Some diffuse interstellar bands related to interstellar C2 molecules

被引:133
|
作者
Thorburn, JA
Hobbs, LM
McCall, BJ
Oka, T
Welty, DE
Friedman, SD
Snow, TP
Sonnentrucker, P
York, DG
机构
[1] Univ Chicago, Dept Astron & Astrophys, Chicago, IL 60037 USA
[2] Univ Calif Berkeley, Dept Astron, Berkeley, CA 94720 USA
[3] Johns Hopkins Univ, Dept Phys & Astron, Baltimore, MD 21218 USA
[4] Univ Colorado, Boulder, CO 80309 USA
来源
ASTROPHYSICAL JOURNAL | 2003年 / 584卷 / 01期
关键词
ISM : lines and bands; ISM : molecules;
D O I
10.1086/345665
中图分类号
P1 [天文学];
学科分类号
0704 ;
摘要
We have investigated the correlations between the equivalent widths of 21 selected diffuse interstellar bands (DIBs) and the corresponding interstellar column densities N(C-2), N(CN), and N(CH), toward 53 stars with color excesses 0.11less than or equal to E(B-V)less than or equal to1.99. The observational data were derived primarily from echelle spectra acquired at R=38,000 as part of our extensive, continuing survey of the bands. All but six of the 53 final spectra show signal-to-noise ratios greater than or equal to800 at 5780 Angstrom. The principal result presented here is that seven of the 21 bands prove to be examples of the C-2 DIBs, a class of weak, narrow bands whose normalized equivalent widths W-lambda(X)/W-lambda(lambda6196) are well correlated specifically with N(C-2)/E(B-V) via power laws. In contrast, the similarly normalized equivalent widths of the 14 other, well-known DIBs analyzed here are uncorrelated, or weakly anticorrelated, with N(C-2)/E(B-V), to within the observational uncertainties. Thus, the polyatomic molecule(s) presumed to cause these seven C-2 DIBs may bear a direct chemical relation to C-2 that is not shared by the polyatomic molecules putatively responsible for the other 14 bands. The C-2 DIBs also show positive correlations with N(CN)/E(B-V) and N(CH)/E(B-V) in our particular sample of light paths, although generally with shallower slopes in the case of N(CN) and with greater scatter in the case of N(CH). Eleven additional C-2 DIBs are also identified but are not analyzed here. Among the 18 C-2 DIBs identified, four apparently have not been previously detected. The lambda4963 band is generally the strongest of the 18 C-2 DIBs, while the lambda4734 band shows the most sensitive correlation with N(C-2).
引用
收藏
页码:339 / 356
页数:18
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