2007/07/24 by J. E. Chiar, K. Ennico, Kimberly Ennico +13 · 1 citation
Chemistry · Physics and Astronomy · #Absorption (acoustics) #Analytical Chemistry (journal) #Astro and Planetary Science #Astronomy #Astrophysics #Astrophysics and Star Formation Studies #Chemistry #Extinction (optical mineralogy) #Feature (linguistics) #Infrared #Line-of-sight #Materials science #Meteorology #Optical depth #Optics #Physics #Silicate #Stellar, planetary, and galactic studies #astro-ph
paper · pdf · doi:10.1086/521789
11 pages including 2 figures, 1 table. Accepted for publication in ApJ Letters, 23 July 2007
arxiv created 2007/07/24 · openalex publication_date 2007/08/20 · arxiv updated 2009/12/01 · openalex created_date 2016/06/24 · openalex updated_date 2026/08/05
We have examined the relationship between the optical depth of the 9.7 μm silicate absorption feature (τ 9.7 ) and the near-infrared color excess, E ( J - K s ), in the Serpens, Taurus, IC 5146, Chameleon I, Barnard 59, and Barnard 68 dense clouds/cores. Our data set, based largely on Spitzer IRS spectra, spans E ( J - K s ) = 0.3-10 mag (corresponding to visual extinction between about 2 and 60 mag). All lines of sight show the 9.7 μm silicate feature. Unlike in the diffuse ISM where a tight linear correlation between the 9.7 μm silicate feature optical depth and the extinction ( A V ) is observed, we find that the silicate feature in dense clouds does not show a monotonic increase with extinction. Thus, in dense clouds, τ 9.7 is not a good measure of total dust column density. With few exceptions, the measured τ 9.7 values fall well below the diffuse ISM correlation line for E ( J - K s ) > 2 mag ( A V > 12 mag). Grain growth via coagulation is a likely cause of this effect.