Cosmic reionization was the last major phase transition of hydrogen from neutral to highly ionized in the intergalactic medium (IGM). Current observations show that the IGM is significantly neutral at
We present the KODIAQZ survey aimed to characterize the cool, photoionized gas at 2.2 ≲
 Award ID(s):
 1910414
 NSFPAR ID:
 10371228
 Publisher / Repository:
 DOI PREFIX: 10.3847
 Date Published:
 Journal Name:
 The Astrophysical Journal
 Volume:
 936
 Issue:
 2
 ISSN:
 0004637X
 Format(s):
 Medium: X Size: Article No. 156
 Size(s):
 ["Article No. 156"]
 Sponsoring Org:
 National Science Foundation
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Abstract z > 7 and largely ionized byz ∼ 5.5. However, most methods to measure the IGM neutral fraction are highly model dependent and are limited to when the volumeaveraged neutral fraction of the IGM is either relatively low ( ) or close to unity ( ${\overline{x}}_{\mathrm{H}\phantom{\rule{0.25em}{0ex}}\mathrm{I}}\lesssim {10}^{3}$ ). In particular, the neutral fraction evolution of the IGM at the critical redshift range of ${\overline{x}}_{\mathrm{H}\phantom{\rule{0.25em}{0ex}}\mathrm{I}}\sim 1$z = 6–7 is poorly constrained. We present new constraints on at ${\overline{x}}_{\mathrm{H}\phantom{\rule{0.25em}{0ex}}\mathrm{I}}$z ∼ 5.1–6.8 by analyzing deep optical spectra of 53 quasars at 5.73 <z < 7.09. We derive modelindependent upper limits on the neutral hydrogen fraction based on the fraction of “dark” pixels identified in the Lyα and Lyβ forests, without any assumptions on the IGM model or the intrinsic shape of the quasar continuum. They are the first modelindependent constraints on the IGM neutral hydrogen fraction atz ∼ 6.2–6.8 using quasar absorption measurements. Our results give upper limits of (1 ${\overline{x}}_{\mathrm{H}\phantom{\rule{0.25em}{0ex}}\mathrm{I}}(z=6.3)<0.79\pm 0.04$σ ), (1 ${\overline{x}}_{\mathrm{H}\phantom{\rule{0.25em}{0ex}}\mathrm{I}}(z=6.5)<0.87\pm 0.03$σ ), and (1 ${\overline{x}}_{\mathrm{H}\phantom{\rule{0.25em}{0ex}}\mathrm{I}}(z=6.7)<{0.94}_{0.09}^{+0.06}$σ ). The dark pixel fractions atz > 6.1 are consistent with the redshift evolution of the neutral fraction of the IGM derived from Planck 2018. 
Abstract We present a detection of 21 cm emission from largescale structure (LSS) between redshift 0.78 and 1.43 made with the Canadian Hydrogen Intensity Mapping Experiment. Radio observations acquired over 102 nights are used to construct maps that are foreground filtered and stacked on the angular and spectral locations of luminous red galaxies (LRGs), emissionline galaxies (ELGs), and quasars (QSOs) from the eBOSS clustering catalogs. We find decisive evidence for a detection when stacking on all three tracers of LSS, with the logarithm of the Bayes factor equal to 18.9 (LRG), 10.8 (ELG), and 56.3 (QSO). An alternative frequentist interpretation, based on the likelihood ratio test, yields a detection significance of 7.1
σ (LRG), 5.7σ (ELG), and 11.1σ (QSO). These are the first 21 cm intensity mapping measurements made with an interferometer. We constrain the effective clustering amplitude of neutral hydrogen (Hi ), defined as , where Ω_{Hi}is the cosmic abundance of H ${\mathit{\ue22d}}_{\mathrm{H}\phantom{\rule{0.25em}{0ex}}\mathrm{I}}\equiv {10}^{3}\phantom{\rule{0.25em}{0ex}}{\mathrm{\Omega}}_{\mathrm{H}\phantom{\rule{0.25em}{0ex}}\mathrm{I}}\left({b}_{\mathrm{H}\phantom{\rule{0.25em}{0ex}}\mathrm{I}}+\u3008\phantom{\rule{0.25em}{0ex}}f{\mu}^{2}\u3009\right)$i ,b _{Hi}is the linear bias of Hi , and 〈f μ ^{2}〉 = 0.552 encodes the effect of redshiftspace distortions at linear order. We find for LRGs ( ${\mathit{\ue22d}}_{\mathrm{H}\phantom{\rule{0.25em}{0ex}}\mathrm{I}}={1.51}_{0.97}^{+3.60}$z = 0.84), for ELGs ( ${\mathit{\ue22d}}_{\mathrm{H}\phantom{\rule{0.25em}{0ex}}\mathrm{I}}={6.76}_{3.79}^{+9.04}$z = 0.96), and for QSOs ( ${\mathit{\ue22d}}_{\mathrm{H}\phantom{\rule{0.25em}{0ex}}\mathrm{I}}={1.68}_{0.67}^{+1.10}$z = 1.20), with constraints limited by modeling uncertainties at nonlinear scales. We are also sensitive to bias in the spectroscopic redshifts of each tracer, and we find a nonzero bias Δv = − 66 ± 20 km s^{−1}for the QSOs. We split the QSO catalog into three redshift bins and have a decisive detection in each, with the upper bin atz = 1.30 producing the highestredshift 21 cm intensity mapping measurement thus far. 
Abstract We present maps tracing the fraction of dust in the form of polycyclic aromatic hydrocarbons (PAHs) in IC 5332, NGC 628, NGC 1365, and NGC 7496 from JWST/MIRI observations. We trace the PAH fraction by combining the F770W (7.7
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Abstract We present a multiwavelength analysis of the galaxy cluster SPTCL J06074448 (SPT0607), which is one of the most distant clusters discovered by the South Pole Telescope at
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Abstract We present the
z ≈ 6 type1 quasar luminosity function (QLF), based on the PanSTARRS1 (PS1) quasar survey. The PS1 sample includes 125 quasars atz ≈ 5.7–6.2, with −28 ≲M _{1450}≲ −25. With the addition of 48 fainter quasars from the SHELLQs survey, we evaluate thez ≈ 6 QLF over −28 ≲M _{1450}≲ −22. Adopting a double power law with an exponential evolution of the quasar density (Φ(z ) ∝ 10^{k(z−6)};k = −0.7), we use a maximum likelihood method to model our data. We find a break magnitude of , a faintend slope of ${M}^{*}={26.38}_{0.60}^{+0.79}\phantom{\rule{0.25em}{0ex}}\mathrm{mag}$ , and a steep brightend slope of $\alpha ={1.70}_{0.19}^{+0.29}$ . Based on our new QLF model, we determine the quasar comoving spatial density at $\beta ={3.84}_{1.21}^{+0.63}$z ≈ 6 to be . In comparison with the literature, we find the quasar density to evolve with a constant value of $n({M}_{1450}<26)={1.16}_{0.12}^{+0.13}\phantom{\rule{0.25em}{0ex}}{\mathrm{cGpc}}^{3}$k ≈ −0.7, fromz ≈ 7 toz ≈ 4. Additionally, we derive an ionizing emissivity of , based on the QLF measurement. Given standard assumptions, and the recent measurement of the mean free path by Becker et al. at ${\u03f5}_{912}(z=6)={7.23}_{1.02}^{+1.65}\times {10}^{22}\phantom{\rule{0.25em}{0ex}}\mathrm{erg}\phantom{\rule{0.25em}{0ex}}{\mathrm{s}}^{1}\phantom{\rule{0.25em}{0ex}}{\mathrm{Hz}}^{1}\phantom{\rule{0.25em}{0ex}}{\mathrm{cMpc}}^{3}$z ≈ 6, we calculate an Hi photoionizing rate of Γ_{H I}(z = 6) ≈ 6 × 10^{−16}s^{−1}, strongly disfavoring a dominant role of quasars in hydrogen reionization.