Low-mass galaxy formation and the ionizing photon budget during reionization

Duffy, Alan R.; Wyithe, J. Stuart B.; Mutch, Simon J.; Poole, Gregory B.

doi:10.1093/mnras/stu1328

Cited by 24 publications

(45 citation statements)

References 86 publications

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“…At z>7, galaxies with luminosities in the range −17<MUV<−13 provide more than ∼50 per cent of total UV flux. These results are in agreement with the findings of our hydrodynamic simulations (Smaug; see Duffy et al 2014). Due to their inefficient formation, the faintest galaxies (MUV>−10) contribute <1 per cent ionizing flux at z∼5-10.…”

Section: Uv Flux From Galaxies Below the Detection Limitsupporting

confidence: 93%

“…Rather, empirical studies and simulations show a galaxy population down to MUV=−13 is required (e.g. Robertson et al 2013;Duffy et al 2014;Robertson et al 2015;Bouwens et al 2015a). The faint-end slope of UV LFs is therefore very important since it determines the number of reionizing photons emitted from the faint galaxies below current detection limits.…”

Section: Introductionmentioning

confidence: 99%

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Dark-ages reionization and galaxy formation simulation – IV. UV luminosity functions of high-redshift galaxies

Liu¹,

Mutch²,

Angel³

et al. 2016

Mon. Not. R. Astron. Soc.

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In this paper we present calculations of the UV luminosity function from the Dark-ages Reionization And Galaxy-formation Observables from Numerical Simulations (DRAG-ONS) project, which combines N-body, semi-analytic and semi-numerical modelling designed to study galaxy formation during the Epoch of Reionization. Using galaxy formation physics including supernova feedback, the model naturally reproduces the UV LFs for high-redshift star-forming galaxies from z∼5 through to z∼10. We investigate the luminosity-star formation rate (SFR) relation, finding that variable SFR histories of galaxies result in a scatter around the median relation of 0.1-0.3 dex depending on UV luminosity. We find close agreement between the model and observationally derived SFR functions. We use our calculated luminosities to investigate the luminosity function below current detection limits, and the ionizing photon budget for reionization. We predict that the slope of the UV LF remains steep below current detection limits and becomes flat at M UV −14. We find that 48 (17) per cent of the total UV flux at z∼6 (10) has been detected above an observational limit of M UV ∼−17, and that galaxies fainter than M UV ∼−17 are the main source of ionizing photons for reionization. We investigate the luminosity-stellar mass relation, and find a correlation for galaxies with M UV <−14 that has the form M * ∝10 −0.47MUV , in good agreement with observations, but which flattens for fainter galaxies. We determine the luminosity-halo mass relation to be M vir ∝10 −0.35MUV , finding that galaxies with M UV =−20 reside in host dark matter haloes of 10 11.0±0.1 M at z∼6, and that this mass decreases towards high redshift.

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Section: Uv Flux From Galaxies Below the Detection Limitsupporting

confidence: 93%

Section: Introductionmentioning

confidence: 99%

Dark-ages reionization and galaxy formation simulation – IV. UV luminosity functions of high-redshift galaxies

Liu¹,

Mutch²,

Angel³

et al. 2016

Mon. Not. R. Astron. Soc.

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“…However, in future work we will expand upon Meraxes, adapting and improving the model to provide a better match with the results of our suite of hydrodynamical simulations, Smaug (Duffy et al 2014), run as part of the DRAGONS programme. …”

Section: Discussionmentioning

confidence: 99%

“…Bouwens et al 2011;McLure et al 2013;Schenker et al 2013). However, even next generation surveys will not extend to the faint luminosities of the faintest galaxies thought to drive the reionization of inter-galactic neutral hydrogen E-mail: smutch@unimelb.edu.au in the early Universe (Robertson et al 2013;Duffy et al 2014). Thus, alongside new probes provided by high redshift gamma-ray bursts (e.g.…”

Section: Introductionmentioning

confidence: 99%

Dark-ages reionization and galaxy formation simulation – III. Modelling galaxy formation and the epoch of reionization

Mutch

Geil

Poole

et al. 2016

Mon. Not. R. Astron. Soc.

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141

160

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We introduce Meraxes, a new, purpose-built semi-analytic galaxy formation model designed for studying galaxy growth during reionization. Meraxes is the first model of its type to include a temporally and spatially coupled treatment of reionization and is built upon a custom (100 Mpc) 3 N -body simulation with high temporal and mass resolution, allowing us to resolve the galaxy and star formation physics relevant to early galaxy formation. Our fiducial model with supernova feedback reproduces the observed optical depth to electron scattering and evolution of the galaxy stellar mass function between z=5 and 7, predicting that a broad range of halo masses contribute to reionization. Using a constant escape fraction and global recombination rate, our model is unable to simultaneously match the observed ionizing emissivity at z < ∼ 6. However, the use of an evolving escape fraction of 0.05-0.1 at z∼6, increasing towards higher redshift, is able to satisfy these three constraints. We also demonstrate that photoionization suppression of low mass galaxy formation during reionization has only a small effect on the ionization history of the inter-galactic medium. This lack of 'selfregulation' arises due to the already efficient quenching of star formation by supernova feedback. It is only in models with gas supply-limited star formation that reionization feedback is effective at regulating galaxy growth. We similarly find that reionization has only a small effect on the stellar mass function, with no observationally detectable imprint at M * >10 7.5 M . However, patchy reionization has significant effects on individual galaxy masses, with variations of factors of 2-3 at z=5 that correlate with environment.

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“…The latter prediction is supported by observations that the two strongest C IV absorbers at z ∼ 6 are physically associated with Lyman-α emitters (Díaz et al 2014), whose stellar mass is characteristically 10 8 -10 10 M⊙ (Lidman et al 2012). The tendency for low-ionization metal absorbers to trace predominantly lower-mass galaxies (Becker et al 2011;Finlator et al 2013;Kulkarni et al 2013) immediately promotes them to a critical constraint on the origin of the UVB and of cosmological reionization because current models for reionization tend to rely heavily on low-mass galaxies to provide the required flux of ionizing photons (Finlator et al 2011;Alvarez et al 2012;Kuhlen & Faucher-Giguère 2012;Jaacks et al 2012;Robertson et al 2013;Duffy et al 2014;Wise et al 2014). Such systems are generally too faint to be observed in emission, hence low-ionization absorbers will remain the only way to constrain their abundance for the foreseeable future.…”

Section: Introductionmentioning

confidence: 99%

The reionization of carbon

Finlator

Thompson

Huang

et al. 2015

Monthly Notices of the Royal Astronomical Society

109

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Observations suggest that C II was more abundant than C IV in the intergalactic medium towards the end of the hydrogen reionization epoch (z ∼ 6). This transition provides a unique opportunity to study the enrichment history of intergalactic gas and the growth of the ionizing background (UVB) at early times. We study how carbon absorption evolves from z = 10-5 using a cosmological hydrodynamic simulation that includes a self-consistent multifrequency UVB as well as a well-constrained model for galactic outflows to disperse metals. Our predicted UVB is within ∼ 2-4× of that from Haardt & Madau (2012), which is fair agreement given the uncertainties. Nonetheless, we use a calibration in post-processing to account for Lyman-α forest measurements while preserving the predicted spectral slope and inhomogeneity. The UVB fluctuates spatially in such a way that it always exceeds the volume average in regions where metals are found. This implies both that a spatially-uniform UVB is a poor approximation and that metal absorption is not sensitive to the epoch when HII regions overlap globally even at column densites of 10 12 cm −2 . We find, consistent with observations, that the C II mass fraction drops to low redshift while C IV rises owing the combined effects of a growing UVB and continued addition of carbon in low-density regions. This is mimicked in absorption statistics, which broadly agree with observations at z = 6-3 while predicting that the absorber column density distributions rise steeply to the lowest observable columns. Our model reproduces the large observed scatter in the number of low-ionization absorbers per sightline, implying that the scatter does not indicate a partially-neutral Universe at z ∼ 6.

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Low-mass galaxy formation and the ionizing photon budget during reionization

Cited by 24 publications

References 86 publications

Dark-ages reionization and galaxy formation simulation – IV. UV luminosity functions of high-redshift galaxies

Dark-ages reionization and galaxy formation simulation – IV. UV luminosity functions of high-redshift galaxies

Dark-ages reionization and galaxy formation simulation – III. Modelling galaxy formation and the epoch of reionization

The reionization of carbon

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