Improved Constraints on the 21 cm EoR Power Spectrum and the X-Ray Heating of the IGM with HERA Phase I Observations
Creators: name: The HERA Collaboration
name: Abdurashidova, Zara
name: Adams, Tyrone
name: Aguirre, James E.
name: Alexander, Paul
name: Ali, Zaki S.
name: Baartman, Rushelle
name: Balfour, Yanga
name: Barkana, Rennan
name: Beardsley, Adam P.
name: Bernardi, Gianni
name: Billings, Tashalee S.
name: Bowman, Judd D.
name: Bradley, Richard F.
name: Breitman, Daniela
name: Bull, Philip
name: Burba, Jacob
name: Carey, Steve
name: Carilli, Chris L.
name: Cheng, Carina
name: Choudhuri, Samir
name: DeBoer, David R.
name: Acedo, Eloy de Lera
name: Dexter, Matt
name: Dillon, Joshua S.
name: Ely, John
name: Ewall-Wice, Aaron
name: Fagnoni, Nicolas
name: Fialkov, Anastasia
name: Fritz, Randall
name: Furlanetto, Steven R.
name: Gale-Sides, Kingsley
name: Garsden, Hugh
name: Glendenning, Brian
name: Gorce, Adélie
name: Gorthi, Deepthi
name: Greig, Bradley
name: Grobbelaar, Jasper
name: Halday, Ziyaad
name: Hazelton, Bryna J.
name: Heimersheim, Stefan
name: Hewitt, Jacqueline N.
name: Hickish, Jack
name: Jacobs, Daniel C.
name: Julius, Austin
name: Kern, Nicholas S.
name: Kerrigan, Joshua
name: Kittiwisit, Piyanat
name: Kohn, Saul A.
name: Kolopanis, Matthew
name: Lanman, Adam
name: La Plante, Paul
name: Lewis, David
name: Liu, Adrian
name: Loots, Anita
name: Ma, Yin-Zhe
name: MacMahon, David H. E.
name: Malan, Lourence
name: Malgas, Keith
name: Malgas, Cresshim
name: Maree, Matthys
name: Marero, Bradley
name: Martinot, Zachary E.
name: McBride, Lisa
name: Mesinger, Andrei
name: Mirocha, Jordan
name: Molewa, Mathakane
name: Morales, Miguel F.
name: Mosiane, Tshegofalang
name: Muñoz, Julian B.
name: Murray, Steven G.
name: Nagpal, Vighnesh
name: Neben, Abraham R.
name: Nikolic, Bojan
name: Nunhokee, Chuneeta D.
name: Nuwegeld, Hans
name: Parsons, Aaron R.
name: Pascua, Robert
name: Patra, Nipanjana
name: Pieterse, Samantha
name: Qin, Yuxiang
name: Razavi-Ghods, Nima
name: Robnett, James
name: Rosie, Kathryn
name: Santos, Mario G.
name: Sims, Peter
name: Singh, Saurabh
name: Smith, Craig
name: Swarts, Hilton
name: Tan, Jianrong
name: Thyagarajan, Nithyanandan
name: Wilensky, Michael J.
name: Williams, Peter K. G.
name: van Wyngaarden, Pieter
name: Zheng, Haoxuan
Publisher: name: arXiv
Year: 2022
Subjects: subject: Cosmology and Nongalactic Astrophysics (astro-ph.CO)
subject: Astrophysics of Galaxies (astro-ph.GA)
subject: Instrumentation and Methods for Astrophysics (astro-ph.IM)
subject: FOS: Physical sciences
subject: FOS: Physical sciences

description: We report the most sensitive upper limits to date on the 21 cm epoch of reionization power spectrum using 94 nights of observing with Phase I of the Hydrogen Epoch of Reionization Array (HERA). Using similar analysis techniques as in previously reported limits (HERA Collaboration 2022a), we find at 95% confidence that $Δ^2(k = 0.34$ $h$ Mpc$^{-1}$) $\leq 457$ mK$^2$ at $z = 7.9$ and that $Δ^2 (k = 0.36$ $h$ Mpc$^{-1}) \leq 3,496$ mK$^2$ at $z = 10.4$, an improvement by a factor of 2.1 and 2.6 respectively. These limits are mostly consistent with thermal noise over a wide range of $k$ after our data quality cuts, despite performing a relatively conservative analysis designed to minimize signal loss. Our results are validated with both statistical tests on the data and end-to-end pipeline simulations. We also report updated constraints on the astrophysics of reionization and the cosmic dawn. Using multiple independent modeling and inference techniques previously employed by HERA Collaboration (2022b), we find that the intergalactic medium must have been heated above the adiabatic cooling limit at least as early as $z = 10.4$, ruling out a broad set of so-called "cold reionization" scenarios. If this heating is due to high-mass X-ray binaries during the cosmic dawn, as is generally believed, our result's 99% credible interval excludes the local relationship between soft X-ray luminosity and star formation and thus requires heating driven by evolved low-metallicity stars.
description: 57 pages, 37 figures. Updated to match the accepted ApJ version. Corresponding author: Joshua S. Dillon