Spike Hunting in Galaxy Spectra

In this paper we summarize analysis of galaxy spectra from the Sloan Digital Sky Survey. To each spectrum we fit non-parametrically a continuum, that is a smooth underlying trend, and a parametric ``island'' of spike profiles at each group (opportunely defined) of adjacent absorption or emission line locations, having, as ultimate inferential goal, the construction of reliable confidence intervals for the signed areas between each spike and the continuum. The implemented semi-parametric estimation procedure based on sieved penalized splines, has proved to be effective, computationally efficient and easy to implement.