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dc.contributor.authorHaslbauer, Moritz
dc.contributor.authorBanik, Indranil
dc.contributor.authorKroupa, Pavel
dc.contributor.authorWittenburg, Nils
dc.contributor.authorJavanmardi, Behnam
dc.identifier.citationHaslbauer , M , Banik , I , Kroupa , P , Wittenburg , N & Javanmardi , B 2022 , ' The high fraction of thin disk galaxies continues to challenge ΛCDM cosmology ' , Astrophysical Journal , vol. 925 , no. 2 , 183 .
dc.identifier.otherPURE: 277771096
dc.identifier.otherPURE UUID: e5cb0b7a-76a4-43de-9633-12f0e4a00863
dc.identifier.otherJisc: 75890273fa6145678ea4829afd551c53
dc.identifier.otherpublisher-id: apjac46ac
dc.identifier.othermanuscript: ac46ac
dc.identifier.otherother: aas33008
dc.identifier.otherORCID: /0000-0002-4123-7325/work/108118871
dc.identifier.otherWOS: 000751072700001
dc.identifier.otherScopus: 85125849191
dc.descriptionFunding: I.B. is supported by Science and Technology Facilities Council grant ST/V000861/1. He acknowledges support from an Alexander von Humboldt Foundation postdoctoral research fellowship (2018–2020) and the University of Bonn "Pathways to Research" program.en
dc.description.abstractAny viable cosmological framework has to match the observed proportion of early- and late-type galaxies. In this contribution, we focus on the distribution of galaxy morphological types in the standard model of cosmology (Lambda cold dark matter, ΛCDM). Using the latest state-of-the-art cosmological ΛCDM simulations known as Illustris, IllustrisTNG, and EAGLE, we calculate the intrinsic and sky-projected aspect ratio distribution of the stars in subhalos with stellar mass M* > 1010 M⊙ at redshift z = 0. There is a significant deficit of intrinsically thin disk galaxies, which however comprise most of the locally observed galaxy population. Consequently, the sky-projected aspect ratio distribution produced by these ΛCDM simulations disagrees with the Galaxy And Mass Assembly (GAMA) survey and Sloan Digital Sky Survey at ≥12.52σ (TNG50-1) and ≥14.82σ (EAGLE50) confidence. The deficit of intrinsically thin galaxies could be due to a much less hierarchical merger-driven build-up of observed galaxies than is given by the ΛCDM framework. It might also arise from the implemented sub-grid models, or from the limited resolution of the above-mentioned hydrodynamical simulations. We estimate that an 85 times better mass resolution realization than TNG50-1 would reduce the tension with GAMA to the 5.58σ level. Finally, we show that galaxies with fewer major mergers have a somewhat thinner aspect ratio distribution. Given also the high expected frequency of minor mergers in ΛCDM, the problem may be due to minor mergers. In this case, the angular momentum problem could be alleviated in Milgromian dynamics because of a reduced merger frequency arising from the absence of dynamical friction between extended dark matter halos.
dc.relation.ispartofAstrophysical Journalen
dc.rightsCopyright © 2022. The Author(s). Original content from this work may be used under the terms of the Creative Commons Attribution 4.0 licence. Any further distribution of this work must maintain attribution to the author(s) and the titleof the work, journal citation and DOI.en
dc.subjectGalaxies and Cosmologyen
dc.subjectQB Astronomyen
dc.subjectQC Physicsen
dc.titleThe high fraction of thin disk galaxies continues to challenge ΛCDM cosmologyen
dc.typeJournal articleen
dc.contributor.sponsorScience & Technology Facilities Councilen
dc.description.versionPublisher PDFen
dc.contributor.institutionUniversity of St Andrews. School of Physics and Astronomyen
dc.description.statusPeer revieweden

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