1. Glen Langston: OSU 08 1 Improved Tools for Astrochemistry Glen Langston Methods for detection of families of molecules Example: HC 7 N collaboration with Barry Turner Wide-band Spectrometers Focal Plane Arrays NRAO

2. Glen Langston: OSU 08 2 Molecular Discoveries: 100m World’s most sensitive Telescope in frequency range 10 to 50 GHz Discovered >7 new interstellar molecules, including propenal and propanal Widely distributed, not exclusively in compact cores Hollis, Snyder, Remijan and Jewell 2004-2008

3. Glen Langston: OSU 08 3 HC 7 N HC 9 N HC 11 N and HC 13 N HC 7 N HC 9 N HC 11 N and HC 13 N Large Cyanopolyynes known to be abundant in TMC-1

4. Glen Langston: OSU 08 4 HC 9 N, HC 11 N and HC 13 N HC 9 N, HC 11 N and HC 13 N Straight forward lesson: Larger molecules exhibit more lines at lower frequencies than their simpler counterparts. Wide bandwidth spectrometers needed with full frequency coverage at high spectral resolution. Improved spectrometer is a priority for NRAO

5. Glen Langston: OSU 08 5 Updated HC 13 N Model Updated HC 13 N Model Frequency (MHz) Intensity (Kelvin) Model of HC 13 N line strength for Taurus Molecular Cloud Models for HC13N moments of inertia and Taurus cloud temperature (9 Kelvin's) show peak of emission at 12 to 15 GHz Prediction common to all ‘large’ molecules in cold clouds: Many lines at lower frequencies (< 20 GHz) Spacing between HC11N lines 338 MHz Spacing between HC13N lines 214 MHz (17 lines in 3.6 GHz)

6. Glen Langston: OSU 08 6 Selections of HC 13 N observations Simultaneous four 50 MHz bandwidth observations HC13N Lines are separated by 214 MHz

7. Glen Langston: OSU 08 7 Daily System Check Daily system check observations: Two 4 minute observations. Simultaneous four 50 MHz bandwidth Widely separated (Delta nu > 1 GHz)

8. Glen Langston: OSU 08 8 HC 7 N and HC 9 N We concentrated on larger HCnN molecules with fourth band.

9. Glen Langston: OSU 08 9 HC 7 N Isotopomers In the HC 13 N observations, a family of 13 C Isotopomers is detected Ratio of HC 7 N and Isotopomers Abundance = 87:1 Langston and Turner (2007), Ap. J. 658, 455

10. Glen Langston: OSU 08 10 K-band Focal Plane Array SpecificationRequirement Frequency Band18-26.5 GHz (complete K- Band coverage) Instantaneous RF Bandwidth 1.8 GHz Number of beams7 (expandable up to 61) T RX (each beam, not including sky) < 25 K (75% of band) * < 35 K (entire band) Aperture Efficiency>55%, any pixel Polarizationdual, circular (axial ratio <= 1 dB) Polarization Isolation >25 dB Pixel-Pixel Isolation>30 dB Headroom> 30 dB (to 1 dB compression point)

11. Glen Langston: OSU 08 11 Design Configuration Single Pixel High performance multi-pixel is technically challenging Seven Pixel

12. Glen Langston: OSU 08 12 Mapping Large Regions

13. Glen Langston: OSU 08 13 Future Directions Lower frequency (6 to 26 GHz) observations are critical for study of important large molecules. Demonstrated detection of a class of molecules by simultaneous observation of weak lines. Isotopomers are a significant fraction for large molecules (7/50 ~ 1/7 for HC7N) Studies of Astro-chemistry will be advanced by: Increasing spectrometer bandwidth Increasing number of beams in receivers Software for optimum “folded” searches of multiple lines in large molecules