The composition of the interstellar medium towards the Lockman Hole

Kappes, Michael; Kerp, J.; Richter, Philipp

doi:10.1051/0004-6361:20030610

Cited by 8 publications

(9 citation statements)

References 32 publications

(46 reference statements)

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“…Weiß et al (1999) also found that IV21 contains two regions in different evolutionary states in the transition from atomic to molecular gas. There is also evidence that this cloud has an X-ray shadow against emission from the Galactic halo (Snowden et al 1994;Benjamin et al 1996;Kappes et al 2003), confirming that it is relatively local.…”

mentioning

confidence: 71%

A Low-Metallicity Molecular Cloud in the Lower Galactic Halo

Hernandez¹,

Wakker²,

Benjamin

et al. 2013

ApJ

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We find evidence for the impact of infalling, low-metallicity gas on the Galactic disk. This is based on FUV absorption line spectra, 21 cm emission line spectra, and far-infrared (FIR) mapping to estimate the abundance and physical properties of IV21 (IVC135+54-45), a galactic intermediate-velocity molecular cloud that lies ∼300 pc above the disk. The metallicity of IV21 was estimated using observations toward the subdwarf B star PG1144+615, located at a projected distance of 16 pc from the cloud's densest core, by measuring ion and H i column densities for comparison with known solar abundances. Despite the cloud's bright FIR emission and large column densities of molecular gas as traced by CO, we find that it has a sub-solar metallicity of log(Z/Z ) = −0.43 ± 0.12 dex. IV21 is thus the first known sub-solar metallicity cloud in the solar neighborhood. In contrast, most intermediate-velocity clouds (IVC) have near-solar metallicities and are believed to originate in the Galactic Fountain. The cloud's low metallicity is also atypical for Galactic molecular clouds, especially in light of the bright FIR emission which suggest a substantial dust content. The measured I 100 μm /N (H i) ratio is a factor of three below the average found in high latitude H i clouds within the solar neighborhood. We argue that IV21 represents the impact of an infalling, low-metallicity high-velocity cloud that is mixing with disk gas in the lower Galactic halo.

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confidence: 71%

A Low-Metallicity Molecular Cloud in the Lower Galactic Halo

Hernandez¹,

Wakker²,

Benjamin

et al. 2013

ApJ

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“…In addition, Kappes et al (2003) demonstrated that in the Lockman Hole region of the sky the halo is quite homogeneous. It is therefore probable that the Lockman observations were contaminated by solar protons or terrestrial CX emission.…”

Section: Non-shadowed Regionsmentioning

confidence: 99%

OVII and OVIII line emission in the diffuse soft X-ray background: heliospheric and galactic contributions

Koutroumpa

Acero

Lallement

et al. 2007

A&A

102

145

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Aims. We study the 0.57 keV (O VII triplet) and 0.65 keV (O VIII) diffuse emission generated by charge transfer collisions between solar wind (SW) oxygen ions and interstellar H and He neutral atoms in the inner Heliosphere. These lines which dominate the 0.3−1.0 keV energy interval are also produced by hot gas in the galactic halo (GH) and possibly the Local Interstellar Bubble (LB). Methods. We developed a time-dependent model of the Solar Wind Charge-Exchange (SWCX) X-ray emission, based on the localization of the Solar Wind Parker spiral at each instant. We include input SW conditions affecting three selected fields, as well as shadowing targets observed with XMM-Newton, Chandra and Suzaku satellites and calculate X-ray emission in the oxygen lines O VII and O VIII in order to determine the SWCX contamination and the residual emission to attribute to the galactic soft X-ray background. We obtain ground level intensities and/or simulated lightcurves for each target and compare to X-ray data from the three instruments mentioned. Results. The local 3/4 keV emission (due essentially to O VII and O VIII) detected in front of shadowing clouds is found to be entirely explained by the CX heliospheric emission. No emission from the LB is needed at these energies. The observed and modeled range of the foreground oxygen emission is 0.3−4.6 LU (Line Units = photons cm −2 s −1 sr −1 ) for OVII and 0.02−2.1 LU for OVIII depending on directions and conditions. Using the model predictions we subtract the heliospheric contribution to the measured emission and derive the halo contribution. We also correct for an error in the preliminary analysis of the Hubble Deep Field North (HDFN). We find intensities of 4.9

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“…The equivalent kinetic energy of these eigenstates averaged over the electron and proton component is most simply calculated from 00 () 4 Ek   . The Milky Way exhibits a range of x-ray energies but the best estimates of the diffuse halo gas temperature are 6 1.3 1.5 10 K  (Kappes et al, 2003). If the hypothesis of energy transfer from dark to visible states is correct, one might expect to see, over a range of different halos, a linear correlation between two quantities 00 M R and the x-ray temperature, both of which should be measurable, the first by lensing and the second by x-ray satellites.…”

Section: Observations and Predictionsmentioning

confidence: 99%

Gravitational Quantisation and Dark Matter

Ernest¹

2012

Advances in Quantum Theory

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The composition of the interstellar medium towards the Lockman Hole

Cited by 8 publications

References 32 publications

A Low-Metallicity Molecular Cloud in the Lower Galactic Halo

A Low-Metallicity Molecular Cloud in the Lower Galactic Halo

OVII and OVIII line emission in the diffuse soft X-ray background: heliospheric and galactic contributions

Gravitational Quantisation and Dark Matter

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