The scale-dependence of relative galaxy bias: encouragement for the halo model description

We investigate the relationship between the colors, luminosities, and environments of galaxies in the Sloan Digital Sky Survey spectroscopic sample, using environmental measurements on scales ranging from 0.2 to 6 Mpc/h. We find: (1) that the relationship between color and environment persists even to the lowest luminosities we probe (absolute magnitude in the r band of about -14 for h=1); (2) at luminosities and colors for which the galaxy correlation function has a large amplitude, it also has a steep slope; and (3) in regions of a given overdensity on small scales (1 Mpc/h), the overdensity on large scales (6 Mpc/h) does not appear to relate to the recent star formation history of the galaxies. Of these results, the last has the most immediate application to galaxy formation theory. In particular, it lends support to the notion that a galaxy's properties are related only to the mass of its host dark matter halo, and not to the larger scale environment.Comment: submitted to ApJ; full resolution figures and slide material available at http://cosmo.nyu.edu/blanton/scale_density.htm

Abundance ratios in hierarchical galaxy formation

The chemical enrichment and stellar abundance ratios of galaxies which form in a hierarchical clustering scheme are calculated. For this purpose I adopt the star formation histories (SFH) as they are delivered by semi-analytic models in Kauffmann (1996}. It turns out that the average SFH of cluster ellipticals does not yield globally alpha-enhanced stellar populations. The star burst that occurs when the elliptical forms in the major merger plays therefore a crucial role in producing alpha-enhancement. Only under the assumption that the IMF is significantly flattened with respect to the Salpeter value during the burst, a Mg/Fe overabundant population can be obtained. In particular for the interpretation of radial gradients in metallicity and alpha-enhancement, the mixing of global and burst populations are of great importance. The model predicts bright field galaxies to be less alpha-enhanced than their counterparts in clusters.Comment: 7 pages, 3 figures, accepted by MNRA

A High Merger Fraction in the Rich Cluster MS1054-03 at z=0.83: Direct Evidence for Hierarchical Formation of Massive Galaxies

We present a morphological study of the galaxy population of the luminous X-ray cluster MS1054-03 at z=0.83. The sample consists of 81 spectroscopically confirmed cluster members in a 3 x 2 Mpc area imaged in F606W and F814W with WFPC2. We find thirteen ongoing mergers in MS1054-03, comprising 17% of the L > L* cluster population. Most of these mergers will likely evolve into luminous (\sim 2 L*) elliptical galaxies, and some may evolve into S0 galaxies. Assuming the galaxy population in MS1054-03 is typical for its redshift it is estimated that \sim 50% of present-day cluster ellipticals experienced a major merger at z < 1. The mergers are preferentially found in the outskirts of the cluster, and probably occur in small infalling clumps. Morphologies, spectra, and colors of the mergers show that their progenitors were typically E/S0s or early-type spirals with mean stellar formation redshifts z* \gtrsim 1.7. The red colors of the merger remnants are consistent with the low scatter in the color-magnitude relation in rich clusters at lower redshift. The discovery of a high fraction of mergers in this young cluster is direct evidence against formation of ellipticals in a single ``monolithic'' collapse at high redshift, and in qualitative agreement with predictions of hierarchical models for structure formation.Comment: Added GIF version of Figure 1. At http://www.astro.rug.nl/~dokkum/preprints/merger_fig1.eps.gz the PS file is available. Accepted for publication in ApJ Letter

The Evolution of Early-Type Galaxies in Distant Clusters III.: M/L_V Ratios in the z=0.33 Cluster CL1358+62

Keck spectroscopy and Hubble Space Telescope WFPC2 imaging over a 1.5x1.5 Mpc field of CL1358+62 at z=0.33 are used to study the Fundamental Plane of galaxies based on a new, large sample of 53 galaxies. First, we have constructed the Fundamental Plane for the 30 E and S0 galaxies and find that it has the following shape: r_e = sigma**(1.31+-0.13) * _e**(-0.86+-0.10), similar to that found locally. The 1-sigma intrinsic scatter about this plane is 14% in M/L(V), comparable to that observed in Coma. We conclude that these E and S0 galaxies are structurally mature and homogeneous, like those observed in nearby clusters. The M/L(V) ratios of these early-type galaxies are offset from the Coma Fundamental Plane by delta log M/L(V) = -0.13+- 0.03 (q0=0.1), indicative of mild luminosity evolution. This evolution suggests a formation epoch for the stars of z > 1. We have also analyzed the M/L(V) ratios of galaxies of type S0/a and later. These early-type spirals follow a different plane from the E and S0 galaxies, with a scatter that is twice as large as the scatter for the E/S0s. The difference in the tilt between the plane of the spirals and the plane of the E/S0s is shown to be due to a systematic correlation of velocity dispersion with residual from the plane of the early-type galaxies. These residuals also correlate with the residuals from the Color-Magnitude relation. Thus for spirals in clusters, we see a systematic variation in the luminosity-weighted mean properties of the stellar populations with central velocity dispersion. If this is a relative age trend, then luminosity-weighted age is positively correlated with dispersion. [abridged version]Comment: 18 pages, 8 figures; revised version, accepted by ApJ on 13 August 199

The Creep and Oxidation Behaviour of Pesting-Resistant (Mo,Ti)5Si3(Mo,Ti)_{5}Si_{3}-Containing Eutectic-Eutectoid Mo-Si-Ti Alloys

In this study we present a series of light-weight (6.24 to 6.42 g/$cm^3$), Ti-rich Mo-Si-Ti alloys (≥40 at.% nominal Ti content) with the hitherto best combination of pesting and creep resistance at 800 and 1200 °C, respectively. This has been achieved by fine-scaled eutectic-eutectoid microstructures with substantial fractions of primarily solidified $(Mo,Ti)_{5}Si_{3}$. $(Mo,Ti)_{5}Si_{3}$ was found to be oxidation-resistant in these alloys and also beneficial for the creep resistance. The enhanced solidus temperature is of specific relevance with respect to the latter point. The creep resistance is competitive to the non-pesting resistant, but most creep-resistant (among the Mo-Si-Ti alloys) eutectoid alloy Mo-21Si-34Ti developed by Schliephake et al. [Schliephake et al., in Intermetallics 104 (2019) pp. 133–142]. Moreover, it is favourably superior to the commercially applied Ni-based single crystal alloy CMSX-4 for the applied compressive loading conditions under vacuum

Infall, the Butcher-Oemler Effect, and the Descendants of Blue Cluster Galaxies at z~0.6

Using wide-field HST/WFPC2 imaging and extensive Keck/LRIS spectroscopy, we present a detailed study of the galaxy populations in MS2053--04, a massive, X-ray luminous cluster at z=0.5866. Analysis of 149 confirmed cluster members shows that MS2053 is composed of two structures that are gravitationally bound to each other; their respective velocity dispersions are 865 km/s (113 members) and 282 km/s (36 members). MS2053's total dynamical mass is 1.2x10^15 Msun. MS2053 is a classic Butcher-Oemler cluster with a high fraction of blue members (24%) and an even higher fraction of star-forming members (44%), as determined from their [OII] emission. The number fraction of blue/star-forming galaxies is much higher in the infalling structure than in the main cluster. This result is the most direct evidence to date that the Butcher-Oemler effect is linked to galaxy infall. In terms of their colors, luminosities, estimated internal velocity dispersions, and [OII] equivalent widths, the infalling galaxies are indistinguishable from the field population. MS2053's deficit of S0 galaxies combined with its overabundance of blue spirals implies that many of these late-types will evolve into S0 members. The properties of the blue cluster members in both the main cluster and infalling structure indicate they will evolve into low mass, L<L* galaxies with extended star formation histories like that of low mass S0's in Coma. Our observations show that most of MS2053's blue cluster members, and ultimately most of its low mass S0's, originate in the field. Finally, we measure the redshift of the giant arc in MS2053 to be z=3.1462; this object is one in only a small set of known strongly lensed galaxies at z>3.Comment: Accepted by ApJ. Version with full resolution figures available at http://www.exp-astro.phys.ethz.ch/tran/outgoing/ms2053.ps.g

A2111: A z=0.23 Butcher-Oemler Cluster with a Non-isothermal Atmosphere and Normal Metallicity

We report results from an X-ray study of the Abell 2111 galaxy cluster using the Advanced Satellite for Astrophysics and Cosmology ASCA and the ROSAT Position Sensitive Proportional Counter (PSPC). By correcting for the energy-dependent point-spread function of the ASCA instruments, we have examined the temperature structure of the cluster. The cluster's core within 3' is found to have a temperature of 6.46+-0.87 keV, significantly higher than 3.10+-1.19 keV in the surrounding region of r = 3 - 6'. This radially decreasing temperature structure can be parameterized by a polytropic index of $\gamma$ $\simeq$ 1.45. The X-ray morphology of the cluster appears elongated and clumpy on scales $\le$1'. These results, together with earlier {\it ROSAT} and optical studies which revealed that the X-ray centroid and ellipticity of A2111 shift with spatial scale, are consistent with the hypothesis that the cluster is a dynamically young system. Most likely, the cluster has recently undergone a merger, which may also be responsible for the high fraction of blue galaxies observed in the cluster. Alternatively, the temperature structure may also be due to the gravitational potential of the cluster. We have further measured the emission weighted abundance of the X-ray-emitting intracluster medium as 0.25$\pm$0.14 solar. This value is similar to those of nearby clusters which do not show a large blue galaxy fraction, indicating that star formation in disk galaxies and subsequent loss to the medium do not drastically alter the average abundance of a cluster. This is consistent with recent results which indicate that cluster abundances have remained constant since at least z ~ 0.3.Comment: accepted by MNRA

Luminosity Evolution of Early-type Galaxies to z=0.83: Constraints on Formation Epoch and Omega

We present deep spectroscopy with the Keck telescope of eight galaxies in the luminous X-ray cluster MS1054-03 at z=0.83. The data are combined with imaging observations from the Hubble Space Telescope (HST). The spectroscopic data are used to measure the internal kinematics of the galaxies, and the HST data to measure their structural parameters. Six galaxies have early-type spectra, and two have "E+A" spectra. The galaxies with early-type spectra define a tight Fundamental Plane (FP) relation. The evolution of the mass-to-light ratio is derived from the FP. The M/L ratio evolves as \Delta log M/L_B \propto -0.40 z (Omega_m=0.3, Omega_Lambda=0). The observed evolution of the M/L ratio provides a combined constraint on the formation redshift of the stars, the IMF, and cosmological parameters. For a Salpeter IMF (x=2.35) we find that z_form>2.8 and Omega_m<0.86 with 95% confidence. The constraint on the formation redshift is weaker if Omega_Lambda>0: z_form>1.7 if Omega_m=0.3 and Omega_Lambda=0.7. At present the limiting factor in constraining z_form and Omega from the observed luminosity evolution of early-type galaxies is the poor understanding of the IMF. We find that if Omega_m=1 the IMF must be significantly steeper than the Salpeter IMF (x>2.6).Comment: To be published in ApJ Letters, Volume 504, September 1, 1998. 5 pages, 4 figure

Rupture of vesicourethral anastomosis following radical retropubic prostatectomy

OBJECTIVE: Rupture of vesicourethral anastomosis following radical retropubic prostatectomy is a complication that requires immediate management. We evaluated the morbidity of this rare complication. MATERIALS AND METHODS: We analyzed retrospectively 5 cases of disruption of vesicourethral anastomosis during post-operative period in a consecutive series of 1,600 radical retropubic prostatectomies, performed by a single surgeon. RESULTS: It occurred in a ratio of 1:320 prostatectomies (0,3%). Management was conservative in all the cases with an average catheter permanence time of 28 days, being its removal preceded by cystography. Two cases were secondary to bleeding, 1 followed the change of vesical catheter and 2 by unknown causes after removing the Foley catheter. Only one patient evolved with urethral stenosis, in the period ranging from 6 to 120 months. CONCLUSION: Rupture of vesicourethral anastomosis is not related to the surgeon's experience, and conservative treatment has shown to be effective.Universidade Federal de São Paulo (UNIFESP), Escola Paulista de Medicina (EPM) Department of UrologyUNIFESP, EPM, Department of UrologySciEL