Probing Galaxy Evolution in Massive Clusters Using ACT and DES: Splashback as a Cosmic Clock

Susmita Adhikari, Tae Hyeon Shin, Bhuvnesh Jain, Matt Hilton, Eric Baxter, Chihway Chang, Risa H. Wechsler, Nick Battaglia, J. Richard Bond, Sebastian Bocquet, Steve K. Choi, Joseph Derose, Mark Devlin, Jo Dunkley, August E. Evrard, Simone Ferraro, J. Colin Hill, John P. Hughes, Patricio A. Gallardo, Martine LokkenAmanda Macinnis, Mathew S. Madhavacheril, Jeffrey McMahon, Frederico Nati, Laura B. Newburgh, Michael D. Niemack, Lyman A. Page, Antonella Palmese, Bruce Partridge, Eduardo Rozo, Eli Rykoff, Maria Salatino, Alessandro Schillaci, Neelima Sehgal, Cristóbal Sifón, Chun Hao To, Ed Wollack, Hao Yi Wu, Zhilei Xu, Michel Aguena, Sahar Allam, Alexandra Amon, James Annis, Santiago Avila, David Bacon, Emmanuel Bertin, Sunayana Bhargava, David Brooks, David L. Burke, Aurelio C. Rosell, Matias Carrasco Kind, Jorge Carretero, Francisco Javier Castander, Ami Choi, Matteo Costanzi, Luiz N. Da Costa, Juan De Vicente, Shantanu Desai, Thomas H. Diehl, Peter Doel, Spencer Everett, Ismael Ferrero, Agnes Ferté, Brenna Flaugher, Pablo Fosalba, Josh Frieman, Juan García-Bellido, Enrique Gaztanaga, Daniel Gruen, Robert A. Gruendl, Julia Gschwend, Gaston Gutierrez, Will G. Hartley, Samuel R. Hinton, Devon L. Hollowood, Klaus Honscheid, David J. James, Tesla Jeltema, Kyler Kuehn, Nikolay Kuropatkin, Ofer Lahav, Marcos Lima, Marcio A.G. Maia, Jennifer L. Marshall, Paul Martini, Peter Melchior, Felipe Menanteau, Ramon Miquel, Robert Morgan, Ricardo L. C. Ogando, Francisco Paz-Chinchón, Andrés Plazas Malagón, Eusebio Sanchez, Basilio Santiago, Vic Scarpine, Santiago Serrano, Ignacio Sevilla-Noarbe, Mathew Smith, Marcelle Soares-Santos, Eric Suchyta, Molly E. C. Swanson, Tamas N. Varga, Reese D. Wilkinson, Yuanyuan Zhang, Jason E. Austermann, James A. Beall, Daniel T. Becker, Edward V. Denison, Shannon M. Duff, Gene C. Hilton, Johannes Hubmayr, Joel N. Ullom, Jeff Van Lanen, Leila R. Vale

Research output: Contribution to journalArticlepeer-review

24 Scopus citations


We measure the projected number density profiles of galaxies and the splashback feature in clusters selected by the Sunyaev-Zel'dovich effect from the Advanced Atacama Cosmology Telescope (AdvACT) survey using galaxies observed by the Dark Energy Survey (DES). The splashback radius is consistent with CDM-only simulations and is located at 2.4-0.4+0.3 Mpc h-1. We split the galaxies on color and find significant differences in their profile shapes. Red and green-valley galaxies show a splashback-like minimum in their slope profile consistent with theory, while the bluest galaxies show a weak feature at a smaller radius. We develop a mapping of galaxies to subhalos in simulations and assign colors based on infall time onto their hosts. We find that the shift in location of the steepest slope and different profile shapes can be mapped to the average time of infall of galaxies of different colors. The steepest slope traces a discontinuity in the phase space of dark matter halos. By relating spatial profiles to infall time, we can use splashback as a clock to understand galaxy quenching. We find that red galaxies have on average been in clusters over 3.2 Gyr, green galaxies about 2.2 Gyr, while blue galaxies have been accreted most recently and have not reached apocenter. Using the full radial profiles, we fit a simple quenching model and find that the onset of galaxy quenching occurs after a delay of about a gigayear and that galaxies quench rapidly thereafter with an exponential timescale of 0.6 Gyr.

Original languageEnglish (US)
Article number37
JournalAstrophysical Journal
Issue number1
StatePublished - Dec 10 2021

All Science Journal Classification (ASJC) codes

  • Astronomy and Astrophysics
  • Space and Planetary Science


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