IERS B1946+708

Lore & Background

IERS B1946+708 is an elliptical galaxy with an inclined disk measured at 600 parsecs in radius via Hubble Space Telescope three-band imaging. Its nuclear regions are much redder than its outer regions, with B and R band magnitude differences of 2–3. A companion galaxy lies 67 kiloparsecs away. The radio source is compact and exhibits an S-symmetry, with the radio core located midway between two hotspots in the north and south. The hotspots have an expansion velocity of 0.024c, corresponding to an age of 4000 ± 1000 years, while the core has an inverted spectrum. Two narrow jets emerge from the core, bending and ending in the hotspot regions; these jets contain four components moving at speeds between 0.6 and 0.9c, with the fastest at 1.09 h⁻¹ c. Low polarization in the jet components indicates Faraday depolarization by ionized gas and a tangled magnetic field. Neutral hydrogen has been detected in all components, with narrow lines toward the north hotspot likely caused by H I clouds associated with a warm gas region. X-ray observations by BeppoSAX revealed strong iron K-alpha emission lines. H I observations by A.B. Peck and G.B. Taylor found multi-peaked absorption across the radio continuum, with maximum column density toward the core and a velocity dispersion of 350 km/s, suggesting a circumnuclear disk.

Reader's Guide

IERS B1946+708 is significant as a compact symmetric object (CSO) with a gigahertz peaked spectrum, providing a laboratory for studying young radio galaxies and their interaction with the interstellar medium. Its well-resolved jet structure, with components moving at relativistic speeds up to 1.09 h⁻¹ c, and the measured hotspot expansion age of 4000 ± 1000 years indicate a young, active source. The detection of neutral hydrogen absorption with multi-peaked profiles and a circumnuclear disk suggests complex gas dynamics near the active nucleus. The strong iron K-alpha emission line observed by BeppoSAX points to the presence of dense, ionized material in the nuclear region. The low polarization and Faraday depolarization in the jets reveal the influence of ionized gas and tangled magnetic fields. The galaxy's inclined disk and redder nuclear regions, along with a companion 67 kiloparsecs away, place it in a broader context of galaxy interactions and evolution. Its legacy lies in its detailed multi-wavelength characterization, from radio to X-rays, which informs models of jet propagation, feedback, and the early stages of radio galaxy evolution.

Did You Know?

• The fastest jet component moves at 1.09 h⁻¹ c.
• X-ray observations by BeppoSAX detected strong iron K-alpha emission lines in its spectrum.