Number Of Planetary Nebulae Research Articles

Newly discovered Planetary Nebulae population in Andromeda (M31): PN Luminosity function and implications for the late stages of stellar evolution

AbstractStars with masses between ∼0.7 and 8 M⊙ end their lives as Planetary Nebulae (PNe). With the MegaCam at CFHT, we have carried out a survey of the central 16 sq. degrees of Andromeda (M31) reaching the outer disk and halo, using a narrow-band [OIII]5007 and a broad-band g filter. This survey extends previous PN samples both in uniform area coverage and depth. We identify ∼4000 PNe in M31, of which ∼3000 are new discoveries. We detect PNe down to ∼6 mag below the bright cut-off of the PN luminosity function (PNLF), ∼2 mag deeper than in previous works. We detect a steep rise in the number of PNe at ∼4.5 mag fainter than the bright cut-off. It persists as we go radially outwards and is steeper than that seen in the Magellanic clouds. We explore possible reasons for this rise, which give insights into the stellar population of M31.

Planetary nebulae as kinematic tracers of galaxy halos

AbstractThe kinematics and dynamical properties of galaxy stellar halos are difficult to measure, given the faint surface brightness that characterizes these regions. Gas-rich systems such as spiral galaxies can be probed using the radio Hi emission. Early-type galaxies contain less gas, therefore alternative kinematic tracers need to be used. Planetary Nebulae (PNe) can be easily detected far out in the halo thanks to their bright [O iii] emission at 5007 Å. It is therefore possible to map the halo kinematics also in early-type galaxies, typically out to 5 effective radii or beyond. Thanks to the recent spectroscopic surveys targeting extra-galactic PNe, we can now rely on few tens of galaxies where the kinematics of the stellar halos are measured. I will discuss the most important results: (a) the relation of the stellar surface brightness and the PNe number density; (b) the velocity and velocity dispersion two-dimensional fields; (c) the radial profiles of angular momentum; and (d) the relation between the derived kinematics physical properties of the host galaxies.

Probing the kinematics of early‐type galaxy halos using planetary nebulae

AbstractWe present first results of a study of the halo kinematics for a sample of early type galaxies using planetary nebulae (PNe) as kinematical tracers. PNe allow to extend up to several effective radii (Re) the information from absorption line kinematics (confined to within 1 or 2Re), providing valuable information and constraints for merger simulations and galaxy formation models.We find that the specific angular momentum per unit mass has amore complex radial dependence when the halo region is taken into account and that the halo velocity dispersion is related to the total galaxy luminosity, isophotal shape, and number of PNe per unit of luminosity. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Intracluster Planetary Nebulae in the Hydra I cluster

AbstractUsing the Multislit Imaging Spectroscopy (MSIS) technique at the FORS2 spectrograph on VLT‐UT1, we have identified 60 Intracluster Planetary Nebula (ICPN) candidates associated with the Intracluster Light (ICL) in the central region of the Hydra I cluster. Hydra I is a medium compact, relatively near (∼50 Mpc), rich cluster in the southern hemisphere. Here we describe the criteria used to select emission sources and present the evidence for these PN candidates to be associated with the ICL in the Hydra I cluster. We also show, using the luminosity‐specific planetary nebulae number, the α parameter, that the expected number of PNs associated with the stellar population of the central cD galaxy NGC 3311 in the cluster is close to the number of PNs detected. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

The Local Group Census: searching for planetary nebulae in IC 1613, WLM and GR8

In the framework of the Local Group Census (LGC), a survey of the Local Group (LG) galaxies above Dec =− 30 ◦ aimed at surveying the populations that have strong emission lines, we have searched for planetary nebulae (PNe) in the low-metallicity dwarf irregular galaxies IC 1613, WLM, GR 8. Two new candidate PNe have been found in IC 1613, one in WLM and none in GR 8. The observations presented in this paper, together with the previous results from the LGC, represent the first step in the study of the PN population in low-metallicity, dwarf irregular galaxies of the Local Group. These observations will be followed by deep spectroscopy to confirm the nature of these objects and to study their physical-chemical properties. We use the observed number of PNe in each LG galaxy to estimate a lower limit to the mass of the intermediate-age population, which is compared with the star formation rate (SFR) of LG dwarf galaxies. These results are in agreement with those from accurate star formation history (SFH) analyses for these small galaxy systems.

Accretion Disks in Pre–Planetary Nebulae

A number of planetary nebulae (PNs) exhibit collimated, high-velocity outflows or jets. These hydrodynamical structures cannot be easily accommodated within the classical models of the evolution of post-asymptotic giant branch stars, and understanding them has become a topical problem in PN research. One way to explain the existence of jets in PNs has been to invoke the presence of accretion disks, which would presumably set the conditions for the collimation and driving of the outflows. This work investigates in detail the type of binary systems that are likely to lead to Roche-lobe overflow (RLOF) and the formation of accretion disks as a consequence of common-envelope evolution, and explores the expected basic physical structure of such disks. The results of the analysis show substantial restrictions on the composition of binary systems that can form a disk upon accretion onto the primary. Typically, it is found that for a primary asymptotic giant branch (AGB) core of 0.6 M☉ and envelope mass of 2-3 M☉, secondaries with M2 0.08 M☉ and initial separation ai 200 R☉ will not lead to RLOF. For systems that do lead to RLOF, this is achieved at orbital separations <2 R☉. We also find that dynamically stable mass transfer from secondaries with M2 0.08 M☉ does not lead to disk formation, since the circularization radius lies below the surface of the AGB core. Only lower mass companions, after a dynamically unstable mass transfer process, may lead to disk formation. Under reasonable simplifying assumptions, we estimate the resulting accretion disk properties and evolution and discuss their potential role in driving collimated outflows.

Excitation processes for the emission of the unidentified IR bands

To our knowledge, no individual polycyclic aromatic hydrocarbon (PAH) molecule has yet been shown to carry all the ubiquitous and closely correlated unidentified IR (UIR) bands. More generally, no IR space observatory (ISO) instrument was able to split these bands into the narrower signatures expected from molecules. Again, the Japanese IRTS satellite has shown that the near-IR CH-stretching band observed near the galactic plane carries an important aliphatic component alien to aromatic molecules. On the other hand, a number of solid-state, disordered, more or less hydrogenated, carbonaceous materials have been shown to carry all the UIR bands. Moreover, their emission spectrum, computed under thermal equilibrium with typical circumstellar radiation fields, was shown to fit, satisfactorily and in detail, the observed near- and mid-IR spectra of a number of planetary nebulae (PNe) and proto-planetary nebulae (PPNe). However, the interstellar radiation field (ISRF) is not strong enough to heat this solid-state dust to the equilibrium temperatures required for emission observed from the galactic plane and reflection nebulae. Even stochastic heating is insufficient in these cases because nanometric grains are too small to retain the desirable optical properties of the bulk. One way out of this deadlock is to look for other excitation mechanisms. Noting that spatial maxima of UIR emission usually occur in photodissociation regions between ionized and molecular gas maxima, where atomic H is most abundant, we have set up to study the interactions of atomic hydrogen with solid-state carbon surfaces. We consider, in particular, a mechanism in which, upon collision with a grain, the potential energy of recombination carried by an atom is delivered to one of the functional groups which will emit a UIR band. Such an IR chemiluminescence is found to be possible, in principle. A laboratory experiment dedicated to the quest of IR chemiluminescence has been built and is described.

Planetary Nebulae in M31: Abundances, and comparison with bright Planetary Nebulae in the LMC

We have obtained spectra of 28 planetary nebulae in the bulge of M31 using the MOS spectrograph at the Canada-France-Hawaii Telescope. Typically, we observed the [O II] λ3727 to He I λ5876 wavelength region at a resolution of approximately 1.6 å/pixel. For 19 of the 21 planetary nebulae whose [OIII]λ5007 luminosities are within 1 mag of the peak of the planetary nebula luminosity function, our oxygen abundances are based upon a measured [OIII]λ4363 intensity, so they are based upon a measured electron temperature. The oxygen abundances cover a wide range, 7.85 dex &lt; 12 + log(O/H) &lt; 9.09 dex, but the mean abundance is surprisingly low, 12 + log(O/H)–8.64 ± 0.32 dex, i.e., roughly half the solar value (Anders &amp; Grevesse 1989). The distribution of oxygen abundances is shown in Figure 1, where the ordinate indicates the number of planetary nebulae with abundances within ±0.1 dex of any point on the x-axis. The dashed line indicates the mean abundance, and the dotted lines indicate the ±1 σ points. The shape of this abundance distribution seems to indicate that the bulge of M31 does not contain a large population of bright, oxygen-rich planetary nebulae. This is a surprising result, for various population synthesis studies (e.g., Bica et al. 1990) have found a mean stellar metallicity approximately 0.2 dex above solar. This 0.5 dex discrepancy leads one to question whether the mean stellar metallicity is as high as the population synthesis results indicate or if such metal-rich stars produce bright planetary nebulae at all. This could be a clue concerning the mechanism responsible for the variation in the number of bright planetary nebulae observed per unit luminosity in different galaxies (e.g., Hui et al. 1993).

Observational tests of the Interacting Winds Model of Planetary Nebulae

Numerical simulations of the evolution of Planetary Nebulae (PNe) based on the Interacting Stellar Winds models have become highly sophisticated, producing synthetic images and spectra in a number of prominent emission lines at high spatial and spectral resolution. The success of these models in producing synthetic images which closely resemble many observed nebulae is well documented. The number of PNe which have been investigated spectroscopically with good spatial coverage and high spatial and spectral resolution is relatively small and therefore in many cases the synthetic spectra predicted by the numerical models have not been directly compared to observed spectra. Here we consider some recent results from two PNe and compare them to model results.

The hot stellar component in elliptical galaxies and spiral bulges. I - The far-ultraviolet spectrum of the bulge of M31

view Abstract Citations (85) References (57) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS The Hot Stellar Component in Elliptical Galaxies and Spiral Bulges. I. The Far-Ultraviolet Spectrum of the Bulge of M31 Ferguson, Henry C. ; Davidsen, Arthur F. Abstract We present a spectrum of the bulge of M31 from 1850 A to the Lyman limit measured through a 9" X 116" aperture by the Hopkins Ultraviolet Telescope (HUT) during the Astro-1 space shuttle mission in 1990 December. Apart from airglow, no significant emission features are present in the spectrum. A search for stellar absorption features reveals several significant detections, but uncertainties in the interstellar-medium contribution and the temperatures of the stars contributing to the spectrum preclude any definite conclusions about the metallicity of the stellar population. We compare the HUT spectra of the M31 bulge and of NGC 1399, the central giant elliptical in the Fornax Cluster. We find significant differences that are relatively insensitive to the assumptions about extinction. Evidently the stars producing the far-UV upturn in UV-bright galaxies such as NGC 1399 are not just more of the same stars producing the emission in UV-fainter galaxies like M31. We investigate the possibility that the two spectral-energy distributions (SEDs) differ only in the fractional contribution from classical post-asymptotic giant branch (PAGB) stars and in the amount of extinction. We find an acceptable fit to the M31 spectrum for E(B - V) = 0.11 if ~65% of the flux (at ~ 1400A) comes from PAGB stars and the rest comes from stars of the type producing the far-UV emission in NGC 1399. The known PAGB population from optical observations (central stars of planetary nebulae) can account for less than 1% of the total far-UV flux. The pointlike sources recently detected at 1750 A by the HST Faint Object Camera are probably PAGB stars with masses lower than planetary-nebula central stars (thought to be ~0.6 M_sun_). These sources too appear to account for only a small fraction (~15%) of the flux observed by HUT at 1750 A. These results suggest that PAGB stars with still lower masses, which would be fainter than the FOC detection limit for point sources, contribute to the M31 SED. We examine the hypothesis that the UV continuum in both galaxies is dominated by stars in post-horizontal branch (post-HB) phases of evolution, with a distribution of post-HB masses governed by the mean metallicity and metallicity spread of the population. The number of UV photons produced per star increases toward lower mass, while the characteristic temperature of the UV emitting population decreases. In this scenario, the far-UV flux of NGC 1399 is produced mostly by low-mass extreme horizontal branch, post-early-AGB, and/or AGB-Manque stars, while in M31 there is a large contribution from classical PAGB stars as well. We can thus qualitatively explain both the relative fluxes of the UV rising branches in NGC 1399 and M31, and the shapes of their SEDs. This scenario makes a prediction, which we confirm from existing surveys, that the number of planetary nebulae per unit luminosity is anticorrelated with the strength of the UV upturn. It also makes. testable predictions for the far-UV SEDs of low-metallicity ellipticals and the spectral evolution of giant ellipticals. Publication: The Astrophysical Journal Pub Date: May 1993 DOI: 10.1086/172572 Bibcode: 1993ApJ...408...92F Keywords: Elliptical Galaxies; Far Ultraviolet Radiation; Galactic Bulge; Galactic Radiation; Hot Stars; Spiral Galaxies; Ultraviolet Astronomy; Absorption Spectra; Asymptotic Giant Branch Stars; Planetary Nebulae; Spectral Energy Distribution; Ultraviolet Spectra; Astrophysics; GALAXIES: INDIVIDUAL MESSIER NUMBER: M31; GALAXIES: INDIVIDUAL MESSIER NUMBER: M32; GALAXIES: INDIVIDUAL NGC NUMBER: NGC 1399; GALAXIES: STELLAR CONTENT full text sources ADS | data products SIMBAD (3) NED (3) MAST (2) INES (1)

Spectrum and chemical analysis of the double-ring planetary nebula IC 1297

view Abstract Citations (14) References (34) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Spectrum and Chemical Analysis of the Double-Ring Planetary Nebula IC 1297 Aller, Lawrence H. ; Keyes, Charles D. ; Feibelman, Walter A. Abstract The double-ring planetary nebula IC 1297 resembles NGC 7662 in appearance, although it is of much lower surface brightness. What is remarkable is the great strength of the dielectronic recombination O V line. Although this line is seen as a P Cygni feature in a number of planetary nebulae, it is in those instances accompanied by a strong continuum and other easily recognized features of stellar origin. No star is visible on CCD images of IC 1297. Optical region measurements are supplemented by IUE observations. The following logarithmic abundance values are found: log N(He) = 11.065; log N(forbidden C) = 8.6; log N(N) = 8.1; log N(O) = 8.74; log N(Ne) = 8.16; log N(S) = 7.0; log N(Cl) = 5.4; log N(Ar) = 6.2. The nebula shows no dramatic pattern of nucleogenesis events. Publication: The Astrophysical Journal Pub Date: December 1986 DOI: 10.1086/164830 Bibcode: 1986ApJ...311..930A Keywords: Abundance; Line Spectra; Planetary Nebulae; Plasma Diagnostics; Spectrum Analysis; Astronomical Models; Astronomical Spectroscopy; Ultraviolet Spectra; Visible Spectrum; Astrophysics; NEBULAE: ABUNDANCES; NEBULAE: INDIVIDUAL ALPHANUMERIC: IC 1297; NEBULAE: PLANETARY; ULTRAVIOLET: SPECTRA full text sources ADS | data products SIMBAD (5) MAST (1) INES (1)

A comparison of forbidden-line and optical continuum electron temperatures in gaseous nebulae

view Abstract Citations (21) References (21) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS A comparison of forbidden-line and optical continuum electron temperatures in gaseous nebulae. Barker, T. Abstract Photoelectric scanner observations have been made of the Balmer and Paschen discontinuities in several positions in a number of planetary nebulae and the Orion Nebula. Electron temperatures determined from these measurements are shown to be in generally good agreement with those found from forbidden lines; there is definitely no evidence that forbidden-line electron temperatures are systematically higher, as some previous investigations have found. This result suggests that in some studies metal-to-hydrogen abundance ratios in gaseous nebulae have been overestimated by nearly a factor of 2. Publication: The Astrophysical Journal Pub Date: February 1979 DOI: 10.1086/156796 Bibcode: 1979ApJ...227..863B Keywords: Abundance; Electron Energy; Forbidden Bands; Nebulae; Planetary Nebulae; Hydrogen Clouds; Line Spectra; Temperature Measurement; Astrophysics; Electron Temperatures:Gaseous Nebulae; Electron Temperatures:Orion Nebula; Forbidden Lines:Planetary Nebulae full text sources ADS | data products SIMBAD (7)

The rate of formation of white dwarfs in stellar systems

view Abstract Citations (27) References (20) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS The rate of formation of white dwarfs in stellar systems. Hills, J. G. Abstract Consideration of energy conservation permits development of a simple relation between the luminosity of a stellar system and the white-dwarf formation rate in that system. The relation shows that one white dwarf is formed in the Galaxy every 3.9 years; the number of planetary nebulae in the Galaxy is set at 1600. White dwarfs comprise about 1.3 to 3.5% of the mass of galaxies, and about one-fourth of the mass of a typical globular cluster. The number of neutron stars and black holes in stellar systems is estimated by similar procedures. Publication: The Astrophysical Journal Pub Date: January 1978 DOI: 10.1086/155813 Bibcode: 1978ApJ...219..550H Keywords: Luminous Intensity; Star Clusters; Stellar Evolution; Stellar Systems; White Dwarf Stars; Energy Conservation; Galactic Radiation; Globular Clusters; Mass Distribution; Milky Way Galaxy; Neutron Stars; Planetary Nebulae; Statistical Analysis; Stellar Models; Astrophysics; Formation:White Dwarfs; Planetary Nebulae:White Dwarfs full text sources ADS |

On the number of planetary nebulae in our galaxy.

It is found that the contribution to the ionization of the interstellar medium due to planetary nebulae is from one or two orders of magnitude smaller than that due to O stars. The mass return to the interstellar medium due to planetary nebulae is investigated, and the birth rate of white dwarfs and planetary nebulae are compared. Several arguments are given against the possibility that the infrared sources detected by Becklin and Neugebauer in the direction of the galactic center are planetary nebulae. (AIP)