A giant thin stellar stream in the Coma Galaxy Cluster

TL;DR

This paper reports the discovery of an extremely faint, giant stellar stream in the Coma Galaxy Cluster, providing new insights into dark matter and galaxy interactions in dense environments.

Contribution

It presents the first detection of a giant, thin stellar stream in a galaxy cluster, supported by simulation comparisons, expanding the known environmental contexts of such structures.

Findings

Detected a 510 kpc long stellar stream with a surface brightness of 29.5 mag arcsec$^{-2}$

Identified the stream as a tidally disrupting dwarf galaxy remnant

Supported the existence of similar streams in galaxy clusters through simulations

Abstract

The study of dynamically cold stellar streams reveals information about the gravitational potential where they reside and provides important constraints on dark matter properties. However, their intrinsic faintness makes detection beyond Local environments highly challenging. Here we report the detection of an extremely faint stellar stream ($\mu_{g,max}=$ 29.5 mag arcsec$^{-2}$) with an extraordinarily coherent and thin morphology in the Coma Galaxy Cluster. This Giant Coma Stream spans ~510 kpc in length and appears as a free-floating structure located at a projected distance of 0.8 Mpc from the centre of Coma. We do not identify any potential galaxy remnant or core, and the stream structure appears featureless in our data. We interpret the Giant Coma Stream as being a recently accreted, tidally disrupting passive dwarf. Using the Illustris-TNG50 simulation, we identify a case with similar characteristics, showing that, although rare, these types of streams are predicted to exist in $\Lambda$-CDM. Our work unveils the presence of free-floating, extremely faint and thin stellar streams in galaxy clusters, widening the environmental context for their promising future applications in the study of dark matter properties.