Photoionized regions in NGC 6822

Photoionized regions in NGC 6822

Liliana Hernández-Martínez

lhernand@astroscu.unam.mx

Instituto de Astronomía

Universidad Nacional Autonóma de México

Liliana Hernández-Martínez

lhernand@astroscu.unam.mx

Instituto de Astronomía

Universidad Nacional Autonóma de México

IAC-150408

Dwarf Irregular GalaxiesDwarf Irregular Galaxies

Low mass Low metallicity Gas rich. Star Formation Chemical homogeneity

Low mass Low metallicity Gas rich. Star Formation Chemical homogeneity

IAC-150408

IAC-150408

NGC 6822NGC 6822

- Optical radius 2.9kpc x 2.9kpc (Mateo, 1998)

- HI radius 6kpc x 14kpc (Blok & Walter, 2000)

- Optical radius 2.9kpc x 2.9kpc (Mateo, 1998)

- HI radius 6kpc x 14kpc (Blok & Walter, 2000)

N

E

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.

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.

Barred dwarf galaxy of type Ir IV-VBarred dwarf galaxy of type Ir IV-V

-Lv=9.44x107Lsun

-Mtot=1.6x109Msun

-Lv=9.44x107Lsun

-Mtot=1.6x109Msun

-Distance 490 ± 40 kpc- Vel Hel:-54 Km/s-Distance 490 ± 40 kpc- Vel Hel:-54 Km/s

IAC-150408

Objects with emission Lines NGC 6822 (previous knowledge)

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).

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

Extragalactic PNe 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.

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

PNe in the Local Group of galaxiesPNe in the Local Group of galaxies

Milky Way

Extragalactic PNeExtragalactic 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

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

PNe in NGC6822 (CTIO)PNe in NGC6822 (CTIO)

E

N

36.8arcmin

Dithered (to cover the gaps) IAC-150408

NGC 6822 MOSAIC2 CTIONGC 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.

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

8 OIII average images8 OIII average images

4 D51 average images 4 D51 average images

Continuum subtractedContinuum subtracted

[OIII] - D51[OIII] - D51

8 OIII average images8 OIII average images

4 D51 average images 4 D51 average images

Continuum subtractedContinuum subtracted

[OIII] - D51[OIII] - D51

Searching for PNe…Searching for PNe…

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By blinking on-band, off -band…By blinking on-band, off -band…

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New PNe in NGC6822.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)

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)

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Flux calibration…

UCLAN 260308

Spatial DistributionSpatial Distribution

N

E

26 PNe candidates in NGC 6822.

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Cumulative Planetary Nebula Luminosity Function.

N = normalization constant = apparent distance modulus

m* = apparent peak magnitudes of the luminosity function

€

=5logd − 5 + A5007€

N(m) = N exp−0.307μ exp0.307m5007 (1− exp3(m*5007 −m5007 ))

m*=19.35

Nexp(-0.307= 6.72x10-3

IAC-150408

…Cumulative PNLF.…Cumulative PNLF.

Hernandez-Martinez, L. et al, in preparation IAC-150408

Absolute peak magnitud of the PNLF. 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*5007(0) -4.83

This work

M*=-4.47±0.05

Ciardullo et. al (2002)

M*=-4.47±0.05

Ciardullo et. al (2002)

M*=-4.57, NGC3109 Peña et al, 2007

IAC-150408

Spectroscopy…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.

-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.

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N

E

PN1

PN4

IAC-150408

9 Planetary Nebulae 2 HII regions

Observations

PN1,PN4

PN7, HII8, PN14, PN13, PN19, PN11 and PN9, PN12, H24, quiet faint

Spectrophotometric StandardsEG274 600B 600 RILDS749B 600B 600RI BPM16274 600B 600RI

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VLT spectra:

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43634471

H

PN1 blue

PN1 red

[SII]6678

[NII]

H

[NII]

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Data analysisData 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).

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

Ionic AbundancesIonic Abundances

7 PNe,VLT1 HII Region

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Total Abundances Total Abundances

Richer & McCall 2007

Peimbert et al. 2006

Richer & McCall 2007

I

I*

*

IAC-150408

PN-VLTHII-VLTPN-MHII-MHII-P

IAC-150408

Chemical evolution Model (IRA)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

InfallInfall

IAC-150408

Carigi et al. 2006

Initial Mass FunctionInitial Mass Function

IMF normalized from 0.01 to 60 M_sun

IAC-150408

Star Formation RateStar Formation Rate

Carigi et al, 2006Carigi et al, 2006

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YieldsYields

Karakas & Lattanzio,2007

Geneva’s group &Woosley & Weaver (1995)

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(very) Preliminary results (very) Preliminary results

Conclusions.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.

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

On-band, off-bandOn-band, off-band

UCLAN 260308