The Galactic Thick Disc density profile traced with RR Lyrae stars [GA]

http://arxiv.org/abs/1802.07798


We used a combination of public RR Lyrae star catalogs and a Bayesian methodology to derive robust structural parameters of the inner Halo (<25 kpc) and Thick Disc of the Milky Way. RR Lyrae stars are an unequivocal tracer of old metal-poor populations, for which accurate distances and extinctions can be individually estimated and so, are a reliable independent means of tracing the population of the old high-[\alpha/Fe] disc usually associated to the Thick Disc. In particular, the chosen RR Lyrae sample spans regions at low galactic latitude toward the anti-center direction, allowing to probe the outermost parts of the disc. Our results favour a Thick Disc with short scale height and short scale length, $h_z=0.65_{-0.05}^{+0.09}$ kpc, $h_R=2.1_{-0.25}^{+0.82}$ kpc, for a model in which the inner Halo has a constant flattening of $q=0.90_{-0.03}^{+0.05}$ and a power law index of $n=-2.78_{-0.05}^{+0.05}$. Similar short scales for the Thick Disc are also found when considering a inner Halo with flattening dependent on radius. We also explored a model in which the Thick Disc has a flare and, although this is only mildly constrained by our data, a flare onset in the inner $\sim11$ kpc is highly disfavoured.

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C. Mateu, A. Vivas, CIDA. , et. al.
Fri, 23 Feb 18
51/64

Comments: 14 pages, 8 figures. Submitted to MNRAS