The Hot, Accreted Halo of NGC 891

Hodges-Kluck, Edmund; Bregman, Joel N.; Li, Jiangtao

doi:10.3847/1538-4357/aae38a

Cited by 45 publications

(52 citation statements)

References 117 publications

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“…This conclusion looks consistent with observations of extended hot (X-ray) haloes around edge-on galaxies with a relatively modest SF rate. For instance, observations on XMM-Newton and Chandra of an edge-on galaxy NGC 891 reveal presence of hot (T ∼ 0.3 keV) gas extending up to z ∼ 10 kpc, which is comparable to the galaxy radius (Hodges-Kluck et al 2018).…”

Section: Resultsmentioning

confidence: 99%

Launching of hot gas outflow by disc-wide supernova explosions

Vasiliev

Shchekinov

Nath

2019

Monthly Notices of the Royal Astronomical Society

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Galactic gas outflows are driven by stellar feedback with dominant contribution from supernovae (SN) explosions. The question of whether the energy deposited by SNe initiates a large scale outflow or gas circulation on smaller scales -between discs and intermediate haloes, depends on SN rate and their distribution in space and time. We consider here gas circulation by disc-wide unclustered SNe with galactic star formation rate in the range from ≃ 6 × 10 −4 to ≃ 6 × 10 −2 M ⊙ yr −1 kpc −2 , corresponding to mid-to-high star formation observed in galaxies. We show that such disc-wide SN explosion regime can form circulation of warm (T ∼ 10 4 K) and cold (T < 10 3 K) phases within a few gas scale heights, and elevation of hot (T > 10 5 K) gas at higher (z > 1 kpc) heights. We found that the threshold energy input rate for hot gas outflows with disc-wide supernovae explosions is estimated to be of the order ∼ 4 × 10 −4 erg s −1 cm −2 . We discuss the observational manifestations of such phenomena in optical and X-ray bands. In particular, we found that for face-on galaxies with SF (Σ SF > 0.02 M ⊙ yr −1 kpc −2 ), the line profiles of ions typical for warm gas show a double-peak shape, corresponding to out-of-plane outflows. In the X-ray bands, galaxies with high SF rates (Σ SF > 0.006 M ⊙ yr −1 kpc −2 ) can be bright, with a smooth surface brightness in low-energy bands (0.1-0.3 keV) and patchy at higher energies (1.6-8.3 keV).

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Section: Resultsmentioning

confidence: 99%

Launching of hot gas outflow by disc-wide supernova explosions

Vasiliev

Shchekinov

Nath

2019

Monthly Notices of the Royal Astronomical Society

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“…Further, we are not injecting any magnetic fields even though supernovae ejecta is expected to be magnetised. Therefore, our simulation is inadequate for addressing radio emission from the halo at larger scale heights as observed by Hodges-Kluck et. al.…”

Section: Discussionmentioning

confidence: 98%

Radio haloes of star-forming galaxies

Vijayan

Nath

Sharma

et al. 2019

Monthly Notices of the Royal Astronomical Society

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We study the synchrotron radio emission from extra-planar regions of star forming galaxies. We use ideal magneto-hydrodynamical (MHD) simulations of a rotating Milky Way-type disk galaxy with distributed star formation sites for three star formation rates (SFRs) (0.3, 3, 30 M yr −1 ). From our simulations, we see emergence of galactic-scale magnetised outflows, carrying gas from the disk. We compare the morphology of the outflowing gas with hydrodynamic (HD) simulations. We look at the spatial distribution of magnetic field in the outflows. Assuming that a certain fraction of gas energy density is converted into cosmic ray energy density, and using information about the magnetic field, we obtain synchrotron emissivity throughout the simulation domain. We generate the surface brightness maps at a frequency of 1.4 GHz. The outflows are more extended in the vertical direction than radial and hence have an oblate shape. We further find that the matter right behind the outer shock, shines brighter in these maps than that above or below. To understand whether this feature can be observed, we produce vertical intensity profiles. We convolve the vertical intensity profile with the typical beam sizes of radio telescopes, for a galaxy located at 10 Mpc (similar to NGC 891) in order to estimate the radio scale height to compare with observations. We find that for our SFRs this feature will lie below the RMS noise limit of instruments. The radio scale height is found to be ∼ 300 − 1200 pc , depending on the resolution of the telescope. We relate the advection speed of the outer shock with the surface density of star formation as v adv ∝ Σ 0.3 SFR , which is consistent with earlier observations and analytical estimates.

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“…Abundances are measured for eight elements, showing a typical depletion pattern seen in the MW warm diffuse gas. The volatile elements (C, N, S) show a metallicity of [X/H] = −0.3 ± 0.3, which suggests that the highmetallicity disk-originating gas is mixed with the virialized hot halo (Z ≈ 0.14Z ⊙ ) seen in the X-rays (Hodges-Kluck et al 2018). This leads to a more massive warm gas disk than the H I disk from 21 cm emission, and along this sightline; the H/H I ratio is about 5 ± 1.…”

Section: Discussionmentioning

confidence: 99%

“…Then, the 10 4 K UV absorbing gas would be understood as a mixture of the disk gas and the hot X-ray emitting medium. Interaction and mixing between the two components has been proposed (Fraternali 2017), although it is not clear whether this is a viable explanation in detail, as the hot halo mass (≈ 2.4 × 10 8 M ⊙ ; Hodges-Kluck & Bregman 2013;Hodges-Kluck et al 2018) is about order of magnitude less than the neutral and warm ionized gas for scale height < 10 kpc.…”

Section: The Major System In Lqac 035+042 003mentioning

confidence: 99%

HST/COS Observations of the Warm Ionized Gaseous Halo of NGC 891

Bregman

Hodges-Kluck

2019

ApJ

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The metallicity of galactic gaseous halos provides insights into accretion and feedback of galaxies. The nearby edge-on galaxy NGC 891 has a multi-component gaseous halo and a background AGN (LQAC 035+042 003) projected 5 kpc above the disk near the minor axis. Against the UV continuum of this AGN, we detect lines from 13 ions associated with NGC 891 in new HST/COS spectra. Most of the absorption is from the warm ionized gas with log T = 4.22 ± 0.04, log n H = −1.26 ± 0.51, and log N H = 20.81 ± 0.20. The metallicity of volatile elements (i.e., C, N, and S) is about half solar ([X/H] ≈ −0.3 ± 0.3), while Mg, Fe, and Ni show lower metallicities of [X/H] ≈ −0.9. The absorption system shows the depletion pattern seen for warm Galactic diffuse clouds, which is consistent with a mixture of ejected solar metallicity disk gases and the hot X-ray emitting halo (Z = 0.1 − 0.2Z ⊙ ). The warm ionized gases are about 5 times more massive than the cold H I emitting gases around the galactic center, which might lead to accretion with a mean rate of 10 2 M ⊙ yr −1 for a period of time. We also detect low metallicity (≈ 0.1 Z ⊙ ) gases toward LQAC 035+042 003 at 110 km s −1 (a high velocity cloud) and toward another sight line (3C 66A; 108 kpc projected from NGC 891) at 30 km s −1 . This low metallicity material could be the cold mode accretion from IGM or the tidal disruption of satellites in the NGC 891 halo.

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The Hot, Accreted Halo of NGC 891

Cited by 45 publications

References 117 publications

Launching of hot gas outflow by disc-wide supernova explosions

Launching of hot gas outflow by disc-wide supernova explosions

Radio haloes of star-forming galaxies

HST/COS Observations of the Warm Ionized Gaseous Halo of NGC 891

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