A Pair of Bootes: A New Milky Way Satellite

S. M. Walsh; H. Jerjen; B. Willman

doi:10.1086/519684

paper

A Pair of Bootes: A New Milky Way Satellite

arXiv:0705.1378 · doi:10.1086/519684

Abstract

As part of preparations for a southern sky search for faint Milky Way dwarf galaxy satellites, we report the discovery of a stellar overdensity in the Sloan Digital Sky Survey Data Release 5, lying at an angular distance of only 1.5 degrees from the recently discovered Bo{ö}tes dwarf. The overdensity was detected well above statistical noise by employing a sophisticated data mining algorithm and does not correspond to any catalogued object. Overlaid isochrones using stellar population synthesis models show that the color-magnitude diagram of that region has the signature of an old (12 Gyr), metal-poor ( $Fe/H \approx - 2.0$ ) stellar population at a tentative distance of 60 kpc, evidently the same heliocentric distance as the Boötes dwarf. We estimate the new object to have a total magnitude of $M_{V} \sim - 3.1 \pm 1.1$ mag and a half-light radius of $r_{h} = 4^{'} .1 \pm 1^{'} .6$ ( $72 \pm 28$ pc) placing it in an apparent $40 < r_{h} < 100$ pc void between globular clusters and dwarf galaxies, occupied only by another recently discovered Milky Way Satellite, Coma Berenices.

Accept by ApJL May 9, 2007

A Pair of Bootes: A New Milky Way Satellite

Abstract

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