Euclid Quick Data Release (Q1). The shape of cluster haloes revealed by intracluster light

@misc{collaboration2026euclid,
  title = {{Euclid Quick Data Release (Q1). The shape of cluster haloes revealed by intracluster light}},
  author = {Euclid Collaboration and T. Kolcu and N. A. Hatch and A. Fernandez and S. P. Bamford and H. Gao and J. B. Golden-Marx and G. Martin and Y. M. Bahé and S. L. Ahad and C. Bellhouse and J. Butler and S. de Nicola and F. Durret and A. Ellien and A. H. Gonzalez and H. Gully and M. Kluge and M. Maturi and M. Montes and L. Moscardini and R. Ragusa and A. Saro and M. Urbano and N. Aghanim and B. Altieri and S. Andreon and N. Auricchio and C. Baccigalupi and M. Baldi and S. Bardelli and P. Battaglia and R. Bender and A. Biviano and M. Bolzonella and E. Branchini and M. Brescia and S. Camera and G. Cañas-Herrera and V. Capobianco and C. Carbone and J. Carretero and S. Casas and M. Castellano and G. Castignani and S. Cavuoti and K. C. Chambers and A. Cimatti and C. Colodro-Conde and G. Congedo and C. J. Conselice and L. Conversi and Y. Copin and F. Courbin and H. M. Courtois and M. Cropper and J. -C. Cuillandre and A. Da Silva and H. Degaudenzi and G. De Lucia},
  howpublished = {arXiv},
  year = {2026},
  month = oct,
  doi = {10.48550/arxiv.2610.29683},
  eprint = {2610.29683},
  archivePrefix = {arXiv},
  url = {https://arxiv.org/abs/2610.29683},
  note = {CC BY 4.0},
}

TY  - UNPB
TI  - Euclid Quick Data Release (Q1). The shape of cluster haloes revealed by intracluster light
AU  - Euclid Collaboration
AU  - T. Kolcu
AU  - N. A. Hatch
AU  - A. Fernandez
AU  - S. P. Bamford
AU  - H. Gao
AU  - J. B. Golden-Marx
AU  - G. Martin
AU  - Y. M. Bahé
AU  - S. L. Ahad
AU  - C. Bellhouse
AU  - J. Butler
AU  - S. de Nicola
AU  - F. Durret
AU  - A. Ellien
AU  - A. H. Gonzalez
AU  - H. Gully
AU  - M. Kluge
AU  - M. Maturi
AU  - M. Montes
AU  - L. Moscardini
AU  - R. Ragusa
AU  - A. Saro
AU  - M. Urbano
AU  - N. Aghanim
AU  - B. Altieri
AU  - S. Andreon
AU  - N. Auricchio
AU  - C. Baccigalupi
AU  - M. Baldi
AU  - S. Bardelli
AU  - P. Battaglia
AU  - R. Bender
AU  - A. Biviano
AU  - M. Bolzonella
AU  - E. Branchini
AU  - M. Brescia
AU  - S. Camera
AU  - G. Cañas-Herrera
AU  - V. Capobianco
AU  - C. Carbone
AU  - J. Carretero
AU  - S. Casas
AU  - M. Castellano
AU  - G. Castignani
AU  - S. Cavuoti
AU  - K. C. Chambers
AU  - A. Cimatti
AU  - C. Colodro-Conde
AU  - G. Congedo
AU  - C. J. Conselice
AU  - L. Conversi
AU  - Y. Copin
AU  - F. Courbin
AU  - H. M. Courtois
AU  - M. Cropper
AU  - J. -C. Cuillandre
AU  - A. Da Silva
AU  - H. Degaudenzi
AU  - G. De Lucia
PY  - 2026
DA  - 2026/10/21
PB  - arXiv
DO  - 10.48550/arxiv.2610.29683
UR  - https://arxiv.org/abs/2610.29683
AB  - Intracluster light (ICL) offers a luminous route for measuring the shapes and orientations of cluster haloes. We used Euclid Quick Data Release (Q1) images to quantify ICL shapes for 205 clusters at 0.1 ≤ z ≤ 0.8 selected from the eROSITA All-Sky Survey and the Dark Energy Survey. We measured the ICL properties across five bands (I_E, Y_E, J_E, H_E and the coadded YJH_E), and find that the shape parameters are consistent across the filters, with the H_E band probing the profiles to the largest cluster-centric distances (0.1R_200c∼100 kpc). The ICL ellipticity (e=1−b/a) distribution peaks at 0.5, consistent with halo ellipticities inferred from strong and weak lensing studies, suggesting that the ICL traces the large-scale structure of the clusters. Cluster cores, dominated by brightest cluster galaxy (BCG) light, are round (e∼0.2), while the ICL becomes progressively more elongated at large radii, reaching an ellipticity of ∼0.5 by 0.1R_200c. We find that the ICL is closely aligned with the BCG (87% lie within 30^∘), but shows a weaker alignment with the satellite galaxy distribution (61% within 30^∘). Robust position angles could be measured using the ICL for 63% of the sample, whereas position angles could be measured for only 30% of the sample using the satellite galaxies. Stacking clusters in redshift bins allows measurements of the ICL surface brightness to $0.6−0.8R_{200\mathrm{c}}$ and ellipticity beyond $0.3−0.4R_{200\mathrm{c}}$ (300-400 kpc), but we observed a plateau in the ICL ellipticity beyond 0.1R_200c. These results demonstrate the capability of Euclid to characterise the ICL morphology with high statistical precision, allowing new constraints on cluster halo structure and its evolution with redshift.
ER  -