CDROM/APJS/V106/P027 Spiral Galaxies in Pairs (Keel 1996) ================================================================================ Rotation Curves and Velocity Measures for Spiral Galaxies in Pairs Willam C. Keel <1996, ApJS, 106, 27> =1996ApJS..107...27K ================================================================================ Abstract: Rotation curves have been obtained for 76 spiral galaxies in pairs, including a geometrically selected subset from the Karachentsev catalog and a set of Seyfert galaxies with close companions. Derived parameters of the rotation curves and the galaxies' light distributions are also presented. The rotation curves are classified broadly by shape, with special emphasis on kinematic disturbances and regions of solid-body behavior that may lead to bar development. Broadband images of the galaxies allow assessments of their degree of symmetry or disturbance. These velocity slices afford an empirical basis for evaluating the accuracy of radial velocity measures for spiral galaxies in pairs, and the dynamically important radial velocity differences. Specifically, the disagreement among several plausible ways of estimating the central velocity from these rotation data is used to estimate how closely any of these might approximate the nuclear or center-of-mass values. From seven indicators of central velocity, the internal scatter is delta_vv = 34 km/s. Of these, the velocity weighted by Halpha intensity along the slit shows a systematic offset of about 20 km/s with respect to the others for the Karachentsev pairs, in the sense that this measure is redshifted with respect to the other indicators. This is in the sense (but not of the total magnitude) required to account for statistical asymmetries in pair velocity differences. Individual scatter between the velocity indicators taken pairwise ranges from delta = 20 to 52 km/s. These results imply that emission-line data such as these cannot specify the center of mass or nuclear redshift at a level more accurate than this, even for arbitrarily precise velocity measurements, because it is not clear how the observed quantities relate to the desired measurement in a physical sense. No useful predictor of which galaxies have large or small scatter among velocity measures was found, except that the scatter is small for the class of "nonrotating" galaxies with small overall velocity amplitudes. Projected separation, separation normalized to disk scale length, and morphological disturbance do not correlate with velocity scatter. Keywords: galaxies: distances and redshifts -- galaxies: kinematics and dynamics -- galaxies: Seyfert -- galaxies: spiral Description: The table described below has header records containing information about each galaxy pair, followed by the velocity-splice measures, as shown in Figure 1 of the printed paper. As such, the table is not in a format that can be easily converted to FITS format. For each galaxy pair, four header records are given listing, in this order: Catalog of Pairs of Galaxies (CPG) number; position angle; correction to heliocentric velocity; and adopted location along the slit from the continuum peak. Following the four header records are the velocity-splice measures, which are documented below. Finally a single blank line separates the data for one galaxy pair from the next. File Summary: -------------------------------------------------------------------------------- File Name Lrecl Records Explanations -------------------------------------------------------------------------------- table2.dat 52 3509 Velocity curves for galaxy pairs -------------------------------------------------------------------------------- Byte-per-byte Description of file: table2.dat -------------------------------------------------------------------------------- Bytes Format Units Label Explanations -------------------------------------------------------------------------------- ----- Format of first four header records ----- 1-52 A52 --- Header Header record, see description above ----- Format of velocity-splice measures ----- 1- 4 I4 pix Pixel *Pixel number along the slit 5- 9 5X --- --- Blank 10-16 F7.1 km/s vobs Weighted mean velocity in the relativistic convention 17-19 3X --- --- Blank 20-25 F6.1 km/s e_vobs 2-sigma error derived from photon statistics 26-28 3X --- --- Blank 29-36 F8.1 --- Halpha *Total Halpha intensity 37-42 6X --- --- Blank 43-47 F5.1 --- Cont Continuum intensity 48-51 4X --- --- Blank 52 I1 --- Lines Number of emission lines measured -------------------------------------------------------------------------------- Notes for file: table2.dat -------------------------------------------------------------------------------- Pixel: Pixel number along the slit, at a scale of 0.78 arcsecond/pixel. The slices are along the position angles indicated in the header records. Smaller pixel numbers are at the eastern end of the slit (that is, NNE for PA 10 degrees, SSE at PA 170). Halpha: Total H-alpha intensity in instrumental units (neglecting the broad-line component where it can be distinguished). -------------------------------------------------------------------------------- ================================================================================ (End) Lee Brotzman [ADS] 09-Oct-96