Electron Density Structure of the Local Galactic Disk

Ocker, Stella Koch; Cordes, J. M.; Chatterjee, Shami

doi:10.3847/1538-4357/ab98f9

Cited by 52 publications

(41 citation statements)

References 58 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…We have already discussed J1643−1224 at some length in Section 4.3. It is worth emphasizing, though, that some of the complexity and chromatic dependence seen in the DM measurements and timing residuals of this pulsar almost certainly arise from the fact that it lies directly behind the HII region Sh 2-27 associated with ζ-Ophiuchi (Ocker et al 2020). This association may also be responsible for a protracted decrease in its flux density (Maitia et al 2003).…”

Section: J1643−1224mentioning

confidence: 91%

The NANOGrav 12.5 yr Data Set: Observations and Narrowband Timing of 47 Millisecond Pulsars

Alam¹,

Arzoumanian²,

Baker³

et al. 2020

ApJS

Self Cite

136

109

View full text Add to dashboard Cite

We present a new analysis of the profile data from the 47 millisecond pulsars comprising the 12.5year data set of the North American Nanohertz Observatory for Gravitational Waves (NANOGrav), which is presented in a parallel paper (Alam et al. 2020, NG12.5). Our reprocessing is performed using "wideband" timing methods, which use frequency-dependent template profiles, simultaneous time-of-arrival (TOA) and dispersion measure (DM) measurements from broadband observations, and novel analysis techniques. In particular, the wideband DM measurements are used to constrain the DM portion of the timing model. We compare the ensemble timing results to NG12.5 by examining the timing residuals, timing models, and noise model components. There is a remarkable level of agreement across all metrics considered. Our best-timed pulsars produce encouragingly similar results to those from NG12.5. In certain cases, such as high-DM pulsars with profile broadening, or sources that are weak and scintillating, wideband timing techniques prove to be beneficial, leading to more precise timing model parameters by 10 − 15%. The high-precision, multi-band measurements of several pulsars indicate frequency-dependent DMs. Compared to the narrowband analysis in NG12.5, the TOA volume is reduced by a factor of 33, which may ultimately facilitate computational speed-ups for complex pulsar timing array analyses. This first wideband pulsar timing data set is a stepping stone, and its consistent results with NG12.5 assure us that such data sets are appropriate for gravitational wave analyses.

show abstract

Section: J1643−1224mentioning

confidence: 91%

The NANOGrav 12.5 yr Data Set: Observations and Narrowband Timing of 47 Millisecond Pulsars

Alam¹,

Arzoumanian²,

Baker³

et al. 2020

ApJS

Self Cite

136

109

View full text Add to dashboard Cite

show abstract

“…Galactic pulsars show a strong Galactic latitude dependence for scattering times indicative of contributions from a strongly scattering thin disk (Cordes & Lazio 2002;Yao et al 2017) and a thick disk with a scattering scale height of one half the scale height H ne ∼ 1.6 kpc for the electron density (Ocker et al 2020). Comparison with the scattering of AGNs, which sample the entire MW halo (unlike pulsars in or near the thick disk or pulsars in the Magellanic clouds), shows no increase in scattering over that provided by the disk components.…”

Section: Scattering In Galaxy Halosmentioning

confidence: 99%

Redshift Estimation and Constraints on Intergalactic and Interstellar Media from Dispersion and Scattering of Fast Radio Bursts

Cordes,

Ocker,

Chatterjee

2021

Preprint

Self Cite

View full text Add to dashboard Cite

A sample of 14 FRBs with measured redshifts and scattering times is used to assess contributions to dispersion and scattering from the intergalactic medium (IGM), galaxy halos, and the disks of host galaxies. The IGM and galaxy halos contribute significantly to dispersion measures but evidently not to scattering, which is then dominated by host galaxies. This enables usage of scattering times for estimating DM contributions from host galaxies and also for a combined scattering-dispersion redshift estimator. Redshift estimation is calibrated using scattering of Galactic pulsars after taking into account different scattering geometries for Galactic and intergalactic lines of sight. The DM-only estimator has a bias ∼ 0.1 and RMS error ∼ 0.15 in the redshift estimate for an assumed ad-hoc value of 50 pc cm −3 for the host galaxy's DM contribution. The combined redshift estimator shows less bias by a factor of four to ten and a 20 to 40% smaller RMS error. Values for the baryonic fraction of the ionized IGM f igm 0.85 ± 0.05 optimize redshift estimation using dispersion and scattering. Our study suggests that two of the 14 candidate galaxy associations (FRB 190523 and FRB 190611) should be reconsidered.

show abstract

“…The HII region Sh 2-27, behind which PSR J1643−1224 lies, is ionised by the O-star 𝜁 Oph at a distance of 112 ± 3 pc (Ocker et al 2020), and has an inferred diameter of 0.034 kpc assuming spherical symmetry (Harvey-Smith et al 2011). The distance to the screen is then 0.112 ± 0.003 ± 0.017 kpc, with uncertainties of the distance and the HII region's radius.…”

Section: Screen Association With Sh 2-27mentioning

confidence: 99%

Modelling annual scintillation arc variations in PSR J1643-1224 using the Large European Array for Pulsars

Mall,

Main,

Antoniadis

et al. 2022

Preprint

View full text Add to dashboard Cite

In this work we study variations in the parabolic scintillation arcs of the binary millisecond pulsar PSR J1643−1224 over five years using the Large European Array for Pulsars (LEAP). The 2D power spectrum of scintillation, called the secondary spectrum, often shows a parabolic distribution of power, where the arc curvature encodes the relative velocities and distances of the pulsar, ionised interstellar medium (IISM), and Earth. We observe a clear parabolic scintillation arc which varies in curvature throughout the year. The distribution of power in the secondary spectra are inconsistent with a single scattering screen which is fully 1D, or entirely isotropic. We fit the observed arc curvature variations with two models; an isotropic scattering screen, and a model with two independent 1D screens. We measure the distance to the scattering screen to be in the range 114-223 pc, depending on the model, consistent with the known distance of the foreground large-diameter HII region Sh 2-27 (112 ± 17 pc), suggesting that it is the dominant source of scattering. We obtain only weak constraints on the pulsar's orbital inclination and angle of periastron, since the scintillation pattern is not very sensitive to the pulsar's motion, since the screen is much closer to the Earth than the pulsar. More measurements of this kind -where scattering screens can be associated with foreground objects -will help to inform the origins and distribution of scattering screens within our galaxy.

show abstract

Electron Density Structure of the Local Galactic Disk

Cited by 52 publications

References 58 publications

The NANOGrav 12.5 yr Data Set: Observations and Narrowband Timing of 47 Millisecond Pulsars

The NANOGrav 12.5 yr Data Set: Observations and Narrowband Timing of 47 Millisecond Pulsars

Redshift Estimation and Constraints on Intergalactic and Interstellar Media from Dispersion and Scattering of Fast Radio Bursts

Modelling annual scintillation arc variations in PSR J1643-1224 using the Large European Array for Pulsars

Contact Info

Product

Resources

About