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IAU 234: Planetary Nebulae
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Maintained by W-W
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Oral Presentations - Questions and Answers


Talk by Quentin Parker: Milky Way and Magellanic Cloud Surveys for Planetary Nebulae

Q: (Bruce Balick) Please clarify the characteristics of the Halpha filter(s) used for your large-scale PN detection surveys.

A: A 1% filter is where the filter FWHM is 1% of the central wavelength, so in the case of the AAO/UKST H-alpha survey the FWHM is 70A and central wavelength 6590A. This includes most [NII] as well as H-alpha except for high galactic velocity systems and towards the edge of the filter (there is a scanning down with wavelength with off-axis flux for interference filters in converging beams).

Q: (Orsola DeMarco) All morphological types should have younger and older PNe. Why do we only find "old" PNe with circular morphology? Does this not indicate that axisymmetric PNe might look circular in their old age?

A: Old PNe tend to be 'circularised' as the expanding inner rim overtakes the shell. Even here though the appearence of the nebula can be highly fractured and flocculent. However, perfectly round PNe do exist, such as IC 3568 while many faint, extended MASH PNe have uniform surface brightness perfectly circular images (no apparent fractures or blobs). About 20% of MASH PNe have less than 10% departure from apparent sphericity.


Talk by Laura Magrini: Local Group Surveys for Planetary Nebulae

Comment: (Maurizio Busso) Speaking of abundances of intermediate-mass nuclei, Ne can be modified by large production of 22Ne in thermal pulses; any Ne enhancement you may find in PNe is certainly 22Ne locally produced by the parent AGB star via 14N (alpha, gamma) 18O (alpha, gamma) 22Ne.


Talk by Martin Roth: 3D Spectroscopy—a Powerful New Observational Tool for PN Research

Q: (Dick Shaw) What are the requirements for controlling scattered light in spectrographs where IFUs are used? Observing faint nebulosity near bright emission, with contrast ratios of 100 or 1000, suggests that the requirements are demanding.


Talk by J. A. Lopez


Talk by Ortwin Gerhard: Surveys beyond the Local Group

Q: (Neil Vaytet) How is the calibration of spectra performed for the multislit observations? (wavelength and velocity calibration)


Talk by John Feldmeier: Intracluster Planetary Nebulae

Q: (Magda Arnaboldi) The fraction of intracluster light depends whether you factor in the dynamics of the stars, i.e., whether they are bound or unbound to the nearest giant ellipticals.


Talk by Arsen Hajian: Distances to Planetary Nebulae

Q: (You-Hua Chu) NGC 7026 is a bipolar nebula. Wouldn't the expansions along the pole and the equator be different?

A: Yes, the expansion velocities are different, but one single magnification factor works well for the entire nebula, both along the pole and the equator.

Q: (Richard Shaw) Does your fitting technique work equally well for all morphological types?

Q: (Detlef Schoenberner) The shock-front effect is smaller and less dependent on evolution for the outer PN shell. Have you tried to measure the angular expansion of the shells as well?

Comment: (Detlef Schoenberner) I guess you did not consider the shock-front corrections in your distance comparisons.

Q: (George Jacoby) Have you applied the expansion distance method to any PN for which the distance is absolutely well known, such as those in the LMC?

Comment: (Bruce Balick) One of the highly beneficial products of comparing image shapes occurs when the multiepoch residuals show that different parts of the nebula deviate from a "theta dot proportional to radius" expansion. These deviations show areas where strong pressure gradients may be at work, perhaps where the limb of a shell expands differently from the expansion of the bubble inside of it. This information is of interest to people studying the processes that drive nebular evolution.


Talk by David Frew: Towards a New Distance Scale and Luminosity Function for Nearby Planetary Nebulae

Q: (P. Garcia-Lario) What is exactly the criterion used to discard a source as a PN based on the MSX photometry? Compact H II regions and young PNe show exactly the same MSX colours. Are you missing the young PNe in your sample?

A: Most of the uncertain cases had low optical surface brightness (ie. if a PN, they were evolved). Also, if these were true PNe, the MSX 8.3 and 21.3 micron fluxes would have been very low or undetectable. Yet, some were found to be quite dusty, and in combination with other data were assumed to be obscured HII regions (see also Cohen & Parker, 2003, IAU Symp. 209, p.33). Note that the local (1 kpc) sample contains only one young luminous dusty PN, NGC 7027. It seems unlikely that there are other undiscovered objects like it in the solar neighborhood.

Q: (Romano Corradi) Counts of PNe within one kpc from the Sun predict a total number of 28,000 PNe in the whole Galaxy. Including MASH and IPHAS we have/will discover ~3000 PNe. Why is the remaining 90% not detected? Because of extinction?

A: Correct. Even quite modest extinction can hide a highly-evolved, low-surface brightness PN. Note that such PNe numerically dominate the Galactic PN population. For example, the essentially unreddened large spherical nebula PFP 1 (D = 550 pc) has an extremely low surface brightness. It would likely have remained undiscovered if it was, say at twice the distance and affected by one magnitude of interstellar absorption.

Q: (Howard Bond) I wonder if your finding that post-CE PNe tend to have low surface brightness could simply be a selection effect. Most of these binaries have been discovered through photometry of the central stars, and myself and others preferentially chose to do the photometry on those stars lying in low-SB nebulae.

A: We find that post-CE PNe tend to have considerably lower ionised masses on average. But I agree with you that observational biases are present. As you have stated, most of the currently-known post-CE PNe have rather low surface brightness, which has the beneficial effect of making the necessary time-series photometry easier to do. Most of the central stars are also quite bright and have not yet reached the WD cooling track. It will be interesting in the future to see if: (1) high-SB, post-CE PNe, and (2) post-CE nebulae with faint central stars, also have systematically lower ionised masses (assuming we discover them!).

Comment: (Detlef Schoenberner) I am surprised to hear that you have found 105 calibrating PNe. I suggest to break this sample down according to the calibrating method and see how this influences the SB-R relation.

A: There are over 140 PNe with a primary distance estimate in the literature. Some of these were unsuitable as calibrators, while data for other calibrators are from our own and other unpublished data. We are currently investigating how the relation is influenced by different subsets of calibrating PNe.


Talk by Albert Zijlstra: AGB Stars

Q: (Arsen Hajian) Why are shells thin? How do they stay thin? This is especially problematic if the shells are ionized.

A: They are neutral/low ionization.


Talk by Pedro Garcia-Lario: Properties of Post-AGB Objects

Q: (Bruce Balick) One grain returned by Stardust is 20 microns in size and largely olivine. Can AGB stars produce such large grains?

A: Bipolar sources provide a safe haven for forming large dust grains--protection from UV, etc.


Talk by Carmen Sanchez Contreras: Probing Post-AGB Metamorphosis with NIR Adaptive Optics Imaging

Comment: (B. Hrivnak) You fit your models to halos with density steeper than r-2. Volk had found that from fitting SEDs. B___ (?) and I also found that from submm CO observations of PPN; they required steepness of density proportional to r-3 or greater, in agreement with what you find.


Talk by Peter van Hoof: The Real-Time Stellar Evolution of Sakurai's Object

Q: (B. Rubin) How high is the 12C/13C ratio in Sakurai's object?

A: The ratio is 4 +/- 1 (Pavlenko et al., 2004, A&A, 416, L39)

Q: (D. Schoenberner) Can you, please, comment on the recombination timescales and what they are based on?

A: The recombination timescale for O2+ to recombine to O+ is given by 86 (Te/104 K)0.52 (ne/100 cm-3)-1 yr (van Hoof et al., 2000, ApJ, 532, 384, and references therein).

Q: (X. Liu) It is generally assumed that the material ejected by VLTP is C-rich. However, our measurement of the H-deficient knot in Abell 30 using optical recombination lines (Wesson, Liu, & Barlow, 2003, MNRAS, 340, 253) show they are O-rich.

A: The fact that the recent outflows in Sakurai's object are C-rich is clearly indicated by the molecular chemistry. There is ample evidence for this, starting with the early spectra showing C2 absorption bands right up to the recent discovery of HCN and polyyne absorption bands in the Spitzer IRS spectrum (Evans et al., MNRAS, submitted). The very high 13C/12C ratio in these molecules shows unambiguously that they were formed in the newly ejected material.


Talk by Mudumba Parthasarathy: Spectroscopic Properties of Post-AGB Stars

Q: (Maurizio Busso) At the beginnining you showed an object with anomalous oxygen isotopes, indicative of extreme extra-mixing. Is there any s-element associated? For such extreme extra-mixing I would not expect strong s-process.

A: Cami & Yamamura (A&A, 367, L1, 2001) discovered anomalous oxygen isotopic ratios in the very Fe-poor ([Fe/H] = -4.7) post-AGB star HR 4049. CNO elements in this star do not show such extreme underabundances. Takeda, Parthasarathy, Aoki et al. (PASJ, 54, 765, 2002) made a detailed analysis of high resolution and high signal to noise ratio spectrum of the post-AGB star HR 4049 obtained with the Subaru 8-m telescope. They have not detected s-process elements in the spectrum of HR 4049, which is in agreement with your explanation.


Talk by D. A. Garcia-Hernandez: Metallicity Effects in the Chemical Evolution from AGB Stars to PNe

Q: (Maurizio Busso) In those objects rich in Rb and with no other s-element seen, can you measure Mg isotopes? You should find enhanced 25Mg and 26Mg

A: It is true that we should find enhanced 25Mg and 26Mg in these stars as a consequence of the activation of 22Ne as a neutron source. Unfortunately, from the optical spectra is not possible to measure Mg isotopes.

Q: (Kevin Volk) Are all your OH/IR stars which have been analysed in the inner Galaxy? Talking about the "Galaxy" vs. "The Magellanic Clouds" is misleading when there is a large range of metallicity with radius in the Galaxy.

A: The OH/IR stars analysed are mainly members of the Galactic disk population. Galactic AGB stars (i.e., the C-rich AGB stars studied so far) in the Galactic disk have nearly solar metallicities.


Talk by Maurizio Busso


Talk by N. C. Sterling: The Abundances of Light Neutron-Capture Elements in Planetary Nebulae

Q: (Sun Kwok) With the new generation of near infrared spectrometers on 8-10 meter telescopes, are there other s-process elements further down in the periodic table whose fine-structure lines can be detected?

Comment: (Kevin Volk) This is a comment in response to Sun Kwok's question about finding more s-process elements via NIR spectroscopy. I have tried a few times to get time for a deep NIR line survey of a few PNs, so far the TACS have not given time but we are still trying.

Q: (Bruce Balick) Have you considered whether n-rich enriched outflows have been polluted by ancient, unenriched matter ejected earlier by the star?

A: No.


Talk by Falk Herwig: Central Star Evolution

Q: (Mike Barlow) For newly enriched material that is mixed up to the surface, do the models currently predict that the cells of enriched material should get completely mixed, to yield homogeneous abundances, or can pockets of enriched material survive into the mass loss outflows?

Q: (Detlef Schoenberner) The uncertainty of mass determination from evolutionary tracks does not include metallicity effects: it is well known that the luminosity and envelope mass depend somewhat on metallicity. Do you have an estimate of this additional uncertainty?

Q: (Orsola De Marco) Known born-again star Sakurai has a much higher He abundance than born-again star V605, which has 1/2 C, 1/2 O (by mass). Should we believe that Sakurai will evolve into V605?

Q: (Maurizio Busso) You mentioned the fact that uncertainties in reaction rates (especially for 14N(p,gamma)) affect dredge up. Is this so despite the recent, precise measurements of this rate?

A: Yes. Without this recent improvement the combined error would be more like a factor of 3.


Talk by Orsola De Marco: Binary Central Stars

Comment: (Roberto Mendez) Visual binaries complicate the issue; the components evolve separately, but each of them could be an undetected binary... Manuel's question below has the same point.

Q: (Manuel Peimbert) Recent results indicate that about 30% of stars with subsolar masses are binaries and you maintain in your talk that of G main sequence stars, about 50% are binaries. What are the binary fraction of A and F stars? Which is the fraction of stars that are too far away to affect the morphology of the PN?

A: The binary fraction of solar-type stars from Duquennoy & Mayor (1991) is about 50%, although they also looked at late F stars, not just G. The fraction of more massive main-sequence stars is higher, although probably not much more than about 65-70% (REF). If so, then the number of PNe from common envelope interactions would be a little larger than we have determined, since most PNe in the galaxy today come from main sequence stars with masses ~1.2-1.3 solar masses.

The maximum separation to affect the PN morphology is about 10 AU (Gawryszczak et al. 2002, A&A, 385, 205). So the visual central star binaries in my list are unlikely to have affected the morphology of their PN. Of course the fact that these PN have distant companions does not preclude them from having a close one as well (there are many main-sequence triple systems; see Tokovinin, Thomas, Sterzik, & Udry 2006, A&A, in press, astro-ph/0601518).

In our population synthesis simulation to predict the birthrate of PNe from common envelopes only we take all these results into account.

References:

Y. Debernardi, IAUS, 200, 161, 2000: finds 160 multiple systems of 295 observed in Am stars (A or early F types with chemically peculiarities). This results in 54+/-6%, but it is thought that these Am stars might be biased toward a higher binary frequency.

M. Sterzik & R. Durisen, RMxAA, 21, 58, 2004: A good reference of the binary frequency quoting from several papers from brown dwarfs through B-type stars. It has a really good figure with mass of primary in log scale on the x-axis and multiplicity fraction on the y-axis and fairly good power-law model through 10 references of binary frequencies.


Talk by Rolf Kudritzki: Atmospheres and Winds of Central Stars

Q: (Orsola De Marco) Can a close companion (mass between 0.4 and 0.6 solar masses) at a few stellar radii "mess up" the mass-Vinfinity-mass-loss relations assumed for single stars? Would we not expect higher mass loss for the same mass? (By the way, 1 star you analyzed, NGC 6826, is a close binary, and another, He 2-131, is a suspected close binary).


Talk by Helge Todt: Revised Element Abundances for WC-type Central Stars

Q: (Roberto Mendez) Do you find any discontinuity or change or jumps in Teff between WC8 and WC4?

A: Yes. [WCE] stars are all hot (T* of 140,000 K, typically), while [WCL] form a sequence from 20,000 K to 80,000 K.

Q: (Orsola de Marco) [WCL] might NOT have any H (De Marco et al. 1997; De Marco & Crowther 1998). Also the C, O, He abundance discrepancy between [WCL] and [WCE] might not be as severe as stated (see review of WC CSPN from last meeting 2003).

A: The figure with abundances which I have shown includes your results from line-blanketed analyses. We have re-done the [WCE] analyses with most recent models. The revisions are minor, and we feel that the abundance discrepancy is still significant. To be sure about hydrogen in some of the [WCL], one would need better spectroscopic observations.

Q: (Miriam Pena) It is a comment to the suggestion that WELS could fill the gap between [WC] late and [WC] early. Although temperatures in WELS are inbetween those of [WC] late and [WC] early, the kinematics of PNe around WELS are similar to PNe with non [WC] stars. WR-PNe show larger expansion velocities than PNe around WELS and normal CS, indicating that WELS are not part of the [WC] family (reference: Medina et al. 2006, Rev Mex. Astron. Astrof., Vol. 42).

A: I would agree. The stellar wind properties of WELS are also not intermediate between [WCL] and [WCE] - their winds are very thin and very fast.


Talk by Thomas Rauch


Talk by Steven Kawaler: Asteroseismology of White Dwarfs, PN Central and Post-AGB Stars

Q: (Detlef Schoenberner) All your examples of pulsating central stars are H-poor. What happens to normal, H-rich central stars?

We need Steve's reply.


Talk by Deborah Mitchell: The Kinematics and Morphologies of Planetary Nebulae with Close-Binary Cores

Comment: (Sun Kwok) Sp 1 is the perfect illustration that without spectroscopic kinematic information, there is no point classifying the morphology of planetary nebulae.

Reply: I agree with this comment. Sp 1 appears to be an almost perfect ring when seen on the plane of the sky, and it would thus be classified as a spherical nebula based only on its observed morphology; however, the kinematic data reveal that this nebula is actually a tube-like structure viewed pole-on. Kinematic data is an essential complement to deep images of PNe in order to accurately determine their true morphological-kinematic structures.

Comments: (Joel Kastner) 1. Suggest looking for near-infrared H2 emission from bipolar PN candidates. Kastner et al. (1996) showed H2 traces bipolarity. 2. Also suggest looking for diffuse X-ray emission associated with energetic shocks resulting from 700 km/s polar jets in Abell 63.

Reply: We would like to obtain X-ray observations of both Abell 63 and all other PNe with known close-binary central stars to look for evidence of high-speed outflows.

Q: (Raghvendra Sahai) How did you decide on the jet temperature? Are the simulations sensitive to the jet temperature? I would expect that the kinetic energy of the jet is the most important physical parameter for the simulations.

A: The jet temperature was governed by the internal Mach number of the jet. It was found that a jet temperature of approximately 50,000 Kelvin produced the structure which most closely resembled the lobes observed in Abell 63. Varying the internal Mach number had a large effect on the final jet structure. A lower Mach number and hence higher temperature created a less-collimated jet.


Talk by Harriet Dinerstein


Talk by Martin Guerrero


Talk by Detlef Schoenberner: Modeling the X-ray Emission of Planetary Nebulae

Q: (J. Kastner) The WR central star BD+30° 3639 has large Lx and low Teff, so doesn't seem to fit to your models. Why?

A: Our model simulations are restricted to hydrogen-rich compositions only. Because the hydrogen-deficient WR central stars are known to have stronger stellar winds, we expect also larger X-ray luminosities for such hydrogen-deficient models, hopefully in close agreement with the observational findings you mentioned.

Q: (M. Peimbert) Have you computed also the expected emission spectrum produced in the 2 x 104 to 1 x 105 K temperature region between the contact discontinuity and the rim?

A: Since we were interested in the X-ray emission, we set a lower temperature boundary of 1x105 K in our computations. We can also compute the emission from the layers with 2 x 104 to 1 x 105 K if this is wanted.


Talk by Motohide Kokubun


Talk by Joel Kastner


Talk by Joseph Hora


Talk by Jeronimo Bernard-Salas: Infrared Spectroscopy of Planetary Nebulae, Including Spitzer

Q: (Harriet Dinerstein) What about the sulfur anomaly?

A: (Karen Kwitter) There are 2 separate issues: the solar sulfur abundance, S/H, which has recently been revised downward, is still above the mean of PNe. The more interesting issue is the ~0.5 dex offset of PN S/H values below the trend line for H II regions and blue compact galaxies, when plotted vs. O/H (see Henry, Kwitter & Balick 2004). The same plot but with Ne/H shows a tight correlation that PNe follow closely. Our S/H were determined using S+, S++ and a model-derived icf for S+3. Even when we examine the published ISO S/H values, calculated using observed [S IV] 10.5 micron fluxes for 10 objects in our sample, we find that the situation improves slightly, but the sulfur anomaly still remains.

Q: (Zijlstra) The chemical pathway for making benzene requires a degree of ionization in a highly obscured region. Do you see any indications for special environments needed for benzene to form?

A: (Bernard-Salas) Both AFGL 618 and SMP LMC 11 are clearly heavily obscured, but I don't see why ionization would be critical for the chemical formation of benzene. In both objects, the [Ne II] line at 12.8 microns and other low-excitation optical lines have been measured but this relates to the ionization of the gas-phase. Concerning the chemical ionization we know that benzene is also seen in cold AGBs. There have been some models for benzene formation using shock chemistry where they localize the formation of benzene and the acetylenic chains in the interaction of the fast wind with the AGB wind. Perhaps indeed this shock requires a certain level of ionization, but this is just one particular model. I think it may be debatable whether you need to ionize the benzene precursors, but the fact is that we do see them.

Q: (Dinerstein) Does Spitzer have the sensitivity to measure H2 lines in PNe?

A: (Bernard-Salas) Yes, for instance we detect the H2(S2) line at 12.28 microns in M1-42 using the high-resolution modules, SH and LH, with only 48 seconds of observing time. The only thing to remember is that the high-resolution modules cover the range between 10 and 37 microns, and therefore the H2 S(3), S(5), and S(7) lines must be measured in the SL module, which has lower resolution (but also higher sensitivity) and the H2 lines may be blended with other features in the spectrum.

Q: How well can you compare the neon abundance in PNe with the solar value since this value is not from the solar photosphere?

A: (Bernard-Salas) Indeed there are no neon lines in the solar photosphere, and the solar neon abundance we have compared to has been derived using the measurements from the coronal lines by Feldman & Widing (2003). One can turn the argument around and say that neon is probably the element for which we have more accurate abundances since we have information on most of the important stages of ionization, missing only Ne IV, and its abundance compares very well to solar. It is then likely that this solar neon abundance is right.


Talk by Eric Lagadec


Talk by Valentin Bujarrabal: Submillimeter- and Millimeter-wave Molecular Data on Planetary Nebulae and Post-AGB Objects

Q: (M. Peimbert) How accurate are the molecular masses due to the conversion factor
between the CO content and the H2 content?

A: The 12CO relative abundances are quite well measured in AGB circumstellar envelopes, ranging between about 8 x 10-4 (C-rich objects) and 3 x 10-4 (O-rich stars). The 12CO/13CO abundance ratio varies, in the objects in which it has been studied, between about 10 (in some O-rich stars) and 40 (C-rich stars). So the 13CO relative abundance is expected to vary within 1-3 x 10-5. We can assume that these abundances are similar in young PNe, since the material we probe was mainly ejected during the AGB phase, provided that photodissociation is not relevant. So, we do not expect errors larger than a factor 2 due to the abundance assumed, except in regions/phases in which photodissociation is important, then the actual abundance could be much smaller.

Q: (S. Kwok) You mentioned that there are molecular outflows in both the equatorial and polar directions. Can you summarize the relative velocities and mass-loss rates of the two components?

A: I think we can classify the 'equatorial' flows in PPNe in two classes: A: Those that share the dynamical properties of the late AGB flows (mass loss rates higher than 10-4 solar mass/yr, total masses of 0.05-0.3 solar mass, expansion velocities of about 10 km/s). They form in general disk-like structures, not always very flat. They are probably the remnants of the AGB shells that have not been accelerated. Examples: M1-92, CRL618, M2-56. B: Those that are similar to the fast bipolar flows often found in the polar direction. They have total masses of about 0.05 solar mass and velocities of about 50 km/s (note that polar flows can be more massive and faster). These outflows are elongated and not always exactly placed in the equatorial plane; they could be jets along 'secondary' axes. Examples: Frosty Leo, CRL2688.

Q: (R. Corradi) From your talk, I had the impression that a good number of proto-PNe have a significant neutral mass, of the order of 1 solar mass. This would point to relatively large mass progenitors, suggesting that it would be interesting to compare the distribution of the total (central star + nebular) masses of the sample of known proto-PNe with the expected mass distribution of PNe progenitors (from e.g. stellar population synthesis models), in order to check for possible observational biases toward the detection of proto-PNe with relatively massive progenitors. Is such a comparison feasible?

A: Yes, it would be interesting to compare with the expected mass distributions, though difficult, since such initial masses are not well known. It is also obvious that some bias favoring massive objects may be present (but is probably not very strong in the total samples of PPNe, which are quite wide and include sources with various properties); bright objects are always the best studied and we have more data on them. In any case, I note that the distribution in logarithmic scale in my viewgraph may be misleading in this respect. In fact, only one object has a mass larger than 1 solar mass; if we calculate the mean of the molecular masses of the objects in my viewgraph with age < 1000 yr, the result is just 0.5 solar mass. So the typical total mass (even in this reduced sample of very well studied sources) would be < 1.5 solar masses.


Talk by Manuel Bautista


Talk by Xiaowei Liu: Optical Recombination Lines as Probes of Conditions in Planetary Nebulae

Q: (Kevin Volk) How can one explain the existence of H-poor gas in H II regions?

A: (Y. G. Tsamis) In the case of H II regions one could appeal to the presence of incompletely mixed SNR ejecta within the nebula. Our recent paper on a 30 Doradus dual-abundance model discusses just that (Tsamis and Pequignot 2005, MNRAS).

Q: (Dana Balser) You mention that 10% of PNe have abundance discrepancy factors (ADF) of > 10. Are there any H II regions with values this large?

A: (Xiaowei Liu) There is one object with an ADF of ~ 6 but this is very uncertain. Typically ADF ~ 2 for H II regions.


Talk by Manuel Peimbert: Temperature Fluctuations and Planetary Nebulae Abundances

Comment: (Bengt Gustafsson) I do not think that the galactic evolution argument is very strong. After all, these models of chemical evolution are based on yields, being however very uncertain. In principle, one should get yields from PNe by observations of their C abundances, instead. We also have to worry about whether PNe are really representative for single intermediate mass stars.

Response: I agree with you that the C yields for intermediate-mass stars are uncertain. Carigi et al. (2005) presented models of Galactic chemical evolution for eleven different sets of yields, and only two of them provided reasonable fits not only to the C/H values for PNe derived from recombination lines, but also to the C/H and O/H Galactic gradients (slope and absolute value at the solar vicinity) derived from H II regions, and to the observed solar values as representative of the ISM 4.5 billion years ago. I also agree that the presence of a close companion might affect the yields and winds of IMS.

Q: (M. Barlow) An important issue is whether one should adopt recombination line or forbidden line abundances for the average PNe (i.e., leaving aside the very large ADF objects). The temperature fluctuations method effectively adopts the recombination line abundances, which for the average PN are about a factor of two higher than the forbidden line abundances. For PNe the mean recombination line abundance agrees with that measured for the Sun (Allende-Prieto et al. 2001), whereas the mean recombination line O-abundance is twice solar. Is this a problem?

A: I think that it is an important difference and that the recombination value might provide us with an important observational constrain. The difference between the solar value and the recombination lines one should be studied further and might be the result of many causes. I will mention four:
     a) From Galactic chemical evolution models by Carigi et al. (2005) it is found that the increase in the C/H and O/H values since the Sun was formed amounts to 0.29 dex and 0.13 dex, respectively. If the average PNe progenitors have masses around 2 solar masses, their chemical composition should be closer to that of the present day ISM values than to that of the Sun.
     b) From observations it follows that a small fraction of H has been converted into He, decreasing the C/H and O/H values by about 0.04 dex.
     c) Some stellar evolution models of intermediate mass stars predict small increases in the O/H ratio, in some cases as high as 0.2 dex. We need more observations of the O/H abundances from central stars of PNe to provide us with observational restrictions for models of stellar evolution.
     d) There is still the open problem of the difference between the photospheric abundances of the Sun and those predicted from solar seismology. This difference requires an increase of the solar opacity predicted by the photospheric abundances of about 0.1 to 0.15 dex.


Talk by M. Otsuka


Talk by Yiannis Tsamis: Unravelling the Chemical Inhomogeneity of PNe with VLT FLAMES Integral-Field Unit Spectroscopy

Q: (Kevin Volk) Were your IFU spectra corrected for extinction since this was not mentioned in your slide summarizing the data reduction?

A: Yes, they were corrected in the usual manner.

Q: (Manuel Peimbert) Is there a simple relation between the ADF discrepancy and the distance from the central star?

A: There is a trend showing that the ADF increases towards the CS. It is hard to say if there is a simple relation. We are looking into it. A complicating factor is that it seems that the ADF is larger at lower surface brightness patches in a PN.


Talk by Roberto Costa


Talk by Bengt Gustafsson


Talk by Barbara Ercolano


Talk by Wouter Vlemmings


Talk by P. J. Huggins: The Formation of Globules in Planetary Nebulae

Q: (Detlef Schoenberner) What is known about the radial expansion speed of the globules?

A: The line-of-sight velocities of about fifty individual globules of the inner part of the inner ring of NGC 7293 have been measured by Meaburn et al. (1998, MNRAS, 294, 201). The de-projected expansion velocity is about 19 km/s (this corrects an arithmetical error in their paper). The expansion velocity from CO farther out in the inner ring is about 29 km/s (Young et al. 1999, ApJ, 522, 387). The two numbers are probably consistent because the values are roughly in proportion to the projected distances from the central star.

Q: (Bengt Gustafsson) Is the magnetic stabilization as active in the 3D case?

A: For the case of a single interface, there are 2-D and 3-D simulations reported by Jun et al. (1995, ApJ, 453, 332). For the more relevant case of a thin shell, I am not aware that detailed simulations have been carried out. One can imagine that in 3-D there may be a tendency to push to smaller wavelengths transverse to the direction of the field, as there is no tension force in that direction. However, if the field has a disordered component, then the 2-D and 3-D growth rates are likely to be similar.


Talk by Romano Corradi: Macrostructures and Microstructures in Planetary Nebulae

Q: (V. Bujarrabal) Do you think that the "rings" and "arcs" often detected in AGB circumstellar envelopes are the precursors of the similar structures seen in the haloes of PNe?

A: Yes, they are. In Corradi et al. (2004, A&A, 417, 637), we showed that the spacing between rings/arcs in proto-PNe is significantly smaller than in PNe, but this is expected due to a slow merging, with time, of the hydrodynamical waves that are thought to cause the formation of the rings.


Talk by Matthias Steffen: Hydrodynamical Interpretation of Basic Nebular Structures

Q: (G. Garcia-Segura) This was supposed to be a review, and Dr. Villaver did a whole thesis about this subject, published in ApJ 2002, and you did not mention anything about her work.

A: I'm sorry for not mentioning her work. I decided to present the more recent results in some detail, and felt safer to refer mainly to the work I am more familiar with. But I accept your criticism. I should have mentioned her work in my talk, and I will do so in the written version for the proceedings.

Q: (B. Balick) Please comment on why some rims are thick and others are thin, and what this tells us about the energy changes of the wind energy.

A: The properties of the rim depend indeed mainly on the wind of the central star. We have recently used a modified wind model based on Pauldrach et al. (2004) and compared the results to those of models based on the Pauldrach et al. (1988) wind model. According to these simulations, a thin rim indicates that the power of central star wind increases steadily with time. The rim becomes broader, and the density gradient becomes positive, after a temporary decrease of the wind power.

Q: (M. A. Guerrero) Actually, the thermal pressure of the gas in the hot bubble is lower than the thermal pressure of the rim, thus suggesting back-filling of the central cavity and thickening of the rim.

A: Yes, that's what happens whenever the energy supply to the hot bubble decreases, temporarily or in the later stages of evolution, when the luminosity of the central star diminishes as it cools down to a white dwarf.


Talk by Adam Frank


Talk by Guillermo Garcia-Segura


Talk by Richard Shaw: Properties of the Magellanic Cloud Planetary Nebulae

Q: (M. Peimbert) The gaseous [ionized] mass of Type I PNe is expected to be larger than that of other types; this was found to be the case for some well observed objects in the Galaxy. Have you tried to determine the gaseous mass of the MCPNe to test this expectation?

A: We have not yet fully addressed this question, but a preliminary look suggests that there are at least some PNe classified as round or elliptical have substantial ionized masses (in excess of 0.4 solar mass), and there are some bipolars with very modest masses (less than 0.2 solar mass). We need to estimate the masses more carefully, and take into account such effects as the nebular filling factors, etc.

Comment: (S. Torres-Peimbert) It would also be important to try to find out if there is a correlation between CS mass and nebular mass.

Response: Yes, such a correlation might be expected. However, if the nebulae that surround the most massive central stars are never fully ionized (because these stars evolve so quickly to low luminosity, as is predicted by recent hydrodynamical models), then accounting accurately for the neutral material will be very important. On the other hand, if the mass in the extended haloes of well-ionized nebulae (as found by Corradi et al.) contains substantial material swept up in the surrounding ISM, as the Villaver et al. 2002 models suggest, it is not obvious how to correct for that.


Talk by Letizia Stanghellini


Talk by Michael Richer: Properties of Planetary Nebulae in Other Galaxies

Comment: (Manuel Peimbert) According to galactic chemical evolution models, the bulge is formed before the disk. Therefore, the progenitor stars of PNe in the bulge are older and less massive than those of PNe in the disk. These considerations might have something to do with the larger expansion velocities observed for bulge PNe.

Response: This might well be the case, though currently it is impossible to provide a definitive answer. At least the work of Villaver et al. (2002, ApJ, 581, 1204) indicates that the relation between progenitor mass and expansion velocity, particularly while the resultant PNe are bright, is not necessarily a monotonically increasing function of progenitor mass. (The same may also be true of the work of Schoenberner and colleagues, though it is more difficult to tell from their papers.) Your suggestion of higher gravities and the resulting larger wind terminal velocities may well play a part, but data are currently not very abundant on these topics as far as I am aware.

Comment: (Eva Villaver) The Pauldrach et al. results on winds driven by resonance lines have a dependence upon metallicity. The wind during the post-AGB phase will have higher velocities for the higher metallicity, and you might expect higher velocities to push the nebular shell more efficiently as well. Have you considered whether the metallicity effect might explain the differences in expansion velocities?

Response: The clearest evidence for a difference in expansion velocities among PNe arising from different stellar populations occurs when comparing PNe in the bulge and disk of M31. From the evidence available (Jacoby & Ford 1986, ApJ, 304, 490; Richer et al. 1999, A&AS, 135, 203; Jacoby & Ciardullo 1999, ApJ, 515, 169; Roth et al. 2004, ApJ, 603, 531), the PNe in the bulge and disk of M31 have similar abundances, so it is not clear that metallicity will play an important role concerning differences in the kinematics. It is curious that including data for other galaxies weakens the M31 result, so we have more work to do to understand whether metallicity might not play a role, given that most of the other galaxies are more metal-poor than M31's bulge or disk. Indeed, if metallicity played the role these models suggest, adding PNe from more metal-poor, often star-forming galaxies to the data available for PNe in M31 does not produce an even greater discrepancy between the kinematics of PNe from young and old progenitor populations, so it is surprising that the result is the opposite. Basically, though, it is important to remember that, where we find a difference, the difference is small, even less than the dispersion within the samples involved. Since we are observing young planetary nebulae (those are the ones that are brightest, e.g., Jacoby 1989, ApJ, 339, 39; Stasinska et al. 1998, A&A, 336, 667), it is not clear how much effect the post-AGB wind phase has had upon the result of the AGB mass loss. Observing more evolved PNe might reveal more clearly a metallicity effect.

Comment: (Detlef Schoenberner) Based upon our study of the structure and kinematics of galactic PNe, expansion velocities based upon the FWHM are not a representative measure of the expansion speed. You will miss a large portion of the ionized mass which expands with higher speeds.

Response: It is important to remember that we have spatially-unresolved data in [O III] for young planetary nebulae. For spatially-unresolved observations, you do expect that the FWHM should give you a good measure of the velocity for most of the mass (e.g., Gesicki & Zijlstraa 2000, A&A, 358, 1058). It is worth noting, though, that our adoption of the FWHM as our measure of the kinematics is primarily pragmatic: statistically, the line profiles we observe in bright extragalactic PNe have a gaussian shape. In that case, a FWHM may be converted into a velocity width at any other intensity level in a straightforward manner. Doing so will not change the fundamental result, that the expansion velocities in PNe in all galaxies observed so far are similar, since a change in definition will affect all data similarly. Furthermore, we have attempted to understand which kinematic components our observations of extragalactic PNe miss. Our experiments with bright PNe in the Milky Way bulge, where the photon statistics allow us the luxury of studying their spatially-unresolved line profiles in detail, indicate that a gaussian shape represents typically at least 90% of the flux in the line profile. Also, for the bright PNe in the Milky Way bulge, the kinematics in [O III] and Halpha are very similar, so, again, it would seem safe to assume that the kinematics observed in [O III] are representative of most of the mass. Therefore, given the limited signal-to-noise for our observations of extragalactic PNe, it would be surprising if some kinematic information were not lost, but our efforts so far to determine what is missed indicate that the loss is relatively small. On the other hand, I can well imagine that this might not be the case for much more evolved PNe or for observations in low ionization lines, such as [N II], and that may be the root of the difference between our results and yours (Schoenberner et al. 2005, A&A, 431, 963).


Talk by Robin Ciardullo


Talk by Eva Villaver: How PN Shells Interact with Their Local Environment

Q: (M. Steffen) At intra-cluster densities of 10-4 particles per cubic centimeter (and temperatures of 107 K), the mean free path of the gas particles must be quite large, possibly larger than the PN you model. In that case, the hydrodynamical approximation must break down. Have you checked that the hydrodynamical approach is still valid (Knudsen Number << 1) even under intra-cluster conditions?

We need Eva's answer.


Talk by Magda Arnaboldi

Talk by Aaron Romanowsky: Planetary Nebulae as Mass Tracers in Galaxies

Q: (Robin Ciardullo) There is an H I ring about NGC 3379. What constraints does that give for dark matter?

A: NGC 3379 is a rare case of an elliptical galaxy where an H I mass constraint is available (Schneider 1985). It implies M/LB = 27 at 100 kpc, which implies dark matter, but surprisingly little. Somebody needs to re-observe this gas "ring" with a modern radiotelescope to investigate its orbital properties.

Q: (Shuji Deguchi) Is the number of PNe consistent with the number of AGB stars in these galaxies? is there any comparison available?

A: Most of the galaxies studied are too distant to directly answer that question. There are HST data on NGC 3379 which could be useful. Most relevant would be M31, where there are now enormous datasets available of both PNe and resolved AGB star counts (e.g. Ferguson et al. 2002)


Talk by Roberto Mendez: High-Quality Slitless Radial Velocities of Extragalactic Planetary Nebulae with Subaru and FOCUS

Q: (Manuel Peimbert) Is it possible to measure the ratio of PN number to luminosity in the outer regions of galaxies?

A: Very difficult because of the very low surface brightness of the stellar population beyond 3 effective radii.


 

 

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