A COLD COMPLEX CHEMISTRY TOWARD THE LOW-MASS PROTOSTAR B1-b: EVIDENCE FOR COMPLEX MOLECULE PRODUCTION IN ICES

Journal Article · Thu Jun 10 00:00:00 EDT 2010 · Astrophysical Journal

DOI:https://doi.org/10.1088/0004-637X/716/1/825· OSTI ID:21451113

Oeberg, Karin I ^[1]; Bottinelli, Sandrine ^[2]; Joergensen, Jes K ^[3]; Van Dishoeck, Ewine F ^[4]

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1. Harvard-Smithsonian Center for Astrophysics, MS 42, 60 Garden Street, Cambridge, MA 02138 (United States)
2. Centre d'Etude Spatiale des Rayonnements, 9 avenue du Colonel Roche, BP 4346, 31028 Toulouse Cedex 4 (France)
3. Centre for Star and Planet Formation, Natural History Museum of Denmark, University of Copenhagen, Oester Voldgade 5-7, 1350 Copenhagen K. (Denmark)
4. Leiden Observatory, Leiden Sterrewacht, P.O. Box 9513, 2300 RA Leiden (Netherlands)

Gas-phase complex organic molecules have been detected toward a range of high- and low-mass star-forming regions at abundances which cannot be explained by any known gas-phase chemistry. Recent laboratory experiments show that UV irradiation of CH{sub 3}OH-rich ices may be an important mechanism for producing complex molecules and releasing them into the gas phase. To test this ice formation scenario, we mapped the B1-b dust core and nearby protostar in CH{sub 3}OH gas using the IRAM 30 m telescope to identify locations of efficient non-thermal ice desorption. We find three CH{sub 3}OH abundance peaks tracing two outflows and a quiescent region on the side of the core facing the protostar. The CH{sub 3}OH gas has a rotational temperature of {approx}10 K at all locations. The quiescent CH{sub 3}OH abundance peak and one outflow position were searched for complex molecules. Narrow, 0.6-0.8 km s{sup -1} wide, HCOOCH{sub 3} and CH{sub 3}CHO lines originating in cold gas are clearly detected, CH{sub 3}OCH{sub 3} is tentatively detected, and C{sub 2}H{sub 5}OH and HOCH{sub 2}CHO are undetected toward the quiescent core, while no complex molecular lines were found toward the outflow. The core abundances with respect to CH{sub 3}OH are {approx}2.3% and 1.1% for HCOOCH{sub 3} and CH{sub 3}CHO, respectively, and the upper limits are 0.7%-1.1%, which is similar to most other low-mass sources. The observed complex molecule characteristics toward B1-b and the pre-dominance of HCO-bearing species suggests a cold ice (below 25 K, the sublimation temperature of CO) formation pathway followed by non-thermal desorption through, e.g., UV photons traveling through outflow cavities. The observed complex gas composition together with the lack of any evidence of warm gas-phase chemistry provides clear evidence of efficient complex molecule formation in cold interstellar ices.

• OSTI ID: 21451113
• Journal Information: Astrophysical Journal, Vol. 716, Issue 1; Other Information: DOI: 10.1088/0004-637X/716/1/825; ISSN 0004-637X
• Country of Publication: United States
• Language: English

Related Subjects

79 ASTROPHYSICS
COSMOLOGY AND ASTRONOMY
ABUNDANCE
CARBON MONOXIDE
DESORPTION
ICE
METHANOL
PHOTONS
STARS
SUBLIMATION
TELESCOPES
ALCOHOLS
BOSONS
CARBON COMPOUNDS
CARBON OXIDES
CHALCOGENIDES
ELEMENTARY PARTICLES
EVAPORATION
HYDROXY COMPOUNDS
MASSLESS PARTICLES
ORGANIC COMPOUNDS
OXIDES
OXYGEN COMPOUNDS
PHASE TRANSFORMATIONS
SORPTION