scholarly journals Evolution of Planetary Nebulae Envelopes: An Empirical Approach

1993 ◽  
Vol 155 ◽  
pp. 370-370
Author(s):  
V.V. Golovaty ◽  
Yu. F. Malkov
Keyword(s):  
Integral Equation ◽  
Density Distribution ◽  
Radial Distribution ◽  
Empirical Investigation ◽  
Planetary Nebulae ◽  
Symmetric Case ◽  
Radio Continuum ◽  
Spherically Symmetric ◽  
Gas Density ◽  
Approximative Expression

We carried out the empirical investigation of the evolution of gas density distribution in the envelopes of planetary nebulae (PN). For this purpose we analysed the isophotal maps of 10 PN in the lines H alpha, H beta or in the optically thin radio continuum. To obtain the spatial radial distribution of gas density n(r) (where n = n(H)+n(He)) we used Abell's integral equation in the simplest, spherically-symmetric case. We found that n(r) for all PN envelopes in our sample can be described by an approximative expression:

scholarly journals Ionization correction factors from an extensive grid of photoionization models of Planetary Nebulae

1997 ◽  
Vol 180 ◽  
pp. 276-276
Author(s):  
O. Rokach ◽  
V. Golovaty
Keyword(s):  
Density Distribution ◽  
Stellar Wind ◽  
Planetary Nebulae ◽  
Approximate Expression ◽  
Spherically Symmetric ◽  
Correction Factors ◽  
Gas Density ◽  
Elemental Abundances ◽  
Central Stars

Using a new photoionization code PAN (Yu. Malkov et al, this book) we have built a grid of 250 photoionization models for planetary nebulae (PN). The stellar evolutionary tracks for PN nuclei with M∗ = 0.566, 0.598, 0.644 and 0.8M⊙ are taken from the computations of the Blöcker (A&A, 299, 1995). On the L∗ – Teff diagram our grid covers whole region in which the PN nuclei are observed. The spectra of the central stars at λ ≤ 912 Å corresponded to non-LTE model atmospheres (R.E.S. Clegg and D. Middlemass, MNRAS, 228, 1987), corrected for presence of the stellar wind. The nebular shell was assumed to be spherically symmetric, and the profile of the radial gas density distribution in it was taken equal to the empirical approximate expression found from the analysis of isophotal maps of real PN (V. Golovaty and Yu. Malkov, Astron. Zh., 69, 1992). Each model was calculated for three choises of Mshell and each of them for two choises of shell expansion velosity −15 and 30 km/sec respectively. The relative elemental abundances were the same for all models: H:He:C:N:O:Ne:Mg:Si:S:Ar = 10000:1200:5.0:1.0:6.0:0.8:0.3:0.3:0.15:0.04 (by number of atoms).

scholarly journals The Spatial Distribution of Line Ratio O III/O II in High Excitation Planetary Nebulae

1989 ◽  
Vol 131 ◽  
pp. 228-228
Author(s):  
A. Noriega-Crespo ◽  
M. McCall
Keyword(s):  
Spatial Distribution ◽  
Density Distribution ◽  
Charge Exchange ◽  
Planetary Nebulae ◽  
Line Ratio ◽  
High Excitation ◽  
Exchange Coefficient ◽  
Gas Density ◽  
Image Position

Previous attempts to model the integrated line ratio [O III] 5007 A/[O II] 3727 A for high excitation planetary nebulae (Che and Köppen 1983) have suggested that the charge exchange coefficient (k) for the reaction could be 10 times smaller than the predicted theoretical value. The influence of other factors that may contribute to differences in the O III/O II ratio, such as the ionizing spectrum and the nebular gas density distribution, seem to be relatively small in the high excitation nebulae.

scholarly journals A new concept of transonic galactic outflows and its application to the Sombrero galaxy

2016 ◽  
Vol 11 (S321) ◽  
pp. 125-125
Author(s):  
Asuka Igarashi ◽  
Masao Mori ◽  
Shin-ya Nitta
Keyword(s):  
Star Formation ◽  
Density Distribution ◽  
Cold Dark Matter ◽  
Star Formation History ◽  
Dark Matter Halo ◽  
Polytropic Model ◽  
Gas Density ◽  
Galactic Outflows ◽  
Distant Region ◽  
Subsonic Region

AbstractWe study fundamental properties of transonic galactic outflows in the gravitational potential of a cold dark matter halo (DMH) with a central super-massive black hole (SMBH) assuming a polytropic, steady and spherically symmetric state. We have classified the transonic solutions with respect to their topology in the phase space. As a result, we have found two types of transonic solutions characterized by a magnitude relationship between the gravity of DMH and that of SMBH. These two types of solutions have different loci of the transonic points; one transonic point is formed at a central region (< 0.01kpc) and another is at a distant region (> 100kpc). Also, mass fluxes and outflow velocities are different between the two solutions. These two transonic solutions may play different roles on the star formation history of galaxies and the metal contamination of intergalactic space. Furthermore, we have applied our model to the Sombrero galaxy. In this galaxy, the wide-spread hot gas is detected as an apparent trace of galactic outflows while the star-formation rate is disproportionately low, and the observed gas density distribution is quite similar to the hydrostatic state (Li et al. 2011). To solve this discrepancy, we propose a slowly accelerating outflow in which the transonic point forms in a distant region (~ 120 kpc) and the subsonic region spreads across the stellar distribution. In the subsonic region, the gas density distribution is similar to that of the hydrostatic state. Our model predicts the possibility of the slowly accelerating outflow in the Sombrero galaxy. Igarashi et al. 2014 used the isothermal model and well reproduced the observed gas density distribution, but the estimated mass flux (1.8M⊙/yr) is lager than the mass of the gas supplied by stars (0.3-0.4M⊙/yr). Then, we expect that the polytropic model may reproduce the observational mass of the supplied gas (Igarashi et al. 2015). Such slowly accelerating outflows should be distinguished from the conventional supersonic outflows frequently argued in star-forming galaxies.

Water masers as signposts of extremely young planetary nebulae

2017 ◽  
Vol 13 (S336) ◽  
pp. 377-380
Author(s):  
José F. Gómez ◽  
Luis F. Miranda ◽  
Lucero Uscanga ◽  
Olga Suárez
Keyword(s):  
Planetary Nebulae ◽  
Radio Continuum ◽  
Continuum Emission ◽  
Water Masers ◽  
Water Maser

AbstractOnly five planetary nebulae (PNe) have been confirmed to emit water masers. They seem to be very young PNe. The water emission in these objects preferentially traces circumstellar toroids, although in K 3-35 and IRAS 15103-5754, it may also trace collimated jets. We present water maser observations of these two sources at different epochs. The water maser distribution changes on timescales of months to a few years. We speculate that these changes may be due to the variation of the underlying radio continuum emission, which is amplified by the maser process in the foreground material.

scholarly journals Radio Spectroscopy of Planetary Nebulae

1978 ◽  
Vol 76 ◽  
pp. 127-128
Author(s):  
Eric J. Chaisson
Keyword(s):  
Stark Effect ◽  
Principal Quantum Number ◽  
Planetary Nebulae ◽  
Radio Continuum ◽  
Radio Lines ◽  
Ion Temperature ◽  
Radio Recombination Line ◽  
Ngc 7027 ◽  
Optical Line ◽  
Ion Impact

The H110α radio recombination line has been observed toward the planetary nebulae NGC 7027, IC 418, and NGC 6543 in order to ascertain the physical characteristics of the bulk nebular gas. The observations of NGC 7027 confirm the earlier findings of Chaisson and Malkan (Ap.J., 210, 108, 1976) and Churchwell, Terzian and Walmsley (A&A, 48, 331, 1976) who reported evidence for a substantial increase in linewidth with principal quantum number. Attributed to electron-ion impact broadening (Stark Effect), the observations imply an electron density Ne ≃ 50,000/cm3. The LTE-derived electron-ion temperature Te ≃ 18,000°K agrees reasonably well with most radio-line analyses, as well as with previous analyses of the radio continuum, of forbidden optical line ratios, and of optical recombination lines and their associated continuum. IC418's HllOa line is also wider than radio lines observed at higher frequencies, suggesting a Stark Effect consistent with Ne < 20,000/cm3; NGC 6543 shows no appreciable line broadening, providing an upper limit to the density Ne < 10,000/cm3. The LTE-derived Te values for IC 418 and NGC 6543 are approximately 14,000 and 7000°K, reasonably consistent with those found by other techniques. On the basis of this and other recent studies, I suggest that the bulkemission in the Hnα recombination lines observed to date, 77 < n < 111, can be explained by a simple model of optically thin planetary nebular gas largely homogeneous in temperature and in density, and only slightly removed from LTE.

scholarly journals Simulation of the gas density distribution in the accelerator of the ELISE test facility

2020 ◽  
Vol 91 (1) ◽  
pp. 013511
Author(s):  
M. Siragusa ◽  
E. Sartori ◽  
F. Bonomo ◽  
B. Heinemann ◽  
G. Orozco ◽  
...  
Keyword(s):  
Density Distribution ◽  
Test Facility ◽  
Gas Density
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