The extreme faint end of the UV luminosity function at z ∼ 6 through gravitational telescopes: a comprehensive assessment of strong lensing uncertainties

By H. Atek, J. Richard, Jean-Paul Kneib, Daniel Schaerer. Monthly notices of the Royal Astronomical Society, 2018

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With the Hubble Frontier Fields program, gravitational lensing has provided a powerful way to extend the study of the ultraviolet luminosity function (LF) of galaxies at $z \sim 6$ down to unprecedented magnitude limits. At the same time, significant discrepancies between different studies were found at the very faint end of the LF. In an attempt to understand such disagreements, we present a comprehensive assessment of the uncertainties associated with the lensing models and the size distribution of galaxies. We use end-to-end simulations from the source plane to the final LF that account for all lensing effects and systematic uncertainties by comparing several mass models. In addition to the size distribution, the choice of lens model leads to large differences at magnitudes fainter than $M_{UV} = -15~$ AB mag, where the magnification factor becomes highly uncertain. We perform MCMC simulations that include all these uncertainties at the individual galaxy level to compute the final LF, allowing, in particular, a crossover between magnitude bins. The best LF fit, using a modified Schechter function that allows for a turnover at faint magnitudes, gives a faint-end slope of $\alpha = -2.01_{-0.14}^{+0.12}$, a curvature parameter of $\beta = 0.48_{-0.25}^{+0.49}$, and a turnover magnitude of $M_{T} = -14.93_{-0.52}^{+0.61}$. Most importantly our procedure shows that robust constraints on the LF at magnitudes fainter than $M_{UV} = -15~$ AB remain unrealistic. More accurate lens modeling and future observations of lensing clusters with the James Webb Space Telescope can reliably extend the UV LF to fainter magnitudes.

Subfields: Astronomy and Astrophysics, Atomic and Molecular Physics, and Optics

View Paper: https://www.semanticscholar.org/paper/28e7c55bb296a34886b64b9cf14f843ba694ab8e

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Citations in the corpus

Early Results from GLASS-JWST. III. Galaxy Candidates at z ∼9–15 (2022, background): “…large samples of LBGs at z∼2–8 (e.g. Reddy & Steidel 2009; McLure et al. 2013; Finkelstein et al. 2015; Roberts-Borsani et al. 2016; Ono et al. 2018; Atek et al. 2018), and progessively smaller samples of increasingly bright objects at higher redshifts up to z∼9– 11 (Zheng et al. 2012; Oesch et…”
Conditions for Reionizing the Universe with a Low Galaxy Ionizing Photon Escape Fraction (2019, background): “…Hubble Frontier Fields (Lotz et al. 2017) have begun to provide empirical justification, with evidence that the observed luminosity functions maintain their steep slopes down to MUV>−16 at z=6 (Atek et al. 2015) and possibly to MUV>−15 (Bouwens et al. 2017; Livermore et al. 2017; Atek et al. 2018).”
A Comprehensive Study of Galaxies at z ∼ 9–16 Found in the Early JWST Data: Ultraviolet Luminosity Functions and Cosmic Star Formation History at the Pre-reionization Epoch (2022, background): “…mag) UV luminosity function at z∼ 6–10 is probed with galaxies behind massive clusters, e.g., with HFF data, via gravitational lensing magnification (Atek et al. 2015, 2018; Ishigaki et al. 2015, 2018; Laporte et al. 2016; Livermore et al. 2017; Oesch et al. 2018), while the faint-end slopes and…”
RELICS: Reionization Lensing Cluster Survey (2019, background): “By combining deep Hubble imaging with the power of gravitational lensing, the Frontier Fields revealed the faintest galaxies yet known, including some of those likely responsible for reionization at z ∼ 6 (Livermore et al. 2016; Atek et al. 2018).”
The bolometric quasar luminosity function at z = 0–7 (2020, methodology): “Bowler et al. 2015; Bouwens et al. 2015; Parsa et al. 2016; Finkelstein 2016; Mehta et al. 2017; Atek et al. 2015, 2018; Ishigaki et al. 2018) and theoretical studies (Jaacks et al. 2012; Tacchella et al. 2013; Mason et al. 2015; Wilkins et al. 2017; Tacchella et al. 2018; Yung et al. 2018).”
Evolution of the AGN UV luminosity function from redshift 7.5 (2018, methodology): “…functions and the incorporation of systematic errors into AGN luminosity function measurements, in a similar manner to recent surveys for lensed high-redshift galaxies that are limited by the accuracy of the lensing mass models (Bouwens et al. 2017; Ishigaki et al. 2018; Atek et al. 2018).”
Rapid Reionization by the Oligarchs: The Case for Massive, UV-bright, Star-forming Galaxies with High Escape Fractions (2019, background): “Our best-fit faint-end slope values are somewhat shallower than what is reported in the recent literature from observations (Bouwens et al. 2017; Livermore et al. 2017; Atek et al. 2018).”
Inferring the astrophysics of reionization and cosmic dawn from galaxy luminosity functions and the 21-cm signal (2018, background): “The observations show scatter between various groups, in particular at the faint end which is dominated by lensing uncertainties (Bouwens et al. 2015a, 2016; Livermore et al. 2016; Atek et al. 2018; Ishigaki et al. 2017).”