Near-IR Spectroscopy of Simple Organic Molecules in GV Tau N Dr. Erika Gibb June 19, 2014

Motivation Understanding how volatiles evolve from dark clouds to disks around young stars to protoplanets –Where/how are volatiles processed? –How are volatiles distributed through disks? –Where did Earth’s water, organics come from? Method –Infrared spectroscopy of clouds, disks and comets –Comparison with chemical models

Keck Observatory 10 meter telescope NIRSPEC: Near-Infrared Spectrometer High resolving power ( /  ~ 25,000) 2-5  m region Simple organic molecules have ro-vibrational transitions

Anatomy of a Disk

Surface layer  emission lines Follow the Volatiles: Disks Spectral features can be used to determine temperature, then combine with disk model to estimate location → non unique solutions

Intermediate layer  rich ion-molecule chemistry, absorption Lahuis et al Follow the Volatiles: Disks

Follow the Volatiles: Disks/Comets? Midplane  cold, volatiles frozen onto grains

GV Tau Low mass binary system Close to edge on Surrounded by circumbinary material Warm HCN & C 2 H 2 absorption toward GV Tau N – Located in warm molecular layer of circumstellar disk (Gibb et al. 2007; Doppman et al. 2008)

GV Tau Recently reported CH 4 … first detection in a disk (Gibb & Horne 2013) Note: Molecules like C 2 H 2 & CH 4 have no pure rotational transitions and cannot be done with ALMA.

GV Tau

CH 4 Toward GV Tau CH 4 in GV Tau N disk –T rot ~750 K

CH 4 Toward GV Tau CH 4 in GV Tau N disk –T rot ~750 K

Where is the gas located? Walsh et al. 2010

Results T rot ~ 750 K Abundances? –If assume gas is co-spatial –HCN/CH 4 ~ 50% –(similar to ratio found in comets) Spectral features are variable –Indicating structure/clumpiness in inner disk?

Mystery left to solve: Why are the 2006 and 2010 spectra so different?

Acknowledgements Students –Logan Brown, Nathan Roth Disks –David Horne (Washington College) Funding –NASA Exobiology, NSF Stellar Astronomy

Disk Processing Surface of disk processed by UV, X-ray, cosmic ray Inner region: ion-molecule chemistry, photochemistry Outer region: grain-surface, ion-molecule, neutral-neutral reaction Bulk motions: turbulence, migration inward  vertical & radial mixing