20 December 2016, Tuesday, 7:45 PM, Presidio Observation Post, Building 211
“Are Ancient Galaxies Really Red and Dead”
Leo Blitz, PhD, UC Berkeley Department of Astrophysics
Galaxies are broadly divided into two classes: spiral and elliptical. Unlike the spirals, the ellipticals, often referred to as early-type galaxies, are largely composed of old stars that give them a reddish color, They typically have little interstellar material with which to form new stars; these galaxies are often referred to as “red and dead.” We will see, however, that a substantial fraction of these galaxies contain surprising amounts of neutral hydrogen and these do form stars, albeit at a reduced rate compared to their spiral cousins. Early-type galaxies outside of clusters can be seen to be accreting gas from their surroundings, which is the source of at least some of the gas fueling star-formation taking place within them. In addition, the galaxies are seen to contain super-massive black holes in their centers. The black holes appear to be responsible for ejecting much of the gas that falls into the nuclei of these galaxies, reenergizing the intergalactic medium.
Here is a Hubble ultra-deep field image of galaxies in deep space:
Leo Blitz’s research interests focus mainly on how galaxies form and evolve into the objects we see today, and how the interstellar gas within galaxies is collected to form stars. Items of current active interest include trying to understand the nature of dark matter on galactic scales, particularly in dwarf galaxies and in the outer parts of the Milky Way. He is also working on how the diffuse interstellar medium generates star-forming giant molecular clouds in different environments to unravel the basic physics of star formation on galactic scales.his team operates an array of fifteen millimeter-wave radio telescopes as part of the CARMA Array, near Bishop, California. They are building the Allen Telescope Array, a new type of radio interferometer of 350 dishes using commercial satellite dish technology to synthesize an aperture of 10,000 square meters for use at centimeter wavelengths.