Sengi: a small, fast, interactive viewer for spectral outputs from
  stellar population synthesis models
  We present Sengi, https://christopherlovell.github.io/sengi , an online tool
for viewing the spectral outputs of stellar population synthesis (SPS) codes.
Typical SPS codes require significant disk space or computing resources to
produce spectra for simple stellar populations with arbitrary parameters. This
makes it difficult to present their results in an interactive, web-friendly
format. Sengi uses Non-negative Matrix Factorisation (NMF) and bilinear
interpolation to estimate output spectra for arbitrary values of stellar age
and metallicity. The reduced disk requirements and computational expense allows
the result to be served as a client-based Javascript application. In this paper
we present the method for generating grids of spectra, fitting those grids with
NMF, bilinear interpolation across the fitted coefficients, and finally provide
estimates of the prediction and interpolation errors.
