Kinematic Evidence of Different PN Populations in Elliptical Galaxy NGC 4697 Niranjan Sambhus, Ortwin Gerhard Astronomy Institute, University of Basel, Switzerland & Roberto H. Mendez Institute for Astronomy, University of Hawaii, USA

Extragalactic PNs Universal PNLF: distance determination Discrete kinematic tracers: mass, angular momentum distribution in halos of galaxies Tracers of diffuse intra-cluster stellar population Tools for metallicity measurements in outer regions of galaxies Ubiquitous in galaxies irrespective of Hubble type

NGC 4697 Axisymmetric E 4/5, ~ edge-on, M B = R e ~ 95”, ~ 0.9, age ~ 9 Gyr, [Z/H] C ~ 0.4 X-ray: point sources (XPS) (Zezas et al 2003: HMXBs?) Distance: Mpc (SBF,  = 30.35), 10.5 Mpc (PNLF,  = 30.1) in front of the Virgo group Stellar kinematics within R e consistent with no DM 4’

PNs in NGC 4697 (Mendez et al 2001) Detection: 535 PNs up to ~ 300” Velocity data: 531 PNs (max error of 40 km/s) Velocity and magnitude data: Total sample (526 PNs) Complete sample: m 5007 < 27.6 outside a central ellipse with semi-major axis 60” (320 PNs) FORS1 on VLT: ON - OFF blinking on-dispersed image shift On-band filter: FWHM = 60 Å, peak transmission = 0.76 Grism 600B: 1.2 Å pixel -1 at 5000 Å

PN system in NGC 4697 Asymmetric rotation 526 PNs MajMin V sys = 1274 km/s

PNs in Velocity - Magnitude plane Sense of rotation: velocity folding, U = sign(x) * (V - Vsys) Co-rotation: U > 0, Counter-rotation: U < 0 Velocity coverage not biased by PN magnitude Complete sample: Velocity - Magnitude correlation ! Brightest counter-rotating PNs differ in kinematics

Spatial distribution of bright PNs Bright PNs: Left-right asymmetry Radial distribution: Bright and Faint PNs are KS compatible (92%), follow the surface brightness profile Azimuthal distribution: KS incompatible (1.8%), similar to XPS counter Co-rot m(5007) < 26.2 m(5007) > 26.9

Azimuthal kinematics of bright & faint PNs Bright PNs incompatible with faint PNs as well as stellar kinematic data: - +ve velocity along major axis - -ve velocity along minor axis - azimuthally varying dispersion (100 km/s <  < 200 km/s) Faint PNs follow stellar kinematics: - No minor axis rotation - Peak major axis velocity ~ 60 km/s - constant dispersion (120 km/s) Bright Faint Azimuthal as well as kinematic distribution of bright PNs in NGC 4697 differs significantly from that of the faint PNs as well as the underlying galaxy stellar population

Which PN population in NGC 4697 is “normal”?  Criteria: m(5007) < 26.2 m(5007) > magnitudes ? - Kinematics ? - Spatial distn ? m(5007) - U correlation: 12/18 kinematic outliers are highly counter-rotating 10/12 PNs lie in the angular over-density region First Approximation of Normal PN population: km/s  V PN  -100 km/s AND - All PNs with m(5007) > For PNs with m(5007)  26.2, after removing the angular over-density

LF of the “normal” PNs in NGC 4697 Complete Scaled Subtracted C  = 0.3 ! Sub   0.15 This could be a lower limit

Errors & Contamination issues: Observations  Unbiased velocity coverage: FORS1 filter width is  1800 km/s around V sys of NGC 4697, and peak transmission of 0.76 with positional error corrections < 5%  Photometric rms errors < 0.2 mag ( 0.1 for m(5007) < 26.5 )  E & W field: positional error < 0.3 pixel ( < 20 km/s)  Max velocity error ~ 40 km/s including contributions from image calibration, registration, guiding & spectrograph deformation

Contamination of bright PNs (m5007 < 26.2)? Background sources: - HII regions: Spectra of 13 of these PNs (Mendez et al 2005) show no detectable continuum & line ratios of metal-rich PNs - Emission line sources: Ly  galaxies would have m(5007) > 26.2, detectable in radial velocity Foreground sources (ICPN?): -NGC 4697 (d = 10.5 Mpc) is closer than virgo (M87: d = 13.8 Mpc) -Velocity dispersion of bright Pns,  ~ 170 km/s, much smaller than those of Virgo ICPNs (~ 800 km/s) -Radial distribution of both bright and faint PNs are KS compatible (92%), are concentrated towards the center, and follow the galaxy light -Surface density of bright PNs is ~0.58 PNs/armin 2 ; mean surface density of Virgo ICPNs is ~0.02 PNs/arcmin 2

Other galaxies: –Large, complete sample with velocity is needed Currently NGC 4697 is one of the largest such samples. –PN.S sample: ~ 200s, magnitude distribution & completeness under investigation –Cen A (merger remnant): Old sample (  = 0.3, filter transmission uncertainities), New sample: under investigation.

Origins A large fraction of bright PNs belongs to a dynamically young population that is not well mixed in the gravitational potential of NGC 4697 Spatial distribution is similar to XPS (possibly HMXBs). Zezas et al 2003 suggest a merger or late tidal infall, though not observed in photometry 13/42 bright PNs have near solar metallicity outside R e, stellar population inside this radius has solar or higher [Z/H] (Mendez et al 2005). [Z/H] does not appear to be the reason for population difference Marigo et al 2004 suggest age difference to be a possible driver If so, scenario consistent with Zezas et al 2003 argument of XPS being HMXBs formed several 10 8 years ago in tidal tails now falling back. Bright PNs could trace an age range different but similar to XPS (no signatures in photometry) Extinction effects in young, bright PNs?

Conclusions Bright & faint PNs in NGC 4697 have significantly different radial velocity distribution. Their mean velocities are co-rotating and ~0 (94% confidence), dispersions differ with 99.3% confidence. PNs in NGC 4697 do not constitute a single population that is a fair tracer of stellar distribution Luminosity functions of extreme counter-rotating sub-sample and the main population are different with 99.8% confidence. PNLF appears to depend on kinematic selection At least two sub-populations: secondary population is prominent in bright PNs with extreme couter-rotation Spatial distribution of bright PNs is different from that of faint PNs. Secondary population is NOT in dynamical equilibrium in galaxy potential Normal population has a bright-end cutoff in PNLF uncertain by ~ 0.2 mag (could be larger)

PN spectra Mendez et al 2005 have FORS1 & Keck LRIS spectra of 13/42 of these bright PNs. –Detect, or put upper limits on [OII] 3727, [OIII] 4363, 4959, H , H , HeII 4686, [OIII]5007, [NeIII]3868 –PNs with strong 5007 line: CLOUDY solutions: T ele = K, Neb Radius = 0.017pc, n ele = 4 * 10 4 cm -3, L * > 7000 L sun (higher if nebula leaks H-ionizing photons, H  luminosity ~ erg/s, T * ~ 10 5 K, Abundances: O (8.60), Ne (7.88), [Z/H] = -0.1 –PNs with weak 5007 line: Not inconsistent with solar metallicity No [OIII] 4363 detected, T ele not very high O abundance ~ 8.2 (Lower limits) –Bright PN: rich in O than faint PNs (M31, MC studies needed) Almost solar metallicity for 80% of studied PNs (bulge of M31) –Metallicity - PN brightness, selection effects, …