Spiral Arms in Galaxies with Two Way (Counter-Rotating) Disks

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Session 76 -- Spiral and Bar Structure in Galaxies
Display presentation, Friday, January 14, 9:30-6:45, Salons I/II Room (Crystal Gateway)

[76.09] Spiral Arms in Galaxies with Two Way (Counter-Rotating) Disks

M.T. Carini (IUEDAC/CSC), Sethanne Howard (USRA), Gene Byrd (University of Alabama), Sandra Lester (LSU)

The Hubble type Sab Galaxy NGC 7217 has 30\% of the stars in its disk counter rotating relative to the rest (Merrifield and Kuijken, 1993). Rubin's (1993) observation of a similar disk in NGC 4550 and the discovery of a counter rotating gas disk in the Black Eye Galaxy (Van Driel and Buta, 1993) raises the question as to whether there is any obvious signature of a substantial counter rotating disk. If such a signature could be found, it would be possible to better estimate how common such disk galaxies might be. Since 1/3 of disk galaxies are currently being tidally perturbed at a level sufficient to create a global spiral arm pattern with an undoubtedly larger total fraction perturbed within the arm lifetime (Byrd and Howard, 1992), the appearance of tidal arms in two way , partly counter rotating disks versus those in normal one way disks should be studied and could serve as such a signature. We have simulated tidal perturbations of galaxies with one way disks compared to galaxies with 50/50 two way disks. We have also studied the behavior of isolated disks with varying amounts of halo relative to the disk.

Friday program listing