AAS meeting, January 2011, Seattle, Washington
Searching for Brown Dwarfs and Brown Dwarf Binaries in Upper Scorpius, the Trapezium, and IC 348 Using the UKIDSS Galactic Cluster Survey
Marin M. Anderson (University of California, Berkeley), B. Biller(Institute for Astronomy, University of Hawai`i)
We conducted a survey of three young star-forming regions using the UKIRT Infrared Deep Sky Galactic Cluster Survey (GCS) Database Release 7 to identify a sample of brown dwarf and brown dwarf binary system candidates. The known distances to and ages of the young star-forming regions queried (the Upper Scorpius association, the Trapezium Cluster in Orion, and IC 348 in the Perseus OB Association) allow us to estimate masses for the candidate brown dwarfs, using appropriate evolutionary models (Chabrier et al. 2000, Baraffe et al. 2002, Baraffe et al. 1998). Brown dwarf candidates were selected based on their infrared luminosity (J, H, and K bands) and a corresponding drop-off in shorter wavelength luminosity (Z and Y bands). A series of color cuts, taken from Lodieu et al. (2006), were applied to (Z - J, Z) color-magnitude diagrams to select the fainter, redder candidates from the brighter sources in the survey regions. Cross-correlation of the GCS data with the 2MASS database provided a second epoch of information, further narrowing the list of brown dwarf candidates to only those proper motion members of the surveyed clusters. The continued discovery and classification of young brown dwarfs in star-forming regions allows us to better model the substellar initial mass function and understand substellar formation processes. In particular, our survey of Upper Sco produced 170 brown dwarf and low-mass stellar candidates, and 4 candidate brown dwarf binary systems, which were used to derive a substellar IMF that corresponds well with other substellar IMFs found from previous surveys of different regions in Upper Sco. This work was conducted through a Research Experience for Undergraduates (REU) position at the University of Hawai`i's Institute for Astronomy, with funding provided by the NSF.
Molecular Hydrogen in the Galactic Wind of M82
Joshua Fuchs (Rhodes College), D. Rupke (Institute for Astronomy, University of Hawai`i)
A more complete understanding of the multiphase nature of galactic winds is necessary to constrain the dominant carriers of mass and energy. Recent studies of near-infrared lines of molecular hydrogen in the galactic wind of M82 have revealed that the warm H2 is extended more than 3 kpc from the nucleus of the galaxy. This project used Gemini NIR spectroscopy to study the velocity structure of the warm molecular hydrogen, which in turn provides information on the dynamical importance of this newly discovered, extended phase. We also present near-infrared shock diagnostics of the M82 wind. This work was conducted by a Research Experience for Undergraduates (REU) position at the University of Hawai`i's Institute for Astronomy and funded by the NSF.
Deriving Telescope Properties Using Daytime Sky Observations
Shannon Hall (Whitman College), D. Harrington (Institute for Astronomy, University of Hawai`i)
High-resolution spectropolarimetry in night-time astronomy is a relatively new but powerful remote sensing technique. In order to make accurate spectropolarimetric measurements using large telescopes, it is necessary to derive the calibration of the telescope by recovering the Mueller matrix elements. These calibrations are typically difficult to recover and are functions of wavelength and telescope pointing. We demonstrate a novel technique using observations of the bright, highly polarized, and easily accessible daytime sky. With the calibration of the AEOS 3.67m telescope on Haleakala and the new low-resolution spectropolarimeter LoVIS, we illustrate the spectropolarimetric accuracy with observations of AB Aurigae.
Modeling the Interior Structure of Tempel 1
Victoria Hartwick (University of Wisconsin - Madison), G. Sarid (Institute for Astronomy, University of Hawai`i)
Processes that determine the correlation between nuclear activity and coma structure in comets are largely unknown. Since ground-based observations of comet nuclei are impossible, complex models present the best current method for interpreting coma changes during orbit, with the exception of in situ observations. Using data collected from the Deep Impact mission in 2005 and ground-based observations from 1983 to 2005, we present a preliminary model of the interior activity of Tempel 1. Matching of output production rates to observed production rates provides information about the model’s accuracy.
Observing Young Variable Stars Using WFCAM at UKIRT
Thomas Rice (Harvard-Smithsonian Center for Astrophysics), C. Aspin (Institute for Astronomy, University of Hawai`i), S. J. Wolk (Harvard-Smithsonian Center for Astrophysics)
We present the results from the analysis of 120 epoch time-series photometry of a 1 square degree region of the Lynds 1003 dark cloud in the Cygnus OB7 association. Using the Wide-Field imaging camera (WFCAM) on UKIRT, we were able to obtain almost-nightly J,H,K' photometry over three observing seasons of over 100,000 stars with photometric uncertainty better than 0.02 mag in the range J=10-16 mags and better than 0.5 mag down to J=19.5. From the data, we establish criteria for determining variability based on the least-varying sources. We report the discovery of both periodic and stochastic variability for a number of young T Tauri stars. We compare statistical properties of known cluster members with the general field population, and discuss physical models for some of the more interesting sources. This work was funded by the NSF REU program.
Searching for Young Stars in Northern Orion
Laurie Urban (Northern Arizona University), A. Kraus (Institute for Astronomy, University of Hawai`i)
The Orion Molecular Cloud contains many known star-forming regions mostly located in the southern parts of the constellation. However, northern Orion is largely unsurveyed outside of a few well-established clusters, meaning there could be more sites of ongoing star formation. We have conducted a search for young stars in northern Orion to find new star-forming regions. Using the MG1 Variable Star Survey, we identified 2118 variable stars spanning a region of ~30 deg2 from R.A. = 4h 00m to 6h 30m and Dec = 2.9 to 3.7 degrees. These stars’ variability could result from accretion or spots, which are common characteristics of young stars. We use several methods to detect candidate young stars from these data: selection cuts with color-magnitude diagrams (CMDs), measurement of proper motions, and visual inspection of the source images. We make cuts to only include stars that have CMD positions consistent with the Orion sequence, have proper motions within 3 sigma of known Orion members, and are not contaminated by other nearby sources. These cuts identify an area between 5h 20m and 5h 52m in R.A. with a significant overdensity of 74 young star candidates. We will discuss in detail our selection cuts and the implication of these discoveries. This work was conducted by a Research Experience for Undergraduates (REU) position at the University of Hawai`i's Institute for Astronomy and funded by the NSF.
The Search for Molecular Hydrogen in the IR Second Solar Spectrum
Amanda White (Drexel University), J. R. Kuhn (Institute for Astronomy, University of Hawai`i)
Molecular hydrogen in sunspots should be a dominant molecular species and an important factor in spot dynamics. The rotational and vibrational transitions of molecular hydrogen are extremely weak in comparison to the overall intensity spectrum of the Sun, making the molecule difficult to observe. Molecular lines, however, are prominent in the linearly polarized spectrum of the Sun, also called the Second Solar Spectrum. Using the Scatter-free Observatory for Limb Active Regions and Coronae (SOLAR-C) located on the summit of Haleakala and a spectropolarimeter, we have observed the linear polarized spectrum of the Sun near the 2.128 micron line of molecular hydrogen and begun to catalog the second solar spectrum in the IR. This work was conducted as part of a Research Experience for Undergraduates (REU) position at the University of Hawai`i's Institute for Astronomy and funded by the NSF.