Water in Star-forming Regions with the<i>Herschel Space Observatory</i>(WISH). I. Overview of Key Program and First Results

Dishoeck, E. F. van; Kristensen, L. E.; Benz, A. O.; Bergin, Edwin A.; Caselli, P.; Cernicharo, J.; Herpin, Fabrice; Hogerheijde, M. R.; Johnstone, Doug; Liseau, R.; Nisini, B.; Shipman, R.; Tafalla, M.; Tak, F. F. S. van der; Wyrowski, F.; Aikawa, Yuri; Bachiller, R.; Baudry, A.; Benedettini, M.; Bjerkeli, P.; Blake, G. A.; Bontemps, Sylvain; Braine, J.; Brinch, Christian; Bruderer, S.; Chavarría, L.; Codella, C.; Daniel, F.; Graauw, Th. de; Deul, E.; Giorgio, A. M. Di; Dominik, C.; Doty, S. D.; Dubernet, Marie‐Lise; Encrenaz, P.; Feuchtgruber, H.; Fich, M.; Frieswijk, W.; Fuente, A.; Giannini, T.; Goicoechea, J. R.; Helmich, Frank; Herczeg, Gregory J.; Jacq, T.; Jørgensen, J. K.; Karska, A.; Kaufman, Michael J.; Keto, Eric; Larsson, Bengt; Leflóch, B.; Lis, D. C.; Marseille, M.; McCoey, C.; Melnick, Gary J.; Neufeld, David A.; Olberg, M.; Pagani, L.; Panić, Olja; Parise, B.; Pearson, John C.; Plume, R.; Risacher, C.; Salter, D. M.; Santiago-García, J.; Saraceno, P.; Stäuber, P.; Kempen, T. A. van; Visser, R.; Viti, S.; Walmsley, M.; Wampfler, S. F.; Yıldız, U. A.

doi:10.1086/658676

Cited by 212 publications

(42 citation statements)

References 173 publications

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“…The observations presented in this paper were obtained with the Heterodyne Instrument for the Far-Infrared (HIFI; de Graauw et al 2010;Roelfsema et al 2012) on board the Herschel Space Observatory (Pilbratt et al 2010) as part of the Guaranteed Time Key Project "Water in Star-forming Regions with Herschel" (WISH; van Dishoeck et al 2011) and two open-time programs (PI: M. Hogerheijde). With its FWHM beam of 18-38 at the observing frequencies, Herschel covers the entire disk of all sources.…”

Section: The Water Line Surveymentioning

confidence: 99%

“…The dust distribution determines the UV field of the disk, which strongly affects the gas temperature (Glassgold et al 2004;Woitke et al 2009) and photo-reaction (photodissociation and photodesorption) rates (Bergin et al 2003;van Dishoeck et al 2006;Bruderer et al 2009;Öberg et al 2009). Dust grains also act as a sink of gas-phase molecules, because molecules can freeze out onto the dust grains.…”

Section: Introductionmentioning

confidence: 99%

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Survey of Cold Water Lines in Protoplanetary Disks: Indications of Systematic Volatile Depletion

Bergin

Hogerheijde

et al. 2017

ApJ

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We performed very deep searches for 2 ground-state water transitions in 13 protoplanetary disks with the HIFI instrument on board the Herschel Space Observatory, with integration times up to 12 hr per line. We also searched for, with shallower integrations, two other water transitions that sample warmer gas. The detection rate is low, and the upper limits provided by the observations are generally much lower than predictions of thermo-chemical models with canonical inputs. One ground-state transition is newly detected in the stacked spectrum of AATau, DMTau, LkCa15, and MWC480. We run a grid of models to show that the abundance of gas-phase oxygen needs to be reduced by a factor of at least 100 to be consistent with the observational upper limits (and positive detections) if a dust-to-gas mass ratio of 0.01 were to be assumed. As a continuation of previous ideas, we propose that the underlying reason for the depletion of oxygen (hence the low detection rate) is the freeze-out of volatiles such as water and CO onto dust grains followed by grain growth and settling/migration, which permanently removes these gas-phase molecules from the emissive upper layers of the outer disk. Such depletion of volatiles is likely ubiquitous among different disks, though not necessarily to the same degree. The volatiles might be returned back to the gas phase in the inner disk ( 15  au), which is consistent with current constraints. Comparison with studies on disk dispersal due to photoevaporation indicates that the timescale for volatile depletion is shorter than that of photoevaporation.

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Section: The Water Line Surveymentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Survey of Cold Water Lines in Protoplanetary Disks: Indications of Systematic Volatile Depletion

Bergin

Hogerheijde

et al. 2017

ApJ

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“…Water, despite being one of the most abundant species in the molecular interstellar medium (ISM), is difficult to observe in astrophysical objects due to its prevalence in the Earth's atmosphere (see van Dishoeck et al 2013 for a comprehensive review of astronomical water observations). Ground-based observations of H 2 O have primarily targeted maser emission, most frequently the…”

Section: Introductionmentioning

confidence: 99%

“…More recently, the study of low-lying rotational levels at high spectral resolution (∼0.5 km s −1 ) has been facilitated by the Heterodyne Instrument for the Far-Infrared (HIFI; de Graauw et al 2010) on board the Herschel Space Observatory (Pilbratt et al 2010). Water has been detected in both emission and absorption out of levels with  E 200 K in several protostars (e.g., van Dishoeck et al 2011;van der Tak et al 2013), and in absorption out of the 0 0,0 and 1 0,1 levels in the molecular ISM (e.g., Sonnentrucker et al 2010;Flagey et al 2013). Observations that resolve the velocity structure of absorption lines are vital to both determining level-specific column densities and understanding the dynamics of the absorbing/emitting regions.…”

mentioning

confidence: 99%

Sofia/Exes Observations of Water Absorption in the Protostar Afgl 2591 at High Spectral Resolution

Indriolo

Neufeld

DeWitt

et al. 2015

ApJ

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We present high spectral resolution (∼3 km s −1 ) observations of the n 2 ro-vibrational band of H 2 O in the 6.086-6.135 μm range toward the massive protostar AFGL 2591 using the Echelon-Cross-Echelle Spectrograph (EXES) on the Stratospheric Observatory for Infrared Astronomy (SOFIA). Ten absorption features are detected in total, with seven caused by transitions in the n 2 band of H 2 O, two by transitions in the first vibrationally excited n 2 band of H 2 O, and one by a transition in the n 2 band of H 2 18 O. Among the detected transitions is the n 2 1 1,1 -0 0,0 line that probes the lowest-lying rotational level of para-H 2 O. The stronger transitions appear to be optically thick, but reach maximum absorption at a depth of about 25%, suggesting that the background source is only partially covered by the absorbing gas or that the absorption arises within the 6 μm emitting photosphere. Assuming a covering fraction of 25%, the H 2 O column density and rotational temperature that best fit the observed absorption

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“…Three separate water formation mechanisms have been posited to date (e.g., Hollenbach et al 2009Hollenbach et al , 2012, and references therein). Many details about water in the ISM can be found in van Dishoeck et al (2011) in their presentation of the early results of the Herschel WISH key program, mainly dedicated to the study of water in star-forming regions and protostars. First, water can be produced by means of a gas-phase ion-neutral chemistry that is driven by cosmic ray ionization.…”

Section: Introductionmentioning

confidence: 99%

WATER ABSORPTION IN GALACTIC TRANSLUCENT CLOUDS: CONDITIONS AND HISTORY OF THE GAS DERIVED FROMHERSCHEL/HIFI PRISMAS OBSERVATIONS

Flagey¹,

Goldsmith²,

Lis³

et al. 2012

ApJ

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100

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ABSTRACT2 O for the lower energy level of each transition observed. The total column density of water in translucent clouds is usually about a few 10 13 cm −2 . We find that the abundance of water relative to hydrogen nuclei is 1 × 10 −8 in agreement with models for oxygen chemistry in which high cosmic ray ionization rates are assumed. Relative to molecular hydrogen, the abundance of water is remarkably constant through the Galactic plane with X(H 2 O) = 5 × 10 −8 , which makes water a good traced of H 2 in translucent clouds. Observations of the excited transitions of H 2 O enable us to constrain the abundance of water in excited levels to be at most 15%, implying that the excitation temperature, T ex , in the ground state transitions is below 10 K. Further analysis of the column densities derived from the two ortho ground state transitions indicates that T ex 5 K and that the density n(H 2 ) in the translucent clouds is below 10 4 cm −3 . We derive the water ortho-to-para ratio for each absorption feature along the line of sight and find that most of the clouds show ratios consistent with the value of 3 expected in thermodynamic equilibrium in the high-temperature limit. However, two clouds with large column densities exhibit a ratio that is significantly below 3. This may argue that the history of water molecules includes a cold phase, either when the molecules were formed on cold grains in the well-shielded, low-temperature regions of the clouds, or when they later become at least partially thermalized with the cold gas (∼25 K) in those regions; evidently, they have not yet fully thermalized with the warmer (∼50 K) translucent portions of the clouds.

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Water in Star-forming Regions with theHerschel Space Observatory(WISH). I. Overview of Key Program and First Results

Cited by 212 publications

References 173 publications

Survey of Cold Water Lines in Protoplanetary Disks: Indications of Systematic Volatile Depletion

Survey of Cold Water Lines in Protoplanetary Disks: Indications of Systematic Volatile Depletion

Sofia/Exes Observations of Water Absorption in the Protostar Afgl 2591 at High Spectral Resolution

WATER ABSORPTION IN GALACTIC TRANSLUCENT CLOUDS: CONDITIONS AND HISTORY OF THE GAS DERIVED FROMHERSCHEL/HIFI PRISMAS OBSERVATIONS

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