by Ann » Fri Dec 01, 2017 6:16 am
sallyseaver wrote:sillyworm2 wrote:Does the size of the existing Black Hole at the center of M33 determine the size of the central bulge?
Yes. The bulge takes time to develop in the lifecycle of a galaxy. Once the bulge forms, the mass of the black hole is .1% of the mass of the bulge. This is the updated Magorrian relation, which you can find in Wikipedia under M-sigma relation.
I believe that M33 is too young to have a fully developed bulge.
I wouldn't make such an assumption. Most galaxies contain at least some very old stars, which suggests that at least some parts of the galaxy have been around for a long time. To the best of my knowledge, astronomers have not yet found a truly young galaxy.
Whether or not a galaxy has a large bulge depends, in my amateur opinion, on whether or not it has experienced either of these star formation histories:
a) One mega-massive super-duper burst of star formation, the kind of which is only seen in the very early universe and its ultra luminous infrared galaxies (galaxies which are choking in dust because of their almost impossibly massive bursts of star formation).
b) Many relatively massive bursts of star formation.
c) A slow, steady rate of star formation that goes on for billions of years, creating new stars whose low-mass members will build up the galactic bulge (and whose very massive stars may contribute to the mass of the galaxy's central black hole).
If a galaxy has never experienced a truly super-massive burst of star formation, or if its relatively massive bursts of star formation have been too few, or if the galaxy has not experienced a steady, uninterrupted rate of star formation for billions of years, then the galaxy may not develop a bright bulge at all.
Please note that M33 does have a bulge, or at the very least, it does have a yellow center. The center of M33 is much yellower than the bar of the Large Magellanic Cloud, for example. So M33 has been more efficient than LMC when it comes to building up a yellow center.
Ann
[quote="sallyseaver"][quote="sillyworm2"]Does the size of the existing Black Hole at the center of M33 determine the size of the central bulge?[/quote]
Yes. The bulge takes time to develop in the lifecycle of a galaxy. Once the bulge forms, the mass of the black hole is .1% of the mass of the bulge. This is the updated Magorrian relation, which you can find in Wikipedia under M-sigma relation.
[b][color=#FF0000]I believe that M33 is too young to have a fully developed bulge[/color][/b].[/quote]
I wouldn't make such an assumption. Most galaxies contain at least some very old stars, which suggests that at least some parts of the galaxy have been around for a long time. To the best of my knowledge, astronomers have not yet found a truly young galaxy.
Whether or not a galaxy has a large bulge depends, in my amateur opinion, on whether or not it has experienced either of these star formation histories:
a) One mega-massive super-duper burst of star formation, the kind of which is only seen in the very early universe and its ultra luminous infrared galaxies (galaxies which are choking in dust because of their almost impossibly massive bursts of star formation).
b) Many relatively massive bursts of star formation.
c) A slow, steady rate of star formation that goes on for billions of years, creating new stars whose low-mass members will build up the galactic bulge (and whose very massive stars may contribute to the mass of the galaxy's central black hole).
If a galaxy has never experienced a truly super-massive burst of star formation, or if its relatively massive bursts of star formation have been too few, or if the galaxy has not experienced a steady, uninterrupted rate of star formation for billions of years, then the galaxy may not develop a bright bulge at all.
Please note that M33 does have a bulge, or at the very least, it does have a yellow center. The center of M33 is much yellower than the bar of the Large Magellanic Cloud, for example. So M33 has been more efficient than LMC when it comes to building up a yellow center.
Ann