Space Warps Talk

Dark Matter

  • Chinabob by Chinabob

    Could concentrated areas of Dark Matter cause a lenz?

    Just a thought bubble.


  • Capella05 by Capella05 moderator

    Hi Chinabob,

    Interesting question, one of the reasons we look for gravitational lenses is so we can calculate the mass of a galaxy (and therefore try to work out the mass of the dark matter). I have not heard of dark matter alone, causing lensing.

    Have a look at this somewhat related thread - more about black holes and lensing, but it does raise some fascinating points.

    Will get one of the scientists to pop by and give a more substantial answer.


  • Tom_Collett by Tom_Collett scientist

    HI Chinabob.

    Nice question.

    A dense 'blob' (we call them halos) of dark matter could cause lensing. Lensing doesn't care if the mass is dark matter or normal. However, there are two reasons to suspect that we wont see lensing by dark matter only.

    1. Dark matter and normal matter trace each other - all massive dark matter halos host galaxies that we can see. Small clumps (millions of times the mass of the sun, compared to the Milky Way dark matter which lives in a halo of approximately 10^12 solar masses), don't seem to have galaxies in them but these halos are too small to have a significant lensing effect

    2. For arcs or multiple images to form requires a gravitational lens that is above a critical density. But, in simulations of the Universe that don't have any normal matter the dark matter halos don't get very dense. The most massive halos would get dense enough, but these are rare (and should definitely have galaxies at the centre of them)

    Hope this helps.


  • Chinabob by Chinabob

    Thanks for the comments. what I like about the zoo is when you look deeper into 'things' the more interesting it gets and for me the more exciting.