On the Hot Gas Content of the Milky Way Halo

Fang, Taotao; Bullock, James S.; Boylan-Kolchin, Michael

doi:10.1088/0004-637x/762/1/20

Cited by 132 publications

(156 citation statements)

References 71 publications

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“…Thus, the halo has a global baryon fraction of 0.16, consistent with the cosmic value of f b = Ω b /Ωm. Some of the recent observations have revealed that the baryon fraction can be ∼ 0.1 for massive spirals (Bogdan et al 2013), and in our MW, this fraction can be ∼ 0.16 for a gas with polytropic index γ = 5/3 in hydrostatic equilibrium (Fang et al 2013;Gatto et al 2013). Though here we assume f b = 0.16, we have also checked the effect of f b on the mass loading factor at virial radius (see §4.3).…”

Section: Setting the Initial Density Distributionsupporting

confidence: 55%

Long way to go: how outflows from large galaxies propagate through the hot halo gas

Sarkar

Nath

Sharma

et al. 2015

Monthly Notices of the Royal Astronomical Society

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Using hydrodynamic simulations, we study the mass loss due to supernova-driven outflows from Milky Way type disk galaxies, paying particular attention to the effect of the extended hot halo gas. We find that the total mass loss at inner radii scales roughly linearly with total mass of stars formed, and that the mass loading factor at the virial radius can be several times its value at inner radii because of the swept up hot halo gas. The temperature distribution of the outflowing material in the inner region (∼10 kpc) is bimodal in nature, peaking at 10 5 K and 10 6.5 K, responsible for optical and X-ray emission, respectively. The contribution of cold/warm gas with temperature 10 5.5 K to the outflow rate within 10 kpc is ≈ 0.3-0.5. The warm mass loading factor, η 3e5 (T 3 × 10 5 K) is related to the mass loading factor at the virial radius (η v ) as η v ≈ 25 η 3e5 SFR/M ⊙ yr −1 −0.15 for a baryon fraction of 0.1 and a starburst period of 50 Myr. We also discuss the effect of multiple bursts that are separated by both short and long periods. The outflow speed at the virial radius is close to the sound speed in the hot halo, 200 km s −1 . We identify two 'sequences' of outflowing cold gas at small scales: a fast (≈ 500 km s −1 ) sequence, driven by the unshocked free-wind; and a slow sequence (≈ ±100 km s −1 ) at the conical interface of the superwind and the hot halo.

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Section: Setting the Initial Density Distributionsupporting

confidence: 55%

Long way to go: how outflows from large galaxies propagate through the hot halo gas

Sarkar

Nath

Sharma

et al. 2015

Monthly Notices of the Royal Astronomical Society

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“…However, larger samples of absorption lines (∼40 sight lines; Bregman & LloydDavies 2007;Gupta et al 2012;Fang et al 2015) and the all-sky emission-line intensities (≈1000 sight lines Henley & Shelton 2012;Miller & Bregman 2013) favor a spherical model. Similar analyses on independent observables that also probe the hot gas, such as the pulsar dispersion measure toward the Large Magellanic Cloud and the ram-pressure stripping of Milky Way satellites favor an extended halo (Fang et al 2013;Salem et al 2015). Finally, a recent analysis of both Galactic and extragalactic sightlines for L * galaxies finds that the O VII traces hot gas (Faerman et al 2016).…”

Section: Halo and Disk Modelsmentioning

confidence: 95%

The Rotation of the Hot Gas Around the Milky Way

Hodges-Kluck

Miller

Bregman

2016

ApJ

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The hot gaseous halos of galaxies likely contain a large amount of mass and are an integral part of galaxy formation and evolution. The Milky Way has a2 10 6 K halo that is detected in emission and by absorption in the O VII resonance line against bright background active galactic nuclei (AGNs), and for which the best current model is an extended spherical distribution. Using XMM-Newton Reflection Grating Spectrometer data, we measure the Doppler shifts of the O VII absorption-line centroids toward an ensemble of AGNs. These Doppler shifts constrain the dynamics of the hot halo, ruling out a stationary halo at about s 3 and a co-rotating halo at s 2 , and leading to a best-fit rotational velocity of =  f v 183 41 km s −1 for an extended halo model. These results suggest that the hot gas rotates and that it contains an amount of angular momentum comparable to that in the stellar disk. We examined the possibility of a model with a kinematically distinct disk and spherical halo. To be consistent with the emission-line X-ray data, the disk must contribute less than 10% of the column density, implying that the Doppler shifts probe motion in the extended hot halo.

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“…First, the baryon fraction that can collapse into low mass halos is strongly reduced (Mo & Mao 2002;van den Bosch, Abel & Hernquist 2003;Oh & Benson 2003;McCarthy et al 2004;Scannapieco & Oh 2004;Lu & Mo 2007). Second, when the entropy of the pre-collapsed gas is higher than would be generated by accretion shocks, the halo gas is expected to develop an extended density distribution (Mo & Miralda-Escude 1996;Mo & Mao 2002;Maller & Bullock 2004;Kaufmann et al 2009;Fang, Bullock & Boylan-Kolchin 2013), thereby affecting where and when halo gas cools to fuel the central disk. Using a semi-analytic model built upon simulated halo accretion histories, we examine in detail the disk size evolution, mass assembly and star formation histories of central galaxies hosted by halos with masses Mvir < 10 12 M⊙ at the present time in the preheating scenario.…”

Section: Introductionmentioning

confidence: 99%

Formation of disc galaxies in preheated media: a preventative feedback model

Lu¹,

Mo²

2014

Monthly Notices of the Royal Astronomical Society

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We introduce a semi-analytic galaxy formation model implementing a self-consistent treatment for the hot halo gas configuration and the assembly of central disks. Using the model, we explore a preventative feedback model, in which the circum-halo medium is assumed to be preheated up to a certain entropy level by early starbursts or other processes, and compare it with an ejective feedback model, in which baryons are first accreted into dark matter halos and subsequently ejected out by feedback. The model demonstrates that when the medium is preheated to an entropy comparable to the halo virial entropy the baryon accretion can be largely reduced and delayed. In addition, the preheated medium can establish an extended low density gaseous halo when it accretes into the dark matter halos, and result in a specific angular momentum of the cooling gas large enough to form central disks as extended as those observed. Combined with simulated halo assembly histories, the preventative feedback model can reproduce remarkably well a number of observational scaling relations. These include the cold baryon (stellar plus cold gas) mass fraction-halo mass relations, star formation histories, disk size-stellar mass relation and its evolution, and the number density of low-mass galaxies as a function of redshift. In contrast, the conventional ejective feedback model fails to reproduce these observational trends. Using the model, we demonstrate that the properties of disk galaxies are closely tied to the thermal state of hot halo gas and even possibly the circum-halo medium, which suggests that observational data for the disk properties and circum-galactic hot/warm medium may jointly provide interesting constraints for galaxy formation models.

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On the Hot Gas Content of the Milky Way Halo

Cited by 132 publications

References 71 publications

Long way to go: how outflows from large galaxies propagate through the hot halo gas

Long way to go: how outflows from large galaxies propagate through the hot halo gas

The Rotation of the Hot Gas Around the Milky Way

Formation of disc galaxies in preheated media: a preventative feedback model

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