Title of article :
KINEMATIC EVIDENCE FOR DIFFERENT PLANETARY NEBULA POPULATIONS IN THE ELLIPTICAL GALAXY NGC 4697
Author/Authors :
Gerhard، Ortwin نويسنده , , SAMBHUS، NIRANJAN نويسنده , , MENDEZ، ROBERTO H. نويسنده ,
Issue Information :
روزنامه با شماره پیاپی سال 2006
Pages :
-836
From page :
837
To page :
0
Abstract :
We have analyzed the magnitudes, kinematics, and positions of a complete sample of 320 planetary nebulae (PNs) in the elliptical galaxy NGC 4697. We show the following. (1) The PNs in NGC 4697 do not constitute a single population that is a fair tracer of the distribution of all stars. The radial velocity distributions, mean velocities, and dispersions of bright and faint subsamples differ with high statistical confidence. (2) Using the combined data for PNs brighter than 26.2, we have identified a subpopulation of PNs that is azimuthally unmixed and kinematically peculiar, and thus neither traces the distribution of all stars nor can be in dynamical equilibrium with the galaxy potential. (3) The planetary nebula luminosity functions (PNLFs) of two kinematic subsamples in NGC 4697 differ with 99.7% confidence, ruling out a universal PNLF. We estimate that the inferred secondary PN population introduces an uncertainty in the bright cutoff magnitude of ~0.15 mag for this galaxy. We argue that this secondary PN distribution may be associated with a younger, ~>1 Gyr old stellar population, perhaps formed in tidal structures that have now fallen back onto the galaxy, as has previously been suggested for the X-ray point sources in this galaxy, or coming from a more recent merger/accretion with a red galaxy. The use of PNs for extragalactic distance determinations is not necessarily compromised, but their use as dynamical tracers of dark halos will require deep observations and careful analysis of large PN samples.
Keywords :
galaxies: kinematics and dynamics , planetary nebulae: general , galaxies: distances and redshifts , galaxies: individual (NGC 4697) , galaxies: elliptical and lenticular, cD
Journal title :
Astronomical Journal
Serial Year :
2006
Journal title :
Astronomical Journal
Record number :
116676
Link To Document :
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