272 research outputs found
A Survey for Planetary Nebulae in M31 Globular Clusters
We report the results of an [O III] 5007 spectroscopic survey for planetary
nebulae (PNe) located within the star clusters of M31. By examining R ~ 5000
spectra taken with the WIYN+Hydra spectrograph, we identify 3 PN candidates in
a sample of 274 likely globular clusters, 2 candidates in objects which may be
globular clusters, and 5 candidates in a set of 85 younger systems. The
possible PNe are all faint, between ~2.5 and ~6.8 mag down the PN luminosity
function, and, partly as a consequence of our selection criteria, have high
excitation, with [O III] 5007 to H-beta ratios ranging from 2 to ~12. We
discuss the individual candidates, their likelihood of cluster membership, and
the possibility that they were formed via binary interactions within the
clusters. Our data are consistent with the suggestion that PN formation within
globular clusters correlates with binary encounter frequency, though, due to
the small numbers and large uncertainties in the candidate list, this study
does not provide sufficient evidence to confirm the hypothesis.Comment: Accepted for publication in the Astrophysical Journal. 54 pages,
including 9 figures and 4 table
The Circumstellar Extinction of Planetary Nebulae
We analyze the dependence of circumstellar extinction on core mass for the
brightest planetary nebulae (PNe) in the Magellanic Clouds and M31. We show
that in all three galaxies, a statistically significant correlation exists
between the two quantities, such that high core mass objects have greater
extinction. We model this behavior, and show that the relation is a simple
consequence of the greater mass loss and faster evolution times of high mass
stars. The relation is important because it provides a natural explanation for
the invariance of the [O III] 5007 planetary nebula luminosity function (PNLF)
with population age: bright Population I PNe are extinguished below the cutoff
of the PNLF. It also explains the counter-intuitive observation that
intrinsically luminous Population I PNe often appear fainter than PNe from
older, low-mass progenitors.Comment: 12 pages, 2 figures, accepted for ApJ, April 10, 199
The edge of the M87 halo and the kinematics of the diffuse light in the Virgo cluster core
We present high resolution FLAMES/VLT spectroscopy of intracluster planetary
nebula (ICPN) candidates, targeting three new fields in the Virgo cluster core
with surface brightness down to mu_B = 28.5. Based on the projected phase space
information we separate the old and 12 newly-confirmed PNs into galaxy and
intracluster components. The M87 PNs are confined to the extended stellar
envelope of M87, within a projected radius of ~ 160 kpc, while the ICPNs are
scattered across the whole surveyed region between M87 and M86. The velocity
dispersions determined from the M87 PNs at projected radii of 60 kpc and 144
kpc show that the galaxy's velocity dispersion profile decreases in the outer
halo, down to 78 +/- 25 km/s. A Jeans model for the M87 halo stars in the
gravitational potential traced by the X-ray emission fits the observed velocity
dispersion profile only if the stellar orbits are strongly radially anisotropic
(beta ~= 0.4 at r ~= 10 kpc increasing to 0.8 at the outer edge), and if
additionally the stellar halo is truncated at ~= 150 kpc average elliptical
radius. From the spatial and velocity distribution of the ICPNs we infer that
M87 and M86 are falling towards each other and that we may be observing them
just before the first close pass. The inferred luminosity-specific PN numbers
for the M87 halo and the ICL are in the range of values observed for old (> 10
Gyr) stellar populations (abridged).Comment: Accepted for publication in Astronomy and Astrophysics. 16 pages, 14
figures and 4 table
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