GalevNB: a conversion from N-BODY simulations to observations

Abstract

We present $GalevNB$ (Galev for $N$-body simulations), an utility that converts fundamental stellar properties of $N$-body simulations into observational properties using the $GALEV$ (GAlaxy EVolutionary synthesis models) package, and thus allowing direct comparisons between observations and $N$-body simulations. It works by converting fundamental stellar properties, such as stellar mass, temperature, luminosity and metallicity into observational magnitudes for a variety of filters of mainstream instruments/telescopes, such as HST, ESO, SDSS, 2MASS, etc.), and into spectra that spans from far-UV (90 $\rm \AA$) to near-IR (160 $\rm \mu$m). As an application, we use $GalevNB$ to investigate the secular evolution of spectral energy distribution (SED) and color-magnitude diagram (CMD) of a simulated star cluster over a few hundred million years. With the results given by $GalevNB$ we discover an UV-excess in the SED of the cluster over the whole simulation time. We also identify four candidates that contribute to the FUV peak, core helium burning stars, thermal pulsing asymptotic giant branch (TPAGB) stars, white dwarfs and naked helium stars.