The chemical composition of Galactic ring nebulae around massive stars

Abstract

We present deep spectra of ring nebulae associated with Wolf-Rayet (WR) and O-type stars: NGC 6888, G2.4+1.4, RCW 58, S 308, NGC 7635 and RCW 52. The data have been taken with the 10m Gran Telescopio Canarias and the 6.5m Clay Telescope. We extract spectra of several apertures in some of the objects. We derive C${}^{++}$ and O${}^{++}$ abundances from faint recombination lines in NGC 6888 and NGC 7635, permitting to derive their C/H and C/O ratios and estimate the abundance discrepancy factor (ADF) of O${}^{++}$. The ADFs are larger than the typical ones of normal HII regions but similar to those found in the ionised gas of star-forming dwarf galaxies. We find that chemical abundances are rather homogeneous in the nebulae where we have spectra of several apertures: NGC 6888, NGC 7635 and G2.4+1.4. We obtain very high values of electron temperature in a peripheral zone of NGC 6888, finding that shock excitation can reproduce its spectral properties. We find that all the objects associated with WR stars show N enrichment. Some of them also show He enrichment and O deficiency as well as a lower Ne/O than expected, this may indicate the strong action of the ON and NeNa cycles. We have compared the chemical composition of NGC 6888, G2.4+1.4, RCW 58 and S 308 with the nucleosynthesis predicted by stellar evolution models of massive stars. We find that non-rotational models of stars of initial masses between 25 and 40 solar masses seem to reproduce the observed abundance ratios of most of the nebulae.

26 pages, 12 pages, 13 tables. Accepted for publication in Monthly Notices of the Royal Astronomical Society

References in corpus (12)

• The MAPPINGS III Library of Fast Radiative Shock Models
• PyNeb: a new tool for analyzing emission lines. I. Code description and validation of results
• The effect of massive binaries on stellar populations and supernova progenitors
• The Galactic WN stars: Spectral analyses with line-blanketed model atmospheres versus stellar evolution models with and without rotation
• The Galactic WC stars: Stellar parameters from spectral analyses indicate a new evolutionary sequence
• Resolving the electron temperature discrepancies in HII Regions and Planetary Nebulae: kappa-distributed electrons
• The MagE Spectrograph
• On the abundance discrepancy problem in HII regions
• Properties of the ionized gas in HH202. II: Results from echelle spectrophotometry with UVES
• Probing Wolf-Rayet Winds: Chandra/HETG X-Ray Spectra of WR 6
• Herschel observations of the nebula M1-67 around the Wolf-Rayet star WR 124
• Herschel-PACS Measurements of Nitrogen Enrichment in Nebulae around Wolf-Rayet Stars

Cited by in corpus (23)

• Nebular spectroscopy: A guide on H II regions and planetary nebulae
• Carbon and oxygen in HII regions of the Magellanic Clouds: abundance discrepancy and chemical evolution
• The radial abundance gradient of oxygen towards the Galactic anticentre
• Temperature inhomogeneities cause the abundance discrepancy in H II regions
• Density biases and temperature relations for DESIRED HII regions
• On the radial abundance gradients of nitrogen and oxygen in the inner Galactic disc
• The Te[N II]-Te[O III] temperature relation in H II regions and the reliability of strong-line methods
• On the X-ray temperature of hot gas in diffuse nebulae
• Thermal emission from bow shocks I: 2D Hydrodynamic Models of the Bubble Nebula
• Helium abundances and its radial gradient from the spectra of HII regions and ring nebulae of the Milky Way
• The last 5 Gyr of Galactic chemical evolution based on H II region abundances derived from a temperature independent method
• Gas-phase Fe/O and Fe/N abundances in Star-Forming Regions. Relations between nucleosynthesis, metallicity and dust
• On the bipolarity of Wolf-Rayet nebulae
• Unveiling the stellar origin of the Wolf-Rayet nebula NGC6888 through infrared observations
• Dust in the Wolf-Rayet Nebula M1-67
• Unveiling the nitrogen-rich massive star in the metal-poor galaxy NGC 4068
• Dust in RCW 58: clues to common envelope channel formation?
• Metallicity gradients in M31, M33, NGC 300 and the Milky Way using abundances of different elements
• Massive stars, successes and challenges
• Photoionization models of Planetary Nebulae
• Evidence for GeV Cosmic Rays from White Dwarfs in the Local Cosmic Ray Spectra and in the Gamma-ray Emissivity of the Inner Galaxy
• Realistic Models for Filling and Abundance Discrepancy Factors in Photoionised Nebulae
• The ADF and the t${}^2$ formalism in H II regions based on the upper mass limit of the IMF for the MW