User talk:SkyFlubbler/Archives/2023/June

HyperLeda diameters

I have been surveying HyperLeda recently, due to my steadfastness in the belief that there must be angular diameters out there other than NED's. I found 2 diameter estimates; one (https://leda.univ-lyon1.fr/fG.cgi?n=a106&o=PGC037477) is the usual measurement of D25 (In the case of the extremely large Abell 1413 BCG, an angular diameter of 1.176 arcminutes.) The other (https://leda.univ-lyon1.fr/ledacat.cgi?PGC+139724++++++++++++++++++++) is 1.07+/- 0.05 arcminutes, but it is stated that this is log D25. When I accessed the meaning of log D25, It said that log D25 is the value of the D25 diameter in arcminutes into (Meaning multiplied with?) 0.1 arcminutes. An example of such a case is given. If the angular diameter of an object is 10 arcminutes, then the log D25 value will be 0.2 arcminutes. This made me confused, because 10×0.1 is 1. I am sorry If I am wrong with the calculations, I just want to know if these diameters can be applied or not. I am also sorry if I appear to be grasping at straws just for a small passage saying that Abell 1413-BCG is among the largest galaxies known, because I have a feeling that galaxy size is not talked about much anymore. Lastly, I apologize if I appear to be bad at Math, because I want to become an astronomer too.The Space Enthusiast (talk) 05:40, 6 June 2023 (UTC)

I am actually planning to also include the HyperLEDA database in the list for a few months now, as it can also be assessed to give a value of the physical diameters, so that we have another list of sources besides just using the NASA/IPAC Database. The only problem that I have is how to reconcile it with the current list.

Regarding log D25, the value listed there is the exponent. So you have to raise 10 by that amount. So 10^1.07 = 11.7489. Since that is 0.1 arcmin, that means this is 1.17489 or 1.175 arcmin. SkyFlubbler (talk) 05:48, 6 June 2023 (UTC)

Thank you so much! The reconciliation will be difficult, however. The Space Enthusiast (talk) 15:26, 6 June 2023 (UTC)

Thanks. I am sorry if I disturbed you, but when measuring the R90 diameters of galaxies such as ESO 383-76, are we including stars within the intracluster light, which is not part of the galaxy? The Space Enthusiast (talk) 01:30, 22 June 2023 (UTC)

Sersic/De Vaucouleurs profiles

While reading Kluge et al's paper on the structure of brightest cluster galaxies and the intracluster light, I had an idea that galaxy sizes could be calculated via the Sersic/De Vaucouleurs/R^1/4 profiles. Is this possible? Do note that this is for Original Research purposes. I also read that the ratio of the size of the BCG and the size of the ICL is on average between 0.1-0.4. Of course, the issue of the ICL continues to make me restless and empty, which is why I am asking you. The Space Enthusiast (talk) 02:26, 26 June 2023 (UTC)