Thermal formaldehyde emission in NGC 7538 IRS 1

Spectral lines from formaldehyde (H2CO) molecules at cm wavelengths are typically detected in absorption and trace a broad range of environments, diffuse gas to giant molecular clouds. In contrast, thermal emission is rare. previous observations with the 100m Robert C. Byrd Green Bank Telescope (GBT), we 2 toward NGC7538 IRS1 - high-mass protostellar object prominent star-forming region our Galaxy. We present further GBT 1 H2CO investigate nature emission. conducted constrain angular size based on East-West North-South cross-scan map. Gaussian fits spatial distribution direction show deconvolved (at half maximum) 50" +/- 8". The revealed superimposed weak feature. A non-LTE radiative transfer analysis shows that consistent quasi-thermal radiation dense (~10^5 10^6 cm^-3). also report detection 4 transitions CH3OH (12.2, 26.8, 28.3, 28.9 GHz), (8,8) transition NH3 (26.5 map 13 GHz SO line extended (> 50").