Chandra high resolution spectroscopy of the circumnuclear matter in the Broad Line Radio Galaxy 3C445

TL;DR

This paper reports high-resolution Chandra X-ray spectroscopy of the Broad Line Radio Galaxy 3C 445, revealing highly ionized, photoionized gas in the nucleus, likely originating from the Broad Line Region and associated with an outflowing disk wind.

Contribution

First detailed high-resolution X-ray spectral analysis of 3C 445 showing ionized emission and absorption lines, indicating the location and nature of circumnuclear gas in a BLRG.

Findings

Detection of highly ionized emission lines from O, Ne, Mg, Si.

Evidence for photoionized gas with high density and velocity broadening.

Identification of an outflowing, clumpy accretion disk wind.

Abstract

We present evidence for X-ray line emitting and absorbing gas in the nucleus of the Broad-Line Radio Galaxy (BLRG), 3C 445. A 200ks Chandra LETG observation of 3C 445 reveals the presence of several highly ionized emission lines in the soft X-ray spectrum, primarily from the He and H-like ions of O, Ne, Mg and Si. Radiative recombination emission is detected from O VII and O VIII, indicating that the emitting gas is photoionized. The He-like emission appears to be resolved into forbidden and intercombination line components, which implies a high density of >10^{10} cm^{-3}, while the Oxygen lines are velocity broadened with a mean width of ~2600 km s^{-1} (FWHM). The density and widths of the ionized lines indicate an origin of the gas on sub-parsec scales in the Broad Line Region (BLR).The X-ray continuum of 3C 445 is heavily obscured either by a partial coverer or by a photoionized absorber of column density N_{H}=2x10^{23} cm^{-2} and ionization parameter log(xi)=1.4 erg cm s^{-1}. However the view of the X-ray line emission is unobscured, which requires the absorber to be located at radii well within any parsec scale molecular torus. Instead, we suggest that the X-ray absorber in 3C 445 may be associated with an outflowing, but clumpy, accretion disk wind with an observed outflow velocity of ~10000 km/s.