Galaxy Build-up in the first 1.5 Gyr of Cosmic History: Insights from the Stellar Mass Function at $z\sim4-9$ from JWST NIRCam Observations

Understand

Combining the public JWST/NIRCam imaging programs CEERS, PRIMER and JADES, spanning a total area of $\sim500\,{\rm arcmin}^2$, we obtain a sample of $>$30,000 galaxies at $z_{\rm phot}\sim4-9$ that allows us to perform a complete, rest-optical selected census of the galaxy population at $z>3$.

• Comparing the stellar mass $M_*$ and the UV-slope $\beta$ distributions between JWST- and HST-selected samples, we generally find very good agreement and no significant biases.
• Nevertheless, JWST enables us to probe a new population of UV-red galaxies that was missing from previous HST-based Lyman Break Galaxy (LBG) samples.
• We measure galaxy stellar mass functions (SMFs) at $z\sim4-9$ down to limiting masses of $10^{7.5}-10^{8.5}\,{\rm M_\odot}$, finding steep low mass slopes over the entire redshift range, reaching values of $\alpha\approx-2$ at $z\gtrsim6$.