A Search For Interstellar Urea With CARMA Hsin-Lun Kuo, Lewis Snyder, Douglas Friedel, Leslie Looney, Benjamin McCall (UIUC), Anthony Remijan (NRAO), Frank Lovas (NIST), Jan Hollis (NASA)

Motivation Urea (NH 2 ) 2 CO has measured and calculated laboratory frequencies good to a few kHz. In preparation of CARMA search for protonated methanol (frequencies measured by McCall group), we wish to develop procedures with trustworthy calibrator fluxes, proper baseline subtraction, and self calibration to extract weak emission lines from CARMA data.

CARMA ( Combined Array for Research in Millimeter- wave Astronomy ) Owens Valley Radio Observatory (OVRO) m X6 Berkeley-Illinois-Maryland Association (BIMA) m X9 105 baselines Angular resolution about 0.3", 0.8", 2", 5", or 10" at 100 GHz in A, B, C, D, and E configuration Operates at 3 mm ( GHz) and 1 mm ( GHz)

Urea Lines Frequency(GHz)Q.N.Frequency(GHz)Q.N (7)4(4,1)-3(3,0) (31)18(*,17)-17(*,16) (9)7(*,6)-6(*,5) (45)19(*,19)-18(*,18) (11)8(*,8)-7(*,7) (37)19(*,18)-18(*,17) (10)8(1,7)-7(2,6) (53)20(*,20)-19(*,19) (10)8(2,7)-7(1,6) (44)20(*,19)-19(*,18) (11)9(*,9)-8(*,8) (63)21(*,21)-20(*,20) (9)5(5,1)-4(4,0) (53)21(*,20)-20(*,19) (9)5(5,0)-4(4,1) (74)22(*,22)-21(*,21) (62)22(*,21)-21(*,20) (86)23(*,23)-22(*,22) (73)23(*,22)-22(*,21) (99)24(*,24)-23(*,23)

Urea Energy Levels

Continuum Map of Sgr B2 (N)

Urea 1mm Spectra

Line Fits & Spectral Analysis Beam averaged total number density (cross- correlation array) (See Appendix in Snyder et al. 2005) Intensity ratio

Temperature Plots Plot I 1 v.s. T rot All plots consistent with T rot ~ 80 K Previous BIMA result T rot = 77 K

Urea 1mm Spectra

Urea 3mm Spectra

Conclusion Rotational temperature T rot ~ 80K Linewidth v ~ 2.05 km s -1 Beam-averaged total column density N tot = cm -2 Proper coupling of source size to the beam size is essential for flux measurements and detection limits; it helps bring out weak signals that are otherwise blended with extended emission.