Journal Article

Detection of satellite remnants in the Galactic Halo with <i>Gaia</i> – II. A modified great circle cell method

C. Mateu, G. Bruzual, L. Aguilar, A. G. A. Brown, O. Valenzuela, L. Carigi, H. Velázquez and F. Hernández

in Monthly Notices of the Royal Astronomical Society

Published on behalf of The Royal Astronomical Society

Volume 415, issue 1, pages 214-224
Published in print July 2011 | ISSN: 0035-8711
Published online July 2011 | e-ISSN: 1365-2966 | DOI: http://dx.doi.org/10.1111/j.1365-2966.2011.18690.x
Detection of satellite remnants in the Galactic Halo with Gaia – II. A modified great circle cell method

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We propose an extension of the great circle cell count streamer finding method of Johnston et al. that can be applied to the future Gaia data base. The original method looks for streamers along great circles in the sky, our extension adds the kinematical restriction that velocity vectors should also be constrained to lie along these great circles, as seen by a Galactocentric observer. We show how to use these combined criteria starting from heliocentric observables. We test it by using the mock Gaia catalogue of Brown et al., which includes a realistic Galactic background and observational errors, but with the addition of detailed star formation histories for the simulated satellites. We investigate its success rate as a function of initial satellite luminosity, star formation history and orbit. We find that the inclusion of the kinematical restriction vastly enhances the contrast between a streamer and the background, even in the presence of observational errors, provided we use only data with good astrometric quality (fractional errors of 30 per cent or better). The global nature of the method diminishes the erasing effect of phase mixing and permits the recovery of merger events of reasonable dynamical age. Satellites with a star formation history different to that of the Galactic background are also better isolated. We find that satellites in the range of 108–109 L can be recovered even for events as old as ∼10 Gyr. Even satellites with 4–5 × 107 L can be recovered for certain combinations of dynamical ages and orbits.

Keywords: methods: numerical; Galaxy: formation; Galaxy: structure; galaxies: interactions

Journal Article.  8911 words.  Illustrated.

Subjects: Astronomy and Astrophysics

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