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

2022; IOP Publishing; Volume: 926; Issue: 2 Linguagem: Inglês

10.3847/2041-8213/ac531f

2041-8213

E. Daddi, R. Michael Rich, Francesco Valentino, Shuowen Jin, I. Delvecchio, Daizhong Liu, V. Strazzullo, James D. Neill, R. Gobat, A. Finoguenov, F. Bournaud, D. Elbaz, Boris S. Kalita, Dónal O’Sullivan, Tao Wang,

Astrophysics and Star Formation Studies

Abstract We present Keck Cosmic Web Imager observations of giant Ly α halos surrounding nine galaxy groups and clusters at 2 < z < 3.3, including five new detections and one upper limit. We find observational evidence for the cold-stream to hot-accretion transition predicted by theory by measuring a decrease in the ratio between the spatially extended Ly 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, 5 σ 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 2.6 σ and 1.3 σ , respectively. The higher scatter in these tracers suggests the Ly α 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 Ly α /BAR = 10 40.51±0.16 erg s −1 <?CDATA ${M}_{\odot }^{-1}$?> M ⊙ − 1 yr, consistent with predictions, and SFR/BAR = 10 −0.54±0.23 : on average, <?CDATA ${30}_{-10}^{+20}$?> 30 − 10 + 20 % of the cold streams go into stars. Above M stream (hot-accretion regime), L Ly α 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.