2012/08/31 by David M. Nataf, Andrew Gould, Pascal Fouqué +11 · 1 citation
Physics and Astronomy · #astro-ph.GA
paper · pdf · doi:10.1088/0004-637x/769/2/88
61 Pages, 21 Figures, 4 Tables, Submitted to The Astrophysical Journal and modified as per a referee report. Includes reddening, reddening law, differential reddening, mean distance, dispersion in distance, surface density of stars and errors thereof for ~9,000 bulge sightlines. For a brief video explaining the key result of this paper, see http://www.youtube.com/user/OSUAstronomy
arxiv created 2013/03/14 · arxiv updated 2015/06/11
We combine VI photometry from OGLE-III with VVV and 2MASS measurements of E(J-Ks) to resolve the longstanding problem of the non-standard optical extinction toward the Galactic bulge. We show that the extinction is well-fit by the relation AI = 0.7465*E(V-I) + 1.3700*E(J-Ks), or, equivalently, AI = 1.217*E(V-I)(1+1.126*(E(J-Ks)/E(V-I)-0.3433)). The optical and near-IR reddening law toward the inner Galaxy approximately follows an RV ≈ 2.5 extinction curve with a dispersion σ_RV ≈ 0.2, consistent with extragalactic investigations of the hosts of type Ia SNe. Differential reddening is shown to be significant on scales as small as as our mean field size of 6', with the 1σ dispersion in reddening averaging 9% of total reddening for our fields. The intrinsic luminosity parameters of the Galactic bulge red clump (RC) are derived to be (MI,RC, σI,RC,0, (V-I)RC,0, σ_(V-I)RC, (J-Ks)RC,0) = (-0.12, 0.09, 1.06, 0.121, 0.66). Our measurements of the RC brightness, brightness dispersion and number counts allow us to estimate several Galactic bulge structural parameters. We estimate a distance to the Galactic center of 8.20 kpc, resolving previous discrepancies in distance determinations to the bulge based on I-band observations. We measure an upper bound on the tilt α ≈ 40°. between the bar's major axis and the Sun-Galactic center line of sight, though our brightness peaks are consistent with predictions of an N-body model oriented at α ≈ 25°. The number of RC stars suggests a total stellar mass for the Galactic bulge of 2.0*1010 M\odot, if one assumes a Salpeter IMF.