Modelling the Galactic distribution of free electrons

Abstract

In this paper we test 8 models of the free electron distribution in the Milky Way that have been published previously, and we introduce 4 additional models that explore the parameter space of possible models further. These new models consist of a simple exponential thick disk model, and updated versions of the models by Taylor & Cordes and Cordes & Lazio with more extended thick disks. The final model we introduce uses the observed H-alpha intensity as a proxy for the total electron column density, also known as the dispersion measure (DM). We use the latest available data sets of pulsars with accurate distances (through parallax measurements or association with globular clusters) to optimise the parameters in these models. In the process of fitting a new scale height for the thick disk in the model by Cordes & Lazio we discuss why this thick disk cannot be replaced by the thick disk that Gaensler et al. advocated in a recent paper. In the second part of our paper we test how well the different models can predict the DMs of these pulsars at known distances. Almost all models perform well, in that they predict DMs within a factor of 1.5-2 of the observed DMs for about 75% of the lines of sight. This is somewhat surprising since the models we tested range from very simple models that only contain a single exponential thick disk to very complex models like the model by Cordes & Lazio. We show that the model by Taylor & Cordes that we updated with a more extended thick disk consistently performs better than the other models we tested. Finally, we analyse which sightlines have DMs that prove difficult to predict by most models, which indicates the presence of local features in the ISM between us and the pulsar. (abridged)

16 pages, 10 figures, 5 tables. Accepted for publication in the Monthly Notices of the RAS by the Royal Astronomical Society and Blackwell Publishing

References in corpus (10)

• The ATNF Pulsar Catalogue
• The relativistic pulsar-white dwarf binary PSR J1738+0333 II. The most stringent test of scalar-tensor gravity
• The Vertical Structure of Warm Ionised Gas in the Milky Way
• Rotation Measures of Extragalactic Sources Behind the Southern Galactic Plane: New Insights into the Large-Scale Magnetic Field of the Inner Milky Way
• New pulsar rotation measures and the Galactic magnetic field
• The Structure of Molecular Clouds: I - All Sky Near Infrared Extinction Maps
• Observational constraints on models for the interstellar magnetic field in the Galactic disk
• Densities and filling factors of the DIG in the Solar neighbourhood
• Magnetic field near the central region of the Galaxy: Rotation measure of extragalactic sources
• Errors in kinematic distances and our image of the Milky Way Galaxy

Cited by in corpus (74)

• A New Electron Density Model for Estimation of Pulsar and FRB Distances
• A census of baryons in the Universe from localized fast radio bursts
• High-precision timing of 42 millisecond pulsars with the European Pulsar Timing Array
• Stars, Gas, and Dark Matter in the Solar Neighborhood
• The magnetic field and turbulence of the cosmic web measured using a brilliant fast radio burst
• Galactic synchrotron emission with cosmic ray propagation models
• Fast radio bursts as a cosmic probe?
• The Galactic Position Dependence of Fast Radio Bursts and the Discovery of FRB 011025
• Millisecond pulsars and the Galactic Center gamma-ray excess: the importance of luminosity function and secondary emission
• Pulsar Spin-Velocity Alignment: Kinematic Ages, Birth Periods and Braking Indices
• Low-frequency Faraday rotation measures towards pulsars using LOFAR: probing the 3-D Galactic halo magnetic field
• The LOFAR Tied-Array All-Sky Survey (LOTAAS): Survey overview and initial pulsar discoveries
• PsrPopPy: An open-source package for pulsar population simulations
• Pulsar polarisation below 200 MHz: Average profiles and propagation effects
• A new limit on local Lorentz invariance violation of gravity from solitary pulsars
• The Local Dark Matter Density from SDSS-SEGUE G-dwarfs
• Linear polarization structures in LOFAR observations of the interstellar medium in the 3C196 field
• Extragalactic dispersion measures of fast radio bursts
• The Coherent Magnetic Field of the Milky Way
• IMAGINE: A comprehensive view of the interstellar medium, Galactic magnetic fields and cosmic rays
• The High Time Resolution Universe Pulsar Survey VIII: The Galactic millisecond pulsar population
• The NANOGrav Nine-year Data Set: Astrometric Measurements of 37 Millisecond Pulsars
• Electron Density Structure of the Local Galactic Disk
• An FRB Sent Me a DM: Constraining the Electron Column of the Milky Way Halo with Fast Radio Burst Dispersion Measures from CHIME/FRB
• Fast Radio Bursts
• Plasma turbulence in the interstellar medium
• The High Time Resolution Universe Pulsar Survey X: Discovery of four millisecond pulsars and updated timing solutions of a further 12
• Discovery of 105 Hz coherent pulsations in the ultracompact binary IGR J16597-3704
• Distinguishing Dark Matter from Unresolved Point Sources in the Inner Galaxy with Photon Statistics
• Galactic interstellar turbulence in the southern sky seen through spatial gradients of the polarization vector
• Constraints from Faraday rotation on the magnetic field structure in the Galactic halo
• A Galactic Origin for the Fast Radio Burst FRB010621
• Diffuse Ionized Gas in Simulations of Multiphase, Star-Forming Galactic Disks
• Variable Heating and Flaring of Three Redback Millisecond Pulsar Companions
• Cosmic Magnetism in Centimeter and Meter Wavelength Radio Astronomy
• Post fall-back evolution of multipolar magnetic fields and radio pulsar activation
• Timing, polarimetry and physics of the bright, nearby millisecond pulsar PSR J0437-4715 - a single-pulse perspective
• Numerical investigation of plasma-driven superradiant instabilities
• A Data-Driven Technique Using Millisecond Transients to Measure the Milky Way Halo
• Interstellar Gas and a Dark Disk
• Estimating the GeV Emission of Millisecond Pulsars in Dwarf Spheroidal Galaxies
• The relation between magnetic and material arms in models for spiral galaxies
• An Ultra-long Wavelength Sky Model with Absorption Effect
• Radio polarimetry of Galactic centre pulsars
• M82 - A radio continuum and polarisation study II. Polarisation and rotation measures
• The High Time Resolution Universe Pulsar Survey - VII: discovery of five millisecond pulsars and the different luminosity properties of binary and isolated recycled pulsars
• The Fan Region at 1.5 GHz. I: Polarized synchrotron emission extending beyond the Perseus Arm
• Planck intermediate results. XXIII. Galactic plane emission components derived from Planck with ancillary data
• Classifying RRATs and FRBs
• Six Faint Gamma-ray Pulsars Seen with the Fermi Large Area Telescope -- Towards a Sample Blending into the Background
• The Complex Large-scale Magnetic Fields in the First Galactic Quadrant as Revealed by the Faraday Depth Profile Disparity
• Disentangling the Faraday rotation sky
• Constraining Redshifts of Unlocalised Fast Radio Bursts
• The Galactic Millisecond Pulsar Population
• Probability distribution functions of gas in M31 and M51
• Axion Echos from the Supernova Graveyard
• A LOFAR search for steep-spectrum pulsars in Supernova Remnants and Pulsar Wind Nebulae
• Superradiance in massive vector fields with spatially varying mass
• Magnetic fields in star-forming systems (II): examining dust polarization, the Zeeman effect, and the Faraday rotation measure as magnetic field tracers
• Constraining HeII Reionization Detection Uncertainties via Fast Radio Bursts
• The optical companion to the intermediate mass millisecond pulsar J1439-5501 in the Galactic field
• Magnetic fields near the peripheries of galactic discs
• Tomography of the Galactic free electron density with the Square Kilometer Array
• The Thousand-Pulsar-Array programme on MeerKAT VII: Polarisation properties of pulsars in the Magellanic Clouds
• NE2025: An Updated Electron Density Model for the Galactic Interstellar Medium
• The Fast Radio Burst Population Energy Distribution
• On the Galactic radio signal from stimulated decay of axion dark matter
• A new method of reconstructing Galactic three-dimensional structures using ultralong-wavelength radio observations
• When Dark Matter interacts with Cosmic Rays or Interstellar Matter: A Morphological Study
• A new method to probe the thermal electron content of the Galaxy through spectral analysis of background sources
• Observational Signatures of Galactic Turbulent Dynamos
• Modeling Local Bubble analogs II: Synthetic Faraday rotation maps
• FRBSTATS: A web-based platform for visualization of fast radio burst properties
• A Monte Carlo Implementation of Galactic Free-Free Emission for the EoR Foreground Models