The Organic Chemistry of Nearby Galaxies Measured with a New, Very Broadband Receiver
Millimeter-wavelength spectra of a number of nearby galaxies have been obtained at the
Five College Radio Astronomy Observatory (FCRAO) in Massachusetts using a new, very
broadband receiver (Erickson et al., 2007). This instrument, which we call the redshift
search receiver (RSR), has an instantaneous bandwidth of 36 GHz and operates from 74 to
110.5 GHz, permitting the measurement of most of the 3 mm spectrum with a single
receiver setting. The receiver has been built at UMass/FCRAO to be part of the initial
instrumentation for the Large Millimeter Telescope (LMT), a 50-m diameter millimeterwavelength
single-dish telescope being built jointly by UMass and the Instituto Nacional de
Astrofísica, Óptica y Electrónica in Mexico (Perez-Grovas et al., 2006). The LMT is sited at
4,600 m elevation at latitude 19° in the Mexican state of Puebla, permitting good access to
the southern sky. It is designed for operation in the 0.85–4 mm wavelength band.
The new receiver is intended for determination of the redshift and hence distance of
distant, dust-obscured galaxies, but it can also be used to investigate the chemistry of
galaxies. Since the LMT is not yet complete (we are hoping for initial 3 mm commissioning
this year), the receiver is being tested on the FCRAO 14 m by measuring the 3 mm spectra
of a number of nearby galaxies. There are interesting differences in the chemistry of these
objects, e.g., in the relative strength of emission lines from HCN, HNC, HCO+, CH3OH,
13CO, CS and N2H+ (a proxy for N2).
ORIGINS OF LIFE AND EVOLUTION OF BIOSPHERES
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