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Photoionized regions in NGC 6822

Photoionized regions in NGC 6822. Liliana Hern á ndez-Mart í nez lhernand@astroscu.unam.mx Instituto de Astronom í a Universidad Nacional Auton ó ma de M é xico. IAC-150408. Dwarf Irregular Galaxies. Low mass Low metallicity Gas rich. Star Formation Chemical homogeneity. IAC-150408.

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Photoionized regions in NGC 6822

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  1. Photoionized regions in NGC 6822 Liliana Hernández-Martínez lhernand@astroscu.unam.mx Instituto de Astronomía Universidad Nacional Autonóma de México IAC-150408

  2. Dwarf Irregular Galaxies • Low mass • Low metallicity • Gas rich. • Star Formation • Chemical homogeneity IAC-150408

  3. IAC-150408

  4. NGC 6822 N E Barred dwarf galaxy of type Ir IV-V • Lv=9.44x107Lsun • Mtot=1.6x109Msun • Distance 490 ± 40 kpc • Vel Hel:-54 Km/s - Optical radius 2.9kpc x 2.9kpc (Mateo, 1998)- HI radius 6kpc x 14kpc (Blok & Walter, 2000) NGC 6822. Three colors: H-green, OIII-red and continuum-blue. MOSAIC2 image (4m Blanco, CTIO). 36.8 x 36.8 arcmin. Hernández-Martínez, L., & Peña, M. Sep-Oct, 2005. IAC-150408

  5. Objects with emission Lines NGC 6822 (previous knowledge)  Killen & Dufour (1982): - 36 emission stellar objects - 31 diffuse and extended objects - 14 compact HII regions - 14 stars with H emission line. Hodge et al (1988): 157 HII regions Ford & Peng (2002): 7 PNe. Leisy et al (2005): 17 PNe (total). IAC-150408

  6. Extragalactic PNe  Baade (1955): 5 PNe in M31  Westerlund (1968): ~100 PNe in LMC and SMC Jacoby & Lesser (1981) found NPs in 5 galaxies in the LG  Ciardullo et al. (1989): 429 PNe in M31  Magrini et al. (2000): 134 PNe in M33  Merrett et al. (2003): 2611 PNe in M31 The “Local Group Census” (2001-2004): survey in 14 galaxies. IAC-150408

  7. PNe in the Local Group of galaxies Milky Way

  8. Extragalactic PNe  Planetary Nebulae Luminosity Function (PNLF) - distance determination.  PNe emission lines -“easy to measure” stellar cinematic  Chemical tracers of the past component of the ISM IAC-150408

  9. E N PNe in NGC6822 (CTIO) 36.8arcmin Dithered (to cover the gaps) IAC-150408

  10. NGC 6822 MOSAIC2 CTIO Observations: sept 4th and oct 9th, 2005. CTIO - Mosaic II CCD imager - 8 CCD’s - 36.8 arcmin. 4 filters: [OIII] 4990Å 50Å (2hrs) D51 (DDO) 5130Å 154Å (1.3hrs)Halpha 6563Å 80Å (1hr) Halpha+8 6650Å 80Å(1hr) Reduction: mscred (IRAF). Buell T. Jannuzi, Jenna Claver, and Frank Valdes, June 2003. http://www.noao.edu/noao/noaodeep/ReductionOpt/framesv6.html. - cross talk correction, trimsec, overscan, bias, flats, bpm (bad pixel mask), astrometric calibration - wcs (USNO-A2.0 catalogue), crmask, fixpix (bpm y crmask), tangent-plane projected, skysub. IAC-150408

  11. Searching for PNe… 8 OIII average images 4 D51 average images Continuum subtracted [OIII] - D51 IAC-150408

  12. By blinking on-band, off -band… IAC-150408

  13. New PNe in NGC6822. Selection criteria: - objects in OIII, but not in continuum - objects in H,but not in continuum Pollution agents: -compact Supernova Remnants -compact HII regions (stellar continuum, stars of PNe are 2mag fainter)  apparent magnitudes (punctual objects) measured with digiphot.apphot.phot (IRAF). PSF=6.5pix  comparative photometry (PN7, Leisy et al. 2005) IAC-150408

  14. Flux calibration… UCLAN 260308

  15. N E Spatial Distribution 26 PNe candidates in NGC 6822. IAC-150408

  16. Cumulative Planetary Nebula Luminosity Function. m*=19.35 Nexp(-0.307= 6.72x10-3 N = normalization constant = apparent distance modulus m* = apparent peak magnitudes of the luminosity function IAC-150408

  17. …Cumulative PNLF. Hernandez-Martinez, L. et al, in preparation IAC-150408

  18. Absolute peak magnitud of the PNLF. We can use the true distance modulus 23.48mag (Van de Bergh 2000) and the extinction AV=0.73 (Gallart et al, 1996) to derive a peak absolute magnitude of the luminosity function of NGC 6822. M*=-4.47±0.05 Ciardullo et. al (2002) M*5007(0) -4.83 This work M*=-4.57, NGC3109 Peña et al, 2007 IAC-150408

  19. Spectroscopy… • VLT Multi-Object Spectrograph observations, carried on August 19th to 22nd, 2006. • - We used FORS-2 spectrograph with a field of 6.8’x6.8’ covering the central part of the galaxy. IAC-150408

  20. N E PN4 PN1 IAC-150408

  21. Spectrophotometric Standards EG274 600B 600 RI LDS749B 600B 600RI BPM16274 600B 600RI 9 Planetary Nebulae 2 HII regions Observations PN1,PN4 PN7, HII8, PN14, PN13, PN19, PN11 and PN9, PN12, H24, quiet faint IAC-150408

  22. VLT spectra: IAC-150408

  23. H 4363 4471 PN1 blue IAC-150408

  24. H [NII] [NII] 6678 [SII] PN1 red IAC-150408

  25. Data analysis • Reddening correction: c(H)F(H)/F(H) red F(H)/F(H) blue F(H)/F(H) blue • Direct Method (4363) Te, Ne, ionic abundances. IRAF: temden, ionic • Total abundances: Ionization Correction Factors (ICFs,Kingsburgh & Barlow, 1994). IAC-150408

  26. Ionic Abundances 7 PNe,VLT 1 HII Region IAC-150408

  27. Peimbert et al. 2006 Total Abundances * I I * Richer & McCall 2007 Richer & McCall 2007 IAC-150408

  28. PN-VLT HII-VLT PN-M HII-M HII-P IAC-150408

  29. Chemical evolution Model (IRA) • Accretion (f). • Chemical abundances of the accreted gas (Xaccretedi). • Star Formation Rate (SFR, ). • Initial Mass Function (IMF, ). (Kroupa et al, 1993) • Stellar Yields (Yi, R). • Galactic winds (w). • Metallicity dependence IAC-150408

  30. Infall Carigi et al. 2006 IAC-150408

  31. Initial Mass Function IMF normalized from 0.01 to 60 M_sun IAC-150408

  32. Star Formation Rate • Carigi et al, 2006 IAC-150408

  33. Yields Karakas & Lattanzio,2007 Geneva’s group & Woosley & Weaver (1995) IAC-150408

  34. (very) Preliminary results

  35. Conclusions. • We have increased the PNe sample. The distribution of HII regions appear to be confined to the center of the galaxy instead PNe apparently being over the whole galaxy. • We have derived the peak absolute magnitude of the luminosity function of NGC 6822. We get M*>4.48, Metallicity dependent?, problems with calibrations? Galactic extinction? • In this work we obtained the abundances of 7 PNe. Given a total number of 10 PNe abundances for this galaxy. • Two PNe in our sample are Type I (2.4-8 Msun). • Two are oxygen self-enrichment. This are not useful as observational constraint of Oxygen. • All these results will be taken into account in our chemical model of NGC 6822. IAC-150408

  36. To be continue . . .

  37. On-band, off-band UCLAN 260308

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