Black hole content of ellipticals (was: Galaxies without dark

In article ,
Gene Partlow wrote:
Has there been any *theoretical* work suggesting that some ellipticals
should have an unusually low stellar mass black hole content...eg: because
conditions exist which have suppressed formation of sufficiently high mass
stars whose end states include the creation of bhs? If so, this would be
circumstantial evidence for a bh/dark matter link of some sort.

I don't know a direct answer to this question, but if you think that
massive ellipticals are formed from the merger of smaller systems,
including spirals, then there's no obvious reason why they should have
many fewer stellar-mass black holes. As I understand it, the theory of
what determines the initial mass function of stars in *any* kind of
system is pretty sketchy -- perhaps someone who knows something about
stars will come out of the woodwork and correct me at this point!

Martin
--
Martin Hardcastle Department of Physics, University of Bristol
A little learning is a dangerous thing; / Drink deep, or taste not the
Pierian spring; / There shallow draughts intoxicate the brain ...

In article ,
Gene Partlow wrote:
Has there been any *theoretical* work suggesting that some ellipticals
should have an unusually low stellar mass black hole content...eg: because
conditions exist which have suppressed formation of sufficiently high mass
stars whose end states include the creation of bhs? If so, this would be
circumstantial evidence for a bh/dark matter link of some sort.

I don't know a direct answer to this question, but if you think that
massive ellipticals are formed from the merger of smaller systems,
including spirals, then there's no obvious reason why they should have
many fewer stellar-mass black holes. As I understand it, the theory of
what determines the initial mass function of stars in *any* kind of
system is pretty sketchy -- perhaps someone who knows something about
stars will come out of the woodwork and correct me at this point!

Martin
--
Martin Hardcastle Department of Physics, University of Bristol
A little learning is a dangerous thing; / Drink deep, or taste not the
Pierian spring; / There shallow draughts intoxicate the brain ...

Gene Partlow wrote in message
...
Several elliptical galaxies (eg: M105) have apparently little or no dark
matter content. Some theorists have conjectured that some dark matter
is associated with stellar mass black holes, though this does not seem
to be the case with our Milky Way spiral galaxy (viz: microlensing and
x-ray surveys). However, if these ellipticals do have a unusually low
total black hole mass content, that might be a check on the conjectured
bh/dark matter link.

Stellar mass black holes are notoriously difficult to detect at the
distances
of the ellipticals in question, so I have a backdoor 'theoretical'
question:

Has there been any *theoretical* work suggesting that some ellipticals
should have an unusually low stellar mass black hole content...eg: because
conditions exist which have suppressed formation of sufficiently high mass
stars whose end states include the creation of bhs? If so, this would be
circumstantial evidence for a bh/dark matter link of some sort.

I have wondered if dark matter would always be
present with matter, suggesting that it was a
characteristic of matter itself that was not understood.
I still think that it may be possible that there is a lack
of understanding about the dynamics of systems that
involve massive core concentrations. Does anyone
know if these particular eliptical galaxies have
concentrated cores? If they do not I wonder if it is
possible to judge whether there is still a need for an
external dark matter halo to explain their dynamics
with other galaxies?

Gene Partlow wrote in message
...
Several elliptical galaxies (eg: M105) have apparently little or no dark
matter content. Some theorists have conjectured that some dark matter
is associated with stellar mass black holes, though this does not seem
to be the case with our Milky Way spiral galaxy (viz: microlensing and
x-ray surveys). However, if these ellipticals do have a unusually low
total black hole mass content, that might be a check on the conjectured
bh/dark matter link.

Stellar mass black holes are notoriously difficult to detect at the
distances
of the ellipticals in question, so I have a backdoor 'theoretical'
question:

Has there been any *theoretical* work suggesting that some ellipticals
should have an unusually low stellar mass black hole content...eg: because
conditions exist which have suppressed formation of sufficiently high mass
stars whose end states include the creation of bhs? If so, this would be
circumstantial evidence for a bh/dark matter link of some sort.

I have wondered if dark matter would always be
present with matter, suggesting that it was a
characteristic of matter itself that was not understood.
I still think that it may be possible that there is a lack
of understanding about the dynamics of systems that
involve massive core concentrations. Does anyone
know if these particular eliptical galaxies have
concentrated cores? If they do not I wonder if it is
possible to judge whether there is still a need for an
external dark matter halo to explain their dynamics
with other galaxies?

Ed Keane III wrote in message ...

I have wondered if dark matter would always be
present with matter, suggesting that it was a
characteristic of matter itself that was not understood.

Yes, this is my intuition also...that there are no exotic dark matter
particles floating around waiting to be discovered. That the dark
matter gravitational potential has its origin in so called luminous
matter in some special and unsuspected state. My own toy model
involves daughter universes, formed by black holes, propagating
some of their gravitation back into our universe as 'dark matter'
potential. I'll refrain from details here to keep my mild heresy
from being ejected from this garden by the proper authorities.

I still think that it may be possible that there is a lack
of understanding about the dynamics of systems that
involve massive core concentrations.

How do you mean?

Does anyone
know if these particular eliptical galaxies have
concentrated cores?

Dunno...however some have supermassive black holes (that of
M105 in their sample weighing in at ~50 million Msols) and those
tend to be associated with concentrated cores or cusps.

If they do not I wonder if it is
possible to judge whether there is still a need for an
external dark matter halo to explain their dynamics
with other galaxies?

Good question. I don't now if their dynamics with adjacent galaxies
has been studied and whether they show higher velocities than ex-
pected from their luminous mass. However I suspect that any local
dark matter potential effect will be swamped by the overall dark
matter content of their home cluster or supercluster of galaxies.

Cheers,

Gene

Ed Keane III wrote in message ...

I have wondered if dark matter would always be
present with matter, suggesting that it was a
characteristic of matter itself that was not understood.

Yes, this is my intuition also...that there are no exotic dark matter
particles floating around waiting to be discovered. That the dark
matter gravitational potential has its origin in so called luminous
matter in some special and unsuspected state. My own toy model
involves daughter universes, formed by black holes, propagating
some of their gravitation back into our universe as 'dark matter'
potential. I'll refrain from details here to keep my mild heresy
from being ejected from this garden by the proper authorities.

I still think that it may be possible that there is a lack
of understanding about the dynamics of systems that
involve massive core concentrations.

How do you mean?

Does anyone
know if these particular eliptical galaxies have
concentrated cores?

Dunno...however some have supermassive black holes (that of
M105 in their sample weighing in at ~50 million Msols) and those
tend to be associated with concentrated cores or cusps.

If they do not I wonder if it is
possible to judge whether there is still a need for an
external dark matter halo to explain their dynamics
with other galaxies?

Good question. I don't now if their dynamics with adjacent galaxies
has been studied and whether they show higher velocities than ex-
pected from their luminous mass. However I suspect that any local
dark matter potential effect will be swamped by the overall dark
matter content of their home cluster or supercluster of galaxies.

Cheers,

Gene