Halo White Dwarfs and Baryonic Dark Matter

Author(s):  
B. D. Fields ◽  
G. J. Mathews ◽  
D. N. Schramm
2021 ◽  
Vol 2021 (3) ◽  
Author(s):  
David Curtin ◽  
Jack Setford

Abstract Dark matter could have a dissipative asymmetric subcomponent in the form of atomic dark matter (aDM). This arises in many scenarios of dark complexity, and is a prediction of neutral naturalness, such as the Mirror Twin Higgs model. We show for the first time how White Dwarf cooling provides strong bounds on aDM. In the presence of a small kinetic mixing between the dark and SM photon, stars are expected to accumulate atomic dark matter in their cores, which then radiates away energy in the form of dark photons. In the case of white dwarfs, this energy loss can have a detectable impact on their cooling rate. We use measurements of the white dwarf luminosity function to tightly constrain the kinetic mixing parameter between the dark and visible photons, for DM masses in the range 10−5–105 GeV, down to values of ϵ ∼ 10−12. Using this method we can constrain scenarios in which aDM constitutes fractions as small as 10−3 of the total dark matter density. Our methods are highly complementary to other methods of probing aDM, especially in scenarios where the aDM is arranged in a dark disk, which can make direct detection extremely difficult but actually slightly enhances our cooling constraints.


2009 ◽  
Vol 36 ◽  
pp. 263-268 ◽  
Author(s):  
F. Mayet ◽  
O. Guillaudin ◽  
D. Santos ◽  
A. Trichet

Galaxies ◽  
2020 ◽  
Vol 8 (4) ◽  
pp. 77
Author(s):  
Anne M. Hofmeister

To explain rotation curves of spiral galaxies through Newtonian orbital models, massive halos of non-baryonic dark matter (NBDM) are commonly invoked. The postulated properties are that NBDM interacts gravitationally with baryonic matter, yet negligibly interacts with photons. Since halos are large, low-density gaseous bodies, their postulated attributes can be tested against classical thermodynamics and the kinetic theory of gas. Macroscopic models are appropriate because these make few assumptions. NBDM–NBDM collisions must be elastic to avoid the generation of light, but this does not permit halo gas temperature to evolve. If no such collisions exist, then the impossible limit of absolute zero would be attainable since the other available energy source, radiation, does not provide energy to NBDM. The alternative possibility, an undefined temperature, is also inconsistent with basic thermodynamic principles. However, a definable temperature could be attained via collisions with baryons in the intergalactic medium since these deliver kinetic energy to NBDM. In this case, light would be produced since some proportion of baryon collisions are inelastic, thereby rendering the halo detectable. Collisions with baryons are unavoidable, even if NBDM particles are essentially point masses. Note that <0.0001 × the size of a proton is needed to avoid scattering with γ-rays, the shortest wavelength used to study halos. If only elastic collisions exist, NBDM gas would collapse to a tiny, dense volume (zero volume for point masses) during a disturbance—e.g., cosmic rays. NBDM gas should occupy central galactic regions, not halos, since self-gravitating objects are density stratified. In summary, properties of NBDM halos as postulated would result in violations of thermodynamic laws and in a universe unlike that observed.


2004 ◽  
Vol 220 ◽  
pp. 241-248 ◽  
Author(s):  
Daniel Pfenniger

We review the different cold dark gas models that have been proposed in the literature, as well as a new variant which addresses their principal stability problems by taking into account the property of molecular hydrogen to become solid or liquid below 33 K and at sufficiently high pressure. This new physical ingredient provides the possibility to stabilise cold gas globules by a core of condensed molecular hydrogen. Such loosely bound cold globules behave in a galaxy as a collisionless ensemble of matter, and form a reservoir of gas easily liberated through, e.g., UV excitation. the cold condensed cores survive the longest, of order a Gyr in the solar neighbourhood radiation field, and much longer in spiral outer HI disks.


2007 ◽  
Vol 3 (S244) ◽  
pp. 17-25 ◽  
Author(s):  
E. Zackrisson ◽  
N. Bergvall ◽  
C. Flynn ◽  
G. Östlin ◽  
G. Micheva ◽  
...  

AbstractDeep optical/near-IR surface photometry of galaxies outside the Local Group have revealed faint and very red halos around objects as diverse as disk galaxies and starbursting dwarf galaxies. The colours of these structures are too extreme to be reconciled with stellar populations similar to those seen in the stellar halos of the Milky Way or M31, and alternative explanations like dust reddening, high metallicities or nebular emission are also disfavoured. A stellar population obeying an extremely bottom-heavy initial mass function (IMF), is on the other hand consistent with all available data. Because of its high mass-to-light ratio, such a population would effectively behave as baryonic dark matter and could account for some of the baryons still missing in the low-redshift Universe. Here, we give an overview of current red halo detections, alternative explanations for the origin of the red colours and ongoing searches for red halos around types of galaxies for which this phenomenon has not yet been reported. A number of potential tests of the bottom-heavy IMF hypothesis are also discussed.


1989 ◽  
Vol 346 ◽  
pp. 648 ◽  
Author(s):  
Dennis J. Hegyi ◽  
Keith A. Olive

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