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Bulge Evolution in Face-On Spiral and Low Surface Brightness Galaxies
It is an observational fact that bulges of spiral galaxies contain ahigh fraction of old and metal-rich stars. Following this observationalfact, we have investigated the colors of 21 bulges hosted by a selectedsample of high surface brightness spiral galaxies and low surfacebrightness galaxies observed in the B and R optical bands and the J andKs near-IR bands. Using structural parameters derived fromthese observations, we obtain evidence that bulges could be formed bypure disk evolution (secular evolution), in agreement with suggestionsby some authors. The color profiles, especially the near-IR ones, shownull or almost null color gradients, supporting the hypothesis that thedisk stellar populations are similar to those present in the bulgeand/or that some bulges can be understood as disks with enhanced stellardensity (or pseudobulges). In the optical, half of the galaxies presentan inverse color gradient, giving additional evidence in favor ofsecular evolution for the sample investigated. The comparison of theobserved colors with those obtained from spectrophotometric models ofgalaxy evolution suggests that bulges of the selected sample have solarand subsolar metallicities and are independent of the current stellarformation rate. Also, we obtain evidence suggesting that galaxieshosting small bulges tend to be systematically metal-poor compared tothose with larger bulges. These results are being checked more carefullywith high signal-to-noise ratio spectroscopy.
| Circumnuclear star-forming activities along the Hubble sequence
In order to study circumnuclear star-forming activity along the Hubblesequence, we cross-correlated the Sloan Digital Sky Survey Data Release2 (SDSS DR2) with the Third Reference Catalog of Bright Galaxies (RC3)to derive a large sample of 1015 galaxies with both morphological andspectral information. Among these, 385 sources are classified asstar-forming galaxies, and the SDSS fibre covered the circumnuclearregions (0.2-2.0 kpc). By using the spectral synthesis method to removethe contribution from the underlying old stellar population, we measuredthe emission lines fluxes accurately, which are then used to estimatethe star-formation rates(SFRs). Our main findings are: (1) early-typespirals show much higher Hα luminosities, and hence higher SFRs,and also suffer more extinctions than late-type ones. The equivalentwidths (EWs) of Hα emission lines show a similar trend; however,the very late types (Sdm ~ Irr) do have large fractions of high EWs; (2)we confirm that D_n(4000) shows a strong correlation with the strengthsof metallic absorption lines (such as CN band, G band, and Mg Ib). Boththese lines and the Balmer absorption lines show interesting variationsbetween Sbc and Sd type galaxies; (3) the bar structure tightly relatesto the enhanced star formation activity, an effect that is even moresignificant in the early-type spirals. But we should note that the barstructure is not a necessary or sufficient condition for galaxies toharbor circumnuclear star formations.
| Strong Emission Line H II Galaxies in the Sloan Digital Sky Survey. I. Catalog of DR1 Objects with Oxygen Abundances from Te Measurements
We present the first edition of the SDSS H II galaxies with Oxygenabundances Catalog (SHOC), which is a listing of strong emission-linegalaxies (ELGs) from the Sloan Digital Sky Survey (SDSS). Oxygenabundances have been obtained with the classic Te method. Wedescribe the method exploiting the SDSS database to construct thissample. The selection procedures are described and discussed in detail,as well as some problems encountered in the process of deriving reliableemission line parameters. The method was applied to the SDSS DataRelease 1 (DR1). We present 612 SDSS emission-line galaxies (624separate SDSS targets in total), for which the oxygen abundances12+log(O/H) have rms uncertainties <=0.20 dex. The subsample of 263ELGs (272 separate SDSS targets) have an uncertainty <=0.10 dex,while 459 ELGs (470 separate SDSS targets) have an uncertainty <=0.15dex. The catalog includes the main parameters of all selected ELGs, theintensities and equivalent widths of hydrogen and oxygen emission lines,as well as oxygen abundances with their uncertainties. The informationon the presence of Wolf-Rayet blue and/or red bumps in 109 galaxies isalso included. With the use of combined g, r, i SDSS images we performedvisual morphological classification of all SHOC galaxies. Four hundredsixty-one galaxies (~75%) are classified as confident or probable bluecompact galaxies (BCG/BCG?), 78 as irregular ones, 20 as low surfacebrightness galaxies (LSBG), 10 as obviously interacting, and 43 asspiral galaxies. In creating the catalog, 30 narrow-line active galacticnuclei and 69 LINERs were also identified; these are also presentedapart of the main catalog. We outline briefly the content of thecatalog, and the prospects of its use for statistical studies of thestar formation and chemical evolution issues. Some of these studies willbe presented in the forthcoming paper. Finally, we show that the methodpresented by Kniazev et al. for calculating O+/H+using intensities of the [O II] λλ7320, 7330 lines forSDSS emission-line spectra in the absence of [O II] λ3727 lineappears to yield reliable results over a wide range of studied oxygenabundances: 7.10<12+log(O/H)<8.5.
| Low Surface Brightness Galaxies in the Sloan Digital Sky Survey. I. Search Method and Test Sample
In this paper we present results of a pilot study to use imaging datafrom the Sloan Digital Sky Survey (SDSS) to search for low surfacebrightness (LSB) galaxies. For our pilot study we use a test sample of92 galaxies from the Impey et al. catalog distributed over 93 SDSSfields of the Early Data Release (EDR). Many galaxies from the testsample are either LSB or dwarf galaxies. To deal with the SDSS data mosteffectively, a new photometry software was created, which is describedin this paper. We present the results of the selection algorithmsapplied to these 93 EDR fields. Two galaxies from the Impey et al. testsample are very likely artifacts, as confirmed by follow-up imaging.With our algorithms we were able to recover 87 of the 90 remaining testsample galaxies, implying a detection rate of ~96.5%. The three missedgalaxies fall too close to very bright stars or galaxies. In addition,42 new galaxies with parameters similar to the test sample objects werefound in these EDR fields (i.e., ~47% additional galaxies). We presentthe main photometric parameters of all identified galaxies and carry outfirst statistical comparisons. We tested the quality of our photometryby comparing the magnitudes for our test sample galaxies and otherbright galaxies with values from the literature. All these tests yieldedconsistent results. We briefly discuss a few unusual galaxies found inour pilot study, including an LSB galaxy with a two-component disk and10 new giant LSB galaxies.
| A search for Low Surface Brightness galaxies in the near-infrared. I. Selection of the sample
A sample of about 3800 Low Surface Brightness (LSB) galaxies wasselected using the all-sky near-infrared (J, H and Ks-band)2MASS survey. The selected objects have a mean central surfacebrightness within a 5'' radius around their centre fainter than 18 magarcsec-2 in the Ks band, making them the lowestsurface brightness galaxies detected by 2MASS. A description is given ofthe relevant properties of the 2MASS survey and the LSB galaxy selectionprocedure, as well as of basic photometric properties of the selectedobjects. The latter properties are compared to those of other samples ofgalaxies, of both LSBs and ``classical'' high surface brightness (HSB)objects, which were selected in the optical. The 2MASS LSBs have aBT_c-KT colour which is on average 0.9 mag bluerthan that of HSBs from the NGC. The 2MASS sample does not appear tocontain a significant population of red objects.All tables and Figs. 2a-c are only available in electronic form athttp://www.edpsciences.org
| 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.
| High and Low Surface Brightness Galaxies in the Local Universe. V. Optical and H I Properties
Using optical spectra of the nuclei of 250 galaxies chosen from theAutomated Plate Measuring Facility (APM) survey of UK Schmidt plates, wederive synthetic B-V and V-R colors, estimates of reddening from Balmerdecrements, metallicity via oxygen abundance, and star formation ratefrom the Hα luminosity. We also present mass-to-light ratios andgas mass fractions from 21 cm H I measurements of 238 APM surveygalaxies, 101 of which also have optical spectra. This sample ofgalaxies spans a large range in surface brightness, from high surfacebrightness irregular galaxies down to the kind of low surface brightness(LSB) galaxies that are missing from most magnitude-limited catalogs.The generally blue global colors are best explained by a combination oflow metallicity and active star formation, primarily because of thetremendous scatter in metallicity versus B-V. Optical spectra show thepresence of G and K main-sequence stars in the nuclei of these galaxies,and the stellar mass-to-light ratios and gas mass fractions show thegalaxies as a whole to be gas-rich. LSB galaxies are most likely toexperience sporadic low levels of star formation over gigayeartimescales.
| 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.
| The Southern Sky Redshift Survey
We report redshifts, magnitudes, and morphological classifications for5369 galaxies with m_B <= 15.5 and for 57 galaxies fainter than thislimit, in two regions covering a total of 1.70 sr in the southerncelestial hemisphere. The galaxy catalog is drawn primarily from thelist of nonstellar objects identified in the Hubble Space TelescopeGuide Star Catalog (GSC). The galaxies have positions accurate to ~1"and magnitudes with an rms scatter of ~0.3 mag. We compute magnitudes(m_SSRS2) from the relation between instrumental GSC magnitudes and thephotometry by Lauberts & Valentijn. From a comparison with CCDphotometry, we find that our system is homogeneous across the sky andcorresponds to magnitudes measured at the isophotal level ~26 magarcsec^-2. The precision of the radial velocities is ~40 km s^-1, andthe redshift survey is more than 99% complete to the m_SSRS2 = 15.5 maglimit. This sample is in the direction opposite that of the CfA2; incombination the two surveys provide an important database for studies ofthe properties of galaxies and their large-scale distribution in thenearby universe. Based on observations obtained at Cerro TololoInter-American Observatory, National Optical Astronomy Observatories,operated by the Association of Universities for Research in Astronomy,Inc., under cooperative agreement with the National Science Foundation;Complejo Astronomico El Leoncito, operated under agreement between theConsejo Nacional de Investigaciones Científicas de laRepública Argentina and the National Universities of La Plata,Córdoba, and San Juan; the European Southern Observatory, LaSilla, Chile, partially under the bilateral ESO-ObservatórioNacional agreement; Fred Lawrence Whipple Observatory;Laboratório Nacional de Astrofísica, Brazil; and the SouthAfrican Astronomical Observatory.
| Low Surface Brightness Galaxies in the Local Universe. I. The Catalog
Data are presented for 693 galaxies identified in a large new survey forlow surface brightness galaxies in the nearby universe (z <~ 0.1).The survey covers 786 square degrees centered on the equator, and itextends significantly the surface brightness range of galaxy surveys inwhich there are a substantial number of galaxies with redshifts. Thedata are derived from the Automated Plate Measuring machine scans ofsurvey plates from the UK Schmidt Telescope and from follow-upobservations at radio and optical wavelengths. Accurate positions, totalB magnitudes, surface brightness parameters, and angular sizes aretabulated for each galaxy. Radial velocities, optical luminosities, andneutral hydrogen masses are listed for a subset of the sample. Findingcharts are also presented for those objects having a large enoughangular size that the scans from survey plates provide somemorphological information. The selection function and the luminosityfunction that can be derived from the survey are discussed in twocompanion papers.
| An image database. II. Catalogue between δ=-30deg and δ=70deg.
A preliminary list of 68.040 galaxies was built from extraction of35.841 digitized images of the Palomar Sky Survey (Paper I). For eachgalaxy, the basic parameters are obtained: coordinates, diameter, axisratio, total magnitude, position angle. On this preliminary list, weapply severe selection rules to get a catalog of 28.000 galaxies, wellidentified and well documented. For each parameter, a comparison is madewith standard measurements. The accuracy of the raw photometricparameters is quite good despite of the simplicity of the method.Without any local correction, the standard error on the total magnitudeis about 0.5 magnitude up to a total magnitude of B_T_=17. Significantsecondary effects are detected concerning the magnitudes: distance toplate center effect and air-mass effect.
| Galaxy structures in the Hercules region
216 redshifts have been obtained in a region of 981 sq deg south of theHercules supercluster. 172 of these redshifts are of galaxies withmpg less than or equal to 15.1, 110 of which had no previousvelocity measurement. 44 new redshifts are of galaxies fainter thanmpg = 15.1. With these new data we have been able to define asample in a vast region (approximately 1700 sq deg) around Herculeslimited to mpg less than or equal to 15.1 with a velocitycompleteness of 81.5%. 189 galaxies have been morphologically classifiedso that all galaxies in the sample with known velocity now also haveknown morphology. The magnitude limited sample, including 556 galaxies,is then used to identify and describe galaxy structures in the region.We find that the overdense volume is small, that its overall appearanceis that of a coral branch floating in a sea of nothing and that earlyand late type galaxies defined different structures.
| H I observations of galaxies in between the Local and the Hydra/Centaurus superclusters
H I observations obtained with the 300-ft NRAO and 100-m Effelsbergradio telescopes in 1984-1985 are reported for 440 galaxies, ofmorphological types S0/a or later and diameter at least 2 arcmin in thecatalog of de Vaucouleurs et al., 1976, from the region between theLocal and Hya/Cen superclusters. The data are compiled in tables alongwith published data on 310 galaxies to form a data base for studies offilamentary structures in the intercluster region. More than 50 percentof the galaxies are detected in H I, and the redshift distribution isfound to be consistent with the existence of filaments.
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