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

•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

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.

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

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

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

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

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).

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

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

Temperature diagnostics:

T[O III], etc.

T (recombination lines) – O++ , C++, C+++, N++, etcT (He lines)T Balmer continuum

Hyung & Aller 1995

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 …

The formulation is a first approximation to describe possible temperature distributions

a) Temperatureinhomogeneities

The formulation is a first approximation to describe possible temperature distributions

a) Temperatureinhomogeneities

b) Temperature& densityinhomogeneities

Other options

Planetary nebulae

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

Esteban et al. 1997

Orion Nebula

I(4649) / I(H)= 1.2 x 10-4

T(Balmer continuum) vs. T[O III]

Liu & Danziger 1993

N(C++) from recombination lines vs. N(C++) from collisionally excited lines

Peimbert, et al. 1995

CII 4267 line

C III] 1909 line

Liu et al. 2001

N(O++) vs. Balmer temperature

Recombination/collisionally excited ratios (log ADF) vs. [O III] – Balmer Temperatures

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

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.

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.

Tsamis et al. 2007

NGC 5882

Integral field spectroscopy

NGC 6153

Temperature and abundance 4959 and 4649

Tsamis et al. 2007

Tsamis et al. 2007

NGC 6153. ADF radial profile

Tsamis et al. 2007

NGC 5882

T[O III] = 9160T(rec) = 2400

2-phase composition in PNe:

Cold inclusions H-poor of a few % massC/O, Ne/O

Ejecta from starsPlanetary bodies

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

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

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

HII regions

Orion NebulaSmall scale structures and t 2

O´Dell et al. 2003

[O III] 5007 image

Orion Nebula – [O III] temperature

O´Dell et al. 2003

T[4363/5007] columnar values for each pixel

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

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

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

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

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

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

Our work

Anabel Arrieta**Leonid Georgiev*Michel Richer*

* Instituto de Astronomía, Universidad Nacional Autónoma de México** Universidad Iberoamericana, México

a

b

Our data:

Echelle spectra from 2.1-m at San Pedro Mártir

NGC 7009-a(along major axis)

Position-velocity diagrams

ordered by excitation potential

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

NGC 7009-b(along minor axis)

Position-velocity diagrams

ordered by excitation potential

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

a

b

NGC6543-a

Position-velocity diagrams

Ordered by excitation potential

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

NGC 6543-b

Position-velocity diagrams

Ordered by excitation potential

Same as previous, but for slit b

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

NGC 7027

Position-velocity diagrams

Ordered by excitation potential

NGC 7027

Ratio of oxygen lines (min, max, rms)4649/4363       0.82   1.6  0.11

4363 4649 4649/4363

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.

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.