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SOAR observations key to identifying the densest galaxies known
Two undergraduates at San José State University have discovered two galaxies that are the densest known. Similar to ordinary globular star clusters but a hundred to a thousand times brighter, the new systems have properties intermediate in size and luminosity between galaxies and star clusters.
The study, led by undergraduates Michael Sandoval and Richard Vo, used imaging data from the Sloan Digital Sky Survey, the Subaru Teles cope, and Hubble Space Telescope, and spectroscopy from the Goodman Spectrograph on the Southern Astrophysical Research Telescope (SOAR). The SOAR spectrum allowed the authors to show that M59-UCD3 is associated with a larger host galaxy, M59, and to measure the age and elemental abundances of the galaxy’s stars.
Reference: “Hiding in plain sight: record-breaking compact stellar systems in the Sloan Digital Sky Survey,” Michael A. Sandoval, Richard P. Vo, Aaron J. Romanowsky et al. 2015, Astrophysical Journal Letters, 808, L32. (Preprint: http://arxiv.org/abs/1506.08828)
First SOAR MOS observations find old Galactic globular cluster with no signatures of multiple stellar populations
Traditionally known as the quintessential single stellar populations, precise HST photometry and higher-resolution spectroscopy have found that most, if not all, Galactic globular clusters host more than one stellar population. Mutiple stellar populations are produced if the star cluster is massive enough to retain the enriched material produced by stellar evolution. What happens then in the case of low-mass clusters? Will they host multiple stellar populations or is there a mass limit for this self-enrichment?
A team of MSU astronomers used the newly commissioned MOS capabilities of the Goodman spectrograph at SOAR to study 23 red giant branch stars in the low-mass cluster E 3 (See top panel of figure for an example of the raw MOS data). By studying the cyanogen (CN) absorption features in the blue part of the spectra (bottom left panel in the figure), they have found a very narrow distribution of the CN abundance (in the bottom right panel compared to the CN distribution in the low mass clusters Palomar 12 and Terzan 7), consistent with a cluster hosting only a single stellar population and no signs of self-enrichment. E 3 would be the first bona fide Galactic globular cluster hosting a genuine single stellar population.
Jul 27, 2015
Reference: R. Salinas & J. Strader, ApJ in press, http://arxiv.org/abs/1506.00637
SOAR held its Review Commitee 2015
Every five years during the course of observatory operations, SOAR holds an external review – roughly the equivalent of a visiting committee at universities. SOAR held its second such review this past June 24-26, in La Serena and on Cerro Pachón. In addition to hearing presentations from the Director, Board and SAC, the committee visited the telescope (see the accompanying photo).At the end of the review, the committee provided an initial debrief, and its final report has now been provided to the Board for its consideration.