Letters of Intent received in 2015

LoI 2017-280
Peering towards Cosmic Dawn

Topics

(i) Cosmic Dawn: theoretical ideas and observational perspectives (e.g., HERA, SKA)
(ii) Epoch of Reionization: theory and simulations
(iii) Epoch of Reionization: first results and constraints from the redshifted 21cm experiments (e.g., EDGES, LOFAR, MWA, and PAPER)
(iv) Epoch of Reionization and the first stars/galaxies: multi-frequency approach (CMB, Ly-alpha emitters, near-infrared background, ...)
(v) Galactic foreground: polarization structures at small and large scales, constrains on interstellar medium and Galactic magnetic fields
(vi) Galactic foreground: multi-wavelenght approach (H-alpha, HI, CO, IR, dust, ...)
(vii) Extragalactic foregrounds: diffuse and extended emission - near by galaxies, radio galaxies, clusters, the cosmic web; and discrete sources: the faint source population, distant star-forming galaxies, AGN, source counts, spectral properties.
(viii) Extragalactic foregrounds: multi-wavelength approach and source evolution through cosmic time
(ix) Foreground removal techniques: CMB and EoR experiments, including the CMB B-mode polarization

Rationale

A very fundamental and yet unsolved question is when and where the first sources formed in the early Universe and began (re)ionizing the predominantly neutral all-pervasive intergalactic medium. This Epoch of Reionization (EoR), thought to occur at redshift z~6-15, is currently subject of ongoing studies using IR and radio telescopes. Whereas IR detections have been made of sources (Lyman-α emitters, quasars and drop-outs) in this redshift regime in relatively small fields of view, no direct detection of neutral hydrogen, via the redshifted 21-cm line, has yet been established. Such a direct detection is expected in the coming years, with ongoing surveys, and could open up not only the EoR, but also the preceding and very interesting Cosmic Dawn period (CD, z~15-30).

All current experiments (e.g. EDGES, LOFAR, MWA and PAPER) attempt statistical detections of the 21-cm signal during the EoR, with limited signal-to-noise. Direct imaging, except maybe on the largest (degree) scales at lower redshifts, as well as higher redshifts will remain out of reach. Future radio telescopes (e.g. HERA and SKA) will revolutionise the field, allowing direct imaging of neutral hydrogen from scales of arc-minutes to degrees over most of the relevant redshift range (z∼6-30) and, in parallel, provide enormous potential for synergy with other upcoming facilities (e.g. LSST, JWST).

In all of these experiments the cosmological 21-cm signal is, however, buried under prominent Galactic and extragalactic foregrounds that make the observations extremely challenging. The success of detection relies on our understanding of the foregrounds and development of good foreground removal techniques. This problem has common ground with the CMB studies, though the application to CD/EoR science is different in many respects. Obviously, studying the physical origin of these foregrounds, whether Galactic or extra-galactic, constitutes a very interesting and exciting field in its own right and is of fundamental importance for perfecting the removal from the observations.

The aim of this symposium is to bring together scientists interested in
the following topics: (i) Cosmic Dawn, (ii) Epoch of Reionization, (iii) Galactic foreground, (iv) extragalactic foregrounds, and (v) foreground removal techniques. All of these topics will also have a multi-wavelength component.