Growth and evolution of the M81 group of galaxies.

摘要

Stellar feedback, along with interactions and mergers, is fundamental to the evolution of galaxies on all physical scales and throughout their histories. The aim of my study is to investigate the cycle of the star formation focusing on the young massive star-forming regions and their interaction with their surroundings on the local scales in eight galaxies in the M81 group.;First, the X-ray data of NGC 2403 are analyzed to understand the hot phase of the interstellar medium as characterized by the X-ray properties of the hot gas, separately treating supernovae remnants, HII regions, and diffuse residual emission. The observed hot gas temperature of the events related to star-forming activities does not change dramatically over the recent star-formation time scale, about 100 Myr, but the density of the hot gas and hence pressure may decrease over time.;Second, the physical properties of the star-forming events on local scales are derived from comparing the broadband photometric spectra using GALEX and Spitzer data to the stellar population synthesis models convolved with the dust reprocessing model. The mechanical luminosity from stars via stellar winds and supernovae is estimated based on the derived physical properties and compared to the X-ray luminosity of star-forming regions to estimate the amount of radiative losses of the hot gas. A very low ratio of the X-ray luminosity to mechanical luminosity suggests that most of the released energy goes into thermalization and is only slowly radiated over a very long period of time.;Finally, the properties of the identified star-forming regions are compared against the properties of the host galaxies such as their morphological types and interaction indicies in the M81 group. It is shown that massive young clusters are found in all types of galaxies and all interaction histories. This is true even for galaxies that have not interacted, suggesting that star formation is driven by internal structures like bars and density waves.