tag:blogger.com,1999:blog-2361412992308994774.post5212037071483254710..comments2023-11-19T19:19:12.773-05:00Comments on Dealing with Creationism in Astronomy: Discordant Redshifts: A Post-MortemW.T."Tom" Bridgmanhttp://www.blogger.com/profile/10889134728080314165noreply@blogger.comBlogger6125tag:blogger.com,1999:blog-2361412992308994774.post-3671477973537052732013-06-20T02:16:51.876-04:002013-06-20T02:16:51.876-04:00Jean, we started doing volume 2 for this catalog b...Jean, we started doing volume 2 for this catalog but all the guys got busy with something else and project then drifted to the background and died.Ari Jokimäkihttps://arijmaki.wordpress.com/noreply@blogger.comtag:blogger.com,1999:blog-2361412992308994774.post-25025965048156964782013-06-19T12:35:38.782-04:002013-06-19T12:35:38.782-04:00@Ari: Have you thought about doing follow-on work,...@Ari: Have you thought about doing follow-on work, looking for M51-like galaxies in the Galaxy Zoo overlaps catalog (see http://data.galaxyzoo.org/overlaps.html), or searching the SDSS DR8 (or DR9) data (using CasJobs, for example)? The role of small companions in creating and sustaining 'grand design' spiral arm systems is an interesting one, and a larger catalog could be useful.<br /><br />Jean TateAnonymousnoreply@blogger.comtag:blogger.com,1999:blog-2361412992308994774.post-13218314420883559632013-06-18T20:40:52.755-04:002013-06-18T20:40:52.755-04:00To Ari,
Are you really unfamiliar with how Arp an...To Ari,<br /><br />Are you really unfamiliar with how Arp and supporters have poisoned the terminology in this topic? Another researcher who was examining planetary orbit resonances used the term 'quantization', apparently unfamiliar with how loaded that term had become (see comments in <a href="http://dealingwithcreationisminastronomy.blogspot.com/2011/09/geocentrisms-quantized-planetary-orbits.html" rel="nofollow">Geocentrism's "Quantized Planetary Orbits"</a>). <br />I've perused your paper linked above.<br /><br />It appears you are making a legitimate investigation of possibly interacting galaxies. <br /><br />You still resort to Arp's probability computation which treats the universe as a 2-D projection on a spherical surface. I explore some of the problems with that with the 3-D examples in the earlier posts. It is explored in more mathematical detail by <a href="http://adsabs.harvard.edu/abs/1975Ap%26SS..38..457N" rel="nofollow">Noerdlinger (1975)</a>.<br /><br />You note that 17 of the 41 pairs with published redshifts have a velocity difference > = 1000 km/s = delta_z of 0.00333. <br />a) Most of your pairs are certainly not that 'discordant' in context usually meant in the topic (redshifts differing by factors of 2-10 and larger) and are probably legitimate interactions.<br />b) a 1000 km/s difference is within the velocity dispersion (<a href="https://en.wikipedia.org/wiki/Velocity_dispersion" rel="nofollow">Wikipedia</a>) of rich clusters of galaxies.<br /><br />Other possible analyses you should consider:<br />1) You could use the implied velocities and positions (in 3-D space) to compute a possible time of the interaction as a test of a past (or future) interaction.<br /><br />2) Is the 'strength' of the interaction between the galaxies dependent on the apparent distance of separation (including the 3rd dimension implied by redshift)?<br /><br />You might also enjoy a warmer reception by the community if you don't use the term 'discordant' when describing even small differences in redshift.<br /><br />TomW.T."Tom" Bridgmanhttps://www.blogger.com/profile/10889134728080314165noreply@blogger.comtag:blogger.com,1999:blog-2361412992308994774.post-55337137265107891952013-06-18T09:31:33.205-04:002013-06-18T09:31:33.205-04:00Discordant redshifts are often present in basic ex...Discordant redshifts are often present in basic extragalactic astronomy. An example of that is our paper (<a href="http://link.springer.com/article/10.1007/s10509-008-9826-3" rel="nofollow">Jokimäki et al. 2008</a>). Imagine our surprise when we found out that 40 % of our sample belongs into the realm of crank science.Ari Jokimäkihttps://arijmaki.wordpress.com/noreply@blogger.comtag:blogger.com,1999:blog-2361412992308994774.post-16119075956827865522013-06-17T21:53:52.632-04:002013-06-17T21:53:52.632-04:00To Ari,
If they are just chance alignments, I can...To Ari,<br /><br />If they are just chance alignments, I can't help but wonder what those issues might be, beyond a certain aesthetic of the imagery.<br /><br />TomW.T."Tom" Bridgmanhttps://www.blogger.com/profile/10889134728080314165noreply@blogger.comtag:blogger.com,1999:blog-2361412992308994774.post-75339011893754249662013-06-17T09:47:53.767-04:002013-06-17T09:47:53.767-04:00Just for the record: I'm not advocating discor...Just for the record: I'm not advocating discordant redshifts, just studying the issues relating to them.Ari Jokimäkihttps://arijmaki.wordpress.com/noreply@blogger.com