Probing Baryons with the Kinematic Sunyae Zel'dovich Effect and Machine Learning Derived Peculiar Velocities using DESI DR2 and ACT DR6

@misc{gong2026probing,
  title = {{Probing Baryons with the Kinematic Sunyae Zel'dovich Effect and Machine Learning Derived Peculiar Velocities using DESI DR2 and ACT DR6}},
  author = {Yulin Gong and Rachel Bean and Patricio A Gallardo and Boryana Hadzhiyska and Yun-Hsin Hsu and Jenna Moore and Eve M Vavagiakis and Nicholas Battaglia and J Aguilar and S Ahlen and A Aviles and F Beutler and D Bianchi and D Brooks and A Carnero Rosell and T Claybaugh and A de la Macorra and Arjun Dey and Biprateep Dey and P Doel and A Font-Ribera and J.E Forero-Romero and E Gaztañaga and G Gutierrez and K Honscheid and S Juneau and T Karim and R Kehoe and D Kirkby and A Kremin and O Lahav and M Landriau and L Le Guillou and M Manera and A Meisner and R Miquel and S Nadathur and J.A Newman and H.E Noriega and E Paillas and N Palanque-Delabrouille and W.J Percival and F Prada and I Pérez-Ràfols and C Ravoux and G Rossi and L Samushia and E Sanchez and C Saulder and D Schlegel and M Schubnell and H Seo and J Silber and M Siudek and G Tarlé and B.A Weaver and R Zhou},
  howpublished = {HAL},
  year = {2026},
  month = sep,
  doi = {10.48550/arxiv.2609.36355},
  eprint = {2609.36355},
  archivePrefix = {arXiv},
  url = {https://hal.science/hal-05781883v1},
}

TY  - UNPB
TI  - Probing Baryons with the Kinematic Sunyae Zel'dovich Effect and Machine Learning Derived Peculiar Velocities using DESI DR2 and ACT DR6
AU  - Yulin Gong
AU  - Rachel Bean
AU  - Patricio A Gallardo
AU  - Boryana Hadzhiyska
AU  - Yun-Hsin Hsu
AU  - Jenna Moore
AU  - Eve M Vavagiakis
AU  - Nicholas Battaglia
AU  - J Aguilar
AU  - S Ahlen
AU  - A Aviles
AU  - F Beutler
AU  - D Bianchi
AU  - D Brooks
AU  - A Carnero Rosell
AU  - T Claybaugh
AU  - A de la Macorra
AU  - Arjun Dey
AU  - Biprateep Dey
AU  - P Doel
AU  - A Font-Ribera
AU  - J.E Forero-Romero
AU  - E Gaztañaga
AU  - G Gutierrez
AU  - K Honscheid
AU  - S Juneau
AU  - T Karim
AU  - R Kehoe
AU  - D Kirkby
AU  - A Kremin
AU  - O Lahav
AU  - M Landriau
AU  - L Le Guillou
AU  - M Manera
AU  - A Meisner
AU  - R Miquel
AU  - S Nadathur
AU  - J.A Newman
AU  - H.E Noriega
AU  - E Paillas
AU  - N Palanque-Delabrouille
AU  - W.J Percival
AU  - F Prada
AU  - I Pérez-Ràfols
AU  - C Ravoux
AU  - G Rossi
AU  - L Samushia
AU  - E Sanchez
AU  - C Saulder
AU  - D Schlegel
AU  - M Schubnell
AU  - H Seo
AU  - J Silber
AU  - M Siudek
AU  - G Tarlé
AU  - B.A Weaver
AU  - R Zhou
PY  - 2026
DA  - 2026/09/28
PB  - HAL
DO  - 10.48550/arxiv.2609.36355
UR  - https://hal.science/hal-05781883v1
AB  - 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.
ER  -