2007ApJ...660L.125H

An analysis of continuum antenna temperatures observed in the GBT spectrometer bandpasses is presented for observations toward Sgr B2(N-LMH). Since 2004, we have identified four new prebiotic molecules toward this source by means of rotational transitions between low-energy levels; concurrently, we have observed significant continuum in GBT spectrometer bandpasses centered at 85 different frequencies in the range 1-48 GHz. The continuum heavily influences the molecular spectral features since we have observed far more absorption lines than emission lines for each of these new molecular species. Hence, it is important to understand the nature, distribution, and intensity of the underlying continuum in the GBT bandpasses for the purposes of radiative transfer, i.e., the means by which reliable molecular abundances are estimated. We find that the GBT spectrometer bandpass continuum is consistent with optically thin, nonthermal (synchrotron) emission with a flux density spectral index of -0.7 and a Gaussian source size of ∼143" at 1 GHz that decreases with increasing frequency as ν^–0.52. Some support for this model is provided by high-frequency VLA observations of Sgr B2.