Research
Research
Star formation scaling relations in NGC 300
Nearby galaxies provide the perfect laboratory in which to study star formation by virtue of providing a more complete sample of molecular clouds all at a single distance. I am working with Charles Lada and Jan Forbrich to measure star formation rates (SFRs, via Spitzer mid-IR, GALEX UV, and narrow-band photometry) and gas (via CO J=2-1 and other tracers) in the star-forming regions of the local (d=1.9 Mpc) galaxy NGC 300. Broadly, we hope to better understand the Schmidt-Kennicutt (SFR vs. gas mass) relation on the full range of scales from individual clouds to cloud complexes to entire galaxies.
The Role of Pressure in Molecular Clouds and Cores
It is commonly assumed that pressure gradients are negligible in molecular clouds, and thus that knowing the kinetic and potential energies provides a complete description of the virialization state of these clouds. I am working on a project with Alyssa Goodman to test this assumption by estimating the pressure observationally as a function of position in several clouds such as Perseus using data from the COMPLETE survey, and comparing the results to simulations of star-forming regions.
Variability in Young Stars
Young stellar objects (YSOs) are often variable in the mid-infrared, yet little is known of the physical mechanisms that drive these changes. I worked with Kevin Covey and the YSOVAR collaboration to explore this question through a spectral variability study of several stars in the rho-Ophiuchus star forming region. We found that although mass accretion rates can vary greatly over short (days to weeks) timescales in active YSOs, there is no direct correlation between such behavior and the mid-infrared photometric variability we observe with Spitzer. Our paper is now accepted, is on the arXiv (http://arxiv.org/abs/1209.5749), and will appear in PASP, November 2012.
primary collaborators
Harvard/Sao
Charles Lada
Alyssa Goodman
UNIVERSITY OF VIENNA
Jan Forbrich
LOWELL OBSERVATORY
Kevin Covey
Indiana University
Constantine Deliyannis
Jeff Cummings
star formation
stellar and chemical evolution
rho Ophiuchus (photo credit: Michael Stecker)
NGC 300 (photo credit: ESO archive)
Cloudshine in Perseus (Foster & Goodman 2006)
Spitzer Space Telescope (credit: NASA/IPAC)
Lithium is one of the most significant elements in the Universe: it is a primordial element, with small amounts having been created shortly after the Big Bang, and is not synthesized in main sequence stars. Furthermore, it is easily destroyed in stellar interiors, and thus represents a unique archaeological probe of both cosmology and stellar evolution. However, the depletion mechanisms are not yet well understood. For example, standard models predict that the Sun should have depleted a factor of ~100 more Li than the abundance we observe. Is such depletion unusual for solar-type stars? For my senior undergraduate honors thesis at Indiana University with Constantine Deliyannis, I measured Li abundances in stars across the main sequence in the solar-age, solar-metallicity open cluster M67. We confirmed that Li depletion increases sharply with decreasing effective temperature, and our preliminary results place the Sun’s abundance in the midst of the locus of that of several solar-type stars in M67, hinting that Li depletion may indeed be common in stars like the Sun.
How weird is our Sun?