Probing the stellar halo of the milky way with the SEKBO RR Lyrae survey

Abstract

We investigate the steepening of the power-law slope beyond the Galactocentric radius of R ∼ 45kpc in the RR Lyrae (RRL) space density distribution found by Keller et al. They identified 2016 RRL candidates derived from the analysis of archival observations of the Southern Edgeworth-Kuiper Belt Object (SEKBO) survey. Our aim is to verify the completeness of RRLs and ultimately the space density distribution function given by Keller et al. We followed up on a subset of 137 candidates with a range of magnitudes (V ∼ 14-20) using the Faulkes Telescope (FT) database and confirmed 57 candidates as real RRLs. A cross-match between SEKBO RRL survey and Sloan Digital Sky Survey Data Release-7 (SDSS DR-7) revealed 272 RRL candidates in common. Applying the color selection criteria proposed by Ivezić et al. resulted in 193 likely RRLs. The completeness as a function of magnitude was calculated empirically from the combined set of SEKBO RRL candidates from current FT data, SDSS cross-matched data, and the Prior et al. catalog. This resulted in a spatial density distribution characterized by two power laws with a break radius R within a range between 45kpc and 50kpc, similar to the results of Keller et al. We find the power-law slopes for the inner halo as n inner = -2.78 ± 0.02 and for the outer halo as n outer = -5.0 ± 0.2. © © 2012. The American Astronomical Society. All rights reserved..