J/ApJS/106/27 Spiral galaxies in pairs (Keel, 1996)
Rotation curves and velocity measures for spiral galaxies in pairs
Keel W.C.
<Astrophys. J. Suppl. Ser. 106, 27 (1996)>
=1996ApJS..106...27K 1996ApJS..106...27K
ADC_Keywords: Galaxies, rotation
Keywords: galaxies: distances and redshifts -
galaxies: kinematics and dynamics - galaxies: Seyfert -
galaxies: spiral
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.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table2a 38 52 Galaxy pair parameters
table2b 45 3250 Velocity curves for galaxy pairs
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See also:
VII/77 : Catalog of Pairs of Galaxies (CPG) (Karachentsev+ 1972)
Byte-by-byte Description of file: table2a
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Bytes Format Units Label Explanations
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1- 8 A8 --- CPG CPG (Cat. VII/77) name
10- 18 A9 --- Name Other name
20- 22 A3 --- n_CPG [abs] absorption
24- 26 I3 deg PA Position angle
28- 32 F5.1 km/s HVcorr Correction to heliocentric velocity
34- 38 F5.1 --- Peak Adopted location along the slit from the
continuum peak
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Byte-by-byte Description of file: table2b
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Bytes Format Units Label Explanations
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1- 8 A8 --- CPG CPG (Cat. VII/77) name
10- 12 I3 pix Pixel *Pixel number along the slit
14- 20 F7.1 km/s Vobs Weighted mean velocity in the relativistic
convention
22- 27 F6.1 km/s e_Vobs 2-sigma error derived from photon statistics
29- 36 F8.1 --- Halpha *Total Halpha intensity
38- 43 F6.1 --- Cont Continuum intensity
45 I1 --- Lines Number of emission lines measured
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Note on 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).
Note on Halpha:
Total H-alpha intensity in instrumental units (neglecting the
broad-line component where it can be distinguished).
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Origin: AAS CD-ROM series, Volume 7, 1996 Lee Brotzman [ADS] 09-Oct-96
(End) Patricia Bauer [CDS] 03-Feb-1997