Description
0.1 Activity 09
The file Galaxy_Sample_Logistic.csv in the repository includes the following columns for a large
sample of galaxies:
Morph : morphological classification (1= elliptical, 0= everything else)
Density : Log of the environmental density (proportional to the surface density of
galaxies around each object)
Absolute : the r band absolute magnitude of an object (remember magnitudes are
defined as -2.5log Luminosity)
Using the programming language of your choice:
Visualize and explore the data, discuss if the correlations you see make sense, given what you have
learned in class. Using the best practice for Bayesian analysis, model the probability 𝜃 of a galaxy
being an elliptical as a function of its environmental density and absolute magnitude.
Compute the 95% credibility interval on 𝜃, in the case of low and high density environments, and
for bright and faint galaxies. [You will have to decide what high/low, faint/bright mean here. Make
sure you ae quantitative and motivate your choice].
Discuss which variable dominates in determining whether or not a galaxy has an elliptical morphology.
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