2004A&A...425..955T


Query : 2004A&A...425..955T

2004A&A...425..955T - Astronomy and Astrophysics, volume 425, 955-972 (2004/10-3)

Organic molecules in protoplanetary disks around T Tauri and Herbig Ae stars.

THI W.-F., VAN ZADELHOFF G.-J. and VAN DISHOECK E.F.

Abstract (from CDS):

The results of single-dish observations of low- and high-J transitions of selected molecules from protoplanetary disks around two T Tauri stars (LkCa 15 and TW Hya) and two Herbig Ae stars (HD 163296 and MWC 480) are reported. Simple molecules such as CO, 13CO, HCO+, CN and HCN are detected. Several lines of H2CO are found toward the T Tauri star LkCa 15 but not in other objects. No CH3OH has been detected down to abundances of 10–9-10–8 with respect to H2. SO and CS lines have been searched for without success. Line ratios indicate that the molecular emission arises from dense (106-108cm–3) and moderately warm (T∼20-40K) intermediate height regions of the disk atmosphere between the midplane and the upper layer, in accordance with predictions from models of the chemistry in disks. The sizes of the disks were estimated from model fits to the 12CO 3-2 line profiles. The abundances of most species are lower than in the envelope around the solar-mass protostar IRAS 16293-2422. Freeze-out in the cold midplane and photodissociation by stellar and interstellar ultraviolet photons in the upper layers are likely causes of the depletion. CN is strongly detected in all disks, and the CN/HCN abundance ratio toward the Herbig Ae stars is even higher than that found in galactic photon-dominated regions, testifying to the importance of photodissociation by radiation from the central object in the upper layers. DCO+ is detected toward TW Hya, but not in other objects. The high inferred DCO+/HCO+ ratio of ∼0.035 is consistent with models of the deuterium fractionation in disks which include strong depletion of CO. The inferred ionization fraction in the intermediate height regions as deduced from HCO+ is at least 10–11-10–10, comparable to that derived for the midplane from recent H2D+ observations. Comparison with the abundances found in cometary comae is made.

Abstract Copyright:

Journal keyword(s): ISM: molecules - stars: circumstellar matter - stars: pre-main-sequence - astrochemistry

Simbad objects: 20

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Number of rows : 20
N Identifier Otype ICRS (J2000)
RA
ICRS (J2000)
DEC
Mag U Mag B Mag V Mag R Mag I Sp type #ref
1850 - 2022
#notes
1 IC 63 HII 00 59 01.37 +60 53 17.8   13.33       ~ 92 1
2 NAME W 3 OH HII 02 27 04.1 +61 52 22           ~ 981 2
3 [JCC87] IRAS 4A Y*O 03 29 10.49 +31 13 30.8           ~ 669 1
4 [JCC87] IRAS 4 FIR 03 29 10.9 +31 13 26           ~ 473 0
5 [JCC87] IRAS 4B Y*O 03 29 12.058 +31 13 02.05           ~ 582 0
6 V* DM Tau Or* 04 33 48.7336763736 +18 10 09.973460280 14.30 14.82 14.00     M2Ve 579 0
7 EM* LkCa 15 Or* 04 39 17.7911622816 +22 21 03.390090984   13.01 12.03 11.61   K5:Ve 612 1
8 TMC-1 MoC 04 41 45.9 +25 41 27           ~ 1520 0
9 RAFGL 618 pA* 04 42 53.6242032600 +36 06 53.400902220   16.32   12.59   C-rich 981 0
10 HD 31648 Ae* 04 58 46.2655706952 +29 50 36.987625680 7.84 7.78 7.62 7.76 7.43 A5Vep 458 0
11 NAME OMC-1 MoC 05 35 14 -05 22.4           ~ 1103 2
12 NAME Orion Bright Bar reg 05 35 22.30 -05 24 33.0           ~ 797 0
13 NAME NGC 2071 IR SFR 05 47 04.4 +00 21 49           ~ 66 0
14 IRC +10216 C* 09 47 57.40632 +13 16 43.5648     10.96     C9,5e 2239 0
15 V* TW Hya TT* 11 01 51.9053285064 -34 42 17.033218380   11.94 10.50 10.626 9.18 K6Ve 1735 1
16 CRBR 2422.8-3423 Y*O 16 27 24.61320 -24 41 03.4080           ~ 86 1
17 IRAS 16293-2422 cor 16 32 22.56 -24 28 31.8           ~ 1158 1
18 NAME NGC 6334-I Cl* 17 20 53.35 -35 47 01.5           ~ 307 0
19 HD 163296 Ae* 17 56 21.2881851168 -21 57 21.871819008 7.00 6.93 6.85 6.86 6.67 A1Vep 953 0
20 OH 34.26 +0.15 SFR 18 53 18.54 +01 14 57.9           ~ 482 0

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2022.05.21-14:39:37

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