The M81 group dwarf irregular galaxy DDO 165. II. Connecting recent star formation with interstellar medium structures and kinematics

We compare the stellar populations and complex neutral gas dynamics of the M81 group dIrr galaxy DDO 165 using data from the Hubble Space Telescope and the Very Large Array. Cannon et al. in Paper I of this series identified two kinematically distinct H I components, multiple localized high velocity gas features, and eight H I holes and shells (the largest of which spans ~2.2 × 1.1 kpc). Using the spatial and temporal information from the stellar populations in DDO 165, we compare the patterns of star formation (SF) over the past 500 Myr with the H I dynamics. We extract localized star formation histories within 6 of the 8 H I holes identified in Paper I, as well as 23 other regions that sample a range of stellar densities and neutral gas properties. From population synthesis modeling, we derive the energy outputs (from stellar winds and supernovae) of the stellar populations within these regions over the last 100 Myr, and compare with refined estimates of the energies required to create the H I holes. In all cases, we find that "feedback" is energetically capable of creating the observed structures in the interstellar medium (ISM). Numerous regions with significant energy inputs from feedback lack coherent H I structures but show prominent localized high velocity gas features; this feedback signature is a natural product of temporally and spatially distributed SF. In DDO 165, the extended period of heightened SF activity (lasting more than 1 Gyr) is energetically capable of creating the observed holes and high velocity gas features in the neutral ISM. Based on observations made with the NASA/ESA Hubble Space Telescope, obtained from the Data Archive at the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS 5-26555