The complex star-formation history of NGC 1569
Abstract
We present new results on the star-formation history (SFH) of NGC 1569, derived using the synthetic Color-Magnitude Diagram method (CMD). The data have been obtained using Hubble Space Telescope NICMOS/NIC2 in the F110W and F160W near-infrared filters. The best fit to the data is obtained assuming 3 episodes of activity in the last 1 - 2 Gyr and a Salpeter IMF. The most recent and strongest (3.2 M⊙ yr-1 kpc-2) episode started 37 Myr ago and ended 13 Myr ago. A previous episode produced stars between ∼ 150 Myr and ∼ 40 Myr ago, with a mean star-formation rate (SFR) about 2/3 lower than the mean SFR of the youngest episode. An older star-formation episode occurred about 1 Gyr ago. All of these SFRs are 2-3 orders of magnitude higher than those derived for late-type dwarfs in the Local Group. We cannot rule out a low SFR in the past > 1 Gyr but we can safely conclude that the last 1-2 Gyr have been peculiar.
- Publication:
-
Starbursts: From 30 Doradus to Lyman Break Galaxies
- Pub Date:
- May 2005
- Bibcode:
- 2005ASSL..329P...4A