Unveiling the Chemistry of Hot Protostellar cores with ALMA

Unveiling the Chemistry of Hot
Protostellar cores with ALMA
M. Guélin (IRAM)
N. Brouillet (ObsBx), J. Cernicharo (DAMIR),
F. Combes (ObsParis), A. Wooten (NRAO)
M. Guelin, Science with ALMA, Madrid Nov 2006
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Outline
1. Introduction: Hot core chemistry models
2. Single-dish surveys of Orion Hot core
region (GBT @43 GHz and IRAM 30-m
@101GHz and 223 GHz)
3. PdB Interferometer survey of the same
region
4. Conclusions and Future prospects
M. Guelin, Science with ALMA, Madrid Nov 2006
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Example of Hot core chemistry models:
coupled grain+gas-phase chemistry
Garrod & Herbst -2006
1. Cold collapse phase
Grain mantle
NH3
10-4
Gas phase
CH3OH
10-12
106 yr
M. Guelin, Science with ALMA, Madrid Nov 2006
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2. Followed by warm-up phase
gas
grain
mantles
HCOOCH3
→Results…
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….To be compared with observed abundances
JCMT (HPBW 14”)
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Difficulties encountered when
measuring molecular abundances
• Spectral line confusion
• Line-of-sight confusion
• Limited spatial resolution
→Mix up gas with different physical and
chemical conditions.
→ observe several rotational transitions
→ observe with high angular resolution
Need Spectral line survey with
interferometer.
M. Guelin, Science with ALMA, Madrid Nov 2006
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4. The quest for the Holy Graal
(or more modestly for glycine)
a) Historics
b) New search in Orion-A (Hot Core) with the
GBT at 43 GHz
c) Search with the IRAM 30-m at 101 &223 GHz
d) New search with the IRAM PdB interferometer
at 101 & 223 GHz
Guélin, Combes, Brouillet, Wooten,…(in progress)
M. Guelin, Science with ALMA, Madrid Nov 2006
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Target of a new search for glycine: the Orion-A
Hot Core Guélin, Combes, Brouillet, Wooten,…(in progress)
1
2
3
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NRAO Green Bank 100-m
telescope
IRAM 30-m telescope on Pico Veleta
IRAM Plateau de Bure Interferometer
Telescopes usedM.for
the search: GBT @43
Guelin, Science with ALMA, Madrid Nov 2006
GHz, PV and PdBI @101 GHz and 223 GHz
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30-m HPBW
@100 GHz
30-m tel
@230 GHz
PdBI HPBW
NH3
M. Guelin, Science with ALMA, Madrid Nov 2006
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Green Bank 100-m Telescope observations
(43-46 GHz survey of Orion IRC2)
In red: lines assigned to known molecules; in green: unidentified
lines
M. Guelin, Science with ALMA, Madrid Nov 2006
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IRAM 30-m telescope spectrum of Orion IRC2
Around 101.5 GHz
predicted transitions of glycine are in blue; Identified lines in red.
Note the strong H2CO and H2CS lines
M. Guelin, Science with ALMA, Madrid Nov 2006
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Same spectrum as above, but expanded y scale
Note the strong H2CO and H2CS lines
M. Guelin, Science with ALMA, Madrid Nov 2006
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Same spectrum as previous one, but with line identifications
(in red). Unidentified lines in green (noted U)
M. Guelin, Science with ALMA, Madrid Nov 2006
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IRAM 30-m telescope spectrum of Orion IRC2
Around 223 GHz ( line identifications in red.
Unidentified lines in green )
M. Guelin, Science with ALMA, Madrid Nov 2006
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IRAM Plateau de Bure interferometer
M. Guelin, Science with ALMA, Madrid Nov 2006
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Map of Orion Hot Core with PdBI @ 101.2-101.8 GHz
1.5”x 2.5” resolution
Spectrum observed in one 1.5”x2.5” beam
Spectrum integrated over whole map
Velocity-Integrated map of the area
covered by the 30-m beam
M. Guelin, Science with ALMA, Madrid Nov 2006
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CH3OH
Same as previous,but at a different
position
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Same as previous: note the differences in the spectra
M. Guelin, Science with ALMA, Madrid Nov 2006
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C
D
B
A
M. Guelin, Science with ALMA, Madrid Nov 2006
PdB interferometer
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Orion Hot Core SMA- 690 GHz -1” resoln
2006
M. Guelin, Science with ALMA, Madrid Nov 2006
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Some conclusions
• High resolution (interferometric) observations do
lower the confusion limit in the richest molecular
sources (Orion-A,…). Lines are strong at submm λ
• These sources (hot cores) show a rich structure
• The molecular column densities (and molecular
abundance ratios) derived from lower resolution
single-dish observations could be off by orders of
magnitude
• Available single-dish spectral surveys must be
complemented by interferometric surveys
M. Guelin, Science with ALMA, Madrid Nov 2006
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Future (1)
PdBI
1. Existing
interferometers:
(VLA, PdB,
CARMA, SMA)
730 m
760 m
M. Guelin, Science with ALMA, Madrid Nov 2006
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Future (2)
ALMA: the “ultimate” machine will
ally
– high spatial resolution (0.02” is 10AU at
Orion A’s distance) to
– high spectral resolution
– wide spectral range
– and high sensitivity
M. Guelin, Science with ALMA, Madrid Nov 2006
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