Neutral Gas Accretion onto Nearby Galaxies

Lockman, Felix J.

doi:10.1007/978-3-319-52512-9_3

Cited by 4 publications

(2 citation statements)

References 78 publications

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“…Analogous populations of cold gas clouds are observed in M31 and other nearby spiral galaxies (e.g. Thilker et al 2004;Westmeier et al 2008;Lockman 2017).…”

Section: Introductionsupporting

confidence: 61%

The effect of rotation on the thermal instability of stratified galactic atmospheres – II. The formation of high-velocity clouds

Sormani

Sobacchi

2019

Monthly Notices of the Royal Astronomical Society

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Whether High Velocity Clouds (HVCs) can form by condensation of the hot (T ∼ 10 6 K) Galactic corona as a consequence of thermal instabilities has been controversial. Here we re-examine this problem and we suggest that rotation of the corona might be a missing key ingredient. We do this by studying the evolution of the models of rotating galactic coronae presented in Sormani et al. (2018) under the presence of cooling and thermal conduction. We combine a linear stability analysis with the results of local and global hydrodynamical simulations. We find that condensations are likely to occur in regions where the corona has substantial rotational support. Under reasonably general assumptions on the rotation profile of the corona, the locations where condensations are expected are in remarkable agreement with the observed location of the major non-magellanic HVCs complexes in our Galaxy (namely, at distances 15 kpc from the Sun and within 30 • from the disc plane). We conclude that HVCs can form by thermal instabilities provided that (i) the corona is rotating substantially in the inner (R 50 kpc) parts, as suggested by current observational data and predicted by cosmological simulations of galaxy formation; (ii) close to the disc the corona is well-represented by a nearly-equilibrium stratified rotating structure (as opposed to a fast cooling flow). Our results also suggest that a better understanding of the disc-halo interface, including supernova feedback, is critical to understand the origin of HVCs.

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“…Analogous populations of cold gas clouds are observed in M31 and other nearby spiral galaxies (e.g. Thilker et al 2004;Westmeier et al 2008;Lockman 2017).…”

Section: Introductionsupporting

confidence: 61%

The effect of rotation on the thermal instability of stratified galactic atmospheres – II. The formation of high-velocity clouds

Sormani

Sobacchi

2019

Monthly Notices of the Royal Astronomical Society

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“…We find a total atomic mass of 1.3 ± 0.5 × 10 7 M in the velocity-integrated regions shown in Figure 18, which accounts for about 20% of the total HVC and disk-halo mass in M33 (Lockman 2017), and ∼ 1% of the atomic mass of the main and lagging disks. This mass is a factor of ∼ 3 less than the estimated HVC mass in the Milky Way (Putman et al 2012).…”

Section: Discrete H I Cloudsmentioning

confidence: 79%

Kinematics of the atomic ISM in M33 on 80 pc scales

Koch

Rosolowsky

Lockman³

et al. 2018

Monthly Notices of the Royal Astronomical Society

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We present new L-band (1-2 GHz) observations of the nearby spiral galaxy M33 with 80 pc resolution obtained with the Karl G. Jansky Very Large Array. The H I observations, combined with H I measurements from the Green Bank Telescope, improve the spectral resolution and sensitivity (2.8 K rms noise in a 0.2 km s −1 channel) compared to previous observations. We find individual profiles are usually non-Gaussian, harbouring line wings, multiple components, and asymmetries. Given this spectral complexity, we quantify the motions in the atomic ISM through moment analysis of the spectra and fits to aligned, stacked profiles. The measured value of the H I line width depends strongly on the method used, with the velocity stacked profiles aligned to the peak velocity giving the minimum value of σ = 7 km s −1 and all other methods giving higher values (σ ∼ 10 km s −1 ). All measurements of the line width show a shallow radial trend, with σ decreasing by ∼ 2 km s −1 from R gal = 0 to R gal = 8 kpc. We consider a number of energy sources that might maintain the line width against turbulent dissipation, but no single source is adequate. We find excess emission relative to a Gaussian in the stacked profile line wings, ranging from 9% to 26% depending on how the spectra are aligned. By splitting the line wings into symmetric and asymmetric components, we find that the lagging rotational disk accounts for one-third of the line wing flux. We also find emission far from the rotation-axis of the galaxy in multiple discrete H I clouds, including a filament with a projected length of ∼ 8 kpc.

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Gas accretion on to galaxies and Kelvin–Helmholtz turbulence

Goldman

Fleck

2023

Monthly Notices of the Royal Astronomical Society

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Continued star formation over the lifetime of a galaxy suggests that gas is steadily flowing in from the circumgalactic medium. Also, cosmological simulations of large-scale structure formation imply that gas is accreted onto galaxies from the halo inside which they formed. Direct observations are difficult, but in recent years observational indications of gas inflows from a circumgalactic medium were obtained. Here we suggest an indirect observational probe: looking for large-scale (exceeding few kpc) turbulence caused by the accretion. As a specific example we consider an accretion flow coplanar with the galaxy disk, and argue that Kelvin-Helmholtz turbulence will be generated. We employ a semi-analytic model of turbulence and derive the expected turbulence power spectrum. The latter turns out to be of a distinctive shape that can be compared with observational power spectra. As an illustrative example we use parameters of the Milky Way galaxy.

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Neutral Gas Accretion onto Nearby Galaxies

Cited by 4 publications

References 78 publications

The effect of rotation on the thermal instability of stratified galactic atmospheres – II. The formation of high-velocity clouds

The effect of rotation on the thermal instability of stratified galactic atmospheres – II. The formation of high-velocity clouds

Kinematics of the atomic ISM in M33 on 80 pc scales

Gas accretion on to galaxies and Kelvin–Helmholtz turbulence

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