Thursday, December 31, 2015

Ongoing Star Formation in the Dwarf Galaxy Leo P

Leo P is a faint, gas-rich dwarf galaxy with ongoing star formation. It is located 5.28 ± 0.49 million light years away, at the edge of the Local Group, far from the influence of any massive galaxy. The total mass of stars in Leo P is estimated to be ~600,000 times the Sun’s mass. Leo P is also home to a massive star with at least 25 times the mass of the Sun. The presence of this star shows that massive stars can form even with star formation rates as low as ~0.00001 solar-mass per year. Observations of the different populations of stars in Leo P show a constant rate of star formation over the lifetime of the dwarf galaxy.

The luminosity of Leo P appears similar to the dwarf spheroidal (dSph) galaxies around the Milky Way. However, unlike Leo P, the dSph galaxies around the Milky Way contain little to no gas, and have no ongoing stars formation. This indicates that Leo P is what a dSph galaxy would look like if it evolved in an isolated environment and held on to its gas content. It also shows that the environment around the Milky Way has the effect of quenching star formation in its satellite dwarf galaxies.

McQuinn et al. (2015), “Leo P: An Unquenched Very Low-Mass Galaxy”, arXiv:1506.05495 [astro-ph.GA]