科研之友
微信
新浪微博
Facebook
分享链接
摘要
We present the results of a deep, wide-area variability survey in the Southern hemisphere, the first of its kind. As part of the Catalina Sky Surveys, the Siding Spring Survey (SSS) has covered 14 800 deg(2) in the declination range of -75 degrees <= delta <= -15 degrees. To mine the enormous SSS data set efficiently, we have developed two algorithms: automatic period selection (APS) and automatic Fourier decomposition (AFD), which aim to sharpen the period estimation and produce robust light-curve models. Armed with the APS and AFD outputs, we classify 10 540 ab-type RR Lyrae (RRab) stars (similar to 90 per cent of which are new) across the southern sky. As well as the positional information we supply photometric metallicities, and unreddened distances. For the RRab stars in the halo, a study of the photometric metallicity distribution reveals a nearly Gaussian shape with a mean metallicity of [Fe/H]= -1.4 dex and a dispersion of 0.3 dex. A spatial study of the RRab metallicities shows no significant radial gradient in the first similar to 7 kpc from the Galaxy centre. However, further out, a small negative gradient is clearly present. This is complemented by a very obvious correlation of the mean RR Lyrae metallicity with distance above the Galactic plane, z. We have also carried out an initial sub-structure search using the discovered RRab, and present the properties of the candidates with significance greater than 2 sigma. Most prominent among these is a southern extension of the Sagittarius dwarf galaxy's stream system, reaching down to declinations similar to -40 deg.
- 出版日期2015-1-21
