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HI LINEWIDTHS, ROTATION VELOCITIES AND THE TULLY-FISHER RELATION
이명현,Adrick H. Broeils 한국우주과학회 2005 Journal of Astronomy and Space Sciences Vol.22 No.2
We determine the rotation velocities of 108 spiral and irregular galaxies (XV-Sample)fromrst-orderrotationcurvesfromposition-velocitymaps, basedonshort21-cmob-servations with the Westerbork Synthesis Radio Telescope (WSRT). To test the usualrandommotioncorrections, we comparethe global HI linewidths and the rotationve-locities, obtainedfrom kinematicalts to two-dimensionalvelocity elds for a sampleof 28 galaxies (RC-Sample), and nd that the most frequently used correction formu-lae (Tully & Fouqu´e 1985) are not very satisfactory. The rotation velocity parameter(the random-motion corrected HI linewidth:... ), derived with these corrections,may be statistically equal to two times the true rotation velocity, but in individualcases the differences can be large. We analyse, for both RC- and XV-Samples, thedependence of the slope of, and scatter in the Tully-Fisher relation on the denitionof the rotation velocity parameters. For the RC-Sample, we nd that the scatter inthe Tully-Fisher relation can be reduced considerably when the rotation velocities de-rived from rotation curves are used instead of the random-motioncorrected global HIlinewidths. No such reduction in the scatter is seen for XV-Sample. We conclude thatthe reduction of the scatter in the Tully-Fisher relation seems to be related to the useof two-dimensional velocity information: accurate rotation velocity and kinematicalinclination.