Stacy McGaugh takes a moment to emphasize that when it comes to the timing of galaxy formation, MOND was right and the ΛCDM model was profoundly wrong.
Our paper on massive galaxies at high redshift is out in the Astrophysical Journal today. This is a scientific analysis of the JWST data that has accumulated to date as it pertains to testing galaxy formation as hypothesized by LCDM and MOND. That massive galaxies are observed to form early (z > 10) corroborates the long standing prediction of MOND, going back to Sanders (1998):Objects of galaxy mass are the first virialized objects to form (by z=10), and larger structure develops rapidlyThe contemporaneous LCDM prediction from Mo, Mao, & White (1998) – a touchstone of galaxy formation theory with nearly 2,000 citations – waspresent-day disc [galaxies] were assembled recently (at z<=1).This is not what JWST sees, as morphologically mature spiral galaxies are present to at least z = 6 (Ferreira et al 2024). More generally, LCDM was predicted to take a long time to build up the stellar mass of large galaxies, with the median time to reach half the final stellar mass being about half a Hubble time (seven billion years, give or take). In contrast, JWST has now observed many galaxies that meet this benchmark in the first billion years. That was not expected to happen.
From here.
As an aside, I strongly favor naming the critical acceleration of MOND, usually notated a0, Milgrom's Constant, after Mordehai Milgrom, who devised MOND in 1983.
Discovery of a Rare Group of Dwarf Galaxies in the Local Universe
ReplyDeleteSanjaya Paudel 1 , Cristiano G. Sabiu 2 , Suk-Jin Yoon 1 , Pierre-Alain Duc 3 , Jaewon Yoo 4 , and Oliver Müller 5
1 Department of Astronomy & Center for Galaxy Evolution Research, Yonsei University, Seoul 03722, Republic of Korea; sjyoon0691@yonsei.ac.kr
2 Natural Science Research Institute (NSRI), University of Seoul, Seoul 02504, Republic of Korea
3 Université de Strasbourg, CNRS, Observatoire astronomique de Strasbourg, UMR 7550, F-67000 Strasbourg, France
4 Quantum Universe Center, Korea Institute for Advanced Study (KIAS), 85 Hoegiro, Dongdaemun-gu, Seoul 02455, Republic of Korea
5 Laboratoire d’astrophysique, École Polytechnique Fédérale de Lausanne (EPFL), Observatoire, 1290 Versoix, Switzerland
Received 2024 September 15; revised 2024 October 22; accepted 2024 November 5; published 2024 November 19
Abstract
We report the discovery of a rare isolated group of five dwarf galaxies located at z = 0.0086 (D = 36 Mpc). All member
galaxies are star forming, blue, and gas rich, with g − r indices ranging from 0.2 to 0.6 mag, and two of them show signs
of ongoing mutual interaction. The most massive member of the group has a stellar mass that is half of the Small
Magellanic Cloud stellar mass, and the median stellar mass of the group members is 7.87 × 107 M☉. The derived total
dynamical mass of the group is Mdyn = 6.02 × 1010 M☉, whereas its total baryonic mass (stellar + H I) is 2.6 × 109 M☉,
which gives us the dynamical to baryonic mass ratio of 23. Interestingly, all galaxies found in the group are aligned along
a straight line in the plane of the sky. The observed spatial extent of the member galaxies is 154 kpc, and their relative line-
of-sight velocity span is within 75 km s−1
. Using the spatially resolved optical spectra provided by the Dark Energy
Spectroscopic Instrument early data release, we find that three group members share a common rotational direction. With
these unique properties of the group and its member galaxies, we discuss the possible importance of such a system in the
formation and evolution of dwarf galaxy groups and in testing the theory of large-scale structure formation.
Unified Astronomy Thesaurus concepts: Interacting galaxies (802); Dwarf galaxies (416); Galaxy groups (597)
1. Introduction
The Lambda cold dark matter (ΛCDM) model is successful in
explaining the large-scale structure of the Universe, but it
encounters difficulties with explaining many aspects of dwarf
galaxies (S. D. M. White & M. J. Rees 1978; C. S. Frenk &