2008ApJ...680..384W


C.D.S. - SIMBAD4 rel 1.7 - 2021.06.21CEST06:03:04

2008ApJ...680..384W - Astrophys. J., 680, 384-397 (2008/June-2)

Chemical rates on small grains and PAHs: c+ recombination and H2Formation.

WOLFIRE M.G., TIELENS A.G.G.M., HOLLENBACH D. and KAUFMAN M.J.

Abstract (from CDS):

We use observations of the C I, C II, H I, and H2 column densities along lines of sight in the Galactic plane to determine the formation rate of H2 on grains and to determine chemical reaction rates with polycyclic aromatic hydrocarbons (PAHs). Photodissociation region models are used to find the best-fit parameters to the observed columns. We find the H2formation rate on grains has a low rate (R∼1x10–17 cm3/s) along lines of sight with low column density (AV≲0.25) and low molecular fraction (fH2≲10–4). At higher column densities (0.25≤AV≤2.13), we find a rate of R∼3.5x10–17 cm3/s. The lower rate at low column densities could be the result of grain processing by interstellar shocks, which may deplete the grain surface area or process the sites of H+H formation, thereby inhibiting H2production. Alternatively, the formation rate may be normal, and the low molecular fraction may be the result of lines of sight that graze larger clouds. Such lines of sight would have a reduced H2self-shielding compared to the line-of-sight column. We find the reaction C++PAH⟶C+PAH0 is best fit with a rate 2.4x10–7ΦPAHT–0.52cm3/s with T2=T/100 K, and the reaction C++PAH0⟶C+PAH+ is best fit with a rate 8.8x10–9ΦPAHcm3/s. In high-column-density gas, we find ΦPAH∼0.4. In low-column-density gas, ΦPAH is less well constrained, with ΦPAH∼0.2-0.4.

Abstract Copyright:

Journal keyword(s): Astrochemistry - ISM: Clouds - ISM: General - ISM: Molecules

Simbad objects: 47

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Number of rows : 47

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 * kap Cas s*b 00 32 59.9911963 +62 55 54.417374 3.50 4.30 4.16 4.02 3.96 B1Ia 451 0
2 NAME SMC G 00 52 38.0 -72 48 01   2.79 2.2     ~ 9841 1
3 * chi Per * 02 18 04.5844857610 +57 30 58.757945030   7.036 6.0230     G7.0III 163 1
4 * o Per * 03 42 22.6455526 +33 57 54.089323 4.13 4.912 4.972     B0.5V 283 0
5 * omi Per ** 03 44 19.13204 +32 17 17.6929 3.13 3.88 3.83 3.71 3.71 B1III 578 0
6 * zet Per V* 03 54 07.9224751 +31 53 01.081262 2.19 2.97 2.85 2.71 2.62 B1Ib 820 0
7 V* X Per HXB 03 55 23.0778791365 +31 02 45.045745259 6.090 6.840 6.720     O9.5III 923 0
8 * eps Per bC* 03 57 51.2320472 +40 00 36.775143 1.71 2.71 2.89 2.96 3.14 B1.5III 498 0
9 * ksi Per ** 03 58 57.9022917 +35 47 27.713205 3.190 4.080 4.060 3.88 3.89 O7.5III(n)((f)) 799 0
10 V* AE Aur Or* 05 16 18.1489437436 +34 18 44.347016027 5.48 6.18 5.96     O9.5V 534 1
11 * 23 Ori SB* 05 22 50.0047401166 +03 32 39.976975214 3.99 4.86 5.00 5.05 5.23 B2IV/V 234 0
12 NAME LMC G 05 23 34.6 -69 45 22     0.4     ~ 15432 1
13 * del Ori EB* 05 32 00.40009 -00 17 56.7424 0.96 2.02 2.41 2.32 2.54 B0III+O9V 751 0
14 * lam Ori A Em* 05 35 08.2792540686 +09 56 02.955355445 2.17 3.48 3.47     O8III((f)) 490 0
15 * iot Ori SB* 05 35 25.9819073 -05 54 35.643537 1.45 2.53 2.77     O9IIIvar 739 0
16 * eps Ori s*b 05 36 12.81335 -01 12 06.9089 0.48 1.51 1.69 1.76 1.93 B0Ia 868 0
17 * zet Ori ** 05 40 45.52666 -01 56 33.2649 0.50 1.56 1.77 1.85 2.05 O9.7Ib+B0III 335 0
18 * zet Ori A SB* 05 40 45.527143 -01 56 33.26036   1.79 1.90     O9.2IbvarNwk 650 0
19 * mu. Col V* 05 45 59.8953630749 -32 18 23.164726112 3.84 4.90 5.18 5.30 5.57 O9.5V 466 0
20 * kap Ori s*b 05 47 45.3888404 -09 40 10.577707 0.87 1.88 2.06 2.09 2.27 B0.5Ia 551 0
21 * 139 Tau Em* 05 57 59.6563212 +25 57 14.079839 3.82 4.76 4.82 4.76 4.87 B0/1II/III 270 0
22 * 15 Mon Be* 06 40 58.65963 +09 53 44.7229 3.360 4.400 4.640   4.88 O7V+B1.5/2V 761 0
23 * zet Pup BY* 08 03 35.04754 -40 00 11.3321 0.89 1.98 2.25 2.36 2.58 O4I(n)fp 1112 1
24 * gam02 Vel WR* 08 09 31.95013 -47 20 11.7108 0.64 1.58 1.83 1.85 2.00 WC8+O7.5III-V 855 0
25 * rho Leo s*b 10 32 48.6716770 +09 18 23.709445 2.780 3.720 3.870 3.90 4.06 B1Iab 514 0
26 HD 112244 s*b 12 55 57.1346044550 -56 50 08.891958192 4.49 5.33 5.32 5.21 5.21 O8.5Iab(f)p 198 0
27 * b Sco * 15 50 58.7451174285 -25 45 04.662754169 3.84 4.552 4.635     B1.5Vn 274 0
28 * pi. Sco EB* 15 58 51.1132378 -26 06 50.788602 1.82 2.71 2.91 3.00 3.20 B1V+B2:V: 379 0
29 * del Sco SB* 16 00 20.00528 -22 37 18.1431 1.30 2.20 2.32 2.36 2.49 B0.3IV 703 0
30 * bet01 Sco SB* 16 05 26.2319826 -19 48 19.630018 1.68 2.55 2.62 2.60 2.69 B1V 538 0
31 * ome Sco bC* 16 06 48.4269211 -20 40 09.090235 3.10 3.92 3.97 3.91 3.99 B1V 447 0
32 * nu. Sco ** 16 11 59.73568 -19 27 38.5361 3.42 4.05 4.00 3.90 3.87 B2V 361 0
33 * sig Sco bC* 16 21 11.3157134 -25 35 34.051476 2.32 3.02 2.89 1.69 1.58 O9.5(V)+B7(V) 835 0
34 * rho Oph ** 16 25 35.11766 -23 26 49.8150 4.30 4.85 4.63 4.27 3.96 B2IV+B2V 620 0
35 * rho Oph A * 16 25 35.1182364594 -23 26 49.827436721 4.3 5.22 5.05     B2/3V 399 0
36 * chi Oph Be* 16 27 01.4349892 -18 27 22.493784 3.95 4.71 4.43 3.97 3.73 B2Vne 572 0
37 * i Sco * 16 30 12.4751393 -25 06 54.804270 3.93 4.72 4.79 4.85 4.99 B3V 287 1
38 * zet Oph Be* 16 37 09.5390545 -10 34 01.529471 1.73 2.58 2.56 2.46 2.50 O9.2IVnn 1755 2
39 HD 154368 s*b 17 06 28.3687923960 -35 27 03.759955171 6.10 6.63 6.13 7.12   O9.5Iab 273 0
40 * gam Ara Be* 17 25 23.6593111 -56 22 39.814775 2.25 3.21 3.34     B1Ib 258 0
41 * kap Aql * 19 36 53.4495162 -07 01 38.917563 4.050 4.930 4.960 4.90 4.94 B0.5IIIn 327 0
42 HD 185418 * 19 38 27.4810594267 +17 15 26.046198639 7 7.639 7.485     B0.5V 122 0
43 HD 192639 s*b 20 14 30.4275040181 +37 21 13.815126140 6.83 7.46 7.11     O7.5Iabf 274 0
44 * f01 Cyg Be* 20 59 49.5516391039 +47 31 15.378902421 3.77 4.71 4.75 4.62 4.63 B1.5Vnne 471 0
45 HD 206267 SB* 21 38 57.6182747705 +57 29 20.557311013 5.09 5.83 5.62   5.56 O6.0V((f))+O9:V 458 0
46 * lam Cep s*b 22 11 30.5750839949 +59 24 52.147736074 4.55 5.29 5.05 4.77 4.62 O6.5I(n)fp 654 1
47 * sig Cas ** 23 59 00.53819 +55 45 17.7430           B1V 144 0

    Equat.    Gal    SGal    Ecl

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2021.06.21-06:03:04

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