Optical and millimeter-wave observations of the M8 region

Journal Article · Thu Jan 01 04:00:00 EST 1976 · Astrophysical Journal

DOI:https://doi.org/10.1086/154058· OSTI ID:4027462

Lada, C. J.; Gottlieb, C. A.; Gottlieb, E. W.; Gull, T. R.

Millimeter-wave observations made toward the NGC 6530-M8 star-forming complex are compared with high-quality optical interference-filter photographs of that region taken with the new Kitt Peak 4-m Mayall telescope and the Kitt Peak No. 192-cm telescope. Extensive CO observations reveal a large molecular cloud in this direction, within which three bright spots of CO emission are found. Two bright spots are associated in angle with prominent optical features. One of these is coincident with the star Herschel 36 and the well known Hourglass Nebula, and the second appears coincident in angle with a bright-rimmed structure shown to be an ionization front southeast of Herschel 36. Emission from H₂CO at 140.8 GHZ and H₂O at 22.2 GHz has been detected from this last bright spot but not from the other two. The third bright spot does not seem to be associated with any visible nebular feature. Carbon monoxide, radio continuum, and optical Hα emission are found to be very similar in angular distribution throughout M8. The kinematics of the molecular cloud are studied, and it is found that the radial velocity of CO emission varies smoothly across the cloud, but it is difficult to interpret this in terms of coherent mass motion of the entire cloud. Analysis of available radial-velocity data for the H ii region shows that the ionized gas is approaching the Earth at a velocity of 7 km s^-1 with respect to the molecular cloud. Analyses of CO, radio continuum, and, especially, optical data indicate that Herschel 36 is the most likely ionizing source for most of the M8 H ii region.

• Research Organization: Center for Astrophysics, Harvard College Observatory
• Sponsoring Organization: USDOE
• NSA Number: NSA-33-030790
• OSTI ID: 4027462
• Journal Information: Astrophysical Journal, Journal Name: Astrophysical Journal Vol. 203; ISSN 0004-637X
• Publisher: Institute of Physics (IOP)
• Country of Publication: United States
• Language: English

Related Subjects

*INTERSTELLAR SPACE-- MOLECULES
79 ASTRONOMY AND ASTROPHYSICS
ANGULAR DISTRIBUTION
CARBON MONOXIDE
COSMIC GASES
H2 REGIONS
HYDROGEN COMPOUNDS
NEBULAE
RADIAL VELOCITY
RADIOWAVE RADIATION
STAR CLUSTERS
VISIBLE RADIATION
WATER