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Space Telescope Science Institute
The Stellar IMF at Low Masses: A Critical Look at Variations and Environmental Dependencies

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Scientific Rationale

The shape of the stellar initial mass function (IMF) is one of the main uncertainties in our understanding of star formation, i.e., the conversion of gas into stars over cosmic time. It is usually assumed that the IMF in external galaxies is the same as in the disk of the Milky Way, where most studies of resolved stellar populations showed the IMF to be “universal”.

However, the "universality" of the stellar IMF has recently been challenged: kinematics from integral-field spectroscopy of nearby galaxies as well as line strength studies of molecular features in spectra of early-type galaxies have shown evidence for a steepening of the low-mass IMF with increasing galaxy velocity dispersion. Deep star count studies in nearby dwarf galaxies seem to corroborate these findings. However, alternative explanations for the spectroscopic evidence have also started to appear in the literature.

A non-universal IMF, if confirmed, would have important implications regarding our understanding of galaxy evolution. The main purpose of this workshop is to have a critical look at current and new evidence for variations of the IMF at sub-solar stellar masses. Recent observational and theoretical insights will be presented to evaluate whether and how the IMF may vary across different environments. Emphasis will be given to the role of future observing facilities in constraining the theoretical scenarios.

Instructions for Interested Participants

To help create a collaborative and engaging atmosphere, the attendance will be limited to 60-70 participants. The workshop will include a combination of Invited Talks, Contributed Talks, and Posters.


Registration for this workshop will start on March 13, 2015. Applicants who have been accepted for participation are asked to complete their registration and pay the workshop registration fee. The registration fee is $200.00. A banquet dinner is planned for Tuesday, June 30th. The cost to attend the dinner is $55.00. This amount is in addition to the registration fee. Registration will only be complete after payment is made by credit card. Deadline for registration and payment of registration fee is May 29, 2015.

Special Colloquium - Wednesday, July 1, 2015

The final talk of this workshop will be a special STScI colloquium on the workshop topic to be held at 3:30 p.m. in the Bahcall Auditorium. This colloquium will be open to the whole STScI/JHU community. The speaker will be Marla Geha of Yale University. All the workshop participants are invited to stay at STScI after the formal conclusion of the workshop to attend this talk.

Important Dates

Date Event
Mar 13 Notification of Talk/Poster Presentations, Registration Opens
May 29 Registration and Registration Fee Payment Deadline
Jun 28 Welcome Reception 4:30 - 6:30 PM
Jun 29 Workshop Opens
Jul 01 Special Colloquium - 3:30 PM

Invited Review Speakers

Speaker Affiliation
Estelle Moraux Université Grenoble Alpes, IPAG
Mark Krumholz University of California-Santa Cruz
Michele Cappellari University of Oxford
Charlie Conroy Harvard University
Marla Geha (special colloquium speaker) Yale University

Scientific Organizing Committee

Name Affiliation
Paul Goudfrooij (Chair) Space Telescope Science Institute
Tom Brown Space Telescope Science Institute
Annalisa Calamida Space Telescope Science Institute
Mario Gennaro Space Telescope Science Institute
Jason Kalirai Space Telescope Science Institute
Janice Lee Space Telescope Science Institute
Stella Offner University of Massachusetts-Amherst
Rosemary Wyse Johns Hopkins University