University of Oulu

La Marca, A., Iodice, E., Cantiello, M., Forbes, D. A., Rejkuba, M., Hilker, M., Arnaboldi, M., Greggio, L., Spiniello, C., Mieske, S., Venhola, A., Spavone, M., D’Ago, G., Raj, M. A., Ragusa, R., Mirabile, M., Rampazzo, R., Peletier, R., Paolillo, M., … Schipani, P. (2022). Galaxy populations in the Hydra I cluster from the VEGAS survey: II. The ultra-diffuse galaxy population. Astronomy & Astrophysics, 665, A105.

Galaxy populations in the Hydra I cluster from the VEGAS survey

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Author: La Marca, Antonio1,2,3; Iodice, Enrichetta1; Cantiello, Michele4;
Organizations: 1INAF – Astronomical Observatory of Capodimonte, Salita Moiariello 16, 80131 Naples, Italy
2Kapteyn Institute, University of Groningen, Landleven 12, 9747 AD Groningen, The Netherlands
3University of Naples “Federico II”, C.U. Monte Sant’Angelo, Via Cinthia, 80126 Naples, Italy
4INAF – Astronomical Observatory of Abruzzo, Via Maggini, 64100 Teramo, Italy
5Centre for Astrophysics & Supercomputing, Swinburne University of Technology, Hawthorn, VIC 3122, Australia
6European Southern Observatory, Karl–Schwarzschild-Strasse 2, 85748 Garching bei München, Germany
7INAF – Osservatorio Astronomico di Padova, Vicolo dell’Osservatorio 5, 35122 Padova, Italy
8Department of Physics, University of Oxford, Denys Wilkinson Building, Keble Road, Oxford OX1 3RH, UK
9European Southern Observatory, Alonso de Cordova 3107, Vitacura, Santiago, Chile
10Space Physics and Astronomy Research Unit, University of Oulu, PO Box 3000 90014 Oulu, Finland
11Instituto de Astrofísica, Facultad de Física, Pontificia Universidad Católica de Chile, Av. Vicuña Mackenna 4860, 7820436 Macul, Santiago, Chile
12INAF – Astronomical Observatory of Rome, Via Frascati, 33, 00078 Monte Porzio Catone, Rome, Italy
13INAF – Astronomical Observatory of Padova, Via dell’Osservatorio 8, 36012 Asiago, (VI), Italy
Format: article
Version: published version
Access: open
Online Access: PDF Full Text (PDF, 20.4 MB)
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Language: English
Published: EDP Sciences, 2022
Publish Date: 2023-06-28


In this work, we extend the catalog of low-surface brightness (LSB) galaxies, including ultra-diffuse galaxy (UDG) candidates, within ≈0.4Rvir of the Hydra I cluster of galaxies based on deep images from the VST Early-type GAlaxy Survey (VEGAS). The new galaxies were found by applying an automatic detection tool and carrying out additional visual inspections of g and r band images. This led to the detection of 11 UDGs and 8 more LSB galaxies. For all of them, we assessed the cluster membership using the color–magnitude relation derived for early-type giant and dwarf galaxies in Hydra I. The UDGs and new LSB galaxies found in Hydra I span a wide range of central surface brightness (22.7 ≲ μ0, g ≲ 26.5 mag arcsec⁻²), effective radius (0.6 ≲ Re ≲ 4.0 kpc), and color (0.4 ≤ g − r ≤ 0.9 mag), and have stellar masses in the range ∼5 × 10⁶ − 2 × 10⁸ M⊙. The 2D projected distribution of both galaxy types is similar to the spatial distribution of dwarf galaxies, with over-densities in the cluster core and north of the cluster center. They have similar color distribution and comparable stellar masses to the red dwarf galaxies. Based on photometric selection, we identify a total of nine globular cluster (GC) candidates associated to the UDGs and four to the LSB galaxies, with the highest number of candidates in an individual UDG being three. We find that there are no relevant differences between dwarfs, LSB galaxies, and UDGs: the structural parameters (i.e., surface brightness, size, color, and n-index) and GC content of the three classes have similar properties and trends. This finding is consistent with UDGs being the extreme LSB tail of the size–luminosity distribution of dwarfs in this environment.

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Series: Astronomy and astrophysics
ISSN: 0004-6361
ISSN-E: 1432-0746
ISSN-L: 0004-6361
Volume: 665
Article number: A105
DOI: 10.1051/0004-6361/202142367
Type of Publication: A1 Journal article – refereed
Field of Science: 115 Astronomy and space science
Funding: ALM acknowledges financial support from the INAF-OAC funds. Authors acknowledge financial support from the VST INAF funds. MC acknowledges financial support from MIUR (PRIN 2017 grant 20179ZF5KS). CS is supported by an ‘Hintze Fellow’ at the Oxford Centre for Astrophysical Surveys, which is funded through generous support from the Hintze Family Charitable Foundation. GD acknowledges support from FONDECYT REGULAR 1200495, and ANID project Basal FB-210003.
Copyright information: © A. La Marca et al. 2022. Open Access article, published by EDP Sciences, under the terms of the Creative Commons Attribution License (, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.