M33 with LAMOST survey sp. I. PNe & HII regions

Physical parameters; extinction; chemical composition of He, N, O, Ne, S, Cl, and Ar (where available); and radial velocities were determined for 110 nebulae (95 HII regions and 15 planetary nebulae) in M33. Among them, 8 planetary nebulae and 55 HII regions in M33 are newly discovered.

We obtained the following O abundance gradients: -0.199_-0.030_^+0.030^dex R_25_^-1^ (based on 95 HII regions), -0.124_-0.036_^+0.036^dex R_25_^-1^ (based on 93 HII regions), and -0.207_-0.174_^+0.160^dex R_25_^-1^ (based on 21 HII regions), utilizing abundances from N2 at O3N2 diagnostics and the Te-sensitive method, respectively. The He, N, Ne, S, and Ar gradients resulted in slopes of -0.179_-0.146_^+0.145^, -0.431_-0.281_^+0.282^, -0.171_-0.239_^+0.234^, -0.417_-0.182_^+0.174^, and -0.340_-0.157_^+0.156^, respectively, utilizing abundances from the Te-sensitive method.