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The Photometric and Kinematic Structure of Face-on Disk Galaxies. I. Sample Definition, Hα Integral Field Spectroscopy, and H I Line Widths
We present a survey of the photometric and kinematic properties of 39nearby, nearly face-on disk galaxies. Our approach exploitsechelle-resolution integral-field spectroscopy of the Hα regions,obtained with DensePak on the WIYN 3.5 m telescope Bench Spectrograph.These data are complemented by H I line profiles observed with theNançay radio telescope for 25 of these sample galaxies. Twelveadditional line widths are available for sample galaxies from theliterature. In this paper, we introduce the goals of this survey, definethe sample selection algorithm, and amass the integral fieldspectroscopic data and H I line widths. We establish spatiallyintegrated Hα line widths for the sample. We test the veracity ofthese spatially integrated line profiles by convolving narrowbandimaging data with velocity field information for one of the samplegalaxies, PGC 38268, and also by comparing to H I line profiles. We findH I and Hα line profiles to be similar in width but different inshape, indicating that we are observing different spatial distributionsof ionized and neutral gas in largely axisymmetric systems with flatouter rotation curves. We also find vertical velocity dispersions of theionized disk gas within several disk scale lengths have a median valueof 18 km s-1 and an 80% range of 12-26 km s-1.This is only a factor of ~2 larger than what is observed for neutralatomic and molecular gas. With standard assumptions for intrinsic andthermal broadening for Hα, this translates into a factor of 3range in turbulent velocities, between 8 and 25 km s-1.
| A Face-on Tully-Fisher Relation
We construct the first ``face-on'' Tully-Fisher (TF) relation for 24galaxies with inclinations between 16° and 41°. The enablingmeasurements are integral-field echelle spectroscopy from the WIYN 3.5 mtelescope, which yield accurate kinematic estimates of disk inclinationto ~15°. Kinematic inclinations are of sufficient accuracy that ourmeasured TF scatter of 0.42 mag is comparable to other surveys evenwithout internal absorption corrections. Three of four galaxies withsignificant kinematic and photometric asymmetries also have the largestdeviations from our TF relation, suggesting that asymmetries make animportant contribution to TF scatter. By measuring inclinations below40°, we establish a direct path to linking this scatter to theunprojected structure of disks and making nondegenerate dynamical massdecompositions of spiral 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.
| 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.
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