Exploring chemical homogeneity in dwarf galaxies: a VLT-<i>MUSE</i> study of JKB 18

James, Bethan L.; Kumari, Nimisha; Emerick, Andrew; Koposov, S. E.; McQuinn, Kristen B. W.; Stark, Daniel P.; Belokurov, Vasily; Maiolino, R.

doi:10.1093/mnras/staa1280

Cited by 19 publications

(15 citation statements)

References 97 publications

(110 reference statements)

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“…As such, we may still be underestimating dust destruction at low metallicity. On the other hand, low-metallicity dwarf galaxies are only found to be chemically inhomogeneous by factors of a few (Lebouteiller et al 2009(Lebouteiller et al , 2013James et al 2016James et al , 2020, so mixing may be efficient enough to limit the importance of this effect.…”

Section: Discussion and C O N C L U S I O N Smentioning

confidence: 99%

The impact of metallicity-dependent dust destruction on the dust-to-metals ratio in galaxies

Priestley

Barlow

2021

Monthly Notices of the Royal Astronomical Society: Letters

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The ratio of the mass of interstellar dust to the total mass of metals (the dust-to-metals/DTM ratio) tends to increase with metallicity. This can be explained by the increasing efficiency of grain growth in the interstellar medium (ISM) at higher metallicities, with a corollary being that the low DTM ratios seen at low metallicities are due to inefficient stellar dust production. This interpretation assumes that the efficiency of dust destruction in the ISM is constant, whereas it might be expected to increase at low metallicity; the decreased cooling efficiency of low-metallicity gas should result in more post-shock dust destruction via thermal sputtering. We show that incorporating a sufficiently strong metallicity dependence into models of galaxy evolution removes the need for low stellar dust yields. The contribution of stellar sources to the overall dust budget may be significantly underestimated, and that of grain growth overestimated, by models assuming a constant destruction efficiency.

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Section: Discussion and C O N C L U S I O N Smentioning

confidence: 99%

The impact of metallicity-dependent dust destruction on the dust-to-metals ratio in galaxies

Priestley

Barlow

2021

Monthly Notices of the Royal Astronomical Society: Letters

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“…These processes can regulate the star formation as well as modify the gas enrichment (e.g. Oppenheimer et al 2010;Krumholz et al 2017;Su et al 2017;James et al 2020) and could not be present in isolated H ii regions. From Fig.…”

Section: Resultsmentioning

confidence: 99%

Chemical abundances in Seyfert galaxies -- VIII. Argon abundance estimates

Monteiro,

Dors

2021

Preprint

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For the first time, the argon abundance relative to hydrogen abundance (Ar/H) in the narrow line region of a sample of Seyfert 2 nuclei has been derived. In view of this, optical narrow emission line intensities of a sample of 64 local Seyfert 2 nuclei (z < 0.25) taken from Sloan Digital Sky Survey DR7 and measured by the MPA/JHU group were considered. We adopted the T e -method for AGNs, which is based on direct determination of the electron temperature, together with a grid of photoionization model results, built with the Cloudy code, to obtain a method for the derivation of the Ar/H abundance. We find that for a metallicity range of 0.2 < ∼ (Z/Z ) < ∼ 2.0, Seyfert 2 nuclei present Ar/H abundance ranging from ∼ 0.1 to ∼ 3 times the argon solar value, adopting log(O/H) = −3.31 and log(Ar/H) = −5.60. These range of values correspond to 8.0 < ∼ (12+log(O/H) < ∼ 9.0 and 5.4 < ∼ (12+log(Ar/H) < ∼ 6.9, respectively. The range of Ar/H and Ar/O abundance values obtained from our sample are in consonance with estimations from extrapolations of the radial abundance gradients to the central parts of the disk for four spiral galaxies. We combined our abundance results with estimates obtained from a sample of H ii galaxies, which were taken from the literature, and found that the Ar/O abundance ratio decreases slightly as the O/H abundance increases.

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“…Highly scattered stellar abundance patterns of low-mass dwarf galaxies and metal-poor stars in the halo have been attributed to inhomogeneous mixing and stochastic star formation effects (James et al 2020;Mashonkina et al 2017;Simon et al 2015;Cescutti & Chiappini 2010;Cescutti 2008). Since the winds of massive stars are weak at low Z and star formation in the Bridge was only active during the last ∼200 Myr, only a few supernovae must have contributed to the chemical enrichment of the ISM.…”

Section: Metallicity Of the Bridgementioning

confidence: 99%

Discovery of O stars in the tidal Magellanic Bridge

Ramachandran

Oskinova

Hamann

2021

A&A

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The Magellanic Bridge, stretching between the Small and the Large Magellanic Cloud (SMC and LMC), is the nearest tidally stripped intergalactic environment. The Bridge has a significantly low average metallicity of Z ≲ 0.1 Z⊙. Here we report the first discovery of O-type stars in the Magellanic Bridge. Three massive O stars were identified thanks to the archival spectra obtained by the ESO’s Very Large Telescope FLAMES instrument. We analyze the spectra of each star using the Potsdam Wolf-Rayet (PoWR) non-local thermodynamic equilibrium model atmosphere code, which provides the physical parameters, ionizing photon fluxes, and surface abundances. The ages of the newly discovered O stars suggest that star formation in the Bridge is ongoing. Furthermore, the discovery of O stars in the Bridge implies that tidally stripped galactic tails containing low-density but highly dynamical gas are capable of producing massive O stars. The multi-epoch spectra indicate that all three O stars are binaries. Despite their spatial proximity to one another, these O stars are chemically distinct. One of them is a fast-rotating giant with nearly LMC-like abundances. The other two are main-sequence stars that rotate extremely slowly and are strongly metal depleted. We discover the most nitrogen-poor O star known to date. Taking into account the previous analyses of B stars in the Bridge, we interpret the various metal abundances as the signature of a chemically inhomogeneous interstellar medium (ISM), suggesting that the Bridge gas might have accreted during multiple episodes of tidal interaction between the Clouds. Attributing the lowest derived metal content to the primordial gas, the time of the initial formation of the Bridge may date back several billion years. Using the Gaia and Galex color-magnitude diagrams, we roughly estimate the total number of O stars in the Bridge and their total ionizing radiation. Comparing this with the energetics of the diffuse ISM, we find that the contribution of the hot stars to the ionizing radiation field in the Bridge is less than 10% and conclude that the main sources of ionizing photons are leaks from the LMC and SMC. We estimate a lower limit for the fraction of ionizing radiation that escapes from these two dwarf galaxies.

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Exploring chemical homogeneity in dwarf galaxies: a VLT-MUSE study of JKB 18

Cited by 19 publications

References 97 publications

The impact of metallicity-dependent dust destruction on the dust-to-metals ratio in galaxies

The impact of metallicity-dependent dust destruction on the dust-to-metals ratio in galaxies

Chemical abundances in Seyfert galaxies -- VIII. Argon abundance estimates

Discovery of O stars in the tidal Magellanic Bridge

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