Measured
Total DM = 349.349 ± 0.006 pc cm⁻³ and the ν⁻² sweep.
REAL CHIME/FRB CATALOG DATA · 400–800 MHz
Six seconds
through the
cosmic web.
A millisecond radio flash reached CHIME’s high-frequency channels first. Its lower frequencies arrived 6.79 seconds later. That delay measures every free electron between a nearby spiral galaxy and Earth—but not where each electron lives.
Follow the signal ↓800 MHz / early400 MHz / late
—pc cm⁻³ total DM
—catalogue S/N
z = 0.0337host redshift
16.35 dactivity period
01 · DECODE THE MEASUREMENT
Dispersion measure is an electron count along a line—not a distance meter.
Cold plasma delays low radio frequencies by an amount proportional to DM × ν⁻². The curve is a strong astrophysical signature. But total DM combines our Galaxy, its halo, intergalactic gas, the host galaxy and the immediate burst environment.
arrival delayΔt = kDM DM (ν⁻² − νref⁻²)For this measured DM, 400 MHz trails 800 MHz by 6.79398 s.
02 · THREE READINGS OF ONE BURST
Signal → population → sightline.
Loading 535 public CHIME events…
03 · A GALAXY CHANGES THE QUESTION
Localization supplies the missing distance.
SDSS J015800.28+654253.0
Very-long-baseline radio observations placed the repeater in a star-forming region of a massive spiral galaxy at z = 0.0337 ± 0.0002. With an independent redshift, DM becomes a probe of intervening matter rather than a guessed distance.
- Position
- RA 29.5°, Dec +65.72°
- Environment
- star-forming region
- Key caution
- low Galactic latitude +3.73°
04 · SCIENTIFIC BOUNDARY
The result is the disagreement.
Model-dependent
NE2001 leaves 150.4 pc cm⁻³ beyond the Galactic disk; YMW16 leaves only 24.5.
Not identified here
A unique IGM column, host contribution, DM-only redshift or progenitor mechanism.
REPRODUCIBLE DATA PATH
535 events, not five anchor dots.
- SourcePublic CHIME/FRB Catalog 1 JSON
- ExtractDM, uncertainty, S/N, sky position and Galactic-model excess
- DeriveExact cold-plasma curve, distribution percentile and foreground comparison
- VerifySource hash and numerical regression tests