Pia Denzmore 2005 Summer Research

Pia M Denzmore

REU program-Summer 2005
Univ. of Wisconsin - Madison
Madison, WI 53706
piadenz@gmail.com
Advisor: Dr. Barbara Whitney

Background
Why study RCW 106?
Star formation in RCW 106
References & Useful Links
My Summer 2004 Research Project
Research projects of other REU students

Characterizing Star Formation in the Giant H II Region RCW 106 using GLIMPSE data

H II Regions of Interest

Young massive stars are very lumnious and emit large amounts of UV radiation which ionizes their surrounding environment. H II regions, therefore, are good indicators of ongoing star formation. There are several large H II regions in RCW 106 and below are RGB (blue:[3.6], green:[4.5], red:[5.8]) composite images of three very bright H II regions of interest. Polycyclic aromatic hydrocarbons (PAHs), not ionized gas, located in the region are responsible for the diffuse red emission. PAHs emit strongly at 5.8 and 8.0 microns which correspond to GLIMPSE bands 3 & 4.

*Young Stellar Cluster (RA:16:21:31.230 DEC:-50:25:07.54):* This H II region is a bright radio source and contains at least 41 near-infrared sources which may be developing protostars (Roman-Lopes et al.). The cluster is associated with the infrared source, IRAS 16177-5018, which may be a massive (~42 Msun) protostar.	*Dark Clouds and Jets (RA:16:19:37.668 DEC:-51:03:14.92)* This image spans approximately 0.45 degrees on the sky. Among the sources in this image are sources with detected molecular outflows, water and methanol masers and the bright IRAS 16158-5055 mid-infrared source.

*G333.6-0.2(RA:16:22:10.1 DEC: -50:53:15)* This complex hosts the well known H II region, G333.6-0.2.The center ionizing cluster is estimated to contain a dozen or more OB stars and it also contains one of the brightest infrared sources in the galaxy, IRAS 16183-4985.

Molecular Jets

Each of the IRAC bands used in the GLIMPSE survey is sensitive to certain features which help in understanding mechanisms and indicators for star formation. Band 1 at 3.6 microns is sensitive to neutral PAH emission, Bands 3 and 4, 5.8 and 8.0 microns respectively, are sensitive to positively charged PAH emission. Band 2 (4.5 microns) is special in that although it contains no PAH features, it does contain very important CO and molecular hydrogen lines. The GLIMPSE survery has uncovered hundreds of sources which only appear at 4.5 microns and since this emission is probably a result of shock heated molecular gas, they are most likely molecular outflows, or jets, from young stellar objects (YSOs).

Why do YSOs form jets? While a protostar is accreting material from its accretion disk, it must conserve angular momentum. Bipolar outflows conserve angular momentum in the system by ejecting large amounts of energy and material into space. This material travels at very high velocities and as it hits the surrounding interstellar medium it produces shocks. Therefore, the shock heated molecular gas emission at 4.5 microns is a good indicator of star formation. It is believe that high mass protostars have more collimated outflows than their low mass counterparts.

Below are four candidate YSOs with molecular outflow emission at 4.5 microns (green).

Bow Outflow (RA:16:20:02.81 DEC:-51:00:32.06)
This bright outflow is a known water, methanol and OH maser. The strength of the [4.5] emission coupled with the maser emissions implies that this is a developing massive protostar. IRAS 16170-5053 (RA:16:20:48.136 DEC:-51:00:12.99)
Prominent bipolar curved outflows mark this bright IRAS and MSX source. A known H II region, it emits XRays and is a strong OH maser.

Silhouetted Outflows (RA:16:21:20 DEC:-50:53:05)
Bright [4.5] emission distinguishes two young maser sources against the background. The "fuzzy" source in the middle is IRAS 16175-5045.

Dark cloud outflows (RA: 16:21:20.113 DEC: -50:09:49.37)
IRAS 16175-5002 is an H II region detected by MSX and detected in X-Rays. Methanol and OH masers are also associated with this area.

Top

*Bow Outflow (RA:16:20:02.81 DEC:-51:00:32.06)* This bright outflow is a known water, methanol and OH maser. The strength of the [4.5] emission coupled with the maser emissions implies that this is a developing massive protostar.	*IRAS 16170-5053 (RA:16:20:48.136 DEC:-51:00:12.99)* Prominent bipolar curved outflows mark this bright IRAS and MSX source. A known H II region, it emits XRays and is a strong OH maser.
*Silhouetted Outflows (RA:16:21:20 DEC:-50:53:05)* Bright [4.5] emission distinguishes two young maser sources against the background. The "fuzzy" source in the middle is IRAS 16175-5045.	Dark cloud outflows (RA: 16:21:20.113 DEC: -50:09:49.37) IRAS 16175-5002 is an H II region detected by MSX and detected in X-Rays. Methanol and OH masers are also associated with this area.