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Cool filamentary accretion extending into the interstellar medium of a quasar host galaxy

With MUSE we discovered a 120 kpc filament of [O II] emission connected to a turbulent 100 kpc nebula around a quasar at z~1

Published onOct 03, 2022
Cool filamentary accretion extending into the interstellar medium of a quasar host galaxy

Movie of MUSE [O II] emission around the luminous quasar TXS 0206-048 (z=1.13) in velocity channels spanning several hundred kilometers per second. The field of view is 330 proper kpc on a side. The observed-frame wavelength and corresponding velocity channel relative to the quasar are listed at the top right.

Complex morphology and kinematics of the giant (50-100 kpc) nebula around TXS 0206-048. The left panel displays [O II] surface brightness contours (red) over a broad-band HST (F814W) image (greyscale). Nebulae are labeled with their observed spatial scale. The right panel displays the line-of-sight emission velocity map of the [O II] nebulae (relative to the quasar) along with galaxies in the quasar’s host group. Galaxies are marked with circles and their colors encode galaxy velocity for comparison with nearby nebulae.

These figures from Johnson et al. (2022) [1] highlight the discovery of multiple giant [O II] emitting nebulae around TXS 0206-048, a luminous quasar at z=1.1317. The system includes a remarkable, narrow filamentary nebula detected as far as 170 kpc north of the quasar. It extends over 120 kpc and intersects with a 100 kpc diameter nebula surrounding the quasar host. While the kinematics of the north filament and host nebulae are complex, they coincide in velocity where they intersect.

The filament’s morphology and spatial and kinematic coincidence with the Host nebula can be explained as cool filamentary accretion from the intergalactic medium (IGM) or circumgalactic medium (CGM) into the diffuse gas and interstellar medium (ISM) surrounding the quasar host. The filament’s width relative to the estimated virial radius of the system is consistent with predictions for cool IGM accretion [2]. Alternatively, the filament could arise from the CGM of an accreting galaxy group if tidal forces resulted in elongation. Down-the-barrel UV absorption spectra of the quasar itself reveal an ionized gas inflow that is kinematically coincident with nebular emission detected 5-10 kpc north of the nucleus, suggesting that the inflow continues from halo scales into the ISM and toward the nucleus itself.

The host nebula could arise from cooling hot halo gas through precipitation and chaotic cold accretion ([3], [4]). Indeed, Chen et al. (2022) [5] demonstrated that the velocity structure function of the host nebula is consistent with expectations for Kolmogorov turbulence in an isotropic, homogeneous, and incompressible gas. See the companion video in New Results for a brief summary of that work.

These insights, based on the morphology, kinematics, and velocity structure function of these nebulae, demonstrate the promise of CGM observations of non-resonant emission lines enabled by current instruments like MUSE [6] and future ones like MIRMOS [7] and HARMONI [8].

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