Line confusion in spectroscopic surveys and its possible effects: shifts in Baryon Acoustic Oscillations position

Roman Space Telescope will survey about 17 million emission-line galaxies over a range of redshifts. Its main targets are H$\alpha$ at low redshifts and [O III] high The estimate the redshift these with single line identification. This suggests that other may be misidentified as targets. In particular, it is hard to distinguish between H$\beta$ lines two close in wavelength hence photometric information not sufficient separate them reliably. Misidentifying emitter cause shift inferred radial position galaxy by approximately 90 Mpc/h. length scale similar Baryon Acoustic Oscillation (BAO) could broaden BAO peak, possibly introduce errors determining peak position. We qualitatively describe effect this new systematic further quantify lightcone simulation galaxies.