Star Formation Histories of Dwarf Galaxies from the Colour-Magnitude Diagrams of Their Resolved Stellar Populations
Figure 1
The effect of the SFH on the theoretical CMD of a hypothetical galactic region with , .08, and with the photometric errors and incompleteness typical of HST/WFPC2 photometry. All the shown synthetic CMDs contain 50 000 stars and are based on the Padova models [22, 23] with the labelled metallicities. (b) The case of an SFR constant from 13 Gyr ago to the present epoch. (a) The effect of adding a burst 10 times stronger in the last 20 Myr to the constant SFR. The CMD has a much brighter and thicker blue plume. (c) The same constant SFR as in the first case, but with a quiescence interval between 3 and 2 Gyrs ago; a gap appears in the CMD region corresponding to stars 2-3 Gyr old, which are completely missing. (e) SF activity only between 13 and 10 Gyr ago with . (f) SF activity only between 13 and 10 Gyr ago with : notice how colour and luminosity of turnoff, subgiant, and red giant branches differ from the previous case. (d) SF activity between 13 and 11 Gyr ago, followed by a second episode of activity between 5 and 4 Gyr ago: a gap separates the two populations in the CMD, but less evident than in (c) case, when the quiescent interval was more recent.
