The c2d Spitzer Spectroscopic Survey Of Ices Around Low-Mass Young Stellar Objects. II. CO2

dc.contributor.utaustinauthorEvans, Neal J.en_US
dc.creatorPontoppidan, Klaus M.en_US
dc.creatorBoogert, Adwin C. A.en_US
dc.creatorFraser, Helen J.en_US
dc.creatorvan Dishoeck, Ewine F.en_US
dc.creatorBlake, Geoffrey A.en_US
dc.creatorLahuis, Freden_US
dc.creatorOberg, Karin I.en_US
dc.creatorEvans, Neal J.en_US
dc.creatorSalyk, Coletteen_US
dc.date.accessioned2016-04-28T19:43:12Z
dc.date.available2016-04-28T19:43:12Z
dc.date.issued2008-05en
dc.description.abstractThis paper presents Spitzer IRS lambda/Delta lambda similar to 600 spectroscopy of the CO2 15.2 mu m bending mode toward 50 embedded young low-mass stars, taken mostly from the "Cores to Disks'' (c2d) Legacy program. The average abundance of solid CO2 relative to water in low-mass protostellar envelopes is 0.32 +/- 0.02, significantly higher than that found in quiescent molecular clouds and in massive star-forming regions. A decomposition of the observed CO2 bending mode profiles requires a minimum of five unique components. Roughly 2/3 of the CO2 ice is found in a water-rich environment, while most of the remaining 1/3 is found in a CO environment with strongly varying relative concentrations of CO2 to CO along each line of sight. Ground-based observations of solid CO toward a large subset of the c2d sample are used to further constrain the CO2:CO component and suggest a model in which low-density clouds form the CO2:H2O component and higher density clouds form the CO2:CO ice during and after the freezeout of gas-phase CO. The abundance of the CO2:CO component is consistent with cosmic-ray processing of the CO-rich part of the ice mantles, although a more quiescent formation mechanism is not ruled out. It is suggested that the subsequent evolution of the CO2 and CO profiles toward low-mass protostars, in particular the splitting of the CO2 bending mode due to pure, crystalline CO2, is first caused by distillation of the CO2:CO component through evaporation of CO due to thermal processing to similar to 20-30 K. The formation of pure CO2 via segregation from the H2O rich mantle may contribute to the band splitting at higher levels of thermal processing (greater than or similar to 50 K) but is harder to reconcile with the physical structure of protostellar envelopes around low-luminosity objects.en_US
dc.description.departmentAstronomyen_US
dc.description.sponsorshipTraining Network (MEST-CT-2004-50460en_US
dc.identifierdoi:10.15781/T20V5K
dc.identifier.Filename2008_05_stellarobjectsii.pdfen_US
dc.identifier.citationPontoppidan, Klaus M., A. C. A. Boogert, Helen J. Fraser, Ewine F. van Dishoeck, Geoffrey A. Blake, Fred Lahuis, Karin I. �berg, Neal J. Evans II, and Colette Salyk. "The c2d spitzer spectroscopic survey of ices around low-mass young stellar objects. II. CO2." The Astrophysical Journal, Vol. 678, No. 2 (May., 2008): 1005.en_US
dc.identifier.doi10.1086/533431en_US
dc.identifier.issn0004-637Xen_US
dc.identifier.urihttp://hdl.handle.net/2152/35167
dc.language.isoEnglishen_US
dc.relation.ispartofen_US
dc.relation.ispartofserialAstrophysical Journalen_US
dc.rightsAdministrative deposit of works to Texas ScholarWorks: This works author(s) is or was a University faculty member, student or staff member; this article is already available through open access or the publisher allows a PDF version of the article to be freely posted online. The library makes the deposit as a matter of fair use (for scholarly, educational, and research purposes), and to preserve the work and further secure public access to the works of the University.en_US
dc.rights.restrictionOpenen_US
dc.subjectastrochemistryen_US
dc.subjectcircumstellar matteren_US
dc.subjectdust, extinctionen_US
dc.subjectism : evolutionen_US
dc.subjecttime-dependent chemistryen_US
dc.subjectdense molecular cloudsen_US
dc.subjectgrainen_US
dc.subjectsurface-reactionsen_US
dc.subjectsolid carbon-dioxideen_US
dc.subjectinfrared-spectroscopyen_US
dc.subjectinterstellar-mediumen_US
dc.subjectthermal-desorptionen_US
dc.subjecthigh-resolutionen_US
dc.subjectbanden_US
dc.subjectstrengthsen_US
dc.subjectdark clouden_US
dc.subjectastronomy & astrophysicsen_US
dc.titleThe c2d Spitzer Spectroscopic Survey Of Ices Around Low-Mass Young Stellar Objects. II. CO2en_US
dc.typeArticleen_US

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