The Nature of Starbursts. Ii. The Duration of Starbursts in Dwarf Galaxies

Abstract

The starburst phenomenon can shape the evolution of the host galaxy and the surrounding intergalactic medium. The extent of the evolutionary impact is partly determined by the duration of the starburst, which has a direct correlation with both the amount of stellar feedback and the development of galactic winds, particularly for smaller mass dwarf systems. We measure the duration of starbursts in twenty nearby, ongoing, and "fossil" starbursts in dwarf galaxies based on the recent star formation histories derived from resolved stellar population data obtained with the Hubble Space Telescope. Contrary to the shorter times of 3 − 10 Myr often cited, the starburst durations we measure range from 450 − 650 Myr in fifteen of the dwarf galaxies and up to 1.3 Gyr in four galaxies; these longer durations are comparable to or longer than the dynamical timescales for each system. The same feedback from massive stars that may quench the flickering SF does not disrupt the overall burst event in our sample of galaxies. While five galaxies present fossil bursts, fifteen galaxies show ongoing bursts and thus the final durations may be longer than we report here for these systems. One galaxy shows a burst that has been ongoing for only 20 Myr; we are likely seeing the beginning of a burst event in this system. Using the duration of the starbursts, we calculate that the bursts deposited 10 53.9 − 10 57.2 ergs of energy

Star Forming Dwarf Galaxies

“…The marks indicate starburst durations derived from other groups using other data. Among these are the results from McQuinn et al [109] (right pointer), Lee et al [90] (dot) and various results arriving at short durations discussed in McQuinn et al [107] (left pointer).…”

Star formation sustained by gas accretion

“…Even though individual HII regions last for a few Myr (e.g., Mas-Hesse and Kunth 1999; Harris et al 2004), the SF episodes of a galaxy as a whole do not shut off within this timescale but they last for several hundred Myr (Dohm-Palmer et al 1998;McQuinn et al 2010b;Hidalgo et al 2011). This relatively long duration of the burst is consistent with a single gas accretion event which suddenly increases the gas but which requires a much longer gas-consumption timescale to transform it into stars (τ g ∼ 1 Gyr; Sect.…”

What will blue compact dwarf galaxies evolve into?

“…Various arguments suggest, in line with evolutionary synthesis models, that starbursts in typical field BCDs do not last longer than ∼10 7 yr (Thuan 1991;Krüger et al 1995;Mas-Hesse & Kunth 1999;Thornley et al 2000) and have to be separated by long (∼1 Gyr) quiescent phases. Dwarf irregulars, on the other hand, are characterised by prolonged low-level star formation that lasts 450 Myr up to 1.3 Gyr, as shown by, e.g., McQuinn et al (2010) through colour−magnitude studies of 20 of these systems.…”