Bérengère Parise Testing grain surface chemistry models using deuterated probes in low-mass star-forming regions. Bonn, Germany

Bérengère Parise - Max Planck Institut für Radioastronomie 2 Introduction For 30 years, observations in the ISM have shown fractionations XD/XH  [D]/[H] (~ ) D 2 CO/H 2 CO ~ 0.05 towards the low-mass protostar IRAS16293 (Ceccarelli et al. 1998, A&A 338, L43) (figure : M.R. Hogerheijde in van Dishoeck & Blake 1998) D 2 CO/H 2 CO ~ in Orion (Turner, 1990, ApJ 362, L29)  Active grain chemistry

Bérengère Parise - Max Planck Institut für Radioastronomie 3 Chemical processes Gas phase reactions ? Grain surface reactions ? (e.g. Roberts & Millar 2000, A&A 361, 398) (e.g. Tielens 1983, A&A 119, 177) Desorption Prestellar core phase Envelope heated by the protostar

Bérengère Parise - Max Planck Institut für Radioastronomie 4 Tielens & Hagen, 1982, A&A 114, 245 Tielens, 1983, A&A 119, 177 Fractionation due to : enhanced atomic D/H ratio in the gas phase (D formed from H 2 D + )  requires CO depletion and low temperature lower activation barriers for reactions involving D CO H 2 CO Roberts & Millar 2000, A&A 361, 398 Roberts & Millar 2000, A&A 364, 780 H HD  H 2 D + + H 2 root reaction : H 2 D + propagates the deuterium to other molecules Adsorption in grain mantles Required physical conditions low temperature CO depletion Gas phase versus grain chemistry

Bérengère Parise - Max Planck Institut für Radioastronomie 5 Charnley et al. 1997, AJ 482, L203 A test for surface chemistry ?

Bérengère Parise - Max Planck Institut für Radioastronomie 6 Deuterated methanol in IRAS16293 Parise et al. 2002, A&A 393, L49 Parise et al. 2004, A&A, 416, 159 IRAM 30m observations 23 CH 2 DOH lines 6 CH 3 OD lines 15 CHD 2 OH lines 12 CD 3 OH lines

Bérengère Parise - Max Planck Institut für Radioastronomie f(CH 2 DOH) = 37 % f(CH 3 OD) = 1.8 % f(CHD 2 OH) = 7.4 % f(CD 3 OH) = 1.0 % -0.6 IRAS Population diagrams

Bérengère Parise - Max Planck Institut für Radioastronomie 8 requires an atomic D/H ratio ~ in the gas phase. This atomic fractionation is now reproduced by new generation models including D 2 H + and D 3 + (e.g. Roberts et al. 2003) See poster by Vastel et al. CH 2 DOH/CH 3 OD very high compared with the statistical ratio 3 CH 3 OD destroyed in the gas phase by protonation ? CH 3 ODH +  CH 3 OH + D + e - CH 3 OD + H + e - confirmed by Osamura et al dashed lines : surface chemistry model Stantcheva et al. 2003, MNRAS 340, 983 red : IRAS observations Comparison to grain chemistry models

Bérengère Parise - Max Planck Institut für Radioastronomie 9 challenged by Dartois et al. (on the edge of one SWS detector) VLT observation on W33A : HDO / H 2 O < (Dartois et al. 2003, A&A 399, 1009) Inconclusive mostly because high-mass protostars show a lower degree of deuteration than low-mass protostars ? Grain surface model predictions : HDO / H 2 O ~ 20 % What about looking directly on the grains ? Observations in solid phase are less sensitive than gas phase observations. H 2 O : main constituent of icy mantles around dust grains. Search for HDO in the ices Previous attempts : Detection of HDO in high mass protostars W33A et NGC7538 IRS9 (Teixeira et al., 1999, A&A, L19-L22)

Bérengère Parise - Max Planck Institut für Radioastronomie 10 Recherche de HDO en phase solide sur les grains Observation of OD and OH stretch bands (in absorption) at 4.1 and 3  m with SpeX on IRTF (Mauna Kea) R = 1500 CH 3 D:O 2 -1:1 ice before and after UV irradiation (Dartois et al 2000) Search for solid HDO in low-mass protostars grain mantles

Bérengère Parise - Max Planck Institut für Radioastronomie 11 Parise et al. 2003, A&A 410, class I protostars bright in NIR high J-K extinction D 2 CO/H 2 CO ~ 5% Solid phase HDO/H 2 O (1)

Bérengère Parise - Max Planck Institut für Radioastronomie 12 Solid phase HDO/H 2 O (2) HDO/H 2 O ≤ ~ 1% Does this exclude grain surface chemistry for deuteration ? Or has water a different fractionation than methanol ?

Bérengère Parise - Max Planck Institut für Radioastronomie 13 Deuterated water in the gas phase IRAS Observations JCMT IRAM Frequency (GHz) E up (K) JCMT and IRAM observations ON-source & outflow 5 lines detected on-source no emission detected towards the outflow.

Bérengère Parise - Max Planck Institut für Radioastronomie 14 Deuterated water in IRAS Modelling T ev = 100 K R x in x out inner envelope : HDO/H 2 O = 3% outer envelope : HDO/H 2 O < 0.2 % Model of envelope emission from Ceccarelli, Hollenbach & Tielens 1996: density structure : inside-out collapse (Shu scenario). gas temperature computed self-consistently : cooling depends on CO, O and H 2 O abundance. Adapted to HDO study : collision coefficients from Green (1989) use of the density and temperature profiles as well as water abundance derived by Ceccarelli et al. (2000). HDO abundance : Parise et al. 2005, A&A 431, 547

Bérengère Parise - Max Planck Institut für Radioastronomie 15 Deuterated methanol observations : IRAS CH 2 DOH/CH 3 OH = 37 % CH 3 OD/CH 3 OH = 1.8 % CHD 2 OH/CH 3 OH = 7.4 % CD 3 OH/CH 3 OH = 1.0 % Consistent with grain chemistry models, but :  these models require a high atomic D/H ratio in the gas phase, which can only occur when CO is heavily depleted.  these models predict HDO/H 2 O ~ 20 % HDO observation in grain mantles : NGC1333 SVS12, SVS13, L1489 IRS, TMR1 HDO/H 2 O ≤ 1 %... HDO observation in the gas phase : IRAS HDO/H 2 O = 3% in the inner enveloppe HDO/H 2 O < 0.2 % in the outer enveloppe. Questions raised by single dish observations

Bérengère Parise - Max Planck Institut für Radioastronomie 16 Conclusions Modelling of the single-dish HDO emission points to a fractionation enhancement of water in the inner warm envelope (“hot corino”). Same for methanol ? Unfortunately such a modelling cannot be performed for CH 2 DOH because collision coefficients are not available. Moreover interferometric observations have shown that IRAS16293 is a binary with different chemical properties (PdBI, Bottinelli et al. 2004; SMA, Kuan et al. 2004, see poster by Huang et al). Accurate comparison to grain surface models can therefore only be done after observing the spatial distribution of deuterated methanol.

Special thanks to the organizers of this conference. Thanks to my collaborators : Cecilia Ceccarelli - Emmanuel Caux Eric Herbst - A.G.G.M. Tielens Alain Castets - Bertrand Lefloch And all the WAGOS group Ted Simon - John Rayner Indra Mukhopadhyay Emmanuel Dartois - Laurent Loinard Peter Schilke - Karl Menten Operations at IRAM are funded by the CNRS (Centre National de la Recherche Scientifique, France), the MPG (Max Planck Gesellschaft, Germany), and the IGN (Instituto Geografico Nacional, Spain). The Infrared Telescope Facility is operated by the University of Hawaii under Cooperative Agreement no. NCC with the National Aeronautics and Space Administration, Office of Space Science, Planetary Astronomy Program. The James Clerk Maxwell Telescope (JCMT) is operated by the Joint Astronomy Centre on behalf of the UK Particle Physics and Astronomy Research Council (PPARC), the National Research Council of Canada and the Netherlands Organisation for Pure Research. No animal was hurt during the preparation of this talk