Download Interpretation and prospects 21 cm Intensity mapping with the Green Bank Telescope:

21 cm Intensity mapping with
the Green Bank Telescope:
Interpretation and
prospects
Kiyoshi Masui
E. Switzer, K. Bandura, L.-M. Calin, T.C. Chang,X.-L. Chen, Y.-C. Li, Y.-W.
Liao, A. Natarajan, U.-L. Pen, J. B.
Peterson, J. R. Shaw, T. C. Voytek
Columbus, Ohio
April 19, 2013
How do we interpret the cross-power and auto-power
measurements?
We have bounded the signal from
above and below!
Pursue a Bayesian analysis to obtain a
combined constraint:
Pursue a Bayesian analysis to obtain a
combined constraint:
More parameters than we have measurements, but
that's okay because of priors (constraints) on nuisance
parameters.
Pursue a Bayesian analysis to obtain a
combined constraint:
Do the usual: write down priors, apply Bayes' Theorem,
marginalize nuisance parameters.
Pursue a Bayesian analysis to obtain a
combined constraint:
68% and 95% confidence intervals for each k-bin.
In context:
Noterdaeme 2012
HI is fuel for star formation, evolution and
clustering is important clue for galaxies.
In context:
if 0.65 < bHI < 1,
but really bHI = ?
Could break degeneracy
using Kaiser effect
Noterdaeme 2012
HI is fuel for star formation, evolution and
clustering is important clue for galaxies.
Challenges
Instrumental Considerations
Wideband gain stability
Estimating foreground
modes with sufficient
fidelity to remove them
Polarized beam response
Foregrounds are estimated from the map.
How much information does the map have
about the foregrounds?
256 spectral channels, so even 100 modes is
okay?
Actually limited by angular DOF
Only 30 (90) independent pixels
We would like 10 times more area
Foregrounds only smooth in Stokes I, if beam is
smooth
Polarization leakage mixes in Q, U
Improve things by smoothing
Calibrate it out...
Future Prospects
More Area
Have lots of angular DOF ~ 1000
Smooth out beam effects
Have more signal-to-noise to work with
Brightness fluctuation
Mean HI density and bias are
degenerate
Can be broken with Kaiser
redshift space distortions
Reid, BOSS 2012
See Masui et. al. 2010
WiggleZ is a BAO survey
High density, large area, large scales
VIPERS is smaller area
MUCH higher galaxy density
Good survey to go after Kaiser in cross-correlation
GBT Multibeam, Parkes
Have some Parkes L-band multibeam data,
working on it
GBT multibeam prototype testing this summer