SKA-Low Intensity Mapping Pathfinder Updates: Deeper 21 cm Power
  Spectrum Limits from Improved Analysis Frameworks
  The Square Kilometre Array (SKA) is a planned radio interferometer of
unprecedented scale that will revolutionize low-frequency radio astronomy when
completed. In particular, one of its core science drivers is the systematic
mapping of the Cosmic Dawn and Epoch of Reionization, which mark the birth of
the first stars and galaxies in the Universe and their subsequent ionization of
primordial intergalactic hydrogen, respectively. The SKA will offer the most
sensitive view of these poorly understood epochs using the redshifted 21 cm
hyperfine signal from intergalactic hydrogen. However, significant technical
challenges stand in the way of realizing this scientific promise. These mainly
involve the mitigation of systematics coming from astrophysical foregrounds,
terrestrial radio interference, and the instrumental response. The Low
Frequency Array, the Murchison Widefield Array and the Hydrogen Epoch of
Reionization Array are SKA pathfinder experiments that have developed a variety
of strategies for addressing these challenges, each with unique characteristics
that stem largely from their different instrumental designs. We outline these
various directions, highlighting key differences and synergies, and discuss how
these relate to the future of low-frequency intensity mapping with the SKA. We
also briefly summarize the challenges associated with modeling the 21 cm signal
and discuss the methodologies being proposed for inferring constraints on
astrophysical models.
