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The ACS Virgo Cluster Survey. VII. Resolving the Connection between Globular Clusters and Ultracompact Dwarf Galaxies
NO>1Based on observations with the NASA/ESA Hubble Space Telescopeobtained at the Space Telescope Science Institute, which is operated bythe association of Universities for Research in Astronomy, Inc., underNASA contract NAS 5-26555.
| The Detailed Fundamental Plane of Two High-Redshift Clusters: MS 2053-04 at z=0.58 and MS 1054-03 at z=0.83
We study the fundamental plane relation in high-redshift clusters usinga sample of 26 galaxies in MS 2053-04 (z=0.583) and 22 galaxies in MS1054-03 (z=0.83). The zero point and scatter are compared to results forlower redshift clusters in order to trace evolutionary effects.Furthermore, our large sample enables us to investigate correlationsbetween residuals from the fundamental plane and other characteristicsof the galaxies, such as color, Hβ line strength, spatialdistribution, and mass. The observed scatter of the early-type galaxieswith σ>100 km s-1 around the fundamental plane is0.134 and 0.106 in logre for MS 2053-04 and MS 1054-03,respectively. The residuals from the fundamental plane of MS 2053-04 arecorrelated with residuals from the Hβ-σ relation, suggestingthat stellar populations are playing a role in shaping the fundamentalplane. The measured evolution in logM/L is influenced by selectioneffects, as galaxies with lower M/L in the Johnson B-band enter amagnitude-limited sample more easily. When we select high-massearly-type galaxies to avoid this bias, we findlogM/LB~-0.47z and a formation redshiftzform~2.95, similar to earlier results.
| The Fundamental Plane at z=1.27: First Calibration of the Mass Scale of Red Galaxies at Redshifts z>1
We present results on the fundamental plane of early-type galaxies inthe cluster RDCS J0848+4453 at z=1.27. Internal velocity dispersions ofthree K-selected early-type galaxies are determined from deep Keckspectra, using absorption lines in the rest-frame wavelength range3400-4000 Å. Structural parameters are determined from HubbleSpace Telescope NICMOS images. The galaxies show substantial offsetsfrom the fundamental plane of the nearby Coma Cluster, as expected frompassive evolution of their stellar populations. The offsets from thefundamental plane can be expressed as offsets in mass-to-light (M/L)ratio. The M/L ratios of the two most massive galaxies are consistentwith an extrapolation of results obtained for clusters at0.023 and R-K>5, and ourresults show that it is hazardous to use simple models for convertingluminosity to mass for these objects. The work presented here, andprevious mass measurements at lower redshift, can be considered firststeps to empirically disentangle luminosity and mass evolution at thehigh-mass end of the galaxy population, lifting an important degeneracyin the interpretation of evolution of the luminosity function.Based on observations with the NASA/ESA Hubble Space Telescope, obtainedat the Space Telescope Science Institute, which is operated by theAssociation of Universities for Research in Astronomy, Inc., under NASAcontract NAS 5-26555.Based on observations obtained at the W. M. Keck Observatory, which isoperated jointly by the California Institute of Technology and theUniversity of California.
| The early-type galaxy population in Abell 2218
We present high signal-to-noise, moderate-resolution spectroscopy of 48early-type members of the rich cluster Abell 2218 at z=0.18, taken withthe LDSS2 spectrograph on the 4.2-m William Herschel Telescope. Thissample both is larger and spans a wider galaxy luminosity range, down toMB*+1, than previous studies. In addition to the relatively large sizeof the sample, we have detailed morphological information from archivalHubble Space Telescope imaging for 20 of the galaxies. We combine themorphological, photometric, kinematic and line-strength information tocompare A2218 with similar samples drawn from local clusters and toidentify evolutionary changes between the samples which have occurredover the last ~3Gyr. The overall picture is one of little or noevolution in nearly all of the galaxy parameters. Zero-point offsets inthe Faber-Jackson, Mgb-σ and Fundamental Planerelations are all consistent with passively evolving stellarpopulations. The slopes of these relations have not changedsignificantly in the 3Gyr between A2218 and today. We do however find asignificant spread in the estimated luminosity-weighted ages of thestellar populations in the galaxies, based on line diagnostic diagrams.This age spread is seen in both the discy early-type galaxies (S0) andalso the ellipticals. We observe both ellipticals with a strongcontribution from a young stellar population and lenticulars dominatedby old stellar populations. On average, we find no evidence forsystematic differences between the populations of ellipticals andlenticulars. In both cases there appears to be little evidence fordifferences between the stellar populations of the two samples. Thispoints to a common formation epoch for the bulk of the stars in most ofthe early-type galaxies in A2218. This result can be reconciled with theclaims of rapid morphological evolution in distant clusters if thesuggested transformation from spirals to lenticulars does not involvesignificant new star formation.
| Ages and metallicities of globular clusters in NGC 4472
We have derived ages and metallicities from co-added spectra of 131globular clusters associated with the giant elliptical galaxy NGC 4472.Based upon a calibration with Galactic globular clusters, we find thatour sample of globular clusters in NGC 4472 span a metallicity range ofapproximately -1.6<=[Fe/H]<=0dex. There is evidence of a radialmetallicity gradient in the globular cluster system which is steeperthan that seen in the underlying starlight. Determination of theabsolute ages of the globular clusters is uncertain, but formally, themetal-poor population of globular clusters has an age of 14.5+/-4Gyr andthe metal-rich population is 13.8+/-6Gyr old. Monte Carlo simulationsindicate that the globular cluster populations present in these data areolder than 6Gyr at the 95per cent confidence level. We find that withinthe uncertainties, the globular clusters are old and coeval, implyingthat the bimodality seen in the broadband colours primarily reflectsmetallicity and not age differences.
| The Evolution of Early-Type Galaxies in Distant Clusters. II. Internal Kinematics of 55 Galaxies in the z=0.33 Cluster CL 1358+62
We define a large sample of galaxies for use in a study of thefundamental plane in the intermediate redshift cluster Cl 1358+62 atz=0.33. We have analyzed high-resolution spectra for 55 members of thecluster. The data were acquired with the Low-Resolution ImagingSpectrograph on the Keck I 10 m telescope. A new algorithm for measuringvelocity dispersions is presented and used to measure the internalkinematics of the galaxies. This algorithm has been tested against theFourier fitting method so that the data presented here can be comparedwith those measured previously in nearby galaxies. We have measuredcentral velocity dispersions suitable for use in a fundamental planeanalysis. The data have a high signal-to-noise ratio (S/N) and theresulting random errors on the dispersions are very low, typically lessthat 5%. Uncertainties due to mismatch of the stellar templates havebeen minimized through several tests, and the total systematic error isof order ~5%. Good seeing enabled us to measure velocity dispersionprofiles and rotation curves for most of the sample, and although alarge fraction of the galaxies display a high level of rotation, thegradients of the total second moment of the kinematics are all veryregular and similar to those in nearby galaxies. We conclude that thedata therefore can be reliably corrected for aperture size in a mannerconsistent with nearby galaxy samples. Based on observations obtained atthe W. M. Keck Observatory, which is operated jointly by the CaliforniaInstitute of Technology and the University of California.
| The Vienna-KPNO search for Doppler-imaging candidate stars. I. A catalog of stellar-activity indicators for 1058 late-type Hipparcos stars
We present the results from a spectroscopic Ca ii H&K survey of 1058late-type stars selected from a color-limited subsample of the Hipparcoscatalog. Out of these 1058 stars, 371 stars were found to showsignificant H&K emission, most of them previously unknown; 23% withstrong emission, 36% with moderate emission, and 41% with weak emission.These spectra are used to determine absolute H&K emission-linefluxes, radial velocities, and equivalent widths of theluminosity-sensitive Sr ii line at 4077 Ä. Red-wavelengthspectroscopic and Strömgren y photometric follow-up observations ofthe 371 stars with H&K emission are used to additionally determinethe absolute Hα -core flux, the lithium abundance from the Li i6708 Å equivalent width, the rotational velocity vsin i, theradial velocity, and the light variations and its periodicity. Thelatter is interpreted as the stellar rotation period due to aninhomogeneous surface brightness distribution. 156 stars were found withphotometric periods between 0.29 and 64 days, 11 additional systemsshowed quasi-periodic variations possibly in excess of ~50 days. Further54 stars had variations but no unique period was found, and four starswere essentially constant. Altogether, 170 new variable stars werediscovered. Additionally, we found 17 new SB1 (plus 16 new candidates)and 19 new SB2 systems, as well as one definite and two possible new SB3systems. Finally, we present a list of 21 stars that we think are mostsuitable candidates for a detailed study with the Doppler-imagingtechnique. Tables A1--A3 are only available in electronic form at theCDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or viahttp://cdsweb.u-strasbg.fr/Abstract.html
| Variable Radial Velocities Among Composite-Spectrum Binaries in the PG Catalog
Ferguson, Green, & Liebert (1984\markcite{FGL}; FGL) identified aset of stars from the PG catalog that are composite-spectrum binariesconsisting of a hot subdwarf star and a late-type (G-K) star. During twoseasons at Kitt Peak National Observatory (KPNO), we examined theFGL\markcite{FGL} sample for close binaries by searching for largeradial velocity changes among typically three or four differentobservations. Only one of the twelve stars sampled so far has shownsignificant radial velocity variations (greater than 3sigma ): DeltaV_max = 83+/- 11 km s(-1) for PG 1224+309. Two other stars showedmarginal velocity changes: PG 0825+428, with Delta V_max = 24+/- 16 kms(-1) (1.6sigma ), and PG 1210+429, with Delta V_max = 39+/- 29 km s(-1)(1.3sigma ). The other nine stars did not display variations larger than0.9sigma (Delta V_max ≲ 15 km s(-1) ). We have reclassified thecool components of these twelve FGL\markcite{FGL} stars and made newestimates of the fractional contributions of the cool components to thetotal flux in the wavelength interval 5320-6532 Angstroms, generallyfinding spectral types slightly earlier, and flux fractions less, thanfound by FGL\markcite{FGL}. Both of these effects lead to reviseddistances to the binaries, mostly larger than those estimated byFGL\markcite{FGL}. An interesting and unexpected result from this workis the discovery of several rapidly rotating secondary stars. Thesestars may be related to the wind-accretion induced rapidly rotatingstars (WIRRing stars) discussed by Jeffries & Stevens(1996)\markcite{js96}. At least two systems, PG 1309-078 and PG1502-103, have large positive mean radial velocities, possiblyindicating halo orbits. We also tabulate mean apparent velocities forthe hot subdwarfs, measured from the He I D_3 line (based on an adoptedwavelength of 5875.697 Angstroms) which may be useful in assessing thegravitational redshifts of these stars. Four of the hot subdwarfs didnot exhibit a measurable D_3 line.
| A sample of galaxy clusters to study the fundamental plane: Redshift measurements
We present the results of spectroscopic observations of galaxies in asample of nearby clusters. We measured galaxy redshifts and estimatedcluster velocity dispersions. These observations were carried out at theObservatoire de Haute Provence as part of a program aiming at a moredetailed study of the Cluster Fundamental Plane. Based on observationsmade at Haute-Provence Observatory, CNRS, France.
| The Tokyo PMC catalog 90-93: Catalog of positions of 6649 stars observed in 1990 through 1993 with Tokyo photoelectric meridian circle
The sixth annual catalog of the Tokyo Photoelectric Meridian Circle(PMC) is presented for 6649 stars which were observed at least two timesin January 1990 through March 1993. The mean positions of the starsobserved are given in the catalog at the corresponding mean epochs ofobservations of individual stars. The coordinates of the catalog arebased on the FK5 system, and referred to the equinox and equator ofJ2000.0. The mean local deviations of the observed positions from theFK5 catalog positions are constructed for the basic FK5 stars to comparewith those of the Tokyo PMC Catalog 89 and preliminary Hipparcos resultsof H30.
| Spectroscopic Orbits for Three Binaries with Low-Mass Companions and the Distribution of Secondary Masses near the Substellar Limit
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1996ApJ...466..415M&db_key=AST
| RW Comae Berenices. II - Spectroscopy
The 36 spectroscopic exposures obtained for the 0.24-day eclipsingbinary RW Com since 1977 have allowed the velocities and emissionbehavior of the components to be studied. This work arose from the needto obtain a mass ratio for synthetic light curve analysis which could inturn furnish system models for use in studies of the system's lightcurves. Radial velocities were determined by means of the crosscorrelation method, and a mass ratio m(2)/m(1) of 0.34 + or - 0.02 hasbeen obtained. Since star 2 is eclipsed at primary minimum, it isidentified as the less massive component.
| Narrow-band photometry of G and K stars near the North Galactic Pole
Photoelectric narrow-band photometry obtained for 292 late-type starsbrighter than 10 m in the North Galactic Pole area is discussed. The g,n, k, m, f-system of Dickow et al. (1970) is used. The stars were chosenfrom two lists: (1) all stars of spectral type G5 or later in the HenryDraper Catalog (Cannon and Pickering, 1918-1924) within 15 deg of theNorth Galactic Pole, together with a few BD stars; and (2) all starsclassified as K or M giants and in Upgren's 25-31 deg zones (Upgren,1962). For most of the stars, estimates of the following quantities arederived: V-magnitude, R-I color, metal abundance, MV, and theduplicity parameter res(k).
| Standard Velocity Stars
Not Available
| Photoelectric radial velocities, paper 6 Heard's IAU standard stars.
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1975MNRAS.171..407G&db_key=AST
| Spectral types and UBV photometry of G-K giants at the north galactic pole
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1973AJ.....78...37S&db_key=AST
| The establishment of 21 new ninth magnitude IAU standard radial velocity stars
Not Available
| The space distribution of late type stars in a North galactic pole region.
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1962AJ.....67...37U&db_key=AST
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| קבוצת-כוכבים: | אריה |
| התרוממות ימנית: | 11h47m56.36s |
| סירוב: | +27°20'26.2" |
| גודל גלוי: | 7.469 |
| מרחק: | 144.718 פארסק |
| תנועה נכונה: | -43.4 |
| תנועה נכונה: | 8.5 |
| B-T magnitude: | 8.603 |
| V-T magnitude: | 7.563 |
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