The Discovery of Raman Lines in NGC 7027

Pequignot, D.; Baluteau, J. P.; Boisson, C.; Morisset, Charles

doi:10.1007/978-94-011-5244-0_48

Cited by 184 publications

(268 citation statements)

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“…We detect several N iv in the spectrum of NGC 3918, but only a handful of them have available recombination coefficients (Péquignot et al 1991). These lines give relatively similar results for the N 4+ /H + ratio and most of them are transitions between high levels and, therefore, are probably excited by pure recombination.…”

Section: N Orlsmentioning

confidence: 95%

s-process enrichment in the planetary nebula NGC 3918. Results from deep echelle spectrophotometry

García‐Rojas¹,

Madonna²,

Luridiana³

et al. 2015

Mon. Not. R. Astron. Soc.

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The chemical content of the planetary nebula NGC 3918 is investigated through deep, highresolution (R∼40000) UVES at VLT spectrophotometric data. We identify and measure more than 750 emission lines, making ours one of the deepest spectra ever taken for a planetary nebula. Among these lines we detect very faint lines of several neutron-capture elements (Se, Kr, Rb, and Xe), which enable us to compute their chemical abundances with unprecedented accuracy, thus constraining the efficiency of the s-process and convective dredge-up in NGC 3918s progenitor star. We find that Kr is strongly enriched in NGC 3918 and that Se is less enriched than Kr, in agreement with the results of previous papers and with predicted s-process nucleosynthesis. We also find that Xe is not as enriched by the s-process in NGC 3918 as is Kr and, therefore, that neutron exposure is typical of modestly subsolar metallicity AGB stars. A clear correlation is found when representing [Kr/O] vs. log(C/O) for NGC 3918 and other objects with detection of multiple ions of Kr in optical data, confirming that carbon is brought to the surface of AGB stars along with s-processed material during third dredge-up episodes, as predicted by nucleosynthesis models. We also detect numerous refractory element lines (Ca, K, Cr, Mn, Fe, Co, Ni, and Cu) and a large number of metal recombination lines of C, N, O, and Ne. We compute physical conditions from a large number of diagnostics, which are highly consistent among themselves assuming a three-zone ionization scheme. Thanks to the high ionization of NGC 3918 we detect a large number of recombination lines of multiple ionization stages of C, N, O and Ne. The abundances obtained for these elements by using recently-determined state-of-the-art ICF schemes or simply adding ionic abundances are in very good agreement, demonstrating the quality of the recent ICF scheme for high ionization planetary nebulae.

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Section: N Orlsmentioning

confidence: 95%

s-process enrichment in the planetary nebula NGC 3918. Results from deep echelle spectrophotometry

García‐Rojas¹,

Madonna²,

Luridiana³

et al. 2015

Mon. Not. R. Astron. Soc.

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“…We checked that the calculated rates summed over n ≥ 2 and l, added to the rate of the 1s 2 (ground level) level, are similar to the total RR rates calculated by Arnaud & Rothenflug (1985), Pequignot et al (1991), Mazzotta et al (1998), Jacobs et al (1977) (for He-like Fe ion) and Nahar (1999) (for O vii). Since these authors used hydrogenic formulae, the RR rate coefficient depends on which screening value was used.…”

Section: Radiative Recombination (Rr) Coefficients Ratesmentioning

confidence: 96%

X-ray photoionized plasma diagnostics with helium-like ions. Application to warm absorber-emitter in active galactic nuclei

Porquet

Dubau

2000

Astron. Astrophys. Suppl. Ser.

314

435

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Abstract. We present He-like line ratios (resonance, intercombination and forbidden lines) for totally and partially photoionized media. For solar plasmas, these line ratios are already widely used for density and temperature diagnostics of coronal (collisional) plasmas. In the case of totally and partially photoionized plasmas, He-like line ratios allow for the determination of the ionization processes involved in the plasma (photoionization with or without an additional collisional ionization process), as well as the density and the electronic temperature.With the new generation of X-ray satellites, Chandra/AXAF, XMM and Astro-E, it will be feasible to obtain both high spectral resolution and high sensitivity observations. Thus in the coming years, the ratios of these three components will be measurable for a large number of non-solar objects.In particular, these ratios could be applied to the Warm Absorber-Emitter, commonly present in Active Galactic Nuclei (AGN). A better understanding of the Warm Absorber connection to other regions (Broad Line Region, Narrow Line Region) in AGN (Seyferts type-1 and type-2, low-and high-redshift quasars...) will be an important key to obtaining strong constraints on unified schemes.We have calculated He-like line ratios, for Z = 6, 7, 8, 10, 12 and 14, taking into account the upper level radiative cascades which we have computed for radiative and dielectronic recombinations and collisional excitation. The atomic data are tabulated over a wide range of temperatures in order to be used for interpreting a large variety of astrophysical plasmas.

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“…1 + 2 in SBS 0335-052E (Table 4). Adopting radiative recombination coefficients from Péquignot et al (1991), we obtained a O 2+ /H + abundance ratio of (1.50 ± 0.75) × 10 −5 from the recombination line flux. This value is consistent with that derived from the forbidden lines (Table 6).…”

Section: Electron Temperature and Electron Number Densitymentioning

confidence: 99%

SBS 0335-052E+W: deep VLT/FORS+UVES spectroscopy of the pair of the lowest-metallicity blue compact dwarf galaxies

Izotov

Гусева

Fricke

et al. 2009

A&A

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Context. We present deep archival VLT/FORS1+UVES spectroscopic observations of the system of two blue compact dwarf (BCD) galaxies SBS 0335-052E and SBS 0335-052W.Aims. Our aim is to derive element abundances in different H ii regions of this unique system of galaxies and to study spatial abundance variations.Methods. The electron temperature T e (O iii) in all H ii regions, except for one, is derived from the [O iii] λ4363/(λ4959+λ5007) flux ratio. We determine ionic abundances of helium, nitrogen, oxygen, neon, sulfur, chlorine, argon and iron. The empirical relations for ionization correction factors are used to derive total abundances of these elements.Results. The oxygen abundance in the brighter eastern galaxy varies in the range 7.11 to 7.32 in different H ii regions supporting previous findings and suggesting the presence of oxygen abundance variations on spatial scales of ∼1−2 kpc. Good seeing during FORS observations allowed us to extract spectra of four H ii regions in SBS 0335-052W. The oxygen abundance in the brightest region No. 1 of SBS 0335-052W is 7.22 ± 0.07, consistent with previous determinations. Three other H ii regions are much more metal-poor with an unprecedently low oxygen abundance of 12 + log O/H = 7.01 ± 0.07 (region No. 2), 6.98 ± 0.06 (region No. 3), and 6.86 ± 0.14 (region No. 4). These are the lowest oxygen abundances ever derived in emission-line galaxies, supporting earlier conclusions that SBS 0335-052W is the lowest-metallicity emission-line galaxy known. Helium abundances derived for the brightest H ii regions of both galaxies are mutually consistent. We derive weighted mean He mass fractions of 0.2485 ± 0.0012 and 0.2514 ± 0.0012 for two different sets of He i emissivities. The ratios of neon and sulfur to oxygen abundance are similar to the respective ratios obtained for other emission-line galaxies. On the other hand, the chlorine-to-oxygen abundance ratio in SBS 0335-052E is lower, while the argon-to-oxygen abundance ratio is higher than those in other low-metallicity galaxies. The Fe/O abundance ratios in different regions of SBS 0335-052E are among the highest for emission-line galaxies implying that iron is almost entirely not depleted onto dust grains despite dust being detected in this galaxy in earlier ISO and Spitzer observations. The N/O abundance ratio in both galaxies is slightly higher than that derived for other BCDs with 12 + log O/H < 7.6. This implies that the N/O in extremely metal-deficient galaxies could increase with decreasing metallicity.

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The Discovery of Raman Lines in NGC 7027

Cited by 184 publications

References 1 publication

s-process enrichment in the planetary nebula NGC 3918. Results from deep echelle spectrophotometry

s-process enrichment in the planetary nebula NGC 3918. Results from deep echelle spectrophotometry

X-ray photoionized plasma diagnostics with helium-like ions. Application to warm absorber-emitter in active galactic nuclei

SBS 0335-052E+W: deep VLT/FORS+UVES spectroscopy of the pair of the lowest-metallicity blue compact dwarf galaxies

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