ViCTORIA project: MeerKAT H I observations of the ram pressure stripped galaxy NGC 4523^⋆

¹ Aix-Marseille Univ., CNRS, CNES, LAM, Marseille, France
e-mail: alessandro.boselli@lam.fr
² Osservatorio Astronomico di Cagliari, via della Scienza 5, 09047 Selargius (CA), Italy
³ INAF – Istituto di Radioastronomia, via P. Gobetti 101, 40129 Bologna, Italy
⁴ Hamburger Sternwarte, University of Hamburg, Gojenbergsweg 112, 21029 Hamburg, Germany
⁵ Université de Strasbourg, CNRS, Observatoire Astronomique de Strasbourg, UMR 7550, 67000 Strasbourg, France
⁶ Universitá di Milano-Bicocca, piazza della scienza 3, 20100 Milano, Italy
⁷ INAF – Osservatorio Astronomico di Brera, via Brera 28, 20121 Milano, Italy
⁸ National Research Council of Canada, Herzberg Astronomy and Astrophysics, 5071 West Saanich Road, Victoria, BC, V9E 2E7 Canada
⁹ AIM, CEA, CNRS, Université Paris-Saclay, Université Paris-Diderot, Sorbonne Paris Cité, Observatoire de Paris, PSL University, 91191 Gif-sur-Yvette Cedex, France
¹⁰ University of Calgary, 2500 University Drive NW, Calgary, Alberta, Canada
¹¹ Centro de Astronomiá (CITEVA), Universidad de Antofagasta, Avenida Angamos 601, Antofagasta, Chile
¹² Laboratoire d’Astrophysique de Bordeaux, Univ. Bordeaux, CNRS, B18N, allée Geoffroy Saint-Hilaire, 33615 Pessac, France
¹³ Collège de France, 11 Pl. M. Berthelot, 75005 Paris, France
¹⁴ LERMA, Observatoire de Paris, CNRS, PSL Research University, Sorbonne Universités, UPMC Univ. Paris 06, 75014 Paris, France
¹⁵ Department of Astrophysics, University of Vienna, Türkenschanzstrasse 17, 1180 Vienna, Austria
¹⁶ Departamento de Física, Universidad Técnica Federico Santa María, Vicuña Mackenna 3939, San Joaquín, Santiago, Chile
¹⁷ Key Laboratory for Research in Galaxies and Cosmology, Department of Astronomy, University of Science and Technology of China, Hefei, 230026 PR China
¹⁸ School of Astronomy and Space Science, University of Science and Technology of China, Hefei, 230026 PR China
¹⁹ Department of Astronomy, University of Cape Town, Private Bag X3, Rondebosch, 7701 South Africa

Received: 4 May 2023
Accepted: 21 June 2023

Abstract

We present the first results of a 21 cm H I line pilot observation carried out with the MeerKAT radio telescope in preparation for the ViCTORIA (Virgo Cluster multi Telescope Observations in Radio of Interacting galaxies and AGN) project, an untargeted survey of the Virgo galaxy cluster. The extraordinary quality of the data in terms of sensitivity and angular resolution (rms ∼ 0.65 mJy beam⁻¹ at ∼27″ × 39″ and 11 km s⁻¹ resolution) allowed us to detect an extended (∼10 kpc projected length) low column density (N(HI)≲2.5 × 10²⁰ cm⁻²) H I gas tail associated with the dwarf (M_star = 1.6 × 10⁹ M_⊙) irregular galaxy NGC 4523 at the northern edge of the cluster. The morphology of the tail and of the stellar disc suggest that the galaxy is suffering a hydrodynamic interaction with the surrounding hot intracluster medium (ICM; ram pressure stripping). The orientation of the trailing tail, the gradient in the H I gas column density at the interface between the cold interstellar medium (ISM) and the hot ICM, the velocity of the galaxy with respect to that of the cluster, and its position indicate that NGC 4523 is infalling for the first time into Virgo from the north-north-west background of the cluster. Using a grid of hydrodynamic simulations, we derive the impact parameters with the surrounding ICM, and estimate that the galaxy will be at pericentre (D ∼ 500–600 kpc) in ∼1 Gyr, where ram pressure stripping will be able to remove most, if not all, of its gas. The galaxy is located on the star formation main sequence when its star formation rate is derived using Hα narrow-band images obtained during the VESTIGE survey, suggesting that NGC 4523 is only at the beginning of its interaction with the surrounding environment. A few H II regions are detected in the deep Hα narrow-band images within the H I gas tail outside the stellar disc. Their ages, derived by comparing their Hα, far-ultraviolet (ASTROSAT/UVIT), near-ultraviolet (GALEX/GUViCS), and optical (NGVS) colours with the predictions of spectral energy distribution fitting models, are ≲30 Myr, and suggest that these H II regions have formed within the stripped gas.