Galaxy Stellar Mass Functions from z ∼ 10 to z ∼ 6 using the Deepest Spitzer/Infrared Array Camera Data: No Significant Evolution in the Stellar-to-halo Mass Ratio of Galaxies in the First Gigayear of Cosmic Time

Abstract

We present new stellar mass functions at z ∼ 6, z ∼ 7, z ∼ 8, z ∼ 9 and, for the first time, z ∼ 10, constructed from ∼800 Lyman-break galaxies previously identified over the eXtreme Deep Field and Hubble Ultra-Deep Field parallel fields and the five Cosmic Assembly Near-infrared Deep Extragalactic Legacy Survey fields. Our study is distinctive due to (1) the much deeper (∼200 hr) wide-area Spitzer/Infrared Array Camera (IRAC) imaging at 3.6 μm and 4.5 μm from the Great Observatories Origins Deep Survey Re-ionization Era Wide-area Treasury from Spitzer program (GREATS) and (2) consideration of z ∼ 6–10 sources over a 3× larger area than those of previous Hubble Space Telescope+Spitzer studies. The Spitzer/IRAC data enable ≥2σ rest-frame optical detections for an unprecedented 50% of galaxies down to a stellar mass limit of ∼ 10 8  ⊙ across all redshifts. Schechter fits to our volume densities suggest a combined evolution in the characteristic mass  * and normalization factor ϕ * between z ∼ 6 and z ∼ 8. The stellar mass density (SMD) increases by ∼1000× in the ∼500 Myr between z ∼ 10 and z ∼ 6, with indications of a steeper evolution between z ∼ 10 and z ∼ 8, similar to the previously reported trend of the star formation rate density. Strikingly, abundance matching to the Bolshoi–Planck simulation indicates halo mass densities evolving at approximately the same rate as the SMD between z ∼ 10 and z ∼ 4. Our results show that the stellar-to-halo mass ratios, a proxy for the star formation efficiency, do not change significantly over the huge stellar mass buildup occurred from z ∼ 10 to z ∼ 6, indicating that the assembly of stellar mass closely mirrors the buildup in halo mass in the first ∼1 Gyr of cosmic history. The James Webb Space Telescope is poised to extend these results into the “first galaxy” epoch at z ≳ 10.

Star formation histories of UV-luminous galaxies at $z \simeq 6.8$: implications for stellar mass assembly at early cosmic times

“…An alternative path towards constraining star formation at early cosmic times is quantifying the total stellar mass content of the Universe at 𝑧 ∼ 6 − 9 (e.g., Duncan et al 2014;Grazian et al 2015;Song et al 2016;Bhatawdekar et al 2019;Kikuchihara et al 2020;Stefanon et al 2021). In this work, we have systematically studied the stellar masses, ages, and SFHs of galaxies in the narrow redshift window of 𝑧 6.6−6.9, where nebular emission lines can be cleanly separated from rest-optical stellar continuum in IRAC photometry.…”

“…Over the last two decades, this census of stellar mass at 𝑧 ∼ 6 − 9 has been enabled by Spitzer/Infrared Array Camera (IRAC) imaging at 3.6 𝜇m and 4.5 𝜇m (e.g. Egami et al 2004;Eyles et al 2005;Stark et al 2009;González et al 2011;Labbé et al 2013;Oesch et al 2014;Duncan et al 2014;Grazian et al 2015;Song et al 2016;Bhatawdekar et al 2019;Kikuchihara et al 2020;Stefanon et al 2021), which probes the rest-frame optical stellar continuum that is key to clean measurements of stellar mass. However, broadband IRAC photometry can also be contaminated by strong nebular emission lines, leading to systematic uncertainties on individual stellar masses (and consequently the total stellar mass content of the Universe) if the exact contribution of nebular lines to the photometry is unknown (e.g.…”

Elevated Hot Gas and High-mass X-Ray Binary Emission in Low-metallicity Galaxies: Implications for Nebular Ionization and Intergalactic Medium Heating in the Early Universe

“…For sample selection purposes, we selected all galaxies with metallicities in the narrow range of 12 log O H ( ) + = 8.1-8.2 (Z ≈ 0.26-0.32Z e ), near the lowest limit by which the PP04 diagnostic is accurate. For context, e.g., Madau & Fragos (2017, see their Figure 2) and Guo et al (2010) show that a metallicity of Z ≈ 0.3Z e corresponds to the mass-weighted metallicity of the universe at z ≈ 6 and the metallicity of relatively massive galaxies M M log   ≈ 9-10 at z ≈ 10, where the knee of the stellar mass function is estimated to be 10 9.5   » * M e (e.g., Stefanon et al 2021). To further identify galaxies that were more explicitly similar to z ≈ 10 massive galaxies, we made use of the SFR and M å estimates from Salim et al (2016), and filtered our sample to contain galaxies with SFR ≈ 2-20 M e yr −1 and M M log   » 8.5-10 (see, e.g., Guo et al 2010;Salmon et al 2015;Song et al 2016).…”

z~2-9 Galaxies Magnified by the Hubble Frontier Field Clusters II: Luminosity Functions and Constraints on a Faint-End Turnover

“…Characterization of lower luminosity galaxies can give us insight into the efficiency of star formation in very low mass galaxies in the universe. There has been significant debate on whether this efficiency evolves with cosmic time since an influential analysis by Behroozi et al (2013), with some studies favoring efficient early star formation (e.g., Harikane et al 2016;Marone et al 2018) and others disfavoring it (e.g., Harikane et al 2018Harikane et al , 2021Stefanon et al 2021Stefanon et al , 2022. Ascertaining what the efficiency of star formation is in low mass galaxies (e.g., Muñoz & Loeb 2011, Finlator et al 2017) should provide us with valuable insight into similar star formation processes in galaxies at the earliest times (z ≥ 12: Wise et al 2014;Barrow et al 2017;Harikane et al 2021) as well as providing constraints on the nature of dark matter (e.g., Dayal et al 2017;Menci et al 2018).…”