ASTROCHEMISTRY IN THE SUBMM DOMAIN

Bérengère Parise

With kind inputs from my MPIfR colleagues:

A. Belloche, S. Leurini, P. Schilke, S. Thorwirth, F. van der Tak

APEX, opening the way for ALMA Paris, February 3rd, 2006

APEX, opening the way for ALMA - Paris, Feb 3rd 2006 2

Visible

Ultraviolet electronic transitions

Infrared

Submillimetre

Millimetre

Radio

vibrational transitions

rotational transitions

Molecu

lar emission

Submm : ground rotational transitions of light molecules and excited rotational transitions of heavier molecules.

The lighter the molecule, the higher the frequencies.T

he

elec

trom

agn

etic

sp

e ctr

um

What does submillimetre bring to astrochemistry ?

Astrochemistry : study of the synthesis of molecules in space and their use in determining the properties of interstellar medium.

APEX, opening the way for ALMA - Paris, Feb 3rd 2006 3

Submm : which molecules ? which environments ?

Ground transitions of light molecules --> probe mostly cold regions

Higher excitation lines of heavier molecules --> probe warmer and/or denser regions

Spectral surveys an insight into molecular complexity comparing the chemical properties of different sources

H2D+, HD2+ essential for deuterium chemistry

HDO probe water content from the ground

H3O+ CR ionization rate

CF+ PDR tracer

CO, SiO outflows

APEX, opening the way for ALMA - Paris, Feb 3rd 2006 4

Deuterium chemistry : H2D+ and D2H+

H3+ + HD --> H2D+ + H2

Reverse reaction slightly endothermic :at low T, H2D+/H3

+ » HD/H2 ~ 10-5

H2D+ : ortho state (372 GHz) --> APEX2a receiver para state (1370 GHz)D2H+ : ortho state (1477 GHz) para state (692 GHz) --> CHAMP+

main reservoir of D in molecular clouds

Ions responsible for the transfer of deuterium in molecules

Their ground transitions lie in the submillimetre regime :

In some cold and depleted environments, they can be among the most abundant ions : - depleted prestellar cores (Caselli et al. 2003, Walmsley et al. 2004: tracer of kinematics, Vastel et al. 2004) - midplane of disks (Ceccarelli et al. 2004: tracer of ionization degree)

CONDOR receiver

APEX, opening the way for ALMA - Paris, Feb 3rd 2006 5

Deuterium chemistry : H2D+, N2D+, DCO+

Belloche et al., in prep

APEX observations towards the southern prestellar condensation Cha-MMS1

Tsys is two to three times better than at JCMT/CSO

APEX, opening the way for ALMA - Paris, Feb 3rd 2006 6

HDO : tracing water from the ground

Water can only be observed from space.

Observation of HDO : - probe the water content of astronomical sources from the ground (better spatial resolution than satellites).   -  link between material in protostellar envelopes, disks, comets, oceans ...

En

ergy

(cm

-1)

APEX will allow observation of the two ground transitions of HDO : 464 GHz, FLASH receiver 893 GHz, CHAMP+ receiver

IRAM 30mIRAM 30mHSO/HIFIHSO/HIFI

APEX/FLASHAPEX/FLASHAPEX/CHAMP+APEX/CHAMP+

HDO

APEX, opening the way for ALMA - Paris, Feb 3rd 2006 7

H3O+ : constraining CR ionization rate

van der Tak et al. in prep

H3O+ (3-2) @ 364GHz

H2O @ 183GHz

Sgr B2

Cernicharo et al. ApJ in press

APEX observations

H3O+/H2O + chemical model --> ionization rateCan further be compared to HCO+/CO diagnostic

APEX, opening the way for ALMA - Paris, Feb 3rd 2006 8

CF+ first detection : a PDR tracer

Theoretical studies (Neufeld, Wolfire & Schilke 2005) have shown: - HF main reservoir of F - HF is abundant even close to UV irradiated cloud surfaces where C+ is the dominant reservoir of C - HF + C+ --> CF+ + H

Gas abundances in a one-sided PDR with nH = 102 cm-3 and UV

= 1Neufeld et al. A&A 2006 in press

Observations towards the Orion Bar

APEX, opening the way for ALMA - Paris, Feb 3rd 2006 9

High energy lines of CO : outflows

Excitation computation becomes possible with observations of high energy CO lines --> physical parameters : n, T

Leurini et al. in prep

APEX observations NGC6334I high-velocity outflow

APEX, opening the way for ALMA - Paris, Feb 3rd 2006 10

Unbiased spectral surveys

NGC6334I @460 and 818GHz NGC6334I (black) and G327.3-0.6 (red)

Schilke et al. in prepAn insight into molecular complexity

A tool to compare chemical properties of different environments : evolution signatures ? differences between low and high-mass hot cores ?

FLASH observationsFLASH observations

APEX, opening the way for ALMA - Paris, Feb 3rd 2006 11

Summary

Observation of molecules is a powerful tool to probe not only the chemistry but also the physical conditions in astronomical sources.

The submillimetre range is an essential domain for these studies.