FAUST X: Formaldehyde in the Protobinary System [BHB2007] 11: Small Scale Deuteration

Abstract

Context. Deuterium in H-bearing species is enhanced during the early stages of star formation, however, only a small number of high spatial resolution deuteration studies exist towards protostellar objects, leaving the small-scale structures unrevealed and understudied. Aims. We aim to constrain the deuterium fractionation ratios in a Class 0/I protostellar object in formaldehyde (H2CO), which has abundant deuterated isotopologues in this environment. Methods. We observed the Class 0/I protobinary system [BHB2007] 11, whose emission components are embedded in circumstellar disks that have radii of 2-3 au, using ALMA within the context of the Large Program FAUST. The system is surrounded by a complex filamentary structure connecting to the larger circumbinary disk. In this work we present the first study of formaldehyde D-fractionation towards this source with detections of H2CO 3(0,3)-2(0,2), combined with HDCO 4(2,2)-3(2,1), HDCO 4(1,4)-3(1,3) and D2CO 4(0,4)-3(0,3). These observations enable multiple velocity components associated with the methanol hotspots also uncovered by FAUST data, as well as the external envelope, to be resolved. In addition, based on the kinematics seen in the observations of the H2CO emission, we propose the presence of a second large scale outflow. Results. HDCO and D2CO are only found in the central regions of the core while H2CO is found more ubiquitously. From radiative transfer modelling, the column densities ranges found for H2CO, HDCO and D2CO are (3-8)x10${}^{14}$ cm${}^{-2}$, (0.8-2.9)x10${}^{13}$ cm${}^{-2}$ and (2.6-4.3)x10${}^{12}$ cm${}^{-2}$, respectively, yielding an average D/H ratio of 0.01-0.04. Following the results of kinematic modelling, the second large scale feature is inconsistent with a streamer-like nature and we thus tentatively conclude that the feature is an asymmetric molecular outflow launched by a wide-angle disk wind.

17 pages, 15 figures

References in corpus (13)

• The ALMA Protostellar Interferometric Line Survey (PILS): First results from an unbiased submillimeter wavelength line survey of the Class 0 protostellar binary IRAS 16293-2422 with ALMA
• First detection of triply-deuterated methanol
• Parametrization of C-shocks. Evolution of the Sputtering of Grains
• Resolved images of a protostellar outflow launched by an extended disk wind
• A protostellar system fed by a streamer of 10,500 au length
• PRODIGE -- Envelope to disk with NOEMA I. A 3000 au streamer feeding a Class I protostar
• pyspeckit: A spectroscopic analysis and plotting package
• Gas flow and accretion via spiral streamers and circumstellar disks in a young binary protostar
• The Spitzer c2d Survey of Nearby Dense Cores: IV. Revealing the Embedded Cluster in B59
• Molecular outflow launched beyond the disk edge
• Deuterated methanol on Solar System scale around the HH212 protostar
• Structure of a protobinary system: an asymmetric circumbinary disk and spiral arms
• 2MASS J17112318-2724315: A Deeply-Embedded Low-Mass Protostellar System in the B59 Molecular Cloud