A Cosmological Ruler as a Probe of Compensated
Description: A Cosmological Ruler as a Probe of Compensated Isocurvature Perturbations Chen Heinrich and Marcel Schmittfull Science Question: Compensated isocurvature perturbations (CIPs) are opposite fluctuations in the baryon and dark matter density
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slide1. A Cosmological Ruler as a Probe of Compensated Isocurvature Perturbations Chen Heinrich and Marcel Schmittfull Science Question: Compensated isocurvature perturbations (CIPs) are opposite fluctuations in the baryon and dark matter density in the era of the Big Bang. Can they explain the contradictory results on the expansion of the universe coming from different cosmological observations? If CIPs do exist, what is the best way to detect them?
Results: A new method is proposed for detection of CIPs – measurement of the spatial modulation of the Baryon Acoustic Oscillation scale. By measuring these modulations, a next-generation spectroscopic galaxy survey could be more sensitive to CIPs than existing results based on the Cosmic Microwave Background.
Significance: If CIPs exist, they may be able to explain some of the conflicting results on the expansion of the universe (e.g. between low-redshift galaxy surveys and supernovae). The new survey methodology could either detect the CIPs or rule them out as the source of conflict. Heinrich, C. and Schmittfull, M. (2019), Physical Review D 100, 063503
https://doi.org/10.1103/PhysRevD.100.063503
This work was supported by JPL internal funds. CIPs are difficult to observe because the gravitational effect of these opposing fluctuations cancels out. Baryon acoustic oscillations (BAOs – a standard ruler in cosmology), however, are sensitive to the CIP perturbations. The peak scale of the BAOs, about 500 million lightyears, is shifted (red dashed lines) depending on the strength of the CIPs. National Aeronautics and Space Administration
Jet Propulsion Laboratory
California Institute of Technology Reproduced with permission from the Physical Reviews, © APS<br>
slide2. National Aeronautics and Space Administration
Jet Propulsion Laboratory
California Institute of Technology Contact:
Chen Heinrich
JPL Postdoctoral Fellow
169-237, Jet Propulsion Laboratory, Pasadena, CA 91109
Chen.H.Heinrich@jpl.nasa.gov
https://orcid.org/0000-0003-0426-1948
Citation:
“BAO Modulation as a probe of compensated isocurvature perturbations”
Heinrich, C. and Schmittfull, M. (2019), Physical Review D 100, 063503
https://doi.org/10.1103/PhysRevD.100.063503
Technical Description of Figure:
Illustration showing the spatial correlation between compensated isocurvature perturbations (CIP) and baryon acoustic oscillations (BAO). As the large scale CIP perturbations vary with sky position (thick line), the BAO scale (the peak position) also varies (red dashed lines).
Scientific significance, societal relevance, and relationships to future missions:
It is unknown if CIPs exist. If so, they may be able to explain the tension between BAO and supernovae (local) measurements of H0, the expansion rate of the universe. The new survey methodology considered here could either detect the CIPs or rule them out as the source of conflict. It could also be used to test systematics in a BAO survey and to cross-check some CMB results.
A specific survey is proposed based on observations of emission-line galaxies out to redshift z=7.
Glossary:
Compensated isocurvature perturbations (CIP): opposing fluctuations in baryons and dark matter
Baryon: matter experienced in everyday life, e.g. protons
Baryon acoustic oscillations (BAO): a standard ruler in cosmology
Cosmic microwave background (CMB): remnant radiation from the early universe
Hubble constant (H0): expansion rate of the universe<br>
Results: A new method is proposed for detection of CIPs – measurement of the spatial modulation of the Baryon Acoustic Oscillation scale. By measuring these modulations, a next-generation spectroscopic galaxy survey could be more sensitive to CIPs than existing results based on the Cosmic Microwave Background.
Significance: If CIPs exist, they may be able to explain some of the conflicting results on the expansion of the universe (e.g. between low-redshift galaxy surveys and supernovae). The new survey methodology could either detect the CIPs or rule them out as the source of conflict. Heinrich, C. and Schmittfull, M. (2019), Physical Review D 100, 063503
https://doi.org/10.1103/PhysRevD.100.063503
This work was supported by JPL internal funds. CIPs are difficult to observe because the gravitational effect of these opposing fluctuations cancels out. Baryon acoustic oscillations (BAOs – a standard ruler in cosmology), however, are sensitive to the CIP perturbations. The peak scale of the BAOs, about 500 million lightyears, is shifted (red dashed lines) depending on the strength of the CIPs. National Aeronautics and Space Administration
Jet Propulsion Laboratory
California Institute of Technology Reproduced with permission from the Physical Reviews, © APS<br>
slide2. National Aeronautics and Space Administration
Jet Propulsion Laboratory
California Institute of Technology Contact:
Chen Heinrich
JPL Postdoctoral Fellow
169-237, Jet Propulsion Laboratory, Pasadena, CA 91109
Chen.H.Heinrich@jpl.nasa.gov
https://orcid.org/0000-0003-0426-1948
Citation:
“BAO Modulation as a probe of compensated isocurvature perturbations”
Heinrich, C. and Schmittfull, M. (2019), Physical Review D 100, 063503
https://doi.org/10.1103/PhysRevD.100.063503
Technical Description of Figure:
Illustration showing the spatial correlation between compensated isocurvature perturbations (CIP) and baryon acoustic oscillations (BAO). As the large scale CIP perturbations vary with sky position (thick line), the BAO scale (the peak position) also varies (red dashed lines).
Scientific significance, societal relevance, and relationships to future missions:
It is unknown if CIPs exist. If so, they may be able to explain the tension between BAO and supernovae (local) measurements of H0, the expansion rate of the universe. The new survey methodology considered here could either detect the CIPs or rule them out as the source of conflict. It could also be used to test systematics in a BAO survey and to cross-check some CMB results.
A specific survey is proposed based on observations of emission-line galaxies out to redshift z=7.
Glossary:
Compensated isocurvature perturbations (CIP): opposing fluctuations in baryons and dark matter
Baryon: matter experienced in everyday life, e.g. protons
Baryon acoustic oscillations (BAO): a standard ruler in cosmology
Cosmic microwave background (CMB): remnant radiation from the early universe
Hubble constant (H0): expansion rate of the universe<br>