Astronomy and Astrophysics – Astronomy
Scientific paper
Dec 2007
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2007aas...211.3304r&link_type=abstract
American Astronomical Society, AAS Meeting #211, #33.04; Bulletin of the American Astronomical Society, Vol. 39, p.785
Astronomy and Astrophysics
Astronomy
Scientific paper
Bars play a very important role in the formation and evolution of disk galaxies. Substantial evidence exists that our own galaxy harbors a bar, providing us with an opportunity for its detailed study.
I use Fabry-Perot absorption line spectroscopy of CaII 8542 line to obtain radial velocities of about 2500 Red Clump stars in the Milky Way bar along three lines-of-sight: Baade's Window (BW) and offset positions (OP) at (l, b) = (±5.5, -3.5). Although previous studies have concentrated on BW, a stronger dynamical signature of the bar is expected at the OP. This sample is an order of magnitude larger than previous studies along a given line-of-sight, and enables us to make the first precise measurement of the higher velocity moments h3 and h4 of the bar's velocity distributions. h3 is non-zero at OP and consistent with zero in BW, exactly as expected if a bar is present. I also measured the shift in average radial velocity between the approaching and receding streams in the bar. The shift is higher at OP and negligible at BW. These high precision measurements will provide stringent constraints on Galactic bar models so that conclusions about its orientation, axis ratio and pattern speed can be made with higher confidence. Preliminary modeling results will be discussed.
I also measure the equivalent width of the CaII 8542 line and infer [Fe/H] using the calcium infrared triplet method. Our main conclusions are: (1) the Galactic bulge is a super-solar bulge, consistent with previous observations; (2) extremely high metallicity stars ([Fe/H] +1.5 dex) exist in the bulge; and (3) the mean [Fe/H] and its dispersion decrease with the galactic longitude and correlate with the line-of-sight velocity dispersion. These results will have significant impact on the chemical evolution models of the Milky Way.
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