The Effects of Mass Loss on Subsequent Star Formation and the Evolution of Galaxies

by Charles Wheaton Congdon

ABSTRACT

The effects of stellar mass loss on subsequent star formation and galactic evolution are examined. It is found that mass loss can decrease the net rate of gas consumption by star formation up to almost a factor of two. These results are dependent on the choice of initial mass function. in the two cases studied (the Salpeter and Kennicutt IMFs), the return rate was found to vary by about a factor of 1.5. Other factors such as the initial-final mass relations can effect this result, but to a much smaller extent. Accounting for mass loss has a profound effect on galactic evolution. Even in galaxies that consume all of their gas each time step, mass loss can return enough gas to keep the star formation rate at or above 1 solar mass per year for relatively long periods, thus removing the need to invoke infall of gas from outside the galaxy. For galaxies with more moderate star formation laws, the rate easily stays about 1 solar mass per year for over 15 billion years. Without mass return these model galaxies would consume all of their gas in under 2 billion years. Finally it is found that up to half of the galactic mass is tied up in stars under 0.9 solar mass that undergo little significant mass loss in a Hubble time.