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Observations of Organic Molecules in Southern Molecular Clouds
Maria Hunt (UNSW, UWS, ATNF) John Whiteoak (ATNF) Paul Jones (UWS) Graeme White (UWS)


Investigating Star Formation in Southern Dense Molecular Cores l How?
­ Mopra and SEST observations of molecular transitions

between 1 and 3 mm. ­ Kinematic information from line profiles. ­ Temperatures and abundances from modelling of line emission.
l

Why?
­ To produce a statistical database of molecular emission

and abundances in southern molecular clouds. ­ To test theoretical predictions for molecular abundances in different physical regions of molecular clouds


SiO, SiO 2 , H2 O NO HCO+, N2 H+ CO, CS, HCN, HNC, HCO+, CN, C3 H2 , N2 H+, HC (2n+1)N T= 5- 25 K

CH3 OH, H2 CO, SO2 , H2CS, OH


As the gas density increases, molecules collide with and stick to the grain surfaces..... H+ HC5 N CS C HCO
+

HCN

HNC H+ O H+

C

HNC HC3 N

...new saturated molecules form on the grain surfaces such as CH3OH, OCS, NH3, H2CO ....


Ultracompact H II region

Hot Molecular Core T = 100 ­ 300 K

CS, SO, OCS, CH3 OH, SO2 , HCOOCH3 , CH3 CH2 OH


Observed Sample
l

27 bright galactic- plane molecular clouds with declinations south of ­30o
­ (250o< l < 2o).

l

Telescopes
­ The Mopra Telescope (86-116 GHz) ­ The SEST (84-250 GHz)


The Mopra Telescope ..
­ ­ ­ ­

Diameter 15 m (until 1999), 22 m (after 1999). 86 GHz ­ 116 GHz UNSW, ATNF Coonabarabran, NSW, Australia


Molecules
l

Transitions of the molecules CO, CS, HCN, HNC, HCO+, HC3 N, OCS, CH3OH and SO and several of their isotopomers with frequencies from 86 - 240 GHz Beam 30 ­ 60 arcsec

l




Calculating Abundances
l

Rotation Diagrams
­ Goldsmith, P.F. & Langer, W.D., 1999. Ap.J., 517,

209.
l

LVG Modelling
­ LVG code courtesy of Dr Peter Schilke, MPIFR. ­ Extension to LVG code for HC 3 N (Maria Hunt). ­ Castor, J.I., 1970. MNRAS, 149, 111. ­ Lampton, M., Margon, B. & Bowyers, S., 1976. Ap.J.,

208, 177.






Results
l

Most of the dense cores showed some evidence for recent or ongoing star formation:
­ Detection of thermal CH3 OH emission. ­ Detection of OCS emission. ­ Line wings suggestive of outflow.

l

G291.3-0.7, G345.5+1.5, NGC 6334(S), NGC 6334(N), NGC 6334(N1), G351.6-1.3 and G353.4-0.4 probably contain hot cores.


More Results
l

The Galactic-Centre cloud G1.6 -0.025 is probably undergoing a cloud- cloud collision. The molecular clouds G265.1+1.5, G291.3 0.7 and G1.6 -0.025 have self- absorbed line profiles in many molecules, suggesting a complex cloud structure and kinematics.

l


ATCA mm-observations
The higher resolution will enable the observation of more chemically homogeneous regions involved in starformation. l Thermal CH3 OH: At least 7 transitions within the 86 ­115 GHz range. l HC3N and OCS have 3 transitions each accessible with the ATCA.
l