Detection of Deuterated Hydrocarbon Nanoparticles in the Whirlpool Galaxy, M51
Journal article, 2025
Deuteration of hydrocarbon material, including polycyclic aromatic hydrocarbons (PAHs), has been proposed to account for the low gas-phase abundances of D in the interstellar medium (ISM). JWST spectra of four star-forming regions in M51 show an emission feature, with central wavelength similar to 4.647 mu m and FWHM 0.0265 mu m, corresponding to the C-D stretching mode in aliphatic hydrocarbons. The emitting aliphatic material is estimated to have (D/H)aliph. approximate to 0.17 +/- 0.02-a factor of similar to 104 enrichment relative to the overall ISM. On similar to 50 pc scales, deuteration levels toward four H ii regions in M51 are 2-3 times higher than in the Orion Bar photodissociation region (PDR), with implications for the processes responsible for the formation and evolution of hydrocarbon nanoparticles, including PAHs. The deuteration of the aliphatic material is found to anticorrelate with helium ionization in the associated H ii, suggesting that harsh far-UV radiation may act to lower the deuteration of aliphatics in PDRs near massive stars. No evidence is found for deuteration of aromatic material, with (D/H)arom. less than or similar to 0.016: deuteration of the aliphatic material exceeds that of the aromatic material by at least a factor of 10. The observed levels of deuteration may account for the depletion of D observed in the Galactic ISM. If so, the 4.65 mu m feature may be detectable in absorption.
Author
B. T. Draine
Princeton University
Karin Sandstrom
University of California at San Diego (UCSD)
Daniel A. Dale
University of Wyoming
J. D. T. Smith
University of Toledo
Ryan Chown
Ohio State University
Grant P. Donnelly
University of Toledo
Sara E. Duval
University of Toledo
Cory M. Whitcomb
University of Toledo
Angela Adamo
Stockholm University
L. Armus
California Institute of Technology (Caltech)
Danielle A. Berg
University of Texas
Torsten Boker
European Space Agency (ESA)
Alberto D. Bolatto
University of Maryland
Martha L. Boyer
Space Telescope Science Institute (STScI)
Daniela Calzetti
University of Massachusetts
Brandt Gaches
Chalmers, Space, Earth and Environment, Astronomy and Plasmaphysics
Karl D. Gordon
Space Telescope Science Institute (STScI)
L. K. Hunt
Istituto nazionale di astrofisica (INAF)
R. C. Kennicutt
University of Arizona
Texas A&M University
Ralf S. Klessen
Harvard University
Harvard-Smithsonian Center for Astrophysics
Heidelberg University
Thomas S. Y. Lai
California Institute of Technology (Caltech)
Adam K. Leroy
Ohio State University
Sean T. Linden
University of Arizona
Alex Pedrini
Stockholm University
Noah S. J. Rogers
Northwestern University
Julia C. Roman-Duval
Space Telescope Science Institute (STScI)
Eva Schinnerer
Max Planck Society
Evan B. Skillman
University of Minnesota
Fabian Walter
Max Planck Society
Tony D. Weinbeck
University of Wyoming
Benjamin F. Williams
University of Washington
Astrophysical Journal Letters
2041-8205 (ISSN) 2041-8213 (eISSN)
Vol. 984 2 L42Subject Categories (SSIF 2025)
Astronomy, Astrophysics, and Cosmology
Meteorology and Atmospheric Sciences
DOI
10.3847/2041-8213/adc991