Research Gallery > Cosmology
|The GMRT Epoch of Reionization experiment: a new upper limit on the neutral hydrogen power spectrum at z ≈ 8.6
Image Credit: Paciga and Chang et al.
Average power spectrum in units of K
of all combinations of
days, excluding December 11, as a function of the multipole moment l. Each
point is shown with a 2σ upper limit derived from a bootstrap error analysis,
which is in most cases smaller than the size of the point. The points are
logarithmically spaced as described in the text, from left to right covering
the ranges 377 < l < 578, 578 < l < 899 and 899 < l < 1414. Triangles are
the power before subtracting foregrounds, diamonds are after 8 MHz mean
subtraction, squares are after 2 MHz mean subtraction and circles are after
0.5 MHz subtraction. The curved solid line is the theoretical EoR signal
from Jelic et al. (2008), and the dashed line is the theoretical EoR signal ´
with a cold absorbing IGM as described in the text.
|For epoch of reionization (EoR), we have been utilizing the the
Giant Metrewave Radio Telescope (GMRT) in India to measure the 21-cm power spectrum at redshifts 8
< z < 9, constraining the fluctuation of ionization. We have put a first upper limit on the amplitude of the
power spectrum at a mean redshift of 8.5 (Paciga et al. 2011), as shown in figure below. The upper limit
is within one order-of-magnitude of the currently popular theoretical expectations, and already rules out
models where the intergalactic medium was not heated before reionization.