Complex organic molecules in hot corinos

Sandrine BottinelliLaboratoire d’AstrOphysique de Grenoble (France) /

Institute for Astronomy (Hawaii)

Cecilia Ceccarelli (LAOG), Jonathan Williams (IfA)

and Roberto Neri (IRAM)

Outline: I – BackgroundII – 30m observations of NGC1333-IRAS4A

III – PdB observations of IRAS16293IV – Conclusions

Hot core: first stage in the evolution of massive protostars

• Compact (<0.1 pc), warm (>100 K), dense (>107 cm-3) regions.

• Rich chemistry: Saturated molecules, Complex organic molecules

(oxygen-, nitrogen-, sulfur-bearing).

• 1st discovered around Orion-KL (Morris et al. 1980). Nowadays, >20 massive hot cores.

• Many studies: e.g. Friedel et al. (this morning), Comito et al. (Friday morning).

Hot cores around Class 0?

Importance of hot corinos

1st hot corino discovered in IRAS16293-2422 (Cazaux et al. 2003).

From Ehrenfreund & Charnley 2000, ARA&A, 38, 427

Protoplanetary disks

Comets (e.g. Bockelée-Morvan, Wednesday)

Hot corinos (this work)

Questions and goals

• Is IRAS16293 an exception or is the hot corino phase common in the evolution of low-mass protostars?

Search for complex molecules towards other Class 0.

• Is the chemistry in hot corinos similar to that in massive hot cores?

Compare abundances.

• What are the formation mechanisms of these complex molecules?

Interferometry, laboratory work, chemical modeling.

30m observations of NGC1333-IRAS4A

• Perseus (220 pc), 6 L, binary 440 AU separation

• Observations at 1, 2 and 3mm

(Bottinelli et al. 2004a, ApJ 615, 354)

Spectra

• HCOOCH3-A (4), HCOOCH3-E (6), HCOOH (2), CH3CN (9)• Upper limits for CH3OCH3 and C2H5CN.

IRAS4A

Rotational diagrams

• HCOOCH3-A/E: x ~ 310-8

Trot = 36 K

IRAS4A

• HCOOH: 510-9, 10K• CH3CN: 210-9, 27 K

Assuming source size 0.5" (Maret et al. 2004) and N(H2) = 1.61024 cm-2.

Comparison with previous results

IRAS4A

Similar abundance ratio for O-bearing molecules, except CH3OH H2CO could be mother molecule.

Lack of CH3OH and N-bearing molecules in hot corinos difference in grain mantle composition?

Similar abundance ratios for N-bearing molecules common mother molecule (NH3?).

Similar abundance ratio for O-bearing molecules, except CH3OH H2CO could be mother molecule. Similar abundance

ratios for N-bearing molecules common mother molecule (NH3?).

PdB observations of IRAS16293-2422

Oph (160 pc), 27 L, binary 800 AU separation

• Continuum 1 and 3mm

• 5 lines CH3CN at ~110 GHz

• 4 lines HCOOCH3 (2 –A, 2 –E) at ~227 GHz

(Bottinelli et al. 2004b, ApJ 617, L69)

Line emission

• Beam: (a) 4.7"×1.6" (c) 2.2"×0.9"• Contour levels: (a) 15 mJy/beam (c) 20 mJy/beam

IRAS16293

110 GHz 227 GHz

Comparison with 30mIRAS16293

Confirms hot corinos are compact with sizes <1.5" (A) and <0.8" (B).

SMA observations

~345 GHz, beam ~ 2.7" 1.3" (Kuan et al. 2004, ApJ 616, L27).

IRAS16293

~300 GHz, beam ~ 1.9" 0.9" (Chandler et al. 2005, ApJ in press).

Continuum emission

SpectraIRAS16293

202,19-192,18

A E

201,19-191,18

A ECN 2-1

6 4,0-5 4,0

6 0,0-5 0,0

6 1,0-5 1,0

6 2,0-5 2,0

6 3,0-5 3,0

2 scenariosIRAS16293

MA ~ 1M

MB < MA

Vsin i = 1.2 km/s

830 AU

2

• VLSR (A) = 3.9 km/s and VLSR (B) = 2.7 km/s.

1

• VLSR (A,B) = 3.9 km/s.

• MA ~ MB, B more compact.

• Lines optically thick towards B.

Chemical modeling

• Coupling between chemistry, dynamics and radiative transfer is computationally intensive, but many efforts to tackle different aspects: – chemical evolution in protostellar envelopes (e.g. Rodgers &

Charnley 2003; Doty et al. (2004); – laboratory studies (e.g. Horn et al. 2004); – molecular line profiles (e.g. Lee et al. 2004);– chemical clocks (e.g. Wakelam et al. 2004, previous talk);– grain surface reactions (e.g. Weaver & Blake this afternoon).

• Problem = difficult to reconcile theory and observations for gas-phase formation of complex molecules (e.g. for HCOOCH3 - Horn et al. 2004).

Conclusions

• Hot corinos exist and have been imaged.• IRAS16293 not alone (however still don’t

know how common hot corinos are).• Open questions:

– What are the formation mechanisms of these molecules?

– Evolution, link with comets?

to answer, continue the effort through combining modeling and observations.