Theoretical He i line intensities in low-density plasmas

Smits, Derck P.

doi:10.1093/mnras/278.3.683

Cited by 127 publications

(160 citation statements)

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“…We take 2 × 10 −5 as a conservative lower limit on D/H. This value agrees with the pre-solar system deuterium abundance inferred from 3 He (Gloeckler & Geiss 1998) Smits (1996) and Blocklehurst (1972). The helium abundances derived from three recombination lines He I λ4471, λ5876 and λ6678 for a given HII region differ fractionally by a few percent.…”

Section: Nucleosynthesissupporting

confidence: 73%

CMB Observables and Their Cosmological Implications 2002

Hu¹

2003

AIP Conference Proceedings

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We show that recent measurements of the power spectrum of cosmic microwave background anisotropies by BOOMERanG and MAXIMA can be characterized by four observables, the position of the first acoustic peak 1 = 206 ± 6, the height of the first peak relative to COBE normalization H 1 = 7.6 ± 1.4, the height of the second peak relative to the first H 2 = 0.38 ± 0.04, and the height of the third peak relative to the first H 3 = 0.43 ± 0.07. This phenomenological representation of the measurements complements more detailed likelihood analyses in multidimensional parameter space, clarifying the dependence on prior assumptions and the specific aspects of the data leading to the constraints. We illustrate their use in the flat ΛCDM family of models where we find Ω m h 3.8 > 0.079 (or nearly equivalently, the age of the universe t 0 < 13 − 14Gyr) from 1 and a baryon density Ω b h 2 > 0.019, a matter density Ω m h 2 < 0.42 and tilt n > 0.85 from the peak heights (95% CL). With the aid of several external constraints, notably nucleosynthesis, the age of the universe and the cluster abundance and baryon fraction, we construct the allowed region in the (Ω m ,h) plane; it points to high h (0.6 < h < 0.9) and moderate Ω m (0.25 < Ω m < 0.6).

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Section: Nucleosynthesissupporting

confidence: 73%

CMB Observables and Their Cosmological Implications 2002

Hu¹

2003

AIP Conference Proceedings

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“…The recombination coefficients used were those by Storey & Hummer (1995) for H and those by Smits (1996) and Benjamin, Skillman, & Smits (1999) for He. Thecollisional contribution was estimated from Sawey & Berrington (1993) and Kingdon & Ferland (1995).…”

Section: Helium Ionic Abundancesmentioning

confidence: 99%

The Chemical Composition of the 30 Doradus Nebula Derived from Very Large Telescope Echelle Spectrophotometry

Peimbert¹

2003

ApJ

133

182

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“…As in Liu et al (2000), the He + /H + abundance was calculated from the average λ4471, λ5876, and λ6678 individual line abundances, weighted 1:3:1, using the tabulated emissivites of Smits (1996) at T e =10000 K and N e =10000 cm −3 . Line intensities were corrected for electron collisional excitations from the He o 2s 3 S metastable term by the formalism of Kingdon & Ferland (1995) using T e =9600 K and N e =10000 cm −3 .…”

Section: Permitted Lines From Other Ionsmentioning

confidence: 99%

Identification and Characterization of Faint Emission Lines in the Spectrum of the Planetary Nebula IC 418

Sharpee¹,

Baldwin²,

Williams³

2004

ApJ

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We present high signal-to-noise echelle spectra of the compact high surface brightness, low ionization planetary nebula IC 418. These reveal 807 emission lines down to intensities less than 10 −5 that of Hβ for which we determine widths and relative intensities. We show that line profiles are a valuable parameter for making line identifications and in constraining the excitation mechanism of the lines. We present evidence that indicates that many supposed high-level recombination lines may in fact be excited by a process other than recombination. We contend from the detection of dielectronic recombination lines that their relatively low intensities argue against their making a significant contribution to level populations of the heavy ions in this object. Following similar analyses of other PNe we find that IC 418 shows a small discrepancy in ion abundances derived from forbidden vs. recombination lines of the heavy elements.

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Theoretical He i line intensities in low-density plasmas

Cited by 127 publications

References 0 publications

CMB Observables and Their Cosmological Implications 2002

CMB Observables and Their Cosmological Implications 2002

The Chemical Composition of the 30 Doradus Nebula Derived from Very Large Telescope Echelle Spectrophotometry

Identification and Characterization of Faint Emission Lines in the Spectrum of the Planetary Nebula IC 418

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