A Data-driven Technique Using Millisecond Transients to Measure the Milky Way Halo

Platts, Emma; Prochaska, J. Xavier; Law, Casey J.

doi:10.3847/2041-8213/ab930a

Cited by 29 publications

(19 citation statements)

References 66 publications

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“…The mass and ionisation state of this (baryonic) halo component has been estimated in a number of ways, but remains poorly constrained. Methods include studies of (1) of the cold and hot components on the Galactic halo using high velocity clouds [113] and column densities of ionised metals (such as Silicon), (2) DM measurements to pulsars in the Magellanic Clouds [182], (3) the diffuse X-ray emission around the Milky Way [183] and (4) the ionised halos formed around galaxies in cosmological simulations [108]. The DMs of pulsars in the Large Magellanic Cloud imply DM halo > 15 pc cm −3 .…”

Section: Probing the Milky Way Ism And Ionised Halo Using Frbsmentioning

confidence: 99%

“…Constraining the halo's mass density and ionisation through DM measurements of nearby FRBs has been proposed by Platts et al [182], among others. They used pulsars and a small number of nearby FRBs to obtain a conservative upper limit on DM MW,halo of 123 pc cm −3 (95% confidence), and estimate that several thousand FRBs are required to significantly improve constraints on DM MW,halo .…”

Section: Probing the Milky Way Ism And Ionised Halo Using Frbsmentioning

confidence: 99%

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Probing the Universe with Fast Radio Bursts

Bhandari

Flynn

2021

Universe

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Fast Radio Bursts (FRBs) represent a novel tool for probing the properties of the universe at cosmological distances. The dispersion measures of FRBs, combined with the redshifts of their host galaxies, has very recently yielded a direct measurement of the baryon content of the universe, and has the potential to directly constrain the location of the “missing baryons”. The first results are consistent with the expectations of ΛCDM for the cosmic density of baryons, and have provided the first constraints on the properties of the very diffuse intergalactic medium (IGM) and circumgalactic medium (CGM) around galaxies. FRBs are the only known extragalactic sources that are compact enough to exhibit diffractive scintillation in addition to showing exponential tails which are typical of scattering in turbulent media. This will allow us to probe the turbulent properties of the circumburst medium, the host galaxy ISM/halo, and intervening halos along the path, as well as the IGM. Measurement of the Hubble constant and the dark energy parameter w can be made with FRBs, but require very large samples of localised FRBs (>103) to be effective on their own—they are best combined with other independent surveys to improve the constraints. Ionisation events, such as for He ii, leave a signature in the dispersion measure—redshift relation, and if FRBs exist prior to these times, they can be used to probe the reionisation era, although more than 103 localised FRBs are required.

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Section: Probing the Milky Way Ism And Ionised Halo Using Frbsmentioning

confidence: 99%

Section: Probing the Milky Way Ism And Ionised Halo Using Frbsmentioning

confidence: 99%

Probing the Universe with Fast Radio Bursts

Bhandari

Flynn

2021

Universe

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“…Platts, Prochaska, & Law (2020) have made a similar analysis using the DMs of Galactic pulsars combined with the DMs of published FRBs, introducing a kernel density estimation technique to find lower and upper bounds for . They place a constraint of (95% confidence interval), assuming a spherical distribution of the baryons.…”

Section: Galactic Electron Density Modelsmentioning

confidence: 99%

“…They place a constraint of (95% confidence interval), assuming a spherical distribution of the baryons. Tighter constraints may be derived using the Platts et al (2020) framework as the sample of FRBs grows, and in particular as more low-DM (i.e. nearby) FRBs are found.…”

Section: Galactic Electron Density Modelsmentioning

confidence: 99%

A comparison of Galactic electron density models using PyGEDM

Price

Flynn

Deller

2021

Publ. Astron. Soc. Aust.

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Galactic electron density distribution models are crucial tools for estimating the impact of the ionised interstellar medium on the impulsive signals from radio pulsars and fast radio bursts. The two prevailing Galactic electron density models (GEDMs) are YMW16 (Yao et al. 2017, ApJ, 835, 29) and NE2001 (Cordes & Lazio 2002, arXiv e-prints, pp astro–ph/0207156). Here, we introduce a software package PyGEDM which provides a unified application programming interface for these models and the YT20 (Yamasaki & Totani 2020, ApJ, 888, 105) model of the Galactic halo. We use PyGEDM to compute all-sky maps of Galactic dispersion measure (DM) for YMW16 and NE2001 and compare the large-scale differences between the two. In general, YMW16 predicts higher DM values towards the Galactic anticentre. YMW16 predicts higher DMs at low Galactic latitudes, but NE2001 predicts higher DMs in most other directions. We identify lines of sight for which the models are most discrepant, using pulsars with independent distance measurements. YMW16 performs better on average than NE2001, but both models show significant outliers. We suggest that future campaigns to determine pulsar distances should focus on targets where the models show large discrepancies, so future models can use those measurements to better estimate distances along those line of sight. We also suggest that the Galactic halo should be considered as a component in future GEDMs, to avoid overestimating the Galactic DM contribution for extragalactic sources such as FRBs.

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“…Such a sample is not available yet. However, Platts et al (2020) recently demonstrated a new method of inferring the MW CGM contribution to the DM of FRBs. Applying it to existing measurements they report min[DM tot ] = 63 +27 −21 ± 9 pc cm −3 , where the first error is statistical and the second -systematic.…”

Section: Model Parameter Spacementioning

confidence: 99%

Exploring the Milky Way Circumgalactic Medium in a Cosmological Context with a Semi-Analytic Model

Faerman,

Pandya,

Somerville

et al. 2021

Preprint

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We combine the Santa-Cruz Semi-Analytic Model (SAM) for galaxy formation and evolution with the circumgalactic medium (CGM) model presented in Faerman et al. (2020) to explore the CGM properties of L * galaxies. We use the SAM to generate a sample of galaxies with halo masses similar to the Milky Way (MW) halo, M vir ≈ 10 12 M ⊙ , and find that the CGM mass and mean metallicity in the sample are correlated. We use the CGM masses and metallicities of the SAM galaxies as inputs for the FSM20 model, and vary the amount of non-thermal support. The density profiles in our models can be approximated by power-law functions with slopes in the range of 0.75 < a n < 1.25, with higher non-thermal pressure resulting in flatter distributions. We explore how the gas pressure, dispersion measure, O VI-O VIII column densities, and cooling rates behave with the gas distribution and total mass. We show that for CGM masses below ∼ 3 × 10 10 M ⊙ , photoionization has a significant effect on the column densities of O VI and O VIII. The combination of different MW CGM observations favors models with similar fractions in thermal pressure, magnetic fields/cosmic rays, and turbulent support, and with M CGM ∼ 3 − 10 × 10 10 M ⊙ . The MW O VI column requires t cool /t dyn ∼ 4, independent of the gas distribution. The AGN jet-driven heating rates in the SAM are enough to offset the CGM cooling, although exact balance is not required in star-forming galaxies. We provide predictions for the columns densities of additional metal ions -N V, Ne VIII, and Mg X.

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A Data-driven Technique Using Millisecond Transients to Measure the Milky Way Halo

Cited by 29 publications

References 66 publications

Probing the Universe with Fast Radio Bursts

Probing the Universe with Fast Radio Bursts

A comparison of Galactic electron density models using PyGEDM

Exploring the Milky Way Circumgalactic Medium in a Cosmological Context with a Semi-Analytic Model

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