Planetary Nebula abundances in NGC 5128with FORSJ. R. Walsh, ST-ECF, ESOG. H. Jacoby, WIYNR. Pelletier, Kapteyn Lab.N. A. Walton, IoA, Cambridge

MotivationMeasure PN abundances in an elliptical galaxy (Z > Milky Way)Determine abundance gradient (-elements, e.g. O) from PN; compare with stellar values ([Fe/H])From spectra determine if the brightest PN are pathological (upper L cut-off of PNLF)Compare kinematics with abundances halo PN with lower Z or groups of PN with similar abundances (merger remnant?)Input to galaxy evolution models and star formation history

4m-class PN spectra in NGC 5128ESO 3.6m EFOSC long-slit spectra3 slit positions, max exp. 9hrs5 PN selected from Hui et al. (1993)

FORS1 MOS ObservationsThree fields at a range of radial offsets (4, 7.5 & 14.5)PN selected from Hui et al. (1993) catalogue maximizing PN observed with18 slitlets Blue spectra (600B) 3500-5500A, R~2.3 for [O II] 3727 to [O III]5007Red spectra - (300V) 4500-8500 R~5 for H/H, He I, [N II], etc.Exposures to 4hrs per field per spectral range

Results & flux calibrate each slitlet, extract all PN spectraField F56: 20 PN F42: 21 PN F34: 9 PN 50 PN detected 23.5 < m5007 < 28.1PN #5601 300Vspectrum calib F56 MOSspectrumSky+background subtractedPN not in Hui catalogm5007 = 28.1m5007 = 27.5

Spectra and abundancesTie blue and red spectra together with [O III]5007Three brightest spectra analysed in each field[O III]4363 detected in 4 PN; 3 in outer field (low background) and in #5601No [O III]4363, use 5007/H and Excitation class Teff relation of Dopita et al (1992) to give TeDetermined O/H, N/O and He/H where lines availablePN spectra normal. One with N/O>1. One PN with c=0.4, most low (

Galaxy scale abundancesO/H v. r gradient?Harris et al. (1999, 2000, 2002) determined old Red Giant Branch metallicities from HST photometry in 3 fields (two halo, one central) Find broad Metallicity Distribution Function (MDF) with peak Z declining with radiusNave [O/Fe] ~ +0.2Point comparison of O v. Fe in NGC 5128 GCsPN#4211 V=-190km/s

Prospects/Conclusions

Analysis still in progress. About 40/50 PN have most strong lines (H, [O II], [O III], [N II], etc) detected, m5007