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Meredith Hughes




Is the molecular gas in circumstellar debris disks the remnant of primordial gas or second-generation material produced in collisions of planetesimals and exocomets? It appears as if most disks are leaning towards a second-generation formation scenario yet several systems do not fit this scenario and with CO as the only detected molecular gas, the key to understanding the origin and evolution lies in understanding the molecular chemistry. We present a deep molecular survey of the nearby debris disk 49 Ceti with 0.900” angular resolution of five tracer molecules (HCN, CN, HCO+, SiO, CH3OH 1(1,1)-0(0,0) and 4(1,3)-3(0,3)) using the Atacama Large Millimeter/ submillimeter Array ( ALMA). We utilize previous spatially resolved observations of CO emission which revealed gas that is axisymmetric and consistent with Keplerian rotation to employ the spectral shifting and spatial averaging method pioneered by Matra (2017). Previous observations of 49 Ceti during ALMA Cycle 1 reached an rms noise of 3 mJy/beam in each 0.41km/s-wide channel at a spatial resolution of 0.5”. Our survey will average across all bands for a resolution of 0.8km/s and improve the expected sensitivity by an order of magnitude.

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