Virgo filaments

VI. Hα clumps in filaments around the Virgo galaxy cluster

¹ Laboratoire d’astrophysique, Ecole Polytechnique Federale de Lausanne (EPFL), Route de la Sorge, 1015, Lausanne, Switzerland
² LIRA, Observatoire de Paris, Université PSL, CNRS, 5 Place Jules Janssen, 92190, Meudon, France
³ Department of Physics and Astronomy, Siena University, 515 Loudon Road, Loudonville, NY, 12211, USA
⁴ School of Physics and Astronomy, University of Nottingham, University Park, Nottingham, NG7 2RD, UK
⁵ Observatoire de Paris, LUX, Collège de France, CNRS, PSL University, Sorbonne University, 75014, Paris, France
⁶ INAF–Osservatorio di Astrofisica e Scienza dello Spazio di Bologna, Via Gobetti 93/3, I-40129, Bologna, Italy
⁷ INAF–Osservatorio astronomico di Padova, Vicolo Osservatorio 5, I-35122, Padova, Italy
⁸ University of Kansas, Department of Physics and Astronomy, 1251 Wescoe Hall Drive, Room 1082, Lawrence, KS, 66049, USA
⁹ INAF – Osservatorio Astronomico di Trieste, Via Tiepolo 11, I-34131, Trieste, Italy
¹⁰ Department of Physics & Astronomy, Union College, Schenectady, NY, 12308, USA
¹¹ Steward Observatory, University of Arizona, 933 North Cherry Avenue, Tucson, AZ, 85721-0065, USA

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

Received: 26 January 2026
Accepted: 4 March 2026

Abstract

The question of which environmental processes operate in filaments still remains unresolved. Given the ubiquity of filaments and their importance in feeding clusters, a proper understanding of these mechanisms is crucial to building a more complete picture of galaxy evolution. Carrying out such an investigation requires access to large galaxy samples with spatially resolved information. As part of this effort, we analysed resolved Hα maps of 685 galaxies inside and outside the filaments around the Virgo cluster, in addition to extensive measurements of the integrated physical properties. We created a pipeline to decompose the Hα images into individual clumps that trace star-forming regions. We find that the number and average size of clumps in a galaxy are well-defined functions of distance and angular resolution. In particular, the power-law relation between the number of clumps and the distance of a galaxy is consistent with a fractal structure of star forming regions. We formulated an algorithm to compare filament and non-filament galaxies after removing observational differences. Although we do not have any conclusive evidence of a difference in clump size distributions between filament and non-filament galaxies, we do find that filament galaxies have slightly more peripheral clumps than their non-filament counterparts.