Abstract
We present a new approach for identifying the tip of the red giant
branch (TRGB) which, as we show, works robustly even on sparsely
populated targets. Moreover, the approach is highly adaptable to the
available data for the stellar population under study, with prior
information readily incorporable into the algorithm. The uncertainty in
the derived distances is also made tangible and easily calculable from
posterior probability distributions. We provide an outline of the
development of the algorithm and present the results of tests designed
to characterize its capabilities and limitations. We then apply the new
algorithm to three M31 satellites: Andromeda I, Andromeda II, and the
fainter Andromeda XXIII, using data from the Pan-Andromeda
Archaeological Survey (PAndAS), and derive their distances as 731(+
5) + 18 (- 4) - 17 kpc, 634(+ 2) +
15 (- 2) - 14 kpc, and 733(+ 13) +
23 (- 11) - 22 kpc, respectively, where the
errors appearing in parentheses are the components intrinsic to the
method, while the larger values give the errors after accounting for
additional sources of error. These results agree well with the best
distance determinations in the literature and provide the smallest
uncertainties to date. This paper is an introduction to the workings and
capabilities of our new approach in its basic form, while a follow-up
paper shall make full use of the method's ability to incorporate priors
and use the resulting algorithm to systematically obtain distances to
all of M31's satellites identifiable in the PAndAS survey area.
Original language | English |
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Pages (from-to) | 69 |
Journal | Astrophysical Journal |
Volume | 740 |
DOIs | |
Publication status | Published - 1 Oct 2011 |