Astronomy:Mass-to-light ratio
In astrophysics and physical cosmology, the mass-to-light ratio, normally designated with the Greek letter upsilon, ϒ,[1] is the quotient between the total mass of a spatial volume (typically on the scales of a galaxy or a cluster) and its luminosity.
These ratios are calculated relative to the Sun as a baseline ratio which is a constant ϒ☉ = 5133 kg/W: equal to the solar mass M☉ divided by the solar luminosity L☉, M☉/L☉. The mass-to-light ratios of galaxies and clusters are all much greater than ϒ☉ due in part to the fact that most of the matter in these objects does not reside within stars and observations suggest that a large fraction is present in the form of dark matter.[2]: 368
Luminosities are obtained from photometric observations, correcting the observed brightness of the object for the distance dimming and extinction effects. In general, unless a complete spectrum of the radiation emitted by the object is obtained, a model must be extrapolated through either power law or blackbody fits. The luminosity thus obtained is known as the bolometric luminosity.[citation needed]
Masses are often calculated from the dynamics of the virialized system or from gravitational lensing. Masses can also be measured through CMB backlighting.[3] Typical mass-to-light ratios for galaxies range from 2 to 10 ϒ☉ while on the largest scales, the mass to light ratio of the observable universe is approximately 100 ϒ☉, in concordance with the current best fit cosmological model.[citation needed]
Mass-to-light ratios in application can be used to gain insight into the dark matter content and dust extinction in a galaxy.[4] Historically, rotation curves for spiral galaxies have been used to study galaxies, but mass-to-light ratios prove more accurate as a method of measuring mass.[5]
See also
References
- ↑ Mihalas, Dimitri; Routly, Paul McRae (1968). Galactic Astronomy. W. H. Freeman. p. 257. ISBN 978-0-7167-0326-6.
- ↑ Peacock, J. A. (1998-12-28). Cosmological Physics (1 ed.). Cambridge University Press. doi:10.1017/cbo9780511804533. ISBN 978-0-521-41072-4. https://www.cambridge.org/core/product/identifier/9780511804533/type/book.
- ↑ "New analyses shine light on dark matter and intergalactic mass in unprecedented detail – Physical Sciences Area" (in en-US). https://physicalsciences.lbl.gov/2025/02/11/new-analyses-shine-light-on-dark-matter-and-intergalactic-mass-in-unprecedented-detail/.
- ↑ Astrobites (2020-11-25). "UR #33: Investigating the dark matter in M82 using the mass-to-light ratio" (in en-US). https://astrobites.org/2020/11/25/ur-m82-dark-matter-mass-to-light-ratio/.
- ↑ Faber, S. M.; Gallagher, J. S. (1979). "Masses and Mass-To-Light Ratios of Galaxies" (in en). Annual Review of Astronomy and Astrophysics 17: 135–187. doi:10.1146/annurev.aa.17.090179.001031. ISSN 0066-4146. Bibcode: 1979ARA&A..17..135F.
External links
- Merrifield, Michael (2009). "ϒ – Mass to Light Ratio". Sixty Symbols. Brady Haran for the University of Nottingham. http://www.sixtysymbols.com/videos/masstolight.htm.
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