University of Oulu

Janz, J., Salo, H., Su, A. H., & Venhola, A. (2021). Signatures of quenching in dwarf galaxies in local galaxy clusters. Astronomy & Astrophysics, 647, A80.

Signatures of quenching in dwarf galaxies in local galaxy clusters : a comparison of the galaxy populations in the Virgo and Fornax clusters

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Author: Janz, Joachim1,2; Salo, Heikki2; Su, Alan H.2;
Organizations: 1Finnish Centre of Astronomy with ESO (FINCA), University of Turku, Vesilinnantie 5, 20014 Turku, Finland
2Space Physics and Astronomy Research Unit, University of Oulu, PO Box 3000, 90014 Oulu, Finland
Format: article
Version: published version
Access: open
Online Access: PDF Full Text (PDF, 1.2 MB)
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Language: English
Published: EDP Sciences, 2021
Publish Date: 2021-09-02


Context: The transformation of late-type galaxies has been suggested as the origin of early-type dwarf galaxies (typically M ≤ 10⁹ M) in galaxy clusters. Based on deep images, Venhola and colleagues analysed correlations between colour and surface brightness for galaxies in the Fornax cluster binned by luminosity or stellar mass. In the bins with M < 10⁸ M, the authors identified a correlation of redness with fainter surface brightness and interpreted it as a consequence of the quenching of star formation by ram pressure stripping in the dwarf galaxies.

Aims: This study carries out a similar analysis for the Virgo cluster. The analysis for both clusters is then used to compare the Virgo and Fornax clusters, for which the ram pressure is expected to have different strengths. The purpose of this is to scrutinise the ram pressure interpretation from the other study and search for differences between the clusters that reflect the different ram pressure efficiencies, which would either support or weaken this interpretation. Ultimately, this could help weigh the importance of ram pressure stripping relative to other transformative processes in the shaping of the dominant early-type dwarf galaxy population.

Methods: We extend the analysis of colour versus surface brightness binned by stellar mass to higher masses and a wider range of optical colours. The results, in particular at low stellar mass, are compared to predictions of stellar evolution models. Benefitting from larger sample sizes, we also analyse late- and early-type galaxies separately. This analysis is carried out for the Virgo and Fornax clusters, and the colour versus surface brightness relation, as well as other properties of the two clusters’ galaxy populations, are compared.

Results: While the colour–surface brightness diagrams are remarkably similar for the two clusters, only the low-mass late-type galaxies are found to have slopes consistent with a fading and reddening following the quenching of star formation. For the early-type galaxies, there are no (or only weak) correlations between colour and surface brightness in all mass bins. Early- and late-type galaxies in both clusters have comparable sizes below a stellar mass of M ≲ 10⁸ M. The colour and size scaling relations are very similar for the Virgo and Fornax clusters. However, Virgo features a lower fraction of early-type or red galaxies despite its higher mass.

Conclusions: The similarity of early-type dwarfs and low-mass late types in size at the masses M ≲ 10⁸ M as well as the overall consistency of the colour–surface brightness correlation with fading stellar populations support a scenario of transformation via the quenching of star formation, for example by gas removal. However, the lack of this imprint of an ageing stellar population on the early-type dwarfs themselves calls for some additional explanation. Finally, the Virgo cluster is an atypical cluster with a comparably low fraction of quiescent early-type galaxies at all galaxy masses despite its large cluster mass.

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Series: Astronomy and astrophysics
ISSN: 0004-6361
ISSN-E: 1432-0746
ISSN-L: 0004-6361
Volume: 647
Article number: A80
DOI: 10.1051/0004-6361/202039408
Type of Publication: A1 Journal article – refereed
Field of Science: 115 Astronomy and space science
Funding: We acknowledge financial support from the European Union’s Horizon 2020 research and innovation program under the Marie Skłodowska-Curie grant agreement No. 721463 to the SUNDIAL ITN network. HS and AV are also supported by the Academy of Finland grant No. 297738. AV acknowledges the financial support from Emil Aaltonen foundation. JJ expresses his thanks to Reynier Peletier for organizing the Low Surface Brightness Galaxies workshop in 2019 in Groningen, where initial ideas for this article originated.
EU Grant Number: (721463) SUNDIAL - SUrvey Network for Deep Imaging Analysis and Learning
Academy of Finland Grant Number: 297738
Detailed Information: 297738 (Academy of Finland Funding decision)
Copyright information: © ESO 2021.