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arXiv · 1411.5019

Two Local Volume Dwarf Galaxies Discovered in 21 cm Emission: Pisces A and B

Erik J. Tollerud·Marla C. Geha·Jana Grcevich·Mary E. Putman·Daniel Stern
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Abstract

We report the discovery of two dwarf galaxies, Pisces A and B, from a blind 21 cm HI search. These were the only two galaxies found via optical imaging and spectroscopy of 22 HI clouds identified in the GALFA-HI survey as dwarf galaxy candidates. They have properties consistent with being in the Local Volume ($<10$ Mpc), and one has resolved stellar populations such that it may be on the outer edge of the Local Group ($\sim 1 \, {\rm Mpc}$ from M31). While the distance uncertainty makes interpretation ambiguous, these may be among the faintest starforming galaxies known. Additionally, rough estimates comparing these galaxies to $Λ$CDM dark matter simulations suggest consistency in number density, implying that dark matter halos likely to host these galaxies are primarily HI-rich. The galaxies may thus be indicative of a large population of dwarfs at the limit of detectability that are comparable to the faint satellites of the Local Group. Because they are outside the influence of a large dark matter halo to alter their evolution, these galaxies can provide critical anchors to dwarf galaxy formation models.

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Erik J. Tollerud, Marla C. Geha, Jana Grcevich, Mary E. Putman, Daniel Stern. 2014-11-18. Two Local Volume Dwarf Galaxies Discovered in 21 cm Emission: Pisces A and B. https://doi.org/10.1088/2041-8205%2F798%2F1%2Fl21

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