# What is the reason for the dispute over the variation of core mass with heavy metal abundance?

In Metal-Poor Stars IV: The Evolution of Red Giants, Rood writes

The differences in the results of these papers are large enough to introduce appreciable uncertainties into the study of the horizontal branch. For instance, there is still disagreement even as to the sign of the variation of core mass with heavy metal abundance ($dM_c/dZ$).

What is the cause of the dispute?

• Well, as a starter, your quote is referring to particular papers that are mentioned just before it. Rood's paper says that those papers came to differing results, and that one of the papers has had its methodologies questioned (but he does not specifically say they were debunked or wrong: just possibly not the right thing, but presumably in a non-obvious way). I surmise that one of the results the papers differed on was the sign of $dM_c/dZ$, and any subsequent studies have not satisfactorily resolved the disagreement. You'd have to actually look through them to be sure, I suppose. – zibadawa timmy May 26 '15 at 0:18
• I would add that this paper was written a while ago. Has a consensus been reached since? – andy256 May 26 '15 at 5:21