Origins of Globular Clusters

[Drewster]

I have two questions about Globular Clusters:

1) How (under what conditions) did GCs from? Did they start out as very compact objects or did they begin as more extended groups of stars that then coalesced?

2) Are GCs still forming in our galaxy or in any other galaxies at present? If not, were they the result of conditions at one stage in the evolution of the universe (or one stage in the evolution of galaxies) which condtions no longer exist?

[neufer]

I have two questions about Globular Clusters:

1) How (under what conditions) did GCs from? Did they start out as very compact objects or did they begin as more extended groups of stars that then coalesced?

2) Are GCs still forming in our galaxy or in any other galaxies at present? If not, were they the result of conditions at one stage in the evolution of the universe (or one stage in the evolution of galaxies) which conditions no longer exist?

Earlier in the evolution of the universe there were probably more numerous large concentrations of dense gas that became Globular Clusters.

Today, smaller concentrations of dense gas can only become Open Clusters.

<<At present the formation of globular clusters remains a poorly understood phenomenon, and it remains uncertain whether the stars in a globular cluster form in a single generation, or are spawned across multiple generations over a period of several hundred million years. In many globular clusters, most of the stars are at approximately the same stage in stellar evolution, suggesting that they formed at about the same time. However, the star formation history varies from cluster to cluster, with some clusters showing distinct populations of stars. An example of this is the globular clusters in the Large Magellanic Cloud (LMC) that exhibit a bimodal population. During their youth, these LMC clusters may have encountered giant molecular clouds that triggered a second round of star formation. This star-forming period is relatively brief, compared to the age of many globular clusters.

Observations of globular clusters show that these stellar formations arise primarily in regions of efficient star formation, and where the interstellar medium is at a higher density than in normal star-forming regions. Globular cluster formation is prevalent in starburst regions and in interacting galaxies. Research indicates a correlation between the mass of a central supermassive black holes (SMBH) and the extent of the globular cluster systems of elliptical and lenticular galaxies. The mass of the SMBH in such a galaxy is often close to the combined mass of the galaxy's globular clusters.

No known globular clusters display active star formation, which is consistent with the view that globular clusters are typically the oldest objects in the Galaxy, and were among the first collections of stars to form. Very large regions of star formation known as super star clusters, such as Westerlund 1 in the Milky Way, may be the precursors of globular clusters.>>

[Drewster]

Earlier in the evolution of the universe there were probably more numerous large concentrations of dense gas that became Globular Clusters.

Thanks. I think that is the information I was looking for.

Drew S.

[dougettinger]

I have two questions about Globular Clusters:

1) How (under what conditions) did GCs from? Did they start out as very compact objects or did they begin as more extended groups of stars that then coalesced?

2) Are GCs still forming in our galaxy or in any other galaxies at present? If not, were they the result of conditions at one stage in the evolution of the universe (or one stage in the evolution of galaxies) which conditions no longer exist?

Earlier in the evolution of the universe there were probably more numerous large concentrations of dense gas that became Globular Clusters.

Today, smaller concentrations of dense gas can only become Open Clusters.

<<At present the formation of globular clusters remains a poorly understood phenomenon, and it remains uncertain whether the stars in a globular cluster form in a single generation, or are spawned across multiple generations over a period of several hundred million years. In many globular clusters, most of the stars are at approximately the same stage in stellar evolution, suggesting that they formed at about the same time. However, the star formation history varies from cluster to cluster, with some clusters showing distinct populations of stars. An example of this is the globular clusters in the Large Magellanic Cloud (LMC) that exhibit a bimodal population. During their youth, these LMC clusters may have encountered giant molecular clouds that triggered a second round of star formation. This star-forming period is relatively brief, compared to the age of many globular clusters.

Observations of globular clusters show that these stellar formations arise primarily in regions of efficient star formation, and where the interstellar medium is at a higher density than in normal star-forming regions. Globular cluster formation is prevalent in starburst regions and in interacting galaxies. Research indicates a correlation between the mass of a central supermassive black holes (SMBH) and the extent of the globular cluster systems of elliptical and lenticular galaxies. The mass of the SMBH in such a galaxy is often close to the combined mass of the galaxy's globular clusters.

No known globular clusters display active star formation, which is consistent with the view that globular clusters are typically the oldest objects in the Galaxy, and were among the first collections of stars to form. Very large regions of star formation known as super star clusters, such as Westerlund 1 in the Milky Way, may be the precursors of globular clusters.>>

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I concur with most of Wikipedia, but add some different spins on the topic of globular clusters (GC's) and appreciate any commentary.

1. Globular clusters began in the early universe 100 million years or more after the Big Bang along with their larger brethren, elliptical galaxies. This time was when the first generation stars were formed into regions of clumpiness that became the first ellipticals and smaller GCs.
2. The GC's became gravitationally attracted to the larger ellipticals but remain detached and separate near the outside perimeter. 3. Within the next 100 million to one billion years the fast moving ellipticals collided with others creating at a very early stage spiral and lenticular galaxies.
4. The GC's for the most part remained and re-aligned themselves in a spherical envelop around the newly formed spiral galaxies.
5. In numerous cases the GC's interacted with each other or directly with the colliding galaxies providing different star evolutions, but the general trend for GC's is that they did not interact during these galactic collisions. Due to little re-processing these GC's became some of the oldest structures in the universe.

Always keeping an open mind,

[dougettinger]

Hello Ann,

One or more years ago I talked to Ann who was an expert on galaxies (their ages, colors, shapes, types of stars, etc.). Is that very Ann still in this forum? I am not sure whether she is Ann, the Commodore.

Anyway, I am hoping this Ann will have some commentary for my above idea. I know there are strong opinions about whether elliptical or spiral galaxies came first. My reason is that ellipticals came first and then collided to form spirals. How else could spirals obtain their kinetic energy to start spinning.

Looking for other open minds like Ann's,

[Chris Peterson]

I know there are strong opinions about whether elliptical or spiral galaxies came first. My reason is that ellipticals came first and then collided to form spirals. How else could spirals obtain their kinetic energy to start spinning.

Galaxies don't spin; rather, their constituent stars orbit. This is as true for elliptical galaxies as for spirals. The difference between the two is that in a spiral galaxy the disc stars are orbiting in the same direction and on the same plane (not so the bulge stars, however, which may account for most of the mass of the galaxy) whereas in an elliptical galaxy the stellar orbits have random inclinations. A spiral galaxy does not have more kinetic energy than an elliptical galaxy, which in both cases is merely the sum of the kinetic energies of all the component stars.

It is clear that some elliptical galaxies are the product of spiral galaxies that have collided. The problem with any scenario that has colliding galaxies (elliptical or otherwise) producing a spiral galaxy is that there's no known mechanism for forming a disc- a large grouping of stars orbiting on the same plane- without the fluid dynamic effects present in the early Universe when there were fewer stars and much more gas.

[owlice]

Doug, Ann is still here, but is not nearly so much the expert on galaxies as the astronomers and astrophysicists who actually study them. The Wikipedia article here is a good introduction to the topic. You can find references there which will take you to academic articles on galaxy evolution, and from those, you can find many, many others.

[dougettinger]

Doug, Ann is still here, but is not nearly so much the expert on galaxies as the astronomers and astrophysicists who actually study them. The Wikipedia article here is a good introduction to the topic. You can find references there which will take you to academic articles on galaxy evolution, and from those, you can find many, many others.

Thank you, Owl ice, I know this article very well and some of its references.

Trying not to be too complacent with Wikipedia,

[owlice]

You don't have to be "complacent" with Wikipedia; it can be an excellent place to start, as the articles often lead the reader to peer-reviewed journal articles. And that's really what you should be reading if you're interested in this: research papers.

[dougettinger]

Hello Owlice,

What kind of name do you have? I know well about research and all the references that Wikipedia provides. But, I am lonely and love to socialize with professional scientists.

The Forum soothes the soul -

[owlice]

Hello Owlice,

What kind of name do you have? I know well about research and all the references that Wikipedia provides. But, I am lonely and love to socialize with professional scientists.

The Forum soothes the soul -

Doug, I don't understand your question. What do you mean, what kind of name do I have?

[dougettinger]

Owlice is an unusual first name. Perhaps Owlice is your last name. That is what I meant. Doug

[owlice]

Oh! It's a nickname.

[dougettinger]

I am sure it has a unique derivation.

[Chris Peterson]

I am sure it has a unique derivation.

Alice?

[dougettinger]

Chris, are you telling me or are you hypothesizing about Owlice? Doug

[Chris Peterson]

Chris, are you telling me or are you hypothesizing about Owlice? Doug

Just a wild guess.

[neufer]

Chris, are you telling me or are you hypothesizing about Owlice? Doug

Just a wild guess.

http://asterisk.apod.com/viewtopic.php?f=9&t=23548

[dougettinger]

After doing some research on the forum, it has come to my knowledge that she or he likes owls. Doug

[Nikolai Pohodenko]

It is clear that some elliptical galaxies are the product of spiral galaxies that have collided. The problem with any scenario that has colliding galaxies (elliptical or otherwise) producing a spiral galaxy is that there's no known mechanism for forming a disc- a large grouping of stars orbiting on the same plane- without the fluid dynamic effects present in the early Universe when there were fewer stars and much more gas.

I believe that eliptical galagies came before spirals.
In fact, dark-matter galaxies formed first, then they sucked in stars, globular clusters and SMBHs, which formed in parallel to (if not earlier than) dark-matter galaxies. Due to radiative cooling , ordinary matter can clump up faster than dark matter, resulting in formation of smaller and denser objects i.e. stars and globular clusters. Whereas dark matter formed such fuzzy megastructures as galaxies and galaxy clasters.
So here is my view on the topic of galactic bulge formation, star formation, globular cluster formation.

Concerning spiral galaxies. Once formed, galactic bulges drew in hydrogen gas halos, which rapidly cooled down into thin disks, where formation of star population-I ensured. All in all, I regard galactic disc as a feature an eliptical galaxy may put on under conditions of gas abundance and loose again in the process of major mergers.