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Gravitational Lensing and the search for Dark Matter
Can someone point me to a good explanation of this method ? I.e. by
analysing lensing effects in a galaxy cluster, it is possible to map the distribution of DM within the cluster, and presumably also to estimate the amount of DM present in the cluster. Thanks, AM [Mod. note: there are many reviews of this topic that you can find with a search engine or by searching ADS. For a recent one try http://arxiv.org/abs/1303.3274 -- mjh] |
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Gravitational Lensing and the search for Dark Matter
In article , AM
writes: Can someone point me to a good explanation of this method ? I.e. by analysing lensing effects in a galaxy cluster, it is possible to map the distribution of DM within the cluster, and presumably also to estimate the amount of DM present in the cluster. Thanks, AM [Mod. note: there are many reviews of this topic that you can find with a search engine or by searching ADS. For a recent one try http://arxiv.org/abs/1303.3274 -- mjh] Apart from Martin's suggestion, you might want to search for "weak lensing", in order to filter out other gravitational-lens stuff which is not related to what you are looking for. (In gravitational lensing, "weak lensing" generally refers to (a) resolved (i.e. not point) sources (b) which are not multiply imaged. So, usually, distorted and magnified images of background galaxies as a result of the gravitational field of the foreground lens (galaxy cluster). |
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Gravitational Lensing and the search for Dark Matter
In article , AM
asked: Can someone point me to a good explanation of this method ? I.e. by analysing lensing effects in a galaxy cluster, it is possible to map the distribution of DM within the cluster, and presumably also to estimate the amount of DM present in the cluster. A nice black-marks-on-dead-trees review is Peter Schneider, Christopher S. Kochanek, and Joachim Wambsganss, "Gravitational Lensing: Strong, Weak and Micro" (Saas-Fee Advanced Course 33) Springer-Verlag, 2006, ISBN 978-3-540-30309-1 -- -- "Jonathan Thornburg [remove -animal to reply]" Dept of Astronomy & IUCSS, Indiana University, Bloomington, Indiana, USA "There was of course no way of knowing whether you were being watched at any given moment. How often, or on what system, the Thought Police plugged in on any individual wire was guesswork. It was even conceivable that they watched everybody all the time." -- George Orwell, "1984" |
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Gravitational Lensing and the search for Dark Matter
In article , "Jonathan
Thornburg [remove -animal to reply]" writes: Can someone point me to a good explanation of this method ? I.e. by analysing lensing effects in a galaxy cluster, it is possible to map the distribution of DM within the cluster, and presumably also to estimate the amount of DM present in the cluster. A nice black-marks-on-dead-trees review is Peter Schneider, Christopher S. Kochanek, and Joachim Wambsganss, "Gravitational Lensing: Strong, Weak and Micro" (Saas-Fee Advanced Course 33) Springer-Verlag, 2006, ISBN 978-3-540-30309-1 This covers essentially all of gravitational lensing, though, not just what the OP was looking for. Still, no reason not to read it. |
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Gravitational Lensing and the search for Dark Matter
On 4/29/14, 3:20 PM, AM wrote:
Can someone point me to a good explanation of this method ? I.e. by analysing lensing effects in a galaxy cluster, it is possible to map the distribution of DM within the cluster, and presumably also to estimate the amount of DM present in the cluster. Thanks, AM [Mod. note: there are many reviews of this topic that you can find with a search engine or by searching ADS. For a recent one try http://arxiv.org/abs/1303.3274 -- mjh] IGM Emission Observations with the Cosmic Web Imager: I. The Circum-QSO Medium of QSO 1549+19, and Evidence for a Filamentary Gas Inflow http://arxiv.org/abs/1402.4816 IGM Emission Observations with the Cosmic Web Imager: II. Discovery of Extended, Kinematically-Linked Emission around SSA22 Lyα Blob 2 http://arxiv.org/abs/1402.4809 These two studies are at the nexus of gravitationally observed dark matter and gaseous neutral and ionized hydrogen observed by Lyman alpha. It is difficult to measure the described parameters but the most difficult is ideal gas temperature (good old PV=nRT). A finite Lyman alpha emission 121.60 nm indicates a temperature equivalent Planck*c/(Boltzmann*121.6)=118,320 K that is not energy equi-partitioned or in thermodynamic equilibrium with the hydrogen gas temperature. The gas temperature is linked to Maxwell Lyman alpha distribution and related velocity distribution The papers say temperatures on the order of 10,000 K, but I do not see the calculations. Hydrogen temperature and related velocity distribution would be on the order of: T (K) v (km/sec) 10,000 12.85 1,000 4.06 500 2.87 100 1.28 50 0.91 10 0.41 5 0.29 where v= SQRT(2*Boltzmann*T/hydrogen_mass) It is difficult to segregate this derived Maxwell distribution from all other velocities (in-out- rotational flows 300 - 1200 km/sec). These relatively small temperature related velocity distributions would be overwhelmed by the other kinetic velocity distributions. And then there are neutral and ionized hydrogen gases that may not be in thermodynamic equilibrium with each other. What are the temperatures of each? Hydrogen temperature may be an important issue in galactic formation but how is it (PV=nRT) measured in this extremely dynamic context? Within the limits of current observation, it could be cold(T near zero K) or hot(T in thousands of K)? and still be congruent with gravitational lensing observations. |
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