skip to main content
OSTI.GOV title logo U.S. Department of Energy
Office of Scientific and Technical Information

Title: The open cluster NGC 2818 and its associated planetary nebula

Abstract

New CCD UBV photometry of the open cluster NGC 2818 central region indicates that previously derived values of distance and reddening for the cluster have been considerably overestimated, leading to erroneous values for the physical parameters of its associated planetary nebula (PK 261 + 8.1 deg). The analysis of the new data yields E(B-V) = 0.18 + or - 0.03 and V(0)-M(v) = 11.80 + or - 0.2 (2.3 + or - 0.2 kpc) for the cluster's color excess and distance modulus, respectively. If cluster membership is assumed for the planetary nebula, the above estimates result in physical parameters that compare better with those of a typical planetary nebula in the Galaxy and the Magellanic Clouds. 26 refs.

Authors:
 [1]
  1. (Saint Mary's Univ., Halifax (Canada))
Publication Date:
OSTI Identifier:
7058814
Resource Type:
Journal Article
Resource Relation:
Journal Name: Astronomical Journal; (USA); Journal Volume: 98
Country of Publication:
United States
Language:
English
Subject:
71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSICS; PLANETARY NEBULAE; PHYSICAL PROPERTIES; STAR CLUSTERS; PHOTOMETRY; CHARGE-COUPLED DEVICES; DISTANCE; INTERSTELLAR SPACE; NEBULAE; SEMICONDUCTOR DEVICES; SPACE; 640102* - Astrophysics & Cosmology- Stars & Quasi-Stellar, Radio & X-Ray Sources

Citation Formats

Pedreros, M. The open cluster NGC 2818 and its associated planetary nebula. United States: N. p., 1989. Web. doi:10.1086/115284.
Pedreros, M. The open cluster NGC 2818 and its associated planetary nebula. United States. doi:10.1086/115284.
Pedreros, M. Fri . "The open cluster NGC 2818 and its associated planetary nebula". United States. doi:10.1086/115284.
@article{osti_7058814,
title = {The open cluster NGC 2818 and its associated planetary nebula},
author = {Pedreros, M.},
abstractNote = {New CCD UBV photometry of the open cluster NGC 2818 central region indicates that previously derived values of distance and reddening for the cluster have been considerably overestimated, leading to erroneous values for the physical parameters of its associated planetary nebula (PK 261 + 8.1 deg). The analysis of the new data yields E(B-V) = 0.18 + or - 0.03 and V(0)-M(v) = 11.80 + or - 0.2 (2.3 + or - 0.2 kpc) for the cluster's color excess and distance modulus, respectively. If cluster membership is assumed for the planetary nebula, the above estimates result in physical parameters that compare better with those of a typical planetary nebula in the Galaxy and the Magellanic Clouds. 26 refs.},
doi = {10.1086/115284},
journal = {Astronomical Journal; (USA)},
number = ,
volume = 98,
place = {United States},
year = {Fri Dec 01 00:00:00 EST 1989},
month = {Fri Dec 01 00:00:00 EST 1989}
}
  • The discovery of a ringlike emission feature located along the time of sight toward the young open cluster NGC 3572 is reported. The small feature is prominent in H-alpha but has no central star brighter than magnitude V about 20 and is barely detectable in U, B, and V frames. The appearance of the ring is consistent with it being a PN at an unknown distance.
  • UBVRI photoelectric photometry and MK spectral classifications are presented for a large number of stars in the young cluster NGC 3293 and its surroundings (Car OB1). Over 70 cluster members with spectral types earlier than approx.B9 have been identified, and star counts indicate that the expected number of members brighter than Vapprox. =18 is 297 +- 9. Reddenings range between E/sub B/-V=0.20 and 0.46 for cluster members, but are higher for some outlying association stars. The cluster appears to lie just in front of a dense dust lane, which itself appears to be part of the dust complex emanating frommore » the center of the Carina Nebula. Main-sequence fitting provides a reliable distance estimate for the cluster of 2.5 +- 0.2 kpc; other members of the Carina OB1 complex (Tr 14, Tr 15, Tr 16, Cr 228, NGC 3324, and IC 2581) have similar distances, and result in a mean distance to the complex of 2.7 +- 0.2 kpc. An age of 5 x 10/sup 6/ yr is derived for NGC 3293. An interesting gap in the distribution os cluster stars between (B-V)/sub 0/=-0.16 and -0.18 may be related to the early post-main-sequence evolution of these objects. Most of the cluster and association members appear to obey a normal reddening law characterized by R=3.1. A few objects, notably stars in reflection nebulae and others probably associated with the dust cloud just behind the cluster, seem to suffer from anomalous extinction. The oldest subgroup of the carina OB1 complex (IC 2581/NGC 3293; age 5 x 10/sup 6/ yr) lies at one edge of the complex, and the youngest (Tr 14/16; age approx.10/sup 6/ yr) at the other, separated by a projected distance of approx.130 pc. The number of stars per subgroup, however, is much larger in Carina than in any local association, and the age gradient is not so steep. If star formation is considered as propagating from IC 2581/NGC 3293 to Tr 14/16, its propagation velocity is approx.25 to 35 km s/sup -1/ in the direction of increasing galactic longitude.« less
  • We present a deep and wide field-of-view (4' x 7') image of the planetary nebula (PN) NGC 7293 (the Helix Nebula) in the 2.12 {mu}m H{sub 2} v = 1 {yields} 0 S(1) line. The excellent seeing (0.''4) at the Subaru Telescope, allows the details of cometary knots to be examined. The knots are found at distances of 2.'2-6.'4 from the central star (CS). At the inner edge and in the inner ring (up to 4.'5 from the CS), the knot often show a 'tadpole' shape, an elliptical head with a bright crescent inside and a long tail opposite tomore » the CS. In detail, there are variations in the tadpole shapes, such as narrowing tails, widening tails, meandering tails, or multipeaks within a tail. In the outer ring (4.'5-6.'4 from the CS), the shapes are more fractured, and the tails do not collimate into a single direction. The transition in knot morphology from the inner edge to the outer ring is clearly seen. The number density of knots governs the H{sub 2} surface brightness in the inner ring: H{sub 2} exists only within the knots. Possible mechanisms which contribute to the shaping of the knots are discussed, including photoionization and streaming motions. A plausible interpretation of our images is that inner knots are being overrun by a faster wind, but that this has not (yet) reached the outer knots. Based on H{sub 2} formation and destruction rates, H{sub 2} gas can survive in knots from formation during the late asymptotic giant branch phase throughout the PN phase. These observations provide new constraints on the formation and evolution of knots, and on the physics of molecular gas embedded within ionized gas.« less