2009 CCU Spring School
University of Arizona & Arizona Radio Observatory
March 23-26, 2009
During the Spring School, each group of students participated in two eight-hour observing sessions at the former NRAO 12 Meter (KP12m) Telescope located 50 miles southwest of Tucson on Kitt Peak. As a basic introduction to the tools and fundamentals of radio astronomy, the first session consisted of observations of several different molecules in a sample of representative sources. The second session consisted of initial measurements of a spectral-line survey using the new ALMA Band 3 (3 mm) receiver of three carbon-rich circumstellar shells: IRC+40540, CIT-6 and CRL-2688. Click here to see Dr. Ziurys' introductory Powerpoint presentation on "Radio Astronomy for Chemists."
The J = 1 → 0 transition near 88 GHz was observed in a cold, dark cloud: L134N, L673, or TMC-1. Due to their very low kinetic temperatures (T ~ 10 K), these sources have resolvable hyperfine splittings, arising from the N nucleus. Three hyperfine components were present in the spectrum, and the ratio of these lines was used to examine the optical depth in the clouds.
The J = 8 → 7 transition was observed near 147 GHz towards a hot core source: W51M, G34.3, or Orion-KL. As CH3CN is a symmetric top, the J = 8 → 7 transition actually consists of a "K-ladder" structure. The relative intensities of these K-ladders were used to estimate the gas kinetic temperature of the object observed.
Rotational transitions were observed at 3 mm and 2mm towards W51M, G34.3, or Orion-KL. The observations were used to construct a "rotational diagram" from which a molecular "column density" was extracted as well as the rotational temperature of the gas-phase HC3N.
The v = 0, J = 2 → 1 and v = 1, J = 2 → 1 transitions near 86 GHz were observed towards the circumstellar gas surrounding the stars Chi Cyg, R Leo, or R Cas. Differences in line shapes and intensity between v = 0 and v = 1 were noted to illustrate the non-thermal nature of many circumstellar and interstellar molecular sources.
The J = 1 → 0 transition near 115 GHz was observed towards 1) L134N, L673, or TMC-1; 2) W51M, Orion-KL, or G34.3; 3) Chi Cyg, R Leo, or R Cas, and 4) the external galaxy M51. These observations demonstrated the varied dynamical information contained in the molecular line profiles for the four types of sources. The J = 1 → 0 transition of 13CO near 110 GHz was also studied towards Chi Cyg, R Leo, or R Cas, allowing for the 12C/13C ratio to be obtained. In addition, because the emission from CO is widespread across the hot cores (W51M, G34.3, or Orion-KL), a 3x3 map with a grid spacing of 60" (arcseconds) was performed for these regions.
A 3 mm spectral survey of the envelopes around the stars IRC+40540, CIT6, and CRL2688 was begun using the new ALMA Band 3 receiver. Using the filter banks with 2 MHz resolution, 500 MHz of bandwidth was simultaneously observed per frequency setting for a period of time sufficient to achieve a low noise level. After this level was achieved, the next frequency was observed 0.5 GHz away, and so forth, with each group measuring two to three frequencies at high sensitivity during their observing shift. Spectral features were identified.
If interested in improving their skills and obtaining potentially publishable results, this project offers an opportunity for the Spring School participants to continue the survey via remote observing once they return to their home institutions.
For more info on the Spring School "Radio Astronomy for Chemists" exercises, download the full pdf file here.
University of Virginia
Michael Buettner -- Anthony Imberi -- Matt Muckle -- Jason Navin
Mahesh Rajappan -- Ana Stevanovic -- Izzie Wang -- Eun Yi
Ohio State University
George Hassel -- Yezhe Pei -- Donghui Quan
Harvard-Smithsonian Center for Astrophysics (CfA)
Valerio Lattanzi -- Silvia Spezzano
University of Arizona / Arizona Radio Observatory
Cathi Duncan -- Tom Folkers -- DeWayne Halfen
Robin Pulliam -- Lindsay Zack -- Lucy Ziurys
University of Virginia
Sara Fitzgerald -- Brooks Pate
Special thanks to Nanette Bird (Kitt Peak National Observatory) and Sandy Ostberg (Four Points by Sheraton University Plaza) for securing lodging and meals for the Spring School participants at their respective locations.
W. Klemperer, "Interstellar chemistry," P.N.A.S. 103, 12232-12234 (2006). View
E. F. van Dishoeck, "Chemistry in low-mass protostellar and protoplanetary regions," P.N.A.S. 103, 12249-12256 (2006). View
L.M. Ziurys, "The chemistry in circumstellar envelopes of evolved stars: Following the origin of the elements to the origin of life," P.N.A.S. 103, 12274-12279 (2006). View
Photos on this page are courtesy of Matt Muckle, George Hassel, and Tom Folkers - thank you!