The chemical composition of Galactic ring nebulae around massive stars

Esteban, C.; Mesa‐Delgado, A.; Morisset, Charles; García‐Rojas, J.

doi:10.1093/mnras/stw1243

Cited by 31 publications

(53 citation statements)

References 84 publications

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“…The abundances for NGC 6888 given in Table A1 come from the most recent deep spectral study of this object by Esteban et al (2016). There is enhanced He and N in this object, normal C abundance and some evidence of O deficiency, compared to solar.…”

Section: Wolf-rayet Nebulaementioning

confidence: 99%

On the X-ray temperature of hot gas in diffuse nebulae

Toalá¹,

Arthur²

2018

Monthly Notices of the Royal Astronomical Society

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X-ray emitting diffuse nebulae around hot stars are observed to have soft-band temperatures in the narrow range [1-3]×10 6 K, independent of the stellar wind parameters and the evolutionary stage of the central star. We discuss the origin of this X-ray temperature for planetary nebulae (PNe), Wolf-Rayet nebulae (WR) and interstellar wind bubbles around hot young stars in our Galaxy and the Magellanic Clouds. We calculate the differential emission measure (DEM) distributions as a function of temperature from previously published simulations and combine these with the X-ray emission coefficient for the 0.3-2.0 keV band to estimate the X-ray temperatures. We find that all simulated nebulae have DEM distributions with steep negative slopes, which is due to turbulent mixing at the interface between the hot shocked stellar wind and the warm photoionized gas. Sharply peaked emission coefficients act as temperature filters and emphasize the contribution of gas with temperatures close to the peak position, which coincides with the observed X-ray temperatures for the chemical abundance sets we consider. Higher metallicity nebulae have lower temperature and higher luminosity X-ray emission. We show that the second temperature component found from spectral fitting to X-ray observations of WR nebulae is due to a significant contribution from the hot shocked stellar wind, while the lower temperature principal component is dominated by nebular gas. We suggest that turbulent mixing layers are the origin of the soft X-ray emission in the majority of diffuse nebulae.

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Section: Wolf-rayet Nebulaementioning

confidence: 99%

On the X-ray temperature of hot gas in diffuse nebulae

Toalá¹,

Arthur²

2018

Monthly Notices of the Royal Astronomical Society

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“…4). Esteban et al (2016) speculate that large ADFs in H ii regions might be produced by the presence of shocks due to large-scale interaction of stellar winds with the ionized gas that may dominate the kinematics of these complex and huge nebulae. This suggestion is based on the results obtained by Esteban et al (2016) Fig.…”

Section: Adf(o 2+mentioning

confidence: 99%

“…Esteban et al (2016) speculate that large ADFs in H ii regions might be produced by the presence of shocks due to large-scale interaction of stellar winds with the ionized gas that may dominate the kinematics of these complex and huge nebulae. This suggestion is based on the results obtained by Esteban et al (2016) Fig. 5 contains the ADF(C 2+ ) as a function of the total O abundances determined from CELs and RLs (left and right panel, respectively) for the H ii regions where we have determinations of C 2+ abundances from CELs available from the literature.…”

Section: Adf(o 2+mentioning

confidence: 99%

Carbon and oxygen in H ii regions of the Magellanic Clouds: abundance discrepancy and chemical evolution

Cipriano

Domínguez-Guzmán

Esteban

et al. 2017

Monthly Notices of the Royal Astronomical Society

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We present C and O abundances in the Magellanic Clouds derived from deep spectra of H ii regions. The data have been taken with the Ultraviolet-Visual Echelle Spectrograph at the 8.2-m VLT. The sample comprises 5 H ii regions in the Large Magellanic Cloud (LMC) and 4 in the Small Magellanic Cloud (SMC). We measure pure recombination lines (RLs) of C ii and O ii in all the objects, permitting to derive the abundance discrepancy factors (ADFs) for O 2+ , as well as their O/H, C/H and C/O ratios. We compare the ADFs with those of other H ii regions in different galaxies. The results suggest a possible metallicity dependence of the ADF for the low-metallicity objects; but more uncertain for high-metallicity objects. We compare nebular and Btype stellar abundances and we find that the stellar abundances agree better with the nebular ones derived from collisionally excited lines (CELs). Comparing these results with other galaxies we observe that stellar abundances seem to agree better with the nebular ones derived from CELs in low-metallicity environments and from RLs in high-metallicity environments. The C/H, O/H and C/O ratios show almost flat radial gradients, in contrast with the spiral galaxies where such gradients are negative. We explore the chemical evolution analysing C/O vs. O/H and comparing with the results of H ii regions in other galaxies. The LMC seems to show a similar chemical evolution to the external zones of small spiral galaxies and the SMC behaves as a typical star-forming dwarf galaxy.

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“…One can also try to find the set of models that fit the observables within a certain tolerance, which naturally gives us the uncertainties in parameter determination. This has been done for example by Esteban et al (2016) …”

Section: Abundance Determinationsmentioning

confidence: 99%