2010A&A...511A..32B


Query : 2010A&A...511A..32B

2010A&A...511A..32B - Astronomy and Astrophysics, volume 511, A32-32 (2010/2-2)

The 15-20 µm PAH emission features: probes of individual PAHs?.

BOERSMA C., BAUSCHLICHER C.W.Jr, ALLAMANDOLA L.J., RICCA A., PEETERS E. and TIELENS A.G.G.M.

Abstract (from CDS):

Spectral features between about 15-20µm are commonly associated with polycyclic aromatic hydrocarbons (PAHs). With the NASA Spitzer Space Telescope these features are reported routinely, and as such, warrant a deeper molecular explanation. We aim to determine the characteristics of the group of carriers of the plateau and the distinct sub-features at 15.8, 16.4, 17.4, 17.8 and 18.9µm and to draw astronomical implications from these spectra. We analyse and interpret the spectra of 15 different sources using the NASA Ames PAH IR spectroscopic database. The bands within the 15-20µm region show large variations. Except for the 16.4µm band, there is also no connection, both in band strength and feature classification, with the mid-IR PAH bands. Of the PAH spectra considered, only those from species containing pendent rings show one ``common'' characteristic: a band near the astronomical 16.4µm position. However, coupling with the carbon skeleton's core influences its precise position in the spectrum. Compact PAHs in the size range 50-130 carbon atoms, consistently show a strong band near the astronomical 17.4µm band position. The 15-20µm region is the transition zone from PAH nearest neighbour modes to full-skeleton modes. We conclude that a few individual PAHs dominate the astronomical PAH family when clear features are prominent. In the few cases of a broad plateau, the PAH family would be far richer. Although PAHs containing pendent rings showed promise explaining the astronomical 16.4µm band, coupling with the skeleton core and the inherent strong quartet mode expected around 13.5µm, make it a less viable candidate. The number of large PAHs in the database becomes a limitation in studying the emission between 15-20µm and longward. Computation of larger PAH spectra should therefore be stimulated, especially for understanding the forthcoming far-IR data expected from Herschel, SOFIA and ALMA.

Abstract Copyright:

Journal keyword(s): astrochemistry - molecular data - techniques: spectroscopic - infrared: general

Simbad objects: 18

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Number of rows : 18
N Identifier Otype ICRS (J2000)
RA
ICRS (J2000)
DEC
Mag U Mag B Mag V Mag R Mag I Sp type #ref
1850 - 2023
#notes
1 LHA 120-N 107 PN 05 10 39.6656702832 -68 36 04.807039644 18.464 17.490 16.179 16.33 17.210 ~ 32 0
2 2MASS J05112369-7001573 pA? 05 11 23.692 -70 01 57.36 15.971 16.222 15.008 15.53 16.678 ~ 39 0
3 IRAS F05258-7343 pA? 05 24 35.9730395808 -73 40 40.240094808   16.48     16.64 WC 59 0
4 HD 36917 Or* 05 34 46.9822530528 -05 34 14.583314568   8.13 8.03     B9III/IV 145 0
5 [GSL2002] 18 HII 05 35 19.8 -05 25 10           ~ 6 0
6 Ass Ori OB 1c As* 05 35 21 -05 20.5           ~ 132 1
7 [VPT2002] Orion Bar 1 HII 05 35 21.4 -05 25 40           ~ 3 0
8 HD 37411 Or* 05 38 14.5072831944 -05 25 13.301118588 10.03 9.91 9.79 9.60 9.45 hA3VakA0mA0(eb)_lB 88 0
9 NGC 2023 RNe 05 41 37.9 -02 15 52           ~ 610 1
10 HD 37903 Em* 05 41 38.3891026008 -02 15 32.479650720 7.32 7.94 7.83 7.64 7.52 B3IV 342 1
11 HD 44179 pA* 06 19 58.2185496 -10 38 14.706068 9.51 9.33 9.02     B9Ib/II 742 0
12 ESO 95-1 HII 12 09 01.260 -63 15 59.63     16.00     ~ 93 2
13 M 94 SyG 12 50 53.0737971432 +41 07 12.900884628 9.15 8.96 8.24 7.78   ~ 1323 2
14 NGC 4735 SBG 12 51 01.7242741800 +28 55 40.705278132   15.10 14.42     ~ 66 0
15 NGC 6567 PN 18 13 45.1636643352 -19 04 34.071637152     10.9     [WC5/6] 268 1
16 PN Cn 1-5 PN 18 29 11.6500996872 -31 29 59.135208396   15.5 15.2 13.34   [WC5/6] 147 0
17 NGC 7023 RNe 21 01 36.9 +68 09 48           ~ 678 0
18 HD 200775 Ae* 21 01 36.9205762896 +68 09 47.789578836 7.34 7.754 7.427 8.13   B2Ve 536 0

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2022.12.01-22:11:04

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