Probing the Hot Circumgalactic Medium with Broad O vi and X-Rays

Abstract

Most of the baryonic mass in the circumgalactic medium (CGM) of a spiral galaxy is believed to be warm-hot, with temperature around 106 K. The narrow O vi absorption lines probe a somewhat cooler component at , but broad O vi absorbers have the potential to probe the hotter CGM. Here we present 376 ks Chandra LETG observations of a carefully selected galaxy in which the presence of broad O vi together with the non-detection of Lyα was indicative of hot gas. The strongest line expected to be present at ≈106 K is O vii λ21.602. There is a hint of an absorption line at the redshifted wavelength, but the line is not detected with better than 2σ significance. A physical model, taking into account strengths of several other lines, provides better constraints. Our best-fit absorber model has and . These parameters are consistent with the hot plasma model based on UV observations; other O vi models of cooler gas phases are ruled out at better than 99% confidence. Thus we have suggestive, but not conclusive evidence for the broad O vi absorber probing the hot gas from the shallow observations of this pilot program. About 800 ks of XMM-Newton observations will detect the expected absorption lines of O vii and O viii unequivocally. Future missions like XRISM, Arcus, and Athena will revolutionize the CGM science.

Gas kinetics of galactic disk explains rotation curves of S-type galaxies without a need for Dark Matter.

“…If we assume that dark matter does not exist, then it becomes clear that in the outer region a certain force is acting on the gas, significantly exceeding the force of gravity caused by the baryonic matter of the galaxy. For this reason, the disk can be divided into two parts: the inner region (R < R 0 ), where the usual gravitational force prevails, and the outer region (R > R 0 ), where the gas dynamics is mainly due to the collisional properties of the gas and is described by the kinetic equation (3). Obviously, the inner part consists mainly of stars (described as collisionless gas) and therefore the influence of gas kinetics here will be insignificant.…”

“…To avoid constraint (6) and at the same time take into account collisions (as it was done in the hydrodynamic approach), I start with the same kinetic equation (3). To obtain eq.…”

“…Authors argue that the missing baryons reside in large-scale filaments in the form of warm-hot intergalactic medium observed in OVII and OVI lines (see also Refs. [2] and [3]). It should also be added here that neglecting the diffuse lensed signal, when processing lensed images, leads to a significant overestimation of the half-light radius and, as a consequence, to an overestimation of the lensing mass value [4] .…”

Кинетика Газа В Галактических Дисках Объясняет Кривые Вращения Спиральных Галактик Без Привлечения Тёмной Материи.

“…Авторы утверждают, что недостающая барионная материя находится в крупномасштабных нитевидных структурах образованныъ тёплым и горячим межгалактическим газом, наблюдаемым в линиях ионизованного кислорода OVII и OVI (см. [2] и [3]). С другой стороны, следует упомянуть об отмеченной в [4] необходимости корректно учитывать диффузный линзированный сигнал, пренебрежение вкладом от которого приводит к переоценке величины линзирующей массы.…”

The longstanding galaxy missing-baryon problem is solved by a large reservoir of hot gas permeating their halos

“…[2]). Observationally, the presence of this hot phase is currently only hinted through Sunyaev-Zeldovich [21] and low-resolution X-ray [22] measurements of the surroundings of local L* galaxy or pioneering X-ray absorption [23] studies (see below), and more ubiquitously through absorption by moderately-ionized ions of oxygen (e.g. [13,[16][17][18]) and neon (e.g.…”