Timeline for Bullet Cluster and MOND
Current License: CC BY-SA 3.0
5 events
| when toggle format | what | by | license | comment | |
|---|---|---|---|---|---|
| Oct 4, 2015 at 7:59 | comment | added | ProfRob | @DonaldRoyAirey You are correct to point out that there are inherent uncertainties in deprojecting 2D X-ray maps, but this is how it is done, and answers your question (without any assumptions about $\Lambda$CDM). If you now wish to shift the focus of your scepticism to another aspect of the process (the assumptions used to estimate gas masses from X-ray observations) then you should ask a different question. | |
| Oct 4, 2015 at 0:33 | comment | added | user32023 | All you know is the surface density. Without de-projection, you don't know the actual 3D density. We've got some pretty good science behind a Sersic or de Vaucouleurs profile, but I'm missing the part where we know the volume of a bow-shaped shock-wave based on the surface profile. I'd appreciate it if you can make the connection. | |
| Oct 3, 2015 at 23:06 | comment | added | ProfRob | @DonaldRoyAirey If I see a certain number of X-ray photons from a gas of a certain volume, then I can calculate the electron density of that gas, which then leads, without any assumptions about dark matter, to the mass of the X-ray emitting gas. The only place I see that requires a minor assumption about $\Lambda$CDM is in the assumed cosmology that tells you how big the bullet cluster is - ie the volume. As it is not very high redshift, this is not very important. | |
| Oct 3, 2015 at 22:18 | comment | added | user32023 | No, you are missing the point entirely. You can't measure the gas directly. You can measure the temperature and make a profile of the brightness. You cannot connect the temperature with a mass because there are dozens of unknowns: what is heating the gas? how long has it been cooling? Please provide some sort of paper that explains how the mass of the gas in the bullet cluster is determined (that isn't built on a house of cards of assumption). | |
| Oct 3, 2015 at 21:47 | history | answered | user10851 | CC BY-SA 3.0 |