Nathan R. Crockett

Ph.D. Astronomy & Astrophysics 2013
University of Michigan

M.S. Astronomy & Astrophysics 2009
University of Michigan

B.S. Astronomy & Physics 2004
University of Arizona

Research Interests

Complex Molecules in Space

There are currently over 150 molecules that have been detected in the interstellar medium (ISM). Included within this chemical inventory are simple 2-4 atom species (e.g. CO, H2O, and NH3) as well as more complex organics that contain over 5 constituent atoms. Among the organics detected in the ISM are alcohols (e.g. CH3OH and C2H5OH), ethers (e.g. CH3OCH3), cyanides (e.g. CH3CN and C2H3CN), esters (e.g. CH3OCHO), and many other types of organics. The existence of such molecular diversity points to an intricate chemistry that is occurring in the ISM which is still poorly understood. Hot cores, the birth sites of high-mass stars, stand out as the most prodigious emitters of molecular line radiation in the Galaxy and contain high abundances of complex organics making them superb laboratories for studying how molecules form in the ISM. My research focuses on using mm, sub-mm, and far-infrared observations to constrain the physical environment in which complex molecules are found in the ISM and the chemical pathways by which these species are produced.

For my PhD dissertation, I led a team of 18 people in the analysis and modeling of a broadband spectrum toward the Orion Kleinmann-Low Nebula (Orion KL), one of the most chemically rich regions in the Milky Way. This spectrum (the largest of its kind toward Orion KL) contains approximately 15,000 emission lines from 39 molecules (79 isotopologues) and probes a region of the electromagnetic spectrum that was previously unexplored at high spectral resolution. At Caltech, I am expanding work from my PhD using high spatial resolution maps, obtained with ALMA, to understand the origin of certain organics in the ISM and pinpoint the ultimate heating source powering the extremely luminous Orion KL nebula, which has, up until now, remained a mystery.

Protoplanetary Disk Evolution

Protoplanetary Disks provide the raw materials from which mature planetary systems emerge. Constraining the chemical and physical structure of these objects is thus critical to understanding how our own Solar System came to exist and how planets form around other stars. My research focuses on using near-infrared spectra obtained with the NIRSPEC instrument on the Keck II telescope to probe the structure of these young systems by analyzing CO rovibrational lines which trace gas within 10 AU of the central star. In particular, I am analyzing a dataset of approximately 5000 M-band spectra toward 18 sources obtained over a period of 4 years. Using these observations, we are looking for variability in the line profiles which may be indicative of embedded protoplanets. These data are also unique in that we take advantage of Keck's adaptive optics capabilities to constrain the spatial extent of the CO emitting gas using a technique known as specto-astrometry, a method by which we can probe size scales less than 1 AU in nearby disks.

More information can be found on my personal website here.

Selected Publications

My full curriculum vitae can be found here (Click for PDF)

Zhang, K., Crockett, N. R., Salyk, C., Pontoppidan, K., Turner, N. J., et al., "Dimming and CO Absorption toward the AA Tau Protoplanetary Disk: An Infalling Flow Caused by Disk Instability", The Astrophysical Journal, 2014, submitted

Crockett, N. R., Bergin, E. A., Neill, J. L., Favre, C., Blake, G. A., et al., "Herschel Observations of EXtra-Ordinary Sources: Analysis of the HIFI 1.2 THz Wide Spectral Survey toward Orion KL. II. Chemical Implications", The Astrophysical Journal, 2014, submitted

Crockett, N. R., Bergin, E. A., Neill, J. L., Favre, C., Schilke, P., et al., "Herschel Observations of EXtra-Ordinary Sources: Analysis of the HIFI 1.2 THz Wide Spectral Survey toward Orion KL. I. Methods", The Astrophysical Journal, 2014, 787, 112.

Neill, J. L., Bergin, E. A., Lis, D. C., Schilke, P., Crockett, N. R., et al., "Herschel Observations of EXtra-Ordinary Sources: Analysis of the Full Herschel/HIFI Molecular Line Survey of Sagittarius B2(N)", The Astrophysical Journal, 2014, 789, 8.

Crockett, N. R., Bergin, E. A., Neill, J. L., Black, J. H. Blake, G. A., Kleshcheva, M., "Herschel Observations of EXtra-Ordinary Sources: H2S as a Probe of Dense Gas and Possibly Hidden Luminosity toward the Orion KL Hot Core", The Astrophysical Journal, 2014, 781, 114.

Neill, J. L., Crockett, N. R., Bergin, E. A., Pearson, J. C., & Xu L. H., "Deuterated Molecules in Orion KL From Herschel/HIFI", The Astrophysical Journal, 2013, 777, 85.

Wang, S., Bergin, E. A., Crockett, N. R., Goldsmith, P. F., Lis, D. C., et al. "Herschel Observations of EXtra-Ordinary Sources (HEXOS): Methanol as a Probe of Physical Conditions in Orion KL", Astronomy & Astrophysics, 2011, 527, 95.

Crockett, N. R., Bergin, Wang, S., Lis, D. C., Bell, T. A., et al., "Herschel Observations of EXtra-Ordinary Sources (HEXOS): The Terahertz Spectrum of Orion KL Seen at High Spectral Resolution", Astronomy & Astrophysics, 2010, 521, L21.