VISTA's view of the Sgr dSph galaxy and southern Galactic Bulge

I. McDonald (Univ. Manchester), A.A. Zijlstra (Univ. Manchester), G.C. Sloan (Cornell), E. Kerins (Univ. Manchester), E. Lagadec (Cornell), D. Minniti (Pontifica Univ. Catolica de Chile), S. Gurovich (Cordoba, Argentina), M.J.de L. Dominguez Romero (Cordoba, Argentina), and V. Santucho (Cordoba, Argentina)

2013, MNRAS, 436, 413

We present the deepest near-infrared (ZJK_s) photometry yet obtained of the Sgr dSph, using VISTA to survey 11 square degrees centred on its core. We list locations and ZJK_s-band magnitudes for over 2.9 million sources in the field. We discuss the isolation of the Sgr dSph from the foreground and Galactic Bulge populations, identify the Sgr dSph's horizontal branch, and map the density of its stars. We fit isochrones to the Sgr dSph and Bulge populations. The properties of the Sgr dSph core are confirmed: it is spheroidal in shape, lies at 25 ± ~1 kpc distance, and is dominated by a metal-poor (-0.7 ~< [Fe/H] ~< -0.4 dex) population at an implied age of ~<9 Gyr, but with a metal-rich tail to the distribution. The previously reported possible density enhancement in the direction of the Galactic Centre appears weakly present, but contamination from the Galactic Bulge prevents accurate measurement of structures. The Bulge population is best fit by a younger population with [Fe/H] ~ 0 and [alpha/Fe] ~ 0. We find no evidence for a split, peanut- or X-shaped Bulge population in this line of sight (l = 5.6° ± ~ 1°, b = -14.1° ± ~3°).

Home Library

Last modified 13 November, 2013. © Gregory C. Sloan and others.