National Aeronautics and Space Administration (NASA)

0097-NPP-NOV23-JPL-Astrophys

11/1/2023 6:00:59 PM Eastern Time Zone

Star formation rates in galaxies depend on how much molecular H2 gas is present in dense cloud regions in which new stars form. Under most interstellar environments molecular H2 gas is not directly observed. CO line emission is used as proxy to trace the H2 gas in molecular clouds. However, there is a large uncertainty relating the observed CO line intensity to the underlying H2 column density. The presence of a significant fraction H2 molecular gas missed by CO as tracer, referred to as “CO-dark H2 gas“, has been inferred from a variety of probes including dust emission, gamma rays, and 158 micron CII fine structure line emission. (c.f. Velusamy et al. 2010, A&A 521, L18; Langer et al. 2010, A&A 521, L17). The dust continuum emission in IR, far-IR, and submm traces the high H2 molecular column densities. CII and CI fine structure lines trace the high H2 molecular column densities in the C+/C0/CO transition layers in molecular clouds which are missed by CO emission. The goal of this project is to investigate the distribution of the “CO-dark H2 gas“ across the Galaxy combining the CII, CI maps observed by Herschel HIFI (GOTC+ survey and follow up projects), with the dust emissions observed by Spitzer IRAC &MIPS, Herschel PACS & SPIRE, and submm maps by SCUBA & LABOCA. The results will be used to constraint the Xco factor (CO-H2 conversion factor defined the ratio of H2 column density to CO line intensity) which is widely used, but poorly constrained, and critical to our understanding of the star formation in galaxies and thus the galaxy evolution in the universe.

Location:
Jet Propulsion Laboratory
Pasadena, California

Field of Science:Astrophysics

Advisors:
Thangasamy Velusamy
Thangasamy.Velusamy@jpl.nasa.gov
818-354-6112

Applications with citizens from Designated Countries will not be accepted at this time, unless they are Legal Permanent Residents of the United States. A complete list of Designated Countries can be found at: https://www.nasa.gov/oiir/export-control.

Eligibility is currently open to:

• U.S. Citizens;
• U.S. Lawful Permanent Residents (LPR);
• Foreign Nationals eligible for an Exchange Visitor J-1 visa status; and,
• Applicants for LPR, asylees, or refugees in the U.S. at the time of application with 1) a valid EAD card and 2) I-485 or I-589 forms in pending status

• Degree: Doctoral Degree.