1. Local Group Census NGC 6822 P. Leisy (1,3) L. Magrini (2), R. Corradi (1), A. Mampaso (3) (1) Isaac Newton Group (La Palma, SPAIN) (2) Universita’ di Firenze (ITALY) (3) Instituto Astrofisico Canarias (Tenerife, SPAIN)

2. Introduction Irregular Dwarf galaxy Ir IV-V Irregular Dwarf galaxy Ir IV-V Distance 490 Kpc (m-M=23.48) Distance 490 Kpc (m-M=23.48) Low metallicity Log(O/H)+12~8.1 (HII) Low metallicity Log(O/H)+12~8.1 (HII) 7.91 Chandar et al. 2000 8.25 Skillman et al. 1989 or Pagel et al 1980 -2.0 < [Fe/H] ~-1.0 Tolstoy et al. 2001 Gas rich galaxy – Huge HI envelope Gas rich galaxy – Huge HI envelope currently ongoing “low” star formation taking place

3. Several set of data Imaging Imaging ESO/WFI H , [OIII], [SII], B, continuum ING/WFC H , [OIII], [SII], r, Str Y Spectra Spectra ESO / NTT (8 long slit spectra) ING / WHT-AF2 (fiber multi-spec 40’ )

4. Filters used

6. NGC 6822 PNe / outliers Supergiant HI shell r>40’ or ~6Kpc Blok & Walter 2000 Red giant extension (6 scale length) Letarte et al. 2002

7. Criteria Criteria Ha – [OIII] emitter Point-like (at 500Kpc 1” = 2.5pc) No Continuum Not using Not using R=[OIII]/(Ha+[NII]) > 1 loose some PN R=[OIII]/(Ha+[NII]) > 1 loose some PN Ratio-[OIII]/Ha Ratio Ha/Cont PNe>100-200 - HII ~ 30-50 Ratio Ha/Cont PNe>100-200 - HII ~ 30-50 Most PNe distributed in the bar young population ? Most PNe distributed in the bar young population ? 2-3 intergalactic PN candidates ? (~15 Kpc) 2-3 intergalactic PN candidates ? (~15 Kpc) PNe candidates

8. Diagram Ha/NII Ha/SII First introduced Sabbadin & D’ Oddorico 1978 Great potential to select candidates; place HII vary inside the Local Group galaxies G. Delgado 2003, IAC Master Thesis, 2003 Delgado, Viironen, Mampaso, Corradi II Internat. workshop of science with GTC 2004 Ha/[OIII]-Ha/[SII].jpg

9. PNLF with 19 PNe Completeness ~3 mag Completeness ~3 mag 2 ind. sets of data (Jacoby) 2 ind. sets of data (Jacoby) Dist = 23.91+/- 0.19 Dist = 23.91+/- 0.19 Extinction correction Extinction correction Av=0.26-0.45 mean~0.32 Av=0.26-0.45 mean~0.32 8 PNe : 0.45<C(H  <  or Av ~ 0.3-1.0 or Av ~ 0.3-1.0 Dist = 23.6 +/- 0.4 Dist = 23.6 +/- 0.4 23.48 +/- 0.06 (2003) 23.48 +/- 0.06 (2003)

10. Spectra NTT spectra of PNe / HII NTT spectra of PNe / HII 10-20mn exposure time high S/N ratio (brightest objects) high S/N ratio (brightest objects) need observations with 8-10m class telescopes need observations with 8-10m class telescopes

11. Diag. N/O - He NGC 6822 (M33) more He ? or much less N LMC – SMC Large N/O

12. Diag. N/O - O NGC 6822 Oxygen ? sample too small LMC – SMC dest O 2 nd Type I slight prod O 2x ? (Carbon 10-100x) M33 same trends MC

13. Conclusions 15 new PNe in NGC6822 (19 in total) Difficulty distinguish PNe/compact HII  spectra  spectra distance PNLF ~23.6 +/- 0.4 (~500 Kpc) distance PNLF ~23.6 +/- 0.4 (~500 Kpc) individual extinction derived from spectra individual extinction derived from spectra High He, faint N (like in M33) High He, faint N (like in M33) N/O ratio SMALL (compare to LMC-SMC) N/O ratio SMALL (compare to LMC-SMC)

15. Laura MAGRINI Sextans A / Sextans B VLT m-o spectroscopy

17. Temperatures Kaler 1994 Relation T[NII] = fn ( T[OIII] ) for Galactic PNe

18. Diag. N/O - N NGC 6822 - M33 Faint N (N/O)