Cosmic Deuterium

The detection of deuterium and the calculation of a D/H ratio are important tools for determining the baryonic density of the Universe. This website catalogues four decades of deuterium-related articles.

As of July 2, 2020

Pasachoff continues working with Donald A. Lubowich of Hofstra University on observations of interstellar deuterium, which started with cosmological observations of its fundamental “spin-flip” spectral line at a frequency/wavelength of 327 MHz/92 cm (http://cosmicdeuterium.info;  website created by Terry-Ann Suer ’04; she is now a postdoc at the Harvard Department of Geosciences).   The Galactic D abundance is determined by a combination of big-bang nucleosynthesis; any Galactic nucleosynthesis processes (cosmic-ray spallation, n flux, or 4He flows); infall of halo or intergalactic gas; astration; mixing; deuterium astrochemistry, and outflow from Galactic winds and fountains.

Pasachoff, jointly with Donald Lubowich (Hofstra University);  Christian Henkel, Yan Gong, and Yaoting Kim  (Max-Planck Institute of Radio Astronomy);  Romane Le Gal (Harvard Smithsonian Center for Astrophysics); Evelyne Roueff (Observatoire de Paris, and Sorbonne Universités, UPMC); and David Weinberg (The Ohio State University, is extending his research on D to determine the D/H ratio in the extreme outer edge of the Milky Way (EOG) at 24 Kpc from the Galactic Center. This is an initial step in future research to measure the D abundances throughout the  Galaxy and determine the D/H gradient. The EOG (R > 18 kpc) is an environment with low gas density, low metallicity, low star-formation rate, and little or no perturbation from the spiral arms. The EOG is similar to the formation of the Galaxy and similar to dwarf irregular galaxies and damped Ly-alpha systems. The D/H ratio is predicted to be the largest in the Galaxy and close to the primordial or early Galactic D/H ratios, and the similar to largest D/H ratios observed in QSO absorption systems.   This research complements Pasachoff’s earlier work on the D/H ratio in the GC (D. A. Lubowich, Jay M. Pasachoff, Thomas J. Balonek, T. J. Millar, Christy Tremonti, Helen Roberts, and Robert P.  Galloway, Nature, 2000, 405, 1025), the D/H gradient out to 10 Kpc (Lubowich D. A., Pasachoff J. M., Proceedings IAU Symposium, No. 268, 2009, 179),  and the physical properties chemical a molecule cloud in the EOG (Ruffle, P., Millar, T. J., Roberts, H. R., Lubowich D. A, Henkel, C., Pasachoff, J. M, and Brammer, G., Astrophysical Journal, 2007, 671, 1766).

The remote observations, led by Lubowich, of DCO+ with the 30-meter IRAM (Institut de Radioastronomie Millimétrique) radio telescope on Pico Veleta in the Spanish Sierra Nevada were done June 24 – June 30, for 27 hours and extended the August 2019 marginal detection of DCO+ from 14 hr due to extremely poor observing weather for these millimeter-wavelength observations.   This is currently the only telescope in the world  that can observe J= 1-0 and J= 2-1  lines of DCO+ .The research group includes astrochemists and experts in astration and galactic  chemical evolution and astration who will fit the observations to astrochemistry/deuterium fractionation models that include gas-phase, gas-grain surface chemistry, and cosmic-ray ionization models plus ortho/para spin states for hydrogen species to obtain the D/H ratio from the DCO+/HCO+ ratio.  The team detected the DCO+ J = 1- 0 (Tmb = 0.0104 K +/- 0.0017 K) and the DCO+ J = 2-1 (Tmb =  0.0065 K  ± 0.00103 K) lines which are the first detention of D in the Galaxy beyond 10 Kpc from the GC). We did not detect C2D, DCN, or N2D+ In order determine the physical conditions and improve the deuterium astrochemical models in this molecular cloud.  Observation were also conducted for mm-wave transitions of CO, 13CO, C18O, CN, HCO+ CS, HCN, H13CN, DCN, C2H, SO, C3H2, H2CO, HNC, CH3OH, N2H+, and HCS+, and C2D.  All of these molecules were detected except for DCN, N2H+, H13CN, and C2D.

Site arranged by Terry-Ann Suer, Williams College '05, in collaboration with Jay M. Pasachoff. Special thanks to NASA Astrophysics Data System.
Last modified July 2, 2020 Webmaster