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Infrared Luminosity Function of the Coma Cluster
Using mid-IR and optical data, we deduce the total infrared (IR)luminosities of galaxies in the Coma Cluster and present their IRluminosity function (LF). The shape of the overall Coma IR LF does notshow significant differences from the IR LFs of the general field, whichindicates the general independence of global galaxy star formation fromenvironment up to densities ~40 times greater than in the field (wecannot test such independence above LIR~1044 ergss-1). However, a shallower faint-end slope and a smallerL*IR are found in the core region (where thedensities are still higher) compared to the outskirt region of thecluster, and most of the brightest IR galaxies are found outside thecore region. The IR LF in the NGC 4839 group region does not show anyunique characteristics. By integrating the IR LF, we find a total starformation rate in the cluster of about 97.0 Msolaryr-1. We also studied the contributions of early- andlate-type galaxies to the IR LF. The late-type galaxies dominate thebright end of the LF, and the early-type galaxies, although only makingup a small portion (~15%) of the total IR emission of the cluster,contribute greatly to the number counts of the LF atLIR<1043 ergs s-1.
| Study of the Structure of the Coma Cluster Based on a Hierarchical Force Clustering Method
Six subclusters in the Coma cluster have been selected on the basis of ahierarchical clustering method that takes the gravitational interactionamong galaxies into account. Of these, 3 central subclusters around thegalaxies NGC 4889, NGC 4874, and NGC 4839 have been singled out. We haveused the objective statistical criterion applied by Vennik and Anosovain studies of close groups of galaxies to evaluate each member includedin a subcluster with a high probability. Galaxies with a significantdeficit of hydrogen HI, including objects from the Bravo-Alfaro list,have been identified with members of the subclusters, with the greatestnumber of them in the subclusters around NGC 4874 and NGC 4839. Aquantitative estimate of the hydrogen deficit using the HI index in theRCG3 catalog reveals a statistically significant excess value for thosegalaxies that are members of the subclusters compared to galaxies with ahydrogen deficit in the overall Coma cluster field. A substantial numberof the spiral galaxies with a hydrogen deficit in the subclusters turnedout to be radio galaxies as well.
| Principal component analysis of International Ultraviolet Explorer galaxy spectra
We analyse the UV spectral energy distribution of a sample of normalgalaxies listed in the International Ultraviolet Explorer (IUE) NewlyExtracted Spectra (INES) Guide No. 2 - Normal Galaxies using a principalcomponent analysis. The sample consists of the IUE short-wavelength (SW)spectra of the central regions of 118 galaxies, where the IUE apertureincluded more than 1 per cent of the galaxy size. The principalcomponents are associated with the main components observed in theultraviolet (UV) spectra of galaxies. The first component, accountingfor the largest source of diversity, may be associated with the UVcontinuum emission. The second component represents the UV contributionof an underlying evolved stellar population. The third component issensitive to the amount of activity in the central regions of galaxiesand measures the strength of star-formation events.In all the samples analysed here, the principal component representativeof star-forming activity accounts for a significant percentage of thevariance. The fractional contribution to the spectral energydistribution (SED) by the evolved stars and by the young population aresimilar.Projecting the SEDs on to their eigenspectra, we find that none of thecoefficients of the principal components can outline an internalcorrelation or can correlate with the optical morphological types. In asubsample of 43 galaxies, consisting of almost only compact and BCDgalaxies, the third principal component defines a sequence related tothe degree of starburst activity of the galaxy.
| Radio and Far-Infrared Emission as Tracers of Star Formation and Active Galactic Nuclei in Nearby Cluster Galaxies
We have studied the radio and far-infrared (FIR) emission from 114galaxies in the seven nearest clusters (<100 Mpc) with prominentX-ray emission to investigate the impact of the cluster environment onthe star formation and active galactic nucleus (AGN) activity in themember galaxies. The X-ray selection criterion is adopted to focus onthe most massive and dynamically relaxed clusters. A large majority ofcluster galaxies show an excess in radio emission over that predictedfrom the radio-FIR correlation, the fraction of sources with radioexcess increases toward cluster cores, and the radial gradient in theFIR/radio flux ratio is a result of radio enhancement. Of theradio-excess sources, 70% are early-type galaxies, and the same fractionhost an AGN. The galaxy density drops by a factor of 10 from thecomposite cluster center out to 1.5 Mpc, yet galaxies show no change inFIR properties over this region and show no indication of masssegregation. We have examined in detail the physical mechanisms thatmight impact the FIR and radio emission of cluster galaxies. Whilecollisional heating of dust may be important for galaxies in clustercenters, it appears to have a negligible effect on the observed FIRemission for our sample galaxies. The correlations between radio and FIRluminosity and radius could be explained by magnetic compression fromthermal intracluster medium pressure. We also find that simple delayedharassment cannot fully account for the observed radio, FIR, and mid-IRproperties of cluster galaxies.
| UV and FIR selected samples of galaxies in the local Universe. Dust extinction and star formation rates
We have built two samples of galaxies selected at 0.2 μm (hereafterUV) and 60 μm (hereafter FIR) covering a sky area of 35.36deg2. The UV selected sample contains 25 galaxies brighterthan AB0.2=17. All of them, but one elliptical, are detectedat 60 μm with a flux density larger or equal to 0.2 Jy. The UV countsare significantly lower than the Euclidean extrapolation towardsbrighter fluxes of previous determinations. The FIR selected samplecontains 42 galaxies brighter than f60=0.6 Jy. Except fourgalaxies, all of them have a UV counterpart at the limiting magnitudeAB0.2=20.3 mag. The mean extinction derived from the analysisof the FIR to UV flux ratio is 1 mag for the UV selected sample and2 mag for the FIR selected one. For each sample we compare severalindicators of the recent star formation rate (SFR) based on the FIRand/or the UV emissions. We find linear relationships with slopes closeto unity between the different SFR indicator, which means that, over thewhole converting offset. Various absolute calibrations for both samplesare discussed in this paper. A positive correlation between extinctionand SFR is found when both samples are considered together although witha considerable scatter. A similar result is obtained when using the SFRnormalized to the optical surface of the galaxies.Tables 3, 4 and Fig. 1 are only available in electronic form athttp://www.edpsciences.org
| The X-ray luminosity function of galaxies in the Coma cluster
The XMM-Newton survey of the Coma cluster of galaxies covers an area of1.86 square degrees with a mosaic of 16 pointings and has a total usefulintegration time of 400 ks. Detected X-ray sources with extent less than10'' were correlated with cataloged galaxies in the Comacluster region. The redshift information, which is abundant in thisregion of the sky, allowed us to separate cluster members frombackground and foreground galaxies. For the background sources, werecover a typical Log N-Log S in the flux range10-15-10-13 ergs s-1 cm-2 inthe 0.5-2.0 keV band. The X-ray emission from the cluster galaxiesexhibits X-ray colors typical of thermal emission. The luminosities ofComa galaxies lie in the 1039-1041 ergss-1 interval in the 0.5-2.0 keV band. The luminosity functionof Coma galaxies reveals that their X-ray activity is suppressed withrespect to the field by a factor of 5.6, indicating a lower level ofX-ray emission for a given stellar mass.
| The impact of high pressure cluster environment on the X-ray luminosity of Coma early-type galaxies
We present an observational study of the LX vs. LBσ2 relation for early-type galaxies in the Coma clusterbased on the XMM-Newton survey data. Compared to a similar relation fora sample dominated by field early-type galaxies, the Coma clustergalaxies show a flatter slope. Our calculations show that adiabaticcompression produces a flattening in the LX vs.LBσ2 relation that is in remarkableagreement with the observed effect. Our scenario is further supported bythe observed compactness of the X-ray emission of Coma galaxies.
| Radio emission from AGN detected by the VLA FIRST survey
Using the most recent (April 2003) version of the VLA FIRST survey radiocatalog, we have searched for radio emission from >2800 AGN takenfrom the most recent (2001) version of the Veron-Cetty and Veron AGNcatalog. These AGN lie in the 9033 square degrees of sky alreadycovered by the VLA FIRST survey. Our work has resulted in positivedetection of radio emission from 775 AGN of which 214 are new detectionsat radio wavelengths.Tables 3 and 4 are only available in electronic form at the CDS viaanonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or viahttp://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/416/35
| A new catalogue of ISM content of normal galaxies
We have compiled a catalogue of the gas content for a sample of 1916galaxies, considered to be a fair representation of ``normality''. Thedefinition of a ``normal'' galaxy adopted in this work implies that wehave purposely excluded from the catalogue galaxies having distortedmorphology (such as interaction bridges, tails or lopsidedness) and/orany signature of peculiar kinematics (such as polar rings,counterrotating disks or other decoupled components). In contrast, wehave included systems hosting active galactic nuclei (AGN) in thecatalogue. This catalogue revises previous compendia on the ISM contentof galaxies published by \citet{bregman} and \citet{casoli}, andcompiles data available in the literature from several small samples ofgalaxies. Masses for warm dust, atomic and molecular gas, as well asX-ray luminosities have been converted to a uniform distance scale takenfrom the Catalogue of Principal Galaxies (PGC). We have used twodifferent normalization factors to explore the variation of the gascontent along the Hubble sequence: the blue luminosity (LB)and the square of linear diameter (D225). Ourcatalogue significantly improves the statistics of previous referencecatalogues and can be used in future studies to define a template ISMcontent for ``normal'' galaxies along the Hubble sequence. The cataloguecan be accessed on-line and is also available at the Centre desDonnées Stellaires (CDS).The catalogue is available in electronic form athttp://dipastro.pd.astro.it/galletta/ismcat and at the CDS via anonymousftp to\ cdsarc.u-strasbg.fr (130.79.128.5) or via\http://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/405/5
| Spectroscopic study of blue compact galaxies. III. Empirical population synthesis
This is the third paper of a series dedicated to the study of the starformation rates, star formation histories, metallicities and dustcontents of a sample of blue compact galaxies (BCGs). We constrain thestellar contents of 73 blue compact galaxies by analyzing theircontinuum spectra and the equivalent widths of strong stellar absorptionfeatures using a technique of empirical population synthesis based on alibrary of observed star-cluster spectra. Our results indicate that bluecompact galaxies are typically age-composite stellar systems; inaddition to young stars, intermediate-age and old stars contributesignificantly to the 5870 Å continuum emission of most galaxies inour sample. The stellar populations of blue compact galaxies also span avariety of metallicities. The ongoing episodes of star formation startedtypically less than a billion years ago. Some galaxies may be undergoingtheir first global episode of star formation, while for most galaxies inour sample, older stars are found to contribute up to half the opticalemission. Our results suggest that BCGs are primarily old galaxies withdiscontinuous star formation histories. These results are consistentwith the results from deep imaging observations of the color-magnitudediagrams of a few nearby BCGs using HST and large ground-basedtelescopes. The good quality of our population synthesis fits of BCGspectra allow us to estimate the contamination of the Hβox{Hα }, Hβ , Hγ and Hdelta Balmer emission lines bystellar absorption. The absorption equivalent widths measured in thesynthetic spectra range from typically 1.5 Å for Hβox{Hα }, to 2-5 Å for Hβ , Hγ , and Hdelta . Theimplied accurate measurements of emission-line intensities will be usedin a later study to constrain the star formation rates and gas-phasechemical element abundances of blue compact galaxies.
| Stellar populations in early-type Coma cluster galaxies - I. The data
We present a homogeneous and high signal-to-noise ratio data set (meanS/N ratio of ~60 Å-1) of Lick/IDS stellar populationline indices and central velocity dispersions for a sample of 132 bright(bj<= 18.0) galaxies within the central 1°(≡1.26h-1 Mpc) of the nearby rich Coma cluster (A1656). Ourobservations include 73 per cent (100 out of 137) of the totalearly-type galaxy population (bj<= 18.0). Observationswere made with the William Herschel 4.2-m telescope and theAUTOFIB2/WYFFOS multi-object spectroscopy instrument (resolution of~2.2-Å FWHM) using 2.7-arcsec diameter fibres (≡0.94h-1 kpc). The data in this paper have well-characterizederrors, calculated in a rigorous and statistical way. Data are comparedwith previous studies and are demonstrated to be of high quality andwell calibrated on to the Lick/IDS system. Our data have median errorsof ~0.1 Å for atomic line indices, ~0.008 mag for molecular lineindices and 0.015 dex for velocity dispersions. This work provides awell-defined, high-quality baseline at z~ 0 for studies of medium- tohigh-redshift clusters. Subsequent papers will use this data set toprobe the stellar populations (which act as fossil records of galaxyformation and evolution) and the spectrophotometric relations of thebright early-type galaxies within the core of the Coma cluster.
| A New Database of Observed Spectral Energy Distributions of Nearby Starburst Galaxies from the Ultraviolet to the Far-Infrared
We present a database of UV-to-FIR data of 83 nearby starburst galaxies.The galaxies are selected based upon the availability of IUE data. Wehave recalibrated the IUE UV spectra for these galaxies by incorporatingthe most recent improvements. For 45 of these galaxies we useobservations by Storchi-Bergmann et al. and McQuade et al. for thespectra in the optical range. The NIR data are from new observationsobtained at the NASA/IRTF and the Mount Laguna Observatory, combinedwith the published results from observations at the Kitt Peak NationalObservatory. In addition, published calibrated ISO data are included toprovide mid-IR flux densities for some of the galaxies. Theoptical-to-IR data are matched as closely as possible to the IUE largeaperture. In conjunction with IRAS and ISO FIR flux densities, all thesedata form a set of observed spectral energy distributions (SEDs) of thenuclear regions of nearby starburst galaxies. The SEDs should be usefulin studying star formation and dust/gas attenuation in galaxies. We alsopresent the magnitudes in the standard BVRI and various HST/WFPC2bandpasses synthesized from the UV and optical wavelength ranges ofthese SEDs. For some of the galaxies, the HST/WFPC2 magnitudessynthesized from the SEDs are checked with those directly measured fromWFPC2 images to test the photometric errors of the optical data andtheir effective matching of apertures with the UV data. The implicationsof the new SEDs on the star formation rates and dust/gas attenuation arebriefly discussed.
| Evolution of Star-forming and Active Galaxies in Nearby Clusters
We have used optical spectroscopy to investigate the active galaxypopulations in a sample of 20 nearby Abell clusters. The targets wereidentified on the basis of 1.4 GHz radio emission, which identifies themas either active galactic nuclei (AGNs) or galaxies forming stars atrates comparable to or greater than that of the Milky Way. The spectrawere used to characterize the galaxies via their emission and absorptionfeatures. The spectroscopy results reveal a significant population ofstar-forming galaxies with large amounts of nuclear dust extinction.This extinction eliminates bluer emission lines such as [O II] from thespectra of these galaxies, meaning their star formation could easily beoverlooked in studies that focus on such features. Around 20% of thecluster star-forming galaxies have spectra of this type. The radialdistributions of active galaxies in clusters show a strong segregationbetween star-forming galaxies and AGNs, with star-forming galaxiesbroadly distributed and AGNs preferentially in the cluster cores. Theradial distribution of the dusty star-forming galaxies is more centrallyconcentrated than the star-forming galaxies in general, which arguesthat they are a consequence of some cluster environmental effect.Furthermore, we note that such galaxies may be identified using their4000 Å break strengths. We find that discrepancies in reportedradio luminosity functions for AGNs are likely the result ofclassification differences. There exists a large population of clustergalaxies whose radio fluxes, far-infrared fluxes, and optical magnitudessuggest their radio emission may be powered by stars yet whose spectralack emission lines. Understanding the nature of these galaxies iscritical to assessing the importance of AGNs in the radio luminosityfunction at low luminosities. We also find that regardless of thispopulation, the crossover point where the radio luminosity function iscomposed equally of star-forming galaxies and AGNs occurs at lowerluminosities in clusters than in the field. This is likely a simpleconsequence of the reduction in star formation in cluster galaxies andthe morphological mix in clusters compared with the field.Based in part on observations obtained with the Apache Point Observatory(APO) 3.5 m telescope, which is owned and operated by the AstrophysicalResearch Consortium.
| The UZC-SSRS2 Group Catalog
We apply a friends-of-friends algorithm to the combined Updated ZwickyCatalog and Southern Sky Redshift Survey to construct a catalog of 1168groups of galaxies; 411 of these groups have five or more members withinthe redshift survey. The group catalog covers 4.69 sr, and all groupsexceed the number density contrast threshold, δρ/ρ=80. Wedemonstrate that the groups catalog is homogeneous across the twounderlying redshift surveys; the catalog of groups and their membersthus provides a basis for other statistical studies of the large-scaledistribution of groups and their physical properties. The medianphysical properties of the groups are similar to those for groupsderived from independent surveys, including the ESO Key Programme andthe Las Campanas Redshift Survey. We include tables of groups and theirmembers.
| The far-ultraviolet emission of early-type galaxies
We have assembled a UV-flux selected sample of 82 early-type galaxiesand collected additional information at other wavelengths. These dataconfirm a large spread of the UV-V color in the range 2 to 5. The spreadin UV-V is accompanied by a spread in B-V that is mainly attributed tothe range of morphological types and luminosities. A large fraction ofthe objects have red colors, UV-V = 4 +/- 0.4, corresponding to a weakUV-upturn as observed with IUE. If the current interpretation for the UVemission from early-type galaxies is applicable to our sample, the PAGB(Post-Asymptotic Giant Branch) tracks are the most common evolution pathfor the low-mass stars responsible for the UV emission. A small numberof very blue (UV-V < 1.4) objects have been found that can bereasonably interpreted as harbouring some low level of star formation.In contrast to a previous sample based on IUE observations, nocorrelation is found between the UV-V color and the Mg2spectral line index; possible explanations are reviewed. The potentialof a more extended UV survey like GALEX is briefly presented.
| Spectroscopic study of blue compact galaxies. I. The spectra
Blue compact galaxies are compact objects that are dominated by intensestar formation. Most of them have dramatically different propertiescompared to the Milky Way and many other nearby galaxies. Using theIRAS, H I data, and optical spectra, we wanted to measure the currentstar formation rates, stellar components, metallicities, and starformation histories and evolution of a large blue compact galaxy sample.We anticipate that our study will be useful as a benchmark for studiesof emission line galaxies at high redshift. In the first paper of thisseries, we describe the selection, spectroscopic observation, datareduction and calibration, and spectrophotometric accuracy of a sampleof 97 luminous blue compact galaxies. We present a spectrophotometricatlas of rest-frame spectra, as well as tables of the recessionvelocities and the signal-to-noise ratios. The recession velocities ofthese galaxies are measured with an accuracy of delta V< 67 kms-1. The average signal-to-noise ratio of sample spectra is ~51. The spectral line strengths, equivalent widths and continuum fluxesare also measured for the same galaxies and will be analyzed in the nextpaper of this series. The atlas and tables of measurements will be madeavailable electronically. Table 3 and Fig. 4 are only available inelectronic form at the CDS via anonymous ftp to cdsarc.u-strasbg.fr(130.79.128.5) or viahttp://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/389/845
| The colour-magnitude relation for galaxies in the Coma cluster
We present a new photometric catalogue of the Coma galaxy cluster in theJohnson U and V bands. We cover an area of 3360arcmin2 ofsky, to a depth of \fontshape{it}{V}=20\hphantom{0} mag in a13-arcsec diameter aperture, and produce magnitudes for ~1400 extendedobjects in metric apertures from 8.8- to 26-arcsec diameters. The meaninternal rms scatter in the photometry is 0.014mag in V, and 0.026mag inU, for \fontshape{it}{V}13<17\hphantom{0}mag.We place new limits on the levels of scatter in the colour-magnituderelation (CMR) in the Coma cluster, and investigate how the slope andscatter of the CMR depend on galaxy morphology, luminosity and positionwithin the cluster. As expected, the lowest levels of scatter are foundin the elliptical galaxies, while the late-type galaxies have thehighest numbers of galaxies bluewards of the CMR. We investigate whetherthe slope of the CMR is an artefact of colour gradients within galaxies,and show that it persists when the colours are measured within adiameter that scales with galaxy size. Looking at the environmentaldependence of the CMR, we find a trend of systematically bluer galaxycolours with increasing projected radius from the centre of the cluster.Surprisingly, this is accompanied by a decreased scatter of the CMR. Weinvestigate whether this gradient could be caused by dust in the clusterpotential, however the reddening required would produce too large ascatter in the colours of the central galaxies. The gradient appears tobe better reproduced by a gradient in the mean galactic ages withprojected radius.
| The Radio Galaxy Populations of Nearby Northern Abell Clusters
We report on the use of the NRAO VLA Sky Survey (NVSS) to identify radiogalaxies in 18 nearby Abell clusters. The listings extend from the coresof the clusters out to radii of 3 h-175 Mpc, whichcorresponds to 1.5 Abell radii and approximately 4 orders of magnitudein galaxy density. To create a truly useful catalog, we have collectedoptical spectra for nearly all of the galaxies lacking public velocitymeasurements. Consequently, we are able to discriminate between thoseradio galaxies seen in projection on the cluster and those that are inactuality cluster members. The resulting catalog consists of 329 clusterradio galaxies plus 138 galaxies deemed foreground or backgroundobjects, and new velocity measurements are reported for 273 of theseradio galaxies. The motivation for the catalog is the study of galaxyevolution in the cluster environment. The radio luminosity function is apowerful tool in the identification of active galaxies, as it isdominated by star-forming galaxies at intermediate luminosities andactive galactic nuclei (AGNs) at higher luminosities. The flux limit ofthe NVSS allows us to identify AGNs and star-forming galaxies down tostar formation rates less than 1 Msolar yr-1. Thissensitivity, coupled with the all-sky nature of the NVSS, allows us toproduce a catalog of considerable depth and breadth. In addition tothese data, we report detected infrared fluxes and upper limits obtainedfrom IRAS data. It is hoped that this database will prove useful in anumber of potential studies of the effect of environment on galaxyevolution. Based in part on observations obtained with the Apache PointObservatory 3.5 m telescope, which is owned and operated by theAstrophysical Research Consortium (ARC).
| The Spatial Distribution and Kinematics of Stellar Populations in E+A Galaxies
We use long-slit spectroscopic observations of the sample of E+Agalaxies described by Zabludoff et al. to constrain the nature of theprogenitors and remnants of the E+A phase of galaxy evolution. Wemeasure spatially resolved kinematic properties of the young (<~1Gyr) and old (>~few Gyr) stellar populations. The young stellarpopulations are more centrally concentrated than the older populations,but they are not confined to the galaxy core (radius <~1 kpc). Thekinematics of the old stellar population place 16 of 20 of our E+As on atrend parallel to the Faber-Jackson relation that is offset by ~0.6 magin R. Eighteen of 20 E+As have v/σ<1. As the young stars inthese systems evolve, the luminosity offset will disappear, and theremnants will be pressure-supported systems that lie on theFaber-Jackson relation. Although Zabludoff et al. spectroscopicallyselected the most extreme E+A galaxies in the local volume, the sampleis kinematically diverse: velocity dispersions range from <~30 kms-1 to ~200 km s-1 over a luminosity range ofMR=-19 to -22+5logh. Combining these results with an estimateof the number of galaxies that experience an E+A phase, we conclude thatthe E+A phase of galaxy evolution is important in the development of alarge fraction of spheroid-dominated galaxies over a wide range ofluminosities and masses. Our kinematic observations, together withevidence that E+As have recently evolved from a vigorous star-formingphase to a quiescent phase (e.g., Couch & Sharples; Caldwell et al.)and that many have tidal features consistent with disklike progenitors(Zabludoff et al.), indicate that these galaxies are undergoing atransformation from gas-rich, star-forming, rotationally supported,disk-dominated galaxies into gas-poor, quiescent, pressure-supported,spheroid-dominated galaxies.
| The First Hour of Extragalactic Data of the Sloan Digital Sky Survey Spectroscopic Commissioning: The Coma Cluster
On 1999 May 26, one of the Sloan Digital Sky Survey (SDSS) fiber-fedspectrographs saw astronomical first light. This was followed by thefirst spectroscopic commissioning run during the dark period of 1999June. We present here the first hour of extragalactic spectroscopy takenduring these early commissioning stages: an observation of the Comacluster of galaxies. Our data samples the southern part of this cluster,out to a radius of 1.5d (1.8 h-1 Mpc, approximately to thevirial radius) and thus fully covers the NGC 4839 group. We outline inthis paper the main characteristics of the SDSS spectroscopic systemsand provide redshifts and spectral classifications for 196 Comagalaxies, of which 45 redshifts are new. For the 151 galaxies in commonwith the literature, we find excellent agreement between our redshiftdeterminations and the published values, e.g., for the largesthomogeneous sample of galaxies in common (63 galaxies observed byColless & Dunn) we find a mean offset of 3 km s -1 and anrms scatter of only 24 km s -1. As part of our analysis, wehave investigated four different spectral classification algorithms:measurements of the spectral line strengths, a principal componentdecomposition, a wavelet analysis and the fitting of spectral synthesismodels to the data. We find that these classification schemes are inbroad agreement and can provide physical insight into the evolutionaryhistories of our cluster galaxies. We find that a significant fraction(25%) of our observed Coma galaxies show signs of recent star formationactivity and that the velocity dispersion of these active galaxies(emission-line and poststarburst galaxies) is 30% larger than theabsorption-line galaxies. We also find no active galaxies within thecentral (projected) 200 h-1 kpc of the cluster. The spatialdistribution of our Coma active galaxies is consistent with that foundat higher redshift for the CNOC1 cluster survey. Beyond the core region,the fraction of bright active galaxies appears to rise slowly out to thevirial radius and are randomly distributed within the cluster with noapparent correlation with the potential merger or postmerger of the NGC4839 group. We briefly discuss possible origins of this recent galaxystar formation.
| VLA HI Imaging of the brightest spiral galaxies in Coma. II. The HI Atlas and deep continuum imaging of selected early type galaxies
In the first paper of this series we used HI observations of the 19brightest spirals in Coma to analyze the dynamical state of the cluster.In this paper we present the detailed HI distribution and kinematics ofthe spirals that were detected in HI, and radio continuum data for asample of star forming and post starburst galaxies in Coma. We discussthe importance of ICM-ISM interactions to explain the observed HImorphology. A rough comparison of observed HI sizes with predicted HIsizes from simulations by Abadi et al. (\cite{Abadi99}) gives reasonableagreement. We use the results on radio continuum emission to estimatethe star formation rate in the PSB galaxies we pointed at. The radiocontinuum emission in the 11 so called post starburst galaxies,identified by Caldwell et al. (\cite{Caldwell93}) in the cluster, isweak. Eight of the 11 were not detected down to a 3 sigma upper limit of0.6 mJy. This sets an upper limit to the star formation rate in thesegalaxies of less than 0.2 Msun,yr-1. The threedetected post starburst galaxies have a star formation rate of less thanone solar mass per year. Thus none of the post starburst galaxies inComa are dust enshrouded starbursts. Appendix is only available inelectronic form at http://www.edpsciences.org
| VLA H I Imaging of the Brightest Spiral Galaxies in Coma
We have obtained 21 cm images of 19 spiral galaxies in the Coma cluster,using the VLA in its C and D configurations. The sample selection wasbased on morphology, brightness, and optical diameters of galaxieswithin one Abell radius (1.2d). The H I-detected, yet deficient galaxiesshow a strong correlation in their H I properties with projecteddistance from the cluster center. The most strongly H I-deficient(DefH I>0.4) galaxies are located inside a radius of 30'(~0.6 Mpc) from the center of Coma, roughly the extent of the centralX-ray emission. These central galaxies show clear asymmetries in their HI distribution and/or shifts between the optical and 21 cm positions.Another 12 spirals were not detected in H I with typical H I mass upperlimits of 108 Msolar. Seven of the 12nondetections are located in the central region of Coma, roughly within30' from the center. The other nondetections are to the east andsouthwest of the center. We looked for seven so-called blue diskgalaxies in Coma in H I and detected six. These galaxies are relativelyclose to the central region of Coma. The nondetected one is the closestto the center. The six detected blue galaxies are mildly H I deficient.We did a more sensitive search for H I from 11 of the 15 knownpoststarburst galaxies in Coma. None were detected with typical H I masslimits between 3 and 7x107 Msolar. Our resultspresent and enhance a picture already familiar for well-studiedclusters. H I poor galaxies (deficient ones and nondetections) areconcentrated toward the center of the cluster. The H I morphology of thecentral galaxies with optical disks extending beyond the H I disks isunique to cluster environments and strongly suggests an interaction withthe intergalactic medium (IGM). A new result in Coma is the clumpydistribution of gas deficiency. In the cluster center the deficientgalaxies are to the east while the nondetections are to the west. In theouter parts the gas rich galaxies are north of Coma, nondetected spiralsare found in the NGC 4944 group to the east, and the NGC 4839 group isto the southwest. This supports recent findings that merging of groupsis ongoing in the center of Coma, farther out the NGC 4944 and NGC 4839must have passed at least once through the core, and the galaxies to thenorth have yet to fall in.
| 1.65 μm (H-band) surface photometry of galaxies. III. observations of 558 galaxies with the TIRGO 1.5 m telescope
We present near-infrared H-band (1.65 μm ) surface photometry of 558galaxies in the Coma Supercluster and in the Virgo cluster. This dataset, obtained with the Arcetri NICMOS3 camera ARNICA mounted on theGornergrat Infrared Telescope, is aimed at complementing, withobservations of mostly early-type objects, our NIR survey of spiralgalaxies in these regions, presented in previous papers of this series.Magnitudes at the optical radius, total magnitudes, isophotal radii andlight concentration indices are derived. We confirm the existence of apositive correlation between the near-infrared concentration index andthe galaxy H-band luminosity Based on observations taken at TIRGO(Gornergrat, Switzerland). TIRGO is operated by CAISMI-CNR, Arcetri,Firenze, Italy. Tables 1 and 2 are only available in electronic form atthe CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or viahttp://cdsweb.u-strasbg.fr/Abstract.html
| 1.65 μm (H-band) surface photometry of galaxies. V. Profile decomposition of 1157 galaxies
We present near-infrared H-band (1.65 μm) surface brightness profiledecomposition for 1157 galaxies in five nearby clusters of galaxies:Coma, A1367, Virgo, A262 and Cancer, and in the bridge between Coma andA1367 in the ``Great Wall". The optically selected (mpg≤16.0) sample is representative of all Hubble types, from E to Irr+BCD,except dE and of significantly different environments, spanning fromisolated regions to rich clusters of galaxies. We model the surfacebrightness profiles with a de Vaucouleurs r1/4 law (dV), withan exponential disk law (E), or with a combination of the two (B+D).From the fitted quantities we derive the H band effective surfacebrightness (μe) and radius (re) of each component, theasymptotic magnitude HT and the light concentration indexC31. We find that: i) Less than 50% of the Ellipticalgalaxies have pure dV profiles. The majority of E to Sb galaxies is bestrepresented by a B+D profile. All Scd to BCD galaxies have pureexponential profiles. ii) The type of decomposition is a strong functionof the total H band luminosity (mass), independent of the Hubbleclassification: the fraction of pure exponential decompositionsdecreases with increasing luminosity, that of B+D increases withluminosity. Pure dV profiles are absent in the low luminosity rangeLH<1010 L\odot and become dominantabove 1011 L\odot . Based on observations taken atTIRGO, Gornergrat, Switzerland (operated by CAISMI-CNR, Arcetri,Firenze, Italy) and at the Calar Alto Observatory (operated by theMax-Planck-Institut für Astronomie (Heidelberg) jointly with theSpanish National Commission for Astronomy). Table 2 and Figs. 2, 3, 4are available in their entirety only in electronic form at the CDS viaanonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or viahttp://cdsweb.u-strasbg.fr/Abstract.html
| Stellar population synthesis for blue compact galaxies.
Not Available
| The QDOT all-sky IRAS galaxy redshift survey
We describe the construction of the QDOT survey, which is publiclyavailable from an anonymous FTP account. The catalogue consists ofinfrared properties and redshifts of an all-sky sample of 2387 IRASgalaxies brighter than the IRAS PSC 60-μm completeness limit(S_60>0.6Jy), sparsely sampled at a rate of one-in-six. At |b|>10deg, after removing a small number of Galactic sources, the redshiftcompleteness is better than 98per cent (2086/2127). New redshifts for1401 IRAS sources were obtained to complete the catalogue; themeasurement and reduction of these are described, and the new redshiftstabulated here. We also tabulate all sources at |b|>10 deg with noredshift so far, and sources with conflicting alternative redshiftseither from our own work, or from published velocities. A list of 95ultraluminous galaxies (i.e. with L_60μm>10^12 L_solar) is alsoprovided. Of these, ~20per cent are AGN of some kind; the broad-lineobjects typically show strong Feii emission. Since the publication ofthe first QDOT papers, there have been several hundred velocity changes:some velocities are new, some QDOT velocities have been replaced by moreaccurate values, and some errors have been corrected. We also present anew analysis of the accuracy and linearity of IRAS 60-μm fluxes. Wefind that the flux uncertainties are well described by a combination of0.05-Jy fixed size uncertainty and 8per cent fractional uncertainty.This is not enough to cause the large Malmquist-type errors in the rateof evolution postulated by Fisher et al. We do, however, find marginalevidence for non-linearity in the PSC 60-μm flux scale, in the sensethat faint sources may have fluxes overestimated by about 5per centcompared with bright sources. We update some of the previous scientificanalyses to assess the changes. The main new results are as follows. (1)The luminosity function is very well determined overall but is uncertainby a factor of several at the very highest luminosities(L_60μm>5x10^12L_solar), as this is where the remainingunidentified objects are almost certainly concentrated. (2) Thebest-fitting rate of evolution is somewhat lower than our previousestimate; expressed as pure density evolution with density varying as(1+z)^p, we find p=5.6+/-2.3. Making a rough correction for the possible(but very uncertain) non-linearity of fluxes, we find p=4.5+/-2.3. (3)The dipole amplitude decreases a little, and the implied value of thedensity parameter, assuming that IRAS galaxies trace the mass, isΩ=0.9(+0.45, -0.25). (4) Finally, the estimate of density varianceon large scales changes negligibly, still indicating a significantdiscrepancy from the predictions of simple cold dark matter cosmogonies.
| E and S0 galaxies in the central part of the Coma cluster: ages, metal abundances and dark matter
Mean ages and metal abundances are estimated for the stellar populationsin a sample of 115 E and S0 galaxies in the central 64 arcmin × 70arcmin of the Coma cluster. The estimates are based on the absorptionline indices Mg2, and HβG, and themass-to-light ratios (M/L). Single stellar population models fromVazdekis et al. were used to transform from the measured line indicesand M/L ratios to mean ages and mean metal abundances ([Mg/H] and[Fe/H]). The non-solar abundance ratios [Mg/Fe] were taken into accountby assuming that for a given age and iron abundance, a [Mg/Fe] differentfrom solar will affect the Mg2 index but not the M/L ratio orthe and HβG indices. The derived ages andabundances are the luminosity-weighted mean values for the stellarpopulations in the galaxies.By comparing the mean ages derived from theMg2-HβG diagram with those derived from theMg2-M/L diagram, we estimate the variations of the fractionof dark matter. Alternatively, the difference between the two estimatesof the mean age may be caused by variations in the initial mass functionor any non-homology of the galaxies.The distributions of the derived mean ages and abundances show thatthere are real variations in both the mean ages and the abundances. Wefind an intrinsic rms scatter of [Mg/H], [Fe/H] and [Mg/Fe] of 0.2 dex,and an intrinsic rms scatter of the derived ages of 0.17 dex. Themagnesium abundances [Mg/H] and the abundance ratios [Mg/Fe] are bothstrongly correlated with the central velocity dispersions of thegalaxies, while the iron abundances [Fe/H] are uncorrelated with thevelocity dispersions. Further, [Mg/H] and [Fe/H] are stronglyanticorrelated with the mean ages of the galaxies. This is not the casefor [Mg/Fe].We have tested whether the slopes of the scaling relations between theglobal parameters for the galaxies (the Mg2-σ relation,the -σ relation, the HβG-σrelation and the Fundamental Plane) are consistent with the relationbetween the ages, the abundances and the velocity dispersions. We findthat all the slopes, except the slope of the Fundamental Plane, can beexplained in a consistent way as resulting from a combination betweenvariations of the mean ages and the mean abundances as functions of thevelocity dispersions. The slope of the Fundamental Plane is `steeper'than predicted from the variations in the ages and abundances.Because of the correlation between the mean ages and the meanabundances, substantial variations in the ages and the abundances arepossible while maintaining a low scatter of all the scaling relations.When this correlation is taken into account, the observed scatter of thescaling relations is consistent with the rms scatter in the derived agesand abundances at a given velocity dispersion.
| Arcsecond Positions of UGC Galaxies
We present accurate B1950 and J2000 positions for all confirmed galaxiesin the Uppsala General Catalog (UGC). The positions were measuredvisually from Digitized Sky Survey images with rms uncertaintiesσ<=[(1.2")2+(θ/100)2]1/2,where θ is the major-axis diameter. We compared each galaxymeasured with the original UGC description to ensure high reliability.The full position list is available in the electronic version only.
| Dust Absorption and the Ultraviolet Luminosity Density at Z~3 as Calibrated by Local Starburst Galaxies
We refine a technique to measure the absorption-corrected ultraviolet(UV) luminosity of starburst galaxies using rest-frame UV quantitiesalone and apply it to Lyman-limit U dropouts at z~3 found in the HubbleDeep Field (HDF). The method is based on an observed correlation betweenthe ratio of far-infrared (FIR) to UV fluxes with spectral slope beta (aUV color). A simple fit to this relation allows the UV flux absorbed bydust and reprocessed to the FIR to be calculated, and hence thedust-free UV luminosity to be determined. International UltravioletExplorer spectra and Infrared Astronomical Satellite fluxes of localstarbursts are used to calibrate the F_FIR/F_1600 versus beta relationin terms of A_1600 (the dust absorption at 1600 Å) and thetransformation from broadband photometric color to beta. Bothcalibrations are almost completely independent of theoreticalstellar-population models. We show that the recent marginal andnondetections of HDF U dropouts at radio and submillimeter wavelengthsare consistent with their assumed starburst nature and our calculatedA_1600. This is also true of recent observations of the ratio of opticalemission-line flux to UV flux density in the brightest U dropouts. Thislatter ratio turns out not to be a good indicator of dust extinction. InU dropouts, absolute magnitude M_1600,0 correlates with beta: brightergalaxies are redder, as is observed to be the case for local starburstgalaxies. This suggests that a mass-metallicity relationship is alreadyin place at z~3. The absorption-corrected UV luminosity function of Udropouts extends up to M_1600,0~-24 AB mag, corresponding to a starformation rate ~200 M_solar yr^-1 (H_0=50 km s^-1 Mpc^-3 and q_0=0.5 areassumed throughout). The absorption-corrected UV luminosity density atz~3 is rho_1600,0>=1.4x10^27 ergs^-1 Hz^-1 Mpc^-1. It is still alower limit since completeness corrections have not been done andbecause only galaxies with A_1600<~3.6 mag are blue enough in the UVto be selected as U dropouts. The luminosity-weighted meandust-absorption factor of our sample is 5.4+/-0.9 at 1600 Å.
| Mid-Infrared Emission from E+A Galaxies in the Coma Cluster
We have used ISO to observe at 12 μm seven E+A galaxies plus anadditional emission-line galaxy, all in the Coma Cluster. E+A galaxieslacking narrow emission lines have 2.2-12 μm flux density ratios orlimits similar to old stellar populations (typical of early-typegalaxies). Only galaxies with emission lines have enhanced 12 μm fluxdensity. Excess 12 μm emission is therefore correlated with thepresence of ongoing star formation or an active galactic nucleus (AGN).From the mid- and far-infrared colors of the brightest galaxy in oursample, which was detected at longer wavelengths with IRAS, we estimatethe far-infrared luminosity of these galaxies. By comparing the currentstar formation rates with previous rates estimated from the Balmerabsorption features, we divide the galaxies into two groups: those forwhich star formation has declined significantly following a dramaticpeak ~1 Gyr ago; and those with a significant level of ongoing starformation or/and an AGN. There is no strong difference in the spatialdistribution on the sky between these two groups. However, the firstgroup has systemic velocities above the mean cluster value and thesecond group has systemic velocities below that value. This suggeststhat the two groups differ kinematically. Based on surveys of the ComaCluster in the radio, the IRAS sources, and galaxies detected inHα emission, we sum the far-infrared luminosity function ofgalaxies in the cluster. We find that star formation in late-typegalaxies is probably the dominant component of the Coma Clusterfar-infrared luminosity. The presence of significant emission fromintracluster dust is not yet firmly established. The member galaxiesalso account for most of the far-infrared output from nearby richclusters in general. We update estimates of the far-infraredluminosities of nearby, rich clusters and show that such clusters arelikely to undergo luminosity evolution from z=0.4 at a rate similar to,or faster than, field galaxies.
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