Star Formation Histories from Spectral Energy Distributions and Color Magnitude Diagrams Show Synchronized Star Formation in Local Volume Dwarf Galaxies
Star Formation Histories (SFHs) can reveal physical processes that influence how galaxies form their stellar mass. For nearby resolved galaxies, SFHs can be reconstructed from Color Magnitude Diagrams (CMDs), while for more distant galaxies, broad-band Spectral Energy Distribution (SED) fitting is used. Olsen et al. (2021) compared the SFHs of 36 Local Volume dwarf galaxies with D < 4 Mpc from the ACS Nearby Galaxy Survey Treasury (ANGST), for which both types of observations are available. Metrics comparing galaxy properties recovered from published CMD SFHs and the Dense Basis SED fitting code show overall good agreement. For both the SED and CMD methods, the median normalized SFH of galaxies in the sample shows a period of quiescence at lookback times of 3-6 Gyr followed by rejuvenated star formation over the past 3 Gyr that remains active until the present day. To determine if these represent special epochs of star formation in the D < 4 Mpc portion of the Local Volume, the ANGST dwarf galaxy sample was broken into subsets based on specific star formation rate and spatial location. We have followed this by testing for “conformity” in galaxy properties such as specific star formation rate and quenched fraction, and for the first time, we make use of the galaxy star formation histories to extend this analysis back in time. The agreement between these two methods with complementary systematics motivates implies that shallow or semi-resolved observations yielding incomplete CMDs can be supplemented with broadband photometry. The surprising result of synchronized star formation in these galaxies motivates using Roman to delve further into dwarf galaxy evolution in the Local Volume than previously possible.