johnnydeep wrote: ↑Sat Apr 23, 2022 8:57 pm
AVAO wrote: ↑Sat Apr 23, 2022 9:47 am
Ann wrote: ↑Sat Apr 23, 2022 4:57 am
They are undoubtedly listed in some kind of catalog, but I can't tell you which one.
in SIMBAD the mini-ensemble of 4 to 5 galaxies is not recorded. Under 2MASS and Gaia there are only cryptid numbers.
Four or five? Ok, checking more closely, you may be right! This is from the full 13500 x 8592 pixel image:
Or are 4 and 5 even more distant, and I guess there might be some hints of smaller galaxies almost embedded near 2 and 3?
How irritating. I made a long post about the "twin background galaxies near M104", which I will henceforth call "the twins".
But my post disappeared. I guess I may have forgotten to submit it.
So let me try again. The interesting thing about Johnny's image is that galaxy #5 is so similar in size and shape to the twins, but its color is so strikingly different. Is #5 so redshift-reddened, because it is a lot more distant than the twins? But if so, how can #5 be almost as big as the twins if it is far in the background? Are the twins so tiny?
I think that the crop from an M104 portrait from Wikipedia
gives us a better understanding.
Note in the Wikipedia crop the faintly reddish color of the extended outer arms or tidal tails of the twins. These features are made up of old yellow stars.
As for galaxy #5, its disk is clearly made up of old stars, too. This galaxy looks so red because we are looking at a redshift-reddened and rather faint stellar disk of intrinsically faint red and yellow stars. This is in stark contrast to the twins, whose inner arms are packed with brilliant blue and ultraviolet stars of an extremely high surface brightness.
But yes, I'm sure that the twins are intrinsically rather small, and smaller than galaxy #5. (Then again, I think galaxy #5 looks smaller in the Wikipedia crop than it does in Johnny's image, so that it is easier to accept that it is more distant than the twins.) I think the twins are similar to M83, if we disregard the fact that M83 is not interacting with a sibling galaxy:
According to ESO
, the diameter of M83 is only 40,000 light-years, which is less than half the size of the Milky Way. I have seen another estimate that makes it larger, some 55,000 light-years, but in any case, M83 is a smallish galaxy.
I really think that the twins are small, too. Note in Johnny's picture how big the resolved clusters are, and how compact the galaxies themselves are compared with the clusters in them. I think that large galaxies are very rarely so full of great clusters "all over".
The Pinwheel Galaxy, M101, is an exception to the rule that richly starforming galaxies that are full of hot bright stars "all over" aren't large. But M101 is clearly a very different type of galaxy than the twins in the background of M104.