# What does lowercase 'beta' mean in this graph of radio-emitting galaxies?

Correlation between the mass of the galaxies (X-axis) and the difference of their radio emissions at different radio frequencies (Y-axis). Each symbol represents an individual galaxy. The image of an example galaxy is from NASA/ESA Hubble Space Telescope T means the time for light to travel from these galaxies to us.

Credit: Fangxia An (IDIA/UWC)

From Phys.org and The Conversation,

Using the Meerkat Telescope on over 2,000 radio galaxies...

• It would help if you posted the actual url to the webpage in question.
– Rob
Aug 29, 2021 at 6:45
• Surely it's the slope of the line? Aug 29, 2021 at 7:56
• In the article, "our new study" links to this MNRAS paper. Aug 29, 2021 at 13:09
• The abstract of that paper confirms @ProfRob’s suggestion — it’s the slope of the relation. Aug 29, 2021 at 13:47

"The linear fit is performed by minimizing the $$\chi^{2}$$ and using the uncertainties of $$\alpha^{3.0GHz}_{1.3GHz}$$ as the inverse weights. The slopes of these linear fits, $$\beta$$, are given on the right-bottom corner of each panel."