A Virgo Environmental Survey Tracing Ionised Gas Emission (VESTIGE)

X. Formation of a red ultra-diffuse galaxy and an almost dark galaxy during a ram-pressure stripping event^⋆,⋆⋆

¹ Aix Marseille Univ, CNRS, CNES, LAM, Marseille, France
e-mail: junais.madathodika@lam.fr; samuel.boissier@lam.fr; lessandro.boselli@lam.fr
² Centro de Astronomá (CITEVA), Universidad de Antofagasta, Avenida Angamos 601, Antofagasta, Chile
³ Dipartimento di Fisica G. Occhialini, Università degli Studi di Milano-Bicocca, Piazza della Scienza 3, 20126 Milano, Italy
⁴ AIM, CEA, CNRS, Université Paris-Saclay, Université Paris Diderot, 91191 Gif-sur-Yvette, France
⁵ NRC Herzberg Astronomy and Astrophysics, 5071 West Saanich Road, Victoria, BC V9E 2E7, Canada
⁶ University of Tampa, 401 West Kennedy Boulevard, Tampa, FL 33606, USA
⁷ Department of Astronomy, Peking University, Beijing 100871, PR China
⁸ Kavli Institute of Astronomy and Astrophysics, Peking University, Beijing 100871, PR China
⁹ Department of Astrophysics, University of Vienna, Türkenschanzstrasse 17, 1180 Vienna, Austria
¹⁰ INAF – Osservatorio Astronomico di Brera, via Brera 28, 20159 Milano, Italy
¹¹ Department of Physics and Astronomy, Stony Brook University, Stony Brook, NY 11794-3800, USA
¹² Institut d’Astrophysique de Paris, UMR7095 CNRS, Sorbonne Université, 98bis Bd. Arago, 75104 Paris, France

Received: 21 December 2020
Accepted: 16 March 2021

Abstract

Context. The evolution of galaxies depends on their interaction with the surrounding environment. Ultra-diffuse galaxies (UDGs) have been found in large numbers in clusters. We detected a few star-forming blobs in the VESTIGE survey, located at ∼5 kpc from a UDG, namely NGVS 3543, in association with an HI gas cloud AGC 226178, suggesting a recent interaction between this low-surface-brightness system and the surrounding cluster environment.

Aims. We use a complete set of multi-frequency data including deep optical, UV, and narrow-band Hα imaging and HI data to understand the formation process that gave birth to this peculiar system.

Methods. For this purpose, we measured (i) the multi-wavelength radial surface brightness profiles of NGVS 3543 and compared them to the predictions of spectro-photometric models of galaxy evolution in rich clusters; and (ii) the aperture photometry of the blue regions in the vicinity of NGVS 3543 in order to determine their age and stellar mass.

Results. Comparisons of the observations with evolutionary models indicate that NGVS 3543 has undergone a ram-pressure stripping that peaked ∼100 Myr ago, transforming a blue gas-rich UDG into a red gas-poor UDG. Star formation has taken place in the ram pressure stripped gas, the mass of which is ∼10⁸ M_⊙, forming star complexes with a typical age of ∼20 Myr and a stellar mass of ∼10⁴ M_⊙.

Conclusions. These results suggest that we are observing for the first time the ongoing transformation of a gas-rich UDG into a red and quiescent UDG under the effect of a ram-pressure stripping event. The same process could explain the lack of star-forming UDGs in rich environments observed in several nearby clusters.