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A catalog of edge-on disk galaxies. From galaxies with a bulge to superthin galaxies
Spiral galaxies range from bulge-dominated early-type galaxies to latetypes with little or no bulge. Cosmological models do not predict theformation of disk-dominated, essentially bulgeless galaxies, yet theseobjects exist. A particularly striking and poorly understood example ofbulgeless galaxies are flat or superthin galaxies with large axisratios. We therefore embarked on a study aimed at a better understandingof these enigmatic objects, starting by compiling a statisticallymeaningful sample with well-defined properties. The disk axis ratios canbe most easily measured when galaxies are seen edge-on. We used datafrom the Sloan Digital Sky Survey (SDSS) in order to identify edge-ongalaxies with disks in a uniform, reproducible, automated fashion. Inthe five-color photometric database of the SDSS Data Release 1 (2099deg^2) we identified 3169 edge-on disk galaxies, which we subdividedinto disk galaxies with bulge, intermediate types, and simple diskgalaxies without any obvious bulge component. We subdivided these typesfurther into subclasses: Sa(f), Sb(f), Sc(f), Scd(f), Sd(f), Irr(f),where the (f) indicates that these galaxies are seen edge-on. Here wepresent our selection algorithm and the resulting catalogs of the 3169edge-on disk galaxies including the photometric, morphological, andstructural parameters of our targets. A number of incompleteness effectsaffect our catalog, but it contains almost a factor of four morebulgeless galaxies with prominent simple disks (flat galaxies) withinthe area covered here than previous optical catalogs, which were basedon the visual selection from photographic plates (cf. Karachentsev etal. 1999, Bull. Special Astrophys. Obs., 47, 5). We find thatapproximately 15% of the edge-on disk galaxies in our catalog are flatgalaxies, demonstrating that these galaxies are fairly common,especially among intermediate-mass star-forming galaxies. Bulgelessdisks account for roughly one third of our galaxies when also puffydisks and edge-on irregulars are included. Our catalog provides auniform database for a multitude of follow-up studies of bulgelessgalaxies in order to constrain their intrinsic and environmentalproperties and their evolutionary status.
| Rotational Widths for Use in the Tully-Fisher Relation. I. Long-Slit Spectroscopic Data
We present new long-slit Hα spectroscopy for 403 noninteractingspiral galaxies, obtained at the Palomar Observatory 5 m Hale telescope,which is used to derive well-sampled optical rotation curves. Becausemany of the galaxies show optical emission features that aresignificantly extended along the spectrograph slit, a technique wasdevised to separate and subtract the night sky lines from the galaxyemission. We exploit a functional fit to the rotation curve to identifyits center of symmetry; this method minimizes the asymmetry in thefinal, folded rotation curve. We derive rotational widths using bothvelocity histograms and the Polyex model fit. The final rotational widthis measured at a radius containing 83% of the total light as derivedfrom I-band images. In addition to presenting the new data, we use alarge sample of 742 galaxies for which both optical long-slit and radioH I line spectroscopy are available to investigate the relation betweenthe H I content of the disks and the extent of their rotation curves.Our results show that the correlation between those quantities, which iswell established in the case of H I-poor galaxies in clusters, ispresent also in H I-normal objects: for a given optical size, starformation can be traced farther out in the disks of galaxies with largerH I mass.
| 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.
| Galaxy coordinates. II. Accurate equatorial coordinates for 17298 galaxies
Using images of the Digitized Sky Survey we measured coodinates for17298 galaxies having poorly defined coordinates. As a control, wemeasured with the same method 1522 galaxies having accurate coordinates.The comparison with our own measurements shows that the accuracy of themethod is about 6 arcsec on each axis (RA and DEC).
| A redshift survey toward a proposed void of galaxies suggested by the distribution of Abell clusters
A program of redshift measurements was carried out in a region of thesky in which a relative under-density of Abell clusters had been used toinfer the presence of a large (diameter about 40/h Mpc) void in thegeneral galaxy distribution. The purpose of this study was toinvestigate whether the large-scale distribution of galaxies is tracedby the distribution of rich clusters. Redshifts are presented for 308galaxies in the Zwicky Catalog in a 234 square degree region centered onR.A. about 2h, Decl. about 12 deg of which 229 have been newly measured.These data reveal a pattern of filamentary structure alternating withvoids of characteristic diameter about 25-30/h Mpc, throughout thevolume sampled. While the redshift data reveal an underdensity in thedistribution of galaxies in the general region suggested by the Abellcluster distribution, they do not support the existence there of a 40/hMpc diameter void.
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