IRderived Abundances in the Galaxy and the Magellanic Clouds

1
IR-derived Abundances in the Galaxy and the
Magellanic Clouds

• Jeronimo Bernard-Salas
• (Cornell University)

Vianney Lebouteiller Stuart Pottasch Shannon
Gutenkunst Bernhard Brandl Vassilis
Charmandaris Jim Houck
Aegina, Jun 2008
2
Outline/Motivation

• Understand the formation and spatial distribution
  of elements in star forming galaxies - spirals
  (MW) and irregulars (Magellanic Clouds)
• Use both PNe and HII regions to estimate
  abundances (Ne, Ar, S, O, Fe) in order to
  constrain the time the elements were created
• Use ISO/SWS and Spitzer/IRS to measure IR lines
  to reduce uncertainties and probe dust enshrouded
  regions
• Study abundances in large scales (Galactic disk,
  bulge and MC PNe, and HII regions) as well as on
  small scales (detailed study of extended SF
  regions, NGC3603, 30 Dor, N66)

3
Formation of Elements

• Big Bang H, He, Li, Be
• Massive stars (Mgt8M?)
• ?-elements (O, Ne, S, Ar, )
• r-process elements (Zn,.actinides)
• Type Ia SNe
• 70 Fe
• Small amounts of heavy elements
• Low- intermediate-mass stars (0.8-8M?)
• He, C, N
• s-process elements (Sr, Y,Pb)

Figures from Chiappini (2001) and the FORS team
4
Advantages of using IR

• IR-lines are little dependent on Te
• Correction for missing ionization states is small
• Correction for extinction usually unimportant,
  allowing the study of dusty regions
• Dust emits in IR

5
Solar Abundances

• Solar present abundances different than a decade
  ago
• C, N, O are a factor of 2 lower (Allende Prieto
  et al. 2001, 2002)
• No lines of Ne and Ar in the solar photosphere
• Ne/H 7.84-8.08 dex (Grevesse Sauval 1998,
  Asplund et al. 2005, Landi et al. 2007)
• Ar/H 6.18-6.62 dex (Feldman Widgin 2003,
  Asplund 2005)
• Solar Sulfur abundance has decrease over the
  years
• S/H 7.15-7.33 dex (Grevesse Noels 1993, Asplund
  et al. 2005)

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MW MCs
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The Galactic Disk

• PNe and HII regions show similar trends
• Galactocentric gradients for O, Ne, S and Ar are
  present (i.e. Maciel Koeppen 1994 and van Zee
  in spiral galaxies)
• Ne/H in PNe and HII regions favors the Solar
  abundance from Feldman Widing (2003)
• Sulfur is under-abundant respect to Solar

Pottasch Bernard-Salas (2006)
HII regions Martin-Hernandez et al. (2002),
Esteban et al. (2005), Carigi et al. (2005).
Solar abundances O/H and S/H Asplund et al.
(2005), Ne/H and Ar/H Feldman Widing (2003)
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NGC3603

• Agreement between IR- and optical-derived
  abundances
• No evidence from enrichment (WR stars, Brinchmann
  et al. 2008, Lopez-Sanchez talk)
• Abundances agree with solar within errors but
• S/H is lower than solar
• Ar/H is higher
• Iron is clearly depleted

Optical references Garcia-Rojas et al. (2006),
Tapia et al. (2001), Simpson et al. (1995)
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Bulge PNe

• Important in the study of the stellar population
  of inner part of the Galaxy (Mauela Zoccalis
  talk)
• Dissipational or dissipationless collapse? (Molla
  et al. 2000, Minniti et al. 1995)
• Secular evolution? (Minniti et al. 1995, Moorthy
  Holtzman 2005)
• Many studies point toward a more metal rich bulge
  than disk (Ratag et al. 1992, Cuisinier et al.
  2000, Gorny et al. 2004, Wang Liu 2007)
• Selection criteria
• Galactic Coordinates l lt 10? and b lt 10?
• High radial velocities
• Diameters lt5
• Isolated objects in IRAS point source catalogue

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Bulge PNe Abundances
Neon
Sulfur
Argon
Oxygen

• Bulge PNe do not follow the trend of disk PNe
  pointing to different evolution
• But we cant conclude the presence/absence of a
  gradient (dissipational/dissipasionless collapse)

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MC PNe and HII regions

• Compared to Galactic disk PNe Neon is 1/3 and 1/6
  for LMC and SMC
• Ne/S ratio similar to Galactic disk PNe (except
  4)
• The 2 PNe with higher Ne/S ratio have a strong
  MgS feature
• No evidence for Neon enrichment (except maybe 2
  PNe)

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30 Dor N66
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Abundances in 30 Dor N66

• IR abundances agree with previous determinations
• Neon abundance is very constant
• Iron likely depleted onto dust

Lebouteiller et al. (2008)
Optical references Simpson et al. (1995),
Peimbert (2003), Tsamis Pequignot (2005),
Vermeij van der Hulst (2002), Rosa Mathis
(1987), Mathis et al. (1985), Shaver et al
(1983), Dufour et al. (1982), Peimbert et al.
(2000)
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Ne and S

• Ne and S correlate with each other, in contrast
  with the lack of correlation of Stabursts found
  by Verma et al. (2003)
• The lower the Z the closer to the solar value,
  dust depletion?
• Vassilis Charmandaris talk

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What About Mixing?
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Metal Enrichment

• Effective mixing in HII regions allow metals to
  mix in 100s pc and 100Myr (Roy Kunth 1995,
  Avillez Mac Low 2002)
• Observations challenge this hypothesis and
  suggest mixing on large scales and timescales
  (Kobulnicky 1998, Skillman Kennicut 1993,
  Russel Dopita 1990)
• We see no significant enrichment ( factor 2) by
  current or previous SF episodes more recent than
  1 Gyr
• Tenorio-Tagle scenario (Tenorio-Tagle 1996)

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Small Scale Mixing

• In the Tenorio-Tagle scenario mixing occurs at
  small scales (lt1pc)
• Typical distance between our observations are 4,
  15, 20 pc
• Uncertainties in estimating abundances are
  0.1dex but ??Ne/H) is 0.02 dex (5)
• Note that 5 of the Ne/H in 30 Dor total Neon
  enrichment in IZw18
• According to Kunth Sargent (1986) this
  represents the minimum enrichment of an HII
  region in a starburst episode
• Small scale mixing is apparently effective
  abundance fluctuations lt55, but internal
  variations (5) cannot be inferred

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Conclusions

• Galactic PNe and HII regions show abundance
  gradient of -0.085 dex/kpc for O/H, -0.13 dex/kpc
  for Ne, Ar, S
• PNe and HII regions show sulfur under-abundance
  w.r.t. to solar, and their neon abundances favor
  the solar value by Feldman Widing (2003)
• Bulge PNe do not follow the Galactic disk
  gradient indicating a different evolution for the
  Disk and the Bulge
• Abundances of Ne, S, and Ar in giant HII regions
  very homogeneous
• No indication of enrichment from hot gas phase in
  30 Dor