An ALMA Survey of H$_2$CO in Protoplanetary Disks

Jamila Pegues; Karin I. Öberg; Jennifer B. Bergner; Ryan A. Loomis; Chunhua Qi; Romane Le Gal; L. Ilsedore Cleeves; Viviana V. Guzmán; Jane Huang; Jes K. Jørgensen; Sean M. Andrews; Geoffrey A. Blake; John M. Carpenter; Kamber R. Schwarz; Jonathan P. Williams; David J. Wilner

doi:10.3847/1538-4357/ab64d9

paper

An ALMA Survey of H $_{2}$ CO in Protoplanetary Disks

arXiv:2002.12525 · doi:10.3847/1538-4357/ab64d9

Abstract

H $_{2}$ CO is one of the most abundant organic molecules in protoplanetary disks and can serve as a precursor to more complex organic chemistry. We present an ALMA survey of H $_{2}$ CO towards 15 disks covering a range of stellar spectral types, stellar ages, and dust continuum morphologies. H $_{2}$ CO is detected towards 13 disks and tentatively detected towards a 14th. We find both centrally-peaked and centrally-depressed emission morphologies, and half of the disks show ring-like structures at or beyond expected CO snowline locations. Together these morphologies suggest that H $_{2}$ CO in disks is commonly produced through both gas-phase and CO-ice-regulated grain-surface chemistry. We extract disk-averaged and azimuthally-averaged H $_{2}$ CO excitation temperatures and column densities for four disks with multiple H $_{2}$ CO line detections. The temperatures are between 20-50K, with the exception of colder temperatures in the DM Tau disk. These temperatures suggest that H $_{2}$ CO emission in disks is generally emerging from the warm molecular layer, with some contributions from the colder midplane. Applying the same H $_{2}$ CO excitation temperatures to all disks in the survey, we find that H $_{2}$ CO column densities span almost three orders of magnitude ( $\sim 5 \times 1 0^{11} - 5 \times 1 0^{14} cm^{- 2}$ ). The column densities appear uncorrelated with disk size and stellar age, but Herbig Ae disks may have less H $_{2}$ CO compared to T Tauri disks, possibly because of less CO freeze-out. More H $_{2}$ CO observations towards Herbig Ae disks are needed to confirm this tentative trend, and to better constrain under which disk conditions H $_{2}$ CO and other oxygen-bearing organics efficiently form during planet formation.

20 pages, 14 figures, 3 figure sets, 9 tables. Published in ApJ (February 2020)

An ALMA Survey of H $_{2}$ CO in Protoplanetary Disks

Abstract

References in corpus (18)

Cited by in corpus (18)

An ALMA Survey of H2​CO in Protoplanetary Disks

Abstract

References in corpus (18)

Cited by in corpus (18)

An ALMA Survey of H $_{2}$ CO in Protoplanetary Disks