Limits on anisotropy in the nanohertz stochastic gravitational-wave background
- Taylor, S.
- Mingarelli, C.
- Gair, J.
- Sesana, A.
- Theureau, G.
- Babak, S.
- Bassa, C.
- Brem, P.
- Burgay, M.
- Caballero, R.
- Champion, D.
- Cognard, I.
- Desvignes, G.
- Guillemot, L.
- Hessels, J.
- Janssen, G.
- Karuppusamy, R.
- Kramer, M.
- Lassus, A.
- Lazarus, P.
- Lentati, L.
- Liu, K.
- Osłowski, S.
- Perrodin, D.
- Petiteau, A.
- Possenti, A.
- Purver, M.
- Rosado, P.
- Sanidas, S.
- Smits, R.
- Stappers, B.
- Tiburzi, C.
- Haasteren, R.
- Vecchio, A.
- Verbiest, J.
Publication date
January 2015
DOIAbstract
The paucity of observed supermassive black hole binaries (SMBHBs) may imply that the gravitational wave background (GWB) from this population is anisotropic, rendering existing analyses sub-optimal. We present the first constraints on the angular distribution of a nanohertz stochastic GWB from circular, inspiral-driven SMBHBs using the $2015$ European Pulsar Timing Array data [Desvignes et al. (in prep.)]. Our analysis of the GWB in the $\sim 2 - 90$ nHz band shows consistency with isotropy, with the strain amplitude in $l>0$ spherical harmonic multipoles $\lesssim 40\%$ of the monopole value. We expect that these more general techniques will become standard tools to probe the angular distribution of source populations
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