A Virgo Environmental Survey Tracing Ionised Gas Emission (VESTIGE)

XIX. The discovery of a spectacular 230 kpc Hα tail following NGC 4569 in the Virgo cluster

¹ Department of Physics & Astronomy, University of Alabama in Huntsville 301 Sparkman Dr NW Huntsville AL 35899, USA
² Aix Marseille Université, CNRS, LAM (Laboratoire d’Astrophysique de Marseille) UMR 7326 13388 Marseille, France
³ Canada-France-Hawaii Telescope 65-1238 Mamalahoa Highway Kamuela HI 96743, USA
⁴ INAF – Osservatorio Astronomico di Cagliari Via della Scienza 5 09047 Selargius (CA), Italy
⁵ School of Physics and Electronic Science, Guizhou Normal University, Guiyang 550001, PR China; Guizhou Provincial Key Laboratory of Radio Astronomy and Data Processing, Guizhou Normal University Guiyang 550001, PR China
⁶ Center for Astrophysics | Harvard & Smithsonian 60 Garden St. Cambridge MA 02138, USA
⁷ Department of Astronomy and Virginia Institute for Theoretical Astronomy, University of Virginia P.O. Box 400325 Charlottesville VA 22904, USA
⁸ Dipartimento di Fisica G. Occhialini, Università degli Studi di Milano Bicocca Piazza della Scienza 3 I-20126 Milano, Italy
⁹ INAF-Osservatorio Astronomico di Brera via Brera 28 I-20121 Milano, Italy
¹⁰ Research Center for Astronomical Computing, Zhejiang Laboratory Hangzhou 311100, PR China
¹¹ Department of Astrophysics, University of Vienna Türkenschanzstrasse 17 1180 Vienna, Austria
¹² SISSA – International School for Advanced Studies Via Bonomea 265 34136 Trieste, Italy
¹³ Laboratoire d’Astrophysique de Bordeaux, Univ. Bordeaux, CNRS, B18N, allée Geoffroy Saint-Hilaire 33615 Pessac, France
¹⁴ AIM, CEA, CNRS, Université Paris-Saclay, Université Paris Diderot, Sorbonne Paris Cité, Observatoire de Paris, PSL University F-91191 Gif-sur-Yvette Cedex, France
¹⁵ National Research Council of Canada, Herzberg Astronomy and Astrophysics 5071 West Saanich Road Victoria BC V9E 2E7, Canada
¹⁶ Université de Strasbourg, CNRS, Observatoire astronomique de Strasbourg, UMR 7550 67000 Strasbourg, France

^★ Corresponding author: This email address is being protected from spambots. You need JavaScript enabled to view it.

Received: 3 July 2025
Accepted: 30 November 2025

Abstract

Context. Galaxies fly inside galaxy clusters and ram pressure by the intracluster medium (ICM) can remove a large amount of the interstellar medium (ISM) from the galaxy, and deposit the gas in the ICM. The ISM decoupled from the host galaxy leaves a long trail following the moving galaxy. Such long trails track galaxy motions and they can be detected with sensitive data in Hα.

Aims. We study the Hα tail trailing NGC 4569 in the Virgo cluster.

Methods. The initial discovery was made with the deep Hα imaging data with CFHT from the VESTIGE project. The follow-up spectroscopic observations were carried out with APO/DIS, MMT/Binospec, and CFHT/SITELLE.

Results. Aside from the known 80 kpc Hα tail downstream of NGC 4569, the deep Hα imaging data allow the Hα tail detected to at least 230 kpc from the galaxy. More importantly, we confirmed the Hα clumps implied from the imaging data with spectroscopic data. The Hα clumps show a smooth radial velocity gradient across ∼1300 km/s, eventually reaching the velocity of the cluster.

Conclusions. For the first time, this discovery offers a view of the full deceleration process of the stripped ISM. This discovery also showcases the potential with wide-field Hα survey on galaxy clusters to discover intracluster optical emission-line clouds originated from cluster galaxies. These clouds provide kinematic tracers to the infall history of cluster galaxies and the turbulence in the ICM. They also serve as excellent multi-phase objects for studying the classical cloud-crushing problem and other important physical processes.