PG 1004+130: Hybrid Morphology Source or a Restarted FRII? A uGMRT Polarimetric Investigation

Abstract

We present the polarization image of the hybrid morphology and broad absorption line quasar PG 1004+130 at 694 MHz obtained with the upgraded Giant Metrewave Radio Telescope. We detect linear polarization in this source’s core, jets, and lobes. The visible discontinuity in total intensity between the inner jets and the kiloparsec-scale lobes suggests that the source is restarted. The inferred poloidal magnetic ( B -) field structure in the inner jet is consistent with that observed in Fanaroff–Riley (FR) type II sources, as are the B -fields aligned with the lobe edges. Moreover, archival Chandra and XMM-Newton data indicate that PG 1004+130 displays several FRII-jetlike properties in X-rays. We conclude that PG 1004+130 is a restarted quasar, with both episodes of activity being FRII type. The spectral index images show the presence of an inverted spectrum core ( α = +0.30 ± 0.01) and a steep spectrum inner jet ( α = −0.62 ± 0.06) surrounded by much steeper lobe emission ( α ≈ −1.2 ± 0.1), consistent with the suggestion that the lobes are from a previous activity episode. The spectral age difference between the two activity episodes is likely to be small (<1.2 × 10 ^7 yr), in comparison to the lobe ages (∼3.3 × 10 ^7 yr). The inferred B -fields in the lobes are suggestive of turbulence and the mixing of plasma. This may account for the absence of X-ray cavities around this source, similar to what is observed in M87's radio halo region. The depolarization models reveal that thermal gas of mass ∼(2.4 ± 0.9) × 10 ^9 M _⊙ is mixed with the nonthermal plasma in the lobes of PG 1004+130.

Keywords

• Quasars
• Radio loud quasars
• Fanaroff-Riley radio galaxies
• Relativistic jets
• Spectral index
• Polarimetry