An evolutionary continuum from nucleated dwarf galaxies to star clusters

Kaixiang Wang; Eric W Peng; Chengze Liu; J Christopher Mihos; Patrick Côté; Laura Ferrarese; Matthew A Taylor; John P Blakeslee; Jean-Charles Cuillandre; Pierre-Alain Duc; Puragra Guhathakurta; Stephen Gwyn; Youkyung Ko; Ariane Lançon; Sungsoon Lim; Lauren A MacArthur; Thomas Puzia; Joel Roediger; Laura V Sales; Rubén Sánchez-Janssen; Chelsea Spengler; Elisa Toloba; Hongxin Zhang; Mingcheng Zhu

doi:10.1038/s41586-023-06650-z

An evolutionary continuum from nucleated dwarf galaxies to star clusters

Nature. 2023 Nov;623(7986):296-300. doi: 10.1038/s41586-023-06650-z. Epub 2023 Nov 8.

Authors

Kaixiang Wang^{1

2}, Eric W Peng³, Chengze Liu^{4

5}, J Christopher Mihos⁶, Patrick Côté⁷, Laura Ferrarese⁷, Matthew A Taylor⁸, John P Blakeslee⁹, Jean-Charles Cuillandre¹⁰, Pierre-Alain Duc¹¹, Puragra Guhathakurta¹², Stephen Gwyn⁷, Youkyung Ko¹³, Ariane Lançon¹¹, Sungsoon Lim¹⁴, Lauren A MacArthur¹⁵, Thomas Puzia¹⁶, Joel Roediger⁷, Laura V Sales¹⁷, Rubén Sánchez-Janssen¹⁸, Chelsea Spengler¹⁶, Elisa Toloba¹⁹, Hongxin Zhang^{20

21}, Mingcheng Zhu^{22

23}

Affiliations

¹ Department of Astronomy, Peking University, Beijing, China. kaixiang.wang@pku.edu.cn.
² Kavli Institute for Astronomy and Astrophysics, Peking University, Beijing, China. kaixiang.wang@pku.edu.cn.
³ NSF's NOIRLab, Tucson, AZ, USA. eric.peng@noirlab.edu.
⁴ Department of Astronomy, School of Physics and Astronomy, and Shanghai Key Laboratory for Particle Physics and Cosmology, Shanghai Jiao Tong University, Shanghai, China. czliu@sjtu.edu.cn.
⁵ Tsung-Dao Lee Institute, Shanghai Jiao Tong University, Shanghai, China. czliu@sjtu.edu.cn.
⁶ Department of Astronomy, Case Western Reserve University, Cleveland, OH, USA.
⁷ Herzberg Astronomy and Astrophysics Research Centre, National Research Council of Canada, Victoria, British Columbia, Canada.
⁸ Department of Physics and Astronomy, University of Calgary, Calgary, Alberta, Canada.
⁹ NSF's NOIRLab, Tucson, AZ, USA.
¹⁰ AIM Paris Saclay, CNRS/INSU, CEA/Irfu, Université Paris Diderot, Orme des Merisiers, Gif-sur-Yvette Cedex, France.
¹¹ Université de Strasbourg, CNRS, Observatoire astronomique de Strasbourg, UMR 7550, Strasbourg, France.
¹² UCO/Lick Observatory, Department of Astronomy and Astrophysics, University of California Santa Cruz, Santa Cruz, CA, USA.
¹³ Korea Astronomy and Space Science Institute, 776 Daedeok-daero, Yuseong-Gu, Daejeon, Republic of Korea.
¹⁴ Department of Astronomy, Yonsei University, 50 Yonsei-ro, Seodaemun-gu, Seoul, Republic of Korea.
¹⁵ Department of Astrophysical Sciences, Princeton University, Princeton, NJ, USA.
¹⁶ Institute of Astrophysics, Pontificia Universidad Católica de Chile, Av. Vicuña Mackenna 4860, 7820436 Macul, Santiago, Chile.
¹⁷ Department of Physics and Astronomy, University of California, Riverside, CA, USA.
¹⁸ UK Astronomy Technology Centre, Royal Observatory Edinburgh, Blackford Hill, Edinburgh, UK.
¹⁹ Department of Physics and Astronomy, University of the Pacific, Stockton, CA, USA.
²⁰ School of Astronomy and Space Science, University of Science and Technology of China, Hefei, China.
²¹ CAS Key Laboratory for Research in Galaxies and Cosmology, Department of Astronomy, University of Science and Technology of China, Hefei, China.
²² Department of Astronomy, Peking University, Beijing, China.
²³ Kavli Institute for Astronomy and Astrophysics, Peking University, Beijing, China.

PMID: 37938704
DOI: 10.1038/s41586-023-06650-z

Abstract

Systematic studies^1-4 have revealed hundreds of ultra-compact dwarf galaxies (UCDs⁵) in the nearby Universe. With half-light radii r_h of approximately 10-100 parsecs and stellar masses M_*≈ 10⁶-10⁸solar masses, UCDs are among the densest known stellar systems⁶. Although similar in appearance to massive globular clusters⁷, the detection of extended stellar envelopes^4,8,9, complex star formation histories¹⁰, elevated mass-to-light ratio^11,12 and supermassive black holes^13-16 suggest that some UCDs are remnant nuclear star clusters¹⁷ of tidally stripped dwarf galaxies^18,19, or even ancient compact galaxies²⁰. However, only a few objects have been found in the transient stage of tidal stripping^21,22, and this assumed evolutionary path¹⁹ has never been fully traced by observations. Here we show that 106 galaxies in the Virgo cluster have morphologies that are intermediate between normal, nucleated dwarf galaxies and single-component UCDs, revealing a continuum that fully maps this morphological transition and fills the 'size gap' between star clusters and galaxies. Their spatial distribution and redder colour are also consistent with stripped satellite galaxies on their first few pericentric passages around massive galaxies²³. The 'ultra-diffuse' tidal features around several of these galaxies directly show how UCDs are forming through tidal stripping and that this evolutionary path can include an early phase as a nucleated ultra-diffuse galaxy^24,25. These UCDs represent substantial visible fossil remnants of ancient dwarf galaxies in galaxy clusters, and more low-mass remnants probably remain to be found.