Probing Baryons with the Kinematic Sunyae Zel'dovich Effect and Machine Learning Derived Peculiar Velocities using DESI DR2 and ACT DR6
Year: 2026
Type: preprint
Abstract: We present novel empirical constraints on average optical depths and gas density profiles from combining kinematic Sunyaev Zel'dovich effect (kSZ) measurements and nonlinear peculiar velocities, reconstructed using machine learning, for massive halos traced by DESI DR2 luminous red galaxies (LRG). The pairwise kSZ is measured using two ACT DR6 cosmic microwave background (CMB) temperature maps (ILC and 150 GHz maps) for seven luminosity-selected LRG samples. We find consistent results between the two maps and significant detections across the samples. We reconstruct LRG line-of-sight peculiar velocities in two cosmic epochs, centered on $z=$ 0.55 and 0.8, using a simulation-trained Transformer machine learning model to extend beyond the linear approximation. Average optical depths are inferred by comparing the kSZ pairwise correlation to the measured pairwise velocity correlation from the reconstructed velocity field and, separately, from a theoretical prediction using the best fit Planck cosmology, with the highest significance reaching SNR = 14.2 and 15.1 respectively. We also obtain velocity-weighted AP-filtered kSZ-stacked cluster density profiles, which show evidence of extended ionized gas around massive LRG groups and no strong redshift evolution within current measurement uncertainties. These results demonstrate the power of combining spectroscopic galaxy and CMB data, and employing machine learning methods, to probe diffuse baryons and coherent large-scale velocity fields. They open up new avenues to leverage upcoming galaxy survey data from Euclid, Roman and Rubin LSST, in tandem with multi-frequency CMB/sub-mm data from CCAT and Simons Observatory.
Source: arXiv (Cornell University)
Authors: Gong, Yulin, Bean, Rachel, Gallardo, Patricio A., Hadzhiyska, Boryana, Hsu, Yun-Hsin, Moore, Jenna, Vavagiakis, Eve M., Battaglia, Nicholas, Aguilar, J., Ahlen, S., Aviles, A., Beutler, F., Bianchi, D., Brooks, D., Rosell, A. Carnero, Claybaugh, T., de la Macorra, A., Dey, Arjun, Dey, Biprateep, Doel, P., Font-Ribera, A., Forero-Romero, J. E., Gaztañaga, E., Gutierrez, G., Honscheid, K., Juneau, S., Karim, T., Kehoe, R., Kirkby, D., Kremin, A., Lahav, O., Landriau, M., Guillou, L. Le, Manera, M., Meisner, A., Miquel, R., Nadathur, S., Newman, J. A., Noriega, H. E., Paillas, E., Palanque-Delabrouille, N., Percival, W. J., Prada, F., Pérez-Ràfols, I., Ravoux, C., Rossi, G., Samushia, L., Sanchez, E., Saulder, C., Schlegel, D., Schubnell, M., Seo, H., Silber, J., Siudek, M., Tarlé, G., Weaver, B. A., Zhou, R.
Institutions: Cornell University, University of Pennsylvania, University of Cambridge, Institute of Astronomy and Astrophysics, Academia Sinica, Duke University, Lawrence Berkeley National Laboratory, Boston University, Universidad Nacional Autónoma de México, Royal Observatory, University of Edinburgh, University of Milan, Brera Astronomical Observatory, University College London, Universidad de La Laguna, Instituto de Astrofísica de Canarias, NSF NOIRLab, University of Pittsburgh, University of Toronto, Institució Catalana de Recerca i Estudis Avançats, Institute for High Energy Physics, Barcelona Institute of Science and Technology, Universidad de Los Andes, University of Portsmouth, University of Waterloo, Instituto de Astrofísica de Andalucía, Universitat Politècnica de Catalunya, Centre National de la Recherche Scientifique, Université Clermont Auvergne, Laboratoire de Physique de Clermont Auvergne, Sejong University, Kansas State University, Evgeni Kharadze Georgian National Astrophysical Observatory, Centro de Investigaciones Energéticas, Medioambientales y Tecnológicas, Max Planck Institute for Extraterrestrial Physics, University of Michigan, Ohio University
Language: English
Subfield: Astronomy and Astrophysics
Field: Physics and Astronomy
Domain: Physical Sciences
Open Access status: green
Funders: National Science Foundation, U.S. Department of Energy, National Aeronautics and Space Administration, Gordon and Betty Moore Foundation, Ministerio de Ciencia, Innovación y Universidades, National Energy Research Scientific Computing Center, Commissariat à l'Énergie Atomique et aux Énergies Alternatives, Office of Science, Science and Technology Facilities Council, Agencia Estatal de Investigación, Division of Astronomical Sciences, Lawrence Berkeley National Laboratory
Awards: G1044631029, G1079818582, G1105844351, G1143651532, G122673668, G1286236842, G1632040200, G1677143136, G1813527838, G1863003419, G3452655474, G3894366994, G419881185, G42916606, G4501827968, G491712853, G498139845, G5076365615, G5635532810, G593054264, Combining measurements of the Cosmic Microwave Background with galaxy clustering to probe the nature of gravity and neutrinos in the universe., G6652958823, G6876926712, G701298221, Management and Operations of the National Optical Astronomy Observatory, G7354628648, G7395345766, G7805626310, G7863371703, G8497050386, G8667377315
OpenAlex ID: W7214908356