2024-08-26 テキサス大学オースチン校(UT Austin)
＜関連情報＞
- https://news.utexas.edu/2024/08/26/early-galaxies-were-not-too-big-for-their-britches-after-all/
- https://iopscience.iop.org/article/10.3847/1538-3881/ad57c1
CEERSによるz = 4-8の大質量銀河の体積密度の浅い進化の証拠 Evidence for a Shallow Evolution in the Volume Densities of Massive Galaxies at z = 4–8 from CEERS
Katherine Chworowsky, Steven L. Finkelstein, Michael Boylan-Kolchin, Elizabeth J. McGrath, Kartheik G. Iyer, Casey Papovich, Mark Dickinson, Anthony J. Taylor, L. Y. Aaron Yung, Pablo Arrabal Haro
The Astronomical Journal Published: 2024 August 26
DOI:10.3847/1538-3881/ad57c1
Abstract
We analyze the evolution of massive (log10[M⋆/M⊙] > 10) galaxies at z ∼ 4–8 selected from JWST Cosmic Evolution Early Release Survey (CEERS). We infer the physical properties of all galaxies in the CEERS NIRCam imaging through spectral energy distribution (SED) fitting with dense basis to select a sample of high-redshift massive galaxies. Where available we include constraints from additional CEERS observing modes, including 18 sources with MIRI photometric coverage, and 28 sources with spectroscopic confirmations from NIRSpec or NIRCam WFSS. We sample the recovered posteriors in stellar mass from SED fitting to infer the volume densities of massive galaxies across cosmic time, taking into consideration the potential for sample contamination by active galactic nuclei. We find that the evolving abundance of massive galaxies tracks expectations based on a constant baryon conversion efficiency in dark matter halos for z ∼ 4–8. At higher redshifts, we observe an excess abundance of massive galaxies relative to this simple model, resulting in a shallower decline of observed volume densities of massive galaxies. These higher abundances can be explained by modest changes to star formation physics and/or the efficiencies with which star formation occurs in massive dark matter halos, and are not in tension with modern cosmology.
