Calendar

Sep
14
Fri
Astro-ph Discussion
Sep 14 @ 11:30 am – 12:00 pm
Astro-ph Discussion @ AY119
Observatory Open House
Sep 14 @ 8:00 pm – 9:00 pm
Observatory Open House @ Tombaugh Observatory

Host: Chris Churchill. Assisted by Trevor Picard, Lauren Kahre, and Ali Hyder

Sep
19
Wed
Astro-ph Discussion
Sep 19 @ 1:30 pm – 2:00 pm
Astro-ph Discussion @ AY119
Sep
21
Fri
Astro-ph Discussion
Sep 21 @ 11:30 am – 12:00 pm
Astro-ph Discussion @ AY119
Colloquium: Dave Thilker (Host: Rene Walterbos)
Sep 21 @ 3:15 pm – 4:15 pm
Colloquium: Dave Thilker (Host: Rene Walterbos) @ BX102

Fresh Perspectives on Star Formation from LEGUS, the Legacy ExtraGalactic Ultraviolet Survey

David Thilker, Johns Hopkins University

The Legacy ExtraGalactic Ultraviolet Survey (LEGUS) was a Cycle 21 Large Treasury HST program which obtained ~parsec resolution NUV- to I-band WFC3 imaging for 50 nearby, representative star-forming Local Volume galaxies, with a primary goal of linking the scales of star formation from the limit of individual stars, to clusters and associations, eventually up through the hierarchy to giant star forming complexes and galaxy-scale morphological features.

I will review the basics of the survey, public data products and science team results pertaining to clusters and the field star hierarchy.  I will then describe work to optimize photometric selection methods for massive main sequence O star candidates and LBV candidates, in the former case establishing a means to statistically constrain the fraction of O stars in very isolated locales.  I will introduce new ideas on how to quantify the complex spatio-temporal nature of hierarchical star formation using multi-scale clustering methods. The first steps of this work have yielded a landmark OB association database for 36 LEGUS target fields (in 28 of the nearest available galaxies), with tracer stellar populations selected and interpreted uniformly.  I will finish with discussion of a pilot HST program to demonstrate remarkably increased survey efficiency of WFC3 UV imaging enabled by use of extra-wide (X) filter bandpasses.  Such efficiency is required as we move beyond LEGUS and begin to rigorously explore low surface brightness star-forming environments where canonical results for the IMF and cluster formation efficiency are increasingly called into question.

 

Sep
26
Wed
Astro-ph Discussion
Sep 26 @ 1:30 pm – 2:00 pm
Astro-ph Discussion @ AY119
Sep
28
Fri
Astro-ph Discussion
Sep 28 @ 11:30 am – 12:00 pm
Astro-ph Discussion @ AY119
Colloquium: Bharat Ratra (Host: Anatoly Klypin)
Sep 28 @ 3:15 pm – 4:15 pm
Colloquium: Bharat Ratra (Host: Anatoly Klypin) @ BX102

Spatial Curvature, Dark Energy Dynamics, Neither, or Both?

Bharat Ratra, Kansas State University

Experiments and observations over the two last decades have persuaded cosmologists that (as yet undetected) dark energy is by far the main component of the energy budget of the current universe. I review a few simple dark energy models and compare their predictions to observational data, to derive dark energy model-parameter constraints and to test consistency of different data sets. I conclude with a list of open cosmological questions.
Oct
3
Wed
Astro-ph Discussion
Oct 3 @ 1:30 pm – 2:00 pm
Astro-ph Discussion @ AY119
Oct
5
Fri
Astro-ph Discussion
Oct 5 @ 11:30 am – 12:00 pm
Astro-ph Discussion @ AY119