Kavli Affiliate: George Efstathiou
| First 5 Authors: Jiten Dhandha, Jiten Dhandha, , ,
| Summary:
The cosmic 21-cm signal is a promising probe of the early Universe, owing to
its sensitivity to the thermal state of the neutral intergalactic medium (IGM)
and properties of the first luminous sources. In this work, we constrain the
21-cm signal and infer IGM properties by leveraging multi-wavelength synergies.
This builds on our earlier study, where we developed the synergy between
high-redshift UV luminosity functions (UVLFs), cosmic X-ray and radio
backgrounds (CXB and CRB), 21-cm global signal non-detection from SARAS~3, and
21-cm power spectrum upper limits from HERA, to constrain the astrophysical
properties of Population II galaxies. Through a combination of CXB and HERA
data, we find the IGM kinetic temperature to be $T_textK(z=15)lesssim
7.7~textK$, $2.5~textK lesssim T_textK(z=10) lesssim 66~textK$,
and $20~textKlesssim T_textK(z=6) lesssim 2078~textK$ at 95%
credible interval (C.I.). Similarly, CRB and HERA data place an upper limit on
the radio emission efficiency of galaxies, giving $T_textrad(z=15) lesssim
47~textK$, $T_textrad(z=10)lesssim 51~textK$, and
$T_textrad(z=6)lesssim 101~textK$. These constraints, strengthened by
the inclusion of UVLFs from HST and JWST, allow us to place the first
textitlower bound on the cosmic 21-cm signal. We infer an absorption trough
of depth $-201~textmKlesssim T_text21,min lesssim -68~textmK$ at
$z_textminapprox10-16$, and a power spectrum of $8.7~textmK^2 <
Delta_21^2(z=15) < 197~textmK^2$ at $k=0.35~htextMpc^-1$. Our
results provide promising predictions for upcoming 21-cm experiments, and
highlight the power of multi-wavelength synergies in constraining the early
Universe.
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