SIMBAD references

2011ApJ...740..109O - Astrophys. J., 740, 109 (2011/October-3)

The Spitzer ice legacy: ice evolution from cores to protostars.

OBERG K.I., BOOGERT A.C.A., PONTOPPIDAN K.M., VAN DEN BROEK S., VAN DISHOECK E.F., BOTTINELLI S., BLAKE G.A. and EVANS N.J.

Abstract (from CDS):

Ices regulate much of the chemistry during star formation and account for up to 80% of the available oxygen and carbon. In this paper, we use the Spitzer c2d Legacy ice survey, complimented with data sets on ices in cloud cores and high-mass protostars, to determine standard ice abundances and to present a coherent picture of the evolution of ices during low- and high-mass star formation. The median ice composition H2O:CO:CO2:CH3OH:NH3:CH4:XCN is 100:29:29:3:5:5:0.3 and 100:13:13:4:5:2:0.6 toward low- and high-mass protostars, respectively, and 100:31:38:4:-:-:- in cloud cores. In the low-mass sample, the ice abundances with respect to H2 O of CH4, NH3, and the component of CO2 mixed with H2O typically vary by <25%, indicative of co-formation with H2O. In contrast, some CO and CO2 ice components, XCN, and CH3 OH vary by factors 2-10 between the lower and upper quartile. The XCN band correlates with CO, consistent with its OCN identification. The origin(s) of the different levels of ice abundance variations are constrained by comparing ice inventories toward different types of protostars and background stars, through ice mapping, analysis of cloud-to-cloud variations, and ice (anti-)correlations. Based on the analysis, the first ice formation phase is driven by hydrogenation of atoms, which results in an H2O-dominated ice. At later prestellar times, CO freezes out and variations in CO freezeout levels and the subsequent CO-based chemistry can explain most of the observed ice abundance variations. The last important ice evolution stage is thermal and UV processing around protostars, resulting in CO desorption, ice segregation, and the formation of complex organic molecules. The distribution of cometary ice abundances is consistent with the idea that most cometary ices have a protostellar origin.

Abstract Copyright:

Journal keyword(s): astrochemistry - circumstellar matter - infrared: ISM - ISM: abundances - ISM: lines and bands - ISM: molecules - molecular processes - stars: formation

Simbad objects: 26

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