CfA OIR Division Lunch Talks
Thursday, May 1, 2008, 12:30 pm, Pratt Conference Room

Mapping Mass in the Local Universe

Dr. Karen Masters (CfA)

We only see a small fraction of the matter in the universe, but the rest gives itself away by the impact of its gravity. The amount and distribution of this unseen mass provides information about the basic cosmology of the universe and helps to tell a story about how galaxies, stars and eventually planets were formed. On the largest scales galaxies seem to trace a "cosmic web". Their so-called "peculiar motions" (under the influence of gravity) have painted a picture of an underlying web of unseen mass (or "dark matter"), but previous "peculiar velocity" surveys have struggled to meet their full potential because of the large errors on individual measurements, poor statistics and uneven sky coverage. I am working on a new survey to measure the motions of thousands of galaxies and map the cosmic web with unprecedented detail. This survey makes use of both optical/near infra-red and radio observations of spiral galaxies to measure their distances and peculiar velocities. It will provide significant improvements in sky coverage especially near the obscuring plane of our Galaxy which crosses the poorly understood "great attractor" region towards which the whole local universe appears to be moving. I will give a progress report on the survey including a look at almost 400 hours of neutral hydrogen (21cm) observations from the Green Bank Telescope as well as Southern hemisphere observations with the Parkes Radio Telescope.