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The azimuthal dependence of outflows and accretion detected using O VI absorption

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posted on 2024-07-26, 13:51 authored by Glenn KacprzakGlenn Kacprzak, Sowgat Muzahid, Christopher W. Churchill, Nikole NielsenNikole Nielsen, Jane C. Charlton
We report a bimodality in the azimuthal angle (Φ) distribution of gas around galaxies traced by O vi absorption. We present the mean Φ probability distribution function of 29 Hubble Space Telescope-imaged O vi absorbing (EW > 0.1) and 24 non-absorbing (EW < 0.1) isolated galaxies (0.08 0.67) within ∼200 kpc of background quasars. We show that equivalent width (EW) is anti-correlated with impact parameter and O vi covering fraction decreases from 80% within 50 kpc to 33% at 200 kpc. The presence of O vi absorption is azimuthally dependent and occurs between ± 10°-20° of the galaxy projected major axis and within ± 30° of the projected minor axis. We find higher EWs along the projected minor axis with weaker EWs along the project major axis. Highly inclined galaxies have the lowest covering fractions due to minimized outflow/inflow cross-section geometry. Absorbing galaxies also have bluer colors while non-absorbers have redder colors, suggesting that star formation is a key driver in the O vi detection rate. O vi surrounding blue galaxies exists primarily along the projected minor axis with wide opening angles while O vi surrounding red galaxies exists primarily along the projected major axis with smaller opening angles, which may explain why absorption around red galaxies is less frequently detected. Our results are consistent with a circumgalactic medium (CGM) originating from major axis-fed inflows/recycled gas and from minor axis-driven outflows. Non-detected O vi occurs between Φ = 20°-60°, suggesting that O vi is not mixed throughout the CGM and remains confined within the outflows and the disk-plane. We find low O vi covering fractions within of the projected major axis, suggesting that cool dense gas resides in a narrow planer geometry surrounded by diffuse O vi gas.

Funding

Simulating galaxy ecosystems

Australian Research Council

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ISSN

1538-4357

Journal title

The Astrophysical Journal

Volume

815

Issue

1

Pagination

12 pp

Publisher

IOP Publishing

Copyright statement

Copyright © 2015 The American Astronomical Society. The published version is reproduced in accordance with the copyright policy of the publisher and can be also be located at http://doi.org/10.1088/0004-637X/815/1/22

Language

eng

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