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Gravitational-wave limits from pulsar timing constrain supermassive black hole evolution
R M Shannon1, V Ravi, W A Coles
1Commonwealth Scientific and Industrial Research Organisation (CSIRO) Astronomy and Space Science, Australia Telescope National Facility, Post Office Box 76, Epping, New South Wales 1710, Australia.
Science (New York, N.Y.)
|October 19, 2013
Summary
New gravitational-wave background limits from pulsar timing arrays challenge supermassive black hole population models. These findings suggest current models may not accurately describe how these cosmic giants form and grow.
Area of Science:
- Astrophysics
- Cosmology
- Gravitational Wave Astronomy
Background:
- Supermassive black hole (SMBH) formation and growth mechanisms remain poorly understood.
- SMBH population models predict the characteristics of the gravitational-wave background (GWB) from merging binary SMBHs.
Purpose of the Study:
- To constrain the fractional GWB energy density using observational data.
- To test the predictions of SMBH population models against new observational limits.
Main Methods:
- Utilized data from the Parkes Pulsar Timing Array.
- Calculated a 95% confidence upper limit on the fractional GWB energy density (Ω(GW)) at 2.8 nanohertz.
Main Results:
- Established a new upper limit: Ω(GW)(H0/73 km/s/Mpc)² < 1.3 × 10⁻⁹.
- This limit is approximately six times more stringent than previous constraints.
- Identified inconsistencies between the derived limit and several SMBH population models, including the Millennium Simulation.
Conclusions:
- The new GWB constraints provide significant challenges to existing SMBH population models.
- Further refinement of galaxy formation and SMBH growth theories is necessary to align with observational data.
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