Alfalfa discovery of the nearby gas-rich dwarf galaxy leo p. iv. distance measurement from lbt optical imaging

Kristen B.W. McQuinn, Evan D. Skillman, Danielle Berg, John M. Cannon, John J. Salzer, Elizabeth A.K. Adams, Andrew Dolphin, Riccardo Giovanelli, Martha P. Haynes, Katherine L. Rhode

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Leo P is a low-luminosity dwarf galaxy discovered through the blind H I Arecibo Legacy Fast ALFA survey. The H I and follow-up optical observations have shown that Leo P is a gas-rich dwarf galaxy with both active star formation and an underlying older population, as well as an extremely low oxygen abundance. Here, we measure the distance to Leo P by applying the tip of the red giant branch (TRGB) distance method to photometry of the resolved stellar population from new Large Binocular Telescope V and I band imaging. We measure a distance modulus of 26.19 mag corresponding to a distance of Mpc. Although our photometry reaches 3 mag below the TRGB, the sparseness of the red giant branch yields higher uncertainties on the lower limit of the distance. Leo P is outside the Local Group with a distance and velocity consistent with the local Hubble flow. While located in a very low-density environment, Leo P lies within ∼0.5 Mpc of a loose association of dwarf galaxies which include NGC 3109, Antlia, Sextans A, and Sextans B, and 1.1 Mpc away from its next nearest neighbor, Leo A. Leo P is one of the lowest metallicity star-forming galaxies known in the nearby universe, comparable in metallicity to I Zw 18 and DDO 68, but with stellar characteristics similar to dwarf spheriodals (dSphs) in the Local Volume such as Carina, Sextans, and Leo II. Given its physical properties and isolation, Leo P may provide an evolutionary link between gas-rich dwarf irregular galaxies and dSphs that have fallen into a Local Group environment and been stripped of their gas.

Original languageEnglish (US)
Article number145
JournalAstronomical Journal
Issue number6
StatePublished - Dec 2013


  • galaxies: distances and redshifts
  • galaxies: dwarf
  • galaxies: evolution
  • galaxies: fundamental Parameters
  • galaxies: photometry
  • galaxies: stellar content


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