AAS 202nd Meeting, May 2003
Session 40 Galaxies
Poster, Wednesday, May 28, 2003, 10:00am-6:45pm, West Exhibit Hall

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[40.08] Neighbor Galaxy Influence on the Tully-Fisher Distance Calculation and Rotation Curve Asymmetry

J. C. Hodge, M. W. Castelaz (PARI)

Calculation of distances to galaxies using the Tully-Fisher relation and Cepheid variables show differences of up to 80 of the Cepheid distance (1.2 magnitude). A model is presented relating the radiated energy of neighboring galaxies to the B-band absolute magnitude of an object galaxy. The illumination from neighboring galaxies is used to correct the Tully-Fisher distance calculation that reduces the residual between the Tully-Fisher and Cepheid distance calculations of the galaxy of interest.

Considerable effort has been spent to relate the asymmetry observed in spiral galaxy HI rotation curves with other physical parameters. The HI rotation velocity asymmetry linearly correlates with the effective potential force from the 10 closest neighboring galaxies. Also, the slope of the rotation curve in the disk region of a galaxy from rising to flat to declining is qualitatively correlated with increasing asymmetry and, hence, to the net force from other galaxies. The model suggests (1) a galaxy's dynamics and apparent luminosity are related to the energy and position of neighboring galaxies, (2) a rising rotation curve in the disk region is intrinsic, (3) flat and declining rotation curves are caused by neighboring galaxies, and (4) the ratio of intrinsic mass to intrinsic luminosity is constant among galaxies.

JCH is a member of the Aristarchus Scholars Program at PARI for Emeritus Scientists and Engineers.

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© 2003. The American Astronomical Soceity.