VictorBorun wrote: ↑Tue Dec 03, 2024 3:41 pm
Ann wrote: ↑Wed Nov 27, 2024 4:01 pm
VictorBorun wrote: ↑Wed Nov 27, 2024 2:55 pm
Can we say a large regular galaxy has 2 components, a planar viscous gas/dust disk and a spherical purely stellar bulge,
if the bulge is tiny then it is called a core and the host galaxy is called a disk galaxy;
if the disk is tiny then the host galaxy is called an elliptic galaxy?
Sounds good to me, except the core is not the bulge. The core is tiny, and the bulge is larger than the core.
Ann
Ethan Siegel at last got to sum up the JWST's new Sombrero and mentioned that a bulge may be the remnants of all the other galaxies in a cluster that the Sombrero had devoured
The Sombrero likely represents a galactic end-state: where a massive spiral has completely devoured its neighbors.
The numerous X-sources in the bulge and the halo must be massive black holes. I think it means they had been central BHs in the galaxies past
Very interesting, Victor, but let me chime in with some of my amateur "wisdom":
The dust lane of M104 is extremely, extremely straight. I don't think it could possibly be that straight if it had undergone any sort of major mergers within, say, the last, perhaps 3 billion years or so. In other words, I don't think it could possibly have undergone any sort of major merger recently.
I still like this old explanation:
Universe Today wrote:
Although it might seem that the Sombrero is the result of a collision between two separate galaxies, that’s actually not thought to be the case.
Such an event would have destroyed the disk structure that’s seen today;
instead, it’s thought that the Sombrero accumulated a lot of extra gas billions of years ago when the Universe was populated with large clouds of gas and dust. The extra gas fell into orbit around the galaxy, eventually spinning into a flattened disk and forming new stars.
Perhaps, if so much gas fell into orbit around the Sombrero Galaxy, there was not much gas left for companion galaxies to form?
As for the X-ray sources in M104's halo, I think it's very reasonable that a giant elliptical galaxy should have undergone bursts of star formation that have left black holes behind. The only problem is that I don't see how the halo black holes could be supergiant in size, since that would require that sort of galactic mergers that would have destroyed the Sombrero's perfectly straight dust lane.
The black holes could well be stellar mass black holes instead. However, to be detectable as X-ray sources, I think that these black holes must be accreting matter. Surely there isn't that much matter to accrete in the halo? Perhaps the X-ray black holes are accreting matter from a swollen companion.
I was surprised at Ethan Siegel's estimate of the rate of star formation in M104:
Ethan Siegel wrote:
Within it, only one solar mass worth of new stars forms annually.
Really? One solar mass worth of new stars forming annually is about the rate of star formation of the Milky Way. Yet our galaxy has indeed produced a few big and bright clusters that should be easily visible for astronomers on a planet in the Sombrero Galaxy, if they had a telescope with the power of Hubble of James Webb.
If the Milky Way, with its rate of star formation of one solar mass per year, has been able to produce two such massive clusters an NGC 3603 and Westerlund 1 in the last few million years, why is it that we don't see any signs of any large young clusters whatsoever in the dust lane of M104? If that galaxy's rate of star formation is the same as ours?
Let's make one more comparison. The Andromeda galaxy forms stars at a slightly slower rate than the Milky Way does. Even so, it has formed enough young stars for the now-defunct ultraviolet-detecting telescope GALEX to detect a lot of ultraviolet young stars in Andromeda. So how many hot young stars did GALEX detect in M104?
Ultraviolet stars in M104 (in blue). Can you see any?
Credit: NASA/JPL-Caltech
Even more interesting than comparing M104 to Andromeda is a comparison between M104 and Centaurus A. Not how much blue light GALEX detected in the dus lane of Centaurus A - a lot of massive hot stars are forming here:
Centaurus A by GALEX. Note all the ultraviolet stars (in blue).
Credit: NASA/JPL-Caltech.
So, in short: Because we can't see any definite signs of any young clusters in M104, and because NASA's GALEX telescope hardly detected any ultraviolet light from this galaxy at all, I just can't believe that M104 is forming one stellar mass of new stars every year, the way the Milky Way and Andromeda does. I believe that M104's rate of star formation must be a lot lower. Either that, or it only forms stars that aren't hot or massive enough to emit much ultraviolet light, and don't stick together with other young stars to form clusters.
Ann
