The repeating fast radio burst FRB 20190520B is an anomaly of the FRB population thanks to its high dispersion measure (DM = 1205 pc cm^{−3}) despite its low redshift of
The Macquart relation describes the correlation between the dispersion measure (DM) of fast radio bursts (FRBs) and the redshift
 NSFPAR ID:
 10499004
 Publisher / Repository:
 DOI PREFIX: 10.3847
 Date Published:
 Journal Name:
 The Astrophysical Journal
 Volume:
 965
 Issue:
 1
 ISSN:
 0004637X
 Format(s):
 Medium: X Size: Article No. 57
 Size(s):
 ["Article No. 57"]
 Sponsoring Org:
 National Science Foundation
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Abstract z _{frb}= 0.241. This excess has been attributed to a large host contribution of DM_{host}≈ 900 pc cm^{−3}, far larger than any other known FRB. In this paper, we describe spectroscopic observations of the FRB 20190520B field obtained as part of the FLIMFLAM survey, which yielded 701 galaxy redshifts in the field. We find multiple foreground galaxy groups and clusters, for which we then estimated halo masses by comparing their richness with numerical simulations. We discover two separateM _{halo}> 10^{14}M _{⊙}galaxy clusters atz = 0.1867 and 0.2170 that are directly intersected by the FRB sight line within their characteristic halo radiusr _{200}. Subtracting off their estimated DM contributions, as well that of the diffuse intergalactic medium, we estimate a host contribution of or ${\mathrm{D}\mathrm{M}}_{\mathrm{h}\mathrm{o}\mathrm{s}\mathrm{t}}={430}_{220}^{+140}$ (observed frame), depending on whether we assume that the halo gas extends to ${280}_{170}^{+140}\phantom{\rule{0.25em}{0ex}}\mathrm{p}\mathrm{c}\phantom{\rule{0.25em}{0ex}}{\mathrm{c}\mathrm{m}}^{3}$r _{200}or 2 ×r _{200}. This significantly smaller DM_{host}—no longer the largest known value—is now consistent with Hα emission measures of the host galaxy without invoking unusually high gas temperatures. Combined with the observed FRB scattering timescale, we estimate the turbulent fluctuation and geometric amplification factor of the scattering layer to be , suggesting that most of the gas is close to the FRB host. This result illustrates the importance of incorporating foreground data for FRB analyses both for understanding the nature of FRBs and to realize their potential as a cosmological probe. $\tilde{F}G\approx 4.5\u201311{({\mathrm{pc}}^{2}\phantom{\rule{0.25em}{0ex}}\mathrm{km})}^{1/3}$ 
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 Fivehundredmeter 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) EM_{s}= 620 pc cm^{−6}× (T /10^{4}K)^{0.9}, implying DM_{Hα}of order the value inferred from the FRB DM budget, pc cm^{−3}for plasma temperatures greater than the typical value 10^{4}K. Combining ${\mathrm{DM}}_{\mathrm{h}}={1121}_{138}^{+89}$τ and DM_{h}yields a nominal constraint on the scattering amplification from the host galaxy , where $\tilde{F}G\phantom{\rule{0.50em}{0ex}}=\phantom{\rule{0.50em}{0ex}}{1.5}_{0.3}^{+0.8}{({\mathrm{pc}}^{2}\phantom{\rule{0.25em}{0ex}}\mathrm{km})}^{1/3}$ describes turbulent density fluctuations and $\tilde{F}$G represents the geometric leverage to scattering that depends on the location of the scattering material. For a twoscreen scattering geometry whereτ arises from the host galaxy and Δν _{d}from 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 Keck/MOSFIRE restoptical composite spectrum of 16 typical gravitationally lensed starforming dwarf galaxies at 1.7 ≲
z ≲ 2.6 (z _{mean}= 2.30), all chosen independent of emissionline strength. These galaxies have a median stellar mass of and a median star formation rate of $\mathrm{log}{({M}_{*}/{M}_{\odot})}_{\mathrm{med}}={8.29}_{0.43}^{+0.51}$ . We measure the faint electrontemperaturesensitive [O ${\mathrm{S}\mathrm{F}\mathrm{R}}_{\mathrm{H}\alpha}^{\mathrm{m}\mathrm{e}\mathrm{d}}={2.25}_{1.26}^{+2.15}\phantom{\rule{0.25em}{0ex}}{M}_{\odot}\phantom{\rule{0.25em}{0ex}}{\mathrm{y}\mathrm{r}}^{1}$iii ]λ 4363 emission line at 2.5σ (4.1σ ) significance when considering a bootstrapped (statisticalonly) uncertainty spectrum. This yields a directmethod oxygen abundance of ( $12+\mathrm{log}{(\mathrm{O}/\mathrm{H})}_{\mathrm{direct}}={7.88}_{0.22}^{+0.25}$ ). We investigate the applicability at high ${0.15}_{0.06}^{+0.12}\phantom{\rule{0.33em}{0ex}}{Z}_{\odot}$z of locally calibrated oxygenbased strongline metallicity relations, finding that the local reference calibrations of Bian et al. best reproduce (≲0.12 dex) our composite metallicity at fixed strongline ratio. At fixedM _{*}, our composite is well represented by thez ∼ 2.3 directmethod stellar mass—gasphase 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 fixed $(\mathrm{log}{({M}_{*}/{M}_{\odot})}_{\mathrm{med}}={8.92}_{0.22}^{+0.31})$M _{*}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 ( ${n}_{e}={1}_{0}^{+215}\phantom{\rule{0.33em}{0ex}}{\mathrm{cm}}^{3}$ ) when considering the bootstrapped (statisticalonly) error spectrum. This result suggests that lowermass galaxies have lower densities than highermass galaxies at ${n}_{e}={1}_{0}^{+74}\phantom{\rule{0.33em}{0ex}}{\mathrm{cm}}^{3}$z ∼ 2. 
Abstract The Makani galaxy hosts the poster child of a galactic wind on scales of the circumgalactic medium. It consists of a twoepisode wind in which the slow, outer wind originated 400 Myr ago (Episode I;
R _{I}= 20 − 50 kpc) and the fast, inner wind is 7 Myr old (Episode II;R _{II}= 0 − 20 kpc). While this wind contains ionized, neutral, and molecular gas, the physical state and mass of the most extended phase—the warm, ionized gas—are unknown. Here we present Keck optical spectra of the Makani outflow. These allow us to detect hydrogen lines out tor = 30–40 kpc and thus constrain the mass, momentum, and energy in the wind. Many collisionally excited lines are detected throughout the wind, and their line ratios are consistent with 200–400 km s^{−1}shocks that power the ionized gas, withv _{shock}=σ _{wind}. Combining shock models, densitysensitive line ratios, and mass and velocity measurements, we estimate that the ionized mass and outflow rate in the Episode II wind could be as high as those of the molecular gas: and ${M}_{\mathrm{II}}^{\mathrm{H}\mathrm{II}}\sim {M}_{\mathrm{II}}^{{\mathrm{H}}_{2}}=(12)\times {10}^{9}\phantom{\rule{0.50em}{0ex}}{M}_{\odot}$ yr^{−1}. The outer wind has slowed, so that $\mathit{dM}/{\mathit{dt}}_{\mathrm{II}}^{\mathrm{H}\mathrm{II}}\sim \mathit{dM}/{\mathit{dt}}_{\mathrm{II}}^{{\mathrm{H}}_{2}}=170250\phantom{\rule{0.25em}{0ex}}{M}_{\odot}$ yr^{−1}, but it contains more ionized gas, $\mathit{dM}/{\mathit{dt}}_{\mathrm{I}}^{\mathrm{H}\mathrm{II}}\sim 10\phantom{\rule{0.25em}{0ex}}{M}_{\odot}$ ${M}_{\mathrm{I}}^{\mathrm{H}\mathrm{II}}=5\times {10}^{9}$M _{⊙}. The momentum and energy in the recent Episode II wind imply a momentumdriven flow (p “boost” ∼7) driven by the hot ejecta and radiation pressure from the Eddingtonlimited, compact starburst. Much of the energy and momentum in the older Episode I wind may reside in a hotter phase, or lie further into the circumgalactic medium. 
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.