Query : 2021A&A...651L...5V

2021A&A...651L...5V - Astronomy and Astrophysics, volume 651, L5-5 (2021/7-1)

A major asymmetric ice trap in a planet-forming disk. I. Formaldehyde and methanol.


Abstract (from CDS):

Context. The chemistry of planet-forming disks sets the exoplanet atmosphere composition and the prebiotic molecular content. Dust traps are of particular importance as pebble growth and transport are crucial for setting the chemistry where giant planets form.
Aims. The asymmetric Oph IRS 48 dust trap located at 60 au radius provides a unique laboratory for studying chemistry in pebble-concentrated environments in warm Herbig disks with gas-to-dust ratios as low as 0.01.
Methods. We use deep ALMA Band 7 line observations to search the IRS 48 disk for H2CO and CH3OH line emission, the first steps of complex organic chemistry.
Results. We report the detection of seven H2CO and six CH3OH lines with energy levels between 17 and 260K. The line emission shows a crescent morphology, similar to the dust continuum, suggesting that the icy pebbles play an important role in the delivery of these molecules. Rotational diagrams and line ratios indicate that both molecules originate from warm molecular regions in the disk with temperatures >100K and column densities ∼1014cm–2 or a fractional abundance of ∼10–8 and with H2CO/CH3OH ∼0.2, indicative of ice chemistry. Based on arguments from a physical-chemical model with low gas-to-dust ratios, we propose a scenario where the dust trap provides a huge icy grain reservoir in the disk midplane, or an 'ice trap', which can result in high gas-phase abundances of warm complex organic molecules through efficient vertical mixing.
Conclusions. This is the first time that complex organic molecules have been clearly linked to the presence of a dust trap. These results demonstrate the importance of including dust evolution and vertical transport in chemical disk models as icy dust concentrations provide important reservoirs for complex organic chemistry in disks.

Abstract Copyright: © ESO 2021

Journal keyword(s): astrochemistry - protoplanetary disks

Simbad objects: 6

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Number of rows : 6
N Identifier Otype ICRS (J2000)
ICRS (J2000)
Mag U Mag B Mag V Mag R Mag I Sp type #ref
1850 - 2023
1 V* V883 Ori Or* 05 38 18.1018261392 -07 02 26.017707120           F:I: 190 0
2 V* TW Hya TT* 11 01 51.9053285064 -34 42 17.033218380   11.94 10.50 10.626 9.18 K6Ve 1808 1
3 HD 100546 Be* 11 33 25.4408872296 -70 11 41.241297948   6.71 6.30   6.64 A0VaekB8_lB 757 1
4 ATO J241.0901-21.5080 Y*O 16 04 21.6547947840 -21 30 28.550063304   13.3       K2 117 0
5 IRAS 16245-2423 TT* 16 27 37.1906433768 -24 30 35.025246828       16.66 14.67 B5-F2 281 0
6 NAME Ophiuchus Molecular Cloud SFR 16 28 06 -24 32.5           ~ 3476 1

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