Astronomy Colloquium for 2017-11-15

Series: Astronomy Colloquium
Date: Wednesday 15-Nov-2017
Time: 16:05-17:00 (4:05-5:00 pm)
Location: ATL 2400
Speaker: Dr. Elena Gallo ( University of Michigan)
Title: The local massive black hole occupation fraction

Whereas mergers and intermittently efficient accretion in larger black holes spur growth and remove observational signatures of their birth,smaller black holes have more subdued histories and undergo mostly secular evolution. Consequently, both the mass distribution and the very rate of occupancy of massive black holes in lower-mass galaxies contain archaeological information on the initial “seeding” mechanism. I will present recent results from a number of observational campaigns aimed at characterizing the massive black hole population in nearby low-mass galaxies. Most notably, I will discuss how a measurement of the local active fraction down to very low X-ray Eddington ratios can be employed to yield quantitative constraints on the massive black hole occupation fraction. As this measurement relies on Chandra X-ray Telescope data for hundreds of nearby galaxies, it enables us to concurrently quantify the incidence and intensity of low-level black hole accretion as a function of host stellar mass as well as environment (such as living in isolation vs. belonging to a cluster or group), and characterize the relation between massive black holes and nuclear star clusters, also as a function of environment and galactic morphology.

Colloquia are usually preceded by espresso and ice cream at 1:45 pm outside room PSC 1150 and are followed by an informal reception at 5:15 pm in that room. Anyone interested in talking with the speaker, or being added to the colloquium announcement email list, should contact the colloquium organizer. Lunch will normally be reserved for the speaker to talk to graduate students.

Colloquium Organizer: Prof. L. Drake Deming


Special accommodations for individuals with disabilities can be made by calling (301) 405-3001. It would be appreciated if we are notified at least one week in advance.


Directions and information about parking can be found here.

This page was automatically generated on: 10-Oct-2017.