RR Lyrae in XSTPS: The Halo Density Profile in the North Galactic Cap

TitleRR Lyrae in XSTPS: The Halo Density Profile in the North Galactic Cap
Publication TypeJournal Article
Year of Publication2014
AuthorsFaccioli, L, Smith, M C, Yuan, H-B, Zhang, H-H, Liu, X-W, Zhao, H-B, Yao, J-S
KeywordsGalaxy: halo, Galaxy: stellar content, Galaxy: structure, stars: variables: RR Lyrae, surveys, techniques: photometric

{We present a catalog of RR Lyrae stars (RRLs) observed by the Xuyi Schmidt Telescope Photometric Survey (XSTPS). The area we consider is located in the north Galactic cap, covering {\ap}376.75 deg$^{2}$ at {$\alpha$} {\ap} 150{\deg} and {$δ$} {\ap} 27{\deg} down to a magnitude limit of i {\ap} 19. Using the variability information afforded by the multi-epoch nature of our XSTPS data, combined with colors from the Sloan Digital Sky Survey, we are able to identify candidate RRLs. We find 318 candidates, derive distances to them, and estimate the detection efficiency. The majority of our candidates have more than 12 observations, and for these we are able to calculate periods. These also allow us to estimate our contamination level, which we predict is between 30% and 40%. Finally, we use the sample to probe the halo density profile in the 9-49 kpc range and find that it can be well fitted by a double power law. We find good agreement between this model and the models derived for the south Galactic cap using the Watkins et al. and Sesar et al. RRL data sets, after accounting for possible contamination in our data set from Sagittarius stream members. We consider non-spherical double power-law models of the halo density profile and again find agreement with literature data sets, although we have limited power to constrain the flattening due to our small survey area. Much tighter constraints will be placed by current and future wide-area surveys, most notably ESA's astrometric Gaia mission. Our analysis demonstrates that surveys with a limited number of epochs can effectively be mined for RRLs. Our complete sample is provided as accompanying online material; as an example the first few entries of each electronic table are shown in the text. }