Has JWST Already Falsified Dark-matter-driven Galaxy Formation?

Abstract

The James Webb Space Telescope (JWST) discovered several luminous high-redshift galaxy candidates with stellar masses of M * ≳ 109 M ⊙ at photometric redshifts z phot ≳ 10, which allows to constrain galaxy and structure formation models. For example, Adams et al. identified the candidate ID 1514 with log 10 ( M * / M ⊙ ) = 9.8 − 0.2 + 0.2 located at z phot = 9.85 − 0.12 + 0.18 and Naidu et al. found even more distant candidates labeled as GL-z11 and GL-z13 with log 10 ( M * / M ⊙ ) = 9.4 − 0.3 + 0.3 at z phot = 10.9 − 0.4 + 0.5 and log 10 ( M * / M ⊙ ) = 9.0 − 0.4 + 0.3 at z phot = 13.1 − 0.7 + 0.8 , respectively. Assessing the computations of the IllustrisTNG (TNG50-1 and TNG100-1) and EAGLE projects, we investigate if the stellar mass buildup as predicted by the ΛCDM paradigm is consistent with these observations assuming that the early JWST calibration is correct and that the candidates are indeed located at z ≳ 10. Galaxies formed in the ΛCDM paradigm are by more than an order of magnitude less massive in stars than the observed galaxy candidates implying that the stellar mass buildup is more efficient in the early universe than predicted by the ΛCDM models. This in turn would suggest that structure formation is more enhanced at z ≳ 10 than predicted by the ΛCDM framework. We show that different star formation histories could reduce the stellar masses of the galaxy candidates alleviating the tension. Finally, we calculate the galaxy-wide initial mass function (gwIMF) of the galaxy candidates assuming the integrated galaxy IMF theory. The gwIMF becomes top-heavy for metal-poor star-forming galaxies decreasing therewith the stellar masses compared to an invariant canonical IMF.

Can Cosmological Simulations Reproduce the Spectroscopically Confirmed Galaxies Seen at z ≥ 10?

“…As future observations better constrain the stellar mass function at z ∼ 11, this tension may strengthen or disappear. If objects as massive as those seen by Labbe et al (2022), Adams et al (2023), andNaidu et al (2022a) are confirmed to be common, with spectroscopic redshifts of z > 10, this would imply a serious problem with existing ΛCDM and galaxy formation theory (Boylan-Kolchin 2022; Haslbauer et al 2022;Lovell et al 2023). In order to be in tension with all models for galaxy formation in ΛCDM (by implying galaxy star formation efficiencies >100%), the number density of M * = 10 9 M e galaxies at z ∼ 11 would need to be more than 3 orders of magnitude higher than what is implied by the JADES-GS-z11-0 detection.…”

“…As Boylan-Kolchin (2022) showed, if the comoving number density of galaxies at z = 10 with M * > 10 10 M e is as high as can be estimated from Labbe et al (2022), it would be a significant challenge for ΛCDM, analogous to Haldane's "fossil rabbits in the Precambrian" (Harvey et al 1996). Haslbauer et al (2022) have shown that the observations of galaxies with high stellar mass (M * > 10 9 ) at high redshift z  10 from Adams et al (2023), Labbe et al (2022), Naidu et al (2022a), andNaidu et al (2022b) are in extreme tension with the simulation predictions of EAGLE (Schaye et al 2015), TNG50, and TNG100 (Pillepich et al 2018a;Nelson et al 2019a). These authors warn, however, that spectroscopic confirmation of redshifts is needed before final conclusions can be reached: these tensions all rest on the estimations of stellar masses provided by SED fitting and critically, on the distance estimates themselves.…”

“…The first sets of detections reported (Naidu et al 2022a;Finkelstein et al 2022;Labbe et al 2022;Adams et al 2023) have found galaxies with M * > 10 8 M e at z phot > 10. The most extreme of these examples, with M * > 10 10 M e at z phot > 10 have already been shown to be in strong tension with ΛCDM (Boylan-Kolchin 2022; Haslbauer et al 2022). These tensions have, however, been clouded by the large uncertainty in fitting photometric redshifts at such extreme distances (Naidu et al 2022b;Bouwens et al 2022;Kaasinen et al 2022).…”

The Cosmic Timeline Implied by the JWST High-redshift Galaxies

“…But not all of the halos and their baryonic content would necessarily have taken this long to condense. The more recent simulations (Yajima et al 2022;Keller et al 2022;Kannan et al 2022;Inayoshi et al 2022;Haslbauer et al 2022;Mirocha & Furlanetto 2023;Whitler et al 2023), in particular, show that the halos could have been distributed across this age, some appearing perhaps as early as ∼ 120 Myr after the big bang (more on this below).…”

“…The second concerns whether the dynamics of structure formation could account for the highly compressed timeline implied by these discoveries (for the most recent work on this topic, see Yajima et al 2022;Keller et al 2022;Kannan et al 2022;Inayoshi et al 2022;Haslbauer et al 2022;Mirocha & Furlanetto 2023;Whitler et al 2023). It is the dynamics, of course, coupled to the physical processes responsible for cooling the gas, that would have governed how quickly stars could condense and assemble into billion solar-mass structures.…”