Dynamics of tachyon dark energy on large scales and its imprint on observed galaxy power spectrum

Abstract: In the present work, we study the large scale matter power spectrum as well as the observed galaxy power spectrum for non-canonical tachyon field dark energy model considering the full general relativistic perturbation equations. We form a set of coupled autonomous equations including both the background and linearly perturbed quantities and obtain their solutions numerically with proper set of initial conditions. We consider different scalar field potentials for our study. Deviations from concordance $\Lambda$CDM model are studied for different relevant quantities. Our study shows that non-canonical tachyon dark energy model produces enhanced gravitational potentials, comoving density contrast as well as linear growth factor for matter perturbations compared to $\Lambda$CDM. It is also observed that for tachyon dark energy models, there is suppression of power on large scales compared to both $\Lambda$CDM model as well as previously studied canonical scalar field models.