ASTROCHEMISTRY IN THE SUBMM DOMAIN Bérengère Parise With kind inputs from my MPIfR colleagues: A....
-
Upload
randell-welch -
Category
Documents
-
view
212 -
download
0
Transcript of ASTROCHEMISTRY IN THE SUBMM DOMAIN Bérengère Parise With kind inputs from my MPIfR colleagues: A....
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.