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Linking low- to high-mass YSOs with Herschel-HIFI observations of water

Authors :
Jose-Garcia, I. San
Mottram, J. C.
van Dishoeck, E. F.
Kristensen, L. E.
van der Tak, F. F. S.
Braine, J.
Herpin, F.
Johnstone, D.
van Kempen, T. A.
Wyrowski, F.
Leiden Observatory [Leiden]
Universiteit Leiden [Leiden]
Max-Planck-Institut für Extraterrestrische Physik (MPE)
Danish Meat Research Institute (DMRI)
SRON Netherlands Institute for Space Research (SRON)
FORMATION STELLAIRE 2016
Laboratoire d'Astrophysique de Bordeaux [Pessac] (LAB)
Université de Bordeaux (UB)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université de Bordeaux (UB)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)
Natl Res Council Canada, Herzberg Inst Astrophys, Victoria, BC V9E 2E7 Canada
Natl Res Council Canada, Herzberg Inst Astrophys, Victoria
foreign laboratories (FL)
CERN [Genève]
Source :
Astronomy and Astrophysics-A&A, Astronomy and Astrophysics-A&A, EDP Sciences, 2016, 585, pp.id.A103. ⟨10.1051/0004-6361/201525708⟩
Publication Year :
2016
Publisher :
EDP Sciences, 2016.

Abstract

Water probes the dynamics in young stellar objects (YSOs) effectively, especially shocks in molecular outflows. It is a key molecule for exploring whether the physical properties of low-mass protostars can be extrapolated to massive YSOs. As part of the WISH key programme, we investigate the dynamics and the excitation conditions of shocks along the outflow cavity wall as function of source luminosity. Velocity-resolved Herschel-HIFI spectra of the H2O 988, 752, 1097 GHz and 12CO J=10-9, 16-15 lines were analysed for 52 YSOs with bolometric luminosities (L_bol) ranging from 10^5 L_sun. The profiles of the H2O lines are similar, indicating that they probe the same gas. We see two main Gaussian emission components in all YSOs: a broad component associated with non-dissociative shocks in the outflow cavity wall (cavity shocks) and a narrow component associated with quiescent envelope material. More than 60% of the total integrated intensity of the H2O lines (L_H2O) comes from the cavity shock component. The H2O line widths are similar for all YSOs, whereas those of 12CO 10-9 increase slightly with L_bol. The excitation analysis of the cavity shock component, performed with the non-LTE radiative transfer code RADEX, shows stronger 752 GHz emission for high-mass YSOs, likely due to pumping by an infrared radiation field. As previously found for CO, a strong correlation with slope unity is measured between log(L_H2O) and log(L_bol), which can be extrapolated to extragalactic sources. We conclude that the broad component of H2O and high-J CO lines originate in shocks in the outflow cavity walls for all YSOs, whereas lower-J CO transitions mostly trace entrained outflow gas. The higher UV field and turbulent motions in high-mass objects compared to their low-mass counterparts may explain the slightly different kinematical properties of 12CO 10-9 and H2O lines from low- to high-mass YSOs.<br />Abridged abstract, 31 pages, 18 figures, 12 tables, accepted in Astronomy & Astrophysics

Details

Language :
English
ISSN :
00046361
Database :
OpenAIRE
Journal :
Astronomy and Astrophysics-A&A, Astronomy and Astrophysics-A&A, EDP Sciences, 2016, 585, pp.id.A103. ⟨10.1051/0004-6361/201525708⟩
Accession number :
edsair.doi.dedup.....25b67051ebb03822621225f9f17dbd29
Full Text :
https://doi.org/10.1051/0004-6361/201525708⟩