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| Format: | Preprint |
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2026
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| Online-Zugang: | https://arxiv.org/abs/2603.23689 |
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| author | Srinivasan, Radhakrishnan Shin, Tae-hyeon von der Linden, Anja Herbonnet, Ricardo Klein, Matthias Varga, Tamas N. Frigo, Antonio Bleem, Lindsey E. Wu, Hao-Yi Zhang, Zhuowen Levine, Benjamin Alarcon, Alex Amon, Alexandra Bayliss, Matthew B. Bechtol, Keith Becker, Matthew Bernstein, Gary Bocquet, Sebastian Campos, Andresa Rosell, Aurelio Carnero Kind, Matias Carrasco Chang, Chihway Chen, Rebecca Choi, Ami De Vicente, Juan DeRose, Joseph Dodelson, Scott Doux, Cyrille Drlica-Wagner, Alex Elvin-Poole, Jack Everett, Spencer Ferté, Agnès Gatti, Marco Gassis, Raven Gladders, Michael D. Grandis, Sebastian Gruen, Daniel Gruendl, Robert Harrison, Ian Jarvis, Mike MacCrann, Niall McCullough, Jamie McDonald, Michael A. Myles, Justin Alsina, Andres Navarro Pandey, Shivam Prat, Judit Raveri, Marco Reichardt, Christian L. Rollins, Richard Rykoff, Eli Sanchez, Carles Sarkar, Arnab Secco, Lucas F. Sevilla, Ignacio Sheldon, Erin Somboonpanyakul, Taweewat Stalder, Brian Stark, Anthony A. Troxel, Michael A. Tutusaus, Isaac Yanny, Brian Yin, Boyan Aguena, Michel Allam, Sahar Andrade-Oliveira, Felipe Bacon, David Blazek, Jonathan Brooks, David Burke, David Camilleri, Ryan Carretero, Jorge Costanzi, Matteo da Costa, Luiz Pereira, Maria Elidaiana da Silva Desai, Shantanu Diehl, H. Thomas Garcia-Bellido, Juan Gutierrez, Gaston Hinton, Samuel Hollowood, Devon L. Lee, Sujeong Marshall, Jennifer Mena-Fernández, Juan Menanteau, Felipe Miquel, Ramon Malagón, Andrés Plazas Ogando, Ricardo Romer, Kathy Roodman, Aaron Sanchez, Eusebio Cid, David Sanchez Suchyta, Eric Swanson, Molly Weaverdyck, Noah Weller, Jochen |
| author_facet | Srinivasan, Radhakrishnan Shin, Tae-hyeon von der Linden, Anja Herbonnet, Ricardo Klein, Matthias Varga, Tamas N. Frigo, Antonio Bleem, Lindsey E. Wu, Hao-Yi Zhang, Zhuowen Levine, Benjamin Alarcon, Alex Amon, Alexandra Bayliss, Matthew B. Bechtol, Keith Becker, Matthew Bernstein, Gary Bocquet, Sebastian Campos, Andresa Rosell, Aurelio Carnero Kind, Matias Carrasco Chang, Chihway Chen, Rebecca Choi, Ami De Vicente, Juan DeRose, Joseph Dodelson, Scott Doux, Cyrille Drlica-Wagner, Alex Elvin-Poole, Jack Everett, Spencer Ferté, Agnès Gatti, Marco Gassis, Raven Gladders, Michael D. Grandis, Sebastian Gruen, Daniel Gruendl, Robert Harrison, Ian Jarvis, Mike MacCrann, Niall McCullough, Jamie McDonald, Michael A. Myles, Justin Alsina, Andres Navarro Pandey, Shivam Prat, Judit Raveri, Marco Reichardt, Christian L. Rollins, Richard Rykoff, Eli Sanchez, Carles Sarkar, Arnab Secco, Lucas F. Sevilla, Ignacio Sheldon, Erin Somboonpanyakul, Taweewat Stalder, Brian Stark, Anthony A. Troxel, Michael A. Tutusaus, Isaac Yanny, Brian Yin, Boyan Aguena, Michel Allam, Sahar Andrade-Oliveira, Felipe Bacon, David Blazek, Jonathan Brooks, David Burke, David Camilleri, Ryan Carretero, Jorge Costanzi, Matteo da Costa, Luiz Pereira, Maria Elidaiana da Silva Desai, Shantanu Diehl, H. Thomas Garcia-Bellido, Juan Gutierrez, Gaston Hinton, Samuel Hollowood, Devon L. Lee, Sujeong Marshall, Jennifer Mena-Fernández, Juan Menanteau, Felipe Miquel, Ramon Malagón, Andrés Plazas Ogando, Ricardo Romer, Kathy Roodman, Aaron Sanchez, Eusebio Cid, David Sanchez Suchyta, Eric Swanson, Molly Weaverdyck, Noah Weller, Jochen |
| contents | The orientation of triaxial galaxy clusters with respect to the line-of-sight is expected to be one of the prime sources of scatter and potential bias in optical observables (e.g., richness and weak-lensing signal) of galaxy clusters. In this work, we use the observed shape of the central Brightest Cluster Galaxy (BCG) as proxy for the orientation along the line-of-sight for clusters selected via the Sunyaev-Zel'dovich (SZ) effect from the South Pole Telescope (SPT) and Atacama Cosmology Telescope (ACT) surveys, matched to optically selected clusters from the Dark Energy Survey Year 3 (DES). We construct two samples of clusters that are designed to be identical in SZ mass estimate and redshift but with the roundest vs. the most elliptical BCGs, which we expect to correspond to BCGs (and clusters) with major axes aligned along the line-of-sight vs. in the plane of the sky, respectively. We find that the optical richness of round-BCG clusters is $\sim 10$\% larger than that of elliptical-BCG clusters, in agreement with the expectation from projection effects and presenting the first such detection in data. The density profiles, however, are not in agreement with the expectation from projection effects: the 1-halo term (below $6~h^{-1}\rm{Mpc}$) of both the weak-lensing and galaxy density profiles are the same for the subsamples, contrary to previous studies based on X-ray selected clusters. In the 2-halo regime (above $6~h^{-1}\rm{Mpc}$), we find a significant excess of the elliptical-BCG cluster profiles compared to the round-BCG cluster profiles, which is the opposite of the expectation from numerical simulations. We hypothesize that the intrinsic shape of the BCG reflects not just the orientation angle, but also intrinsic properties of the cluster which can affect both the SZ signal and the amplitude of the 2-halo term. |
| format | Preprint |
| id |
arxiv_https___arxiv_org_abs_2603_23689 |
| institution | arXiv |
| publishDate | 2026 |
| record_format | arxiv |
| spellingShingle | Brightest Cluster Galaxy ellipticity as proxy for halo shape: Orientation bias, assembly bias, and potential selection effects in SZ-selected clusters Srinivasan, Radhakrishnan Shin, Tae-hyeon von der Linden, Anja Herbonnet, Ricardo Klein, Matthias Varga, Tamas N. Frigo, Antonio Bleem, Lindsey E. Wu, Hao-Yi Zhang, Zhuowen Levine, Benjamin Alarcon, Alex Amon, Alexandra Bayliss, Matthew B. Bechtol, Keith Becker, Matthew Bernstein, Gary Bocquet, Sebastian Campos, Andresa Rosell, Aurelio Carnero Kind, Matias Carrasco Chang, Chihway Chen, Rebecca Choi, Ami De Vicente, Juan DeRose, Joseph Dodelson, Scott Doux, Cyrille Drlica-Wagner, Alex Elvin-Poole, Jack Everett, Spencer Ferté, Agnès Gatti, Marco Gassis, Raven Gladders, Michael D. Grandis, Sebastian Gruen, Daniel Gruendl, Robert Harrison, Ian Jarvis, Mike MacCrann, Niall McCullough, Jamie McDonald, Michael A. Myles, Justin Alsina, Andres Navarro Pandey, Shivam Prat, Judit Raveri, Marco Reichardt, Christian L. Rollins, Richard Rykoff, Eli Sanchez, Carles Sarkar, Arnab Secco, Lucas F. Sevilla, Ignacio Sheldon, Erin Somboonpanyakul, Taweewat Stalder, Brian Stark, Anthony A. Troxel, Michael A. Tutusaus, Isaac Yanny, Brian Yin, Boyan Aguena, Michel Allam, Sahar Andrade-Oliveira, Felipe Bacon, David Blazek, Jonathan Brooks, David Burke, David Camilleri, Ryan Carretero, Jorge Costanzi, Matteo da Costa, Luiz Pereira, Maria Elidaiana da Silva Desai, Shantanu Diehl, H. Thomas Garcia-Bellido, Juan Gutierrez, Gaston Hinton, Samuel Hollowood, Devon L. Lee, Sujeong Marshall, Jennifer Mena-Fernández, Juan Menanteau, Felipe Miquel, Ramon Malagón, Andrés Plazas Ogando, Ricardo Romer, Kathy Roodman, Aaron Sanchez, Eusebio Cid, David Sanchez Suchyta, Eric Swanson, Molly Weaverdyck, Noah Weller, Jochen Cosmology and Nongalactic Astrophysics The orientation of triaxial galaxy clusters with respect to the line-of-sight is expected to be one of the prime sources of scatter and potential bias in optical observables (e.g., richness and weak-lensing signal) of galaxy clusters. In this work, we use the observed shape of the central Brightest Cluster Galaxy (BCG) as proxy for the orientation along the line-of-sight for clusters selected via the Sunyaev-Zel'dovich (SZ) effect from the South Pole Telescope (SPT) and Atacama Cosmology Telescope (ACT) surveys, matched to optically selected clusters from the Dark Energy Survey Year 3 (DES). We construct two samples of clusters that are designed to be identical in SZ mass estimate and redshift but with the roundest vs. the most elliptical BCGs, which we expect to correspond to BCGs (and clusters) with major axes aligned along the line-of-sight vs. in the plane of the sky, respectively. We find that the optical richness of round-BCG clusters is $\sim 10$\% larger than that of elliptical-BCG clusters, in agreement with the expectation from projection effects and presenting the first such detection in data. The density profiles, however, are not in agreement with the expectation from projection effects: the 1-halo term (below $6~h^{-1}\rm{Mpc}$) of both the weak-lensing and galaxy density profiles are the same for the subsamples, contrary to previous studies based on X-ray selected clusters. In the 2-halo regime (above $6~h^{-1}\rm{Mpc}$), we find a significant excess of the elliptical-BCG cluster profiles compared to the round-BCG cluster profiles, which is the opposite of the expectation from numerical simulations. We hypothesize that the intrinsic shape of the BCG reflects not just the orientation angle, but also intrinsic properties of the cluster which can affect both the SZ signal and the amplitude of the 2-halo term. |
| title | Brightest Cluster Galaxy ellipticity as proxy for halo shape: Orientation bias, assembly bias, and potential selection effects in SZ-selected clusters |
| topic | Cosmology and Nongalactic Astrophysics |
| url | https://arxiv.org/abs/2603.23689 |