Interstellar Ices2 Ice Inventory Protostellar Environments Energetic Processing

  • Slides: 25
Download presentation
Interstellar Ices-2 Ice Inventory Protostellar Environments Energetic Processing? Laboratory Simulations New Spitzer Satellite Results

Interstellar Ices-2 Ice Inventory Protostellar Environments Energetic Processing? Laboratory Simulations New Spitzer Satellite Results Adwin Boogert California Inst. of Technology Jan/2005 Interstellar Ices-I 1

Contents –what else is present in interstellar ices, besides H 2 O and CO?

Contents –what else is present in interstellar ices, besides H 2 O and CO? –basic chemistry: Are new molecules formed through energetic processes? –complexity in the 5 -10 m region –Ice inventory. Where is NH 3? –energetic processing diffuse/dense ISM? –Ions in the ices? –Complex CH 3 OH/CO 2/CO/H 2 O mixtures Jan/2005 Interstellar Ices-I 2

5 A Grain in Space More realistic: Jan/2005 Interstellar Ices-I 3

5 A Grain in Space More realistic: Jan/2005 Interstellar Ices-I 3

Laboratory Simulations 5 Chemical processes occurring in space can be simulated in laboratory at

Laboratory Simulations 5 Chemical processes occurring in space can be simulated in laboratory at low T (>=10 K) and low pressure. ●Thin films of ice condensed on a surface and absorption or reflection spectrum taken. ●Temperature and irradiation by UV light or energetic particles of ice sample can be controlled. ●Astrophysical laboratories: Leiden, Catania, NASA Ames/Goddard, Paris ● Gerakines et al. A&A 357, 793 (2000) Jan/2005 Interstellar Ices-I 4

Spitzer Spectroscopy of Ices toward Protostars 5 /SVS 4 -5 Jan/2005 Interstellar Ices-I 5

Spitzer Spectroscopy of Ices toward Protostars 5 /SVS 4 -5 Jan/2005 Interstellar Ices-I 5

Ice Inventory Jan/2005 Interstellar Ices-I 6 6

Ice Inventory Jan/2005 Interstellar Ices-I 6 6

Ice Inventory Jan/2005 Interstellar Ices-I 6 7

Ice Inventory Jan/2005 Interstellar Ices-I 6 7

6 Ice Inventory [H 2 O and silicate subtracted!] Jan/2005 Interstellar Ices-I 8

6 Ice Inventory [H 2 O and silicate subtracted!] Jan/2005 Interstellar Ices-I 8

6 Ice Inventory [H 2 O and silicate subtracted!] Jan/2005 Interstellar Ices-I 9

6 Ice Inventory [H 2 O and silicate subtracted!] Jan/2005 Interstellar Ices-I 9

6 Ice Inventory NH 3/CH 3 OH=4 (SVS 4 -5) NH 3/CH 3 OH<0.

6 Ice Inventory NH 3/CH 3 OH=4 (SVS 4 -5) NH 3/CH 3 OH<0. 5 Jan/2005 Interstellar Ices-I 10

6 Ice Inventory 'Typical' abundances w. r. t. H 2 O ice CO CO

6 Ice Inventory 'Typical' abundances w. r. t. H 2 O ice CO CO 2 CH 4 CH 3 OH HCOOH [NH 3] H 2 CO [HCOO-] OCS [SO 2] [NH 4+] [OCN-] Jan/2005 few-50% 15 -35% 2 -4% <8, 30% 3 -8% <10, 40% (? ) <2, 7% 0. 3% <0. 05, 0. 2% <=3% 3 -12% <0. 2, 7% Interstellar Ices-I Factors of 2 abundance variations between sight -lines are common! Note uncertain NH 3 abundance. Will Spitzer spectra finally establish presence of NH 3 in interstellar ices? 11

Evidence for Energetic Processing? 7 UV/CR processing simple ices in laboratory produces organic residues

Evidence for Energetic Processing? 7 UV/CR processing simple ices in laboratory produces organic residues ('yellow' stuff). Problem: no such complex stuff observed in icy sightlines. Much explained by grain surface chemistry and thermal processing of simple ices. Selection effect? Greenberg et al. Ap. J 455, L 177 (1995): launched Low infrared sensitivity? processed ice sample in earth orbit exposing Better observe sublimated directly to solar radiation (EUREKA experiment). species (more sensitive)-see Yellow stuff turned brown: highly carbonaceous lecture Cecilia. residue, also including PAH. ● ● ● Jan/2005 Interstellar Ices-I 12

Evidence for Energetic Processing? Pendleton et al. 1994, Adamson et al. 1998, Chiar et

Evidence for Energetic Processing? Pendleton et al. 1994, Adamson et al. 1998, Chiar et al. 2000 Jan/2005 Interstellar Ices-I 7 3. 4 um absorption feature observed in diffuse ISM (e. g. Galactic Center). Triple peaks due to hydrocarbons (-CH, -CH 2, -CH 3). Little evidence production by UV/CR bombardment of ices: *formed in evolved star envelopes, and injected in ISM *band not polarized as opposed to silicates/ices: not in processed mantle but separate grains 13 *3. 4 um band observed in

Low Mass versus High Mass Protostar 7 Protostellar luminosity unimportant factor in ice formation

Low Mass versus High Mass Protostar 7 Protostellar luminosity unimportant factor in ice formation and processing Noriega-Crespo et al. Ap. JS 154, 352 (2004) Jan/2005 Interstellar Ices-I 14

Identification: the 6. 85 mm band 7 Major solid state band not firmly identified

Identification: the 6. 85 mm band 7 Major solid state band not firmly identified yet. Observational constraint: band shifts to red for warmer lines of sight + Condition fulfilled by NH 4 [Schutte & Khanna A&A 398, 1049, 2003]. Corresponding 3. 25 and 3. 47 m bands + would require NH as well NH 4 3 as thermal- or photo-processing to be continued. . . Jan/2005 Interstellar Ices-I 15

7 Ions in Ices H 2 O: CO 2: NH 3: O 2 at

7 Ions in Ices H 2 O: CO 2: NH 3: O 2 at different T and mixing ratios –NH 4+ roughly has spectral characteristics that fit interstellar 6. 85 m band. –NH 4+ easily produced by warming acid/base mixture NH 3+HNCO produces OCN-, which has observed feature at 4. 62 m and might account for charge balance; further study needed. –also H 2 O: N 2: CH 4 after irradiation: –In Jan/2005 fact, 4. 62 um band attributed to CN-bearing species ('XCN') last 15 years and always considered strongest evidence energetic UV/CR processing. Now less likely. Interstellar Ices-I 16

Complex CO 2/CH 3 OH/H 2 O/CO Ice Mixtures 8 H 2 O: CO

Complex CO 2/CH 3 OH/H 2 O/CO Ice Mixtures 8 H 2 O: CO 2: CH 3 OH at different CH 3 OH concentrations. Note CO 2: CH 3 OH complexes. Jan/2005 Interstellar Ices-I 17

Complex CO 2/CH 3 OH/H 2 O/CO Ice Mixtures 8 Weak wing in 2

Complex CO 2/CH 3 OH/H 2 O/CO Ice Mixtures 8 Weak wing in 2 Spitzer sources consistent with low CH 3 OH abundance derived from other features Overall width due to H 2 O: CO 2 Bottom of profile indicates apolar CO/CO 2 component [Boogert et al. Ap. JS 154, 359 (2004)] Jan/2005 Interstellar Ices-I 18

8 Complex CO 2/CH 3 OH/H 2 O/CO Ice Mixtures H 2 O: CO

8 Complex CO 2/CH 3 OH/H 2 O/CO Ice Mixtures H 2 O: CO 2: CH 3 OH=1: 1: 1 heated. Double peak characteristic for pure CO 2 appears after H 2 O crystallization. Jan/2005 Interstellar Ices-I 19

8 Evolution of Ices as Function of Protostellar Stage No obvious evolution of ice

8 Evolution of Ices as Function of Protostellar Stage No obvious evolution of ice abundances [other than evaporation of volatiles] Effects of heating commonly observed: CO ice band, 6. 8 m band, CO 2 ice band Jan/2005 Interstellar Ices-I 20

Ice Processing Massive YSOs Solid 13 CO 2: Evidence envelope heating: • • Jan/2005

Ice Processing Massive YSOs Solid 13 CO 2: Evidence envelope heating: • • Jan/2005 8 CO 2 crystallization (Boogert et al. 2000; Gerakines et al. 1999) H 2 O crystallization (Smith et al. 1989) gas/solid ratio increases (van Dishoeck et al. 1997) Detailed modelling gas phase mmwave observations (van der Tak et al. 2000) Interstellar Ices-I 21

8 Ice Processing Massive YSOs Solid 13 CO 2: Evidence envelope heating: • •

8 Ice Processing Massive YSOs Solid 13 CO 2: Evidence envelope heating: • • Jan/2005 CO 2 crystallization (Boogert et al. 2000; Gerakines et al. 1999) H 2 O crystallization (Smith et al. 1989) gas/solid ratio increases (van Dishoeck et al. 1997) Detailed modelling gas phase mmwave observations (van der Tak et al. 2000) Interstellar Ices-I 22

8 Evolution of Ices: Conclusions Ice composition evolution with protostellar phase? No (tentatively), but

8 Evolution of Ices: Conclusions Ice composition evolution with protostellar phase? No (tentatively), but evaporation of volatiles occurs. What causes composition variations between lines of sight? Ice temperature evolution in low mass protostars? Yes. Profiles 6. 8 um and 15 um CO 2 band, apolar CO evaporation, H 2 O crystallization. Also in disks. Ice composition influenced by protostellar mass/luminosity? No observational evidence, except possibly CO 2: new CO/CO 2 ice phase larger CO 2 ice abundance NH 3: surprisingly large variations between sightlines (tentative) Jan/2005 Interstellar Ices-I 23

ISO/SWS+LWS 2 -200 m spectrum Elias 29 ( Oph) with flared face-on disk model

ISO/SWS+LWS 2 -200 m spectrum Elias 29 ( Oph) with flared face-on disk model (Boogert et al. 2002, Ap. J 570, 708). Jan/2005 Interstellar Ices-I 24

Ices in Low Mass YSOs • • Jan/2005 Ices abundant toward Elias 29: most

Ices in Low Mass YSOs • • Jan/2005 Ices abundant toward Elias 29: most luminous (30 Lsun) low mass (1 -2 Msun) protostar in �Oph cloud [Before drawing conclusions on ice processing, one needs to locate ices along line of sight] Interstellar Ices-I 25