We present here the results obtained from studying the resolved stellar populations of two dwarf irregular galaxies in the nearby Universe. These galaxies, DDO 68 and NGC 4449, were studied within the Legacy ExtraGalactic UV Survey, an HST program aimed to uncover the many ways in which the star formation (SF) process occurs at different scales. Thanks to the deep photometry obtained in different bands (from λ2704 Å to λ8057 Å), we were able to connect the location and timescales of the star forming regions within the galaxies to merging and interaction with gas clouds and satellites, a crucial aspect of galaxy evolution, even in such small systems. From the color-magnitude diagrams of the analyzed galaxies we were able to recover their star formation history (up to ~ 2 - 3 Gyr ago since we do not observe the oldest main sequence turn-off or horizontal branch, due to the systems' distance), finding that the SF never really stopped, but proceeded continuously even with the succession of high and low activity. The time intervals where we find higher SF rates in the two galaxies well agree with the dynamical timescales of previous interactions events, which might represent a major channel for triggering the SF in relatively isolated galaxies.
Star formation and environment: a step in understanding the formation and evolution of local dwarf galaxies
Cignoni, Michele;
2019-01-01
Abstract
We present here the results obtained from studying the resolved stellar populations of two dwarf irregular galaxies in the nearby Universe. These galaxies, DDO 68 and NGC 4449, were studied within the Legacy ExtraGalactic UV Survey, an HST program aimed to uncover the many ways in which the star formation (SF) process occurs at different scales. Thanks to the deep photometry obtained in different bands (from λ2704 Å to λ8057 Å), we were able to connect the location and timescales of the star forming regions within the galaxies to merging and interaction with gas clouds and satellites, a crucial aspect of galaxy evolution, even in such small systems. From the color-magnitude diagrams of the analyzed galaxies we were able to recover their star formation history (up to ~ 2 - 3 Gyr ago since we do not observe the oldest main sequence turn-off or horizontal branch, due to the systems' distance), finding that the SF never really stopped, but proceeded continuously even with the succession of high and low activity. The time intervals where we find higher SF rates in the two galaxies well agree with the dynamical timescales of previous interactions events, which might represent a major channel for triggering the SF in relatively isolated galaxies.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
