NOCTURNE. III. Unidentified variable emission in the nuclear regions of PKS 2153-69

TL;DR

This study uses advanced integral field spectroscopy to isolate and analyze the central regions of a Type 1 AGN, revealing a unique high-velocity, short-term variable emission component in PKS 2153-68.

Contribution

It introduces a novel method for modeling and subtracting QSO light in Type 1 AGN, enabling detailed study of the nuclear emission and discovery of an unprecedented high-velocity variable feature.

Findings

Detection of a high-velocity (~25000 km/s) variable emission component.

Identification of a short timescale variability (≤1 year) in the nuclear region.

Successful separation of host galaxy and AGN spectra using MUSE WFM data.

Abstract

Historically, the study of the central regions of Type 1 AGN has been limited by the combination of the host galaxy spectrum with strong emission from the accretion disk and NLR/BLR, which prevented us from accurately probing the galactic and AGN properties in the central regions. Integral field spectroscopy allows us to correct for this effect and study both the unobscured cores of AGN host galaxies as well as the uncontaminated spectra of their central engines with unprecedented precision. Using MUSE WFM observations, in this work, we present a combined method for modelling and subtracting QSO light in type-1 AGN alongside results for one such source, PKS 2153-68 (z=0.028), both jetted and gamma-ray emitting. After separating the host galaxy and AGN spectra, we discuss the discovery of an unresolved and yet-to-be-identified high-velocity ($\sim$25000 km/s) short timescale ($\leq$1 yr) variable emission, unlike anything observed in other variable AGN.