TY - JOUR

T1 - Water abundance variations around high-mass protostars

T2 - HIFI observations of the DR21 region

AU - Van Der Tak, F. F.S.

AU - Marseille, M. G.

AU - Herpin, F.

AU - Wyrowski, F.

AU - Baudry, A.

AU - Bontemps, S.

AU - Braine, J.

AU - Doty, S.

AU - Frieswijk, W.

AU - Melnick, G.

AU - Shipman, R.

AU - Van Dishoeck, E. F.

AU - Benz, A. O.

AU - Caselli, P.

AU - Hogerheijde, M.

AU - Johnstone, D.

AU - Liseau, R.

AU - Bachiller, R.

AU - Benedettini, M.

AU - Bergin, E.

AU - Bjerkeli, P.

AU - Blake, G.

AU - Bruderer, S.

AU - Cernicharo, J.

AU - Codella, C.

AU - Daniel, F.

AU - Di Giorgio, A. M.

AU - Dominik, C.

AU - Encrenaz, P.

AU - Fich, M.

AU - Fuente, A.

AU - Giannini, T.

AU - Goicoechea, J.

AU - De Graauw, Th

AU - Helmich, F.

AU - Herczeg, G.

AU - Jørgensen, J.

AU - Kristensen, L.

AU - Larsson, B.

AU - Lis, D.

AU - McCoey, C.

AU - Neufeld, D.

AU - Nisini, B.

AU - Olberg, M.

AU - Parise, B.

AU - Pearson, J.

AU - Plume, R.

AU - Risacher, C.

AU - Santiago, J.

AU - Wampfler, S.

AU - WISH team

PY - 2010/10/15

Y1 - 2010/10/15

N2 - Context. Water is a key molecule in the star formation process, but its spatial distribution in star-forming regions is not well known. Aims. We study the distribution of dust continuum and H2O and 13CO line emission in DR21, a luminous star-forming region with a powerful outflow and a compact H ii region. Methods. Herschel-HIFI spectra near 1100 GHz show narrow 13CO 10-9 emission and H2O 111-000 absorption from the dense core and broad emission from the outflow in both lines. The H2O line also shows absorption by a foreground cloud known from ground-based observations of low-J CO lines. Results. The dust continuum emission is extended over 36" FWHM, while the 13CO and H 2O lines are confined to ≈ 24" or less. The foreground absorption appears to peak further North than the other components. Radiative transfer models indicate very low abundances of ∼2×10-10 for H2O and ∼8×10-7 for 13CO in the dense core, and higher H2O abundances of ∼4×10-9 in the foreground cloud and ∼7×10-7 in the outflow. Conclusions. The high H2O abundance in the warm outflow is probably due to the evaporation of water-rich icy grain mantles, while the H2O abundance is kept down by freeze-out in the dense core and by photodissociation in the foreground cloud.

AB - Context. Water is a key molecule in the star formation process, but its spatial distribution in star-forming regions is not well known. Aims. We study the distribution of dust continuum and H2O and 13CO line emission in DR21, a luminous star-forming region with a powerful outflow and a compact H ii region. Methods. Herschel-HIFI spectra near 1100 GHz show narrow 13CO 10-9 emission and H2O 111-000 absorption from the dense core and broad emission from the outflow in both lines. The H2O line also shows absorption by a foreground cloud known from ground-based observations of low-J CO lines. Results. The dust continuum emission is extended over 36" FWHM, while the 13CO and H 2O lines are confined to ≈ 24" or less. The foreground absorption appears to peak further North than the other components. Radiative transfer models indicate very low abundances of ∼2×10-10 for H2O and ∼8×10-7 for 13CO in the dense core, and higher H2O abundances of ∼4×10-9 in the foreground cloud and ∼7×10-7 in the outflow. Conclusions. The high H2O abundance in the warm outflow is probably due to the evaporation of water-rich icy grain mantles, while the H2O abundance is kept down by freeze-out in the dense core and by photodissociation in the foreground cloud.

KW - astrochemistry

KW - ISM: individual objects: DR21

KW - ISM: molecules

KW - stars: formation

UR - http://www.scopus.com/inward/record.url?scp=77957799846&partnerID=8YFLogxK

U2 - 10.1051/0004-6361/201014515

DO - 10.1051/0004-6361/201014515

M3 - Journal article

AN - SCOPUS:77957799846

VL - 518

JO - Astronomy & Astrophysics

JF - Astronomy & Astrophysics

SN - 0004-6361

IS - 4

M1 - L107

ER -