Revisiting FUSE O VI Emission in Galaxy Halos. (arXiv:2103.05008v2 [astro-ph.GA] UPDATED)
<a href="http://arxiv.org/find/astro-ph/1/au:+Chung_H/0/1/0/all/0/1">Haeun Chung</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Vargas_C/0/1/0/all/0/1">Carlos J. Vargas</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Hamden_E/0/1/0/all/0/1">Erika Hamden</a>
A significant fraction of baryons in galaxies are in the form of diffuse gas
of the circumgalactic medium (CGM). One critical component of the multi-phases
of CGM, the so-called “coronal” warm-hot phase gas ($rm 10^{5}-10^{6}$ K)
traced by O VI 1031.93, 1037.62 r{A} resonance lines, has rarely been detected
in emission from galaxy halos other than Milky Way. Here we report four
additional detections of O VI emission gas in the halos of nearby edge-on
galaxies, NGC 4631 and NGC 891, using archival Far Ultraviolet Spectroscopic
Explorer data and an updated data pipeline. We find the most intense O VI
emission to be from fields forming a vertical line near the center of NGC 4631,
despite the close proximity to the disk of two other fields. The detected O VI
emission surface brightness are about 1.1 $times$ $10^{-18}$ to 3.9 $times$
$10^{-18}$ ergs s$^{-1}$ cm$^{-2}$ arcsec$^{-2}$. The spatial distribution of
the five 30″ $times$ 30″ O VI detection fields in NGC 4631 can be interpreted
as the existence of filamentary structures of more intense O VI emission
superimposed within a diffuse and faint O VI halo in star-forming galaxies.
Volume-filled O VI emission mapping is greatly needed to determine the
structure and prevalence of warm-hot gas and the role it plays in the cycling
of gas between the galaxy disk and the halo. Finally, we present the
sensitivity of future funded and proposed UV missions (LUVOIR-A, LUVOIR-B,
CETUS, and Aspera) to the detection of diffuse and faint O VI emission in
nearby galaxy halos.
A significant fraction of baryons in galaxies are in the form of diffuse gas
of the circumgalactic medium (CGM). One critical component of the multi-phases
of CGM, the so-called “coronal” warm-hot phase gas ($rm 10^{5}-10^{6}$ K)
traced by O VI 1031.93, 1037.62 r{A} resonance lines, has rarely been detected
in emission from galaxy halos other than Milky Way. Here we report four
additional detections of O VI emission gas in the halos of nearby edge-on
galaxies, NGC 4631 and NGC 891, using archival Far Ultraviolet Spectroscopic
Explorer data and an updated data pipeline. We find the most intense O VI
emission to be from fields forming a vertical line near the center of NGC 4631,
despite the close proximity to the disk of two other fields. The detected O VI
emission surface brightness are about 1.1 $times$ $10^{-18}$ to 3.9 $times$
$10^{-18}$ ergs s$^{-1}$ cm$^{-2}$ arcsec$^{-2}$. The spatial distribution of
the five 30″ $times$ 30″ O VI detection fields in NGC 4631 can be interpreted
as the existence of filamentary structures of more intense O VI emission
superimposed within a diffuse and faint O VI halo in star-forming galaxies.
Volume-filled O VI emission mapping is greatly needed to determine the
structure and prevalence of warm-hot gas and the role it plays in the cycling
of gas between the galaxy disk and the halo. Finally, we present the
sensitivity of future funded and proposed UV missions (LUVOIR-A, LUVOIR-B,
CETUS, and Aspera) to the detection of diffuse and faint O VI emission in
nearby galaxy halos.
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