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The Photometric and Kinematic Structure of Face-on Disk Galaxies. II. Integrated Line Profile Characterization and the Origin of Line Profile Asymmetry
We perform a moments analysis of H I and H II global line profiles for33 nearly face-on disk galaxies for the threefold purpose ofrationalizing and interpreting line profile indices in the literature,presenting robust moment definitions with analytic error functionscalibrated against Monte Carlo simulation, and probing the physicalorigin of line profile asymmetries. The first four profile moments serveas viable surrogates for the recession velocity, line width, asymmetry,and profile shape, respectively. The first three moments are superior,by a factor of ~2 in precision, to related quantities defined in theliterature. First and third profile moments are related; skew can beused to calculate more accurate recession velocities from globalprofiles. Second and fourth profile moments are linked, corresponding tothe known trend that narrow (but well resolved) line widths tend to bemore Gaussian. Hα kurtosis also appears correlated with thespatially resolved line width of the ionized gas. No systematics appearbetween various measures of line width and true rotation speed otherthan the wide range of normalizations, which we calibrate. Thisconclusion and calibration, however, is highly sample dependent. Theratio of H II to H I widths is consistent with unity, even at lowprojected line width. There may be a trend toward a decrease in theratio of H II to H I widths consistent with previous studies, but wealso observe greater scatter. While there is good agreement between H Iand H II first, second, and fourth moments, we find no positivecorrelation between skew measured from H I and H II profiles. Detailedanalysis of the spatially resolved Hα distribution demonstratesthat H II global profile asymmetries are dominated by differences in thegas distribution, not kinematic asymmetries.
| 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.
| 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.
| A Measurement of Disk Ellipticity in Nearby Spiral Galaxies
We have measured the intrinsic disk ellipticity for seven nearby, nearlyface-on spiral galaxies by combining Densepak integral-fieldspectroscopy with I-band imaging from the WIYN telescope. Initiallyassuming an axisymmetric model, we determine the kinematic inclinationsand position angles from Hα velocity fields and the photometricaxis ratios and position angles from imaging data. We interpret theobserved disparities between kinematic and photometric disk parametersin terms of an intrinsic nonzero ellipticity ɛ. The meanellipticity of our sample is 0.05. If the majority of disk galaxies havesuch intrinsic axis ratios, this would account for roughly 50% of thescatter in the Tully-Fisher relation. This result, in turn, placestighter constraints on other sources of scatter in this relation, themost astrophysically compelling of which is galaxy mass-to-light ratios.
| 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.
| KISO survey for ultraviolet-excess galaxies. VI.
Not Available
| Radial velocities of galaxies in the neighborhood of groups of galaxies. III
New determinations of the radial velocities for 31 galaxies in theneighborhood of groups of galaxies are reported. The observations aredescribed, and data are given for the galaxies in a table, including thenumber of spectra used, the radial velocity of each galaxy corrected forthe motion of the sun and the earth, the internal error in themeasurement, estimates of the quality of the spectra, the spectral linesused in the calculation of the velocities, the radial velocitiesdetermined by other authors, and the membership of the objects ingalactic systems. The data from other authors are used to determine thereal (external) accuracy of the present determinations, and goodagreement is found.
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