Planetary Nebula Candidates Research Articles

Radio Continuum Observations of Southern Planetary Nebulae Candidates

In an attempt to find new Planetary Nebulae we have short radio continuum observations at 6 cm and 3 cm of 90 PN candidates with the Australian Compact Array. We selected the unidentified objects from the IRAS Point Source Catalogue on basis of their PN colors. Detection of radio continuum emission at the IRAS position almost certainly confirms that these objects are PN, because it indicates the presence of ionized gas. Therefore the 18 detected sources are considered new PN. Because of their high brightness temperatures, they are probably young PN.

Planetary nebulae as standard candles. VII - A test versus Hubble type in the NGC 1023 group

We present the results of an [O III] λ5007 survey for planetary nebulae in the NGC 1023 Group. In all, we detected 143 planetary nebula candidates: 110 in the SBO galaxy NGC 1023 and 33 in the halo of the edge-on Sb spiral NGC 891. Using a statistically complete and homogeneous sample of planetary nebulae and the procedures described in previous papers in the series, we derive distances to these galaxies using the planetary nebula luminosity function (PNLF)

Misidentified OH/IR Stars

AbstractPlots of periods against (25μm – 12μm) colour of OH/IR stars suggest that four IRAS sources, that have been associated with known OH/IR stars, either provide anomalous identifications, or are weak rather than regular variables. It is argued here that only one of these cases is an association error. OH15.7+0.8 and OH37.1–0.8 are the new proto–planetary nebula candidates.

Planetary nebulae as standard candles. V - The distance to the Virgo Cluster

The O III forbiden 5007-A line fluxes of 486 planetary nebula candidates in six early-type galaxies (NGC 4374, 4382, 4406, 4472, 4486, and 4649) in the core of the Virgo Cluster are identified and measured. Following the procedures and calibrations outlined in previous papers in this series, the observed planetary nebula luminosity functions are compared to an empirical model based on the planetary nebulae in M31, and the distances to the galaxies are derived to be 15.7, 14.4, 15.7, 13.9, 14.5, and 14.2 Mpc. These distances exhibit superb agreement with a dispersion of only 0.8 Mpc and suggest that the cluster depth is less than 2 Mpc. Most importantly, the distances are totally uncorrelated with parent galaxy metallicity, color, UV flux, or Hubble type. 76 refs.

The Optical Counterpart of the IRAS Planetary Nebula Candidate 19170+1706

The Optical Counterpart of the IRAS Planetary Nebula Candidate 19170+1706

Planetary Nebulae in Galaxies Beyond the Local Group

Planetary nebulae can be used to estimate the distances to galaxies and to measure stellar dynamics in faint halos. We discuss surveys which have netted a total of 665 candidate planetary nebulae in NGC 5128 (Cen A), NGC 5102, NGC 3031 (M81), NGC 3115, three galaxies in the Leo Group (NGC 3379, NGC 3384, NGC 3377), NGC 5866, and finally, in NGC 4486 (M87). Radial velocities of planetaries in M32 have shown that its halo velocity dispersion is most likely isotropic. Radial velocities of planetaries in M31 show that ∼ 2/3 of the nebulae with projected radii between 15 and 30 kpc are members of a rotating thick disk with slight asymmetric drift, while ∼ 1/3 belong to a slowly rotating halo. Velocities of 116 nebulae in NGC 5128 reveal pronounced rotation and a slowly declining velocity dispersion in the halo out to 20 kpc. The [O III] λ5007 luminosity functions (PNLFs) in NGC 5128, M81, and the three Leo Galaxies have the same shape over the first magnitude. The highly consistent distances derived from the brightnesses of the jth nebula and the median nebula in different fields in the same galaxy and from different galaxies in the same group lend strong support to the suggestion that planetaries are an accurate standard candle in old stellar populations. Comparison of theoretical luminosity functions to the observed PNLFs shows that there is a very small dispersion in the central star masses.

SEVEN NEW PLANETARY NEBULAE IN THE DIRECTION OF BAADE'S WINDOW.

ABSTRACT The authors present seven new planetary nebula candidates that were discovered with interference-filter photographs, and that lie in or near Baade's Window (l = 1°.0, b = -3°.9). Two of them are angularly resolved, and are probably relatively nearby disk objects. All are faint and suffer from high interstellar reddening.

A More Complete Listing of LMC Planetary Nebulae

In an earlier paper by Sanduleak et al. (1978) a listing was given of 102 confirmed and probable planetary nebulae in the Large Magellanic Cloud detected on objective-prism plates taken with the Curtis Schmidt telescope at Cerro Tololo. Subsequently, deeper coverage was obtained on nitrogen-baked Kodak IIIa-J plates plus GG 455 filter exposed for 90 minutes. The thin prism was again used to provide a dispersion of about 1500 Å mm−1 at Hβ and the spectra were unwidened. An additional 25 planetary nebula candidates were found on this new plate material to show the requisite characteristics, i.e. they display (a) a stellar appearance, (b) [OIII] λλ5007, 4959 strongly in emission, and (c) no evidence of a continuum.