2002 REU Students' AAS & DPS Abstracts

AAS 201st Meeting, January, 2003
[44.01] The Chemical Composition of the Hyades
A. M. Boesgaard (U. Hawaii), J. L. Beard (Virginia Tech), J. R. King (UNLV)

The enrichment of various chemical elements with time in the Galaxy reveals the history of massive star formation and the production of supernovae. We have embarked on a study of elemental abundances in unevolved G stars in star clusters of a range in age to trace the evolution and mixing in the galactic disk.

We have obtained Keck/HIRES spectra of 17 Hyades stars with temperatures between 5000 and 6200 K and high signal-to-noise ratios (typically 500 - 700) in order to determine chemical abundances of G dwarfs in this 700 Myr old cluster. The spectra cover 5700 - 8100 A with some inter-order gaps. We have redetermined Fe and Li abundances and find good agreement with earlier results. Abundances for O and C and some other alpha-elements have been found as well as abundances of other light elements, Fe-peak elements, and rare earth elements. We compare the Hyades results with those from the old open cluster, M67. The Hyades at 700 Myr is metal-rich with [Fe/H] = +0.16 while M67 at 4.5 Gyr has solar metallicity of -0.04. Compared to M67, the Hyades has somewhat larger enhancements of C and O.

AAS 201st Meeting, January, 2003
[6.17U] Extremely Red Objects and Very Red Objects: A Wide Field Survey Around the Hubble Deep Field
E. Fernandez (New Mexico Institute of Mining and Technology), A. Barger (University of Hawaii)

We performed a deep, wide-field near-infrared survey of the Hubble Deep Field North region using the University of Hawaii's 2.2-meter telescope. We obtained complementary Suprime-Cam I-band observations of the same area using the Subaru 8.2-meter telescope. From the I-K colors of the galaxy sources, we were able to identify a sizeable population of Extremely Red Objects (EROs; I-K>4) and Very Red Objects (VROs; I-K>3.5). We report on the surface densities of these unusual populations and compare our results with those of other surveys.Fernandez, E.; Barger, A.
We performed a deep, wide-field near-infrared survey of the Hubble Deep Field North region using the University of Hawaii's 2.2-meter telescope. We obtained complementary Suprime-Cam I-band observations of the same area using the Subaru 8.2-meter telescope. From the I-K colors of the galaxy sources, we were able to identify a sizeable population of Extremely Red Objects (EROs; I-K>4) and Very Red Objects (VROs; I-K>3.5). We report on the surface densities of these unusual populations and compare our results with those of other surveys.

AAS 201st Meeting, January, 2003
[46.05U] Potential Brown Dwarfs Discovered in IfA Deep Imaging Survey
M. Graham (Oklahoma State University)

Deep, wide-field imaging surveys in the red and near-infrared are ideal for discovering substellar objects like brown dwarfs. A few of these surveys, such as 2MASS and SDSS, have already been successful in these attempts. A new wide-field red plus near-infrared survey was conducted by astronomers at the University of Hawaii's Institute for Astronomy (IfA) on the Subaru telescope. Five fields, each approximately 0.5 square degrees at varying galactic latitudes were observed in the Rc-, Ic-, and z'-bands.

Typical image quality of the survey is FWHM = 0.8". The total integration times for the Rc-, Ic-, and z'-bands were approximately 4500, 6500, and 9500 sec, respectively, for each field. For a 2" circular aperture the 5-sigma limiting magnitudes in Rc, Ic, and z' were approximately 27.1, 26.7, and 26.0, respectively.

One of the goals of the survey is the study of brown dwarfs. T dwarfs (or methane dwarfs) are the coolest, faintest, and most difficult to observe of the brown dwarf types. One T dwarf with spectral type T3-T4, IfA 0230-Z1, has already been confirmed from the IfA survey. In total the survey is expected to yield about 40 such objects.

Evaluation of the data has led to a large number of brown dwarf candidates. From four of the five fields in the survey, concentrating on the brightest (z'-magnitude < 23.0) stellar objects, approximately 38 excellent brown dwarf candidates were discovered. These are thought to be mostly late-L and T dwarfs.

This project was undertaken at the IfA as part of the summer 2002 Research Experience for Undergraduates program sponsored by the National Science Foundation. The presenter wishes to thank his project advisor at the IfA, Dr. Richard Wainscoat, as well as Dr. Eduardo Martin, who proposed the project as part of the IfA Deep Imaging Survey.

DPS 35th Meeting, 1-6 September 2003
[14.06] Spectrum of MUSES-C target asteroid 1998 SF36 from TRISPEC observations
C. Salyk (MIT), D.J. Tholen (IfA)

A spectrum spanning 0.5 - 2.5 microns was obtained for the asteroid 1998 SF36, the target of Japanese sample-return mission MUSES-C, which is scheduled for launch at the end of 2002. The asteroid was observed with the UKIRT telescope on Mauna Kea, on 2001 March 2 and 3 UT using a new instrument called TRISPEC (Triple Range Imager and SPECtrograph), developed by Nagoya University graduate students H. Nakaya, M. Watanabe and T. Yamamuro. Using three optical channels, this instrument allows simultaneous observations in a visible and two infrared bands, each with its own detector. Preliminary spectra confirm results of Binzel et al. (2001, Meteoritics Plan. Sci., 36, 1167-1172) that 1998 SF36 is an S-type asteroid. Further analysis of band-depth ratios should reveal more detailed information about its composition and classification. This work was supported by the National Science Foundation Research Experience for Undergraduates Site grant AST99-87896 to the University of Hawaii.