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NRAO/Socorro Colloquium Series

Mordecai-Mark Mac Low

AMNH

The Formation of Molecular Clouds and Massive Stars

In this talk I consider two questions. First, I examine the formation of molecular clouds from diffuse interstellar gas. It has been argued that the pressure of the interstellar gas controls the fraction of molecular hydrogen present, and thus the star formation rate. Alternatively, I and others have suggested that the gravitational instability of gas in galactic disks controls both. I present numerical results demonstrating that observed correlations between midplane pressure, molecular hydrogen fraction, and star formation rate can be explained within the gravitational instability picture. Second, I discuss how ionization affects the formation of the most massive stars. Although most distinctive observables of massive stars can be traced back to their ionizing radiation, it does not appear to have a strong effect on their actual formation. Rather, I present simulations suggesting that stars only ionize large volumes after their accretion has already been throttled by gravitational fragmentation in the accretion flow. At the same time these models can explain many aspects of the observations of ultracompact H II regions. Finally, I will show how some predictions of these models are now being tested by the JVLA.

May 3, 2013
11:00 am

Array Operations Center Auditorium

All NRAO employees are invited to attend via video, available in Charlottesville Room 230, Green Bank Room 137 and Tucson N525.

Local Host: Juergen Ott