Continuous star formation in IZw18

Recchi, Simone; Matteuccí, F.; D’Ercole, A.; Tosi, M.

doi:10.1051/0004-6361:20040536

Cited by 44 publications

(68 citation statements)

References 89 publications

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“…The chemical evolution is usually not very detailed in these models. Recchi et al (2001Recchi et al ( , 2002Recchi et al ( , 2004 provided detailed information on the ejection efficiencies of single chemical species produced by SNe (of both Type II and Type Ia) and by winds from intermediate-mass stars. RH07 added important information on the effect of clouds.…”

Section: A Brief Overview Of Literature Resultsmentioning

confidence: 99%

“…The chemical enrichment of the galaxy is followed in detail; the production (by SNe of Type II, Type Ia, and intermediate-mass stars) of eight chemical elements (H, He, C, N, O, Mg, Si, and Fe) is considered, and the advection of these elements is followed by means of passive scalar fields. For instantaneous bursts, this scheme is described in detail in Recchi et al (2001) and its extension to more complex SFHs is explained in Recchi et al (2004). Since the code keeps correct track of the evolution of the metallicity in each computational cell, the detailed metallicity-dependent cooling function of Böhringer & Hensler (1989) can be implemented.…”

Section: The Chemo-dynamical Codementioning

confidence: 99%

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The fate of heavy elements in dwarf galaxies – the role of mass and geometry

Recchi

Hensler

2013

A&A

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Context. Energetic feedback from supernovae and stellar winds can drive galactic winds. Dwarf galaxies, due to their shallower potential wells, are assumed to be more vulnerable to this phenomenon. Metal loss through galactic winds is also commonly invoked to explain the low metal content of dwarf galaxies. Aims. Our main aim in this paper is to show that galactic mass cannot be the only parameter determining the fraction of metals lost by a galaxy. In particular, the distribution of gas must play an equally important role. Methods. We performed 2D chemo-dynamical simulations of galaxies characterized by different gas distributions, masses, and gas fractions.Results. The gas distribution can change the fraction of lost metals through galactic winds by up to one order of magnitude. In particular, disk-like galaxies tend to lose metals more easily than roundish ones. Consequently, the final metallicities attained by models with the same mass but with different gas distributions can also vary by up to one dex. Confirming previous studies, we also show that the fate of gas and freshly produced metals strongly depends on the mass of the galaxy. Smaller galaxies (with shallower potential wells) more easily develop large-scale outflows, so that the fraction of lost metals tends to be higher.

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Section: A Brief Overview Of Literature Resultsmentioning

confidence: 99%

Section: The Chemo-dynamical Codementioning

confidence: 99%

The fate of heavy elements in dwarf galaxies – the role of mass and geometry

Recchi

Hensler

2013

A&A

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“…Most importantly, the discrepancy between the observational results complicates the interpretation of chemical evolution models. Recchi et al (2004) found that abundances in the H  medium (defined by a temperature lower than 7000 K) should be similar to those in the H  gas. A definitive observational constraint is needed to challenge the models.…”

Section: Introductionmentioning

confidence: 90%

Chemical enrichment and physical conditions in I Zw 18

Lebouteiller

Heap

Hubený

et al. 2013

A&A

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Context. Low-metallicity star-forming dwarf galaxies are prime targets to understand the chemical enrichment of the interstellar medium. The H  region contains the bulk of the mass in blue compact dwarfs, and it provides important constraints on the dispersal and mixing of heavy elements released by successive star-formation episodes. The metallicity of the H  region is also a critical parameter to investigate the future star-formation history, as metals provide most of the gas cooling that will facilitate and sustain star formation. Aims. Our primary objective is to study the enrichment of the H  region and the interplay between star-formation history and metallicity evolution. Our secondary objective is to constrain the spatial-and time-scales over which the H  and H  regions are enriched, and the mass range of stars responsible for the heavy element production. Finally, we aim to examine the gas heating and cooling mechanisms in the H  region. Methods. We observed the most metal-poor star-forming galaxy in the Local Universe, I Zw 18, with the Cosmic Origin Spectrograph onboard Hubble. The abundances in the neutral gas are derived from far-ultraviolet absorption-lines (H , C , C *, N , O , ...) and are compared to the abundances in the H  region. Models are constructed to calculate the ionization structure and the thermal processes. We investigate the gas cooling in the H  region through physical diagnostics drawn from the fine-structure level of C + . Results. We find that H  region abundances are lower by a factor of ∼2 as compared to the H  region. There is no differential depletion on dust between the H  and H  region. Using sulfur as a metallicity tracer, we calculate a metallicity of 1/46 Z (vs. 1/31 Z in the H  region). From the study of the C/O, [O/Fe], and N/O abundance ratios, we propose that C, N, O, and Fe are mainly produced in massive stars. We argue that the H  envelope may contain pockets of pristine gas with a metallicity essentially null. Finally, we derive the physical conditions in the H  region by investigating the C * absorption line. The cooling rate derived from C * is consistent with collisions with H 0 atoms in the diffuse neutral gas. We calculate the star-formation rate from the C * cooling rate assuming that photoelectric effect on dust is the dominant gas heating mechanism. Our determination is in good agreement with the values in the literature if we assume a low dust-to-gas ratio (∼2000 times lower than the Milky Way value).

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“…Throughout this work, we assume chemical homogeneity (instantaneous mixing), such that outflows caused by feedback processes are assumed to have the same metallicity as the interstellar medium, though in reality the situation cannot be captured by our simple recipe (Strickland & Heckman 2009) and newly produced metals are more likely to be ejected than the gas (e.g. Recchi et al 2004). Note that, thanks to the fine sub-stepping used for the stellar evolution, also ejecta from SNII and the contributions of single low-mass stars is implemented without the need to assume the istantaneous recycling approximation.…”

Section: Chemical Evolutionmentioning

confidence: 99%

GALICS. II: the [ α/Fe] -mass relation in elliptical galaxies

Pipino¹,

Devriendt²,

Thomas³

et al. 2009

A&A

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Aims. We test whether the mass-and σ-[α/Fe] relations in the stellar populations of early-type galaxies can be reproduced by a cosmologically motivated assembly history for spheroids. Methods. We implement a detailed treatment for the chemical evolution of H, He, O, and Fe in GalICS, a semi-analytical model for galaxy formation that successfully reproduces basic low-and high-redshift galaxy properties. We take the contribution of supernovae into account (both type Ia and II), as well as low-and intermediate-mass stars, to chemical feedback. The model predictions are compared with the most recent observational results. Results. We find that the model shows significant improvement at the highest masses with respect to previous work, where the most massive galaxies were also the most α-depleted. In fact the predicted [α/Fe] ratios in this regime are now marginally consistent with observed values. We show that this result comes from the implementation of AGN quenching of star formation in massive haloes. However, this does not help with the creation of the mass-metallicity relation. Instead, at intermediate masses, the scatter in the predicted [α/Fe] ratios is much larger than the observed dispersion. This problem is related to inadequacies of the model in treating satellite galaxies. In particular, we find an excess of low-mass strongly α-enhanced satellites. Conclusions. The final stellar [α/Fe] of a single galaxy is determined by the star formation history summed over all the progenitors. In particular, a longer duration the integrated star formation history leads to a lower α-enhancement, as might be expected from the results of closed box chemical evolution models. However, non-negligible differences between closed box and hierarchical model predictions are found, due to processes such as dry mergers and hot gas-phase metal recycling in the latter case. These processes help to build up the galactic mass while keeping the α element abundance in the stars at a super-solar level. To match the observed mass-[α/Fe] relation at low and intermediate masses, we suggest that the next generation of semi-analytical model should feature either stellar or AGN feedback schemes that allow galaxies to self-regulate their own star formation history, rather than being crudely linked to the halo mass. At the same time, mechanisms that allow the very old and passively evolving satellite galaxies that do not merge to accrete fresh gas and form stars at later times should be implemented.

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Continuous star formation in IZw18

Cited by 44 publications

References 89 publications

The fate of heavy elements in dwarf galaxies – the role of mass and geometry

The fate of heavy elements in dwarf galaxies – the role of mass and geometry

Chemical enrichment and physical conditions in I Zw 18

GALICS. II: the [ α/Fe] -mass relation in elliptical galaxies

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