CELT Science Case
CELT Science Justification
Process
• Put together a Science Working Group
– Bolte, Chuck Steidel, Andrea Ghez, Mike Brown, Judy
Cohen, Mike Jura, Richard Ellis, Wal Sargent
– Identified areas and solicited work from various
members of the UC/CIT community
– Made a presentation at a workshop in Feb 2001 and
gathered useful feedback.
– Final result is Chapter 2 of the CELT Conceptual
Design `Greenbook’
SWG Goals
• Answer questions:
– Is it worthwhile building a next generation large
telescope based on science drivers?
– What is the minimum size for `breakthrough’ capability
– Where does a 30m O/IR telescope fit into the
ALMA/NGST/multiple 8m picture
• Make the science case
• Guide conceptual design of telescope and
proposed 1st generation instruments and the site
• Emphasize capabilities, rather than specific science
projects.
– Lesson from Keck is that it is difficult to anticipate the most
exciting science areas a decade in advance.
– Developing workhorse capabilities in general areas pays large
scientific dividends.
• Anticipated Science Areas:
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The development and evolution of structure in the universe
The emergence of the first galaxies
The physics of star formation
The formation and evolution of planetary systems
Physical processes in the Solar System
The star formation and chemical evolution history of galaxies in the
local universe.
• New discovery space
Greenbook Examples
• Spectral studies of Solar System objects
• Extra-solar planets
– Extend searches to lower L/M
– Spectroscopic studies of ESP atmospheres
– Direct detection
• Star formation
• Chemical Evolution/star formation histories of
galaxies to 20Mpc
• Black hole demographics
• Evolution of galaxies and the IGM from z=1-5
Seeing-Limited Observations
• One illustrative example: Sloan Digital Sky Survey survey
at a lookback time of 10 billion years (z~2.5)
– 20 arc minute seeing limited field of view: equivalent at z=2.5 to a
3.4 degree field at the mean redshift of the SDSS– CELT is a widefield telescope for the distant universe.
– There are 50,000 galaxies (in the z=2-3.5 range) per square degree
accessible to low-resolution optical spectroscopy with CELT
(R=26.5)
– The CELT aperture allows one to use the brightest high redshift
galaxies, rather than rare quasars, as background sources that can
be used to perform tomography on the diffuse intergalactic
medium.
• Surface density of objects for which R>5000 spectra could be
obtained increases by 2 orders of magnitude
• Detailed physics, chemistry of baryonic material, relative distribution
of galaxies, diffuse hydrogen, and metals in the young universe.
Example: Baryonic Structure
at High Redshift
The 3-D Structure of the diffuse IGM can be probed using
“tomography” via multiple sightlines through the survey volume
Keck/HIRES
hydrogen
carbon
Where to next?
• Database of night-sky emission and detector
characteristics
• Develop a simulator
• Identify few key science questions and do a
detailed evaluation of 30m capability (assist
in tradeoff discussions)
• Expand the science baseline of ideas for
30m science - e.g. astrometry