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Near-infrared study of CIZA J1324.7-5736, the second richest cluster of galaxies in the Great Attractor
We present the result of a deep near-infrared survey of the newlyidentified X-ray luminous cluster of galaxies CIZA J1324.7-5736 in theGreat Attractor (GA) region. In a 35 × 35 arcmin2region, 111 galaxy candidates with rKs20 >arcsec are identified. Comparison of the extinction-correctedKs-band luminosity function of CIZA J1324.7-5736 with thoseof nearby clusters indicates that the richness class of CIZAJ1324.7-5736 is almost the same as, or richer than, the Pavo, Centaurusand Hydra clusters but poorer than the Coma, Perseus and Norma clusters.CIZA J1324.7-5736 is possibly the second richest cluster in the GAregion following the Norma cluster. The position of CIZA J1324.7-5736[in the (l, b, v) space] is close to the Centaurus-Crux cluster and theagglomeration of galaxies detected by the Parkes HI survey. CIZAJ1324.7-5736, together with the Centaurus-Crux cluster and the HI galaxyagglomeration, is most likely to be one of the richest localconcentrations in the GA overdensity of galaxies.
| Globular cluster systems in low-luminosity early-type galaxies near the Fornax cluster centre
We present a photometric study of the globular cluster systems (GCSs) ofthe Fornax cluster galaxies NGC1374, NGC1379 and NGC1387. The dataconsist of images from the wide-field MOSAIC imager of the Cerro TololoInter-American Observatory (CTIO) 4-m telescope, obtained withWashington C and Kron-Cousins R filters. The images cover a field of 36× 36arcmin2, corresponding to 200 ×200kpc2 at the Fornax distance. Two of the galaxies, NGC1374and NGC1379, are low-luminosity ellipticals while NGC1387 is alow-luminosity lenticular. Their cluster systems are still embedded inthe cluster system of NGC1399. Therefore, the use of a large field iscrucial and some differences to previous work can be explained by this.The colour distributions of all GCSs are bimodal. NGC1387 presents aparticularly distinct separation between red and blue clusters and anoverproportionally large population of red clusters. The radialdistribution is different for blue and red clusters, red clusters beingmore concentrated towards the respective galaxies. The different colourand radial distributions point to the existence of two globular clustersubpopulations in these galaxies. Specific frequencies are in the rangeSN= 1.4-2.4, smaller than the typical values for ellipticalgalaxies. These galaxies might have suffered tidal stripping of blueglobular clusters by NGC1399.
| Optical Counterparts of Ultraluminous X-Ray Sources Identified from Archival HST WFPC2 Images
We present a systematic analysis of archival HST WFPC2 ``Association''data sets that correlate with the Chandra positions of a set of 44ultraluminous X-ray sources (ULXs) of nearby galaxies. The mainmotivation is to address the nature of ULXs by searching for opticalcounterparts. Sixteen of the ULXs are found in early-type galaxies (RC3Hubble type <3). We have improved the Chandra/HST relative astrometrywhenever possible, resulting in errors circles of 0.3"-1.7" in size.Disparate numbers of potential ULX counterparts are found, and in somecases none are found. The lack of or low number of counterparts in somecases may be due to insufficient depth in the WFPC2 images. Particularlyin late-type galaxies, the HST image in the ULX region was often complexor crowded, requiring source detection to be performed manually. Wetherefore address various scenarios for the nature of the ULX since itis not known which, if any, of the sources found are true counterparts.The optical luminosities of the sources are typically in the range104-106 Lsolar, with (effective) Vmagnitudes typically in the range 22-24. In several cases colorinformation is available, with the colors roughly tending to be more redin early-type galaxies. This suggests that, in general, the (potential)counterparts found in early-type galaxies are likely to be older stellarpopulations and are probably globular clusters. Several early-typegalaxy counterparts have blue colors, which may be due to youngerstellar populations in the host galaxies, however, these could also bebackground sources. In spiral galaxies the sources may also be due tolocalized structure in the disks rather than bound stellar systems.Alternatively, some of the counterparts in late-type galaxies may beisolated supergiant stars. The observed X-ray/optical flux ratio isdiluted by the optical emission of the cluster in cases where the systemis an X-ray binary in a cluster, particularly in the case of a low-massX-ray binaries in an old cluster. If any of the counterparts are boundsystems with ~104-106 stars and are the truecounterparts to the ULX sources, then the X-ray luminosities of the ULXare generally well below the Eddington limit for a black hole with mass~0.1% of the cluster mass. Finally, we find that the optical flux of thecounterparts is consistent with being dominated by emission from anaccretion disk around an intermediate-mass black hole if the black holehappens to have a mass >~102 Msolar and isaccreting at close to the Eddington rate, unless the accretion disk isirradiated (which would result in high optical disk luminosities atlower black hole masses).Based on observations made with the NASA/ESA Hubble Space Telescope,obtained from the Data Archive at the Space Telescope Science Institute,which is operated by the Association of Universities for Research inAstronomy, Inc., under NASA contract NAS 5-26555. This project isassociated with Archival proposal 9545.
| Large-scale study of the NGC 1399 globular cluster system in Fornax
We present a Washington C and Kron-Cousins R photometric study of theglobular cluster system of NGC 1399, the central galaxy of the Fornaxcluster. A large areal coverage of 1 square degree around NGC 1399 isachieved with three adjoining fields of the MOSAIC II Imager at the CTIO4-m telescope. Working on such a large field, we can perform the firstindicative determination of the total size of the NGC 1399 globularcluster system. The estimated angular extent, measured from the NGC 1399centre and up to a limiting radius where the areal density of blueglobular clusters falls to 30 per cent of the background level, is 45± 5 arcmin, which corresponds to 220-275 kpc at the Fornaxdistance. The bimodal colour distribution of this globular clustersystem, as well as the different radial distribution of blue and redclusters, up to these large distances from the parent galaxy, areconfirmed. The azimuthal globular cluster distribution exhibitsasymmetries that might be understood in terms of tidal stripping ofglobulars from NGC 1387, a nearby galaxy. The good agreement between theareal density profile of blue clusters and a projected dark-matter NFWdensity profile is emphasized.
| Extragalactic globular clusters in the near-infrared. V. IC 4051 and NGC 3311
We present the results of combined optical and near-infrared photometryfor the globular cluster systems of the giant ellipticals IC 4051 andNGC 3311. We use the reduced age-metallicity degeneracy in (V-I) vs.(V-H) color-color diagrams to derive the cumulative age distributionwithin the red sub-population of globular clusters and to search for agesub-populations. The age distribution is then compared to the onedetermined for simulated globular cluster systems in order to setconstraints on the relative age and size of these globular clustersub-populations. In both galaxies we find a significant fraction ofglobular clusters with ages between 2-5 Gyr. We also investigate themetallicity distribution in both systems. Small number statisticsprevent us from making any definite statements concerning NGC 3311, butwe find that the derived metallicity distribution of the IC 4051clusters strongly depends on the assumed age distribution. Based on ourmost likely result that finds a large number of young/intermediate ageclusters (~2 Gyr) within the selected globular cluster sample, we findmetallicity peaks at ~-0.2 for the old clusters and +0.8 for the youngclusters. Only few very metal poor clusters are found. However, themetallicity distribution within the young/intermediate globular clusterpopulation is significantly affected by our choice of the applied SingleStellar Population model. The mean metallicity of the second generationof globular clusters changes from the above mentioned and extremely high+0.8 dex to +0.2 dex. Note that the model dependency becomes less severewith an increasing age of the cluster population.
| The distance to Hydra and Centaurus from surface brightness fluctuations: Consequences for the Great Attractor model
We present I-band Surface Brightness Fluctuation (SBF) measurements for16 early-type galaxies (3 giants, 13 dwarfs) in the central region ofthe Hydra cluster, based on deep photometric data in 7 fields obtainedwith VLT FORS1. From the SBF-distances to the galaxies in our sample weestimate the distance of the Hydra cluster to be 41.2 ± 1.4 Mpc((m-M)=33.07 ± 0.07 mag). Based on an improved correction forfluctuations from undetected point sources, we revise the SBF-distanceto the Centaurus cluster from Mieske & Hilker (2003, A&A, 410,455) upwards by 10% to 45.3 ± 2.0 Mpc ((m-M)=33.28 ± 0.09mag). The relative distance modulus of the two clusters then is(m-M)_Cen-(m-M)_Hyd=0.21 ± 0.11 mag. With H_0= 72 ± 4 kms-1 Mpc-1, we estimate a positive peculiarvelocity of 1225 ± 235 km s-1 for Hydra and 210± 295 km s-1 for the Cen30 component of Centaurus.Allowing for a thermal velocity dispersion of 200 km s-1,this rules out a common peculiar flow velocity for both clusters at 98%confidence. We find that the 9× 1015 Mȯ“Great Attractor” at a distance of ≃45 Mpc can explainthe observed peculiar velocities if shifted about 15° towards theHydra cluster position. Our results are inconsistent at 94% confidencewith a scenario where the Centaurus cluster is identical to the GA. Inorder to better restrict partially degenerate Great Attractor parameterslike its mass and distance, a recalculation of the local flow model withupdated distance information over a larger area than covered by us wouldbe needed.
| A wide-field photometric study of the globular cluster system of NGC 4636
Previous smaller-scale studies of the globular cluster system of NGC4636, an elliptical galaxy in the southern part of the Virgo cluster,have revealed an unusually rich globular cluster system. Were-investigate the cluster system of NGC 4636 with wide-field Washingtonphotometry. The globular cluster luminosity function can be followedroughly 1 mag beyond the turn-over magnitude found at {V} =23.31±0.13 for the blue cluster sub-population. This correspondsto a distance modulus of ({m}-{M})=31.24±0.17, 0.4 mag largerthan the distance determined from surface brightness fluctuations. Thehigh specific frequency is confirmed, yet the exact value remainsuncertain because of the uncertain distance: it varies between5.6±1.2 and 8.9±1.2. The globular cluster system has aclearly bimodal color distribution. The color peak positions show noradial dependence and are in good agreement with the values found forother galaxies studied in the same filter system. However, a luminositydependence is found: brighter clusters with an“intermediate” color exist. The clusters exhibit a shallowradial distribution within 7´, represented by a power-law with anexponent of -1.4. Within the same radial interval, the galaxy light hasa distinctly steeper profile. Because of the difference in the clusterand light distribution the specific frequency increases considerablywith radius. At 7´ and 9´ the density profiles of the redand blue clusters, respectively, change strongly: the power-law indicesdecrease to around -5 and become similar to the galaxy profile. Thissteep profile indicates that we reach the outer rim of the clustersystem at approximately 11´. This interpretation is supported bythe fact that in particular the density distribution of the blue clusterpopulation can be well fit by the projection of a truncated power-lawmodel with a core. This feature is seen for the first time in a globularcluster system. While the radial distribution of the cluster and fieldpopulations are rather different, this is not true for the ellipticityof the system: the elongation as well as the position angle of thecluster system agree well with the galaxy light. We compare the radialdistribution of globular clusters with the light profiles for a sampleof elliptical galaxies. The difference observed in NGC 4636 is typicalof an elliptical galaxy of this luminosity. The intrinsic specificfrequency of the blue population is considerably larger than that of thered one.Tables A.1 to A.6 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/433/43
| Inhomogeneity in the Hot Intracluster Medium of Abell 1060 Observed with Chandra
A Chandra observation of the non-cooling flow cluster A 1060 hasconfirmed that the hot intracluster medium has fairly uniformdistributions of temperature and metal abundance from a radius of about230kpc to the central 5kpc region ( H0 = 75 km s-1Mpc-1). The radial temperature profile shows a broad peak at30-40kpc from the center at a level 20% higher than that in theouter region. Assuming spatially uniform temperature and abundancedistributions, we derived a 3-dimensional density structure byiteratively correcting the β model, and obtained the central gasdensity to be 8.2+1.8-1.0 × 10-3cm-3. The distribution of gravitational mass was estimatedfrom the density profile, and a central concentration of mass within aradius of 50kpc was indicated. The data also suggest severalhigh-abundance regions. The most significant blob adjacent to thecentral galaxy NGC 3311 has a radius of about 9kpc, which indicates ametallicity of 1.5 solar. We consider that this blob may beproduced by the gas stripped off from NGC 3311.
| A deep near-infrared survey around the giant radio galaxy PKS 1343-601
We present the results of a deep near-infrared survey of a 36 × 36arcmin2 region centred on the giant elliptical radio galaxyPKS 1343-601, suggested to be the core of an unknown rich clusterlocated at the low Galactic latitude of b= 1.°73 in the GreatAttractor (GA) region. 19 obvious galaxies and 38 galaxy candidates havebeen detected; only three of them were previously identified as agalaxy. The total Galactic extinction AK towards our surveyarea is estimated to be 0.6-0.8 mag from the J-K colour of foregroundgiants. This is systematically lower by about 0.4 mag than AKtaken from the IRAS/DIRBE extinction map. The number density of galaxiesbrighter than an extinction-corrected Ks band magnitude of 13 is 42galaxies deg-2, five times as high as the overall average inthe GA region. However, the number of galaxies within the central270-kpc radius is less than that of the Norma, Pavo and Centaurusclusters in the GA region. We found no evidence that a rich cluster isassociated with PKS 1343-601.
| K-band Properties of Galaxy Clusters and Groups: Brightest Cluster Galaxies and Intracluster Light
We investigate the near-infrared K-band properties of the brightestcluster galaxies (BCGs) in a sample of 93 X-ray galaxy clusters andgroups, using data from the Two Micron All Sky Survey. Our clustersample spans a factor of 70 in mass, making it sensitive to any clustermass-related trends. We derive the cumulative radial distribution forthe BCGs in the ensemble and find that 70% of the BCGs are centered inthe cluster to within 5% of the virial radius r200; thisquantifies earlier findings that BCG position coincides with the clustercenter as defined by the X-ray emission peak. We study the correlationsbetween the luminosity of the BCGs (Lb) and the mass and theluminosity of the host clusters, finding that BCGs in more massiveclusters are more luminous than their counterparts in less massivesystems and that the BCGs become less important in the overall clusterlight (L200) as cluster mass increases. By examining a largesample of optically selected groups, we find that these correlationshold for galactic systems less massive than our clusters(<3×1013 Msolar). From the differencesbetween luminosity functions in high- and low-mass clusters, we arguethat BCGs grow in luminosity mainly by merging with other luminousgalaxies as the host clusters grow hierarchically; the decreasing BCGluminosity fraction (Lb/L200) with cluster massindicates that the rate of luminosity growth in BCGs is slow compared tothe rate at which clusters acquire galaxy light from the field or othermerging clusters. Utilizing the observed correlation between the clusterluminosity and mass and a merger tree model for cluster formation, weestimate that the amount of intracluster light (ICL) increases withcluster mass; our calculations suggest that in 1015Msolar clusters more than 50% of total stellar mass is inICL, making the role of ICL very important in the evolution andthermodynamic history of clusters. The cluster baryon fractionaccounting for the ICL is in good agreement with the value derived fromcosmic microwave background observations. The inclusion of ICL reducesthe discrepancy between the observed cluster cold baryon fraction andthat found in hydrodynamical simulations. Based on the observed ironabundance in the intracluster medium, we find that the ICL predicted byour model, together with the observed galaxy light, match the ironmass-to-light ratio expected from simple stellar population models,provided that the Salpeter initial mass function is adopted. The ICLalso makes it easier to produce the ``iron excess'' found in the centralregions of cool-core clusters.
| The Globular Cluster System of NGC 1399. II. Kinematics of a Large Sample of Globular Clusters
We study the kinematics and dynamics of the globular cluster system ofNGC 1399, the brightest elliptical galaxy near the center of the Fornaxcluster of galaxies. The observational data consists ofmedium-resolution spectra, obtained at the Very Large Telescope withFORS2 and the Mask Exchange Unit (MXU). Our sample comprises 468 radialvelocities in the magnitude range 201.6) and blue clusters (C-R<1.6), and find velocitydispersions for these groups of 255+/-13 and 291+/-14 km s-1,respectively, again radially constant. Any possible rotation of eitherof these cluster populations is below the detection limit, with theexception of a weak signature of rotation for the blue clusters moredistant than 6'. Spherical models point to a circular velocity of419+/-30 km s-1, assuming isotropy for the red clusters. Thisvalue is constant out to 40 kpc. The inferred dark halo potential can bewell represented by a logarithmic potential. A halo of the NFW type alsoprovides a good fit to the observations. The orbital structure of theclusters can only be weakly constrained. It is consistent with isotropyfor the red clusters and a slight tangential bias for the blue clusters.Some mass profiles derived from X-ray analyses do not agree with aconstant circular velocity within our radial range, irrespective of itsexact value. Interpreting the extreme low radial velocities as spacevelocities of bound clusters near their pericentric distances wouldrequire an extension of the cluster system of at least 200 kpc.Implications for formation scenarios of the cluster system are brieflycommented on.Based on observations collected at the European Southern Observatory,Cerro Paranal, Chile; ESO program 66.B-0393.
| FLASH redshift survey - I. Observations and catalogue
The FLAIR Shapley-Hydra (FLASH) redshift survey catalogue consists of4613 galaxies brighter than bJ= 16.7 (corrected for Galacticextinction) over a 700-deg2 region of sky in the generaldirection of the Local Group motion. The survey region is a70°× 10° strip spanning the sky from the ShapleySupercluster to the Hydra cluster, and contains 3141 galaxies withmeasured redshifts. Designed to explore the effect of the galaxyconcentrations in this direction (in particular the Supergalactic planeand the Shapley Supercluster) upon the Local Group motion, the 68 percent completeness allows us to sample the large-scale structure betterthan similar sparsely-sampled surveys. The survey region does notoverlap with the areas covered by ongoing wide-angle (Sloan or 2dF)complete redshift surveys. In this paper, the first in a series, wedescribe the observation and data reduction procedures, the analysis forthe redshift errors and survey completeness, and present the surveydata.
| Galaxy Luminosity Functions from Deep Spectroscopic Samples of Rich Clusters
Using a new spectroscopic sample and methods accounting forspectroscopic sampling fractions that vary in magnitude and surfacebrightness, we present R-band galaxy luminosity functions (GLFs) for sixnearby galaxy clusters with redshifts of 4000 kms-1
| Redshift-Distance Survey of Early-Type Galaxies: Spectroscopic Data
We present central velocity dispersions and Mg2 line indicesfor an all-sky sample of ~1178 elliptical and S0 galaxies, of which 984had no previous measures. This sample contains the largest set ofhomogeneous spectroscopic data for a uniform sample of ellipticalgalaxies in the nearby universe. These galaxies were observed as part ofthe ENEAR project, designed to study the peculiar motions and internalproperties of the local early-type galaxies. Using 523 repeatedobservations of 317 galaxies obtained during different runs, the dataare brought to a common zero point. These multiple observations, takenduring the many runs and different instrumental setups employed for thisproject, are used to derive statistical corrections to the data and arefound to be relatively small, typically <~5% of the velocitydispersion and 0.01 mag in the Mg2 line strength. Typicalerrors are about 8% in velocity dispersion and 0.01 mag inMg2, in good agreement with values published elsewhere.
| Redshift-Distance Survey of Early-Type Galaxies: Circular-Aperture Photometry
We present R-band CCD photometry for 1332 early-type galaxies, observedas part of the ENEAR survey of peculiar motions using early-typegalaxies in the nearby universe. Circular apertures are used to tracethe surface brightness profiles, which are then fitted by atwo-component bulge-disk model. From the fits, we obtain the structuralparameters required to estimate galaxy distances using theDn-σ and fundamental plane relations. We find thatabout 12% of the galaxies are well represented by a pure r1/4law, while 87% are best fitted by a two-component model. There are 356repeated observations of 257 galaxies obtained during different runsthat are used to derive statistical corrections and bring the data to acommon system. We also use these repeated observations to estimate ourinternal errors. The accuracy of our measurements are tested by thecomparison of 354 galaxies in common with other authors. Typical errorsin our measurements are 0.011 dex for logDn, 0.064 dex forlogre, 0.086 mag arcsec-2 for<μe>, and 0.09 for mRC,comparable to those estimated by other authors. The photometric datareported here represent one of the largest high-quality and uniformall-sky samples currently available for early-type galaxies in thenearby universe, especially suitable for peculiar motion studies.Based on observations at Cerro Tololo Inter-American Observatory (CTIO),National Optical Astronomy Observatory, which is operated by theAssociation of Universities for Research in Astronomy, Inc., undercooperative agreement with the National Science Foundation (NSF);European Southern Observatory (ESO); Fred Lawrence Whipple Observatory(FLWO); and the MDM Observatory on Kitt Peak.
| The Globular Cluster System of NGC 1399. I. A Wide-Field Photometric Study
We present a photometric investigation of the globular clusterpopulation of NGC 1399, the central galaxy in the Fornax cluster, inWashington C and Kron R filters within a field of 36'×36',corresponding to about 200×200 kpc at the Fornax distance. This isthe largest area around this galaxy ever studied with CCD photometry.The cluster system of NGC 1399 is found to extend farther than 100 kpcaway from the galaxy. The color distribution exhibits a pronouncedbimodality. Within a radial distance of about 55 kpc, the red clustersare more strongly concentrated toward the center than the blue clusters.At larger radii, the surface density profiles of the clusters areindistinguishable and match well the distribution of the galaxy light.Over the entire radial distance range, the surface brightness profile ofNGC 1399 can be very well fitted by a power law with an exponent of-1.85 and a core radius of 3.3". No steepening of the luminosity profilecan be detected at large radii. We suggest that the power-law profile ofNGC 1399 results from the galaxy being embedded in a large dark matterhalo, which prevents the stellar density profile from steepeningoutward. The cluster system contains 6450+/-700 clusters and thespecific frequency is found to be 5.1+/-1.2 in the V band. While NGC1399 shows a pronounced color gradient the nearby comparison galaxy NGC1404 does not show such a gradient. Using simple assumptions about theunderlying population that formed during the same star formation eventas the globular clusters, we present a model in which we use radiallychanging local specific frequencies for the red and blue subpopulationsto fit the observations. We find that within 7' the required specificfrequency of the blue clusters alone is a factor of approximately 3larger than that of the red ones. Outside this radius, however, bothpopulations have the same high local specific frequency of around 8 and13 (blue and red clusters, respectively).Based partly on observations collected at the European SouthernObservatory, Cerro Paranal, Chile; ESO program 66.B-0393.
| Hubble Space Telescope Imaging of Brightest Cluster Galaxies
We used the Hubble Space Telescope Wide Field Planetary Camera 2 toobtain I-band images of the centers of 81 brightest cluster galaxies(BCGs), drawn from a volume-limited sample of nearby BCGs. The imagesshow a rich variety of morphological features, including multiple ordouble nuclei, dust, stellar disks, point-source nuclei, and centralsurface brightness depressions. High-resolution surface brightnessprofiles could be inferred for 60 galaxies. Of those, 88% havewell-resolved cores. The relationship between core size and galaxyluminosity for BCGs is indistinguishable from that of Faber et al.(published in 1997, hereafter F97) for galaxies within the sameluminosity range. However, the core sizes of the most luminous BCGs fallbelow the extrapolation of the F97 relationshiprb~L1.15V. A shallower relationship,rb~L0.72V, fits both the BCGs and thecore galaxies presented in F97. Twelve percent of the BCG sample lacks awell-resolved core; all but one of these BCGs have ``power law''profiles. Some of these galaxies have higher luminosities than anypower-law galaxy identified by F97 and have physical upper limits onrb well below the values observed for core galaxies of thesame luminosity. These results support the idea that the centralstructure of early-type galaxies is bimodal in its physical propertiesbut also suggest that there exist high-luminosity galaxies withpower-law profiles (or unusually small cores). The BCGs in the lattercategory tend to fall at the low end of the BCG luminosity function andtend to have low values of the quantity α (the logarithmic slopeof the metric luminosity as a function of radius, at 10 kpc). Sincetheoretical calculations have shown that the luminosities andα-values of BCGs grow with time as a result of accretion, thissuggests a scenario in which elliptical galaxies evolve from power-lawprofiles to core profiles through accretion and merging. This isconsistent with theoretical scenarios that invoke the formation ofmassive black hole binaries during merger events. More generally, theprevalence of large cores in the great majority of BCGs, which arelikely to have experienced several generations of galaxy merging,underscores the role of a mechanism that creates and preserves cores insuch merging events.Based on observations made with the NASA/ESA Hubble Space Telescope,obtained at the Space Telescope Science Institute, which is operated bythe Association of Universities for Research in Astronomy, Inc., underNASA contract NAS 5-26555. These observations are associated withproposal 8683.
| 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
| Formation and evolution of globular clusters (II): models
In this paper many interesting and important models about the formationand evolution of globular cluster are reviewed and compared with eachother. A newly developed model about the self-enrichment for globularclusters proposed by the authors is also briefly discussed.
| Specific frequencies, metallicities and mass functions of globular cluster systems
Three problems, the specific frequencies, metallicities and massspectra, in studies of globular cluster systems are reviewed anddiscussed for current knowledge and open issues. It is noted thatdifferent between specific frequencies of globular clusters fromgalaxies to galaxies indicate different formation models. Themetallicity distributions imply three probable epochs of globularcluster formation corresponding to three kinds of formation models. Thepower-law initial mass functions can be physically connected withglobular cluster formation even though the preliminary results ofsimulations with the log-normal initial mass functions are moreconsistent with current observations.
| Early-type galaxy distances from the Fundamental Plane and surface brightness fluctuations
We compare two of the most popular methods for deriving distances toearly-type galaxies: the Fundamental Plane (FP) and surface brightnessfluctuations (SBF). Distances for 170 galaxies are compared. A third setof distances is provided by predictions derived from the density fieldof the IRAS redshift survey. Overall there is good agreement between thedifferent distance indicators. We investigate systematic trends in theresiduals of the three sets of distance comparisons. First, we find thatseveral nearby, low-luminosity, mainly S0 galaxies have systematicallylow FP distances. Because these galaxies also have Mg2indices among the lowest in the sample, we conclude that they deviatefrom the FP partly because of recent star formation and consequently lowmass-to-light ratios; differences in their internal velocity structuresmay also play a role. Secondly, we find some evidence that theground-based I -band SBF survey distances (Tonry et al. 2001) begin toshow a bias near the survey limit at , which is expected for this sortof distance-limited survey, but had not previously been demonstrated.Although SBF and FP distances are affected in opposite senses by errorsin the Galactic extinction estimates, we find no evidence for biases inthe distances due to Galactic extinction. The tie between theCepheid-calibrated SBF distances (Mpc) and the far-field calibrated FPdistances (kms-1 ) yields a Hubble constant , while thecomparison between SBF and the IRAS -reconstructed distances yields(independent errors only). Thus there is a marginal inconsistency in thedirect and IRAS -reconstructed ties to the Hubble flow (this can be seenindependently of the SBF distances). Possible explanations includesystematic errors in the redshift survey completeness estimates or inthe FP aperture corrections, but at this point the best estimate of H0 may come from a simple average of the above two estimates.After revising the SBF distances downward by 2.8 per cent to be inagreement with the final set of Key Project Cepheid distances (Freedmanet al.), we conclude that from early-type galaxies, where the seconderror bar represents the total systematic uncertainty in the distancezero-point. We also discuss the `fluctuation star count', recentlyintroduced by Tonry et al. (2001) as a less demanding alternative to forcalibrating SBF distances. The N -calibrated SBF method is akin to ahybrid SBF-FP distance indicator, and we find that the use of N actuallyimproves the SBF distances. Further study of the behaviour of thisquantity may provide an important new test for models of ellipticalgalaxy formation.
| Chandra Observation of the Central Galaxies in the A1060 Cluster of Galaxies
A Chandra observation of the central region of the A1060 cluster ofgalaxies resolved X-ray emission from two giant elliptical galaxies, NGC3311 and NGC 3309. The emission from these galaxies consists of twocomponents, namely, the hot interstellar medium (ISM) and the low-massX-ray binaries (LMXBs). We found that the spatial extent of the ISMcomponent was much smaller than that of stars for both galaxies, whilethe ratios of X-ray to optical blue-band luminosities were rather lowbut within the general scatter for elliptical galaxies. Aftersubtracting the LMXB component, the ISM is shown to be in pressurebalance with the intracluster medium of A1060 at the outer boundary ofthe ISM. These results imply that the hot gas supplied from stellar massloss is confined by the external pressure of the intracluster medium,with the thermal conduction likely to be suppressed. The cD galaxy NGC3311 does not exhibit the extended potential structure that is commonlyseen in bright elliptical galaxies, and we discuss the possibleevolution history of the very isothermal cluster A1060.
| X-Ray Binaries and Globular Clusters in Elliptical Galaxies
The X-ray emission from normal elliptical galaxies has two majorcomponents: soft (kT~0.2-1 keV) emission from diffuse gas and harder(kT~6 keV) emission from populations of accreting (low mass) stellarX-ray binaries. If the low-mass X-ray binary (LMXB) population isintimately tied to the field stellar population in a galaxy, itsaggregate X-ray luminosity is expected to be simply proportional to theoptical luminosity of the galaxy. However, recent ASCA and Chandra X-rayobservations show that the global luminosities of LMXB components inelliptical galaxies exhibit significant scatter (a factor of ~4) at agiven optical luminosity. This scatter may reflect a range ofevolutionary stages among X-ray binary populations in ellipticalgalaxies of different ages. If so, the ratio of the global LMXB X-rayluminosity to the galactic optical luminosity,LLMXB/Lopt, may in principle be used to determinewhen the bulk of stars were formed in individual elliptical galaxies. Totest this we compare variations in LLMXB/Lopt forLMXB populations in elliptical galaxies to optically derived estimatesof stellar ages in the same galaxies. We find no correlation, whichsuggests that variations in LLMXB/Lopt are not agood age indicator for elliptical galaxies. Alternatively, LMXBs may beformed primarily in globular clusters (through stellar tidalinteractions) rather than comprise a subset of the primordial binarystar population in a galactic stellar field. Since elliptical galaxiesexhibit a wide range of globular cluster populations for a givengalactic luminosity, this may induce a dispersion in the LMXBpopulations of elliptical galaxies with similar optical luminosities.Indeed, we find that LLMXB/Lopt ratios for LMXBpopulations are strongly correlated with the specific globular clusterfrequencies in elliptical galaxies. This suggests that most LMXBs wereformed in globular clusters. If so, Chandra observations of centraldominant galaxies with unusually large globular cluster populationsshould find proportionally excessive numbers of LMXBs.
| Redshift-Distance Survey of Early-Type Galaxies. I. The ENEARc Cluster Sample
This paper presents data on the ENEARc subsample of the larger ENEARsurvey of nearby early-type galaxies. The ENEARc galaxies belong toclusters and were specifically chosen to be used for the construction ofa Dn-σ template. The ENEARc sample includes newmeasurements of spectroscopic and photometric parameters (redshift,velocity dispersion, line index Mg2, and the angular diameterdn), as well as data from the literature. New spectroscopicdata are given for 229 cluster early-type galaxies, and new photometryis presented for 348 objects. Repeat and overlap observations withexternal data sets are used to construct a final merged catalogconsisting of 640 early-type galaxies in 28 clusters. Objectivecriteria, based on catalogs of groups of galaxies derived from completeredshift surveys of the nearby universe, are used to assign galaxies toclusters. In a companion paper, these data are used to construct thetemplate Dn-σ distance relation for early-typegalaxies, which has been used to estimate galaxy distances and derivepeculiar velocities for the ENEAR all-sky sample. Based on observationsat Complejo Astronomico El Leoncito, operated under agreement betweenthe Consejo Nacional de Investigaciones Científicas de laRepública Argentina and the National Universities of La Plata,Córdoba, and San Juan; Cerro Tololo Inter-American Observatory,National Optical Astronomical Observatory, which is operated by theAssociation of Universities for Research in Astronomy, Inc., undercooperative agreement with the National Science Foundation; the EuropeanSouthern Observatory (ESO), partially under the ESO-ON agreement; theFred Lawrence Whipple Observatory; the Observatório do Pico dosDias, operated by the Laboratório Nacional de Astrofísicaand the MDM Observatory at Kitt Peak.
| The Colors of Globular Clusters
A compilation has been made of available data on the ratio of the numberof metal-rich ([Fe/H]>-1.0) to metal-poor ([Fe/H]<-1.0) clustersin various globular cluster systems. Among early-type galaxies of typesE, E/S0, and S0, the ratio of blue to red globular clusters is found tovary by almost 2 orders of magnitude. The data suggest that cD galaxieshave the widest range of evolutionary histories. The fraction ofmetal-rich red clusters is largest among early-type galaxies and appearsto decrease toward later Hubble types.
| ASCA Temperature Maps of Three Clusters of Galaxies: Abell 1060, AWM 7, and the Centaurus Cluster
We present two-dimensional temperature maps of three bright clusters ofgalaxies (Abell 1060, AWM 7, and the Centaurus cluster), based onmulti-pointing observations with the ASCA GIS. The temperatures werederived from hardness ratios by taking into account the XRT response.For the Centaurus cluster, we subtracted the central cool componentusing the previous ASCA and ROSAT results, and the metallicity gradientsobserved in AWM 7 and the Centaurus cluster were included in derivingthe temperatures. The intracluster medium in Abell 1060 and AWM 7 isalmost isothermal from the center to the outer regions with temperaturesof 3.3 and 3.9 keV, respectively. The Centaurus cluster exhibitsremarkable hot regions within about 30' from the cluster center, showinga temperature increase of ×0.8 keV from the surrounding level of3.5keV, and the outer cool regions with lower temperatures by -1.3 keV.These results imply that a strong merger has occurred in the Centaurusin the recent 2-3Gyr, and that the central cool component has survivedit. In contrast, the gas in Abell 1060 was well-mixed in an earlyperiod, which probably has prevented the development of a central coolcomponent. In AWM 7, mixing of the gas should have occurred in a periodearlier than the epoch of metal enrichment.
| X-Ray Probing of the Central Regions of Clusters of Galaxies
The results on ASCA X-ray study of the central regions ofmedium-richness clusters of galaxies are summarized, while emphasizingthe differences between cD and non-cD clusters. The intra-cluster medium(ICM) is likely to consist of two (hot and cool) phases within ~ 100 kpcof a cD galaxy, where the ICM metallicity is also enhanced. In contrast,the ICM in non-cD clusters appears to be isothermal with a smallmetallicity gradient right of the center. The gravitational potentialexhibits a hierarchical nesting around cD galaxies, while a totalmass-density profile with a central cusp is indicated for a non-cDcluster, Abell 1060. The iron-mass-to-light ratio of the ICM decreasestoward the center in both types of clusters, although it is radiallyconstant in peripheral regions. The silicon-to-iron abundance ratio inthe ICM increases with the cluster richness, but remains close to thesolar ratio around cD galaxies. These overall results are interpretedwithout appealing to the popular cooling-flow hypothesis. Instead, anemphasis is put on the halo-in-halo structure formed around cD galaxies.
| A catalogue and analysis of X-ray luminosities of early-type galaxies
We present a catalogue of X-ray luminosities for 401 early-typegalaxies, of which 136 are based on newly analysed ROSAT PSPC pointedobservations. The remaining luminosities are taken from the literatureand converted to a common energy band, spectral model and distancescale. Using this sample we fit the LX:LB relationfor early-type galaxies and find a best-fit slope for the catalogue of~2.2. We demonstrate the influence of group-dominant galaxies on the fitand present evidence that the relation is not well modelled by a singlepower-law fit. We also derive estimates of the contribution to galaxyX-ray luminosities from discrete-sources and conclude that they provideLdscr/LB~=29.5ergs-1LBsolar-1. Wecompare this result with luminosities from our catalogue. Lastly, weexamine the influence of environment on galaxy X-ray luminosity and onthe form of the LX:LB relation. We conclude thatalthough environment undoubtedly affects the X-ray properties ofindividual galaxies, particularly those in the centres of groups andclusters, it does not change the nature of whole populations.
| A synthesis of data from fundamental plane and surface brightness fluctuation surveys
We perform a series of comparisons between distance-independentphotometric and spectroscopic properties used in the surface brightnessfluctuation (SBF) and fundamental plane (FP) methods of early-typegalaxy distance estimation. The data are taken from two recent surveys:the SBF Survey of Galaxy Distances and the Streaming Motions of AbellClusters (SMAC) FP survey. We derive a relation between(V-I)0 colour and Mg2 index using nearly 200galaxies and discuss implications for Galactic extinction estimates andearly-type galaxy stellar populations. We find that the reddenings fromSchlegel et al. for galaxies with E(B-V)>~0.2mag appear to beoverestimated by 5-10 per cent, but we do not find significant evidencefor large-scale dipole errors in the extinction map. In comparison withstellar population models having solar elemental abundance ratios, thegalaxies in our sample are generally too blue at a given Mg2;we ascribe this to the well-known enhancement of the α-elements inluminous early-type galaxies. We confirm a tight relation betweenstellar velocity dispersion σ and the SBF `fluctuation count'parameter N, which is a luminosity-weighted measure of the total numberof stars in a galaxy. The correlation between N and σ is eventighter than that between Mg2 and σ. Finally, we deriveFP photometric parameters for 280 galaxies from the SBF survey data set.Comparisons with external sources allow us to estimate the errors onthese parameters and derive the correction necessary to bring them on tothe SMAC system. The data are used in a forthcoming paper, whichcompares the distances derived from the FP and SBF methods.
| The connection between globular cluster systems and the host galaxies
A large number of early-type galaxies are now known to possess blue andred subpopulations of globular clusters. We have compiled a data base of28 such galaxies exhibiting bimodal globular cluster colourdistributions. After converting to a common V-I colour system, weinvestigate correlations between the mean colour of the blue and redsubpopulations with galaxy velocity dispersion. We support previousclaims that the mean colours of the blue globular clusters are unrelatedto their host galaxy. They must have formed rather independently of thegalaxy potential they now inhabit. The mean blue colour is similar tothat for halo globular clusters in our Galaxy and M31. The red globularclusters, on the other hand, reveal a strong correlation with galaxyvelocity dispersion. Furthermore, in well-studied galaxies the redsubpopulation has similar, and possibly identical, colours to the galaxyhalo stars. Our results indicate an intimate link between the redglobular clusters and the host galaxy; they share a common formationhistory. A natural explanation for these trends would be the formationof the red globular clusters during galaxy collapse.
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