Presentation is loading. Please wait.

Presentation is loading. Please wait.

Astrochemistry Panel Members: Jacqueline Keane Hideko Nomura Ted Bergin Tatsuhiko Hasegawa Karin Öberg Yi-Jehng Kuan.

Similar presentations


Presentation on theme: "Astrochemistry Panel Members: Jacqueline Keane Hideko Nomura Ted Bergin Tatsuhiko Hasegawa Karin Öberg Yi-Jehng Kuan."— Presentation transcript:

1 Astrochemistry Panel Members: Jacqueline Keane Hideko Nomura Ted Bergin Tatsuhiko Hasegawa Karin Öberg Yi-Jehng Kuan

2 COMETS Obama.blogspot A'Hearn et al (Icarus xxx); 2011 (Science xxx) Deep Impact/ EPOXI Meech et al xxx Mumma & Charnley 2011 ARAA Ootsubo et al (AKARI) & WISE mission important volatiles Constraints on Chemistry/Physics in Early Solar System, Natal Cloud ….. ?

3 …..... “Chemistry Works” …..... …..... What Chemistry Works ? ….....

4 OPR … ortho-to-para ratios Spin temperatures, infer formation temperature.... model dependent ? H 2 O & NH 3 molecules all cluster around 30 K Hama et al. 2011; T spin does not reflect temperature at which the ice condensed D/H Ratios Finally ! Herschel, ALMA, painful gnd-based observations H/D exchange in ice ? Ratajczak et al Abundances & Nitrogen & ….. Bulk compositions ? …ratios do not vary significantly over passage (?) Molecule relative to …what ? (A'Hearn et al 2012; comet forming region) HDO/H2O approaching VSMOW (?) but comets are N-poor COMETS : some issues with chemistry

5 Chemical Structure of PPDs (e.g., Dutrey+ 1997; Markwick+2002, Aikawa+ 2002, Bergin+ 2007) ESA Halley H 2 O, CO 2, CH 4, CH 3 OH, H 2 CO, NH 3, etc. ・ Depletion of CO: midplane of outer disk ・ Relatively large molecules: middle layer ・ Radicals: disk surface

6 Chemical Structure of PPDs (e.g., Dutrey+ 1997; Markwick+2002, Aikawa+ 2002, Bergin+ 2007) ESA Halley H 2 O, CO 2, CH 4, CH 3 OH, H 2 CO, NH 3, etc. How can we trace physical processes in disks using molecular lines? ・ Depletion of CO: midplane of outer disk ・ Relatively large molecules: middle layer ・ Radicals: disk surface

7 Chemical Structure of PPDs (e.g., Dutrey+ 1997; Markwick+2002, Aikawa+ 2002, Bergin+ 2007) ESA Halley H 2 O, CO 2, CH 4, CH 3 OH, H 2 CO, NH 3, etc. PDRs dense cores How can we trace physical processes in disks using molecular lines? ・ Depletion of CO: midplane of outer disk ・ Relatively large molecules: middle layer ・ Radicals: disk surface

8 FUV (e.g., White & Sandell 1995, Fuente+ 1996, …) FUV 13CO/C18O CI/CO Av PDRs Dust continuum C17O (e.g., Caselli+ 1999, Tafalla+ 2004) L1498 by IRAM center R dense cores Find useful tracer! Basic properties have been studied in PDRs, dense cores, etc… CO depletion Photochemistry

9 G. Mathews’ talk yesterday

10 Complexity vs Simplicity How predictive are chemical models? A general procedure (there are others) ➡ Use dust SED (and sometimes submm imaging) to constrain dust physical structure assuming grain size distribution (variable) and composition ➡ perform UV/Xray radiation transfer within this framework alongside gas chemistry/thermal balance ➡ predict abundances/column densities and sometimes emission ➡ large number of chemical and physical assumptions (constrained as best we can)

11 CO Ladder workshop BUT - not all species are CO!

12 Complexity vs Simplicity What does this mean ➡ complex models can betray what species trace what layers in the disk (think turbulence/ionization) -- can be confirmed with observations ➡ simple assumptions of abundance structure are reliable approach to directly match observations (ALMA surveys) - need information from models to make approximations ➡ complex models can betray what chemistry/physics is needed to even approach observational results

13 11/6/17 Whittet et al. (1985, MNRAS, 216, 45p) UKIRT M band observations in the 1980’s Lacy et al. (1984, ApJ, 276, 533) Palomar 5m Mitchell et al. (1990, ApJ, 363, 554) CFHT + FTS Interstellar gas and ice (OCN- band detection)

14 11/6/17 The OCN micron band in a YSO ISO spectrum NGC 7538 IRS 1 wavenumbers (cm-1) wavelength

15 Nature vs Nurture How much of the final disk chemistry is inherited from previous interstellar phases? (Water destruction and reformation in disks? Aikawa’s talk) Under which circumstances can such an inheritance be ignored when modeling? (ProDiMo, Chapillon’s, Bergin’s and Millar’s talks, etc) Contradictory evidence from disk and Solar system observations? (H 2 CO in disks, comet compositions) Is there any chemistry that is unique to the pre-disk stages?

16 How much is the chemistry reset during disk formation? What Class 0/1 molecular observations would help? Evidence from T Tauri stage observations? Evidence from comet abundances? [Herbst & van Dishoeck 2009]


Download ppt "Astrochemistry Panel Members: Jacqueline Keane Hideko Nomura Ted Bergin Tatsuhiko Hasegawa Karin Öberg Yi-Jehng Kuan."

Similar presentations


Ads by Google