James Webb Space Telescope Feed Post

Arxiv: CEERS Key Paper I: An Early Look into the First 500 Myr of Galaxy Formation with JWST Published: 11/10/2022 9:00:02 PM Updated: 11/4/2023 2:38:19 PM

Paper abstract: We present an investigation into the first 500 Myr of galaxy evolution fromthe Cosmic Evolution Early Release Science (CEERS) survey. CEERS, one of 13JWST ERS programs, targets galaxy formation from z~0.5 to z>10 using severalimaging and spectroscopic modes. We make use of the first epoch of CEERS NIRCamimaging, spanning 35.5 sq. arcmin, to search for candidate galaxies at z>9.Following a detailed data reduction process implementing several custom stepsto produce high-quality reduced images, we perform multi-band photometry acrossseven NIRCam broad and medium-band (and six Hubble broadband) filters focusingon robust colors and accurate total fluxes. We measure photometric redshiftsand devise a robust set of selection criteria to identify a sample of 26 galaxycandidates at z~9-16. These objects are compact with a median half-light radiusof ~0.5 kpc. We present an early estimate of the z~11 rest-frame ultraviolet(UV) luminosity function, finding that the number density of galaxies at M_UV ~-20 appears to evolve very little from z~9 to z~11. We also find that theabundance (surface density [arcmin^-2]) of our candidates exceeds nearly alltheoretical predictions. We explore potential implications, including that atz>10 star formation may be dominated by top-heavy initial mass functions, whichwould result in an increased ratio of UV light per unit halo mass, though acomplete lack of dust attenuation and/or changing star-formation physics mayalso play a role. While spectroscopic confirmation of these sources is urgentlyrequired, our results suggest that the deeper views to come with JWST shouldyield prolific samples of ultra-high-redshift galaxies with which to furtherexplore these conclusions.