Red Supergiant Stars as Cosmic Abundance Probes: Kmos Observations in NGC 6822

Patrick, L. R.; Evans, C. J.; Davies, Ben; Kudritzki, R. P.; Gazak, J. Zachary; Bergemann, M.; Plez, B.; Ferguson, Annette M. N.

doi:10.1088/0004-637x/803/1/14

Cited by 54 publications

(84 citation statements)

References 56 publications

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“…This seems to be qualitatively consistent with the result obtained by Bresolin et al (2016). In the case of NGC 6822, Bresolin et al (2016) used the metallicities -Fe/H ratiosestimated by Patrick et al (2015) for a sample of red supergiants for deriving the O/H ratio of this galaxy, obtaining a 12+log(O/H) = 8.08 ± 0.21 for this object instead of the value of 8.36 ± 0.19 obtained by Venn et al (2001). Using this value the behaviour of NGC 6822 in the diagram would become more similar to that of the other low-metallicity objects in the MCs -CELs determinations more consistent with stellar abundances.…”

Section: Comparison Between Nebular and Stellar O Abundancessupporting

confidence: 86%

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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Section: Comparison Between Nebular and Stellar O Abundancessupporting

confidence: 86%

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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“…On the other hand, after the successful tests of the method at Milky Way ) and significantly lower metallicities Patrick et al 2014) we are confident that the method delivers reliable metallicities.…”

Section: Discussionmentioning

confidence: 71%

“…The pilot near-infrared J-band study of Davies et al (2010) and high spectral resolution followup by Gazak et al (2014) −both targeting galactic RSGs−demonstrate the applicability of the technique to stars with roughly solar chemical enrichment. In Davies et al (2014) and Patrick et al (2014), the technique is successfully applied to RSGs significantly below solar chemical abundance in the Small and Large Magellanic Clouds and the metal poor Local Group dwarf galaxy NGC 6822.…”

Section: Introductionmentioning

confidence: 99%

Red Supergiants as Cosmic Abundance Probes: The Sculptor Galaxy NGC 300

Gazak

Kudritzki

Evans

et al. 2015

ApJ

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We present a quantitative spectroscopic study of twenty-seven red supergiants in the Sculptor Galaxy NGC 300. J-band spectra were obtained using KMOS on the VLT and studied with state of the art synthetic spectra including NLTE corrections for the strongest diagnostic lines. We report a central metallicity of [Z]= −0.03 ± 0.05 with a gradient of −0.083 ± 0.014 [dex/kpc −1 ], in agreement with previous studies of blue supergiants and H ii-region auroral line measurements. This result marks the first application of the J-band spectroscopic method to a population of individual red supergiant stars beyond the Local Group of galaxies and reveals the great potential of this technique.

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“…Since then, a flurry of works (Gazak et al 2014;Davies et al 2015;Patrick et al 2015) have obtained similar temperatures for RSGs from different environments. Ordered by increasing metallicity, these are NGC 6822, the SMC, the LMC, and Perseus OB1.…”

Section: Introductionmentioning

confidence: 99%

“…They used the spectral synthesis method on J-band spectra, as initially proposed by Davies et al (2010). Gazak et al (2014) found temperatures for all but one of their RSGs in the Galactic Perseus OB1 association to lie in the range from 3800 K to 4100 K. Patrick et al (2015) obtained temperatures between 3790 K and 4000 K for all their RSGs in NGC 6882. Davies et al (2015) re-analysed the same data from Davies et al (2013) with this method, finding all the stars from both MCs within the range 3800 K to 4200 K, without any differences between RSGs from each galaxy.…”

Section: Introductionmentioning

confidence: 99%

Spectral type, temperature, and evolutionary stage in cool supergiants

Dorda

Negueruela

González-Fernández

et al. 2016

A&A

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Context. In recent years, our understanding of red supergiants has been questioned by strong disagreements between stellar atmospheric parameters derived with different techniques. Temperature scales have been disputed, and the possibility that spectral types do not depend primarily on temperature has been raised. Aims. We explore the relations between different observed parameters, and we explore the ability to derive accurate intrinsic stellar parameters from these relations through the analysis of the largest spectroscopic sample of red supergiants to date. Methods. We obtained intermediate-resolution spectra of a sample of about 500 red supergiants in the Large and the Small Magellanic Cloud. From these spectra, we derive spectral types and measure a large set of photospheric atomic lines. We explore possible correlations between different observational parameters, also making use of near-and mid-infrared colours and literature on photometric variability.Results. Direct comparison between the behaviour of atomic lines (Fe i, Ti i, and Ca ii) in the observed spectra and a comprehensive set of synthetic atmospheric models provides compelling evidence that effective temperature is the prime underlying variable driving the spectral-type sequence between early G and M2 for supergiants. In spite of this, there is a clear correlation between spectral type and luminosity, with later spectral types tending to correspond to more luminous stars with heavier mass loss. This trend is much more marked in the LMC than in the SMC. The population of red supergiants in the SMC is characterised by a higher degree of spectral variability, early spectral types (centred on type K1) and low mass-loss rates (as measured by dust-sensitive mid-infrared colours). The population in the LMC displays less spectroscopic variability and later spectral types. The distribution of spectral types is not single-peaked. Instead, the brightest supergiants have a significantly different distribution from less luminous objects, presenting mostly M subtypes (centred on M2), and increasing mass-loss rates for later types. In this regard, the behaviour of red supergiants in the LMC is not very different from that of Milky Way objects. Conclusions. The observed properties of red supergiants in the SMC and the LMC cannot be described correctly by standard evolutionary models. The very strong correlation between spectral type and bolometric luminosity, supported by all data from the Milky Way, cannot be reproduced at all by current evolutionary tracks.

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Red Supergiant Stars as Cosmic Abundance Probes: Kmos Observations in NGC 6822

Cited by 54 publications

References 56 publications

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

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

Red Supergiants as Cosmic Abundance Probes: The Sculptor Galaxy NGC 300

Spectral type, temperature, and evolutionary stage in cool supergiants

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