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Structural Parameters of Thin and Thick Disks in Edge-on Disk Galaxies
We analyze the global structure of 34 late-type, edge-on, undisturbed,disk galaxies spanning a wide range of mass. We measure structuralparameters for the galaxies using two-dimensional least-squares fittingto our R-band photometry. The fits require both a thick and a thin diskto adequately fit the data. The thick disks have larger scale heightsand longer scale lengths than the embedded thin disks by factors of ~2and ~1.25, respectively. The observed structural parameters agree wellwith the properties of thick and thin disks derived from star counts inthe Milky Way and from resolved stellar populations in nearby galaxies.We find that massive galaxies' luminosities are dominated by the thindisk. However, in low-mass galaxies (Vc<~120 kms-1) thick disk stars contribute nearly half the luminosityand dominate the stellar mass. Thus, although low-mass dwarf galaxiesappear blue, the majority of their stars are probably quite old.Our data are most easily explained by a formation scenario in which thethick disk is assembled through direct accretion of stellar materialfrom merging satellites while the thin disk is formed from accreted gas.The baryonic fraction in the thin disk therefore constrains the gasrichness of the merging pregalactic fragments. If we include the mass inH I as part of the thin disk, the thick disk contains <~10% of thebaryons in high-mass galaxies and ~25%-30% of the baryons in low-massgalaxies. Our data, therefore, indicate that the fragments were quitegas rich at the time of merging (fgas=75%-90%). However,because low-mass galaxies have a smaller fraction of baryons in theirthin disks, the pregalactic fragments from which they assembled musthave been systematically more gas poor. We believe this trend resultsfrom increased outflow due to supernova-driven winds in the lower masspregalactic fragments. We estimate that ~60% of the total baryonic massin these systems was lost due to outflows. Pushing the episode ofsignificant winds to early times allows the mass-metallicityrelationship for disks to be established early, before the main disk isassembled, and obviates the difficulty in driving winds from diffusedisks with low star formation efficiencies. We discuss otherimplications of this scenario for solving the G dwarf problem, forpredicting abundance trends in thick disks, and for removingdiscrepancies between semianalytic galaxy formation models and theobserved colors of low-mass galaxies.
| A Structural and Dynamical Study of Late-Type, Edge-on Galaxies. II. Vertical Color Gradients and the Detection of Ubiquitous Thick Disks
We present an analysis of optical (B-R) and optical-infrared(R-Ks) color maps for 47 extremely late-type edge-onunwarped, bulgeless disk galaxies spanning a wide range of mass. Thecolor maps show that the thin disks of these galaxies are embedded in alow surface brightness red envelope. This component is substantiallythicker than the thin disk (a:b~4:1 vs. >8:1), extends to at least 5vertical disk scale heights above the galaxy midplane, and has a radialscale length that appears to be uncorrelated with that of the embeddedthin disk. The color of the red envelope is similar from galaxy togalaxy, even when the thin disk is extremely blue, and is consistentwith a relatively old (>6 Gyr) stellar population that is notparticularly metal-poor. The color difference between the embedded thindisk and the red stellar envelope varies systematically with rotationspeed, reflecting an increasing age difference between the thin andthick components in lower mass galaxies, driven primarily by changes inthe age of the thin disk. The red stellar envelopes are similar to thethick disk of the Milky Way, having common surface brightnesses, spatialdistributions, mean ages, and metallicities. We argue that the ubiquityof the red stellar envelopes implies that the formation of the thickdisk is a nearly universal feature of disk formation and is notnecessarily connected to the formation of a bulge. Our data suggest thatthe thick disk forms early (>6 Gyr ago), even within galaxies where thebulk of the stars formed very recently (<2 Gyr). We argue thatseveral aspects of our data and the observed properties of the Milky Waythick disk argue in favor of a merger origin for the thick diskpopulation. If so, then the age of the thick disk marks the end of theepoch of major merging, and the age difference between the younger thindisk and the older thick disk can become a strong constraint oncosmological constants and models of galaxy and/or structure formation.
| A list of peculiar velocities of RFGC galaxies
A list of radial velocities, HI line widths and peculiar velocities of1327 galaxies from the RFGC catalogue has been compiled using actualobservations and literature data. The list can be used for studying bulkmotions of galaxies, construction of the field of peculiar velocitiesand other tasks.
| 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.
| A Structural and Dynamical Study of Late-Type, Edge-on Galaxies. I. Sample Selection and Imaging Data
We present optical (B and R) and infrared (Ks) images andphotometry for a sample of 49 extremely late-type, edge-on disk galaxiesselected from the Flat Galaxy Catalog of Karenchentsev et al. Our samplewas selected to include galaxies with particularly large axial ratios,increasing the likelihood that the galaxies in the sample are trulyedge-on. We have also concentrated the sample on galaxies with lowapparent surface brightness in order to increase the representation ofintrinsically low surface brightness galaxies. Finally, the sample waschosen to have no apparent bulges or optical warps so that the galaxiesrepresent undisturbed, ``pure disk'' systems. The resulting sample formsthe basis for a much larger spectroscopic study designed to placeconstraints on the physical quantities and processes that shape diskgalaxies. The imaging data presented in this paper have beenpainstakingly reduced and calibrated to allow accurate surfacephotometry of features as faint as 30 mag arcsec-2 in B and29 mag arcsec-2 in R on scales larger than 10". Because oflimitations in sky subtraction and flat-fielding, the infrared data canreach only to 22.5 mag arcsec-2 in Ks oncomparable scales. As part of this work, we have developed a new methodfor quantifying the reliability of surface photometry, which providesuseful diagnostics for the presence of scattered light, optical emissionfrom infrared cirrus, and other sources of nonuniform sky backgrounds.
| 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 Revised Flat Galaxy Catalogue.
We present a new improved and completed version of the Flat GalaxyCatalogue (FGC) named the Revised Flat Galaxy Catalogue (RFGC)containing 4236 thin edge-on spiral galaxies and covering the whole sky.The Catalogue is intended to study large-scale cosmic streamings as wellas other problems of observational cosmology. The dipole moment ofdistribution of the RFGC galaxies (l = 273 degr; b =+19 degr) lieswithin statistical errors (+/-10 degr) in the direction of the LocalGroup motion towards the Microwave Background Radiation (MBR).
| 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.
| The I-Band Tully-Fisher Relation for SC Galaxies: Optical Imaging Data
Properties derived from the analysis of photometric I-band imagingobservations are presented for 1727 inclined spiral galaxies, mostly oftypes Sbc and Sc. The reduction, parameter extraction, and errorestimation procedures are discussed in detail. The asymptotic behaviorof the magnitude curve of growth and the radial variation in ellipticityand position angle are used in combination with the linearity of thesurface brightness falloff to fit the disk portion of the profile. TotalI-band magnitudes are calculated by extrapolating the detected surfacebrightness profile to a radius of eight disk scale lengths. Errors inthe magnitudes, typically ~0.04 mag, are dominated by uncertainties inthe sky subtraction and disk-fitting procedures. Comparison is made withthe similar imaging database of Mathewson, Ford, & Buchhorn, both aspresented originally by those authors and after reanalyzing theirdigital reduction files using identical disk-fitting procedures. Directcomparison is made of profile details for 292 galaxies observed incommon. Although some differences occur, good agreement is found,proving that the two data sets can be used in combination with onlyminor accommodation of those differences. The compilation of opticalproperties presented here is optimized for use in applications of theTully-Fisher relation as a secondary distance indicator in studies ofthe local peculiar velocity field.
| A Complete Redshift Survey to the Zwicky Catalog Limit in a 2^h X 15 deg Region around 3C 273
We compile 1113 redshifts (648 new measurements, 465 from theliterature) for Zwicky catalog galaxies in the region (-3.5d <= delta<= 8.5d, 11h5 <= alpha <= 13h5). We include redshifts for 114component objects in 78 Zwicky catalog multiplets. The redshift surveyin this region is 99.5% complete to the Zwicky catalog limit, m_Zw =15.7. It is 99.9% complete to m_Zw = 15.5, the CfA Redshift Survey(CfA2) magnitude limit. The survey region is adjacent to the northernportion of CfA2, overlaps the northernmost slice of the Las CampanasRedshift Survey, includes the southern extent of the Virgo Cluster, andis roughly centered on the QSO 3C 273. As in other portions of theZwicky catalog, bright and faint galaxies trace the same large-scalestructure.
| Spectroscopy of Edge-On Spirals
We present HI line observations of \Ntot edge-on spiral galaxies,extracted from the Flat Galaxy Catalog of Karachentsev \etal (1993).Fluxes, systemic velocities and line widths are given for \Ndet detectedgalaxies, as well as search parameters for \Nnod undetected systems.Widths are corrected for instrumental broadening, smoothing,signal-to-noise and profile shape, and an estimate of the error on thewidth is given. When corrected for turbulent broadening and inclinationangle of the disks, the velocity widths presented here can provide theappropriate line width parameter needed to derive distances via theTully-Fisher relation.
| The peak apparent and true flattenings of flat galaxies.
Not Available
| Distribution of the spin vectors of the disk galaxies of the Virgo cluster. I. The catalogue of 310 disk galaxies in the Virgo area.
Not Available
| Flat galaxy catalogue
A systematic search for disklike edge-on-galaxies with a diameter largerthan a = 40 arcsec and a major-to-minor axis ratio a/b greater than 7was carried out by means of the Palomar Observatory Sky Survey and theESO/SERC survey. As a result, we present a new catalog of flat galaxies(FGC) containing 4455 objects and covering about 56 percent of the wholesky for the first time. The catalogue is assigned to study large-scalecosmic streamings and other problems of observational cosmology.
| The kinematics of the Virgo cluster revisited
The paper updates the velocity data of Virgo cluster galaxies andreconsiders the kinematic structure of the Virgo cluster. New velocitiesare given for 144 galaxies listed in the Virgo Cluster Catalog (VCC).Improved velocities are given for another 131 VCC galaxies. The Virgocluster is disentangled from its surrounding clouds of galaxies, and thelikely members of each of these clouds are listed. The velocitydistribution of dwarf elliptical cluster members is found to be highlyasymmetric. This phenomenon is interpreted as evidence for the imminentmerging of two subclusters in the core region, which points to thedynamical youth of the Virgo cluster. The mean heliocentric velocity ofthe Virgo cluster is estimated at 1050 +/- 35 km/s.
| Axial ratios of edge-on spirals
A diameter-limited sample of 888 normal Sa-Sc galaxies was compiled fromthe Uppsala General Catalog. New micrometer measures of the axial ratiosR of the disk components of 262 edge-on spirals in this sample were madeon copies of blue Palomar Sky Survey plates and calibrated againstphotometric standards. The distribution of isophotal axial ratios forthe whole sample was analyzed to give information on the true axialratios R0 of spiral disks. The mean value of logR0 is 0.95 +/- 0.03 and the dispersion about this mean is0.12 +/- 0.04. A similar mean value (0.90) was obtained from avolume-limited sub-sample of 348 spirals. The dispersion in logR0 is partly due to a dependence of R0 onmorphological type, and the mean value of log R0 for eachtype was estimated. Inclinations of 342 edge-on (R is greater than about3) spirals were determined from their isophotal axial ratios and types.No significant dependence of R0 on luminosity at each typewas found.
| Flat edge-on galaxies on the Tully-Fischer diagram.
For a sample of 114 northern galaxies with angular diameters greaterthan 2 arcmin and apparent axial ratios greater than 7, relations arediscussed between their global parameters: the inner motion amplitude W,the blue luminosity, the linear diameter, and the neutral hydrogen mass.Taken as a distance indicator for the given W, these parameters exhibitnearly the same efficiency. Outside the Local Supercluster the lineardiameter of the flat edge-on galaxy produces a standard deviation about25 percent as a distance estimate. The total mass-to-luminosity ratio offlat galaxies increases when their mean surface brightness decreases.
| The Tully-Fisher relation in different environments
The Tully-Fisher relation (TFR) in different environments wasinvestigated in 13 galaxy samples spanning a large range in galaxydensities, using two statistical tests to compare the TFR of differentsamples. Results of the analysis of TFR parameters in severalenvironments showed that, when samples of similar data-accuracy andmagnitude-range were compared, there was no significant differencebetween the galaxy samples. It is suggested that a comparison of sampleswith very different data accuracy or those biased by incompletenesseffects may lead to misleading results.
| H I observations in the Virgo cluster area. III - All 'member' spirals
H I observations of 141 spiral galaxies in and around the Virgo Clusterare reported, with major-axis mapping for 65 of them. Heliocentricvelocities, profile widths, and H I fluxes are given for all detectedgalaxies. Spin orientations are given for mapped galaxies and H Idiameters for those sufficiently resolved by the 3.2 arcmin beam. Mappedgalaxy spectra are shown as contour plates of position versus velocity;central beam spectra are shown for the remainder. The distributions ofspin orientations are briefly analyzed and shown to be essentiallyrandom. The distributions of H I luminosity are presented along withindicative dynamical mass for the spirals and a synthesized H Idistribution for the cluster as a whole.
| Studies of the Virgo Cluster. II - A catalog of 2096 galaxies in the Virgo Cluster area.
The present catalog of 2096 galaxies within an area of about 140 sq degapproximately centered on the Virgo cluster should be an essentiallycomplete listing of all certain and possible cluster members,independent of morphological type. Cluster membership is essentiallydecided by galaxy morphology; for giants and the rare class of highsurface brightness dwarfs, membership rests on velocity data. While 1277of the catalog entries are considered members of the Virgo cluster, 574are possible members and 245 appear to be background Zwicky galaxies.Major-to-minor axis ratios are given for all galaxies brighter than B(T)= 18, as well as for many fainter ones.
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