduce certain cluster parameters. The cluster parameters of interest include an estimate of cluster distance, cluster center and cluster richness, galaxy distributions as a function of morphological type, magnitude distribution and core radius as determined by an isothermal gas sphere model.
Monthly Notices of The Royal Astronomical Society, 1973
Astronomical Journal, 2011
We present a current catalog of 21 cm HI line sources extracted from the Arecibo Legacy Fast Arec... more We present a current catalog of 21 cm HI line sources extracted from the Arecibo Legacy Fast Arecibo L-band Feed Array (ALFALFA) survey over ~2800 square degrees of sky: the alpha.40 catalog. Covering 40% of the final survey area, the alpha.40 catalog contains 15855 sources in the regions 07h30m < R.A. < 16h30m, +04 deg < Dec. < +16 deg and +24 deg < Dec. < +28 deg and 22h < R.A. < 03h, +14 deg < Dec. < +16 deg and +24 deg < Dec. < +32 deg. Of those, 15041 are certainly extragalactic, yielding a source density of 5.3 galaxies per square degree, a factor of 29 improvement over the catalog extracted from the HI Parkes All Sky Survey. In addition to the source centroid positions, HI line flux densities, recessional velocities and line widths, the catalog includes the coordinates of the most probable optical counterpart of each HI line detection, and a separate compilation provides a crossmatch to identifications given in the photometric and spectroscopic catalogs associated with the Sloan Digital Sky Survey Data Release 7. Fewer than 2% of the extragalactic HI line sources cannot be identified with a feasible optical counterpart; some of those may be rare OH megamasers at 0.16 < z < 0.25. A detailed analysis is presented of the completeness, width dependent sensitivity function and bias inherent in the current alpha.40 catalog. The impact of survey selection, distance errors, current volume coverage and local large scale structure on the derivation of the HI mass function is assessed. While alpha.40 does not yet provide a completely representative sampling of cosmological volume, derivations of the HI mass function using future data releases from ALFALFA will further improve both statistical and systematic uncertainties.
Astronomy Letters-a Journal of Astronomy and Space Astrophysics, 1993
The 3D 2-point correlation function xi(R) for a sample of 70 Abell clusters in the richness class... more The 3D 2-point correlation function xi(R) for a sample of 70 Abell clusters in the richness class 2 or greater and redshifts of z between 0.06 and 0.24 in the southern galactic hemisphere (southern semi-cone) is calculated. Redshifts for 30 clusters from the sample were measured directly; for other clusters, the Leir-van den Bergh estimates were used. The validity of the method used was tested on a previously used sample from the northern cone region. The correlation function has a peak of xi = 0.6 at R = 250(50/H) Mpc, as in the case of the Northern cone sample. The peak disappears when a larger sample including less rich Abell clusters of the same region is used. A list of 23 new values of z for Abell clusters in the southern galactic hemisphere, measured with a 6-m telescope, is also presented.
The southern extension of the Abell Catalogue of Rich Clusters of Galaxies has been completed (Ab... more The southern extension of the Abell Catalogue of Rich Clusters of Galaxies has been completed (Abell, Corwin and Olowin 1989, hereafter ACO) and for the most part is compatible with the survey done by Abell in 1957. The southern data have been collected from the ESO/SRC southern sky survey, using the UK 1.2-m Schmidt Telescope IIIa-J plates and films, and have been reduced to the systems defined by the northern data previously published by Abell (1958). A revised northern catalogue, including Bautz-Morgan types and redshifts where known, is also included in the new complilation. The new catalogue contains data on 4073 rich clusters of galaxies, each of which has at least 30 members within the magnitude range m 3 to m 3 +2, where m 3 is the magnitude of the third brightest cluster member, and with each cluster having a nominal redshift less than 0.2.
Astrophysical Journal, 1989
The distribution of rich clusters of galaxies in the new southern catalog of Abell, Corwin, and O... more The distribution of rich clusters of galaxies in the new southern catalog of Abell, Corwin, and Olowin (ACO, 1989) is examined. A comparison with the cluster distribution in the northern Abell catalog, published in 1958, is presented. The similarities as well as the differences between the catalogs are highlighted. The angular cluster correlation function of the ACO catalog is consistent with the Abell cluster correlation, showing strong superclustering to about 50/h Mpc. The correlation amplitude scales with depth, as expected for real spatial clustering. Plate-to-plate variation effects are investigated; no significant impact of the latter on the cluster correlation is observed.
Astrophysical Journal, 1989
Astrophysical Journal, 1999
We report the discovery of two highly extended filaments and one extremely high density knot with... more We report the discovery of two highly extended filaments and one extremely high density knot within the region of Aquarius. The supercluster candidates were chosen via percolation analysis of the Abell and ACO catalogs and include only the richest clusters (R >= 1). The region examined is a 10x45 degree strip and is now 87% complete in cluster redshift measurements to mag_10 = 18.3. In all, we report 737 galaxy redshifts in 46 cluster fields. One of the superclusters, dubbed Aquarius, is comprised of 14 Abell/ACO clusters and extends 110h^-1Mpc in length only 7 degrees off the line-of-sight. On the near-end of the Aquarius filament, another supercluster, dubbed Aquarius-Cetus, extends for 75h^-1Mpc perpendicular to the line-of-sight. After fitting ellipsoids to both Aquarius and Aquarius-Cetus, we find axis ratios (long-to- midlength axis) of 4.3 for Aquarius and 3.0 for Aquarius-Cetus. We fit ellipsoids to all N>=5 clumps of clusters in the Abell/ACO measured-z cluster sample. The frequency of filaments with axis ratios >=3.0 (~20%) is nearly identical with that found among `superclusters' in Monte Carlo simulations of random and random- clumped clusters, however, so the rich Abell/ACO clusters have no particular tendency toward filamentation. The Aquarius filament also contains a `knot' of 6 clusters at Z ~0.11, with five of the clusters near enough togeteher to represent an apparent overdensity of 150. There are three other R >= 1 cluster density enhancements similar to this knot at lower redshifts: Corona Borealis, the Shapely Concentration, and another grouping of seven clusters in Microscopium. All four of these dense superclusters appear near the point of breaking away from the Hubble Flow, and some may now be in collapse, but there is little evidence of any being virialized.
This talk covered material from two papers that have been submitted for publication elsewhere. Th... more This talk covered material from two papers that have been submitted for publication elsewhere. The first of these papers (Paper 1) was “The Distribution of Clusters in the Southern ACO Catalogue”, submitted to The Astrophysical Journal. The second (Paper 2) was “The Correlation Function of Southern Clusters”, The Astrophysical Journal (Letters), 333, L13 (1988). An extended abstract of each paper follows.