Local law and Tracy.Widom limit for sparse sample covariance matrices

We consider spectral properties of sparse sample covariance matrices, which includes biadjacency matrices of the bipartite Erd.s.Rényi graph model. We prove a local law for the eigenvalue density up to the upper spectral edge. Under a suitable condition on the sparsity, we also prove that the limiting distribution of the rescaled, shifted extremal eigenvalues is given by the GOE Tracy.Widom law with an explicit formula on the deterministic shift of the spectral edge. For the biadjacency matrix of an Erd.s.Rényi graph with two vertex sets of comparable sizes M and N, this establishes Tracy.Widom fluctuations of the second largest eigenvalue when the connection probability p is much larger than N.2/3with a deterministic shift of order (Np).1.