A Study of Absorption Features in the Three Micron Spectra of Molecular Cloud Sources with H$_2$O Ice Bands

T. Y. Brooke; K. Sellgren; R. G. Smith

doi:10.1086/176883

paper

A Study of Absorption Features in the Three Micron Spectra of Molecular Cloud Sources with H $_{2}$ O Ice Bands

arXiv:astro-ph/9509067 · doi:10.1086/176883

Abstract

New 3.3--3.6~ $μ$ m spectra were obtained of nine young stellar objects embedded in molecular clouds. An absorption feature at $\sim$ 3.47~ $μ$ m (2880~cm $^{- 1}$ ) with FWHM $\sim$ 0.09 $μ$ m (80 cm $^{- 1}$ ), first identified by Allamandola et al. (1992), was definitively detected toward seven objects, and marginally in the other two. The feature is better correlated with H $_{2}$ O ice than with the silicate dust optical depth in the data obtained to date. Assuming the feature is due to a C--H stretch absorption, the abundance of the C--H bonds averaged along the lines of sight is closely related to that of H $_{2}$ O ice. We interpret the correlation with H $_{2}$ O ice as indicating that the C--H bonds form together with H $_{2}$ O ice on grain surfaces in the molecular clouds, though other formation mechanisms are not ruled out. A second absorption feature at 3.25 $μ$ m (3080 cm $^{- 1}$ ) was detected toward NGC7538/IRS 1 and S140/IRS 1; this feature was first detected in spectra of MonR2/IRS 3 (Sellgren, Smith, \& Brooke 1994; Sellgren et al. 1995). There is as yet insufficient data to tell whether this feature is better correlated with H $_{2}$ O ice or silicates.

20 pages (37 kb), AASTex format. Also 9 Postscript figures (388 kB), tarred, compressed and uuencoded, added with 'figure' command. 9 figures (compressed PostScript) available from anonymous ftp at ftp://bessel.mps.ohio-state.edu/pub/sellgren/brookefig.tar.Z A complete (text+figs) compressed PostScript preprint is also available at ftp://bessel.mps.ohio-state.edu/pub/sellgren/brooke.ps.Z Hardcopy available upon request to [email protected]. Accepted by ApJ (March 1996)

A Study of Absorption Features in the Three Micron Spectra of Molecular Cloud Sources with H2​O Ice Bands

Abstract

Cited by in corpus (27)

A Study of Absorption Features in the Three Micron Spectra of Molecular Cloud Sources with H $_{2}$ O Ice Bands