KPNO REU Students at the 215th AAS Meeting (January 2010)

The opportunity to present the findings of their original research at the most important national meeting of US astronomy is arguably one of the most prized benefits enjoyed by KPNO REU students. All six of the 2009 summer students will attend the 215th meeting of the American Astronomical Society (AAS) at Washington, D.C. in January 2010.

The abstracts of the REU student posters are reproduced below.

Searching for Planetary Pollution: Stellar Parameters for 10 Stars with Planets

Davin C. Flateau (University of Cincinnati), Bulletin of the American Astronomical Society, 42, 328 (2010)

It has been observed that stars with known planets are more metal-rich than surrounding field stars. One explanation is the accretion of hydrogen-depleted planetary matter into the atmospheres of the planet hosts. In such a case, trends of increasing abundances with increasing element Tc may be expected for a given host star. The presence of 6Li, which is expected to be completely destroyed during the pre-main sequence evolution of solar-type stars, could also be a strong accretion signal. High-resolution spectra (R 120,000, S/N=500-850) were obtained for 10 solar-type stars with planets in order to search for these accretion signatures. As the initial step in our analysis, stellar parameters - effective temperatures, surface gravities, and microturbulent velocities and Fe abundances - of the target stars have been derived from Fe I and Fe II lines via measurements of equivalent widths. Here we present the derived stellar parameters, Fe abundances, and the abundances of other elements of our planetary host sample. These results are complemented by our search for 6Li in these stars, which is presented in a companion paper at this meeting.

Near IR Light Profiles of Massive Elliptical Galaxies at z~1

Erica D. Jones (Louisiana State University), & J. M. Lotz (NOAO), Bulletin of the American Astronomical Society, 42, 484 (2010)

Current galaxy evolution models support recent observations revealing that massive elliptical galaxies are small and compact at high redshift. As these galaxies evolve, they proceed to increase significantly in size as measured in rest-frame blue light, yet the total stellar mass estimates are very similar. Using HST NIC3 F110W and F160W images, we examine eleven massive elliptical galaxies at z~1 in rest-frame red light. Our best-fit Sersic profiles indicate that these galaxies have small effective radii, consistent with rest-frame blue studies, although larger radii cannot be ruled out at the 3-sigma confidence level. We compute stellar mass density profiles. Our results reveal that light can be seen out to a radius of at least 16 kpc, which is consistent with outer stellar mass profiles of local elliptical galaxies. This contradiction may be explained by biases in Sersic profile fitting due to the dominance of background noise at large radii. Our results suggest that massive elliptical galaxies at z~1 may not be as dissimilar to local galaxies as previously thought.

A Search For Planetary Nebulae in the Globular Cluster Population of M31

Evan Kaplan (Vassar College), G. Jacoby (NOAO), H. Hwang (CEA, Saclay, France), M. Lee (Seoul National University, Republic of Korea), J. Davies (NOAO), K. Herrmann (Lowell Observatory), L. Fullton (Nagravision, Switzerland), R. Ciardullo (Penn State University), O. De Marco (Macquarie University, Australia), & J. Feldmeier (Youngstown State University), Bulletin of the American Astronomical Society, 42, 472 (2010)

The formation of planetary nebulae (PNe) is traditionally thought to occur during the late stages of stellar evolution in individual 1-8 solar mass stars. However, the presence of 4 PNe in the 150 Milky Way (MW) globular clusters (GCs) suggests other methods may be required, such as interacting binaries or mergers, to enhance the very low progenitor masses. Using WIYN/Hydra medium resolution spectra of 455 GCs in M31, we searched for spectral and kinematic tracers of GC PNe. The results yielded 10 - 14 very likely candidate PNe, which is statistically proportional tothe number found in the MW sample. However, the lack of PNe from x-ray GCs fails to support the interacting binary theory.

A Template-Independent Technique for Obtaining Photometric Redshift Estimates for Dusty, Star-forming Galaxies

Stephen J. Messenger (University of Missouri)), A. Pope (NOAO), A. Dey (NOAO), Bulletin of the American Astronomical Society, 42, 247 (2010)

Spectroscopic redshift determinations of dusty, high redshift galaxies (e.g. submillimeter galaxies) are challenging due to their faintness at optical wavelengths and, thus, the large amount of telescope time required. These factors drive the need for alternative methods of redshift determination. A promising avenue for creating such a method involves using the 1.6 micron stellar bump of dusty, star-forming galaxies. Using a large sample of submillimeter galaxies and Spitzer-selected dusty galaxies with spectroscopic redshifts, we developed a new technique for estimating photometric redshifts which does not rely on the use of templates. These redshift estimates depend solely on the Spitzer IRAC+MIPS fluxes and, therefore, can be applied to large submillimeter surveys with these data. In particular, we applied our method to the submillimeter galaxies in the SHADES survey and the Dust Obscured Galaxies (DOGs) in the Bootes field. Our method has shown itself to be a quick, easy, and inexpensive way to obtain photometric redshifts for dusty, high redshift galaxies.

Searching for Flickering Giants in the Ursa Minor Dwarf Spheroidal Galaxy

Edward J. Montiel (University of Arizona), K. J. Mighell (NOAO), Bulletin of the American Astronomical Society, 42, 274 (2010)

We present a preliminary analysis of three epochs of archival Hubble Space Telescope (HST) Wide Field Planetary Camera 2 (WFPC2) observations of a single field in the Ursa Minor (UMi) dwarf spheroidal (dSph) galaxy. These observations were obtained in 2000, 2002, and 2004 (GO-7341, GO-8776, GO-2004; PI: Olszewski). We expand upon the work of Mighell and Roederer (2004) who reported the existence of low-amplitude variability in red giant stars in the UMi dSph. We report the 16 brightest point sources (F606W <= 21.5 mag) that we are able to match between all 3 epochs. The 112 observations were analyzed with HSTphot. We tested for variability with a chi-squared statistic that had a softened photometric error where 0.01 mag was added in quadrature to the reported HSTphot photometric error. We find that all 13 stars and 3 probable galaxies exhibit the same phenomenon as described in Mighell and Roederer with peak to peak amplitudes ranging from 54 to 125 mmags on 10 minute timescales. If these objects were not varying, the deviates should be normally distributed. However, we find that the deviates have a standard deviation of 1.4. This leads to three possible conclusions: (1) the observed phenomenon is real, (2) an additional systematic error of 7 mmag needs to be added to account for additional photometric errors (possibly due to dithering), or (3) there was a small instrumental instability with the WFPC2 instrument from 2000 to 2004.

Updated on June 21, 2022, 10:03 am