The bright end of the galaxy luminosity function at z≃7: before the onset of mass quenching?

By R. Bowler, J. Dunlop, R. McLure, A. B. Rogers, H. McCracken, B. Milvang-Jensen, H. Furusawa, Johan Peter Uldall Fynbo, Yoshiaki Taniguchi, J. Afonso and 2 more. 2013

157 citations recorded by the source corpus.

We present the results of a new search for bright star-forming galaxies at redshift z ≃ 7 within the UltraVISTA second data release (DR2) and UKIDSS (UKIRT Infrared Deep Sky Survey) UDS (Ultra Deep Survey) DR10 data, which together provide 1.65 deg^2 of near-infrared imaging with overlapping optical and Spitzer data. Using a full photometric redshift analysis, to identify high-redshift galaxies and reject contaminants, we have selected a sample of 34 luminous (−22.7<M_(UV)<−21.2 −22.7<M_(UV)<−21.2) galaxies with 6.5 < z < 7.5. Crucially, the deeper imaging provided by UltraVISTA DR2 confirms all of the robust objects previously uncovered by Bowler et al., validating our selection technique. Our new expanded galaxy sample includes the most massive galaxies known at z ≃ 7, with M^* ≃ 10^(10) M_⊙, and the majority are resolved, consistent with larger sizes (r1/2 ≃ 1–1.5 kpc) than displayed by less massive galaxies. From our final robust sample, we determine the form of the bright end of the rest-frame UV galaxy luminosity function (LF) at z ≃ 7, providing strong evidence that it does not decline as steeply as predicted by the Schechter-function fit to fainter data. We exclude the possibility that this is due to either gravitational lensing, or significant contamination of our galaxy sample by active galactic nuclei (AGN). Rather, our results favour a double power-law form for the galaxy LF at high redshift, or, more interestingly, an LF which simply follows the form of the dark matter halo mass function at bright magnitudes. This suggests that the physical mechanism which inhibits star formation activity in massive galaxies (i.e. AGN feedback or some other form of ‘mass quenching’) has yet to impact on the observable galaxy LF at z ≃ 7, a conclusion supported by the estimated masses of our brightest galaxies which have only just reached a mass comparable to the critical ‘quenching mass’ of M^* ≃ 10^(10).2 M_⊙ derived from studies of the mass function of star-forming galaxies at lower redshift.

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

View Paper: https://www.semanticscholar.org/paper/a79e58a13278cc75bfc3109b1a61327c9b727b84

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In Astronomy and Astrophysics

1. L. Hernquist
2. Richard S. Ellis
3. P. Hopkins
4. P. V. van Dokkum
5. J. Dunlop
6. M. Franx
7. P. Oesch
8. R. Bouwens

In Electrical and Electronic Engineering

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

In Instrumentation

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

Citations in the corpus

• Big Three Dragons: A z = 7.15 Lyman-break galaxy detected in [O iii] 88 μm, [C ii] 158 μm, and dust continuum with ALMA (2018, methodology): “We use the Y , J , H , and K band data taken by UltraVISTA (Bowler et al. 2014) and the deep Spitzer/IRAC 3.6 and 4.5 µm data (Bowler et al. 2017).”
• UV LUMINOSITY FUNCTIONS AT REDSHIFTS z ∼ 4 TO z ∼ 10: 10,000 GALAXIES FROM HST LEGACY FIELDS (2014, methodology): “Finally, the present LF results are in excellent agreement with the new LF determination at z ∼ 7 from Bowler et al. (2014), except for their faintest LF bin (see Figure 26).”
• The z = 9-10 galaxy population in the Hubble Frontier Fields and CLASH surveys: the z = 9 luminosity function and further evidence for a smooth decline in ultraviolet luminosity density at z≥ 8 (2016, methodology): “The LF at redshift z = 6− 8 has been the subject of numerous studies in the recent literature, and is now largely well-understood at magnitudes fainter than M1500 ' −21 (see McLure et al. 2013; Finkelstein et al. 2014; Bowler et al. 2014, 2015; Bouwens et al. 2015).”
• SUBARU HIGH-z EXPLORATION OF LOW-LUMINOSITY QUASARS (SHELLQs). I. DISCOVERY OF 15 QUASARS AND BRIGHT GALAXIES AT 5.7 < z < 6.9 (2016, unknown): “The LBG contamination in our project could be significant, particularly if the LBG luminosity function has a double power-law form instead of the Schechter function with its exponential cut-off at the bright end (Bowler et al. 2014, 2015).”
• Lyα and C iii] emission in z = 7–9 Galaxies: accelerated reionization around luminous star-forming systems? (2016, background): “In addition to RB16, the galaxy has been reported elsehwere (e.g., Tilvi et al. 2013; Bowler et al. 2014).”
• A SPECTROSCOPIC REDSHIFT MEASUREMENT FOR A LUMINOUS LYMAN BREAK GALAXY AT z = 7.730 USING KECK/MOSFIRE (2015, background): “As these lines shift into the IRAC 4.5 µm band, galaxies at z ∼ 7 to z ∼ 9 exhibit red [3.6]−[4.5] IRAC colors (see also Stark et al. 2013; Labbé et al. 2013; Bowler et al. 2014).”
• THE EVOLUTION OF THE GALAXY REST-FRAME ULTRAVIOLET LUMINOSITY FUNCTION OVER THE FIRST TWO BILLION YEARS (2014, methodology): “For the double power law, we used the form given in Equation (2) of Bowler et al. (2014), which is similar to the Schechter function at the faint end, but replaces the bright end with a second power law with slope β.”
• The COSMOS2015 galaxy stellar mass function . Thirteen billion years of stellar mass assembly in ten snapshots (2017, methodology): “Unlike dwarf star spectra used in previous work (e.g. Ouchi et al. 2009; Bouwens et al. 2011; Bowler et al. 2014) those derived from Baraffe et al. (2015) extend to λr.f. > 2.5 µm and therefore SPLASH photometry contributes to disentangling their degeneracy with distant galaxies (Wilkins et al.…”
• Evolution of the AGN UV luminosity function from redshift 7.5 (2018, background): “…AGN may also be consistent with the shallow bright-end slopes of the z ∼ 7 UV luminosity function of galaxies relative to a Schechter function (Bowler et al. 2012, 2014; Bradley et al. 2014; Bowler et al. 2015) and the hard spectra of these galaxies (Stark et al. 2015a,b, 2017; Laporte et…”
• The galaxy luminosity function at z ≃ 6 and evidence for rapid evolution in the bright end from z ≃ 7 to 5 (2014, methodology): “This work at z ' 6 and the analogous work at z ' 7 presented in Bowler et al. (2014) allow the form and evolution of the bright end of the LF to be tightly constrained, and potential evolution of the functional form to be investigated.”
• EVIDENCE FOR PopIII-LIKE STELLAR POPULATIONS IN THE MOST LUMINOUS Lyα EMITTERS AT THE EPOCH OF REIONIZATION: SPECTROSCOPIC CONFIRMATION (2015, methodology): “This indicates that the Lyα EW is very high and highlights that the Lyman-break selection can easily miss such sources, even if they are extremely bright and compact in Lyα, as MASOSA is not detected at the current depth of the UltraVISTA survey (Bowler et al. 2014).”
• Constraining the galaxy–halo connection over the last 13.3 Gyr: star formation histories, galaxy mergers and structural properties (2017, methodology): “Observational data are from Bouwens et al. (2007, 2011, 2015, 2016); Bowler et al. (2014); Finkelstein et al. (2015); McLure et al. (2013); Oesch et al. (2012); Schenker et al. (2013); van der Burg, Hildebrandt & Erben (2010) and Willott et al. (2013).”
• Full-data Results of Hubble Frontier Fields: UV Luminosity Functions at z ∼ 6–10 and a Consistent Picture of Cosmic Reionization (2017, methodology): “We use recent results of blank field surveys; Bouwens et al. (2015); Bowler et al. (2014); Ouchi et al. (2009); Bradley et al. (2012); Oesch et al. (2013); Calvi et al. (2016).”
• Identification of the brightest Lyα emitters at z = 6.6 : Implications for the evolution of the luminosity function in the reionization era (2015, background): “As expected, none of our LAE candidates except for CR7, are in the UV selected z ∼ 7 galaxy catalogue from Bowler et al. (2014), since they are not detected in broadband photometry.”
• THE EVOLUTION OF THE GALAXY STELLAR MASS FUNCTION AT z = 4–8: A STEEPENING LOW-MASS-END SLOPE WITH INCREASING REDSHIFT (2015, background): “Over the past few years, a number of studies have found that the exponential cutoff of the UV luminosity function appears to weaken at z ≥ 7 (Bowler et al. 2014; Finkelstein et al. 2015; Bowler et al. 2015).”