2008A&A...484..241B


C.D.S. - SIMBAD4 rel 1.7 - 2021.03.05CET19:51:46

2008A&A...484..241B - Astronomy and Astrophysics, volume 484, 241-249 (2008/6-2)

The characteristics of the IR emission features in the spectra of Herbig Ae stars: evidence for chemical evolution.

BOERSMA C., BOUWMAN J., LAHUIS F., VAN KERCKHOVEN C., TIELENS A.G.G.M., WATERS L.B.F.M. and HENNING T.

Abstract (from CDS):

Infrared (IR) spectra provide a prime tool to study the characteristics of polycyclic aromatic hydrocarbon (PAH) molecules in regions of star formation. Herbig Ae/Be stars are a class of young pre-main sequence stellar objects of intermediate mass. They are known to have varying amounts of natal cloud material still present in their direct vicinity. We characterise the IR emission bands, due to fluorescence by PAH molecules, in the spectra of Herbig Ae/Be stars and link observed variations to spatial aspects of the mid-IR emission. We analysed two PAH dominated spectra from a sample of 15 Herbig Ae/Be stars observed with the Spitzer Space Telescope. We derived profiles of the major PAH bands by subtracting appropriate continua. The shape and the measured band characteristics show pronounced variations between the two Spitzer spectra investigated. Those variations parallel those found between three infrared space observatory (ISO) spectra of other, well-studied, Herbig Ae/Be stars. The derived profiles are compared to those from a broad sample of sources, including reflection nebulae, planetary nebulae, HII regions, young stellar objects, evolved stars and galaxies. The Spitzer and ISO spectra exhibit characteristics commonly interpreted respectively as interstellar matter-like (ISM), non-ISM-like, or a combination of the two. We argue that the PAH emission detected from the sources exhibiting a combination of ISM-like and non-ISM-like characteristics indicates the presence of two dissimilar, spatially separated, PAH families. As the shape of the individual PAH band profiles reflects the composition of the PAH molecules involved, this demonstrates that PAHs in subsequent, evolutionary linked stages of star formation are different from those in the general ISM, implying active chemistry. None of the detected PAH emission can be associated with the (unresolved) disk and is thus associated with the circumstellar (natal) cloud. This implies that chemical changes may already occur in the (collapsing?) natal cloud and not necessarily in the disk.

Abstract Copyright:

Journal keyword(s): stars: planetary systems: formation - infrared: stars - line: profiles - ISM: molecules

CDS comments: Paragraph.4 DC 292.6-7.9 is a probable misprint for DCld 296.2-07.9

Simbad objects: 27

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Number of rows : 27

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 HD 35929 dS* 05 27 42.7907337821 -08 19 38.446457813   8.55 8.11     F2IV/V 92 0
2 HD 36112 Ae* 05 30 27.5286772598 +25 19 57.082162439   8.57 8.27     A8Ve 382 0
3 HD 244604 Or* 05 31 57.2512002483 +11 17 41.374206174   9.61 9.43     A0Vesh 61 0
4 HD 36917 Or* 05 34 46.9833806135 -05 34 14.574708752   8.13 8.03     B9III/IV 137 0
5 Ass Ori OB 1c As* 05 35 21 -05 20.5           ~ 129 1
6 HD 37258 Ae* 05 36 59.2489032761 -06 09 16.317559872   9.72 9.61 9.56   A3Ve 117 0
7 HD 37357 Ae* 05 37 47.0795535305 -06 42 30.203876953   8.96 8.85     A1V 98 0
8 HD 37411 Or* 05 38 14.5075249942 -05 25 13.317577897 10.03 9.91 9.79 9.60 9.45 hA3VakA0mA0(eb)_lB 84 0
9 HD 37806 Be* 05 41 02.2930276072 -02 43 00.729083804 7.67 7.93 7.90     B9/9.5II/III 143 0
10 HD 38120 Be* 05 43 11.8931815256 -04 59 49.881886291 9.08 9.10 9.1     B9Vnne 76 0
11 HD 58647 Em* 07 25 56.0988044433 -14 10 43.548997982 6.81 6.92 6.85 6.73 6.73 B9IV 77 0
12 HD 72106 ** 08 29 34.89852 -38 36 21.1321       9.32   A0IV 64 0
13 HD 85567 Be* 09 50 28.5375203189 -60 58 02.950579275 8.16 8.67 8.57     B5Vne 81 0
14 HD 95881 Em* 11 01 57.6212785173 -71 30 48.313329972   8.37 8.23     A0 90 0
15 NAME Cha 1 MoC 11 06 48 -77 18.0           ~ 1011 1
16 NAME Cha T Association As* 11 08 -77.0           ~ 41 1
17 HD 97048 Ae* 11 08 03.3105687971 -77 39 17.491180130 9.03 8.76 9.00   8.64 A0Vep 467 0
18 BRAN 341B RNe 11 08 03.4 -77 39 19           ~ 27 0
19 DCld 296.2-07.9 DNe 11 32 47 -69 42.4           ~ 16 0
20 HD 100546 Be* 11 33 25.4404858122 -70 11 41.239343121   6.71 6.30   6.64 A0VaekB8_lB 669 1
21 HD 142527 Ae* 15 56 41.8888096574 -42 19 23.245384377   9.04 8.34     F6III 503 1
22 NGC 6726 RNe 19 01 38 -36 53.5           ~ 33 0
23 V* TY CrA Ae* 19 01 40.8312189956 -36 52 33.801844387 10.03 9.92 9.39     B9e 272 0
24 NAME CrA Complex reg 19 15 00.0 -37 30 00           ~ 102 1
25 HD 190073 Ae* 20 03 02.5098091524 +05 44 16.658081203 7.91 7.86 7.73   7.65 A2IVe 232 0
26 NGC 7027 PN 21 07 01.8 +42 14 10   9.1 10.9     ~ 2353 1
27 NAME Ori Belt reg ~ ~           ~ 69 0

    Equat.    Gal    SGal    Ecl

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2021.03.05-19:51:46

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