X-Y plot from article

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...

  • $\begingroup$ It would help if you posted the actual url to the webpage in question. $\endgroup$
    – Rob
    Aug 29, 2021 at 6:45
  • 2
    $\begingroup$ Surely it's the slope of the line? $\endgroup$
    – ProfRob
    Aug 29, 2021 at 7:56
  • 1
    $\begingroup$ In the article, "our new study" links to this MNRAS paper. $\endgroup$
    – Mike G
    Aug 29, 2021 at 13:09
  • $\begingroup$ The abstract of that paper confirms @ProfRob’s suggestion — it’s the slope of the relation. $\endgroup$ Aug 29, 2021 at 13:47

1 Answer 1


This is an answer that I am writing up based on comments by ProfRob and Mike G.

The meaning of 'beta' in these plots is the slope of the line. The figure itself is from Radio spectral properties of star-forming galaxies in the MIGHTEE-COSMOS field and their impact on the far-infrared-radio correlation (arXiv link).

From the caption of the figure in the above question:

"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."

  • $\begingroup$ Which for me, raises another question: what's the point of performing a linear fit, when there's no clear correlation between the x and y variables? What am I missing? $\endgroup$
    – Jim421616
    Jan 2, 2022 at 17:18

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