silvia torres-peimbert instituto de astronomía universidad nacional autónoma de méxico
DESCRIPTION
Nebular kinematics of planetary nebulae as tests of possible differences of distribution of permitted and forbidden emission lines. Silvia Torres-Peimbert Instituto de Astronomía Universidad Nacional Autónoma de México. September 14, 2007. Outline. - PowerPoint PPT PresentationTRANSCRIPT
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Nebular kinematics of planetary nebulae as tests of possible differences of distribution of permitted and forbidden emission linesSilvia Torres-Peimbert
Instituto de AstronomíaUniversidad Nacional Autónoma de México
September 14, 2007
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•Recombination vs. forbidden lines diagnostics•Definitions
T [O III], T (Balmer), T (O II), T (C II)•Temperature variations vs. compositon and temperature
variations •Planetary nebulae•HII regions•Our work•Conclusions
Outline
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Why are abundances important? • Tests for atomic physics computations
• The input chemical composition to produce models of nebulae
• Constraints on the stellar evolution theory of IMS from those elements affected by stellar evolution
• Initial abundances in the ISM for those elements not affected by stellar evolution
• Constraints on models of galactic chemical evolution
• Constraints on models of the chemical evolution of the universe through the determination of ΔY/ΔZ and the determination of the primordial helium abundance.
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To derive abundances from emission lines:
We require temperature diagnostics:
Forbidden line intensity ratios
I(4363)/I(5007)I(5577)/I(6584)
Abundance derivations:
N(O++) /N(H+) = I(5007)/I(Hbeta) f(Te,Ne)
f(Te,Ne) is very sensitive to temperature
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There is a problem:
•This is a widespread phenomenon: HII regions and PNe
•The recombination coeficients are correct
•The ratios C/O/N/Ne are the same
•The temperature variations are larger than expected
•Gas abundance values are those of the recombination lines (higher)
•There are inclusions of cold high metallicity gas
•They are low temperature
•The overall gaseous abundance is the expected
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Are there temperature variations?
Models predict t2 ~ 0.003 to 0.03, with typical values around 0.01
Observations give values of t2 in the 0.00 to 0.09 range typical values ~ 0.03)
ADF (abundance difference factor) = abundances derived from permitted lines / forbidden lines ~ 2 to 3 (O, C, N, Ne),
If t2 = 0.00 it is possible to reconcile the abundances
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Causes for temperature variations
• Chemical inhomogeneities
• Deposition of mechanical energy
• Time dependent ionization
• Density variations
• Deposition of magnetic energy
• Shadowed regions
• All of the above
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Time dependent ionization
• Photoionization fronts heat the gas above the steady state value – Delay before reaching equilibrium
• Decreasing stellar ionizing flux, – the outer regions of the nebula become isolated from
the stellar radiation field – Will cool first and then recombine– Producing cold partially ionized outer regions (this
might be the case in NGC 7009).
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Deposition of mechanical energy
The following objects are strong X-ray emitters (Guerrero et al. 2005):
BD+30 (WR)NGC 40 (WR)NGC 2392NGC 3242NGC 6543 (WR)NGC 7009NGC 7027
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Density variations
• Extreme density variations are present in most PNe
(optical images)– For steady state photoionization models, density
variations are generally not included– For time dependent processes, the regions of higher
density will reach equilibrium sooner than those of lower density
• Also, density variations might affect the temperature determination if using the wrong characteristic density– e.g. the IR determined densities usually are a lower
limit to the average density of a typical PNe
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Temperature diagnostics:
T[O III], etc.
T (recombination lines) – O++ , C++, C+++, N++, etcT (He lines)T Balmer continuum
Hyung & Aller 1995
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Te(4363/5007) = T0 [1 + (90800/T0 -3) t 2/2]Te(Bac/H) = T0 (1 – 1.70 t 2)
Te(4649/5007) = f1 (T0 , t 2)
T0 =
t 2 =
Te Ne Ni dV
Ne Ni dV
(Te - T0)2 Ne Ni dV
T02
Ne Ni dV
Te(He lines) = T0 (1 – k t 2) k~1.8
Te(4267/1909) = f2(T0 , t2)
Temperature determinations
Peimbert 1967 …
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The formulation is a first approximation to describe possible temperature distributions
a) Temperatureinhomogeneities
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The formulation is a first approximation to describe possible temperature distributions
a) Temperatureinhomogeneities
b) Temperature& densityinhomogeneities
Other options
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Planetary nebulae
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Liu et al. 2001
M1-42
M2-36
M2-36 Bac = 5,900K [OIII] = 8,400K
M1-42 Bac = 5,360K [OIII] = 9,200K
Temperatures
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Esteban et al. 1997
Orion Nebula
I(4649) / I(H)= 1.2 x 10-4
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T(Balmer continuum) vs. T[O III]
Liu & Danziger 1993
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N(C++) from recombination lines vs. N(C++) from collisionally excited lines
Peimbert, et al. 1995
CII 4267 line
C III] 1909 line
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Liu et al. 2001
N(O++) vs. Balmer temperature
Recombination/collisionally excited ratios (log ADF) vs. [O III] – Balmer Temperatures
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Chemical homogeneity diagnostics
When all helium is He+ and all oxygen is O++, it can be shown that:
• If t2(Balmer , [O III]) ≈ t2(He I , [O III]) ≈ t2(O II, [O III])
≈ t2(C II, [C III]) chemically homogeneous
• If t2(Balmer , [O III]) < t2(He I , [O III]) ≈ t2(O II, [O III]) ≈ t2(C II, [C III]) chemically inhomogeneous
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Evidence for chemically homogeneous PNe:
• For well observed objects:
t2 values derived from T(Balmer) and T([O III]) are similar to those derived from T(He I) and T([O III]),
T(C II) and T([O III]), and T(O II) and T([O III]).
• The carbon evolution of the Galaxy.
• For NGC 5307 and NGC 5315 the radial velocities and the FWHM of the O II and [O III] lines are the same.
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Chemically inhomogeneous nebulae are based on:
• The IR lines yield lower abundances than the RL.
• High density H-poor knots in A30 and A78.
-- They were expelled later and at higher velocities than the main body of the nebula.
-- The photospheric abundances of these stars are H-poor.
• About 10% of the CSPNe and of the white dwarfs in the Sloan sample are H-poor.
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Tsamis et al. 2007
NGC 5882
Integral field spectroscopy
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NGC 6153
Temperature and abundance 4959 and 4649
Tsamis et al. 2007
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Tsamis et al. 2007
NGC 6153. ADF radial profile
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Tsamis et al. 2007
NGC 5882
T[O III] = 9160T(rec) = 2400
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2-phase composition in PNe:
Cold inclusions H-poor of a few % massC/O, Ne/O
Ejecta from starsPlanetary bodies
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NGC 6543: Temperature determinations
• T(Bac) = 7100 ± 1000, Kingsburgh et al. 1996• T(Bac) = 6800 ± 400, Zhang et al. 2004• T(He II) = 5730 ± 1000, Zhang et al. 2005, based on 3 He I lines
DiagnosticWesson & Liu (2004)
Georgiev et al. (2007)
T(Bac) 8340 ± 500 6800 ± 400
T(He II) 6450 ±1000 (3) 6674 ± 559 (13)
T([O III] 7990 ± 50 7980 ± 50
T([O II] 9500 ± 500 9500 ± 500
T([O II],[O III]) 8100 ± 100
Georgiev et al. 2007
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NGC 6543: Atmospheric Model
He/H 12+log(C/H)
Central Star 0.10± 0.01 9.02 ± 0.10
Nebula 0.113 ± 0.002 8.90 ± 0.06RL 8.40 ± 0.10CEL
Georgiev, et al. 2007
Orange: pure He modelBlue: their best modelGreen: observations
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NGC 6543: Stellar and nebular abundances
• In units of 12 + Log N(X)/N(H).
Element Stellar Nebular RL Nebular CEL
He 11.00 ± 0.04 11.05 ± 0.01 ….
C 9.02 ± 0.10 8.90 ± 0.10 8.40 ± 0.10
O 9.02 ± 0.10 9.19 ± 0.12 8.79 ± 0.06
Georgiev, et al. 2007
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HII regions
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Orion NebulaSmall scale structures and t 2
O´Dell et al. 2003
[O III] 5007 image
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Orion Nebula – [O III] temperature
O´Dell et al. 2003
T[4363/5007] columnar values for each pixel
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Orion Nebula: Noise vs. true temperature variations
O´Dell et al. 2003
The face of the nebula is mottled with small scale variations in TC with angular dimensions of about 10” (~0.02 pc) and amplitudes of 400 K
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Chemically inhomogeneous H II regions: Pros
• NGC 5253 -- N excess Sanchez-Lopez et al.(2007). - from the O II and C II recombination lines - t 2 values of 0.052 and 0.072, - the excess N is due to pollution by massive WR stars
• 30 Dor -- Tsamis and Pequignot (2005) - chemically inhomogeneous model of 30 Doradus - reproduces the observed line intensities of the forbidden
and permitted O, C, and N lines
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Chemically inhomogeneous H II regions : Objections
• The model of Tsamis & Pequinot- Excess abundance of O x 8- Excess C x 14- Models of chemical evolution of irregular galaxies (Carigi,
et al. )Carbon: 64% due to IMS, 36% to massive starsNitrogen: ~80% is due to IMS Oxygen: 100% massive stars
- The ratios C/N/O do not fit
• The small dispersion in abundances of H II regions in irregular galaxies and in the abundance gradient in our galaxy are against this idea
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Chemically inhomogeneous H II regions(2 phase model): Implications
• 30 Dor A.
• Peimbert give: 12 + log O/H = 8.45, • Tsamis & Pequinot give 8.33 for t2 = 0.000 and 8.54 for t2 = 0.033
• Therefore the TP model is closer to the abundances given by the O II lines than to those given by the [O III] lines and the T[O III] temperature
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Overall situation 2/2
• PNe with strong X-ray emission show large t2 (BD + 30, NGC 40, NGC 2392, NGC 3242, NGC 6543, NGC 7009, NGC 7027)
• Objects with large velocity dispersions also show large t2 (NGC 2392, NGC 2371-2, NGC 2818, NGC 6302, and Hu 1-2)
• Galactic chemical evolution models indicate that most of the carbon of the galaxy has been produced by intermediate mass stars.
Consistent with C/H derived from recombination lines
• Future:
Compare stellar abundances with nebular abundances
Determine accurate density and temperature diagnostics
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Overall situation 1 / 2
• Most PNe show temperature variations larger than predicted by photoionized chemically homogeneous models
• High quality observations are needed to show if a given nebula is chemically homogeneous or not
• The comparison of T(He I) with T(Balmer) is important. (For nebulae where practically all He is He+)
• A small fraction of PNe show chemical inhomogeneities that can produce large temperature variations
• Only about 10% of the central stars of PNe and of the white dwarf samples are H-poor
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Our work
Anabel Arrieta**Leonid Georgiev*Michel Richer*
* Instituto de Astronomía, Universidad Nacional Autónoma de México** Universidad Iberoamericana, México
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a
b
Our data:
Echelle spectra from 2.1-m at San Pedro Mártir
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NGC 7009-a(along major axis)
Position-velocity diagrams
ordered by excitation potential
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NGC 7009-a(along major axis)
Oxygen lines
4363 4649 4662
4649/4363 4662/ 4363 4662/4649
Ratio of oxygen lines (min, max, rms)4649/4363 0.56, 1.3 , 0.14 4662/4363 0.58, 1.27, 0.12 4662/4649 0.78, 1.37, 0.08
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NGC 7009-b(along minor axis)
Position-velocity diagrams
ordered by excitation potential
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NGC 7009-b(along minor axis)
Oxygen lines
Ratio of oxygen lines (min, max, rms)4649/4363 0.78 1.14 0.06 4662/4363 0.71 1.19 0.07 4662/4649 0.70 1.29 0.08
4363 4649 4662
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a
b
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NGC6543-a
Position-velocity diagrams
Ordered by excitation potential
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NGC 6543-a
Oxygen lines
Ratio of oxygen lines (min, max, rms)4649/4363 0.62 1.17 0.08 4662/4363 0.55 1.35 0.11 4662/4649 0.55 1.61 0.13
4363 4649 4662
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NGC 6543-b
Position-velocity diagrams
Ordered by excitation potential
Same as previous, but for slit b
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NGC6543-b
Oxygen lines
Ratio of oxygen lines (min, max, rms)4649/4363 0.60 1.20 0.092 4662/4363 0.08 1.92 0.19 4662/4649 0.08 2.38 0.17
4363 4649 4662
4649/4363 4662/4363 4662/4649
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NGC 7027
Position-velocity diagrams
Ordered by excitation potential
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NGC 7027
Ratio of oxygen lines (min, max, rms)4649/4363 0.82 1.6 0.11
4363 4649 4649/4363
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Our results
In NGC 7009
Along slit b there is an excess of emission in the O II lines in the central regions, where both 4649 and 4363 lines are faint.
lower central temperature?higher density?differences of the velocity distribution?
In NGC 6543 and NGC 7027
No systematic differences in the velocity diagrams.
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In conclusion
• We do not find a difference in velocity distribution of the O II and [O III] emitting regions.
• This result limits the possibility of chemically inhomogeneous condensations
In contrast to Abell 30
• If indeed these condensations are present in these objects, they have the same velocity distribution.