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FOSSILs in the Galactic Halo

Grillmair, Carl J. (2019) FOSSILs in the Galactic Halo. In: Dwarf Galaxies: From the Deep Universe to the Present. Proceedings of the International Astronomical Union. Vol.14. No.344. Cambridge University Press , Cambridge, pp. 73-76.

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We use a matched filter to detect compact groups of old, metal-poor stars that we term FOSSILs (Fragments of Old Stellar Systems in Limbo). With size scales on the order of 10 arcminutes, distances ranging from 2 to 200 kpc, and memberships ranging from a handful to several dozen stars, these FOSSILs stand out from the surrounding field and are presumably signatures of, or debris from, ancient star clusters and dwarf galaxies. They may be localized concentrations of stars within more extensive tidal streams, and in some cases may be the signatures of extant but heretofore undetected ultrafaint galaxies. Using magnitudes and colors from the Pan-STARRs survey, we detect ∼70 such FOSSILs at 5σ or greater in a 2200 square degree region in the vicinity of the north Galactic pole. A subsample of more populous FOSSILs that could be candidate ultrafaint dwarf galaxies suggests a total population of 200 such objects within 200 kpc of the Galactic center. Spectroscopic and astrometric follow-up of these FOSSILs will be required to determine the nature of these structures, deepen our understanding of the make-up and accretion history of the Galactic halo, and perhaps alleviate the missing satellites problem.

Item Type:Book Section
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Grillmair, Carl J.0000-0003-4072-169X
Additional Information:© 2019 International Astronomical Union. Published online by Cambridge University Press: 30 October 2019.
Group:Infrared Processing and Analysis Center (IPAC)
Subject Keywords:Galaxy: halo, galaxies: dwarf
Series Name:Proceedings of the International Astronomical Union
Issue or Number:344
Record Number:CaltechAUTHORS:20191125-145324945
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Official Citation:Grillmair, C. (2018). FOSSILs in the Galactic Halo. Proceedings of the International Astronomical Union, 14(S344), 73-76. doi:10.1017/S1743921318007111
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:100046
Deposited By: Tony Diaz
Deposited On:25 Nov 2019 23:03
Last Modified:16 Nov 2021 17:51

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