Intergalactic-Absorption Confounding Circumgalactic Observations
Itai Bromberg, Kartick C.Sarkar, Orly Gnat, and Yuval Brinboim

TL;DR
This paper proposes that a significant portion of warm-ion absorption observed around galaxies may originate from the intergalactic medium rather than the circumgalactic medium, impacting the interpretation of such observations.
Contribution
It introduces a simple spherical collapse model to quantify IGM contributions to warm-ion columns, challenging previous assumptions that mainly attributed these to the CGM.
Findings
IGM can produce over 75% of O VI columns in massive halos.
The model reproduces observed O VI trends with impact parameter and halo mass.
IGM envelopes may dominate warm-ion absorption, complicating CGM analysis.
Abstract
The origin of warm ions in the circum-galactic medium (CGM) surrounding massive galaxies remains a mystery. In this paper, we argue that a significant fraction of the observed warm-ion columns may arise in the intergalactic medium (IGM) surrounding galactic halos. We use a simple spherical collapse model of the dark matter (DM) halos and their baryonic content to compute the evolving ion fractions within and outside virial halos. We show that the photoionized IGM may produce a thick blanket of warm ions around the CGM, thereby contaminating CGM observations. We find that the IGM contributes of the total \ion{O}{6} column densities in halos with virial masses exceeding a few times , and that it may dominate the \ion{O}{6} absorption even for lower mass-halos, depending on the impact parameter. We compare our results with observations and find that our simplified…
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Taxonomy
TopicsRadio Astronomy Observations and Technology · Astronomical Observations and Instrumentation · Geophysics and Gravity Measurements
