Computer Science
Scientific paper
Aug 2003
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2003phdt.........7p&link_type=abstract
Thesis (PhD). UNIVERSITY OF MINNESOTA, Source DAI-B 64/02, p. 765, Aug 2003, 184 pages.
Computer Science
Scientific paper
We present both a star count and a kinematic analysis using data from 40 (×2) Automated Plate Scanner POSS-I plate pairs matched in galactic latitude at complementary longitudes, and the spectra of nearly 1000 stars using the HYDRA multi-object spectrometer at both CTIO and KPNO. We have identified a region with a significant excess of stars in Quadrant I above (+Q1) and below (-Q1) the galactic plane. The asymmetric distributution of stars consists of 20 contiguous POSS-I fields extending from l = 20° 55° and |b| = 20° 50° and is symmetric above and below the galactic plane. We are unable to discriminate between thick disk or inner halo stars, however there appear to be more blue stars in +Q1 with LSR velocities suggestive of a thick disk population. We compare the LSR radial velocity distributions for a total of 752 stars in Quadrant I to Quadrant IV (+Q4), above the plane. Stars in +Q1 appear to have a more negative distribution of LSR radial velocities than stars in +Q4; additionally we calculate the circular angular velocities and find that ω+Q1 = 9.5 ± 0.3 km/s/kpc is rotating four × slower ω +Q4 = 36.2 ± 0.1 km/s/kpc. Preliminary N-body simulations by Sellwood and Debattista (2003) reproduce both our excess in star counts and the negative LSR velocity signatures only if the models include a stellar bar in the disk and an asymmetric thick disk. The star count excess we find in Q1 along with the significantly slower circular angular velocity suggests that the thick disk may be interacting with the stellar bar in the disk. This interaction is likely inducing a gravitational wake which is trapping and piling up stars behind the bar.
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