The imprint of reionization on the star formation histories of dwarf galaxies

Benitez-Llambay, Alejand ro; Navarro, Julio F.; Abadi, Mario G.; Gottlöber, Stefan; Yepes, Gustavo; Hoffman, Yehuda; Steinmetz, Matthias

doi:10.1093/mnras/stv925

Cited by 74 publications

(85 citation statements)

References 82 publications

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“…For example, Gallart et al (2015) proposed that strong internal feedback and reionization may couple to induce important gas loss at early times leading to early quenching in fast dwarfs, while this coupling may not occur in slow dwarfs, in which the onset of star formation would be delayed and take place only when the dark matter halo has grown massive enough to allow the gas to cool and form stars after reionization. A similar dichotomy in SFHs was noticed in work by Benítez-Llambay et al (2015), which makes use of the CLUES simulations (Gottloeber et al 2010. The dwarf galaxies with predominantly old SFHs are those inhabiting DM haloes that collapse early and where re-ionization coupled with internal feedback drives the lowdensity gas out of the virial radius, preventing further re- Gallart et al (2015).…”

Section: Relation To the Present-day Stellar Masssupporting

confidence: 71%

On the early evolution of Local Group dwarf galaxy types: star formation and supernova feedback

Bermejo-Climent

Battaglia

Gallart

et al. 2018

Monthly Notices of the Royal Astronomical Society

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According to star formation histories (SFHs), Local Group dwarf galaxies can be broadly classified in two types: those forming most of their stars before z = 2 (fast) and those with more extended SFHs (slow). The most precise SFHs are usually derived from deep but not very spatially extended photometric data; this might alter the ratio of old to young stars when age gradients are present. Here we correct for this effect and derive the mass formed in stars by z = 2 for a sample of 16 Local Group dwarf galaxies. We explore early differences between fast and slow dwarfs, and evaluate the impact of internal feedback by supernovae (SN) on the baryonic and dark matter (DM) component of the dwarfs. Fast dwarfs assembled more stellar mass at early times and have larger amounts of DM within the half-light radius than slow dwarfs. By imposing that slow dwarfs cannot have lost their gas by z = 2, we constrain the maximum coupling efficiency of SN feedback to the gas and to the DM to be ∼10%. We find that internal feedback alone appears insufficient to quench the SFH of fast dwarfs by gas deprivation, in particular for the fainter systems. Nonetheless, SN feedback can core the DM halo density profiles relatively easily, producing cores of the sizes of the halflight radius in fast dwarfs by z = 2 with very low efficiencies. Amongst the "classical" Milky Way satellites, we predict that the smallest cores should be found in Draco and Ursa Minor, while Sculptor and Fornax should host the largest ones.

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Section: Relation To the Present-day Stellar Masssupporting

confidence: 71%

On the early evolution of Local Group dwarf galaxy types: star formation and supernova feedback

Bermejo-Climent

Battaglia

Gallart

et al. 2018

Monthly Notices of the Royal Astronomical Society

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“…As discussed by Benítez-Llambay et al (2015) the two distinct components form as a result of a merger between two systems whose masses were very close to the hydrogen-cooling limit at the time of cosmic reionization, zreion. They are able to form some stars before reionization but, because of their weak potential wells, star formation activity declines soon thereafter as the combined effects of reionization and feedback heat the remaining gas.…”

Section: Resultsmentioning

confidence: 99%

Mergers and the outside-in formation of dwarf spheroidals

Benítez-Llambay¹,

Navarro²,

Abadi³

et al. 2015

Mon. Not. R. Astron. Soc.

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We use a cosmological simulation of the formation of the Local Group to explore the origin of age and metallicity gradients in dwarf spheroidal galaxies. We find that a number of simulated dwarfs form "outside-in", with an old, metal-poor population that surrounds a younger, more concentrated metal-rich component, reminiscent of dwarf spheroidals like Sculptor or Sextans. We focus on a few examples where stars form in two populations distinct in age in order to elucidate the origin of these gradients. The spatial distributions of the two components reflect their diverse origin; the old stellar component is assembled through mergers, but the young population forms largely in situ. The older component results from a first episode of star formation that begins early but is quickly shut off by the combined effects of stellar feedback and reionization. The younger component forms when a late accretion event adds gas and reignites star formation. The effect of mergers is to disperse the old stellar population, increasing their radius and decreasing their central density relative to the young population. We argue that dwarf-dwarf mergers offer a plausible scenario for the formation of systems with multiple distinct populations and, more generally, for the origin of age and metallicity gradients in dwarf spheroidals.

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“…on the properties of dwarf galaxies in cosmological simulations (e.g. Benítez-Llambay et al 2015;Garrison-Kimmel et al, in prep.). Our approach is therefore to provide a UVB model with a fiducial reionization history motivated by current constraints and to also make available, in electronic form, data for other reionization parameters.…”

Section: Reionization History Parametersmentioning

confidence: 99%

A cosmic UV/X-ray background model update

Faucher-Giguère

2020

Monthly Notices of the Royal Astronomical Society

187

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We present an updated model of the cosmic ionizing background from the UV to the X-rays. Relative to our previous model ), the new model provides a better match to a large number of up-to-date empirical constraints, including: 1) new galaxy and AGN luminosity functions; 2) stellar spectra including binary stars; 3) obscured and unobscured AGN; 4) a measurement of the non-ionizing UV background; 5) measurements of the intergalactic HI and HeII photoionization rates at z ∼ 0 − 6; 6) the local X-ray background; and 7) improved measurements of the intergalactic opacity. In this model, AGN dominate the HI ionizing background at z 3 and star-forming galaxies dominate it at higher redshifts. Combined with the steeply declining AGN luminosity function beyond z ∼ 2, the slow evolution of the HI ionization rate inferred from the high-redshift HI Lyα forest requires an escape fraction from star-forming galaxies that increases with redshift (a population-averaged escape fraction of ≈ 1% suffices to ionize the intergalactic medium at z = 3 when including the contribution from AGN). We provide effective photoionization and photoheating rates calibrated to match the Planck 2018 reionization optical depth and recent constraints from the HeII Lyα forest in hydrodynamic simulations.

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The imprint of reionization on the star formation histories of dwarf galaxies

Cited by 74 publications

References 82 publications

On the early evolution of Local Group dwarf galaxy types: star formation and supernova feedback

On the early evolution of Local Group dwarf galaxy types: star formation and supernova feedback

Mergers and the outside-in formation of dwarf spheroidals

A cosmic UV/X-ray background model update

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