IPAC Visiting Graduate Fellowship Talks - Jonathan Gagne and Wanggi Lim

Wanggi Lim: We present photometric and spectroscopic tests of MIR to FIR extinction laws toward IRDC G028.36+00.07, a potential site of massive star formation. Lim & Tan (2014, hereafter LT14) developed methods of FIR extinction mapping of this source using Spitzer-MIPS 24 micron and Herschel-PACS 70 micron images, and extending the MIR 8 micron mapping methods of (Butler & Tan 2012, hereafter BT12), finding evidence for grain growth in the highest mass surface density regions. Here we present initial results of spectroscopic infrared extinction (SIREX) mapping using Spitzer-IRS (14 to 38 micron) data of the same IRDC. These methods allow us to measure the SED of the diffuse Galactic ISM, which we compare to theoretical models of Draine & Li (2007), as well as to search for opacity law variations with mass surface density within the IRDC. By comparison with theoretical dust models, e.g., Ossenkopf & Henning (1994) and Ormel et al. (2011), we are able to search for compositional signatures of the grain ices, such as water and methanol. We find evidence for generally flatter MIR to FIR extinction laws as mass surface density increases, strengthening the evidence for grain and ice mantle growth in higher density regions. ************************ Jonathan Gagne: In this talk, I will present our efforts in developing reduction pipelines and procedures to measure precise radial velocities (RVs) of M stars in the near-infrared using CSHELL. I will show how a deep understanding of the instrument is required to achieve precisions below ~ 50 m/s on individual RV measurements. I will then describe our most up-to-date methods for extracting CSHELL spectra as well as the unique pipeline that our team developed for measuring RV variations, which uses a methane isotopologue gas cell for wavelength reference, and does not require a stellar template.