Observing Kinematic Anisotropies of the Stochastic Background with LISA

17.05.2024 11:50 – 12:50

Next-generation gravitational wave detectors hold the capability to track unresolved gravitational waves bundled into a stochastic background. This composite background contains cosmological and astrophysical contributions, the exploration of which offers promising avenues for groundbreaking new insights into very early universe cosmology as well as late-time structure formation. However, such signatures will be entangled and mixed with instrumental noise & artefacts, making a robust component separation a particularly challenging task, and the object of an intense research effort from the community. A promising diagnostic tool for identifying the origin of SGWB signals bases on exploiting kinematic anisotropies, that is, the deformations of the SGWB angular distribution induced by the observer motion w.r.t. CMB rest frame. Detection by LISA of such Doppler modulation may act as a smoking-gun for the extragalactic origin of an observed SGWB. Verifying consistency between CMB and SGWB rest frame is also of great interest, in the current context of a vivid tension with galaxy count anisotropy expectations.

In this presentation, I will discuss the capability of LISA to resolve motion-induced SGWB dipole & quadrupole, and present data analysis techniques proposed to that end. I will discuss the results of our recent publication [arXiv:2401.14849], which expose, for the first time, a full end-to-end pipeline developed and applied for the extraction of extra-galactic signals, based on kinematic anisotropies arising from the galactic motion w.r.t. SGWB rest frame. It uses a full-time-domain simulations of LISA response to the gravitational wave anisotropic sky, and employs a Markov-Chain-Monte-Carlo map-making scheme, able to extract multipoles up to l=2 and resolve the our motion w.r.t. SGWB frame in a signal-dominated regime, providing a practical diagnostics tool for such a scenario. The impact of instrumental noise on the extraction of kinematic anisotropies will then be investigated. Finally, we will discuss how, for a large variety of SGWB sources, distinctive features shown by the SGWB energy density spectra in LISA band (slope breaks, maxima, peaks), as is particularly the case for backgrounds spectrum associated to Primordial Black Holes (PBH) formation and populations, can significantly enhance the kinematic dipoles and quadrupoles. Hence making this diagnostic tool even more promising in the hunt for cosmological signatures in LISA data.

Lieu

Bâtiment: Ecole de Physique

EP234

entrée libre