The z ∼ 6 Luminosity Function Fainter than −15 mag from the Hubble Frontier Fields: The Impact of Magnification Uncertainties

By R. Bouwens, P. Oesch, G. Illingworth, Richard S. Ellis, M. Stefanon. 2016

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We use the largest sample of galaxies to date from the first four Hubble Frontier Fields clusters to set constraints on the shape of the luminosity functions (LFs) to fainter than mag. We quantify, for the first time, the impact of magnification uncertainties on LF results and thus provide more realistic constraints than other recent work. Our simulations reveal that, for the highly magnified sources, the systematic uncertainties can become extremely large fainter than −14 mag, reaching several orders of magnitude at 95% confidence at approximately −12 mag. Our new forward-modeling formalism incorporates the impact of magnification uncertainties into the LF results by exploiting the availability of many independent magnification models for the same cluster. One public magnification model is used to construct a mock high-redshift galaxy sample that is then analyzed using the other magnification models to construct an LF. Large systematic errors occur at high magnifications ( ) because of differences between the models. The volume densities we derive for faint (≳−17 mag) sources are ∼3–4× lower than one recent report and give a faint-end slope , which is 3.0–3.5σ shallower (including or not including the size uncertainties, respectively). We introduce a new curvature parameter δ to model the faint end of the LF and demonstrate that the observations permit (at 68% confidence) a turn-over at in the range of −15.3 to −14.2 mag, depending on the assumed lensing model. The present consideration of magnification errors and new size determinations raise doubts about previous reports regarding the form of the LF at . We discuss the implications of our turn-over constraints in the context of recent theoretical predictions.

Subfields: Astronomy and Astrophysics, Instrumentation

View Paper: https://www.semanticscholar.org/paper/0c18de3f7faec1548f7590d9711533eb1b7ab614

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Citations in the corpus

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).”
The Dearth of z ∼ 10 Galaxies in All HST Legacy Fields—The Rapid Evolution of the Galaxy Population in the First 500 Myr (2017, background): “…distribution functions are based on recent observations of both the redshift and luminosity dependence of galaxy sizes (see e.g. Oesch et al. 2010; Grazian et al. 2012; Huang et al. 2013; Ono et al. 2013; Holwerda et al. 2015; Kawamata et al. 2015; CurtisLake et al. 2016; Bouwens et al. 2017a).”
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): “…2015, 2018; Laporte et al. 2016; Livermore et al. 2017; Oesch et al. 2018), while the faint-end slopes and luminosity function turnovers are poorly constrained due to the limited statistics and lensing magnification systematics (Bouwens et al. 2017, 2022a; Kawamata et al. 2018; Yang et al. 2022).”
Full-data Results of Hubble Frontier Fields: UV Luminosity Functions at z ∼ 6–10 and a Consistent Picture of Cosmic Reionization (2017, methodology): “Many groups study the properties of high-redshift galaxies using a part of the HFF data (Atek et al. 2015a,b; Zheng et al. 2014; Coe et al. 2015; Oesch et al. 2015; Ishigaki et al. 2015, 2016; Kawamata et al. 2015, 2016; Livermore et al. 2017; Bouwens et al. 2017a,b; McLeod et al. 2015, 2016).”
The Universe Is Reionizing at z ∼ 7: Bayesian Inference of the IGM Neutral Fraction Using Lyα Emission from Galaxies (2017, methodology): “…draw a realistic sample of LBGs at z ∼ 7 from the Mason et al. (2015) UV luminosity function model (which is consistent with all observations, including new deep data from the Hubble Frontier Fields at z∼> 7 e.g., Atek et al. 2015b; McLeod et al. 2016; Livermore et al. 2017; Bouwens et al. 2017a).”
Constraining the mass of light bosonic dark matter using SDSS Lyman-α forest (2017, background): “…function (Bouwens et al. 2015; Livermore et al. 2017), as derived from deep observations such as the Hubble Frontier Fields, MNRAS 000, 1–11 (2017) are still subject to large uncertainties (Bouwens et al. 2017) but they do not clearly point towards a deviation from the CDM Schechter law.”
The bolometric quasar luminosity function at z = 0–7 (2020, methodology): “The binned estimations of the GUVLF include: the compilation from Finkelstein (2016) at z = 4 − 10, Alavi et al. (2014); Mehta et al. (2017) at z = 2, Parsa et al. (2016) at z = 2, 4, van der Burg et al. (2010) at z = 4, Bouwens et al. (2017); Atek et al. (2018) at z = 6.”
The SPHINX Cosmological Simulations of the First Billion Years: the Impact of Binary Stars on Reionization★ (2018, methodology): “Redshift 6 luminosity functions from our 10 and higher resolution 5 cMpc volumes (ignoring absorption), and from the observational compilations of Bouwens et al. (2017) and Livermore, Finkelstein & Lotz (2017), as indicated in the legend.”
Great Optically Luminous Dropout Research Using Subaru HSC (GOLDRUSH). I. UV Luminosity Functions at $z \sim 4-7$ Derived with the Half-Million Dropouts on the 100 deg$^2$ Sky (2017, background): “…et al. 2017), although it has been pointed out that the analyses for the lensing fields would be significantly affected by systematic errors such as the one from the assumed size distribution of faint galaxies (Bouwens et al. 2017a) and the constructed magnification maps (Bouwens et al. 2017b).”
The extreme faint end of the UV luminosity function at z ∼ 6 through gravitational telescopes: a comprehensive assessment of strong lensing uncertainties (2018, methodology): “In particular, Bouwens et al. (2017a) find that galaxies down to MAB ∼ −15 mag have near-point source profiles with typical half-light radii below 30 mas.”
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).”