Discovery of a Very Hot Phase of the Milky Way Circumgalactic Medium with Non-solar Abundance Ratios

Das, Sanskriti; Mathur, S.; Nicastro, F.; Krongold, Y.

doi:10.3847/2041-8213/ab3b09

Cited by 55 publications

(53 citation statements)

References 54 publications

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“…The electrons in this hot component would contribute significantly to the Galactic dispersion measure. The N(H) of the ≈ 10 7 K component along 1ES 1553+113 (l = 21.91 • , b = 43.96 • ) was found to be an order of magnitude higher than the N(H) of the ≈ 10 6 K component (Das et al 2019b). Therefore, the DM hot along this sightline would be higher than the current estimate by the same order.…”

Section: Assumptions and Caveatscontrasting

confidence: 53%

“…In fact, any existing method to calculate DM lacks this information. However, there are certain sightlines where a hotter ≈ 10 7 K component has been observed in absorption and/or emission (Henley & Shelton 2013;Nakashima et al 2018;Das et al 2019b,a, Gupta et al 2020. The electrons in this hot component would contribute significantly to the Galactic dispersion measure.…”

Section: Assumptions and Caveatsmentioning

confidence: 99%

“…Therefore, the DM hot along this sightline would be higher than the current estimate by the same order. Using equation 6 for the N(H) estimates by Das et al (2019b), we find that DM hot ≈ 128 cm −3 pc, while it is ≈ 12 cm −3 pc from the N(H) estimate of Gatuzz & Churazov (2018). In fact, if multiple temperature components are present along a sightline, using the ratio of N(O viii) and N(O vii) to estimate f O vii will be faulty as well, because it assumes that all of the O vii and O viii are coming from the same temperature component.…”

Section: Assumptions and Caveatsmentioning

confidence: 99%

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Empirical estimates of the Galactic halo contribution to the dispersion measures of extragalactic fast radio bursts using X-ray absorption

Das,

Mathur,

Gupta

et al. 2020

Preprint

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We provide an empirical list of the Galactic dispersion measure (DM Gal ) contribution to the extragalactic fast radio bursts along 72 sightlines. It is independent of any model of the Galaxy, i.e., we do not assume the density of the disk or the halo, spatial extent of the halo, baryonic mass content, or any such external constraints to measure DM Gal . We use 21-cm, UV, EUV and X-ray data to account for different phases, and find that DM Gal is dominated by the hot phase probed by X-rays. The median DM Gal = 64 +20 −23 cm −3 pc, with a 68% (90%) confidence interval of 33-172 (23-660) cm −3 pc. The DM Gal does not appear to follow any trend with the galactic longitude or latitude, and there is a large scatter around the values predicted by simple disk+halo models. Our measurements provide complementary (if not better) estimates of the Galactic DM compared to the previous studies. We provide a table and a code to retrieve DM Gal for any FRB localized in the sky.

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Section: Assumptions and Caveatscontrasting

confidence: 53%

Section: Assumptions and Caveatsmentioning

confidence: 99%

Section: Assumptions and Caveatsmentioning

confidence: 99%

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Empirical estimates of the Galactic halo contribution to the dispersion measures of extragalactic fast radio bursts using X-ray absorption

Das,

Mathur,

Gupta

et al. 2020

Preprint

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“…The first robust detection was in the sightline to 1ES1553 + 113 passing close to the North Polar Spur/Loop-I region of the Galactic bubbles [9,10]. Later, the similar temperature hot gas was detected toward three other sightlines passing close to and away from the Galactic bubbles [11].…”

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confidence: 89%

Paradigm shift in understanding the Galactic eROSITA Bubbles

Gupta

Mathur

Kingsbury

et al. 2022

Preprint

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The magnificent bubbles at the Galactic center provide a great channel to understand the effects of feedback on galaxy evolution. The newly discovered eROSITA bubbles show enhanced X-ray emission from the shells around bubbles. Previous works assumed that the X-ray emitting gas in the shells has a single temperature component and that they trace the shock-heated lower-temperature Galactic halo gas. Here we show that the thermal structure of the eROSITA bubble shells is more complex. Using Suzaku observations we find with high confidence that the X-ray emission from the shells is best described by a two-temperature thermal model, one near Galaxy's virial temperature at ~0.2 keV and the other at super-virial temperatures ranging between kT = 0.4-1.1 keV. Furthermore, we show that temperatures of the virial and super-virial components are similar in the shells and in the ambient medium, although the emission measures are significantly higher in the shells. We argue that the X-ray bright eROSITA bubble shells are the signature of compressed isothermal radiative shocks. The age of the bubbles is constrained to 70-130 Myr. This expansion timescale, as well as the observed non-solar Ne/O and Mg/O ratios, favor the stellar feedback models for the formation of the Galactic bubbles, settling a long-standing debate on the origin of the Galactic bubbles.

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“…Werk et al 2014;Miller & Bregman 2015;Prochaska et al 2017;Bregman et al 2018). The CGM is composed of a multiphase medium spanning a temperature range from the the cold gas (T ≈ 10 K) to the hot gas (T 10 6 K; e.g., Ménard et al 2010;Li & Wang 2013;Stocke et al 2013;Fang et al 2015;Peek et al 2015;Bogdán et al 2017;Burchett et al 2019;Das et al 2019;Lehner et al 2020;Kaaret et al 2020;Bregman et al 2021). This massive multi-phase CGM not only supplies the gaseous disk for continuous star formation, but also gathers the feedback materials from stellar evolution.…”

Section: Introductionmentioning

confidence: 99%

The Warm Gas in the MW: the Kinematical Model of C IV and its Connection with Si IV

Qu,

Lindley,

Bregman

2021

Preprint

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We compose a 265-sight line MW C IV line shape sample using the HST/COS archive, which is complementary to the existing Si IV samples. C IV has a higher ionization potential (47 − 64 eV) than Si IV (33 − 45 eV), so it also traces warm gas, which is roughly cospatial with Si IV. The spatial density distribution and kinematics of C IV is identical with Si IV within ≈ 2σ. C IV is more sensitive to the warm gas density distribution at large radii with a higher element abundance. Applying the kinematical model to the C IV sample, we find two possible solutions of the density distribution, which are distinguished by the relative extension along the disk mid-plane and the normal-line direction. Both two solutions can reproduce the existing sample, and suggest a warm gas disk mass of log M (M ) ≈ 8 and an upper limit of log M (M ) < 9.3 within 250 kpc, which is consistent with Si IV. There is a decrease of the C IV/Si IV column density ratio from the Galactic center (GC) to outskirts by 0.2 − 0.3 dex, which may suggest a phase transition or different ionization mechanisms for C IV and Si IV. Also, we find that the difference between C IV and Si IV is an excellent tracer of small-scale features, and we find a typical size of 5 • − 10 • for possible turbulence within individual clouds (≈ 1 kpc).

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Discovery of a Very Hot Phase of the Milky Way Circumgalactic Medium with Non-solar Abundance Ratios

Cited by 55 publications

References 54 publications

Empirical estimates of the Galactic halo contribution to the dispersion measures of extragalactic fast radio bursts using X-ray absorption

Empirical estimates of the Galactic halo contribution to the dispersion measures of extragalactic fast radio bursts using X-ray absorption

Paradigm shift in understanding the Galactic eROSITA Bubbles

The Warm Gas in the MW: the Kinematical Model of C IV and its Connection with Si IV

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