thesis - IRS, The Infrared Spectrograph

4.5. The visual and the ultraviolet spectrum 57Table 4.5–. Ultraviolet (IUE) and optical line fluxes in units of 10 −12 erg cm −2 s −1 for BD+30 3639.The optical lines are from Aller & Hyung (1995).λ (nm) Ident. Flux obs Flux corr λ (nm) Ident. Flux obs Flux corr190.9 † C III] 1.76 21.7 551.8 [Cl III] 0.12 0.31232.6 ⋆ C II 19.7 292.5 553.8 [Cl III] 0.37 0.97372.6 [O II] 98.8 417.3 575.4 [N II] 5.15 12.89372.9 [O II] 40.2 169.6 587.6 He I 4.06 9.94406.9 [S II] 6.04 23.6 630.0 [O I] 1.88 4.30407.6 [S II] 1.62 6.31 631.2 [S III] 1.32 3.01447.1 He I 0.77 2.73 636.3 [O I] 0.71 1.61486.1 ♯ H β 93.3 293.9 658.3 [N II] 457.0 1002.9493.3 [O III] 0.06 0.18 671.6 [S II] 5.18 11.12495.9 [O III] 2.09 6.39 673.1 [S II] 11.17 24.0519.9 [N I] 0.24 0.68 858.1 [Cl II] 1.01 1.68520.1 [N I] 0.18 0.51 912.6 [Cl II] 0.27 0.43† From the IUE observations (see Sect. 4.2.2).⋆ Taken from Torres-Peimbert & Peña (1981).♯ From Acker et al. (1992).4.4.2 NGC 6543In Table 4.4 the twenty one lines measured with SWS are tabulated. Upper limits for [Mg IV]at 4.49 µm and [O IV] at 25.9 µm were also derived. Three LWS lines were also used.The strongest lines correspond to [Ne III] and [S IV]. [Si II], although faint, is also clearlydetected.It is not possible to derive the extinction in the same way as for BD+30 3639 becausethe hydrogen lines have been measured with the smallest aperture, which as discussed inSect. 4.3, may miss some nebular flux. The expected H β can be found from the 6 cm radioemission using the following equation:F (H β ) =(4.1)2.82 × 10 9 t 0.53 (1 + He+H+ 3.7 He+++ H) +In this equation the flux density S ν =0.873 Jy at 5 GHz (George et al. 1974), t is theelectron temperature in units of 10 4 K (0.82 for this nebula) and 2.82 × 10 9 is a conversionfactor to give the F (H β ) in erg cm −2 s −1 . The helium abundances used in this calculationare those of Table 4.10. The predicted H β flux is then 307.8 × 10 −12 erg cm −2 s −1 . Themeasured H β flux by Acker et al. (1992) is 245.5 × 10 −12 erg cm −2 s −1 . This leads toC Hβ =0.1 or E B−V =0.07 which we shall use in the remainder of this paper.4.5 The visual and the ultraviolet spectrumOptical and ultraviolet lines have been used to provide more information on ionization stagesof some ions, especially carbon, oxygen and nitrogen.S ν