Analysis of Spatially Resolved Emission Lines in the Spectra of Distant Galaxies

Internal kinematics is rapidly becoming an important tool for understanding the nature and evolution of distant galaxies. However, the very low signal‐to‐noise ratios involved in these observations pose challenges to reduction techniques. We present a synthetic rotation curve technique to analyze spatially resolved emission lines from faint galaxies. This algorithm takes into account important variables, such as intrinsic velocity field, spatial distribution of the line‐emitting gas, telescope point‐spread function, spectrograph slit width, and instrumental profiles. Our technique makes use of the Metropolis algorithm to find the best model parameter values and their confidence intervals. This algorithm proves to be more robust in low signal‐to‐noise regimes than least‐squares fitting. The technique has been tested on a large set of rotation curve simulations and has been successfully used to analyze a sample of 22 field galaxies in the redshift range 0.25