TY  - JOUR
KW  - ISM: abundances
KW  -  planetary nebulae: individual: SMC N2
KW  -  planetary nebulae: individual: SMC N5
KW  -  Magellanic Clouds
N1  - This version is the version of record. For information on re-use, please refer to the publisher?s terms and conditions.
IS  - 1
EP  - 181
TI  - Photoionization modelling based on HST images of Magellanic Cloud planetary nebulae ? I. SMC N 2 and SMC N 5
SN  - 0035-8711
AV  - public
JF  - Monthly Notices of the Royal Astronomical Society
PB  - BLACKWELL SCIENCE LTD
A1  - LIU, XW
A1  - BARLOW, MJ
A1  - BLADES, JC
A1  - OSMER, S
A1  - CLEGG, RES
VL  - 276
SP  - 167
N2  - We construct fully self-consistent, detailed photoionization models for two planetary nebulae (PNe) in the Small Magellanic Cloud (SMC), namely SMC N 2 and SMC N 5, to fit optical and UV spectrophotometric observations as well as HST Faint Object Camera (FOC) narrow-band images taken in the light of H?. The derived density structure shows that both PNe have a central cavity surrounded by a shell of decreasing density described by a parabolic curve. For both nebulae, our models fail to reproduce the HST images taken in the light of the [O III] ? 5007 line, in the sense that the observed [O III] ? 5007 surface brightness decreases more slowly outside the peak emission than predicted. An effective temperature of Teff = 111 500 K, a stellar surface gravity of log g = 5.45 and a luminosity of L* = 8430 L? are derived for the central star of SMC N2; similarly Teff = 137 500 K, log g = 6.0 and L* = 5850 L? are derived for SMC N 5. SMC N 2 is optically thin and has a total nebular mass (H plus He) of 0.180 M?, while SMC N 5 is optically thick and has an ionized gas mass of 0.194 M?. Using the H-burning SMC metal abundance (Z = 0.004) evolutionary tracks calculated by Vassiliadis & Wood, core masses of 0.674 M? and 0.649M? are derived for SMC N 2 and SMC N 5, respectively. Similarly, from the He-burning evolutionary tracks of Vassiliadis & Wood for progenitor stars of mean LMC heavy-element abundance (Z = 0.008), we find Mc = 0.695 and 0.675 M? for SMC N 2 and SMC N 5, respectively. We find that H? images are needed if one is to derive accurate stellar luminosities directly from photoionization modelling. However, in the absence of an H? image, photoionization models based on [O III] images (and nebular line intensities) yield accurate values of Teff and log g, which in turn allow reliable stellar masses and luminosities to be derived from a comparison with theoretical evolutionary tracks. We show that the correct nebular ionized mass can be deduced from the nebular H? flux, provided the mean nebular density given by the C III] ? 1909/? 1907 ratio is also known.
UR  - https://doi.org/10.1093/mnras/276.1.167
ID  - discovery10096146
Y1  - 1995/09//
ER  -