The H<scp>i</scp> Distribution of the Milky Way

Kalberla, P. M. W.

doi:10.1146/annurev-astro-082708-101823

Cited by 415 publications

(403 citation statements)

References 110 publications

(171 reference statements)

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“…If, for the sake of argument, we approximate QH I ∼ LUV/h ∼ 6 × 10 56 sec −1 , our model (Curran & Whiting 2012) yields a scale-length of R = 3.05 kpc, cf. 3.15 kpc for the Milky Way (Kalberla & Kerp 2009). That is, this ionising photon rate is just sufficient to ionise all of the gas in a large spiral, which is consistent with the results of Curran & Whiting.…”

Section: Observational Resultssupporting

confidence: 89%

Atomic and molecular absorption in redshifted radio sources

Curran

Whiting

Allison

et al. 2017

Monthly Notices of the Royal Astronomical Society

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We report on a survey for associated H I 21-cm and OH 18-cm absorption with the Giant Metrewave Radio Telescope at redshifts z ≈ 0.2 − 0.4. Although the low redshift selection ensures that our targets are below the critical ultra-violet luminosity (L UV ∼ 10 23 W Hz −1 ), which is hypothesised to ionise all of the neutral gas in the host galaxy, we do not obtain any detections in the six sources searched. Analysing these in context of the previous surveys, in addition to the anti-correlation with the ultra-violet luminosity (ionising photon rate), we find a correlation between the strength of the absorption and the blue -near-infrared colour, as well as the radio-band turnover frequency. We believe that these are due to the photo-ionisation of the neutral gas, an obscured sight-line being more conducive to the presence of cold gas and the compact radio emission being better intercepted by the absorbing gas, maximising the flux coverage, respectively. Regarding the photo-ionisation, the compilation of the previous surveys increases the significance of the critical ionising photon rate, above which all of the gas in the host galaxy is hypothesised to be ionised (Q H I ≈ 3 × 10 56 sec −1 ), to > 5σ. This reaffirms that this is an ubiquitous effect, which has profound implications for the detection of neutral gas in these objects with the Square Kilometre Array.

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Section: Observational Resultssupporting

confidence: 89%

Atomic and molecular absorption in redshifted radio sources

Curran

Whiting

Allison

et al. 2017

Monthly Notices of the Royal Astronomical Society

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“…4) are consistent with the hypothesis that LA2 and LA3 filaments probably passed through a thinner volume density portion at longer galactocentric distances than LA1.3. Using the Kalberla & Kerp (2009) model, we suggest for LA2 and LA3 a galactocentric distance of ≥40 kpc where a density n ≤ 10 −4 cm −3 is expected.…”

Section: Velocity Structure Of La1mentioning

confidence: 87%

“…In the case of an exponential radial density distribution of the Galactic disk (Kalberla & Kerp 2009), the strength of the interaction depends critically on the radial distance from the Galactic center. Our findings (see Fig.…”

Section: Velocity Structure Of La1mentioning

confidence: 99%

The four leading arms of the Magellanic Cloud system

Venzmer¹,

Kerp²,

Kalberla³

2012

A&A

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Context. The Magellanic Cloud system (MCS) interacts via tidal and drag forces with the Milky Way galaxy. Aims. Using the Parkes Galactic All-Sky Survey (GASS) of atomic hydrogen we explore the role of drag on the evolution of the so-called Leading Arm (LA).Methods. We present a new image recognition algorithm that allows us to differentiate features within a 3D data cube (longitude, latitude, radial velocity) and to parameterize individual coherent structures. We compiled an Hi object catalog of LA objects within an area of 70 • × 85 • (1.6 sr) of the LA region. This catalog comprises information of location, column density, line width, shape and asymmetries of the individual LA objects above the 4-σ threshold of ΔT b 200 mK.Results. We present evidence of a fourth arm segment (LA4). For all LA objects we find an inverse correlation of velocities v GSR in Galactic Standard of Rest frame with Magellanic longitude. High-mass objects tend to have higher radial velocities than low-mass ones. About 1/4 of all LA objects can be characterized as head-tail (HT) structures. Conclusions. Using image recognition with objective criteria, it is feasible to isolate most of LA emission from the diffuse Milky Way Hi gas. Some blended gas components (we estimate 5%) escape detection, but we find a total gas content of the LA that is about 50% higher than previously assumed. These methods allow the deceleration of the LA clouds to be traced towards the Milky Way disk by drag forces. The derived velocity gradient strongly supports the assumption that the whole LA originates entirely in the Large Magellanic Cloud (LMC). LA4 is observed opposite to LA1, and we propose that both arms are related, spanning about 52 kpc in space. HT structures trace drag forces even at tens of kpc altitudes above the Milky Way disk.

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“…In particular, we have subtracted a template map including all of the sources in the region contained within the Fermi Second Source Catalog [24] (adopting central values for the intensity and location of each source, as reported in the catalog), with the exception of the bright central source, which cannot be easily disentangled from dark matter annihilation products in the case of a strongly cusped or contracted halo profile. To account for emission from the disk, we subtract a template with a morphology derived from the line-of-sight gas densities [25,26] as a function of galactic latitude (this template is only very mildly dependent on galactic longitude in the region of the sky being studied here). For details, see Ref.…”

Section: Analysis Proceduresmentioning

confidence: 99%

Stringent constraints on the dark matter annihilation cross section from the region of the Galactic Center

Hooper

Kelso

Queiroz

2013

Astroparticle Physics

157

197

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For any realistic halo profile, the Galactic Center is predicted to be the brightest source of gammarays from dark matter annihilations. Due in large part to uncertainties associated with the dark matter distribution and astrophysical backgrounds, however, the most commonly applied constraints on the dark matter annihilation cross section have been derived from other regions, such as dwarf spheroidal galaxies. In this article, we study Fermi Gamma-Ray Space Telescope data from the direction of the inner Galaxy and derive stringent upper limits on the dark matter's annihilation cross section. Even for the very conservative case of a dark matter distribution with a significant (∼kpc) constant-density core, normalized to the minimum density needed to accommodate rotation curve and microlensing measurements, we find that the Galactic Center constraint is approximately as stringent as those derived from dwarf galaxies (which were derived under the assumption of an NFW distribution). For NFW or Einasto profiles (again, normalized to the minimum allowed density), the Galactic Center constraints are typically stronger than those from dwarfs.

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The Hi Distribution of the Milky Way

Cited by 415 publications

References 110 publications

Atomic and molecular absorption in redshifted radio sources

Atomic and molecular absorption in redshifted radio sources

The four leading arms of the Magellanic Cloud system

Stringent constraints on the dark matter annihilation cross section from the region of the Galactic Center

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