OBSERVATIONAL STUDY OF THE MULTISTRUCTURED PLANETARY NEBULA NGC 7354
- Instituto de Astronomia, Universidad Nacional Autonoma de Mexico, Apdo. Postal 877, 22800 Ensenada, B. C. (Mexico)
- Instituto de Astrofisica de Andalucia, CSIC, C/Camino Bajo de Huetor 50, E-18008 Granada (Spain)
- Depto. de Investigacion en Fisica, Universidad de Sonora, Blvd. Rosales Esq. L. D. Colosio, Edif. 3H, 83190 Hermosillo, Son. (Mexico)
- Instituto Tecnologico de Ensenada, Av. Transpeninsular 1675, 22835 Ensenada, B.C. (Mexico)
We present an observational study of the planetary nebula (PN) NGC 7354 consisting of narrowband H{alpha} and [N II]{lambda}6584 imaging as well as low- and high-dispersion long-slit spectroscopy, and VLA-D radio continuum. According to our imaging and spectroscopic data, NGC 7354 has four main structures: a quite round outer shell and an elliptical inner shell, a collection of low-excitation bright knots roughly concentrated on the equatorial region of the nebula, and two asymmetrical jet-like features, not aligned either with the shells' axes, or with each other. We have obtained physical parameters like electron temperature and electron density as well as ionic and elemental abundances for these different structures. Electron temperature and electron density slightly vary throughout the nebula going from {approx_equal}11, 000 to {approx_equal}14, 000 K, and from {approx_equal}1000 to {approx_equal} 3000 cm{sup -3}, respectively. The local extinction coefficient c {sub H{beta}} shows an increasing gradient from south to north and a decreasing gradient from east to west consistent with the number of equatorial bright knots present in each direction. Abundance values show slight internal variations but most of them are within the estimated uncertainties. In general, abundance values are in good agreement with the ones expected for PNe. Radio continuum data are consistent with optically thin thermal emission. Mean physical parameters derived from the radio emission are electron density n{sub e} = 710 cm{sup -3} and M(H II) = 0.22 M {sub sun}. We have used the interactive three-dimensional modeling tool SHAPE to reproduce the observed morphokinematic structures in NGC 7354 with different geometrical components. Our observations and model show evidence that the outer shell is moving faster ({approx_equal}35 km s{sup -1}) than the inner one ({approx_equal} 30 km s{sup -1}). Our SHAPE model includes several small spheres placed on the outer shell wall to reproduce equatorial bright knots. Observed and modeled velocity for these spheres lies between the inner and outer shells velocity values. The two jet-like features were modeled as two thin cylinders moving at a radial velocity of {approx_equal}60 km s{sup -1}. In general, our SHAPE model is in very good agreement with our imaging and spectroscopic observations. Finally, after modeling NGC 7354 with SHAPE, we suggest a possible scenario for the formation of the nebula.
- OSTI ID:
- 21301210
- Journal Information:
- Astronomical Journal (New York, N.Y. Online), Vol. 139, Issue 4; Other Information: DOI: 10.1088/0004-6256/139/4/1426; Country of input: International Atomic Energy Agency (IAEA); ISSN 1538-3881
- Country of Publication:
- United States
- Language:
- English
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