Intensity Mapping: A New Window into
the Cosmos
Hamsa Padmanabhan
Abstract The technique of intensity mapping (IM) has emerged as a powerful
tool to explore the universe at z < 6. IM measures the integrated emission from
sources over a broad range of frequencies, unlocking significantly more information
than traditional galaxy surveys. Astrophysical uncertainties, however, constitute an
important systematic in our attempts to constrain cosmology with IM. I describe
an innovative approach which allows us to fully utilize our current knowledge of
astrophysics in order to develop cosmological forecasts from IM. This framework
can be used to exploit synergies with other complementary surveys, thereby opening
up the fascinating possibility of constraining physics beyond ΛCDM from future IM
observations.
Keywords Intensity mapping · Cosmology · Large-scale structure
1 Introduction
Intensity mapping (IM) has emerged as a novel, powerful probe of cosmology
over the last decade (e.g., [4]). In this technique, the aggregate intensity of
spectral line emission is mapped out to probe the underlying large-scale structure,
without resolving individual systems. This offers a three-dimensional picture of the
formation and growth of baryonic material (primarily neutral hydrogen—HI), with
the frequency dependence tracing their redshift evolution. In contrast to traditional
galaxy surveys, which reach their sensitivity limits at z ∼ 2, probing only about
a few percent [6] of the comoving volume of the observable universe, IM has the
Invited talk at the ‘Quantum Theory and Symmetries’ (QTS-XI) conference, Montreal, QC,
Canada, July 2019.
H. Padmanabhan ()
Canadian Institute for Theoretical Astrophysics, Toronto, ON, Canada
e-mail: hamsa@cita.utoronto.ca
© Springer Nature Switzerland AG 2021
M. B. Paranjape et al. (eds.), Quantum Theory and Symmetries, CRM Series in
Mathematical Physics, https://doi.org/10.1007/978-3-030-55777-5_42
457
the Cosmos
Hamsa Padmanabhan
Abstract The technique of intensity mapping (IM) has emerged as a powerful
tool to explore the universe at z < 6. IM measures the integrated emission from
sources over a broad range of frequencies, unlocking significantly more information
than traditional galaxy surveys. Astrophysical uncertainties, however, constitute an
important systematic in our attempts to constrain cosmology with IM. I describe
an innovative approach which allows us to fully utilize our current knowledge of
astrophysics in order to develop cosmological forecasts from IM. This framework
can be used to exploit synergies with other complementary surveys, thereby opening
up the fascinating possibility of constraining physics beyond ΛCDM from future IM
observations.
Keywords Intensity mapping · Cosmology · Large-scale structure
1 Introduction
Intensity mapping (IM) has emerged as a novel, powerful probe of cosmology
over the last decade (e.g., [4]). In this technique, the aggregate intensity of
spectral line emission is mapped out to probe the underlying large-scale structure,
without resolving individual systems. This offers a three-dimensional picture of the
formation and growth of baryonic material (primarily neutral hydrogen—HI), with
the frequency dependence tracing their redshift evolution. In contrast to traditional
galaxy surveys, which reach their sensitivity limits at z ∼ 2, probing only about
a few percent [6] of the comoving volume of the observable universe, IM has the
Invited talk at the ‘Quantum Theory and Symmetries’ (QTS-XI) conference, Montreal, QC,
Canada, July 2019.
H. Padmanabhan ()
Canadian Institute for Theoretical Astrophysics, Toronto, ON, Canada
e-mail: hamsa@cita.utoronto.ca
© Springer Nature Switzerland AG 2021
M. B. Paranjape et al. (eds.), Quantum Theory and Symmetries, CRM Series in
Mathematical Physics, https://doi.org/10.1007/978-3-030-55777-5_42
457