107 research outputs found
Prospects for 21cm-Galaxy Cross-Correlations with HERA and the Roman High-Latitude Survey
The cross-correlation between the 21 cm field and the galaxy distribution is
a potential probe of the Epoch of Reionization (EoR). The 21 cm signal traces
neutral gas in the intergalactic medium and, on large spatial scales, this
should be anti-correlated with the high-redshift galaxy distribution which
partly sources and tracks the ionized gas. In the near future, interferometers
such as the Hydrogen Epoch of Reionization Array (HERA) are projected to
provide extremely sensitive measurements of the 21 cm power spectrum. At the
same time, the Nancy Grace Roman Space Telescope (Roman) will produce the most
extensive catalog to date of bright galaxies from the EoR. Using semi-numeric
simulations of reionization, we explore the prospects for measuring the
cross-power spectrum between the 21 cm and galaxy fields during the EoR. We
forecast a 14 detection between HERA and Roman, assuming an overlapping
survey area of 500 deg, redshift uncertainties of (as
expected for the high-latitude spectroscopic survey of Ly-emitting
galaxies), and an effective Ly emitter duty cycle of . Thus the HERA-Roman cross-power spectrum may be used to help verify 21 cm
detections from HERA. We find that the shot-noise in the galaxy distribution is
a limiting factor for detection, and so supplemental observations using Roman
should prioritize deeper observations, rather than covering a wider field of
view.Comment: 26 pages, 15 figures, accepted at Ap
Probing helium reionization with kinetic Sunyaev Zel'dovich tomography
Reionization of helium is expected to occur at redshifts and have
important consequences for quasar populations, galaxy formation, and the
morphology of the intergalactic medium, but there is little known empirically
about the process. Here we show that kinetic Sunyaev-Zeldovich (kSZ)
tomography, based on the combination of CMB measurements and galaxy surveys,
can be used to infer the primordial helium abundance as well as the time and
duration of helium reionization. We find a high-significance detection at
can be expected from Vera Rubin Observatory and CMB-S4 in the
near future. A more robust characterization of helium reionization will require
next-generation experiments like MegaMapper (a proposed successor to DESI) and
CMB-HD.Comment: 4+2 pages, 2 figures, comments welcom
Mapping Cosmic Dawn and Reionization: Challenges and Synergies
Cosmic dawn and the Epoch of Reionization (EoR) are among the least explored
observational eras in cosmology: a time at which the first galaxies and
supermassive black holes formed and reionized the cold, neutral Universe of the
post-recombination era. With current instruments, only a handful of the
brightest galaxies and quasars from that time are detectable as individual
objects, due to their extreme distances. Fortunately, a multitude of
multi-wavelength intensity mapping measurements, ranging from the redshifted 21
cm background in the radio to the unresolved X-ray background, contain a
plethora of synergistic information about this elusive era. The coming decade
will likely see direct detections of inhomogenous reionization with CMB and 21
cm observations, and a slew of other probes covering overlapping areas and
complementary physical processes will provide crucial additional information
and cross-validation. To maximize scientific discovery and return on
investment, coordinated survey planning and joint data analysis should be a
high priority, closely coupled to computational models and theoretical
predictions.Comment: 5 pages, 1 figure, submitted to the Astro2020 Decadal Survey Science
White Paper cal
Cosmology with the Highly Redshifted 21cm Line
In addition to being a probe of Cosmic Dawn and Epoch of Reionization
astrophysics, the 21cm line at is also a powerful way to constrain
cosmology. Its power derives from several unique capabilities. First, the 21cm
line is sensitive to energy injections into the intergalactic medium at high
redshifts. It also increases the number of measurable modes compared to
existing cosmological probes by orders of magnitude. Many of these modes are on
smaller scales than are accessible via the CMB, and moreover have the advantage
of being firmly in the linear regime (making them easy to model theoretically).
Finally, the 21cm line provides access to redshifts prior to the formation of
luminous objects. Together, these features of 21cm cosmology at provide
multiple pathways toward precise cosmological constraints. These include the
"marginalizing out" of astrophysical effects, the utilization of redshift space
distortions, the breaking of CMB degeneracies, the identification of signatures
of relative velocities between baryons and dark matter, and the discovery of
unexpected signs of physics beyond the CDM paradigm at high redshifts.Comment: Science white paper submitted to Decadal 2020 surve
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