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A new method to determine the thickness of non-edge-on disk galaxies
Aims.We present a new method to determine the thickness of non-edge-ondisk galaxies. This method allows us to investigate the mass-to-lightratio of the disk. Methods: .Our method is based on the comparisonof observations and theory of the distribution of the vertical velocitydispersion, which is obtained from the solution of three dimensionalPoisson equations and the galactic dynamical equation. Results:.As examples, the thickness and mass-to-light ratio of two diskgalaxies, NGC 1566 and NGC 5247, which have been extensively studied byspectroscopy, have been calculated. The calculated results areconsistent with observations and support the use of this method.However, due to the small sample size available, the results should beconfirmed on other samples of galaxies.
| Metal-poor Globular Clusters and the Formation of Their Host Galaxies
We have determined the total numbers and specific frequencies of blue,metal-poor globular clusters (GCs) in eight spiral and early-typegalaxies. These data, along with five measurements from the literature,show a trend of increasing blue GC specific frequency with increasingmass of the host galaxy. The increase is not accounted for in a simplegalaxy formation model in which elliptical galaxies and their GC systemsare formed by the merger of typical spiral galaxies. The data appearbroadly consistent with hierarchical formation scenarios in whichmetal-poor GCs are formed over a finite period in the early universeduring the initial stages of galaxy assembly. In this picture, theobserved trend is related to biasing, in the sense that the more massivegalaxies of today began assembling earlier and therefore formedrelatively more GCs during this early epoch of metal-poor GC formation.We discuss how comparisons of the observed specific frequency ofmetal-poor GCs with model calculations can constrain the formationredshift of these objects.
| Hα Imaging of Early-Type Sa-Sab Spiral Galaxies. II. Global Properties
New results, based on one of the most comprehensive Hα imagingsurveys of nearby Sa-Sab spirals completed to date, reveals early-typespirals to be a diverse group of galaxies that span a wide range inmassive star formation rates. While the majority of Sa-Sab galaxies inour sample are forming stars at a modest rate, a significant fraction(~29%) exhibit star formation rates greater than 1 Msolaryr-1, rivaling the most prolifically star-forming late-typespirals. A similar diversity is apparent in the star formation historyof Sa-Sab spirals as measured by their Hα equivalent widths.Consistent with our preliminary results presented in the first paper inthis series, we find giant H II regions [L(Hα)>=1039ergs s-1] in the disks of ~37% of early-type spirals. Wesuspect that recent minor mergers or past interactions are responsiblefor the elevated levels of Hα emission and, perhaps, for thepresence of giant H II regions in these galaxies. Our results, however,are not in total agreement with the Hα study of Kennicutt &Kent, who did not find any early-type spirals with Hα equivalentwidths >14 Å. A close examination of the morphologicalclassification of galaxies, however, suggests that systematicdifferences between the Revised Shapley-Ames Catalog and the SecondReference Catalogue may be responsible for the contrasting results.Based on observations obtained with the 3.5 m telescope at Apache PointObservatory (APO) and the 0.9 m telescope at Kitt Peak NationalObservatory (KPNO). The APO 3.5 m telescope is owned and operated by theAstrophysical Research Consortium.
| The Globular Cluster Systems of Five Nearby Spiral Galaxies: New Insights from Hubble Space Telescope Imaging
We use available multifilter Hubble Space Telescope (HST) WFPC2 imagingof five (M81, M83, NGC 6946, M101, and M51, in order of distance)low-inclination, nearby spiral galaxies to study ancient star clusterpopulations. Combining rigorous selection criteria to rejectcontaminants (individual stars, background galaxies, and blends) withoptical photometry including the U bandpass, we unambiguously detectancient globular cluster (GC) systems in each galaxy. We presentluminosities, colors, and size (effective radius) measurements for ourcandidate GCs. These are used to estimate specific frequencies, toassess whether intrinsic color distributions are consistent with thepresence of both metal-poor and metal-rich GCs, and to compare relativesizes of ancient clusters between different galaxy systems. M81globulars have intrinsic color distributions that are very similar tothose in the Milky Way and M31, with ~40% of sample clusters havingcolors expected for a metal-rich population. The GC system in M51meanwhile, appears almost exclusively blue and metal-poor. This lack ofmetal-rich GCs associated with the M51 bulge indicates that the bulgeformation history of this Sbc galaxy may have differed significantlyfrom that of our own. Ancient clusters in M101 and possibly in NGC 6946,two of the three later type spirals in our sample, appear to haveluminosity distributions that continue to rise to our detection limit(MV~-6.0), well beyond the expected turnover(MV~-7.4) in the luminosity function. This is reminiscent ofthe situation in M33, a Local Group galaxy of similar Hubble type. Thefaint ancient cluster candidates in M101 and NGC 6946 have properties(colors and reff) similar to their more luminouscounterparts, and we suggest that these are either intermediate-age (3-9Gyr) disk clusters or the low-mass end of the original GC population.Potentially, these lower mass clusters were not destroyed because ofdifferent dynamical conditions relative to those present in earlier typegalaxies. If the faint, excess GC candidates are excluded, we find thatthe specific frequency (SN) of ancient clusters formed inlater type spirals is roughly constant, with SN=0.5+/-0.2. Ifwe consider only the blue, metal-poor clusters in the early-type spiralM81, this galaxy is also consistent with having formed a ``universal''specific frequency of halo GC population, with a value ofSN~0.6. By combining the results of this study withliterature values for other systems, we find that the total GC specificfrequencies in spirals appear to correlate best with Hubble type andbulge/total ratio, rather than with galaxy luminosity or galaxy mass.
| The Globular Cluster Systems of the Early-Type Galaxies NGC 3379, NGC 4406, and NGC 4594 and Implications for Galaxy Formation
We have investigated the global properties of the globular cluster (GC)systems of three early-type galaxies: the Virgo Cluster elliptical NGC4406, the field elliptical NGC 3379, and the field S0 galaxy NGC 4594.These galaxies were observed as part of a wide-field CCD survey of theGC populations of a large sample of normal galaxies beyond the LocalGroup. Images obtained with the Mosaic detector on the Kitt Peak 4 mtelescope provide radial coverage to at least 24', or ~70-100 kpc. Weuse BVR photometry and image classification to select GC candidates andthereby reduce contamination from non-GCs, as well as Hubble SpaceTelescope WFPC2 data to help quantify the contamination that remains.The GC systems of all three galaxies have color distributions with atleast two peaks and show modest negative color gradients. Theproportions of blue GCs range from 60% to 70% of the total populations.The GC specific frequency (SN) of NGC 4406 is 3.5+/-0.5, ~20%lower than past estimates and nearly identical to SN for theother Virgo Cluster elliptical included in our survey, NGC 4472.SN for NGC 3379 and NGC 4594 are 1.2+/-0.3 and 2.1+/-0.3,respectively; these are similar to past values, but the errors have beenreduced by a factor of 2-3. We compare our results for the early-typesample (including NGC 4472) to models for the formation of massivegalaxies and their GC systems. Of the scenarios we consider, ahierarchical merging picture, in which metal-poor GCs form at highredshift in protogalactic building blocks and metal-rich GC populationsare built up over time during subsequent gas-rich mergers, appears mostconsistent with the data.
| The ISOPHOT 170 μm Serendipity Survey II. The catalog of optically identified galaxies%
The ISOPHOT Serendipity Sky Survey strip-scanning measurements covering≈15% of the far-infrared (FIR) sky at 170 μm were searched forcompact sources associated with optically identified galaxies. CompactSerendipity Survey sources with a high signal-to-noise ratio in at leasttwo ISOPHOT C200 detector pixels were selected that have a positionalassociation with a galaxy identification in the NED and/or Simbaddatabases and a galaxy counterpart visible on the Digitized Sky Surveyplates. A catalog with 170 μm fluxes for more than 1900 galaxies hasbeen established, 200 of which were measured several times. The faintest170 μm fluxes reach values just below 0.5 Jy, while the brightest,already somewhat extended galaxies have fluxes up to ≈600 Jy. For thevast majority of listed galaxies, the 170 μm fluxes were measured forthe first time. While most of the galaxies are spirals, about 70 of thesources are classified as ellipticals or lenticulars. This is the onlycurrently available large-scale galaxy catalog containing a sufficientnumber of sources with 170 μm fluxes to allow further statisticalstudies of various FIR properties.Based on observations with ISO, an ESA project with instruments fundedby ESA Member States (especially the PI countries: France, Germany, TheNetherlands and the UK) and with the participation of ISAS and NASA.Members of the Consortium on the ISOPHOT Serendipity Survey (CISS) areMPIA Heidelberg, ESA ISO SOC Villafranca, AIP Potsdam, IPAC Pasadena,Imperial College London.Full Table 4 and Table 6 are only available in electronic form at theCDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or viahttp://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/422/39
| Properties of isolated disk galaxies
We present a new sample of northern isolated galaxies, which are definedby the physical criterion that they were not affected by other galaxiesin their evolution during the last few Gyr. To find them we used thelogarithmic ratio, f, between inner and tidal forces acting upon thecandidate galaxy by a possible perturber. The analysis of thedistribution of the f-values for the galaxies in the Coma cluster leadus to adopt the criterion f ≤ -4.5 for isolated galaxies. Thecandidates were chosen from the CfA catalog of galaxies within thevolume defined by cz ≤5000 km s-1, galactic latitudehigher than 40o and declination ≥-2.5o. Theselection of the sample, based on redshift values (when available),magnitudes and sizes of the candidate galaxies and possible perturberspresent in the same field is discussed. The final list of selectedisolated galaxies includes 203 objects from the initial 1706. The listcontains only truly isolated galaxies in the sense defined, but it is byno means complete, since all the galaxies with possible companions underthe f-criterion but with unknown redshift were discarded. We alsoselected a sample of perturbed galaxies comprised of all the diskgalaxies from the initial list with companions (with known redshift)satisfying f ≥ -2 and \Delta(cz) ≤500 km s-1; a totalof 130 objects. The statistical comparison of both samples showssignificant differences in morphology, sizes, masses, luminosities andcolor indices. Confirming previous results, we found that late spiral,Sc-type galaxies are, in particular, more frequent among isolatedgalaxies, whereas Lenticular galaxies are more abundant among perturbedgalaxies. Isolated systems appear to be smaller, less luminous and bluerthan interacting objects. We also found that bars are twice as frequentamong perturbed galaxies compared to isolated galaxies, in particularfor early Spirals and Lenticulars. The perturbed galaxies have higherLFIR/LB and Mmol/LB ratios,but the atomic gas content is similar for the two samples. The analysisof the luminosity-size and mass-luminosity relations shows similartrends for both families, the main difference being the almost totalabsence of big, bright and massive galaxies among the family of isolatedsystems, together with the almost total absence of small, faint and lowmass galaxies among the perturbed systems. All these aspects indicatethat the evolution induced by interactions with neighbors would proceedfrom late, small, faint and low mass Spirals to earlier, bigger, moreluminous and more massive spiral and lenticular galaxies, producing atthe same time a larger fraction of barred galaxies but preserving thesame relations between global parameters. The properties we found forour sample of isolated galaxies appear similar to those of high redshiftgalaxies, suggesting that the present-day isolated galaxies could bequietly evolved, unused building blocks surviving in low densityenvironments.Tables \ref{t1} and \ref{t2} are only available in electronic form athttp://www.edpsciences.org
| Box- and peanut-shaped bulges. III. A new class of bulges: Thick Boxy Bulges
Inspecting all 1224 edge-on disk galaxies larger than 2\arcmin in theRC3 on Digitized Sky Survey (DSS) images (Lütticke et al.\cite{lue2000a}) we have found several galaxies with extraordinarybulges meeting two criteria: they are box shaped and large in respect tothe diameters of their galaxies. These bulges are often disturbed, showfrequently prominent irregularities and asymmetries, and some possesspossible merger remnants or merging satellites. For these bulges we haveintroduced the term ``Thick Boxy Bulges'' (TBBs). About 2% of all diskgalaxies (S0-Sd), respectively 4% of all galaxies with box- andpeanut-shaped (b/p) bulges, belong to this class of galaxies. Usingmulticolour CCD and NIR data we have enlarged and followed up our sampleof nearly 20 galaxies with a TBB. The disturbed morphology of a largefraction of these galaxies shows that many of the TBB galaxies are notdynamically settled. For the TBBs the extent of the box shape seems tobe too large to result from a normal bar potential. Therefore weconclude that two classes of b/p bulges exist with different origins.While most (96%) b/p bulges can be explained by bars alone(Lütticke et al. \cite{lue2000b}), the extended boxy structures ofTBBs result most likely from accreted material by infalling satellitecompanions (soft merging).
| Hubble Space Telescope observations of globular cluster systems along the Hubble sequence of spiral galaxies
We have studied the globular cluster systems of seven giant, edge-onspiral galaxies using Hubble Space Telescope imaging in V and I. Thegalaxy sample covers the Hubble types Sa to Sc, allowing us to study thevariation of the properties of globular cluster systems along the Hubblesequence. The photometry reaches ~1.5 mag beyond the turn-over magnitudeof the globular cluster luminosity function for each galaxy. Specificfrequencies of globular clusters (SN values) were evaluatedby comparing the numbers of globular clusters found in our WFPC2pointings with those in our Milky Way that would be detected in the samespatial region if placed at the distance of the target galaxies. Resultsfrom this method were found to be consistent with the more commonly usedmethod of constructing radial distribution functions of globularclusters. The SN values of spirals with B/T<~ 0.3 (i.e.spirals with a Hubble type later than about Sb) are consistent with avalue of SN= 0.55 +/- 0.25. We suggest that this populationof globular clusters represents a `universal', old halo population thatis present around each galaxy. Most galaxies in our sample haveSN values that are consistent with a scenario in whichglobular cluster systems are made up of (i) the aforementioned halopopulation plus (ii) a population that is associated with bulges, whichgrows approximately linearly with the mass of the bulge. Such scenariosinclude the `merger scenario' for the formation of elliptical galaxiesas well as the `multi-phase collapse' scenario, but it seemsinconsistent with the `secular evolution' scenario of Pfenniger &Norman, in which bulges are formed from disc stars by means of theredistribution of angular momentum through bar instabilities and/orminor perturbations. However, there is one bulge-dominated spiral galaxyin our sample (NGC7814) with a low SN value that isconsistent with those of the latest-type spirals. This means that the`secular evolution' scenario can still be viable for somebulge-dominated spirals. Thus, our results suggest that the formationhistories of galaxy bulges of early-type spirals can be significantlydifferent from one galaxy to another.
| Globular Clusters as Candidates for Gravitational Lenses to Explain Quasar-Galaxy Associations
We argue that globular clusters (GCs) are good candidates forgravitational lenses in explaining quasar-galaxy associations. Thecatalog of associations (Bukhmastova 2001) compiled from the LEDAcatalog of galaxies (Paturel 1997) and from the catalog of quasars(Veron-Cetty and Veron 1998) is used. Based on the new catalog, we showthat one might expect an increased number of GCs around irregulargalaxies of types 9 and 10 from the hypothesis that distant compactsources are gravitationally lensed by GCs in the halos of foregroundgalaxies. The King model is used to determine the central surfacedensities of 135 GCs in the Milky Way. The distribution of GCs incentral surface density was found to be lognormal.
| Measuring Distances and Probing the Unresolved Stellar Populations of Galaxies Using Infrared Surface Brightness Fluctuations
To empirically calibrate the IR surface brightness fluctuation (SBF)distance scale and probe the properties of unresolved stellarpopulations, we measured fluctuations in 65 galaxies using NICMOS on theHubble Space Telescope. The early-type galaxies in this sample includeelliptical and S0 galaxies and spiral bulges in a variety ofenvironments. Absolute fluctuation magnitudes in the F160W (1.6 μm)filter (MF160W) were derived for each galaxy using previouslymeasured I-band SBF and Cepheid variable star distances. F160W SBFs canbe used to measure distances to early-type galaxies with a relativeaccuracy of ~10%, provided that the galaxy color is known to ~0.035 magor better. Near-IR fluctuations can also reveal the properties of themost luminous stellar populations in galaxies. Comparison of F160Wfluctuation magnitudes and optical colors to stellar population modelpredictions suggests that bluer elliptical and S0 galaxies havesignificantly younger populations than redder ones and may also be moremetal-rich. There are no galaxies in this sample with fluctuationmagnitudes consistent with old, metal-poor (t>5 Gyr, [Fe/H]<-0.7)stellar population models. Composite stellar population models implythat bright fluctuations in the bluer galaxies may be the result of anepisode of recent star formation in a fraction of the total mass of agalaxy. Age estimates from the F160W fluctuation magnitudes areconsistent with those measured using the Hβ Balmer-line index. Thetwo types of measurements make use of completely different techniquesand are sensitive to stars in different evolutionary phases. Bothtechniques reveal the presence of intermediate-age stars in theearly-type galaxies of this sample.Based on observations with the NASA/ESA Hubble Space Telescope, obtainedat the Space Telescope Science Institute, which is operated by AURA,Inc., under NASA contract NAS 5-26555.
| The Globular Cluster System of the Spiral Galaxy NGC 7814
We present the results of a wide-field photometric study of the globularcluster (GC) system of the edge-on Sab spiral NGC 7814. This is thefirst spiral to be fully analyzed from our survey of the GC systems of alarge sample of galaxies beyond the Local Group. NGC 7814 is ofparticular interest because a previous study estimated that it has500-1000 GCs, giving it the largest specific frequency (SN)known for a spiral. Understanding this galaxy's GC system is importantin terms of our understanding of the GC populations of spirals ingeneral and has implications for the formation of massive galaxies. Weobserved the galaxy in BVR filters with the WIYN 3.5 m telescope andused image classification and three-color photometry to select GCcandidates. We also analyzed archival Hubble Space Telescope (HST) WideField Planetary Camera 2 images of NGC 7814, both to help quantify thecontamination level of the WIYN GC candidate list and to detect GCs inthe inner part of the galaxy halo. Combining HST data with high-qualityground-based images allows us to trace the entire radial extent of thisgalaxy's GC system and determine the total number of GCs directlythrough observation. We find that rather than being an especiallyhigh-SN spiral, NGC 7814 has <~200 GCs andSN~1, making it comparable to the two most well-studiedspiral galaxies, the Milky Way and M31. We explore the implications ofthese results for models of the formation of galaxies and their GCsystems. The initial results from our survey suggest that the GC systemsof typical elliptical galaxies can be accounted for by the merger of twoor more spirals, but that for highly luminous elliptical galaxies,additional physical processes may be needed.
| 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
| A catalogue and analysis of local galaxy ages and metallicities
We have assembled a catalogue of relative ages, metallicities andabundance ratios for about 150 local galaxies in field, group andcluster environments. The galaxies span morphological types from cD andellipticals, to late-type spirals. Ages and metallicities were estimatedfrom high-quality published spectral line indices using Worthey &Ottaviani (1997) single stellar population evolutionary models. Theidentification of galaxy age as a fourth parameter in the fundamentalplane (Forbes, Ponman & Brown 1998) is confirmed by our largersample of ages. We investigate trends between age and metallicity, andwith other physical parameters of the galaxies, such as ellipticity,luminosity and kinematic anisotropy. We demonstrate the existence of agalaxy age-metallicity relation similar to that seen for local galacticdisc stars, whereby young galaxies have high metallicity, while oldgalaxies span a large range in metallicities. We also investigate theinfluence of environment and morphology on the galaxy age andmetallicity, especially the predictions made by semi-analytichierarchical clustering models (HCM). We confirm that non-clusterellipticals are indeed younger on average than cluster ellipticals aspredicted by the HCM models. However we also find a trend for the moreluminous galaxies to have a higher [Mg/Fe] ratio than the lowerluminosity galaxies, which is opposite to the expectation from HCMmodels.
| Bar Galaxies and Their Environments
The prints of the Palomar Sky Survey, luminosity classifications, andradial velocities were used to assign all northern Shapley-Ames galaxiesto either (1) field, (2) group, or (3) cluster environments. Thisinformation for 930 galaxies shows no evidence for a dependence of barfrequency on galaxy environment. This suggests that the formation of abar in a disk galaxy is mainly determined by the properties of theparent galaxy, rather than by the characteristics of its environment.
| 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.
| Local velocity field from sosie galaxies. I. The Peebles' model
Pratton et al. (1997) showed that the velocity field around clusterscould generate an apparent distortion that appears as tangentialstructures or radial filaments. In the present paper we determine theparameters of the Peebles' model (1976) describing infall of galaxiesonto clusters with the aim of testing quantitatively the amplitude ofthis distortion. The distances are determined from the concept of sosiegalaxies (Paturel 1984) using 21 calibrators for which the distanceswere recently calculated from two independent Cepheid calibrations. Weuse both B and I-band magnitudes. The Spaenhauer diagram method is usedto correct for the Malmquist bias. We give the equations for theconstruction of this diagram. We analyze the apparent Hubble constant indifferent regions around Virgo and obtain simultaneously the Local Groupinfall and the unperturbed Hubble constant. We found:[VLG-infall = 208 ± 9 km s-1] [\log H =1.82 ± 0.04 (H ≈ 66 ± 6 km s-1Mpc-1).] The front side and backside infalls can be seenaround Virgo and Fornax. In the direction of Virgo the comparison ismade with the Peebles' model. We obtain: [vinfall} =CVirgo/r0.9 ± 0.2] withCVirgo=2800 for Virgo and CFornax=1350 for Fornax,with the adopted units (km s-1 and Mpc). We obtain thefollowing mean distance moduli: [μVirgo=31.3 ± 0.2(r=18 Mpc )] [μFornax=31.7 ± 0.3 (r=22 Mpc). ] Allthese quantities form an accurate and coherent system. Full Table 2 isonly available in electronic form at the CDS via anonymous ftp tocdsarc.u-strasbg.fr (130.79.128.5) or viahttp://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/393/57
| 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.
| A Possible Relationship between Quasars and Clusters of Galaxies
The distribution on the sky of clusters of galaxies shows significantassociation with relatively nearby, large, active galaxies. The patternis that of clusters paired equidistant across a central galaxy with theapparent magnitudes and redshifts of their constituent galaxies beingclosely matched. The clusters and the galaxies in them tend to be strongX-ray and radio emitters, and their redshifts occur at preferredredshift values. The central, low-redshift galaxies often show evidenceof ejection in the direction of these higher redshift clusters. In allthese respects the clusters resemble closely quasars which have beenincreasingly shown for the last 34 years to be similarly associated withactive parent galaxies. New, especially significant pairings of quasarsare presented here, which are, at the same time, associated with Abellclusters of galaxies. It is argued here that, empirically, the quasarsare ejected from active galaxies. They evolve to lower redshift withtime, forming stars, and fragmenting at the end of their developmentinto clusters of low-luminosity galaxies. The cluster galaxies can be atthe same distance as their lower redshift parents because they stillretain a component of their earlier, quasar intrinsic redshift.
| The Multitude of Unresolved Continuum Sources at 1.6 Microns in Hubble Space Telescope Images of Seyfert Galaxies
We examine 112 Seyfert galaxies observed by the Hubble Space Telescopeat 1.6 μm. We find that ~50% of the Seyfert 2.0 galaxies which arepart of the Revised Shapely-Ames (RSA) Catalog or the CfA redshiftsample contain unresolved continuum sources at 1.6 μm. All but acouple of the Seyfert 1.0-1.9 galaxies display unresolved continuumsources. The unresolved sources have fluxes of order 1 mJy,near-infrared luminosities of order 1041 ergs s-1,and absolute magnitudes MH~-16. Comparison non-Seyfertgalaxies from the RSA Catalog display significantly fewer (~20%),somewhat lower luminosity nuclear sources, which could be due to compactstar clusters. We find that the luminosities of the unresolved Seyfert1.0-1.9 sources at 1.6 μm are correlated with [O III] λ5007and hard X-ray luminosities, implying that these sources are nonstellar.Assuming a spectral energy distribution similar to that of a Seyfert 2galaxy, we estimate that a few percent of local spiral galaxies containblack holes emitting as Seyferts at a moderate fraction,~10-1-10-4, of their Eddington luminosities. Wefind no strong correlation between 1.6 μm fluxes and hard X-ray or [OIII] λ5007 fluxes for the pure Seyfert 2.0 galaxies. Thesegalaxies also tend to have lower 1.6 μm luminosities compared to theSeyfert 1.0-1.9 galaxies of similar [O III] luminosity. Either largeextinctions (AV~20-40) are present toward theircontinuum-emitting regions or some fraction of the unresolved sources at1.6 μm are compact star clusters. With increasing Seyfert type thefraction of unresolved sources detected at 1.6 μm and the ratio of1.6 μm to [O III] fluxes tend to decrease. These trends areconsistent with the unification model for Seyfert 1 and 2 galaxies.
| The SBF Survey of Galaxy Distances. IV. SBF Magnitudes, Colors, and Distances
We report data for I-band surface brightness fluctuation (SBF)magnitudes, (V-I) colors, and distance moduli for 300 galaxies. Thesurvey contains E, S0, and early-type spiral galaxies in the proportionsof 49:42:9 and is essentially complete for E galaxies to Hubblevelocities of 2000 km s-1, with a substantial sampling of Egalaxies out to 4000 km s-1. The median error in distancemodulus is 0.22 mag. We also present two new results from the survey.(1) We compare the mean peculiar flow velocity (bulk flow) implied byour distances with predictions of typical cold dark matter transferfunctions as a function of scale, and we find very good agreement withcold, dark matter cosmologies if the transfer function scale parameterΓ and the power spectrum normalization σ8 arerelated by σ8Γ-0.5~2+/-0.5. Deriveddirectly from velocities, this result is independent of the distributionof galaxies or models for biasing. This modest bulk flow contradictsreports of large-scale, large-amplitude flows in the ~200 Mpc diametervolume surrounding our survey volume. (2) We present adistance-independent measure of absolute galaxy luminosity, N and showhow it correlates with galaxy properties such as color and velocitydispersion, demonstrating its utility for measuring galaxy distancesthrough large and unknown extinction. Observations in part from theMichigan-Dartmouth-MIT (MDM) Observatory.
| The Soft X-Ray Properties of Nearby Low-Luminosity Active Galactic Nuclei and their Contribution to the Cosmic X-Ray Background
We have examined ROSAT soft X-ray observations of a complete,distance-limited sample of Seyfert and LINER galaxies. X-ray data areavailable for 46 out of 60 such objects which lie within a hemisphere ofradius 18 Mpc. We have constructed radial profiles of the nuclearsources in order to characterize their spatial extent and, in somecases, to help constrain the amount of flux associated with a nuclearpoint source. PSPC data from ROSAT have been used to explore thespectral characteristics of the objects with sufficient numbers ofdetected counts. Based on the typical spectral parameters of thesesources, we have estimated the luminosities of the weaker sources in thesample. We then explore the relationship between the soft X-ray andHα luminosities of the observed objects; these quantities arecorrelated for higher luminosity AGNs. We find a weak correlation at lowluminosities as well, and we have used this relationship to predictLX for the 14 objects in our sample that lack X-ray data.Using the results of the spatial and spectral analyses, we have comparedthe X-ray properties of Seyferts and LINERs, finding no strikingdifferences between the two classes of objects. However, both types ofobjects often exhibit significant amounts of extended emission, whichcould minimize the appearance of differences in their nuclearproperties. The soft X-ray characteristics of the type 1 and type 2active galaxies in the sample are also discussed. We then compute thelocal X-ray volume emissivity of low-luminosity Seyferts and LINERs andinvestigate their contribution to the cosmic X-ray background. The0.5-2.0 keV volume emissivity of 2.2×1038 ergss-1 Mpc-3 we obtain for our sample suggests thatlow-luminosity AGNs produce at least 9% of the soft X-ray background.
| The formation of galaxy bulges: Spectrophotometric constraints
We have measured Mg2, Fe 5270 and Fe 5335 spectrophotometricindices (LICK system) in the bulge of 89 galaxies, mostly spirals fromthe Héraudeau (\cite{her96}) sample. The indices are reduced to anull velocity dispersion and normalized to an aperture of 0.2h-1 kpc. The mean errors are 0.009 mag on Mg2, and0.3 Å on the iron indices. These measurements almost double theamount of similar data already available on spiral galaxies. Our dataconfirm the existence of the relation between Mg2, andsigma0, the central stellar velocity dispersion; we find aneven tighter relation between Mg2, andVmrot, the maximum rotational velocity of thegalaxy, deduced from HI observations. For the most massive bulges, thesecorrelations may be interpreted as a mass-metallicity relation. However,the presence of young stellar populations, traced by the detection of[OIII] lambda 5007 Å, emission, provides clear evidence that ageeffects do play a role. Since the contribution of the young populationis anti-correlated to the mass of the galaxy, it continues theMg2, vs. sigma0 , relation toward thelow-sigma0, region and globally increases its slope. We alsopresent evidence for a new positive correlation between Fe indices andsigma0, and for a significant correlation between theline-strength indices and the total or disk luminosity. We propose tomodel the whole sequence of bulges within the folowing framework: bulgesare composed of a primary population formed prior to the disk, duringthe initial collapse, and of a secondary population formed during itsevolution. The whole family of bulges can be classified into threeclasses: (A) the bulges dominated by young populations are generallysmall, have ionized gas, low velocity dispersion and low line strengths;(B) the bulges dominated by the primary population lie along themass-metallicity sequence defined for elliptical galaxies; and (C) thebulges where the secondary population is significant are lessMg-over-abundant than (B)-type bulges and deviate from theMg2, vs. sigma0, relation of elliptical galaxies.Based on observations collected at the Observatoire de Haute-Provence.Table 3 is presented in electronic form only at the CDS. Tables 1 and 2are also available form at the CDS, Strasbourg, via anonymous ftp tocdsarc.u-strasbg.fr (130.79.128.5) or viahttp://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/366/68
| Structural Characteristics of Faint Galaxies Serendipitously Discovered with the Hubble Space Telescope WFPC2
Utilizing the F814W and F300W filters, Hubble Space Telescope Wide FieldPlanetary Camera-2 (WFPC2) images were taken of four low surfacebrightness galaxies in the direction of the Virgo Cluster-V7L3, V2L8,V1L4, and Malin 1. The high resolution of the WFPC2 combined with theextremely diffuse nature of the four galaxies makes them essentiallytransparent, allowing for the serendipitous discovery of 139 backgroundgalaxies visible through both the disks and nuclei of the foregroundgalaxies. Surface photometry was done on the newly discovered galaxiesthrough the F814W (I-band) filter. The detected galaxies have bothr1/4 and exponential-type profiles with radii (to theμF814W=25.0 mag arcsec-2 limit) less than 5.0".Their total magnitudes range from 18.9 through the survey cutoff at 25.0in the F814W filter. The median central surface brightness of thosegalaxies with exponential profiles is approximately 1 mag brighter thanthe background F814W ``sky.'' Thus, with this data set we recoverFreeman's law and hence know that we do not have a representative sampleof distant galaxies (and neither does anyone else). When possible, theB, V, and I colors of these galaxies were determined using ground-basedimages, which show the galaxies to be fairly red. Coupled with theirsmall angular size, we estimate the redshifts to be 0.5<=z<=1.5.Classification of the galaxies was done strictly in structural terms,based only on the form of the derived luminosity profile. Nomorphological considerations were made during the classificationprocess. Twenty-three percent of the galaxies we detected have ther1/4 profile typical of early-type galaxies, matching mostprevious studies of both the Hubble Deep Field and the Medium DeepSurvey, which typically find 15%-40% E/S0 galaxies. In addition, we haveattempted to perform bulge/disk deconvolutions. While we find that mostof the sample cannot be easily deconvolved into a classic bulge+disk,seven objects could be fitted in this way. For these seven objects wefind (1) a large range in bulge-to-total luminosity and (2) some disksthat have a large bulge-to-disk ratio. We also present one object,283-10, which is an excellent example of the structural ambiguity thatexists in the luminosity profiles of distant galaxies. In agreement withother studies, we also found a significant percentage of galaxies thathave disturbed luminosity profiles indicative of probable galaxy-galaxyinteractions or mergers. Indirect indicators suggest that the volumeover which r1/4 objects are selected is significantly largerthan the volume over which disk galaxies are selected. This implies arelatively low space density of r1/4 at all redshifts out toz~2.5 and is consistent with the general idea that r1/4galaxies are largely confined to galaxy clusters.
| Nearby Optical Galaxies: Selection of the Sample and Identification of Groups
In this paper we describe the Nearby Optical Galaxy (NOG) sample, whichis a complete, distance-limited (cz<=6000 km s-1) andmagnitude-limited (B<=14) sample of ~7000 optical galaxies. Thesample covers 2/3 (8.27 sr) of the sky (|b|>20deg) andappears to have a good completeness in redshift (97%). We select thesample on the basis of homogenized corrected total blue magnitudes inorder to minimize systematic effects in galaxy sampling. We identify thegroups in this sample by means of both the hierarchical and thepercolation ``friends-of-friends'' methods. The resulting catalogs ofloose groups appear to be similar and are among the largest catalogs ofgroups currently available. Most of the NOG galaxies (~60%) are found tobe members of galaxy pairs (~580 pairs for a total of ~15% of objects)or groups with at least three members (~500 groups for a total of ~45%of objects). About 40% of galaxies are left ungrouped (field galaxies).We illustrate the main features of the NOG galaxy distribution. Comparedto previous optical and IRAS galaxy samples, the NOG provides a densersampling of the galaxy distribution in the nearby universe. Given itslarge sky coverage, the identification of groups, and its high-densitysampling, the NOG is suited to the analysis of the galaxy density fieldof the nearby universe, especially on small scales.
| Radio Sources in Low-Luminosity Active Galactic Nuclei. I. VLA Detections of Compact, Flat-Spectrum Cores
We report a high-resolution (0.2"), 15 GHz survey of a sample of 48low-luminosity active galactic nuclei with the Very LargeArray.5 Compact radio emission has beendetected above a flux density of 1.1 mJy in 57% (17 of 30) oflow-ionization nuclear emission-line region (LINER) nuclei andlow-luminosity Seyfert galaxies. The 2 cm radio power is significantlycorrelated with the emission-line ([O I] λ6300) luminosity. Usingradio fluxes at other frequencies from the literature, we find that atleast 15 of the 18 detected radio cores have a flat to inverted spectrum(α>=-0.3, Sν~να). While thepresent observations are consistent with the radio emission originatingin star-forming regions (the brightness temperatures are>=102.5-4.5 K), higher resolution radio observations of 10of the detected sources, reported in an accompanying paper, show thatthe cores are very compact (<~1 pc), of high brightness temperature(Tb>~108 K), and probably synchrotronself-absorbed, ruling out a starburst origin. Thus, our results suggestthat at least 50% of low-luminosity Seyfert galaxies and LINERs in thesample are accretion powered, with the radio emission presumably comingfrom jets or advection-dominated accretion flows. We have detected only1 of 18 ``transition'' (i.e., LINER+H II) nuclei observed, indicatingthat their radio cores are significantly weaker than those of ``pure''LINERs. Compact 2 cm radio cores are found in both type 1 (i.e., withbroad Hα) and type 2 (without broad Hα) nuclei. There isweak evidence, limited in significance by small numbers, thatlow-luminosity active galactic nuclei with compact radio cores exhibitradio ejecta preferentially aligned along the rotation axis of thegalaxy disk. If this result were confirmed by a larger sample, it wouldlend support to the idea that the misalignment of accretion disks withthe galaxy stellar disk in more luminous Seyfert galaxies is a result ofradiation-pressure-induced warping of their accretion disks.
| Box- and peanut-shaped bulges. I. Statistics
We present a classification for bulges of a complete sample of ~ 1350edge-on disk galaxies derived from the RC3 (Third Reference Catalogue ofBright Galaxies, de Vaucouleurs et al. \cite{rc3}). A visualclassification of the bulges using the Digitized Sky Survey (DSS) inthree types of b/p bulges or as an elliptical type is presented andsupported by CCD images. NIR observations reveal that dust extinctiondoes almost not influence the shape of bulges. There is no substantialdifference between the shape of bulges in the optical and in the NIR.Our analysis reveals that 45% of all bulges are box- and peanut-shaped(b/p). The frequency of b/p bulges for all morphological types from S0to Sd is > 40%. In particular, this is for the first time that such alarge frequency of b/p bulges is reported for galaxies as late as Sd.The fraction of the observed b/p bulges is large enough to explain theb/p bulges by bars. Partly based on observations collected at ESO/LaSilla (Chile), DSAZ/Calar Alto (Spain), and Lowell Observatory/Flagstaff(AZ/U.S.A.). Tables 6 and 7 are only available in electronic form at CDSvia anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or viahttp://cdsweb.u-strasbg.fr/Abstract.html
| The elliptical galaxy formerly known as the Local Group: merging the globular cluster systems
Prompted by a new catalogue of M31 globular clusters, we have collectedtogether individual metallicity values for globular clusters in theLocal Group. Although we briefly describe the globular cluster systemsof the individual Local Group galaxies, the main thrust of our paper isto examine the collective properties. In this way we are simulating thedissipationless merger of the Local Group, into presumably an ellipticalgalaxy. Such a merger is dominated by the Milky Way and M31, whichappear to be fairly typical examples of globular cluster systems ofspiral galaxies. The Local Group `Elliptical' has about 700 +/- 125globular clusters, with a luminosity function resembling the `universal'one. The metallicity distribution has peaks at [Fe/H] ~ -1.55 and -0.64with a metal-poor to metal-rich ratio of 2.5:1. The specific frequencyof the Local Group Elliptical is initially about 1 but rises to about 3,when the young stellar populations fade and the galaxy resembles an oldelliptical. The metallicity distribution and stellar populationcorrected specific frequency are similar to that of some known earlytype galaxies. Based on our results, we briefly speculate on the originof globular cluster systems in galaxies.
| 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.
| Properties of the Stellar Velocity Ellipsoid and Stability in Disks of Spiral Galaxies
Disks of spiral galaxies are characterized by effectively exponentialbrightness and presumably density distributions in both the radial andvertical directions. It is to be expected that the ratio between thescalelength and -height bears a relation to the axis ratio of thestellar velocity ellipsiod. Hydrostatic equilibrium connects thevertical velocity dispersion to the scaleheight. In the radial directionthe velocity dispersion relates to the scalelength through conditions oflocal stability. Preliminary applications are presented.
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