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Register a new userResults from EDGES High-Band: III. New Constraints on Parameters of the Early Universe
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We present new constraints on parameters of cosmic dawn and the epoch of reionization derived from the EDGES High-Band spectrum ($90-190$ MHz). The parameters are probed by evaluating global $21$ cm signals generated with the recently developed Global21cm tool. This tool uses neural networks trained and tested on $sim 30,000$ spectra produced with semi-numerical simulations that assume the standard thermal evolution of the cosmic microwave background and the intergalactic medium. From our analysis, we constrain at $68%$ (1) the minimum virial circular velocity of star-forming halos to $V_{rm c}<19.3$ km s$^{-1}$, (2) the X-ray heating efficiency of early sources to $f_{rm X}>0.0042$, and (3) the low-energy cutoff of the X-ray spectral energy distribution to $ u_{rm min}<2.3$ keV. We also constrain the star-formation efficiency ($f_*$), the electron scattering optical depth ($tau_{rm e}$), and the mean-free path of ionizing photons ($R_{rm mfp}$). We re-compute the constraints after incorporating into the analysis four estimates for the neutral hydrogen fraction from high-$z$ quasars and galaxies, and a prior on $tau_{rm e}$ from Planck $2018$. The largest impact of the external observations is on the parameters that most directly characterize reionization. Specifically, we derive the combined $68%$ constraints $tau_{rm e}<0.063$ and $R_{rm mfp}>27.5$ Mpc. The external observations also have a significant effect on $V_{rm c}$ due to its degeneracy with $tau_{rm e}$, while the constraints on $f_*$, $f_{rm X}$, and $ u_{rm min}$, remain primarily determined by EDGES.
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We use the sky-average spectrum measured by EDGES High-Band ($90-190$ MHz) to constrain parameters of early galaxies independent of the absorption feature at $78$~MHz reported by Bowman et al. (2018). These parameters represent traditional models of cosmic dawn and the epoch of reionization produced with the 21cmFAST simulation code (Mesinger & Furlanetto 2007, Mesinger et al. 2011). The parameters considered are: (1) the UV ionizing efficiency ($zeta$), (2) minimum halo virial temperature hosting efficient star-forming galaxies ($T^{rm min}_{rm vir}$), (3) integrated soft-band X-ray luminosity ($L_{rm X,<,2,keV}/{rm SFR}$), and (4) minimum X-ray energy escaping the first galaxies ($E_{0}$), corresponding to a typical H${rm scriptstyle I}$ column density for attenuation through the interstellar medium. The High-Band spectrum disfavors high values of $T^{rm min}_{rm vir}$ and $zeta$, which correspond to signals with late absorption troughs and sharp reionization transitions. It also disfavors intermediate values of $L_{rm X,<,2,keV}/{rm SFR}$, which produce relatively deep and narrow troughs within the band. Specifically, we rule out $39.4<log_{10}left(L_{rm X,<,2,keV}/{rm SFR}right)<39.8$ ($95%$ C.L.). We then combine the EDGES High-Band data with constraints on the electron scattering optical depth from Planck and the hydrogen neutral fraction from high-$z$ quasars. This produces a lower degeneracy between $zeta$ and $T^{rm min}_{rm vir}$ than that reported in Greig & Mesinger (2017a) using the Planck and quasar constraints alone. Our main result in this combined analysis is the estimate $4.5$~$leq log_{10}left(T^{rm min}_{rm vir}/rm Kright)leq$~$5.7$ ($95%$ C.L.). We leave for future work the evaluation of $21$~cm models using simultaneously data from EDGES Low- and High-Band.
We report constraints on the global $21$ cm signal due to neutral hydrogen at redshifts $14.8 geq z geq 6.5$. We derive our constraints from low foreground observations of the average sky brightness spectrum conducted with the EDGES High-Band instrument between September $7$ and October $26$, $2015$. Observations were calibrated by accounting for the effects of antenna beam chromaticity, antenna and ground losses, signal reflections, and receiver parameters. We evaluate the consistency between the spectrum and phenomenological models for the global $21$ cm signal. For tanh-based representations of the ionization history during the epoch of reionization, we rule out, at $geq2sigma$ significance, models with duration of up to $Delta z = 1$ at $zapprox8.5$ and higher than $Delta z = 0.4$ across most of the observed redshift range under the usual assumption that the $21$ cm spin temperature is much larger than the temperature of the cosmic microwave background (CMB) during reionization. We also investigate a `cold IGM scenario that assumes perfect Ly$alpha$ coupling of the $21$ cm spin temperature to the temperature of the intergalactic medium (IGM), but that the IGM is not heated by early stars or stellar remants. Under this assumption, we reject tanh-based reionization models of duration $Delta z lesssim 2$ over most of the observed redshift range. Finally, we explore and reject a broad range of Gaussian models for the $21$ cm absorption feature expected in the First Light era. As an example, we reject $100$ mK Gaussians with duration (full width at half maximum) $Delta z leq 4$ over the range $14.2geq zgeq 6.5$ at $geq2sigma$ significance.
We present independent determinations of cosmological parameters using the distance estimator based on the established correlation between the Balmer line luminosity, L(H$beta$), and the velocity dispersion ($sigma$) for HII galaxies (HIIG). These results are based on new VLT-KMOS high spectral resolution observations of 41 high-z ($1.3 leq$ z $leq 2.6$) HIIG combined with published data for 45 high-z and 107 z $leq 0.15$ HIIG, while the cosmological analysis is based on the MultiNest MCMC procedure not considering systematic uncertainties. Using only HIIG to constrain the matter density parameter ($Omega_m$), we find $Omega_m = 0.244^{+0.040}_{-0.049}$ (stat), an improvement over our best previous cosmological parameter constraints, as indicated by a 37% increase of the FoM. The marginalised best-fit parameter values for the plane ${Omega_m; w_0}$ = ${0.249^{+0.11}_{-0.065}; -1.18^{+0.45}_{-0.41}}$ (stat) show an improvement of the cosmological parameters constraints by 40%. Combining the HIIG Hubble diagram, the cosmic microwave background (CMB) and the baryon acoustic oscillation (BAO) probes yields $Omega_m=0.298 pm 0.012$ and $w_0=-1.005 pm 0.051$, which are certainly compatible -- although less constraining -- than the solution based on the joint analysis of SNIa/CMB/BAO. An attempt to constrain the evolution of the dark energy with time (CPL model), using a joint analysis of the HIIG, CMB and BAO measurements, shows a degenerate 1$sigma$ contour of the parameters in the ${w_0,w_a}$ plane.
We present the first cosmological parameter constraints using measurements of type Ia supernovae (SNe Ia) from the Dark Energy Survey Supernova Program (DES-SN). The analysis uses a subsample of 207 spectroscopically confirmed SNe Ia from the first three years of DES-SN, combined with a low-redshift sample of 122 SNe from the literature. Our DES-SN3YR result from these 329 SNe Ia is based on a series of companion analyses and improvements covering SN Ia discovery, spectroscopic selection, photometry, calibration, distance bias corrections, and evaluation of systematic uncertainties. For a flat LCDM model we find a matter density Omega_m = 0.331 +_ 0.038. For a flat wCDM model, and combining our SN Ia constraints with those from the cosmic microwave background (CMB), we find a dark energy equation of state w = -0.978 +_ 0.059, and Omega_m = 0.321 +_ 0.018. For a flat w0waCDM model, and combining probes from SN Ia, CMB and baryon acoustic oscillations, we find w0 = -0.885 +_ 0.114 and wa = -0.387 +_ 0.430. These results are in agreement with a cosmological constant and with previous constraints using SNe Ia (Pantheon, JLA).
We present the first cosmological constraint on dark matter scattering with protons in the early Universe for the entire range of dark matter masses between 1 keV and 1 TeV. This constraint is derived from the Planck measurements of the cosmic microwave background (CMB) temperature and polarization anisotropy, and the CMB lensing anisotropy. It improves upon previous CMB constraints by many orders of magnitude, where limits are available, and closes the gap in coverage for low-mass dark matter candidates. We focus on two canonical interaction scenarios: spin-independent and spin-dependent scattering with no velocity dependence. Our results exclude (with 95% confidence) spin-independent interactions with cross sections greater than $5.3 times 10^{-27}$ cm$^2$ for 1 keV, $3.0 times 10^{-26}$ cm$^2$ for 1 MeV, $1.7 times 10^{-25}$ cm$^2$ for 1 GeV, and $1.6 times 10^{-23}$ cm$^2$ for 1 TeV dark matter mass. Finally, we discuss the implications of this study for dark matter physics and future observations.
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