Dark Matter Discovered in Accretion Disks (Forwarded)

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EMBARGOED FOR RELEASE: 10:30 a.m. CST, Wednesday, January 9, 2008

RELEASE NO: NOAO 08-02

Dark Matter Discovered in Accretion Disks -- Suggests Major Revisions to
Concepts of Disk Structure and Luminosity

Observations of the interacting binary star using telescopes at Kitt Peak
National Observatory and NASA's Spitzer Space Telescope suggest that the
disks of hot gas that accumulate around a wide variety of astronomical
objects -- from degenerate stars in energetic binary systems to
supermassive black holes at the hearts of active galaxies -- are likely to
be much larger than previously believed.

The target of this specific investigation, named WZ Sagittae (WZ Sge), is
an interacting binary star located in the constellation Sagitta, the arrow
of the archer Sagittarius. As part of a program called the Spitzer-NOAO
Observing Program for Teachers and Students, Steve B. Howell and a team of
astronomers and educators imaged WZ Sge using the National Science
Foundation's 2.1-meter telescope and the WIYN 0.9-meter telescope, both
located at Kitt Peak, and the Infrared Array Camera (IRAC) on Spitzer.

"We were very surprised to see the contrasting results obtained with the
optical telescopes on the ground and the infrared telescope in space,"
says Howell, an astronomer at the National Optical Astronomy Observatory
(NOAO) and leader of the team who made the discovery being reported today
in Austin, TX, at the 211th meeting of the American Astronomical Society
(AAS). "The much larger size of the infrared-emitting portion of the
accretion disk around WZ Sge was immediately obvious in the data. Our
observations strongly imply the presence of dark matter in these
structures, which are ubiquitous throughout the Universe."

Interacting binary stars such as WZ Sge contain a white dwarf star (a
compact star about the size of the Earth, but with a mass near that of the
Sun) and a larger, but less massive and much cooler companion star. The
companion, usually a low-mass star or a brown dwarf, has material ripped
off its surface by the stronger gravity of the white dwarf. This material
flows toward the more massive star and, in the process, forms a disk
surrounding the white dwarf, known as an accretion disk.

Stars such as WZ Sge are called cataclysmic variables due to their rapid
and often large changes in brightness, all caused by variations in the
accretion disk. The two stars in such systems orbit about each other at a
similar distance to that between Earth and the Moon, but with tremendous
angular momentum that results in orbital periods ranging from a few hours
down to as short as tens of minutes (the period of WZ Sge is 81 minutes).

Whether they form in cataclysmic variable systems or they surround the
massive black hole hearts of active galaxies, accretion disks have been
well observed and modeled using measurements obtained across much of the
electromagnetic spectrum, from X-rays to the near-infrared. The derived
picture of the "standard accretion disk" model is a geometrically thin
disk of gaseous material surrounding the white dwarf or black hole.
Accretion disk models, bolstered by observation, are generally composed of
hot gas having a temperature distribution within them, being hottest near
the center and falling off in temperature toward the outer edge.

In order to confirm the general accretion disk models and extend them into
the mid-infrared portion of the spectrum, Howell's team obtained the first
time series observations of an accretion disk system at 4.5 and 8 microns
with the Spitzer Space Telescope. At nearly the same time, they obtained
optical observations of WZ Sge at Kitt Peak. The optical observations
confirmed the standard view of the accretion disk size and temperature,
values known for over a decade.

The mid-infrared observations, however, were completely unexpected and
revealed that a larger, thicker disk of cool dusty material surrounds much
of the gaseous accretion disk. This outer dust disk likely contains as
much mass as a medium-sized asteroid. The newly discovered outer disk
extends about 20 times the radius of the gaseous disk.

"This discovery suggests that our current model for accretion disks of all
kinds is wrong," says team member Donald Hoard of the Spitzer Science
Center. "We will need to rethink and recast these models for accretion
disks, not only in interacting binary stars but also in distant, highly
luminous active galaxies."

The implications from such a discovery are far reaching, affecting not
only the theoretical models (since the formation and evolution of the
disks are modeled based on their size, temperature, and composition -- all
quantities that now need to be revised), but also nearly all previous
observations of systems containing accretion disks.

In addition, the dust disk (which is thicker than the known gaseous disk)
blocks infrared light emitted by the compact central object and the inner
hot regions of the gaseous disk. Not knowing that some mid to far infrared
light is blocked by the newly discovered outer dust ring can lead
observers to significantly underestimate the total luminosity of the
central object. "The amount of this underestimation is not yet accurately
known from our initial discovery, but may be as large as 50 percent,"
Howell says.

An artist's concept comparing the previous view and the new view of the
accretion disk around WZ Sge is available at
http://www.noao.edu/outreach/press/pr08/pr0802.html

The observational program making this discovery was a joint effort between
research scientists Howell, Hoard, and Carolyn Brinkworth of Spitzer
Science Center, and high school teacher Beth Thomas and student Kimmerlee
Johnson (Great Falls Public Schools, Great Falls, MT), teacher Jeff Adkins
and student John Michael Santiago (Deer Valley High School, Antioch, CA),
and teacher Tim Spuck and student Matt Walentosky (Oil City High School,
Oil City, PA).

The work was funded by Spitzer Science Center as part of a joint project
with NOAO to expand and extend the national observatory's Research Based
Science Education (RBSE) teacher professional development program to
include observations with the Spitzer Space Telescope. RBSE has been
training groups of 20 teachers in the research process (including regular
observations at Kitt Peak National Observatory) every year for more than a
decade, using funding support from NSF.

Kitt Peak National Observatory is part of the National Optical Astronomy
Observatory, based in Tucson, AZ, which is operated by the Association of
Universities for Research in Astronomy (AURA) under a cooperative
agreement with the NSF.

NASA's Jet Propulsion Laboratory, Pasadena, CA, manages the Spitzer Space
Telescope mission for NASA's Science Mission Directorate, Washington.
Science operations are conducted at the Spitzer Science Center at the
California Institute of Technology. Caltech manages JPL for NASA.

"Andrew Yee" wrote in message
...
....
Dark Matter Discovered in Accretion Disks
....
The mid-infrared observations, however, were
completely unexpected and revealed that a larger,
thicker disk of cool dusty material surrounds much
of the gaseous accretion disk.

Then it is *not* Dark Matter. It is cool normal matter.

David A. Smith

"N:dlzc D:aol T:com (dlzc)" wrote in message
...
"Andrew Yee" wrote in message
...
...
Dark Matter Discovered in Accretion Disks
...
The mid-infrared observations, however, were
completely unexpected and revealed that a larger,
thicker disk of cool dusty material surrounds much
of the gaseous accretion disk.

Then it is *not* Dark Matter. It is cool normal matter.

Also:

"In addition, the dust disk (which is thicker than the known
gaseous disk) blocks infrared light emitted by the compact
central object and the inner hot regions of the gaseous disk."

Dark matter doesn't interact with light. So again, this
is not dark matter.

Greg Neill wrote:
"N:dlzc D:aol T:com (dlzc)" wrote in message
...

"Andrew Yee" wrote in message
...
...

Dark Matter Discovered in Accretion Disks

...

The mid-infrared observations, however, were
completely unexpected and revealed that a larger,
thicker disk of cool dusty material surrounds much
of the gaseous accretion disk.

Then it is *not* Dark Matter. It is cool normal matter.


Also:

"In addition, the dust disk (which is thicker than the known
gaseous disk) blocks infrared light emitted by the compact
central object and the inner hot regions of the gaseous disk."

Dark matter doesn't interact with light. So again, this
is not dark matter.


There remains the possibility that dark matter is 'normal matter'
but of such size distribution that its aggregate optical path (mean free path)
dictates that it is unobservable from earth
except for its gravitational effects.

Richard D. Saam

"Richard Saam" wrote in message
...

There remains the possibility that dark matter is 'normal matter'
but of such size distribution that its aggregate optical path (mean free
path)
dictates that it is unobservable from earth
except for its gravitational effects.

But it wouldn't stay dark for long, particularly
in the infrared, as it absorbed ambient light and
warmed up.

It would also then be subject to frictional cooling
and aggregation, particularly into disks. We'd then
have the problem of explaining how so much matter
managed to remain in vast halos surrounding galaxies
rather than collapsing to their disks like the rest
of the matter.

Greg Neill wrote:
"Richard Saam" wrote in message
...


There remains the possibility that dark matter is 'normal matter'
but of such size distribution that its aggregate optical path (mean free

path)

dictates that it is unobservable from earth
except for its gravitational effects.


But it wouldn't stay dark for long, particularly
in the infrared, as it absorbed ambient light and
warmed up.
What if the dark (normal) matter
was in a milieu (isotropic continuous non ambient light absorptive medium)
with extremely cold temperature (~1E-16K)
with heat capacity to ameliorate any absorbed ambient light
onto dark (normal) matter
(ambient light would be extremely dim in interstellar, extragalactic space.

It would also then be subject to frictional cooling
and aggregation, particularly into disks.

Such dark matter could be as tenuous as 10 cm objects
at a radius from each other of 10,000 kilometers
(for aggregate density of ~1E-24 g/cc - approximate galactic density).
Negligible frictional cooling
may not interfere with Keplerian motion around the galactic center.

Interaction of tenuous dark (normal) matter
with the above milieu (through momentum transfer)
may result in the observed galactic accretion process
as well as observed flat galactic rotation curves.

Richard D. Saam

"Richard Saam" wrote in message
...
Greg Neill wrote:
"Richard Saam" wrote in message
...


There remains the possibility that dark matter is 'normal matter'
but of such size distribution that its aggregate optical path (mean free

path)

dictates that it is unobservable from earth
except for its gravitational effects.


But it wouldn't stay dark for long, particularly
in the infrared, as it absorbed ambient light and
warmed up.
What if the dark (normal) matter
was in a milieu (isotropic continuous non ambient light absorptive medium)
with extremely cold temperature (~1E-16K)
with heat capacity to ameliorate any absorbed ambient light
onto dark (normal) matter
(ambient light would be extremely dim in interstellar, extragalactic
space.

What might comprise such a milieu that is of sufficient
abundance? Normal matter from the early universe is largely
hydrogen and a smatter of helium with scant traces of
anything heavier.

Heat capacity can only delay the eventual warming to
ambient background temperatures, and large heat capacity
generally goes along with high molecular weights.


It would also then be subject to frictional cooling
and aggregation, particularly into disks.

Such dark matter could be as tenuous as 10 cm objects
at a radius from each other of 10,000 kilometers
(for aggregate density of ~1E-24 g/cc - approximate galactic density).
Negligible frictional cooling
may not interfere with Keplerian motion around the galactic center.

It would interact with other normal matter, so their
dynamics wouldn't be decoupled as they appear to be
from what we observe of normal matter. I would think
that we could expect to see similar ratios of densities
of "light" and "dark" matter in the halo and disk, which
is not what we see.


Interaction of tenuous dark (normal) matter
with the above milieu (through momentum transfer)
may result in the observed galactic accretion process
as well as observed flat galactic rotation curves.

I think you'd have to back up that claim with suitable
model simulations.

Dear Richard Saam:

"Richard Saam" wrote in message
...
....
Such dark matter could be as tenuous as 10 cm
objects at a radius from each other of 10,000
kilometers (for aggregate density of ~1E-24 g/cc
- approximate galactic density). Negligible
frictional cooling may not interfere with Keplerian
motion around the galactic center.

Interaction of tenuous dark (normal) matter
with the above milieu (through momentum transfer)
may result in the observed galactic accretion process
as well as observed flat galactic rotation curves.

But absorbs / scatters an abnormal amount of light. Such that
intensity would not agree with red shift for any source.

David A. Smith

Greg Neill wrote:

"Richard Saam" wrote in message
...

Greg Neill wrote:

"Richard Saam" wrote in message
...



There remains the possibility that dark matter is 'normal matter'
but of such size distribution that its aggregate optical path (mean free

path)


dictates that it is unobservable from earth
except for its gravitational effects.


But it wouldn't stay dark for long, particularly
in the infrared, as it absorbed ambient light and
warmed up.

What if the dark (normal) matter
was in a milieu (isotropic continuous non ambient light absorptive medium)
with extremely cold temperature (~1E-16K)
with heat capacity to ameliorate any absorbed ambient light
onto dark (normal) matter
(ambient light would be extremely dim in interstellar, extragalactic

space.

What might comprise such a milieu that is of sufficient
abundance? Normal matter from the early universe is largely
hydrogen and a smatter of helium with scant traces of
anything heavier.

The ubiquitous milieu could be related to universe critical density
(3/8pi)H^2/G ~ 1E-29 g/cc
Lets assume that this density is made of
particles with unobserved charge
(perhaps balancing or resonant + and - charges)
with a mass (m) between an electron and a proton.
Then each particle would occupy ~20 cm^3

Within this context a quantum mechanical temperature is suggested.

T = h^2/(2m) 1/20^2 / k = ~1E-16 K

Heat capacity can only delay the eventual warming to
ambient background temperatures, and large heat capacity
generally goes along with high molecular weights.

A milieu heat capacity of ~2E-19 erg/cm^3 is suggested

It would also then be subject to frictional cooling
and aggregation, particularly into disks.

Such dark matter could be as tenuous as 10 cm objects
at a radius from each other of 10,000 kilometers
(for aggregate density of ~1E-24 g/cc - approximate galactic density).
Negligible frictional cooling
may not interfere with Keplerian motion around the galactic center.

Assume a 10 cm dark matter particle
is exposed from a distance of 10 light years (9.5E+18 cm)
to our suns radiation
~1 joule / meter^2 /sec (1400 erg/cm^2/sec)
(at the earth sun radius of 1.5E+13 cm).

The 10 cm dark matter particle would receive:

1400*10^2*(1.5E+13)^2 /(9.5E+18)^2 = 3.49E-7 erg/sec

The milieu surrounding the 10 cm dark matter particle
would have heat capacity of 10,000 kilometers (1E8 cm)

2E-19 * 1E8^3 = 2E5 erg

Assuming milieu is in thermal equilibrium with the dark normal matter
then the time to heat up the 10 cm dark matter particle would be

2E5/3.49E-7 or 5.73E11 seconds
Compare this to the age of the universe
13.7 billion years (4.32E17 sec)

Yes, normally the 10 cm dark matter particle would heat up
but consider that the particle is at 1E-16 K.
At much higher temperatures than this,
Bose condensates have been formed from normal matter.

What is the radiation absorptivity of a Bose-Condensate.
I think it absorbs at one characteristic frequency
(exclusive of the majority of others)
which may make the above timing calculation
appropriatedly relative to the universe age.
I remember commentary
of the Bose Einstein Condensate (at ~1E-7 K)
produced at MIT (Nobel Prize Wolfgang Ketterle 2001),
exposed to ambient light with no consequence.


It would interact with other normal matter, so their
dynamics wouldn't be decoupled as they appear to be
from what we observe of normal matter.

A coupling of milieu with normal matter occurs
for normal matter less than a particular size
(10's of cm with large surface to mass ratios).
Objects greater than this size are negligibly coupled to the milieu
and tend to gravitationally aggregate into observable objects
(stars planets etc)

I would think
that we could expect to see similar ratios of densities
of "light" and "dark" matter in the halo and disk, which
is not what we see.

Yes, the above explanation could explain this.

Interaction of tenuous dark (normal) matter
with the above milieu (through momentum transfer)
may result in the observed galactic accretion process
as well as observed flat galactic rotation curves.


I think you'd have to back up that claim with suitable
model simulations.

Agreed.
I have done modeling on a simple spread sheet mode
and the model appears to work.

I wish I had access to greater computer power
and coordination with more astrophysical expertise.

Richard D. Saam

"Richard Saam" wrote in message
...
Greg Neill wrote:

"Richard Saam" wrote in message
...

Greg Neill wrote:

"Richard Saam" wrote in message
...



There remains the possibility that dark matter is 'normal matter'
but of such size distribution that its aggregate optical path (mean
free

path)


dictates that it is unobservable from earth
except for its gravitational effects.


But it wouldn't stay dark for long, particularly
in the infrared, as it absorbed ambient light and
warmed up.

What if the dark (normal) matter
was in a milieu (isotropic continuous non ambient light absorptive
medium)
with extremely cold temperature (~1E-16K)
with heat capacity to ameliorate any absorbed ambient light
onto dark (normal) matter
(ambient light would be extremely dim in interstellar, extragalactic

space.

What might comprise such a milieu that is of sufficient
abundance? Normal matter from the early universe is largely
hydrogen and a smatter of helium with scant traces of
anything heavier.

The ubiquitous milieu could be related to universe critical density
(3/8pi)H^2/G ~ 1E-29 g/cc
Lets assume that this density is made of
particles with unobserved charge
(perhaps balancing or resonant + and - charges)
with a mass (m) between an electron and a proton.
Then each particle would occupy ~20 cm^3

Within this context a quantum mechanical temperature is suggested.

T = h^2/(2m) 1/20^2 / k = ~1E-16 K

So you're proposing some new, previously unknown normal
matter particle suffusing space at a spacial density of
one per 20cm^3 volume. I don't see the benefit of this
proposal over that of the current dark matter proposals.


Heat capacity can only delay the eventual warming to
ambient background temperatures, and large heat capacity
generally goes along with high molecular weights.

A milieu heat capacity of ~2E-19 erg/cm^3 is suggested

Shouldn't that be erg/cm^3/K ?


It would also then be subject to frictional cooling
and aggregation, particularly into disks.

Such dark matter could be as tenuous as 10 cm objects
at a radius from each other of 10,000 kilometers
(for aggregate density of ~1E-24 g/cc - approximate galactic density).
Negligible frictional cooling
may not interfere with Keplerian motion around the galactic center.

Assume a 10 cm dark matter particle

A particle with a diameter of 10cm and a mass of about
half a proton. Okay...

is exposed from a distance of 10 light years (9.5E+18 cm)
to our suns radiation
~1 joule / meter^2 /sec (1400 erg/cm^2/sec)
(at the earth sun radius of 1.5E+13 cm).

The 10 cm dark matter particle would receive:

1400*10^2*(1.5E+13)^2 /(9.5E+18)^2 = 3.49E-7 erg/sec

The milieu surrounding the 10 cm dark matter particle
would have heat capacity of 10,000 kilometers (1E8 cm)

2E-19 * 1E8^3 = 2E5 erg

Huh? Don't these particles comprise the milieu? Or is
this milieu a separate property of space?


Assuming milieu is in thermal equilibrium with the dark normal matter
then the time to heat up the 10 cm dark matter particle would be

2E5/3.49E-7 or 5.73E11 seconds
Compare this to the age of the universe
13.7 billion years (4.32E17 sec)

So the time constant is about a millionth of the
age of the universe. Thus the milieu and your particles
would, for all intents and purposes, be in temperature
equilibrium with the universe as a whole over the lifetime
of the universe.


Yes, normally the 10 cm dark matter particle would heat up
but consider that the particle is at 1E-16 K.

No, I think it must be in temperature equilibrium as
infered from the relative length of the cooling/heating
time constant that you provided.

At much higher temperatures than this,
Bose condensates have been formed from normal matter.

What is the radiation absorptivity of a Bose-Condensate.
I think it absorbs at one characteristic frequency
(exclusive of the majority of others)
which may make the above timing calculation
appropriatedly relative to the universe age.
I remember commentary
of the Bose Einstein Condensate (at ~1E-7 K)
produced at MIT (Nobel Prize Wolfgang Ketterle 2001),
exposed to ambient light with no consequence.

Except we can *see* the Bose Einstein condensate by
reflected light. A BEC behaves quantumly much as if it was
a single extended atom, and as such should present a
pretty complex absorption/emission spectrum, having so
many electrons to diddle.

If the universe were filled with regions of BEC at 1E-16K,
this would be glaringly obvious from their excessively
cool temperatures compared to the general 2.9K background,
no?



It would interact with other normal matter, so their
dynamics wouldn't be decoupled as they appear to be
from what we observe of normal matter.

A coupling of milieu with normal matter occurs
for normal matter less than a particular size
(10's of cm with large surface to mass ratios).
Objects greater than this size are negligibly coupled to the milieu
and tend to gravitationally aggregate into observable objects
(stars planets etc)

I think you're stretching the credibility of things here,
adding ad hoc properties to cover deficiencies in the
basic premis. A dose of Occam is required :-)


I would think
that we could expect to see similar ratios of densities
of "light" and "dark" matter in the halo and disk, which
is not what we see.

Yes, the above explanation could explain this.

Interaction of tenuous dark (normal) matter
with the above milieu (through momentum transfer)
may result in the observed galactic accretion process
as well as observed flat galactic rotation curves.


I think you'd have to back up that claim with suitable
model simulations.

Agreed.
I have done modeling on a simple spread sheet mode
and the model appears to work.

I wish I had access to greater computer power
and coordination with more astrophysical expertise.

Richard D. Saam