Does the virial mass drive the intra-cluster light?. Relationship between the ICL and M<SUB>vir</SUB> from VEGAS

Ragusa, R.; Iodice, E.; Spavone, M.; Montes, M.; Forbes, D. A.; Brough, S.; Mirabile, M.; Cantiello, M.; Paolillo, M.; Schipani, P.
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Astronomy and Astrophysics

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In this Letter, we revisit the relationship between the fraction of the intra-cluster light (ICL) as well as the virial mass and the fraction of early-type galaxies in the host halo. This exploration is based on a statistically significant and homogeneous sample of 22 groups and clusters of galaxies in the Local Universe (z ≤ 0.05), obtained with the VST Early-type GAlaxy Survey (VEGAS). Taking advantage of the long integration time and large area of the VEGAS images, we are able to map the galaxy outskirts and ICL down to μg ≥ 29-30 mag arcsec−2 and out to hundreds of kpc. With this data set, we have expanded the sample of ICL measurements, doubling the previous measures available from the literature for z ≤ 0.05. The main result of this work is the apparent lack of any significant trend between the fraction of ICL and the virial mass of the host environment, covering a wide range of virial masses (∼1012.5 ≤ Mvir ≤ 1015.5 M⊙), in full agreement with a number of theoretical studies. Since the new data points have all been derived based on the same methodology and from the same observational setup, all with comparable depths, the large observed scatter indicates an intrinsic variation in the ICL fraction. On the other hand, there is a weak relationship between the fraction of ICL and the fraction of early-type galaxies in the host halo, where a larger fraction of ICL is found in groups and clusters of galaxies dominated by earlier morphological types, indicating a connection between the ICL and the dynamical state of the host system.