A survey of the Wolf-Rayet population of the barred, spiral galaxy NGC1313⋆

We present a VLT/FORS1 survey of Wolf-Rayet (WR) stars in the spiral galaxy NGC1313. In total, 94 WR candidate sources have been identified from narrow-band imaging. Of these, 82 have been spectroscopically observed, for which WR emission features are confirmed in 70 cases, one of which also exhibits strong nebular He ii λ4686 emission. We also detect strong nebular He ii λ4686 emission within two other regions of NGC 1313, one of which is a possible supernova remnant. Nebular properties confirm that NGC1313 has a metal-content log(O/H)+12=8.23±0.06, in good agreement with previous studies. From continuum subtracted Hα images we infer a global star formation rate of 0.6M⊙yr . Using template LMC WR stars, spectroscopy reveals that NGC1313 hosts a minimum of 84 WR stars. Our census comprises 51 WN stars, including a rare WN/C transition star plus 32 WC stars. In addition, we identify one WO star which represents the first such case identified beyond the Local Group. The bright giant H ii region PES 1, comparable in Hα luminosity to NGC595 in M33, is found to host a minimum of 17 WR stars. The remaining photometric candidates generally display photometric properties consistent with WN stars, such that we expect a global WR population of ∼115 stars with N(WR)/N(WO)∼0.01 and N(WC)/N(WN)∼0.4.