Forward modeling of galaxy kinematics in slitless spectroscopy
Résumé
Context. Slitless spectroscopy has long been considered a complicated and confused technique. Nonetheless, with the advent of Hubble Space Telescope (HST) instruments, characterized by a low sky background level and a high spatial resolution (most notably WFC3), slitless spectroscopy has become an adopted survey tool to study galaxy evolution from space.Aims. We aim to investigate its application to single-object studies to measure not only redshift and integrated spectral features, but also spatially-resolved quantities such as galaxy kinematics.Methods. We built a complete forward model to quantitatively compare actual slitless observations. This model depends on a simplified thin cold disk galaxy description - including flux-distribution, intrinsic-spectrum, and kinematic parameters - and on the instrumental signature. It is used to improve redshifts and constrain basic rotation curve parameters, meaning the plateau velocity v(0) (in km s(-1)) and the central velocity gradient w(0) (in km s(-1) arcsec(-1)).Results. The model is tested on selected observations from 3D-HST and GLASS surveys to estimate redshift and kinematic parameters on several galaxies measured with one or more roll angles.Conclusions. Our forward approach makes it possible to mitigate the self-contamination effect, a primary drawback of slitless spectroscopy, and therefore has the potential to increase precision on redshifts. In a limited sample of well-resolved spiral galaxies from HST surveys, it is possible to significantly constrain galaxy rotation curve parameters. This proof-of-concept work is promising for future large slitless spectroscopic surveys, such as Euclid and WFIRST.