The Highest-redshift Balmer Breaks as a Test of ΛCDM

Journal article

Recent studies have reported tension between the presence of luminous, high-redshift galaxies and the halo mass functions predicted by standard cosmology. Here, an improved test is proposed using the presence of high-redshift Balmer breaks to probe the formation of early 104–105 M ⊙ baryonic minihalos. Unlike previous tests, this does not depend upon the mass-to-light ratio and has only a slight dependence upon the metallicity, stellar initial mass function, and star formation history, which are all weakly constrained at high redshift. We show that the strongest Balmer breaks allowed at z = 9 using the simplest ΛCDM cosmological model would allow a D 4000 as high as 1.26 under idealized circumstances and D 4000 ≤ 1.14 including realistic feedback models. Since current photometric template fitting to JWST sources infers the existence of stronger Balmer breaks out to z ≳ 11, upcoming spectroscopic follow-up will either demonstrate those templates are invalid at high redshift or imply new physics beyond “vanilla” ΛCDM.

Authors: Steinhardt, CL; Sneppen, A; Clausen, T; Katz, H; Rey, MP

• Publication status: Published
• Peer review status: Peer reviewed
• Publisher: American Astronomical Society
• Journal: The Astrophysical Journal
• Volume: 967
• Issue: 2
• Article number: 172
• Publication date: 2024-05-30
• Acceptance date: 2024-03-28
• DOI: 10.3847/1538-4357/ad3afb
• EISSN: 1538-4357
• ISSN: 0004-637X
• Language: English
• Keywords: Galaxy spectroscopy; Galaxies; Quenched galaxies