Wednesday, September 26, 2012

Surfing the High-Redshift Universe in Santa Cruz

I was waiting all week long for the last day of the CANDELS team meeting, not to go home, but because on that day we finally had the high-redshift sessions!  We had two sessions devoted wholly to high-redshift science, split with some science talks, and some discussion sessions.  My primary goal for these sessions was to get our group to work together - we have high-redshift experts in CANDELS spread not only throughout the US, but around the world, with large groups in Edinburgh and Rome.  Each of these groups sent representatives to Santa Cruz, so it was a great opportunity for the team to catch up on the goings on around the high-redshift team.

We also got updates on some of the papers in progress.  One of the most interesting results came from Vithal Tilvi, who is a postdoc at my old stomping grounds, Texas A&M.  He has been combining CANDELS data with some ground-based medium-band images (meaning he's using some filters narrower than those we've been using on HST to isolate specific wavelengths).  His primary goal was to find distant galaxies.  But in an ironic twist, he thinks he might have found an extremely nearby object; a very low-mass star known as a Y-dwarf (these are so small they are not undergoing any fusion, and thus are known as brown dwarfs, and this particular flavor of brown dwarfs are barely larger than Jupiter).  Brown dwarfs have colors similar to high-redshift galaxies, thus they can hide in our samples.  Typically they're thought of as contaminants, but this particular type of star is rare, so its more like a diamond in the rough!  We also heard some updates by Giovanni Fazio on the status of his deep Spitzer Space Telescope program which is imaging the CANDELS field in the infrared, and I updated the team on my ongoing work measuring the luminosity functions of distant galaxies (which is a measure of the distribution of galaxy brightnesses).
An image of the field with the Y-dwarf, with the box highlighting the brown dwarf.  The inset shows an image of a Jupiter-like planet, which likely doesn't look much different from this brown dwarf.

We had some interesting discussion sessions as well.  We made a lot of progress on a project we're doing to create a catalog of "CANDELS-approved" very distant galaxies.  We also discussed how best to proceed with measuring galaxy clustering, which is a highly interesting yet extremely difficult way to measure the cosmic structure from the positions of galaxies.  And we had a great session where we interfaced with our fantastic theory group, working with them to identify the key problems we should be focussing on.  So now its back to work for all of us, but it won't be too long until we get together again - we're planning for our next high-redshift meeting to be in the scenic city of Sesto, Italy in January.  Sesto is like the Aspen of Italy, so don't forget your snow pants!

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