Science with SOAR

 
In the current era of 8-10m class telescopes, and with the advent of LSST in the next several years, the 4.2m SOAR telescope stands out as an astronomical facility with a set of capabilities that make if a powerful research tool for carrying out scientfic programs not feasible at larger telescopes.

  • First, SOAR is optimized for delivering excellent image quality, and spanning a wide wavelength range, from the atmospheric cut-off in the blue (320nm) to the near infrared
  • Second, it is equipped with an "always-on" suite of optical and near-IR imagers and spectrographs, allowing switching instruments in just a few minutes. With its new ground-layer visible wavelength Adaptive Optics system (SAM) over a 3x3 arcmin field of view (FOV), and the multi-object slit mode for a 3x5 arcmin FOV on the Goodman Spectrograph, even further and exciting new possibilities open up for the potential science user.
  • Third, SOAR has an accurate and reliable non-sidereal tracking mode that enables routine observations of Solar System objects.
  • Finally, SOAR offers Remote Observing mode as a regular observing scheme, which opens possibilities like different users sharing nights among several programs, or carrying out projects requiring complicated scheduling, like multi-epoch observations scattered over weeks or months. Remote observing allows users to carry out the observations themselves, often resulting in better control and decision-making of the data acquisition process when compared with queue-mode observations.  SOAR enables programs that cannot be carried out under classical or queue observing modes in other telescopes.
Some SOAR Science Highlights
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?

Jul 27, 2015
R. Salinas & J. Strader, ApJ in press, http://arxiv.org/abs/1506.00637

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.
Coolest Known White Dwarf: A Diamond in the Sky?

“Up above the world so high, like a diamond in the sky…” A team of astronomers, using multiple telescopes, has identified the coolest, faintest white dwarf star known. White dwarfs are the extremely dense end states of stars like our sun: after their nuclear fuel is exhausted, they collapse from the size of a star (about 1,000,000 miles across) to the size of the Earth (7,000 miles across). This white dwarf, located in the constellation Aquarius, is so cool that its carbon has crystallized—in other words, it’s like a diamond, with a mass similar to that of our sun (Kaplan et al. 2014, ApJ, 789, Issue 2, 119).

This image (left), taken in visible light at the SOAR telescope (right), shows the field of the pulsar/white dwarf pair. There is no evidence for the white dwarf at the position of the pulsar in this deep image, indicating that the white dwarf is much fainter, and therefore cooler, than any such known object. The two large white circles mask bright, overexposed stars. These results are presented in a recently published paper led by Dr. David Kaplan (UW-Milwaukee)

Discovery of binary systems
Left: SAM AO image of the A and B components of the rare nearby quadruple system ADS1652. The two main components, which are 0.8" apart, are clearly separated  in the SAM 0.4" FWHM I-band image obtained on 2009.75. With a three-tier hierarchy this study contributes to our still limited knowledge of such multiples.  The multiple system is located at a distance of 44 pc and it is composed of main-sequence dwarfs with estimated masses of 0.74, 0.72, 0.57, and 0.78 solar masses for Aa, Ab, B and C, respectively (from Tokovinin et al. 2014, MNRAS, 443, 3082)
Right: SAM AO image of the T Tauri CVSO-28, a member of the ~8 Myr old 25 Ori cluster in the Orion OB1 association. At a separation of 1" and 4 mag fainter than the primary, the faint probable companion to the M1 CVSO-28 could well be a young brown dwarf at a projected separation of 400AU (Briceño et al. 2015, in preparation)
X-ray tails and  intracluster star formation in  the rich galaxy cluster  Abell 3627
The combination of Chandra observations with sharp SOAR Ha images allowed the authors to study the X-ray emission in ESO 137-001 and ESO 137-002, both late-type galaxies in the  cluster Abell 3627. They conclude that the high-pressure environment around these two galaxies is important for their bright X-ray tails and the intracluster star formation.
Left: XMM-Newton 0.5-2 keL mosaic of A3627 from an 18 ks observation. Right: composite X-ray (Chandra)/optical (SOAR) image pf ESO 137-001's tail (from Sun et al 2010, ApJ, 708, 946)

List of Scientific Publications using data obtained at SOAR