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
- Award ID(s):
- 1908284
- NSF-PAR ID:
- 10492477
- Publisher / Repository:
- The Astrophysical Journal
- Date Published:
- Journal Name:
- The Astrophysical Journal
- Volume:
- 943
- Issue:
- 1
- ISSN:
- 0004-637X
- Page Range / eLocation ID:
- 67
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
More Like this
-
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 volume-averaged neutral fraction of the IGM is either relatively low ( ) or close to unity ( ). In particular, the neutral fraction evolution of the IGM at the critical redshift range ofz = 6–7 is poorly constrained. We present new constraints on atz ∼ 5.1–6.8 by analyzing deep optical spectra of 53 quasars at 5.73 <z < 7.09. We derive model-independent 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 model-independent constraints on the IGM neutral hydrogen fraction atz ∼ 6.2–6.8 using quasar absorption measurements. Our results give upper limits of (1σ ), (1σ ), and (1σ ). 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 Keck/MOSFIRE rest-optical composite spectrum of 16 typical gravitationally lensed star-forming dwarf galaxies at 1.7 ≲
z ≲ 2.6 (z mean= 2.30), all chosen independent of emission-line strength. These galaxies have a median stellar mass of and a median star formation rate of . We measure the faint electron-temperature-sensitive [Oiii ]λ 4363 emission line at 2.5σ (4.1σ ) significance when considering a bootstrapped (statistical-only) uncertainty spectrum. This yields a direct-method oxygen abundance of ( ). We investigate the applicability at highz of locally calibrated oxygen-based strong-line metallicity relations, finding that the local reference calibrations of Bian et al. best reproduce (≲0.12 dex) our composite metallicity at fixed strong-line ratio. At fixedM *, our composite is well represented by thez ∼ 2.3 direct-method stellar mass—gas-phase metallicity relation (MZR) of Sanders et al. When comparing to predicted MZRs from the IllustrisTNG and FIRE simulations, having recalculated our stellar masses with more realistic nonparametric star formation histories , we find excellent agreement with the FIRE MZR. Our composite is consistent with no metallicity evolution, at fixedM *and SFR, of the locally defined fundamental metallicity relation. We measure the doublet ratio [Oii ]λ 3729/[Oii ]λ 3726 = 1.56 ± 0.32 (1.51 ± 0.12) and a corresponding electron density of ( ) when considering the bootstrapped (statistical-only) error spectrum. This result suggests that lower-mass galaxies have lower densities than higher-mass galaxies atz ∼ 2. -
Abstract We present a detection of 21 cm emission from large-scale 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), emission-line 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 ΩHi is the cosmic abundance of Hi ,b Hi is the linear bias of Hi , and 〈f μ 2〉 = 0.552 encodes the effect of redshift-space distortions at linear order. We find for LRGs (z = 0.84), for ELGs (z = 0.96), and for QSOs (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−1for 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 highest-redshift 21 cm intensity mapping measurement thus far. -
Abstract The repeating fast radio burst FRB 20190520B is localized to a galaxy at
z = 0.241, much closer than expected given its dispersion measure DM = 1205 ± 4 pc cm−3. Here we assess implications of the large DM and scattering observed from FRB 20190520B for the host galaxy’s plasma properties. A sample of 75 bursts detected with the Five-hundred-meter Aperture Spherical radio Telescope shows scattering on two scales: a mean temporal delayτ (1.41 GHz) = 10.9 ± 1.5 ms, which is attributed to the host galaxy, and a mean scintillation bandwidth Δν d(1.41 GHz) = 0.21 ± 0.01 MHz, which is attributed to the Milky Way. Balmer line measurements for the host imply an Hα emission measure (galaxy frame) EMs= 620 pc cm−6× (T /104K)0.9, implying DMHα of order the value inferred from the FRB DM budget, pc cm−3for plasma temperatures greater than the typical value 104K. Combiningτ and DMhyields a nominal constraint on the scattering amplification from the host galaxy , where describes turbulent density fluctuations andG represents the geometric leverage to scattering that depends on the location of the scattering material. For a two-screen scattering geometry whereτ arises from the host galaxy and Δν dfrom the Milky Way, the implied distance between the FRB source and dominant scattering material is ≲100 pc. The host galaxy scattering and DM contributions support a novel technique for estimating FRB redshifts using theτ –DM relation, and are consistent with previous findings that scattering of localized FRBs is largely dominated by plasma within host galaxies and the Milky Way. -
Abstract We present a multiwavelength analysis of the galaxy cluster SPT-CL J0607-4448 (SPT0607), which is one of the most distant clusters discovered by the South Pole Telescope at
z = 1.4010 ± 0.0028. The high-redshift cluster shows clear signs of being relaxed with well-regulated feedback from the active galactic nucleus (AGN) in the brightest cluster galaxy (BCG). Using Chandra X-ray data, we construct thermodynamic profiles and determine the properties of the intracluster medium. The cool-core nature of the cluster is supported by a centrally peaked density profile and low central entropy ( keV cm2), which we estimate assuming an isothermal temperature profile due to the limited spectral information given the distance to the cluster. Using the density profile and gas cooling time inferred from the X-ray data, we find a mass-cooling rate yr−1. From optical spectroscopy and photometry around the [Oii ] emission line, we estimate that the BCG star formation rate is yr−1, roughly two orders of magnitude lower than the predicted mass-cooling rate. In addition, using ATCA radio data at 2.1 GHz, we measure a radio jet power erg s−1, which is consistent with the X-ray cooling luminosity ( erg s−1withinr cool= 43 kpc). These findings suggest that SPT0607 is a relaxed, cool-core cluster with AGN-regulated cooling at an epoch shortly after cluster formation, implying that the balance between cooling and feedback can be reached quickly. We discuss the implications for these findings on the evolution of AGN feedback in galaxy clusters.