Next Article in Journal
Study of Eclipsing Binaries: Light Curves & O-C Diagrams Interpretation
Previous Article in Journal
Magnetized Particle Motion in γ-Spacetime in a Magnetic Field
Open AccessArticle

Thermodynamic Constraints on the Non-Baryonic Dark Matter Gas Composing Galactic Halos

Department of Earth and Planetary Science, Washington University, St Louis, MO 63130, USA
Galaxies 2020, 8(4), 77; https://doi.org/10.3390/galaxies8040077
Received: 17 August 2020 / Revised: 2 November 2020 / Accepted: 5 November 2020 / Published: 8 November 2020
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. View Full-Text
Keywords: rotation curves; kinetic theory of gases; thermodynamic laws; inelastic collisions; blackbody radiation; non-baryonic dark matter; non-luminous matter rotation curves; kinetic theory of gases; thermodynamic laws; inelastic collisions; blackbody radiation; non-baryonic dark matter; non-luminous matter
Show Figures

Figure 1

MDPI and ACS Style

Hofmeister, A.M. Thermodynamic Constraints on the Non-Baryonic Dark Matter Gas Composing Galactic Halos. Galaxies 2020, 8, 77.

AMA Style

Hofmeister AM. Thermodynamic Constraints on the Non-Baryonic Dark Matter Gas Composing Galactic Halos. Galaxies. 2020; 8(4):77.

Chicago/Turabian Style

Hofmeister, Anne M. 2020. "Thermodynamic Constraints on the Non-Baryonic Dark Matter Gas Composing Galactic Halos" Galaxies 8, no. 4: 77.

Find Other Styles
Note that from the first issue of 2016, MDPI journals use article numbers instead of page numbers. See further details here.

Article Access Map by Country/Region

1
Search more from Scilit
 
Search
Back to TopTop