Stellar Populations in the Cosmological Context: Day 1

The Space Telescope Science Institute is currently hosting their annual May Symposium. This year, it’s on “Stellar Populations in the Cosmological Context“. The official abstract for the meeting claims “The 2010 May Symposium aims at understanding the physical processes and observational characteristics of local stellar populations as a tool for elucidating the evolution of general stellar populations throughout cosmic history”, but I prefer to think of it as “Hey! Galaxies are made of STARS! We might learn something if we actually look at them!”

For those of you playing along at home, you can skip the layover in Denver and the seven dollar snack box on the plane and just watch the conference on the web (although I’ve heard that the streaming was dicey today). Some of the highlights for me today were:

A very nice talk by Sally Oey on a number of issues related to energetics of massive stars and feedback effects. The local observations of how ionizing photons may or may not get out of HII regions has bearing on many very high-redshift searches for constraints on the sources of reionization.

A horrifying bit in an otherwise non-horrifying talk on the 30 Doradus region by Chris Evans, where he pointed out how multi-epoch spectroscopy by Bosch et al 2009 dropped the velocity dispersion of the cluster from 35 km/s to 8 km/s, by correcting for the motions of stars in binaries (2/3rds of the massive stars). Herein dies the dream of measuring masses of unresolved stellar clusters at larger distances.

A consistently entertaining talk by Guido De Marchi on using an efficient diagnostic of pre-main sequence stars to age date very young stars. Clearly lots of details to understand before I can buy into it completely, but seemed to be a very promising way of mapping out exactly how star formation propagates around a region.

A rather dense afternoon discussion of the completely crazy multiple sequences seen in high-precision HST observations of globular clusters. They are clearly single stellar populations no more (or at least, not all of them). Unfortunately, the new observations take what is already an extreme endpoint of star formation, and place even weirder requirements on the possible formation scenarios. Most mechanisms for producing the multiple sequences involve having a significant fraction of the globular’s stars enriched with a hellacious amount helium, without any significant additional iron enrichment. Alvio Renzini’s talk was probably the clearest introduction to the problem, if you’re new to it. He has some, um, strong opinions about the plausibility of possible solutions. I found Selma De Mink’s subsequent talk to be a viable scenario as well. Interesting discussion at the end of the day about how much this may actually matter for field stars, or stars that form in less massive clusters.

And, the image for the day for me was the multiwavelength map of 30 Doradus, showing the X-ray emission (red) filling in holes in the distribution of gas (H-alpha in green) ionized by young UV bright stars (blue):

30 Doradus

Posted via web from Traction Lobe