The galaxy UV luminosity function at $\mathbf{z \simeq 11}$ from a suite of public JWST ERS, ERO and Cycle-1 programs (2304.14469v2)

Abstract: We present a new determination of the evolving galaxy UV luminosity function (LF) over the redshift range $9.5<z\<12.5$ based on a wide-area ($\>250$ arcmin$^2$) data set of JWST NIRCam near-infrared imaging assembled from thirteen public JWST surveys. Our relatively large-area search allows us to uncover a sample of 61 robust $z>9.5$ candidates detected at $\geq 8\sigma$, and hence place new constraints on the intermediate-to-bright end of the UV LF. When combined with our previous JWST+UltraVISTA results, this allows us to measure the form of the LF over a luminosity range corresponding to four magnitudes ($M_{1500}$). At these early times we find that the galaxy UV LF is best described by a double power-law function, consistent with results obtained from recent ground-based and early JWST studies at similar redshifts. Our measurements provide further evidence for a relative lack of evolution at the bright-end of the UV LF at $z=9-11$, but do favour a steep faint-end slope ($\alpha\leq-2$). The luminosity-weighted integral of our evolving UV LF provides further evidence for a gradual, smooth (exponential) decline in co-moving star-formation rate density ($\rho_{\mathrm{SFR}}$) at least out to $z\simeq12$, with our determination of $\rho_{\mathrm{SFR}}(z=11)$ lying significantly above the predictions of many theoretical models of galaxy evolution.

• The paper establishes a double power-law UV luminosity function at z≃11 using JWST imaging of 61 galaxies.
• It reveals a bright-end invariance from z=9 to z=11 and a steep faint-end slope (α ≤ -2) in the galaxy luminosity distribution.
• The findings suggest higher star-formation efficiencies than current models predict, prompting a re-evaluation of early galaxy evolution.

An Analysis of the Galaxy UV Luminosity Function at $z \simeq 11$

The paper by McLeod et al. presents an analysis of the ultraviolet (UV) luminosity function (LF) for galaxies in the high-redshift range of $9.5 < z < 12.5$, utilizing an extensive dataset from various public JWST surveys. This extensive and meticulous work adds significant insights into the understanding of the early universe, particularly the formation and evolution of galaxies.

The paper leverages JWST's NIRCam near-infrared imaging to detect 61 robust galaxy candidates above the $\geq 8\sigma$ detection threshold. This large dataset allows the authors to precisely define the UV LF across a luminosity range of four magnitudes ($M_{1500}$), which represents a considerable advancement over previous analyses conducted with the Hubble Space Telescope. The research suggests that at these redshifts, the UV LF is best described by a double power-law function, a conclusion consistent with prior findings from early JWST results and ground-based observations.

Significantly, this paper reports a relative invariance in the bright-end of the UV LF from $z = 9$ to $z = 11$, supporting theories of diminished evolution in star formation rates at these higher luminosities. Conversely, a steep faint-end slope ($\alpha \leq -2$) is favored, indicating rapid changes in star-forming activities within less luminous galaxies during this epoch. Moreover, the inclusion of data beyond $z=12$ provides further evidence for an exponential decline in the co-moving star-formation rate density, $\rho_{\mathrm{SFR}}$, with increasing redshift.

McLeod et al.'s determination of the $\rho_{\mathrm{SFR}}$ at $z=11$ stands out by lying significantly above the predictions of many current theoretical models of galaxy evolution. This suggests either a need to revise these models or an indication of higher efficiency in star-forming processes at this early cosmic time, a finding that challenges and refines our understanding of the universe's evolution. It also prompts further exploration into whether current models adequately account for the impact of dust attenuation and other factors influencing star-formation rates.

This detailed examination of high-redshift galaxies underscores JWST's capability in advancing knowledge about the universe's infancy. It invites future research focusing on gaining deeper high-redshift data, potentially with upcoming JWST Cycles, to further refine the models of these early cosmic times. Additionally, the findings have practical implications for understanding the emergence of structure in the universe, highlighting areas for theoretical and observational advancements.

In conclusion, the work by McLeod et al. is a pivotal reference in astrophysics, providing robust constraints on the galaxy UV LF at $z \simeq 11$. It opens numerous avenues for future research in both observational and theoretical domains, contributing substantially to our comprehension of galaxy formation and evolution during the early universe. This research solidifies the foundation for evolving models that describe the dynamics of star-formation and galaxy evolution beyond $z > 9$.