A Hubble Space Telescope planetary camera view of giant H II regions - The Wolf-Rayet content of NGC 595 and NGC 604 in M33
1993; Institute of Physics; Volume: 105; Linguagem: Inglês
10.1086/116519
ISSN1538-3881
AutoresLaurent Drissen, A. F. J. Moffat, Michael M. Shara,
Tópico(s)Stellar, planetary, and galactic studies
ResumoWe present images of NGC 595 and NGC 604, the most massive giant H II regions in M33, obtained with the Planetary Camera aboard the Hubble Space Telescope in order to study their Wolf-Rayet (WR) population. Fourteen WR and/or Of candidates are detected in NGC 604, and eleven in NGC 595. All previously claimed "superluminous" WR stars are found to be tight (diameter <= 3 pc) stellar aggregates containing one (or sometimes more) normal WR star. As suspected from ground-based data, the WR/O number ratio is significantly higher in NGC 595 (~0.3) than in NGC 604 (0.1). Although they contribute only slightly to the total blue light, the WR stars may be major contributors to the output of mechanical power and energy into the interstellar medium in both clusters. Over the observable initial mass range M_0_~15-60M_sun_, the initial mass functions (IMFs) have similar slopes: x = 0.88+/-0.16 for NGC 604, x = 0.92+/-0.23 for NGC 595 [N(M)~M^-(x+1)^], compared to the Saltpeter value x = 1.35. These IMFs are somewhat flatter than those generally derived for massive stars in the Galaxy or the Magellanic Clouds.
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