1112.4209 (Warren A. Reid)
Warren A. Reid
The Magellanic Clouds are close enough to the Milky Way to provide an
excellent environment in which to study extragalactic PNe. Most of these PNe
are bright enough to be spectroscopically observed and spatially resolved. With
the latest high resolution detectors on today's large telescopes it is even
possible to directly observe a large number of central stars. Magellanic Cloud
(MC) PNe provide several astrophysical benefits including low overall
extinction and a good sample size covering a large range of dynamic
evolutionary timescales while the known distances provide a direct estimation
of luminosity and physical dimensions. Multi-wavelength surveys are revealing
intriguing differences between MC and Galactic PNe.
Over the past 5 years there has been a substantial increase in the number of
PNe discovered in the Large Magellanic Cloud (LMC) in particular. Deep surveys
have allowed the faint end of the luminosity function to be investigated,
finally providing a strong clue to its overall shape. In so doing, the surveys
are approaching completeness, estimated at ~80% in the LMC (~120 deg2) and ~65%
in the Small Magellanic Cloud (SMC) (~20 deg2).
The number of galaxies comprising the Local Group (LG) and its outskirts has
been growing steadily over the past 5 years and now numbers 48. Most of the 7
newly discovered galaxies are dwarf spheroidal (dSph) in structure and range
from 7.6 to 755 kpc from the Milky Way. Nonetheless, there are no published
searches for PNe in any of these galaxies to date. Apart from the LMC and Milky
Way, the number of PN discoveries has been very modest and only one additional
LG galaxy has been surveyed for PNe over the past 5 years. This paper provides
the number of Local Group PNe currently known and estimates each galaxy's total
PN population.
View original:
http://arxiv.org/abs/1112.4209
No comments:
Post a Comment