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Probing the circumgalactic medium of active galactic nuclei with background quasars

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posted on 2024-07-26, 14:10 authored by Glenn KacprzakGlenn Kacprzak, C. W. Churchill, Michael MurphyMichael Murphy, Jeff CookeJeff Cooke
We performed a detailed study of the extended cool gas, traced by Mgii absorption [Wr(2796) > 0.3 Å], surrounding 14 narrow-line active galactic nuclei (AGNs) at 0.12 6 z 6 0.22 using background quasar sight-lines. The background quasars probe the AGNs at projected distances of 60 6 D 6 265 kpc. We find that, between 100 6 D 6 200 kpc, AGNs appear to have lower Mgii gas covering fractions (0.09+0.18 −0.08) than quasars (0.47+0.16 −0.15) and possibly lower than in active field galaxies (0.25+0.11 −0.09). We do not find a statistically significant azimuthal angle dependence for theMgii covering fraction aroundAGNs, though the data hint at one. We also study the ‘down-the-barrel’ outflow properties of the AGNs themselves and detect intrinsic NaiD absorption in 8/8 systems and intrinsic Mgii absorption in 2/2 systems, demonstrating that the AGNs have significant reservoirs of cool gas. We find that 6/8 NaiD and 2/2 Mgii intrinsic systems contain blueshifted absorption with _v > 50 km s−1, indicating outflowing gas. The 2/2 intrinsic Mgii systems have outflow velocities a factor of ∼ 4 higher than the NaiD outflow velocities. Our results are consistent with AGN-driven outflows destroying the cool gas within their halos, which dramatically decreases their cool gas covering fraction, while star-burst driven winds are expelling cool gas into their circumgalactic media (CGM). This picture appears contrary to quasar–quasar pair studies which show that the quasar CGM contains significant amounts of cool gas whereas intrinsic gas found ‘downthe-barrel’ of quasars reveals no cool gas. We discuss how these results are complementary and provide support for the AGN unified model.

Funding

Pristine fuel for early galaxies

Australian Research Council

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Detecting the deaths of the first stars: Investigating the physical processes in the early Universe

Australian Research Council

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ISSN

0035-8711

Journal title

Monthly Notices of the Royal Astronomical Society

Volume

446

Issue

3

Pagination

8 pp

Publisher

Oxford University Press

Copyright statement

Copyright © 2014 RAS. This article has been accepted for publication in the Monthly Notices of the Royal Astronomical Society ©: 2015 The authors. Published by Oxford University Press on behalf of the Royal Astronomical Society.

Language

eng

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