THE STELLAR MASS FUNDAMENTAL PLANE AND COMPACT QUIESCENT GALAXIES AT<i>z</i>< 0.6

Zahid, H. Jabran,Damjanov, Ivana,Geller, Margaret J.,Hwang, Ho Seong,Fabricant, Daniel G. American Astronomical Society 2016 The Astrophysical Journal Vol.821 No.2

<P>We examine the evolution of the relation between stellar mass surface density, velocity dispersion, and half-light radius-the stellar mass fundamental plane (MFP)-for quiescent galaxies at z < 0.6. We measure the local relation from galaxies in the Sloan Digital Sky Survey and the intermediate redshift relation from similar to 500 quiescent galaxies with stellar masses 10 less than or similar to log(M*/M-circle dot) less than or similar to 11.5. Nearly half of the quiescent galaxies in our intermediate redshift sample are compact. After accounting for important selection and systematic effects, the velocity dispersion distribution of galaxies at intermediate redshifts is similar to that of galaxies in the local universe. Galaxies at z < 0.6 appear to be smaller (less than or similar to 0.1 dex) than galaxies in the local sample. The orientation of the stellar MFP is independent of redshift for massive quiescent galaxies at z < 0.6 and the zero-point evolves by similar to 0.04 dex. Compact quiescent galaxies fall on the same relation as the extended objects. We confirm that compact quiescent galaxies are the tail of the size and mass distribution of the normal quiescent galaxy population.</P>

THE SCALING OF STELLAR MASS AND CENTRAL STELLAR VELOCITY DISPERSION FOR QUIESCENT GALAXIES AT<i>z</i>< 0.7

Zahid, H. Jabran,Geller, Margaret J.,Fabricant, Daniel G.,Hwang, Ho Seong American Astronomical Society 2016 The Astrophysical Journal Vol.832 No.2

<P>We examine the relation between stellar mass and central stellar velocity dispersion-the M*sigma relation-for massive quiescent galaxies at z < 0.7. We measure the local relation from the Sloan Digital Sky Survey and the intermediate redshift relation from the Smithsonian Hectospec Lensing Survey. Both samples are highly complete (>85%) and we consistently measure the stellar mass and velocity dispersion for the two samples. The M*sigma relation and its scatter are independent of redshift with sigma proportional to M*(0.3) for M* greater than or similar to 10(10.3) M-circle dot. The measured slope of the M*sigma relation is the same as the scaling between the total halo mass and the dark matter halo velocity dispersion obtained by N-body simulations. This consistency suggests that massive quiescent galaxies are virialized systems, where the central dark matter concentration is either a constant or negligible fraction of the stellar mass. The relation between the total galaxy mass (stellar + dark matter) and the central stellar velocity dispersion is consistent with the observed relation between the total mass of a galaxy cluster and the velocity dispersion of the cluster members. This result suggests that the central stellar velocity dispersion is directly proportional to the velocity dispersion of the dark matter halo. Thus, the central stellar velocity dispersion is a fundamental, directly observable property of galaxies, which may robustly connect galaxies to dark matter halos in N-body simulations. To interpret the results further in the context of Lambda CDM, it would be useful to analyze the relationship between the velocity dispersion of stellar particles and the velocity dispersion characterizing their dark matter halos in high-resolution cosmological hydrodynamic simulations.</P>

A RISE IN THE IONIZING PHOTONS IN STAR-FORMING GALAXIES OVER THE PAST 8 BILLION YEARS

Kewley, Lisa J.,Zahid, H. Jabran,Geller, Margaret J.,Dopita, Michael A.,Hwang, Ho Seong,Fabricant, Dan IOP Publishing 2015 ASTROPHYSICAL JOURNAL LETTERS - Vol.812 No.2

<P>We investigate the change in ionizing photons in galaxies in the range 0.2 < z < 0.6 using the F2 field of the SHELS complete galaxy redshift survey. We show, for the first time, that while the [O III]/H beta and [O III]/[O II] ratios rise, the [N II]/H alpha and [S II]/H alpha ratios fall significantly over the 0.2 < z < 0.35 redshift range for stellar masses in the range 9.2 < log(M/M-circle dot) < 10.6. The [O III]/H beta and [O III]/[O II] ratios continue to rise across the full 0.2 < z < 0.6 redshift range for stellar masses in the range 9.8 < log(M/M-circle dot) < 10.0. We conclusively rule out active galactic nucleus contamination, a changing ISM pressure, and a change in the hardness of the EUV radiation field as the cause of the change in the line ratios in the range 0.2 < z < 0.35. We find that the ionization parameter rises significantly with redshift (by 0.1-0.25 dex depending on the stellar mass of the sample). We show that the ionization parameter is strongly correlated with the fraction of young-to-old stars, as traced by the H mu equivalent width. We discuss the implications of this result on higher redshift studies, and we consider the implications on the use of standard optical metallicity diagnostics at high redshift.</P>

hCOSMOS: A Dense Spectroscopic Survey of <i>r</i> ≤ 21.3 Galaxies in the COSMOS field

Damjanov, Ivana,Zahid, H. Jabran,Geller, Margaret J.,Fabricant, Daniel G.,Hwang, Ho Seong American Astronomical Society 2018 The Astrophysical journal Supplement series Vol.234 No.2

<P>We describe the hCOSMOS redshift survey of the COSMOS field conducted with the Hectospec spectrograph on the MMT. In the central 1. deg(2), the hCOS20.6 subset of the survey is > 90% complete to a limiting magnitude r = 20.6. The hCOSMOS survey includes 1701 new redshifts in the COSMOS field. We also use the total of 4362 new and remeasured objects to derive the age-sensitive D(n)4000 index over the entire redshift interval 0.001 less than or similar to z less than or similar to 0.6. For 85% of the quiescent galaxies in hCOS20.6, we measure the central line-of-sight velocity dispersion. To explore potential uses of this survey, we combine previously measured galaxy sizes, profiles, and stellar masses with the spectroscopy. The comparison reveals the known relations among structural, kinematic, and stellar population properties. We also compare redshift and Dn4000 distributions of hCOS20.6 galaxies with SHELS; a complete spectroscopic survey of 4 deg(2) observed to the same depth. The redshift distributions in the two fields are very different, but the Dn4000 distribution is remarkably similar. The relation between velocity dispersion and stellar mass for massive hCOS20.6 galaxies is consistent with the local relation from the Sloan Digital Sky Survey. Using measured velocity dispersions, we test a photometric proxy calibrated to galaxies in the local universe. The systematic differences between the measured and photometric proxy velocity dispersions are correlated with galaxy dynamical and stellar population properties highlighting the importance of direct spectroscopic measurements.</P>

QUIESCENT COMPACT GALAXIES AT INTERMEDIATE REDSHIFT IN THE COSMOS FIELD. THE NUMBER DENSITY

Damjanov, Ivana,Geller, Margaret J.,Zahid, H. Jabran,Hwang, Ho Seong IOP Publishing 2015 The Astrophysical journal Vol.806 No.2

<P>We investigate the evolution of compact galaxy number density over the redshift range 0.2 < z < 0.8. Our sample consists of galaxies with secure spectroscopic redshifts observed in the COSMOS field. With the large uncertainties, the compact galaxy number density trend with redshift is consistent with a constant value over the interval 0.2 < z < 0.8. Our number density estimates are similar to the estimates at z > 1 for equivalently selected compact samples. Small variations in the abundance of the COSMOS compact sources as a function of redshift correspond to known structures in the field. The constancy of the compact galaxy number density is robust and insensitive to the compactness threshold or the stellar mass range (for M-* > 10(10) M-circle dot). To maintain constant number density any size growth of high-redshift compact systems with decreasing redshift must be balanced by a formation of quiescent compact systems at z < 1.</P>

Testing Weak-Lensing Maps of Galaxy Clusters with Dense Redshift Surveys Testing Weak-Lensing Maps of Galaxy Clusters with Dense Redshift Surveys

Ho Seong Hwang,Margaret J. Geller,Antonaldo Diaferio,Kenneth J. Rines,H. Jabran Zahid 한국천문학회 2014 天文學會報 Vol.39 No.2

CATALOGS OF COMPACT GROUPS OF GALAXIES FROM THE ENHANCED SDSS DR12

Sohn, Jubee,Geller, Margaret J.,Hwang, Ho Seong,Zahid, H. Jabran,Lee, Myung Gyoon American Astronomical Society 2016 The Astrophysical journal Supplement series Vol.225 No.2

<P>We apply a friends-of-friends algorithm to an enhanced SDSS DR12 spectroscopic catalog, including redshift from the literature to construct a catalog of 1588 N >= 3 compact groups of galaxies containing 5178 member galaxies and covering the redshift range 0.01 < z < 0.19. This catalog contains 18 times as many systems and reaches 3 times the depth of the similar catalog of Barton et al. We construct catalogs from both magnitude-limited and volume-limited galaxy samples. Like Barton et al. we omit the frequently applied isolation criterion in the compact group selection algorithm. Thus the groups selected by fixed projected spatial and rest-frame line-of-sight velocity separation produce a catalog of groups with a redshift-independent median size. In contrast to previous catalogs, the enhanced SDSS DR12 catalog (including galaxies with r < 14.5) includes many systems with z less than or similar to 0.05. The volume-limited samples are unique to this study. The compact group candidates in these samples have a median stellar mass independent of redshift. Groups with velocity dispersion. less than or similar to 100 km s(-1) show abundant evidence for ongoing dynamical interactions among the members. The number density of the volume-limited catalogs agrees with previous catalogs at the lowest redshifts but decreases as the redshift increases. The SDSS fiber placement constraints limit the catalog's completeness. In spite of this issue, the volume-limited catalogs provide a promising basis for detailed spatially resolved probes of the impact of galaxy-galaxy interactions within similar dense systems over a broad redshift range.</P>

COMPARING DENSE GALAXY CLUSTER REDSHIFT SURVEYS WITH WEAK-LENSING MAPS

Hwang, Ho Seong,Geller, Margaret J.,Diaferio, Antonaldo,Rines, Kenneth J.,Zahid, H. Jabran IOP Publishing 2014 The Astrophysical journal Vol.797 No.2

<P>We use dense redshift surveys of nine galaxy clusters at z similar to 0.2 to compare the galaxy distribution in each system with the projected matter distribution from weak lensing. By combining 2087 new MMT/Hectospec redshifts and the data in the literature, we construct spectroscopic samples within the region of weak-lensing maps of high (70%-89%) and uniform completeness. With these dense redshift surveys, we construct galaxy number density maps using several galaxy subsamples. The shape of the main cluster concentration in the weak-lensing maps is similar to the global morphology of the number density maps based on cluster members alone, mainly dominated by red members. We cross-correlate the galaxy number density maps with the weak-lensing maps. The cross-correlation signal when we include foreground and background galaxies at 0.5z(cl) < z < 2z(cl) is 10%-23% larger than for cluster members alone at the cluster virial radius. The excess can be as high as 30% depending on the cluster. Cross-correlating the galaxy number density and weak-lensing maps suggests that superimposed structures close to the cluster in redshift space contribute more significantly to the excess cross-correlation signal than unrelated large-scale structure along the line of sight. Interestingly, the weak-lensing mass profiles are not well constrained for the clusters with the largest cross-correlation signal excesses (>20% for A383, A689, and A750). The fractional excess in the cross-correlation signal including foreground and background structures could be a useful proxy for assessing the reliability of weak-lensing cluster mass estimates.</P>

HECTOMAP AND HORIZON RUN 4: DENSE STRUCTURES AND VOIDS IN THE REAL AND SIMULATED UNIVERSE

Hwang, Ho Seong,Geller, Margaret J.,Park, Changbom,Fabricant, Daniel G.,Kurtz, Michael J.,Rines, Kenneth J.,Kim, Juhan,Diaferio, Antonaldo,Zahid, H. Jabran,Berlind, Perry,Calkins, Michael,Tokarz, Susa American Astronomical Society 2016 The Astrophysical journal Vol.818 No.2

<P>HectoMAP is a dense redshift survey of red galaxies covering a 53 deg(2) strip of the northern sky. HectoMAP is 97% complete for galaxies with r < 20.5, (g-r) > 1.0, and (r -i) > 0.5. The survey enables tests of the physical properties of large-scale structure at intermediate redshift against cosmological models. We use the Horizon Run 4, one of the densest and largest cosmological simulations based on the standard. Cold Dark Matter (Lambda CDM) model, to compare the physical properties of observed large-scale structures with simulated ones in a volume-limited sample covering 8 x 10(6) h(-3) Mpc(3) in the redshift range 0.22 < z < 0.44. We apply the same criteria to the observations and simulations to identify over-and under-dense large-scale features of the galaxy distribution. The richness and size distributions of observed over-dense structures agree well with the simulated ones. Observations and simulations also agree for the volume and size distributions of under-dense structures, voids. The properties of the largest over-dense structure and the largest void in HectoMAP are well within the distributions for the largest structures drawn from 300 Horizon Run 4 mock surveys. Overall the size, richness and volume distributions of observed large-scale structures in the redshift range 0.22 < z < 0.44 are remarkably consistent with predictions of the standard Lambda CDM model.</P>