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Published February 20, 2022 | Accepted Version + Published
Journal Article Open

Evidence for Cold-stream to Hot-accretion Transition as Traced by Lyα Emission from Groups and Clusters at 2 < z < 3.3

Abstract

We present Keck Cosmic Web Imager observations of giant Lyα halos surrounding nine galaxy groups and clusters at 2 < z < α luminosity and the expected baryonic accretion rate (BAR), with increasing elongation above the transition mass (M_(stream)). This implies a modulation of the share of BAR that remains cold, diminishing quasi-linearly (logarithmic slope of 0.97 ± 0.19, 5σ significance) with the halo to M_(stream) mass ratio. The integrated star formation rates (SFRs) and active galactic nucleus (AGN) bolometric luminosities display a potentially consistent decrease, albeit significant only at 2.6σ and 1.3σ, respectively. The higher scatter in these tracers suggests the Lyα emission might be mostly a direct product of cold accretion in these structures rather than indirect, mediated by outflows and photoionization from SFR and AGNs; this is also supported by energetics considerations. Below M_(stream) (cold-stream regime), we measure L_(Lyα)/BAR = 10^(40.51 ± 0.16) erg s⁻1 M_⊙⁻¹ yr, consistent with predictions, and SFR/BAR = 10^(−0.54 ± 0.23): on average, 30₋₁₀⁺²⁰% of the cold streams go into stars. Above M_(stream) (hot-accretion regime), L_(Lyα) is set by M_(stream) (within 0.2 dex scatter in our sample), independent of the halo mass but rising 10-fold from z = 2 to 3.

Additional Information

© 2022. The Author(s). Published by the American Astronomical Society. Original content from this work may be used under the terms of the Creative Commons Attribution 4.0 licence. Any further distribution of this work must maintain attribution to the author(s) and the title of the work, journal citation and DOI. Received 2021 November 23; revised 2022 February 5; accepted 2022 February 7; published 2022 February 21. We thank Dawn Erb for sharing calibrations, Sebastiano Cantalupo for his CubEx code and discussions, and the referee for a constructive report. R.M.R. acknowledges GO-15910.002 from the Space Telescope Science Institute. Data were obtained at the W. M. Keck Observatory, operated as a scientific partnership among the California Institute of Technology, the University of California, and the National Aeronautics and Space Administration, made possible by the generous financial support of the W. M. Keck Foundation. The authors also acknowledge the indigenous Hawaiian community and are grateful for the opportunity to collect data from the summit of Maunakea.

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Published - Daddi_2022_ApJL_926_L21.pdf

Accepted Version - 2202.03715.pdf

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Additional details

Created:
August 22, 2023
Modified:
October 23, 2023