Timeline for Why does the gas in the Bullet Cluster act like a lens?
Current License: CC BY-SA 3.0
6 events
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| Oct 11, 2015 at 14:20 | comment | added | user32023 | I'm sure you are talking about Strong Lens analysis. You seem too informed about the subject to not know that Weak Lens analysis (which is what is used in the Bullet Cluster) depends on a statistical analysis of the background stars within the cluster and is heavily dependent on the configuration on the mass in the foreground. A small sphere on this scale will focus the geodesics better than an amorphous cloud of higher mass. | |
| Oct 10, 2015 at 17:32 | comment | added | ProfRob | @DonaldRoyAirey The gravitational lensing analysis cares not a jot what form the gravitating mass is in that is the whole point. 9% of the mass is in the form of hot gas when analysed using a GR formalism. Who are "MOND people" and which papers claim the lensing can be explained without very significant quantities of dark (as in, we cannot see it) matter that is associated with the galaxy clusters and not the hot gas? | |
| Oct 10, 2015 at 16:53 | comment | added | user32023 | Yes, if you accept a priori Dark Matter, which I do not. Nor do I believe in MOND, but I'm trying to understand each other's arguments in objective terms. MOND people claim their relativistic model can bend light just as well as DM. I find that proposition no more preposterous than a stable, electrically neutral, non-relativistic particle that has been ruled out of the Standard Model. | |
| Oct 10, 2015 at 16:24 | comment | added | ProfRob | @DonaldRoyAirey Only 9% of the mass is in the form of hot gas. The lensing shows that most of the mass is still in and around the visible galaxies and not associated with the hot gas. | |
| Oct 10, 2015 at 15:40 | comment | added | user32023 | The argument for the Bullet Cluster goes something like this: 90% of the matter in the two clusters is in the form of gas, so the gravity lensing effect should be strongest around the gas. I appreciate the background material you provided, but it doesn't explain why we think the non-descript shape of the gas should have the same focusing ability as a relaxed spheroid. The mass of the gas may be 9 times that of the stellar matter, but I don't see how that translate into an ability to focus light. | |
| Oct 10, 2015 at 14:53 | history | answered | Ernie | CC BY-SA 3.0 |