Journal article
LEO P: AN UNQUENCHED VERY LOW-MASS GALAXY Based on observations made with the NASA/ESA Hubble Space Telescope (HST), obtained from the Data Archive at the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS 5-26555
The Astrophysical journal, Vol.812(2), 158
10/20/2015
DOI: 10.1088/0004-637X/812/2/158
Abstract
ABSTRACT 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 active star formation, an underlying older population, and an extremely low oxygen abundance. We have obtained optical imaging with the Hubble Space Telescope to two magnitudes below the red clump in order to study the evolution of Leo P. We refine the distance measurement to Leo P to be 1.62 0.15 Mpc, based on the luminosity of the horizontal branch stars and 10 newly identified RR Lyrae candidates. This places the galaxy at the edge of the Local Group, ∼0.4 Mpc from Sextans B, the nearest galaxy in the NGC 3109 association of dwarf galaxies of which Leo P is clearly a member. The star responsible for ionizing the H ii region is most likely an O7V or O8V spectral type, with a stellar mass 25 M . The presence of this star provides observational evidence that massive stars at the upper end of the initial mass function are capable of being formed at star formation rates as low as ∼10−5 M yr−1. The best-fitting star formation history (SFH) derived from the resolved stellar populations of Leo P using the latest PARSEC models shows a relatively constant star formation rate over the lifetime of the galaxy. The modeled luminosity characteristics of Leo P at early times are consistent with low-luminosity dSph Milky Way satellites, suggesting that Leo P is what a low-mass dSph would look like if it evolved in isolation and retained its gas. Despite the very low mass of Leo P, the imprint of reionization on its SFH is subtle at best, and consistent with being totally negligible. The isolation of Leo P, and the total quenching of star formation of Milky Way satellites of similar mass, implies that the local environment dominates the quenching of the Milky Way satellites.
Details
- Title: Subtitle
- LEO P: AN UNQUENCHED VERY LOW-MASS GALAXY Based on observations made with the NASA/ESA Hubble Space Telescope (HST), obtained from the Data Archive at the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS 5-26555
- Creators
- Kristen B. W. McQuinn - The University of Texas at AustinEvan D. Skillman - University of MinnesotaAndrew Dolphin - RTXJohn M. Cannon - Macalester CollegeJohn J. Salzer - Indiana University BloomingtonKatherine L. Rhode - Indiana University BloomingtonElizabeth A. K. Adams - Netherlands Institute for Radio AstronomyDanielle Berg - University of MinnesotaRiccardo Giovanelli - Cornell UniversityLéo Girardi - Osservatorio Astronomico di PadovaMartha P. Haynes - Cornell University
- Resource Type
- Journal article
- Publication Details
- The Astrophysical journal, Vol.812(2), 158
- Publisher
- The American Astronomical Society
- DOI
- 10.1088/0004-637X/812/2/158
- ISSN
- 0004-637X
- eISSN
- 1538-4357
- Number of pages
- 15
- Alternative title
- LEO P: AN UNQUENCHED VERY LOW-MASS GALAXY
- Language
- English
- Date published
- 10/20/2015
- Academic Unit
- Physics and Astronomy
- Record Identifier
- 9984627233102771
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