Download emulateapj.cls and use it instead of aastex.cls.
\documentclass{emulateapj}
or
\documentclass[onecolumn]{emulateapj}
(see header for other options)
Emulateapj uses revtex4.cls,
download it also if you don't have it already.
The user needs to use \documentclass{aastex} and then \usepackage{emulateapj5}.
Some TeX installations (e.g. teTeX) will find all the font files used by apjfonts.sty. If, however, your LaTeX/dvips complains about not finding some fonts, you will have to install them: download apjfonts.tar.gz, unpack and read INSTALL.
If you have any questions, email alexey@head-cfa.harvard.edu