2019A&A...631A..69M


C.D.S. - SIMBAD4 rel 1.7 - 2021.02.24CET22:14:57

2019A&A...631A..69M - Astronomy and Astrophysics, volume 631A, 69-69 (2019/11-1)

Bright C2H emission in protoplanetary discs in Lupus: high volatile C/O > 1 ratios.

MIOTELLO A., FACCHINI S., VAN DISHOECK E.F., CAZZOLETTI P., TESTI L., WILLIAMS J.P., ANSDELL M., VAN TERWISGA S. and VAN DER MAREL N.

Abstract (from CDS):


Context. Recent ALMA surveys in different star-forming regions have shown that CO emission in protoplanetary discs is much fainter than expected. Accordingly, CO-based gas masses and gas to dust ratios are orders of magnitude lower than previously thought. This may be explained either as fast gas dispersal, or as chemical evolution and locking up of volatiles in larger bodies leading to the low observed CO fluxes. The latter processes lead to enhanced C/O ratios in the gas, which may be reflected in enhanced abundances of carbon-bearing molecules like C2H.
Aims. The goal of this work is to use C2H observations to understand whether low CO fluxes are caused by volatile depletion or by fast gas dissipation.
Methods. We present ALMA Cycle 4 C2H (N=3-2, J=7/2-5/2, F=4-3 and F=3-2) observations of a subsample of nine sources in the Lupus star-forming region. The integrated C2H emission is determined and compared to previous CO isotopologue observations and physical-chemical model predictions.
Results. Seven out of nine discs are detected in C2H, whose line emission is almost as bright as 13CO. All detections are significantly brighter than the typical sensitivity of the observations, hinting at a bimodal distribution of the C2H line intensities. This conclusion is strengthened when our observations are compared with additional C2H observations of other discs. When compared with physical-chemical models, the observed C2H fluxes can be reproduced only if some level of volatile carbon and oxygen depletion is allowed and [C]/[O]>1 in the gas. Models with reduced gas-to-dust ratios near unity however fail to reproduce the observed C2H line luminosity. A steeper than linear correlation between C2H and CN emission line is found for the Lupus discs. This is linked to the fact that C2H emission lines are affected more strongly by [C]/[O] variations than CN lines. Ring-like structures are detected both in C2H and in continuum emission but, as for CN, they do not seem to be connected. The source Sz 71 shows ring-shaped emission in both C2H and CN with the location of the peak intensity coinciding, within our 30 au resolution.
Conclusions. Our new ALMA C2H observations favour volatile carbon and oxygen depletion rather than fast gas dispersal to explain the faint CO observations for most of the discs. This result has implications for disc-evolution and planet-formation theories, as disc gas masses may be larger than expected if CO is considered to be the main carbon carrier in the gas phase.

Abstract Copyright: © ESO 2019

Journal keyword(s): protoplanetary discs - astrochemistry - methods: observational - submillimeter: planetary systems - ISM: molecules - radiative transfer

VizieR on-line data: <Available at CDS (J/A+A/631/A69): list.dat fits/*>

Simbad objects: 23

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Number of rows : 23

N Identifier Otype ICRS (J2000)
RA
ICRS (J2000)
DEC
Mag U Mag B Mag V Mag R Mag I Sp type #ref
1850 - 2021
#notes
1 V* DM Tau Or* 04 33 48.7335659850 +18 10 09.974471722 14.30 14.82 14.00     M2Ve 532 0
2 EM* LkCa 15 Or* 04 39 17.7912813350 +22 21 03.387667491   13.01 12.03 11.61   K5:Ve 579 1
3 V* GM Aur Or* 04 55 10.9813656049 +30 21 59.375978047 14.59 14.22 13.10     K3Ve 565 0
4 HD 31648 Ae* 04 58 46.2654165113 +29 50 36.990341242 7.84 7.78 7.62 7.76 7.43 A5Vep 411 0
5 V* TW Hya TT* 11 01 51.9054298616 -34 42 17.031550898   11.94 10.50 10.626 9.18 K6Ve 1594 1
6 NAME Chamaeleon Region SFR 11 55 -78.0           ~ 708 0
7 QSO B1424-41 QSO 14 27 56.29756536 -42 06 19.4375991   18.48 17.7 16.30   ~ 378 1
8 QSO B1514-24 BLL 15 17 41.8135246339 -24 22 19.482167214   15.13 14.00 13.95   ~ 665 3
9 CD-33 10685 Or* 15 45 12.8670160093 -34 17 30.646921079 12.47 11.56 10.224 9.60 8.685 K3Ve 228 1
10 V* GW Lup Or* 15 46 44.7292759994 -34 30 35.677245389   13.8       M1.5e 91 0
11 THA 15-12 Or* 15 56 09.2067120748 -37 56 06.126159332   13.12 11.93 11.45   M0e 275 0
12 WRAY 15-1400 TT* 15 59 16.4714616661 -41 57 10.300292528   13.5 12.0     K7IVe 64 0
13 V* MY Lup TT* 16 00 44.5199369001 -41 55 30.931594414   12.64 12.17 11.06   K0 69 0
14 2MASS J16011549-4152351 Y*O 16 01 15.492 -41 52 35.19           ~ 24 0
15 NAME Lup Cloud SFR 16 03 -38.1           ~ 548 0
16 2MASS J16070384-3911113 Y*O 16 07 03.8309506752 -39 11 11.679148554       18.79 16.80 M4.5 29 0
17 2MASS J16070854-3914075 LM* 16 07 08.5541572537 -39 14 07.513184501   17.85   18.67 17.86 M1.75 26 0
18 V* V1279 Sco Or* 16 08 22.4935035747 -39 04 46.427826148   14.99 13.66 11.70 11.21 M0.4 88 1
19 2MASS J16090141-3925119 Y*O 16 09 01.4148763417 -39 25 11.923408383   16.92 15.31 15.04 13.48 M4 37 0
20 THA 15-35 Or* 16 09 01.8488471357 -39 05 12.416220509   15.33 14.12 14.35 12.54 M5.5 74 0
21 ICRF J161021.8-395858 QSO 16 10 21.87908922 -39 58 58.3284422       18.5   ~ 63 1
22 HD 163296 Ae* 17 56 21.2882188601 -21 57 21.872343282 7.00 6.93 6.85 6.86 6.67 A1Vep 839 0
23 HD 319139 LM* 18 14 10.4818974563 -32 47 34.516106830   11.47 10.68   9.11 K5+K7 306 0

    Equat.    Gal    SGal    Ecl

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