Colloquia Schedule Spring 2016

Colloquia are on Tuesdays (unless otherwise indicated) at 3:30 pm in RLM 15.216B

Jan. 19

"Spirals, Gaps, and Cavities: Signposts of Planets in Protoplanetary Disks?"


Robin (Ruobing) Dong


host: Adam Kraus

Jan. 26

"The Key Influence of AGB Stars on the Evolution and Global Properties of Galaxies"


Martha L. Boyer

NASA Goddard

host: Kristen McQuinn

Feb. 2

"CAMPARE and Cal-Bridge: Two Synergistic Programs Forming a Successful New Model for Promoting Participation of Women and Underrepresented Minority Students in Astronomy"


Alexander L. Rudolph

California State Polytechnic University, Pomona

host: William Cochran

Feb. 9

"Exoplanet Atmospheres in High Resolution"


Jayne L. Birkby

Harvard-Smithsonian Center for Astrophysics

host: Daniel Jaffe

Feb. 16

"The Dynamical Evolution of Young Stellar Complexes in the Milky Way"


Alison I. Sills

McMaster University, Hamilton, ON

host: Natalie Gosnell

Feb. 23

"The Evolution of Galaxy Structural Properties"


Rachel Somerville

Rutgers University, Downsbrough Chair in Astrophysics

host: Shardha Jogee

Mar. 1

"A PHAT New Measurement of the High-Mass Stellar IMF"

The initial mass function (IMF) for stars above ~1 Msun is essential to testing and validating theories of star formation, constraining chemical enrichment models, the frequency of core-collapse supernovae, and interpreting the stellar populations of galaxies across cosmic time. Yet, despite more than 60 years of research, observational constraints on the high-mass IMF remain remarkably uncertain. Widely used high-mass IMFs (e.g., Kroupa) have associated uncertainties approaching an order-of-magnitude, making it virtually impossible to determine if the high-mass IMF varies with respect to environment (e.g., metallicity or star formation intensity) or is "Universal". In this talk, I will present the most precise measurement of the high-mass IMF to date. Using ~100 young, resolved star clusters in M31 imaged as part of the Panchromatic Hubble Andromeda Treasury (PHAT) survey, we find the high-mass IMF slope to be Gamma=1.45+/-0.03. Compared to the canonical Kroupa IMF (Gamma=1.3+/-0.7), the high-mass IMF in M31 is 0.15 dex steeper (i.e., fewer massive stars) and represents a factor of ~20 improvement in precision. There are no significant trends between the cluster IMF slopes and their ages, masses, and sizes, indicating that the IMF is remarkably "Universal" in this sample of ~100 clusters. I will illustrate some of the broader implications of a steeper IMF slope (e.g., on star formation rate indicators, core-collapse supernovae rates) and will conclude by discussing the prospects for precision IMF measurements in other environments.


Daniel Weisz

UC Berkeley/University of Washington

host: Michael Boylan-Kolchin

Mar. 8

"The Role of Dwarf-Dwarf Galaxy Interactions in Galaxy Assembly"


Sabrina Stierwalt

NRAO/University of Virginia

host: Kristen McQuinn

Mar. 15

No colloquium scheduled. (Spring Break)

Mar. 22

"Exploring the z~2.3 Cosmic Web with 3D Lyman-Alpha Forest Tomography"


Khee-Gan Lee

UC Berkeley/LBNL

host: Caitlin Casey

Mar. 29

"Understanding Galaxy Evolution with Massive Starburst Galaxies"


Hai Fu

University of Iowa

host: Caitlin Casey

Apr. 5

"Implications from the Detection of the Binary Black Hole Inspiral GW150914"


Matthew Benacquista

University of Texas Rio Grande Valley

host: J. Craig Wheeler

Apr. 6

Stellar Seminar talk Date/Time: Wed., 12 Noon: "Title: TBA"

David Yong (Stellar Tinsley Scholar)

Mt. Stromlo Observatory, Australia

host: Fritz Benedict

Apr. 12

"The Calm Before the Storm: Exploring the Post Accretionary Doldrums Prior to the Late Heavy Bombardment"


William F. Bottke (Planetary Tinsley Scholar)

Southwest Research Instutite, Boulder, Colorado

host: Mike Endl/Judit Ries

Apr. 19

"Disk Galaxy Assembly Across Cosmic Time: Combining Magnitude-limited Survey with Gravitational Lensing"


Tiantian Yuan (Exgal Tinsley Scholar)

Australia National University

host: Chao-Ling Hung

Apr. 26

"The Discovery and Characterization of the Y Dwarfs"


Michael Cushing

University of Toledo

host: Brendan Bowler

May 3

"What can Binaries tell us about Planet Formation?"


Kaitlin M. Kratter (ISM Tinsley Scholar)

Steward Observatory, University of Arizona

host: Adam Kraus

Visitors to the Department of Astronomy can find detailed information and maps on our Visiting Austin Page.

Please report omissions/corrections to: G. Orris at

15 April 2016
Astronomy Program · The University of Texas at Austin
prospective student inquiries:
site comments: · web accessibility policy · web privacy policy