Dark Galaxy

Let me take a break from my homework marathon. Physicsweb and PPARC announced that a candidate for "dark galaxy" is observed. Paper is already on ArXiv astro-ph/0502312. It was first recognized in 2000 in radio astronomy hydrogen gas survey. From the size and rotation velocity, its mass seems to be about 10^8 solar mass. Subsequent observations in other wavelengths showed no sign of stars inside or nearby galaxies which can give out debris. So the most plausible explanation is a gigantic cloud almost entirely made out of dark matter! If it is not hidden by a cold dense cloud we have a very interesting object.

I was skeptical at first sight about how to generate these objects. Can dark matter clump without sucking lots of matter inside? As I went through the paper, I saw references to simulations that predict these objects. Claim is there must be more dark halos than galaxies.

If we can find a family of these objects, it will be a great challenge for any alternative gravity theories against dark matter. I can't think of any way to have such gravitation with no dark matter and almost no baryonic mass. Wouldn't it be so exciting if it turns out to be a SUSY or axion galaxy! I love astronomy; it is always full of surprises.