Unwanted CM fonts when trying to use mathpazo

Question

Some more information. In making an MWE I removed a lot of stuff, including the use of XeLaTeX or LuaLaTeX, and fontspec. What I was actually trying to do was set up a suitable maths font environment to accompany Minion Pro. In seeking an MWE (took me most of the afternoon, snort), I have reporduced this behaviour with fontspec, and under all three engines (PDFTeX, LuaTeX, and XeTeX).

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Original Question:

I'm trying to use mathpazo in a document. I may have a separate problem with fontspec, but I'll leave that to another question.

Here's my MWE:

\documentclass{article}
\usepackage{mathpazo}
\usepackage{tgpagella}
\begin{document}

When traffic is normal, the probability $P_2$ 
that this second message is waiting depends on two factors: 
the message arrival rate $\lambda$ 
and the trigger processing time $t_T$; 
its approximate value is given by

%\[ P_2  = 1-e^{- \lambda t_T} \]  % Uncomment this!

\end{document}

When I process this with the display-math line commented out, I get a reasonable PDF with 4 fonts embedded (PazoMath-Italic, TeXGyrePagella-Regular, URWPalladioL-Ital and -Roma), which seems reasonable.

However, when I uncomment the display-math line, my PDF now shows two more fonts: CMR10 and CMSY10. Inspecting the output, I can't see any difference in the glyphs.

What's going on here? And, if it needs fixing, how should I fix it?

Answer 1

mathpazo uses a virtual font that includes some CM symbols to make up the math character set. So seeing cm in the final output if you use mathematics is to be expected.

The easiest way to see which characters come from which font is to look at the fontinst source, http://mirrors.ctan.org/fonts/mathpazo/pazofnst/pazofnst.tex