What the study found
The study found that, in a sample of massive galaxy clusters, the characteristic stellar mass in the cluster stellar mass function evolves only slightly from redshift 0.8 to 0.55, and that most measurable growth happens between redshift 0.55 and 0.2. The authors also report evidence that the stellar mass fraction in galaxies above 10^9.5 solar masses grows significantly over 0.2 < z < 0.8 after accounting for cluster halo growth.
Why the authors say this matters
The authors suggest this means most of the massive galaxy population in clusters, meaning galaxies with stellar mass above about 10^10.75 solar masses, is already in place by redshift 0.8. They conclude that later evolution is driven by late-time assembly processes.
What the researchers tested
The researchers studied 568 Sunyaev-Zel’dovich-selected galaxy clusters with masses greater than 2.9 × 10^14 solar masses and redshifts between 0.2 and 0.8, using data from ACT DR5 and deep photometry from DECaLS DR10. They built redshift- and cluster-mass-binned composite cluster stellar mass functions down to 10^9.5 solar masses, and measured cluster stellar mass fractions across the same redshift range.
What worked and what didn't
The characteristic stellar mass, M*, changed only marginally at 0.55 ≤ z < 0.8, with the main growth occurring at 0.2 < z < 0.55. The low-mass slope was flat at high redshift around z ~ 0.8 and became steeper at z < 0.55, which the authors associate with an abundance of massive galaxies in high-z clusters compared with low-z clusters. They also found a factor-of-2.5 growth in stellar mass fraction after accounting for halo mass growth.
What to keep in mind
This is the first analysis of the cluster stellar mass function for this cluster sample at this epoch, according to the abstract. The abstract does not describe additional limitations beyond the redshift, mass, and stellar-mass ranges studied.
Key points
- 568 massive galaxy clusters were analyzed over redshifts 0.2 to 0.8.
- The characteristic stellar mass changed only marginally from redshift 0.8 to 0.55.
- Most measurable stellar mass growth occurred between redshift 0.55 and 0.2.
- The stellar mass fraction in galaxies above 10^9.5 solar masses grew by a factor of 2.5 after halo growth was accounted for.
- The low-mass slope of the cluster stellar mass function was flat at high redshift and steeper at lower redshift.
Disclosure
- Research title:
- Cluster stellar mass growth is mostly established by redshift 0.8
- Authors:
- Damien C. Ragavan, Unnikrishnan Sureshkumar, Matt Hilton, John P. Hughes, Kavilan Moodley, Tony Mroczkowski, Bruce Partridge, Maria Salatino, Cristobál Sifón, Eve M. Vavagiakis, Edward J. Wollack
- Institutions:
- University of the Witwatersrand, University of Warsaw, University of KwaZulu-Natal, Rutgers, The State University of New Jersey, Institute of Space Sciences, Haverford College, Kavli Institute for Particle Astrophysics and Cosmology, Pontificia Universidad Católica de Valparaíso, Duke University, Cornell University, Goddard Space Flight Center
- Publication date:
- 2026-04-23
- OpenAlex record:
- View
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