VERTICO

III. The Kennicutt-Schmidt relation in Virgo cluster galaxies^⋆

¹ Observatorio Astronómico Nacional (IGN), C/Alfonso XII, 3, 28014 Madrid, Spain
e-mail: mdonaire@oan.es
² Centro de Desarrollos Tecnológicos, Observatorio de Yebes (IGN), 19141 Yebes, Guadalajara, Spain
³ Herzberg Astronomy and Astrophysics Research Centre, National Research Council of Canada, 5071 West Saanich Rd, Victoria, BC V9E 2E7, Canada
⁴ Department of Physics & Astronomy, McMaster University, 1280 Main St West, Hamilton, Ontario L8S 4M1, Canada
⁵ Leiden Observatory, Leiden University, PO Box 9513 2300 RA Leiden, The Netherlands
⁶ Department of Astronomy, University of Cape Town, Private Bag X3, Rondebosch 7701, South Africa
⁷ Department of Physics & Astronomy, University of Victoria, Finnerty Road, Victoria, British Columbia V8P 1A1, Canada
⁸ Department of Astronomy, University of Maryland, College Park, MD 20742, USA
⁹ Department of Physics & Astronomy, The University of Western Ontario, London, ON N6A 3K7, Canada
¹⁰ Institute for Earth and Space Exploration, The University of Western Ontario, London, ON N6A 3K7, Canada
¹¹ Department of Physics, Engineering Physics, and Astronomy, Queen’s University, Kingston, ON K7L 3N6, Canada
¹² Aix-Marseille Université, CNRS, CNES, LAM, Marseille, France
¹³ International Centre for Radio Astronomy Research, The University of Western Australia, 35 Stirling Hwy, 6009 Crawley, WA, Australia
¹⁴ ARC Centre of Excellence for All Sky Astrophysics in 3 Dimensions (ASTRO 3D), Australia
¹⁵ Department of Astronomy, Yonsei University, 50 Yonsei-ro, Seodamun-gu, Seoul 03722, Republic of Korea
¹⁶ School of Physics & Astronomy, Cardiff University, Queens Buildings, The Parade, Cardiff CF24 3AA, UK
¹⁷ Korea Astronomy and Space Science Institute, 776 Daedeokdae-ro, Yuseong-gu, Daejeon 34055, Republic of Korea
¹⁸ Royal Military College of Canada, PO Box 17000 Station Forces, Kingston, ON K7K 7B4, Canada
¹⁹ Canadian Institute for Theoretical Astrophysics (CITA), University of Toronto, 60 St George Street, Toronto, ON M5S 3H8, Canada

Received: 9 August 2022
Accepted: 23 November 2022

Abstract

Aims. In this Virgo Environment Traced in CO (VERTICO) science paper, we aim to study how the star formation process depends on the galactic environment and gravitational interactions in the context of galaxy evolution. We explore the scaling relation between the star formation rate surface density (Σ_SFR) and the molecular gas surface density (Σ_mol), also known as the Kennicutt-Schmidt relation, in a subsample of Virgo cluster spiral galaxies.

Methods. We used new Atacama Compact Array and Total Power (ACA+TP) observations from the VERTICO-Atacama Large Millimeter/submillimeter Array (ALMA) Large Program at 720 pc resolution to resolve the molecular gas content, as traced by the ¹²CO (2 − 1) transition, across the disks of 37 spiral galaxies in the Virgo cluster. In combination with archival UV and IR observations used to determine the star formation rate (SFR), we estimated the parameters of the Kennicutt-Schmidt (KS) relation for the entire ensemble of galaxies, and within individual galaxies.

Results. We find the KS slope for the entire population to be N = 0.97 ± 0.07, with a characteristic molecular gas depletion time of 1.86 Gyr for our full sample, which is in agreement with previous work in isolated, nearby star-forming galaxies. In individual galaxies, we find that the KS slope ranges between 0.69 and 1.40, and that typical star formation efficiencies of molecular gas can vary from galaxy to galaxy by a factor of ∼4. These galaxy-to-galaxy variations account for ∼0.20 dex in scatter in the ensemble KS relation, which is characterized by a 0.42 dex scatter. In addition, we find that the HI-deficient galaxies in the Virgo cluster show a steeper resolved KS relation and lower molecular gas efficiencies than HI-normal cluster galaxies.

Conclusions. While the molecular gas content in galaxies residing in the Virgo cluster appears – to first order – to behave similarly to that in isolated galaxies, our VERTICO sample of galaxies shows that cluster environments play a key role in regulating star formation. The environmental mechanisms affecting the HI galaxy content also have a direct impact on the star formation efficiency of molecular gas in cluster galaxies, leading to longer depletion times in HI-deficient members.