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

Miguel Coloma Puga, Marco Berton, Pierpaolo Condò, Abigail García-Pérez, Emilia Järvelä, Anne Lähteenmäki, Swayamtrupta Panda

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.

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

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 (25000 km/s) short timescale (1 yr) variable emission, unlike anything observed in other variable AGN.
Paper Structure (6 sections, 4 figures)

This paper contains 6 sections, 4 figures.

Table of Contents

  1. INTRODUCTION
  2. METHODS
  3. RESULTS
  4. QSO-host deconvolution
  5. Variable nuclear emission
  6. DISCUSSION

Figures (4)

  • Figure 1: RGB image of PKS 2153-69. The blue band corresponds to [O III]$\lambda$5007, the green band corresponds to the stellar continuum, and the red band corresponds to H$\alpha$. The black cross marks the AGN position
  • Figure 2: Deconvolved spectra of the AGN and host galaxy emission of PKS 2153-69. Wavelengths are in rest frame
  • Figure 3: Comparison between the available nuclear optical spectra of PKS 2153-69. Both the MUSE and EFOSC2 spectra were extracted using an aperture the size of the PSF on each given night in order to maximize the signal-to-noise.
  • Figure 4: Spectral modeling of the H$\beta$/[O III] emission in PKS 2153-69 for two different epochs. At the bottom of each plot are the residuals expressed as the relative fraction of the flux. The dashed lines mark the measured noise levels.