• Freeman, W.
• Silva, D.
• Levesque, E.
• Massey, P.
• Olsen, K.
• Plez, B.
• Nordhaus, J.
• Clayton, G.
• Chatelain, J.
• Bright, Stacey N.
• Gordon, Karl

Abstract

We have gathered together a unique dataset for red supergiants (RSGs) in the Magellanic Clouds, which can be used to investigate the amount and nature of dust produced by RSGs in different environments. For a sample of 40 RSGs in each of the LMC and the SMC, we have obtained visible spectrophotometry (4000-9000 A), 2MASS photometry (JHK), and photometry in the Spitzer IRAC and MIPS bands. In addition, we have obtained Spitzer/IRS spectra for 10 stars in each galaxy. We will use our Monte Carlo radiative transfer models to analyze the emission from dust in the circumstellar shells. We plan to use the IRS data to make a systematic study of the dust properties in RSG shells in the LMC and SMC so that we can probe how they may vary with a large range of galactic metallicities. The derived stellar SEDs and extinction curves will be combined with the IRAC and MIPS photometry and IRS spectra as inputs to our Monte Carlo codes which will be used to study the composition, size distributions and clumpiness of the dust. We will model the dust shells using amorphous carbon and silicate dust grains as well as PAHs appropriate to these shells. This modeling will allow us to infer the total circumstellar dust mass around the sample RSGs. We will also consider whether the large global metallicity differences between galaxies lead to observable differences in the dust being produced by their RSGs. This project is being supported by NSF grant AST-0707691 and a LaSPACE Undergraduate Research Assistantship (NASA grant NNG05GH22H).

Topics

• impedance spectroscopy
• amorphous
• Carbon
• grain
• spectrophotometry