NE2025: An Updated Electron Density Model for the Galactic Interstellar Medium

Abstract

Free electrons in the Galactic interstellar medium (ISM) disperse and scatter coherent radio waves, by amounts that depend on the distance to the radio source. Models of the Galactic electron density are thus widely used to predict distances and scattering of compact radio sources (including pulsars, fast radio bursts (FRBs), and long-period transients), in addition to mitigating ISM foregrounds in Galactic and extragalactic studies. We use a sample of 171 precise pulsar distances, based entirely on parallaxes and globular cluster associations, as well as scattering measurements of 568 pulsars, active galactic nuclei, and masers, to update the NE2001 Galactic electron density model. We refit the thick and thin disks and three of the spiral arms. The new parameters for these large-scale components significantly repartition free electrons between the thick disk and spiral arms, thereby correcting NE2001's systematic underestimation of pulsar distance and scattering. Sightlines with excessive dispersion and scattering are used to identify new clumps that are added to the model, in addition to refining clumps that were already included (e.g., Cygnus, Vela, and Gum). The Galactic Center component is revised, yielding scattering time predictions that are $10^3$ times smaller than the Galactic Center in NE2001. The updated model, NE2025, provides a factor of $20\times$ improvement in median distance prediction accuracy and $100\%$ median improvement in scattering predictions based on DM, relative to NE2001. There is a $15\times$ improvement in median distance prediction accuracy relative to YMW16. NE2025 is available on Github and the Python Package Interface.

34 pages, 18 figures, accepted for publication in ApJ

References in corpus (94)

• Astropy: A Community Python Package for Astronomy
• The Astropy Project: Building an inclusive, open-science project and status of the v2.0 core package
• The Astropy Project: Sustaining and Growing a Community-oriented Open-source Project and the Latest Major Release (v5.0) of the Core Package
• The ATNF Pulsar Catalogue
• A New Electron Density Model for Estimation of Pulsar and FRB Distances
• Giant Gamma-ray Bubbles from Fermi-LAT: AGN Activity or Bipolar Galactic Wind?
• Trigonometric Parallaxes Of High-Mass Star Forming Regions: Our View Of The Milky Way
• The Parkes Multibeam Pulsar Survey: I. Observing and Data Analysis Systems, Discovery and Timing of 100 Pulsars
• The Velocity Distribution of Isolated Radio Pulsars
• The Parkes multibeam pulsar survey: VI. Discovery and timing of 142 pulsars and a Galactic population analysis
• A Full-Sky H-alpha Template for Microwave Foreground Prediction
• A strong magnetic field around the supermassive black hole at the centre of the Galaxy
• The WISE Catalog of Galactic HII Regions
• The NANOGrav 15-year Data Set: Observations and Timing of 68 Millisecond Pulsars
• Accurate distances to Galactic globular clusters through a combination of Gaia EDR3, HST and literature data
• Parallaxes and proper motions of interstellar masers toward the Cygnus X star-forming complex. I. Membership of the Cygnus X region
• The Vertical Structure of Warm Ionised Gas in the Milky Way
• The second data release from the European Pulsar Timing Array I. The dataset and timing analysis
• The observed spiral structure of the Milky Way
• Strong-field Gravity Tests with the Double Pulsar
• The Vela Pulsar's proper motion and parallax derived from VLBI observations
• Dense gas in the Galactic central molecular zone is warm and heated by turbulence
• Probing Galactic Halos with Fast Radio Bursts
• The NANOGrav Nine-year Data Set: Observations, Arrival Time Measurements, and Analysis of 37 Millisecond Pulsars
• On Pulsar Distance Measurements and their Uncertainties
• VLBA Measurement of Nine Pulsar Parallaxes
• The FAST Galactic Plane Pulsar Snapshot survey: I. Project design and pulsar discoveries
• Precision Astrometry with the Very Long Baseline Array: Parallaxes and Proper Motions for 14 Pulsars
• Getting Its Kicks: A VLBA Parallax for the Hyperfast Pulsar B1508+55
• The RMS Survey: Galactic distribution of massive star formation
• A Comprehensive Study of Relativistic Gravity using PSR B1534+12
• The NANOGrav 12.5 yr Data Set: Observations and Narrowband Timing of 47 Millisecond Pulsars
• Microarcsecond VLBI pulsar astrometry with PSR$\pi$ II. parallax distances for 57 pulsars
• Pulsar Parallaxes at 5 GHz with the Very Long Baseline Array
• The 1.28 GHz MeerKAT Galactic Center Mosaic
• A parallax distance and mass estimate for the transitional millisecond pulsar system J1023+0038
• Discovery of Three Pulsars from a Galactic Center Pulsar Population
• Precision southern hemisphere VLBI pulsar astrometry II: Measurement of seven parallaxes
• The Galactic Halo Contribution to the Dispersion Measure of Extragalactic Fast Radio Bursts
• The Angular Broadening of the Galactic Center Pulsar SGR J1745-29: A New Constraint on the Scattering Medium
• Modelling the Galactic distribution of free electrons
• The distance and radius of the neutron star PSR B0656+14
• Pulse Broadening Measurements from the Galactic Center Pulsar J1745--2900
• The Extension of the Transition Temperature Plasma into the Lower Galactic Halo
• Scatter broadening measurements of 124 pulsars at 327 MHz
• Finding Distant Galactic HII Regions
• FAST Globular Cluster Pulsar Survey: Twenty-Four Pulsars Discovered in Fifteen Globular Clusters
• Discovery of two pulsars towards the Galactic Centre
• The Parkes pulsar timing array second data release: Timing analysis
• A comparison of Galactic electron density models using PyGEDM
• 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
• Binary Pulsar Distances and Velocities from Gaia Data Release 2
• The neutron star mass, distance, and inclination from precision timing of the brilliant millisecond pulsar J0437$-$4715
• Redshift Estimation and Constraints on Intergalactic and Interstellar Media from Dispersion and Scattering of Fast Radio Bursts
• A radio-polarisation and rotation measure study of the Gum Nebula and its environment
• Exploring the dispersion measure of the Milky Way halo
• psrqpy: a python interface for querying the ATNF pulsar catalogue
• The High-Density Ionized Gas in the Central Parsec of the Galaxy
• SPHEREx: NASA's Near-Infrared Spectrophotmetric All-Sky Survey
• The analysis of the largest sample of multi-frequency pulsar scatter time estimates
• The gamma-ray millisecond pulsar deathline, revisited - New velocity and distance measurements
• Constraining Galaxy Haloes from the Dispersion and Scattering of Fast Radio Bursts and Pulsars
• Densities and filling factors of the DIG in the Solar neighbourhood
• The Initial Mass Function and the Surface Density Profile of NGC 6231
• The FAST Galactic Plane Pulsar Snapshot survey: VI. The discovery of 473 new pulsars
• Pulsar lensing geometry
• Modelling annual scintillation arc variations in PSR J1643-1224 using the Large European Array for Pulsars
• TRAPUM discovery of thirteen new pulsars in NGC 1851 using MeerKAT
• Locating the intense interstellar scattering towards the inner Galaxy
• Discovery and timing of ten new millisecond pulsars in the globular cluster Terzan 5
• The SPHEREx Satellite Mission
• A magnetar parallax
• Probing pulsar scattering between 120 and 280 MHz with the MWA
• Scatter broadening of pulsars in the direction of the Gum nebula
• NE2001p: A Native Python Implementation of the NE2001 Galactic Electron Density Model
• Empirical estimates of the Galactic halo contribution to the dispersion measures of extragalactic fast radio bursts using X-ray absorption
• Rotation measure variations in Galactic Centre pulsars
• Pulsar Scintillation in the Local ISM: Loop I and Beyond
• Distance of PSR B0458+46 indicated by FAST HI absorption observations
• The Galactic halo pulsar population
• A Sino-German 6cm polarisation survey of the Galactic plane IX. HII regions
• A single HII region model of the strong interstellar scattering towards Sgr A*
• Green Bank Telescope Discovery of the Redback Binary Millisecond Pulsar PSR J0212+5321
• Improving Binary Millisecond Pulsar Distances with Gaia
• Improving Distances to Binary Millisecond Pulsars with Gaia
• The FAST Galactic Plane Pulsar Snapshot survey: IV. Discovery of five fast radio bursts
• The NANOGrav 12.5-Year Data Set: Probing Interstellar Turbulence and Precision Pulsar Timing with PSR J1903+0327
• A Re-examination of the Distribution of Galactic Free Electrons
• The JWST-NIRCam View of Sagittarius C. II. Evidence for Magnetically Dominated HII Regions in the CMZ
• A millisecond pulsar position determined to 0.2 milliarcsecond precision with VLBI
• A Spatial Gap in the Sky Distribution of Fast Radio Burst Detections Coinciding with Galactic Plasma Overdensities
• VLBA astrometry of PSRs B0329+54 and B1133+16: Improved pulsar distances and comparison of global ionospheric models
• Pulsar scattering as a probe for structures in the interstellar medium

Cited by in corpus (2)

• Characterizing Pulsar Distances Using HI Kinematics
• Discovery and Timing of the First Millisecond Pulsar in NGC 6316