Spatial Curvature, Dark Energy Dynamics, Neither, or Both?
Bharat Ratra, Kansas State University
Clues to Globular Cluster Formation
David Nataf, Johns Hopkins University
Globular clusters are now well-established to host “Second-generation” stars, which show anomalous abundances in some or all of He, C, N, O, Na, Al, Mg, etc. The simplest explanations for these phenomena typically require the globular clusters to have been ~20x more massive at birth, and to have been enriched by processes which are not consistent with the theoretical predictions of massive star chemical synthesis models. The library of observations is now a vast one, yet there has been comparatively little progress in understanding how globular clusters could have formed and evolved. In this talk I discuss two new insights into the matter. First, I report on a meta-analysis of globular cluster abundances that combined APOGEE and literature data for 28 globular clusters, new trends with globular cluster mass are identified. I discuss the chemical properties of former globular cluster stars that are now part of the field population, and what can be learned.
The Magdalena Ridge Observatory Interferometer: Design Details and Progress towards First Light with UT#1
Michelle Creech-Eakman, New Mexico Tech
The Magdalena Ridge Observatory Interferometer (MROI), a 10-telescope optical/near-IR interferometer in central NM, has been conceived to be the most ambitious optical interferometric array under construction to date. With baselines ranging from 7.8 to 347 meters, and limiting magnitudes of 14 at H band, it will be able to assess many thousands of astronomical targets on spatial scales of 10’s to 0.1’s of milliarcseconds. This is achieved through several careful design choices and trade-offs which should allow the MROI to reach 4-5 magnitudes deeper than similar facilities can achieve today. After over a decade of funding from NRL and the major partner institutions (NM Tech and Cambridge University), new funding was obtained in late 2015 via a Cooperative Agreement between NM Tech and the Air Force Research Lab (AFRL) to bring the facility to a three-interferometer system capable of observing geosynchronous satellites. However, we still maintain an exciting and compelling astronomical portfolio which will produce statistical samples of: YSOs and their surrounding disks, systems dominated by mass-loss and mass-transfer, pulsating stars and binary star systems, and images of the environs of AGN in nearby galaxies. An overview of the major design components of this ambitious imaging machine, recent progress, and plans for MROI for the next 3 years under the AFRL Cooperative Agreement will be presented.
Understanding How Galaxies Reionized the Universe
Sanchayeeta Borthakur, Arizona State University
Identifying the population of galaxies that was responsible for the reionization of the universe is a long-standing quest in astronomy. While young stars can produce large amounts of ionizing photons, the mechanism behind the escape of Lyman continuum photons (wavelength < 912 A) from star-forming regions has eluded us. To identify such galaxies and to understand the process of the escape of Lyman continuum, we present an indirect technique known as the residual flux technique. Using this technique, we identified (and later confirmed) the first low-redshift galaxy that has an escape fraction of ionizing flux of 21%. This leaky galaxy provides us with valuable insights into the physics of starburst-driven feedback. In addition, since direct detection of ionizing flux is impossible at the epoch of reionization, the residual flux technique presents a highly valuable tool for future studies to be conducted with the upcoming large telescopes such as the JWST.