You have to be more patient. It takes about 1.5 minutes to just read the eps file on my IM 6.7.5.7 Q16 Mac OSX Snow Leopard (INTEL dual core with 4GB RAM)
If I simplify your processing the following works.
time convert -colorspace rgb -density
72 2011jd016761-p04.eps -background white -flatten 2011jd016761-p04.png
real 1m30.013s
user 1m29.035s
sys 0m0.242s
Note +repage after the -trim is not needed for jpg, though does not hurt
For larger density values, it will take longer to process assuming you have enough memory. If not, then try memory management such as at
http://www.imagemagick.org/Usage/files/#massive
One other problem is that your eps file when converted has a large amount of white space at the top that is several times the height of the image data. So you probably want to use -trim to cut out all the excess white space.
time convert -colorspace rgb -density
72 2011jd016761-p04.eps -background white -flatten -fuzz 10% -trim 2011jd016761-p04.png
real
1m27.525s
user 1m27.145s
sys 0m0.184s
time convert -colorspace rgb -density
150 2011jd016761-p04.eps -background white -flatten -fuzz 10% -trim 2011jd016761-p04.png
real
9m27.575s
user 9m24.320s
sys 0m0.673s
So it really slows down as I double the density (which would quadruple the area).