The intragroup light in KiDS+GAMA groups

Ahad, SL ORCID: 0000-0001-6336-642X, Hoekstra, H ORCID: 0000-0002-0641-3231, Bahé, YM ORCID: 0000-0002-3196-5126, Baldry, IK ORCID: 0000-0003-0719-9385, Kuijken, K ORCID: 0000-0002-3827-0175, Brough, S ORCID: 0000-0002-9796-1363 and Holwerda, BW ORCID: 0000-0002-4884-6756 (2025) The intragroup light in KiDS+GAMA groups. Astronomy & Astrophysics, 702. A271-A271. ISSN 0004-6361

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Abstract

The assembly of galaxy groups and clusters occur through dynamical interactions of smaller systems, resulting in the formation of a diffuse stellar halo known as the intragroup or intracluster light (IGL or ICL). By preserving the records of these interactions, the IGL and ICL provide valuable insight into the growth history of galaxy groups and clusters. Groups are especially interesting because they represent the link between galactic halos and massive clusters. However, the low surface brightness of this diffuse light makes it extremely challenging to detect individually. Recent deep wide-field imaging surveys allow us to push such measurements to lower brightness limits by stacking data for large ensembles of groups, thereby suppressing the noise and biases in the measurements. In this work, we present a special-purpose pipeline to reprocess individual r-band Kilo-Degree Survey (KiDS) exposures to optimise the IGL detection. Using an initial sample of 2385 groups with at least five spectroscopically confirmed member galaxies from the Galaxy and Mass Assembly (GAMA) survey and deep images from KiDS (reprocessed with our updated pipeline), we present the first robust measurement of IGL from a large group sample (∼750) down to 31−32 mag/arcsec2 (varying in different stacked bins). We also compare our stacked IGL measurements to predictions from matched mock observations from the Hydrangea cosmological hydrodynamic simulations. Systematics in the imaging data can affect IGL measurements, even with our special-purpose pipeline. However, with a large sample and optimised analysis, we can place well-constrained upper and lower limits on the IGL fraction (3−21%) for our group ensemble across 0.09 ≤ z ≤ 0.27 and 12.5 ≤ log10[M200/M⊙] ≤ 14.0. This work explores the potential performance of stacked statistical analysis of diffuse light in large samples of systems from next-generation observational programs such as Euclid and the Vera C. Rubin Observatory’s Legacy Survey of Space and Time (LSST).

Item Type:	Article
Uncontrolled Keywords:	5109 Space Sciences; 5107 Particle and High Energy Physics; 5101 Astronomical Sciences; 51 Physical Sciences; Bioengineering; 0201 Astronomical and Space Sciences; Astronomy & Astrophysics; 5101 Astronomical sciences; 5107 Particle and high energy physics; 5109 Space sciences
Subjects:	Q Science > QB Astronomy Q Science > QC Physics
Divisions:	Astrophysics Research Institute
Publisher:	EDP Sciences
Date of acceptance:	23 August 2025
Date of first compliant Open Access:	29 October 2025
Date Deposited:	29 Oct 2025 14:45
Last Modified:	29 Oct 2025 15:00
DOI or ID number:	10.1051/0004-6361/202452001
URI:	https://researchonline.ljmu.ac.uk/id/eprint/27442

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