Interstellar Turbulence II: Implications and Effects

Scalo, J. M.; Elmegreen, Bruce G.

doi:10.1146/annurev.astro.42.120403.143327

Cited by 309 publications

(164 citation statements)

References 269 publications

(342 reference statements)

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“…Theoretical investigations of metal abundance fluctuations in the ISM have until recently been based on order of magnitude arguments involving characteristic spatial scales and timescales for various turbulent mixing processes, see e.g. Roy & Kunth (1995), and Scalo & Elmegreen (2004) for a review. More recently, sophisticated 3D (magneto-)hydrodynamic simulations of the local ISM at high resolution (e.g.…”

Section: Stellar Evolution: the Initial Chemical Compositionmentioning

confidence: 99%

Present-day cosmic abundances

Nieva

Przybilla²

2012

A&A

450

506

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Context. Early B-type stars are ideal indicators for present-day cosmic abundances since they preserve their pristine abundances and typically do not migrate far beyond their birth environments over their short lifetimes, in contrast to older stars like the Sun. They are also unaffected by depletion onto dust grains, unlike the cold/warm interstellar medium (ISM) or H ii regions. Aims. A carefully selected sample of early B-type stars in OB associations and the field within the solar neighbourhood is studied comprehensively. Quantitative spectroscopy is used to characterise their atmospheric properties in a self-consistent way. Present-day abundances for the astrophysically most interesting chemical elements are derived in order to investigate whether a present-day cosmic abundance standard can be established. Methods. High-resolution and high-S/N FOCES, FEROS and ELODIE spectra of well-studied sharp-lined early B-type stars are analysed in non-LTE. Line-profile fits based on extensive model grids and an iterative analysis methodology are used to constrain stellar parameters and elemental abundances at high accuracy and precision. Atmospheric parameters are derived from the simultaneous establishment of independent indicators, from multiple ionization equilibria and the Stark-broadened hydrogen Balmer lines, and they are confirmed by reproduction of the stars' global spectral energy distributions. Results. Effective temperatures are constrained to 1-2% and surface gravities to less than 15% uncertainty, along with accurate rotational, micro-and macroturbulence velocities. Good agreement of the resulting spectroscopic parallaxes with those from the new reduction of the Hipparcos catalogue is obtained. Absolute values for abundances of He, C, N, O, Ne, Mg, Si and Fe are determined to better than 25% uncertainty. The synthetic spectra match the observations reliably over almost the entire visual spectral range. Three sample stars, γ Ori, o Per and θ 1 Ori D, are identified as double-lined, indicating the presence of an early/mid B-type companion. Conclusions. A present-day cosmic abundance standard is established from a sample of 29 early B-type stars, indicating abundance fluctuations of less than 10% around the mean. Our results (i) resolve the long-standing discrepancy between a chemical homogeneous gas-phase ISM and a chemically inhomogeneous young stellar component out to several hundred parsec from the Sun, (ii) facilitate the amount of heavy elements locked up in the interstellar dust to be constrained precisely -the results imply that carbonaceous dust is largely destroyed inside the Orion H ii region, unlike the silicates, and that graphite is only a minority species in interstellar dust -, (iii) show that the mixing of CNO-burning products in the course of massive star evolution follows tightly the predicted nuclear path, (iv) provide reliable present-day reference points for anchoring Galactic chemical evolution models to observation, and (v) imply that the Sun has migrated outwards from the inne...

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Section: Stellar Evolution: the Initial Chemical Compositionmentioning

confidence: 99%

Present-day cosmic abundances

Nieva

Przybilla²

2012

A&A

450

506

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“…Scalo & Elmegreen 2004). If we divide the scatter by the slope of the gradient we obtain a measurement of how far a certain H ii region has been able to move from its expected location based on the displayed abundance gradient, that is, the mixing scalelength (r mix , Sánchez et al 2015).…”

Section: Dispersion Of the Gradient And Mixing Scalelengthmentioning

confidence: 99%

The shape of oxygen abundance profiles explored with MUSE: evidence for widespread deviations from single gradients

Sánchez-Menguiano

Sanchez

Pérez

et al. 2018

A&A

150

146

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We characterised the oxygen abundance radial distribution of a sample of 102 spiral galaxies observed with VLT/MUSE using the O3N2 calibrator. The high spatial resolution of the data allowed us to detect 14345 H ii regions with the same image quality as with photometric data, avoiding any dilution effect. We developed a new methodology to automatically fit the abundance radial profiles, finding that 55 galaxies of the sample exhibit a single negative gradient. The remaining 47 galaxies also display, as well as this negative trend, either an inner drop in the abundances (21), an outer flattening (10), or both (16), which suggests that these features are a common property of disc galaxies. The presence and depth of the inner drop depends on the stellar mass of the galaxies with the most massive systems presenting the deepest abundance drops, while there is no such dependence in the case of the outer flattening. We find that the inner drop appears always around 0.5 r e , while the position of the outer flattening varies over a wide range of galactocentric distances. Regarding the main negative gradient, we find a characteristic slope in the sample of α O/H = − 0.10 ± 0.03 dex/r e . This slope is independent of the presence of bars and the density of the environment. However, when inner drops or outer flattenings are detected, slightly steeper gradients are observed. This suggests that radial motions might play an important role in shaping the abundance profiles. We define a new normalisation scale ('the abundance scale length', r O/H ) for the radial profiles based on the characteristic abundance gradient, with which all the galaxies show a similar position for the inner drop (∼ 0.5 r O/H ) and the outer flattening (∼ 1.5 r O/H ). Finally, we find no significant dependence of the dispersion around the negative gradient with any property of the galaxies, with values compatible with the uncertainties associated with the derivation of the abundances.

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“…Turbulence is considered to be a decisive factor in mixing theories (for a review see Scalo & Elmegreen 2004). Mixing of stellar ejecta into ICM that forms subsequent generations of stars is strongly constrained by observations (e.g.…”

Section: Mixing Of Supernovae Ejecta With Pristine Gasmentioning

confidence: 99%

Superbubble dynamics in globular cluster infancy

Krause

Charbonnel

Decressin

et al. 2013

A&A

138

155

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Context. The self-enrichment scenario for globular clusters (GC) requires large amounts of residual gas after the initial formation of the first stellar generation. Recently, we found that supernovae may not be able to expel that gas, as required to explain their presentday gas-free state, and suggested that a sudden accretion onto the dark remnants at a stage when type II supernovae have ceased may plausibly lead to fast gas expulsion. Aims. Here, we explore the consequences of these results for the self-enrichment scenario via fast-rotating massive stars (FRMS). Methods. We analysed the interaction of FRMS with the intra-cluster medium (ICM), in particular where, when, and how the second generation of stars may form. From the results, we developed a timeline of the first ≈40 Myr of GC evolution. Results. Our previous results imply three phases during which the ICM is in a fundamentally different state, namely the wind bubble phase (lasting 3.5 to 8.8 Myr), the supernova phase (lasting 26.2 to 31.5 Myr), and the dark remnant accretion phase (lasting 0.1 to 4 Myr): (i) Quickly after the first-generation massive stars have formed, stellar wind bubbles compress the ICM into thin filaments. No stars may form in the normal way during this phase because of the high Lyman-Werner flux density. If the first-generation massive stars have equatorial ejections however, as we proposed in the FRMS scenario, accretion may resume in the shadow of the equatorial ejecta. The second-generation stars may then form due to gravitational instability in these disc, which are fed by both the FRMS ejecta and pristine gas. (ii) In the supernova phase the ICM develops strong turbulence, with characteristic velocities below the escape velocity. The gas does not accrete either onto the stars or onto the dark remnants in this phase because of the high gas velocities. The strong mass loss associated with the transformation of the FRMS into dark remnants then leads to the removal of the secondgeneration stars from the immediate vicinity of the dark remnants. (iii) When the supernovae have ceased, turbulence quickly decays, and the gas can once more accrete, now onto the dark remnants. As discussed previously, this may release sufficient energy to unbind the gas, and may happen fast enough so that a large fraction of less tightly bound first-generation stars are lost. Conclusions. Studying the FRMS scenario for the self-enrichment of GCs in detail reveals the important role of the physics of the ICM for our understanding of the formation and early evolution of GCs. Depending on the level of mass segregation, this sets constraints on the orbital properties of the stars, in particular high orbital eccentricities, which likely has implications on the GC formation scenario.

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Interstellar Turbulence II: Implications and Effects

Cited by 309 publications

References 269 publications

Present-day cosmic abundances

Present-day cosmic abundances

The shape of oxygen abundance profiles explored with MUSE: evidence for widespread deviations from single gradients

Superbubble dynamics in globular cluster infancy

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