2019-09-09, 11:00:Dr. D. Hollenbach (SETI, USA)
Dr. D. Hollenbach
The Masses of the First Stars in the Universe
The mass of the first stars determine their fate and the enrichment in heavy elements to the early universe as they die. As the first stars accrete and grow to masses > 40 M_sun, their EUV luminosities rapidly increase. The EUV ionizes and heats infalling gas and gas accreting through the circumstellar disk, and this feedback can terminate the accretion onto the star and fix its final mass. This talk focuses on the halting of the accretion through the disk onto the star caused by the EUV-induced photoevaporation of the disk. We note that recent numerical simulations have found higher photoevaporation rates, and therefore lower mass first stars, than earlier semi-analytic estimates of the rates by Hollenbach et al (1994). We propose reasons for the difference, and suggest refinements on future numerical studies that will lead to somewhat higher masses for the first stars. Comparison will be made to observations of extremely metal poor stars that formed in the second generation of star formation in the universe, and whose photospheric abundances give clues to the mass of the first stars.
Location: 31 Fitzwilliam Place