A New Model for Cosmic‐Ray Ion Erosion of Volatiles from Grains in the Interstellar Medium

Bringa, Eduardo M.; Johnson, R. E.

doi:10.1086/381382

Cited by 66 publications

(85 citation statements)

References 28 publications

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“…It is thus conceivable that they are older than assumed and that the absence of depletion could be due to another mechanism, such as strong desorption, an ill-understood mechanism (Roberts et al 2007). It is understood that energetic cosmic ray impacts can desorb the most volatile ices such as CO (Leger et al 1985;Hasegawa & Herbst 1993;Bringa & Johnson 2004;Roberts et al 2007). The desorption efficiency is inversely correlated with the size of the grains because smaller grains are easier to warm up.…”

Section: Discussionmentioning

confidence: 99%

L1506: a prestellar core in the making

Pagani¹,

Ristorcelli

Boudet

et al. 2010

A&A

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Context. Exploring the structure and dynamics of cold starless clouds is necessary to understand the different steps leading to the formation of protostars. Because clouds evolve slowly, many of them must be studied in detail to identify different moments in a cloud's lifetime. Aims. We study a fragment of the long filament L1506 in the Taurus region, which we name L1506C, a core with interesting dust properties observed by the PRONAOS balloon-borne telescope. Methods. To trace the mass content of L1506C and its kinematics, we mapped the dust emission, and the line emission of two key species, C 18 O and N 2 H + . We also observed 13 CO and C 17 O. We model the species emission using 1D Monte Carlo models.Results. This cloud is reminiscent of L1498 but also exhibits peculiar features: i) a large envelope emitting solely in 13 CO that contains a much smaller core with strong C 18 O depletion at its centre despite a low maximum opacity (A V ∼ 20 mag); ii) extremely narrow C 18 O lines indicating a low, non-measurable turbulence; iii) contraction traced by C 18 O itself (plus rotation); iv) unexpectedly, the kinematical signature of the external envelope is opposite to that of the core, the 13 CO and C 18 O velocity gradients having opposite directions and the C 18 O line profile being blue peaked in contrast to the 13 CO one which is red peaked. The core is large (r = 3 × 10 4 AU) and not very dense (n(H 2 ) ≤ 5 × 10 4 cm −3 , possibly less). This core is therefore not yet prestellar. Conclusions. All these properties imply that the core is kinematically detached from its envelope and in the process of forming a prestellar core. This is the first time that the dynamical formation of a prestellar core has been witnessed. The extremely low turbulence could explain the strong depletion of this core despite its relatively low density and opacity in contrast to undepleted cores such as L1521E, which exhibits a turbulence at least 4 times as high.

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Section: Discussionmentioning

confidence: 99%

L1506: a prestellar core in the making

Pagani¹,

Ristorcelli

Boudet

et al. 2010

A&A

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“…Irradiation of astrophysical ices, such as H 2 O, CO 2 , CO, and NH 3 , by heavy ions have been recently investigated either by plasma desorption mass spectrometry (Collado et al 2004;Farenzena et al 2005;Ponciano et al 2006;Martinez et al 2006) or by infrared spectroscopy (FTIR) (Seperuelo Duarte et al 2009Pilling et al 2010). This kind of data may be useful for estimating desorption rates of the interstellar grains attributed to HGCR (Bringa & Johnson 2004). In the present contribution, the column densities of CH 4 and their radiolysis products have been measured as a function of beam fluence.…”

Section: Introductionmentioning

confidence: 99%

Cosmic ray impact on astrophysical ices: laboratory studies on heavy ion irradiation of methane

Barros

Bordalo

Duarte

et al. 2011

A&A

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Laboratory data of CH 4 ice radiolysis promoted by fast heavy ions are obtained by infrared spectroscopy (FTIR). CH 4 molecules are condensed on a CsI substrate at 15 K, and the ice layer is bombarded by 220 MeV 16 O 7+ ion beam. The ice thickness is thin enough to be traversed by projectiles at constant velocity close to the equilibrium charge state. The induced CH 4 dissociation gives rise to the formation of molecular species CH 3 , C 2 H 2 , C 2 H 4 , C 2 H 6 , and C 3 H 8 . Their formation and dissociation cross sections are determined. C 2 H 6 represent the most abundant daughter molecules. The carbon budget analysis of CH 4 and its radiolysis products shows that the column density of carbon atoms contained in the methane destroyed during ion irradiation is 30−50% greater than the sum for the column densities of the newly formed species. As an astrophysical implication, the current results allow estimation of chemical reaction rates in ices covering interstellar grains.

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“…For example, a 0.1 µm olivine grain is heated to temperatures in excess of 70 K with a frequency Σf >70 = 3 × 10 −10 s −1 , compared to ≈ 10 −12 s −1 assumed previously (Bringa & Johnson 2004;Roberts et al 2007). Ice covered grains have Σf >70 around 10 −10 s −1 .…”

Section: Resultsmentioning

confidence: 95%

Temperature Spectra of Interstellar Dust Grains Heated by Cosmic Rays. I. Translucent Clouds

Kalvāns

2016

ApJS

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Heating of whole interstellar dust grains by cosmic-ray (CR) particles affects the gas-grain chemistry in molecular clouds by promoting molecule desorption, diffusion, and chemical reactions on grain surfaces. The frequency of such heating f T , s −1 , determines how often a certain temperature T CR , K, is reached for grains hit by CR particles. This study aims to provide astrochemists with comprehensive and updated dataset on the CR-induced whole-grain heating. We present calculations of f T and T CR spectra for bare olivine grains with radius a of 0.05; 0.1; 0.2 µm, and such grains covered with ice mantles of thickness 0.1a and 0.3a.Grain shape and structure effects are considered, as well as 30 CR elemental constituents with an updated energy spectrum corresponding to a translucent cloud with A V = 2 mag. Energy deposition by CRs in grain material was calculated with the srim program. We report full T CR spectra for all nine grain types and consider initial grain temperatures of 10 K and 20 K. We also provide frequencies

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A New Model for Cosmic‐Ray Ion Erosion of Volatiles from Grains in the Interstellar Medium

Cited by 66 publications

References 28 publications

L1506: a prestellar core in the making

L1506: a prestellar core in the making

Cosmic ray impact on astrophysical ices: laboratory studies on heavy ion irradiation of methane

Temperature Spectra of Interstellar Dust Grains Heated by Cosmic Rays. I. Translucent Clouds

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