2005/08/15 by R. A. Benjamin, Robert A. Benjamin, E. Churchwell +20 · 6 citations
Physics and Astronomy · #Astronomy and Astrophysical Research #Astrophysics and Star Formation Studies #Stellar, planetary, and galactic studies #astro-ph
paper · pdf · doi:10.1086/491785
published as Astrophys.J.630:L149-L152,2005 · Accepted for publication in Astrophysical Journal Letters. Version with full res figures and info on GLIMPSE Point Source Catalog at http://www.astro.wisc.edu/glimpse
arxiv created 2005/08/15 · openalex publication_date 2005/08/19 · arxiv updated 2009/12/01 · openalex created_date 2016/06/24 · openalex updated_date 2026/07/31
The GLIMPSE (Galactic Legacy Mid-Plane Survey Extraordinaire) Point Source Catalog of ~30 million mid-infrared sources toward the inner Galaxy, 10° ≤ | l | ≤ 65° and | b | ≤ 1°, was used to determine the distribution of stars in Galactic longitude, l , latitude, b , and apparent magnitude, m . The counts versus longitude can be approximated by the modified Bessel function N = N 0 ( l / l 0 ) K 1 ( l / l 0 ), where l 0 is insensitive to limiting magnitude, band choice, and side of Galactic center: l 0 = 17°-30° with a best-fit value in the 4.5 μm band of l 0 = 24° ± 4°. Modeling the source distribution as an exponential disk yields a radial scale length of H * = 3.9 ± 0.6 kpc. There is a pronounced north-south asymmetry in source counts for | l | ≲ 30°, with ~25% more stars in the north. For l = 10°-30°, there is a strong enhancement of stars of m = 11.5-13.5 mag. A linear bar passing through the Galactic center with half-length R bar = 4.4 ± 0.5 kpc, tilted by ϕ = 44° ± 10° to the Sun-Galactic center line, provides the simplest interpretation of these data. We examine the possibility that enhanced source counts at l = 26°-28°, 31 5-34°, and 306°-309° are related to Galactic spiral structure. Total source counts are depressed in regions where the counts of red objects ( m K - m [8.0] > 3) peak. In these areas, the counts are reduced by extinction due to molecular gas, high diffuse backgrounds associated with star formation, or both.