Letter to the Editor

A Virgo Environmental Survey Tracing Ionised Gas Emission (VESTIGE)

VI. Environmental quenching on HII-region scales^⋆

¹ Aix Marseille Univ, CNRS, CNES, LAM, Marseille, France
e-mail: alessandro.boselli@lam.fr, alessia.longobardi@lam.fr
² Institute for Computational Cosmology and Centre for Extragalactic Astronomy, Department of Physics, Durham University, South Road, Durham DH1 3LE, UK
e-mail: matteo.fossati@durham.ac.uk
³ Centro de Astronomá (CITEVA), Universidad de Antofagasta, Avenida Angamos 601, Antofagasta, Chile
⁴ Laboratoire d’Astrophysique de Bordeaux, Univ. Bordeaux, CNRS, B18N, Allée Geoffroy Saint-Hilaire, 33615 Pessac, France
⁵ NRC Herzberg Astronomy and Astrophysics, 5071 West Saanich Road, Victoria, BC V9E 2E7, Canada
⁶ AIM, CEA, CNRS, Université Paris-Saclay, Université Paris Diderot, Sorbonne Paris Cité, Observatoire de Paris, PSL University, 91191 Gif-sur-Yvette Cedex, France
⁷ Universitá di Milano-Bicocca, Piazza della Scienza 3, 20100 Milano, Italy
⁸ Department of Astrophysics, University of Vienna, Türkenschanzstrasse 17, 1180 Vienna, Austria
⁹ Laboratório de Astrofísica Teórica e Observacional, Universidade Estadual de Santa Cruz, 45650-000 Ilhéus, BA, Brasil
¹⁰ Department of Physics and Astronomy, University of Alabama in Huntsville, Huntsville, AL 35899, USA
¹¹ INAF – Osservatorio Astronomico di Brera, Via Brera 28, 20159 Milano, Italy

Received: 13 December 2019
Accepted: 17 January 2020

Abstract

The Virgo Environmental Survey Tracing Ionised Gas Emission (VESTIGE) is a blind narrow-band Hα + [NII] imaging survey of the Virgo cluster carried out with MegaCam at the Canada-French-Hawaii telescope. We use a new set of data extracted from VESTIGE to study the impact of the hostile cluster environment on the star formation process down to the scale of HII regions (∼50 pc). Here, HII regions are identified and their parameters measured using the HIIPHOT code on a sample of 114 late-type galaxies spanning a wide range in morphological type (Sa-Sd, Im, BCD), stellar mass (10^6.5 ≤ M_star ≤ 10¹¹ M_⊙), and star formation activity (10⁻³ ≤ SFR ≤ 10 M_⊙ yr⁻¹). Owing to the exquisite average resolution of the VESTIGE data (0.65 arcsec), we detect 11302 HII regions with an Hα luminosity L(Hα) ≥ 10³⁷ erg s⁻¹. We show that the typical number of HII regions in gas-stripped objects is significantly lower than in healthy late-types of similar stellar mass. We also show that in these gas-stripped galaxies the number of HII regions significantly drops outside the effective radius, suggesting that the quenching process occurs outside-in, in agreement with other multifrequency observations. These new results consistently confirm that the main mechanism responsible for the decrease of the star formation activity observed in cluster galaxies is ram pressure, allowing us to discard other milder processes such as starvation or strangulation, which are unable to reproduce the observed radially truncated profiles.