THE GALAXY LUMINOSITY FUNCTION DURING THE REIONIZATION EPOCH

By M. Trenti, M. Stiavelli, R. Bouwens, P. Oesch, J. Michael Shull, G. Illingworth, L. Bradley, C. Carollo. 2010

159 citations recorded by the source corpus.

The new Wide Field Camera 3/IR observations on the Hubble Ultra-Deep Field (HUDF) started investigating the properties of galaxies during the reionization epoch. To interpret these observations, we present a novel approach inspired by the conditional luminosity function method. We calibrate our model to observations at z = 6 and assume a non-evolving galaxy luminosity versus halo mass relation. We first compare model predictions against the luminosity function (LF) measured at z = 5 and z = 4. We then predict the LF at z ⩾ 7 under the sole assumption of evolution in the underlying dark-matter halo mass function. Our model is consistent with the observed z ≳ 7 galaxy number counts in the HUDF survey and suggests a possible steepening of the faint-end slope of the LF: α(z ≳ 8) ≲ −1.9 compared to α = −1.74 at z = 6. Although we currently see only the brightest galaxies, a hidden population of lower luminosity objects (L/L* ≳ 10−4) might provide ≳75% of the total reionizing flux. Assuming escape fraction fesc ∼ 0.2, clumping factor C ∼ 5, top-heavy initial mass function (IMF), and low metallicity, galaxies below the detection limit produce complete reionization at z ≳ 8. For solar metallicity and normal stellar IMF, reionization finishes at z ≳ 6, but a smaller C/fesc is required for an optical depth consistent with the Wilkinson Microwave Anisotropy Probe measurement. Our model highlights that the star formation rate in sub-L* galaxies has a quasi-linear relation to dark-matter halo mass, suggesting that radiative and mechanical feedback were less effective at z ⩾ 6 than today.

Subfields: Astronomy and Astrophysics, Electrical and Electronic Engineering, Instrumentation

View Paper: https://www.semanticscholar.org/paper/94172d4e626a70f2a8415f6770e7f9c5c7104279

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In Astronomy and Astrophysics

1. Richard S. Ellis
2. R. Bouwens
3. P. Oesch
4. G. Illingworth
5. J. Dunlop
6. M. Franx
7. P. V. van Dokkum
8. I. Labbé

In Electrical and Electronic Engineering

1. Richard S. Ellis
2. R. Bouwens
3. J. Dunlop
4. P. Oesch
5. D. Stark
6. G. Illingworth
7. R. McLure
8. I. Labbé

In Instrumentation

1. Richard S. Ellis
2. R. Bouwens
3. P. Oesch
4. G. Illingworth
5. M. Franx
6. P. V. van Dokkum
7. I. Labbé
8. J. Dunlop

Citations in the corpus

• PROBING THE DAWN OF GALAXIES AT z ∼ 9–12: NEW CONSTRAINTS FROM HUDF12/XDF AND CANDELS DATA (2013, methodology): “In Figure 12, we compare our observational results to two conditional luminosity function models from Trenti et al. (2010) and Tacchella et al. (2012), the prediction from a semi-analytical model of Lacey et al. (2011), as well as the results from two hydrodynamical simulations of Finlator et al.…”
• CLASH: THREE STRONGLY LENSED IMAGES OF A CANDIDATE z ≈ 11 GALAXY (2012, result): “This is consistent with some theoretical predictions (Trenti et al. 2010; Lacey et al. 2011).”
• THE GRISM LENS-AMPLIFIED SURVEY FROM SPACE (GLASS). I. SURVEY OVERVIEW AND FIRST DATA RELEASE (2015, methodology): “For the first ingredient we use the model of the LBG LF recently proposed by Mason et al. (2015) building on earlier work by Trenti et al. (2010) and Tacchella et al. (2013).”
• The z ∼ 6 Luminosity Function Fainter than −15 mag from the Hubble Frontier Fields: The Impact of Magnification Uncertainties (2016, methodology): “Yue et al. (2016) adopt a very similar approach to what Mason et al. (2015) employ in predicting the galaxy LF (see also Trenti et al. 2010 and Tacchella et al. 2013).”
• CRITICAL STAR FORMATION RATES FOR REIONIZATION: FULL REIONIZATION OCCURS AT REDSHIFT z ≈ 7 (2012, methodology): “The LyC emissivity is proportional to the SFR density, computed from our halo mass function model (Trenti et al. 2010), integrated down to absolute magnitudes MAB = −18 (Bouwens et al. 2011a) or to MAB = −10, the faint limit suggested by Trenti et al. (2010).”
• REIONIZATION AFTER PLANCK: THE DERIVED GROWTH OF THE COSMIC IONIZING EMISSIVITY NOW MATCHES THE GROWTH OF THE GALAXY UV LUMINOSITY DENSITY (2015, background): “…progress to construct self-consistent models for reionizing the universe (e.g., Choudhury & Ferrara 2006; Bolton & Haehnelt 2007; Oesch et al. 2009; Trenti et al. 2010; Alvarez et al. 2012; Bouwens et al. 2012a; Finkelstein et al. 2012a; Haardt & Madau 2012 [HM12]; Kuhlen & FaucherGiguère 2012…”
• UV LUMINOSITY FUNCTIONS AT REDSHIFTS z ∼ 4 TO z ∼ 10: 10,000 GALAXIES FROM HST LEGACY FIELDS (2014, background): “Evolution in the faint-end slope α is also expected due to the steepening of the halo mass function towards early times (e.g., Trenti et al. 2010: see §5.5).”
• Concordance models of reionization: implications for faint galaxies and escape fraction evolution (2012, background): “…are consistent with theoretical analyses anchored in the predicted dark matter halo mass function, rather than to the observed luminosity function (Trenti et al. 2010; Mesinger et al. 2011; Ciardi et al. 2011), indicating that as of yet undetected galaxies must contribute significantly to…”
• A CENSUS OF STAR-FORMING GALAXIES IN THE Z ∼ 9–10 UNIVERSE BASED ON HST+SPITZER OBSERVATIONS OVER 19 CLASH CLUSTERS: THREE CANDIDATE Z ∼ 9–10 GALAXIES AND IMPROVED CONSTRAINTS ON THE STAR FORMATION RATE DENSITY AT Z ∼ 9.2 (2012, methodology): “A rapid evolution of the UV LF at z > 8 is supported by several theoretical models (Trenti et al. 2010; Lacey et al. 2011), but may be in some tension with the discovery of one bright, multiply-lensed z ∼ 10.8 galaxy in the CLASH program (C13), since one might have expected such sources to be quite…”
• ULTRAVIOLET LUMINOSITY FUNCTIONS FROM 132 z ∼ 7 AND z ∼ 8 LYMAN-BREAK GALAXIES IN THE ULTRA-DEEP HUDF09 AND WIDE-AREA EARLY RELEASE SCIENCE WFC3/IR OBSERVATIONS (2010, background): “It is unclear what physical explanation would impart such a cut-off in the LF (particularly if M∗ becomes fainter at higher redshift: §7.5), but it is possible this may be due (at least partially) to a similar exponential cut-off in the halo mass function (e.g., Trenti et al. 2010).”
• Evidence of patchy hydrogen reionization from an extreme Lyα trough below redshift six (2014, methodology): “First we assign star-forming galaxies to dark matter halos using an abundance matching scheme (e.g., equation 1 in Trenti et al. 2010).”
• CANDELS: THE CONTRIBUTION OF THE OBSERVED GALAXY POPULATION TO COSMIC REIONIZATION (2012, background): “…is highly probable that galaxies significantly fainter than this limit exist, given results from a wide variety of cosmological simulations (e.g., Trenti et al. 2010; Salvaterra et al. 2011; Finlator et al. 2011; Jaacks et al. 2012), and plausible, though scant, observational evidence (e.g.,…”
• THE MOST LUMINOUS z ∼ 9–10 GALAXY CANDIDATES YET FOUND: THE LUMINOSITY FUNCTION, COSMIC STAR-FORMATION RATE, AND THE FIRST MASS DENSITY ESTIMATE AT 500 Myr (2013, methodology): “These models include semiempirical estimates of the SFRD evolution (Trenti et al. 2010; Tacchella et al. 2013), semi-analytical models (Lacey et al. 2011), as well as hydrodynamic simulations (Finlator et al. 2011; Salvaterra et al. 2011; Dayal et al. 2013; Jaacks et al. 2013).”
• THE UV LUMINOSITY FUNCTION OF STAR-FORMING GALAXIES VIA DROPOUT SELECTION AT REDSHIFTS z ∼ 7 AND 8 FROM THE 2012 ULTRA DEEP FIELD CAMPAIGN (2012, methodology): “This steepening is also predicted by conditional luminosity function methods based on the evolution of the dark matter halo mass function (Trenti et al. 2010).”
• KECK SPECTROSCOPY OF 3 < z < 7 FAINT LYMAN BREAK GALAXIES: THE IMPORTANCE OF NEBULAR EMISSION IN UNDERSTANDING THE SPECIFIC STAR FORMATION RATE AND STELLAR MASS DENSITY (2012, result): “For example, the steep faint end slope of the ultraviolet luminosity function (UV LF) at z > 6 (Bouwens et al. 2011) implies that star formation in low mass dark matter halos becomes more efficient at earlier times (e.g., Trenti et al. 2010), in contrast to the implications of the sSFR measurements.”
• LOWER-LUMINOSITY GALAXIES COULD REIONIZE THE UNIVERSE: VERY STEEP FAINT-END SLOPES TO THE UV LUMINOSITY FUNCTIONS AT z ⩾ 5–8 FROM THE HUDF09 WFC3/IR OBSERVATIONS (2011, background): “Of course, if the faint-end slope α steepens at earlier times (as has been suggested by theory: Trenti et al. 2010), the impact of galaxies would be more substantial.”
• THE BRIGHTEST OF REIONIZING GALAXIES SURVEY: CONSTRAINTS ON THE BRIGHT END OF THE z ∼ 8 LUMINOSITY FUNCTION (2012, methodology): “Theoretical and numerical investigations predict that it should remain Schechter-like (Schechter 1976), of the form φ(L) = φ∗(L/L∗)α e−(L/L∗), at z ∼ 7–10 (Trenti et al. 2010; Jaacks et al. 2012).”