First CH3D detection in Class 0/I proto-brown dwarfs: constraints on CH4 abundances. Issue 1 (27th January 2022)

• Record Type: Journal Article
• Authors: Riaz, B; Thi, W-F
• Is Part Of: Monthly notices of the Royal Astronomical Society. Volume 511:Issue 1(2022)
• Page Start: L50
• Page End: L54
• Publication Date: 2022-01-27
• Subjects: astrochemistry -- brown dwarfs -- stars: evolution -- stars: formation -- stars: individual: ISO-OPH 200 -- ISM: abundances -- ISM: molecules; Astronomy -- Research -- Periodicals; Periodicals; 520.5
• DOI: 10.1093/mnrasl/slac007
• Languages: English
• ISSNs: 1745-3933

Abstract

ABSTRACT: We report the first detection in the JK = 10 –00 rotational transition line of CH3 D towards three Class 0/I proto-brown dwarfs (proto-BDs) from IRAM 30-m observations. Assuming a rotational temperature of 25 K, the CH3 D abundances (relative to H2 ) are in the range of (2.3–14.5) × 10 −7 . The CH4 abundances derived from the CH3 D abundances and assuming the DCO + /HCO + ratios are in the range of (0.05–4.8) × 10 −5 . The gas-phase formation of CH3 D via CH2 D + is enhanced at high densities of 10 8 –10 10 cm −3 and our observations are likely probing the innermost dense and warm regions in proto-BDs. Thermal and/or non-thermal desorption can return the CH3 D and CH4 molecules formed at an early stage on grain surfaces to the gas-phase. The gas-phase abundances are indicative of warm carbon-chain chemistry in proto-BDs where carbon-chain molecules are synthesized in a lukewarm (∼20–30 K) region close to the central source.