Publication: Physical structure of the proto-planetary nebula CRL 618. I. Optical long-slit spectroscopy and imaging
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2002-10-10
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American Astronomical Society
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In this paper we present optical long-slit spectroscopy and imaging of the proto-planetary nebula CRL 618. The optical lobes of CRL 618 consist of shock-excited gas, which emits many recombination and forbidden lines, and dust, which scatters light from the innermost regions. From the analysis of the scattered Hα emission, we derive a nebular inclination of i = 24° ± 6°. The spectrum of the innermost part of the east lobe (visible as a bright, compact nebulosity close to the star in the Hα Hubble Space Telescope image) is remarkably different from that of the shocked lobes but similar to that of the inner H II region, suggesting that this region represents the outermost parts of the latter. We find a nonlinear radial variation of the gas velocity along the lobes. The largest projected LSR velocities (with respect to the systemic velocity), ~80 km s^-1, are measured at the tips of the lobes, where the direct images show the presence of compact bow-shaped structures. The velocity of the shocks in CRL 618 is in the range ~75-200 km s^-1, as derived from diagnostic line ratios and line profiles. We report a brightening (weakening) of [O III] λ5007 ([O I] λ6300) over the last ~10 years that may indicate a recent increase in the speed of the exciting shocks. From the analysis of the spatial variation of the nebular extinction, we find a large density contrast between the material inside the lobes and beyond them: the optical lobes seem to be "cavities" excavated in the asymptotic giant branch (AGB) envelope by interaction with a more tenuous post-AGB wind. The electron density, with a mean value n_e ~ 5 × 10^3-10^4 cm^-3, shows significant fluctuations but no systematic decrease along the lobes, in agreement with most line emission arising in a thin shell of shocked material (the lobe walls) rather than in the post-AGB wind filling the interior of the lobes. The masses of atomic and ionized gas, respectively, in the east (west) lobe are >1.3 × 10^-4 (>7 × 10^-5) and ~6 × 10^-5 (~4 × 10^-5) M_☉. The shocks in CRL 618 are in a radiative regime and may lead in the future to the evolution of the optically emitting lobes into a fast, bipolar molecular outflow. The time required by the dense, shocked gas to cool down significantly is ≲2 yr, which is substantially lower than the kinematical age of the lobes (≲180 yr). This result suggests that a fast wind is currently active in CRL 618 and keeps shocking the circumstellar material.
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© 2002. The American Astronomical Society. All rights reserved. The authors are grateful to Noam Soker for reading and commenting on this paper, to A. Castro Carrizo for helping during the long-slit observations, and to C.-F. Lee for fruitful conversations during the writing of this paper. This work was performed at the Jet Propulsion Laboratory, California Institute of Technology, under a contract with the National Aeronautics and Space Administration, and has been partially supported by a NASA Long Term Space Astrophysics grant to R. S. This research has made use of the USNOFS Image and Catalog Archive operated by the United States Naval Observatory, Flagstaff Station (http://www.nofs. navy.mil/data/fchpix). The authors also acknowledge the use of NASA’s Astrophysical Data System Abstract Service (ADS).
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Alcolea, J., Bujarrabal, V., Sánchez Contreras, C., Neri, R., & Zweigle, J. 2001, A&A, 373, 932
Aller, L. H., & Keyes, C. D. 1987, ApJS, 65, 405
Bachiller, R., Gómez González, J., Bujarrabal, V., & Martín Pintado, J. 1988, A&A, 196, L5
Baessgen, M., Hopfensitz, W., & Zweigle, J. 1997, A&A, 325, 277
Blondin, J. M., Fryxell, B. A., & Konigl, A. 1990, ApJ, 360, 370
Bujarrabal, V., Alcolea, J., Sánchez Contreras, C., & Sahai, R. 2002, A&A, 389, 271
Bujarrabal, V., Castro Carrizo, A., Alcolea, J., & Sánchez Contreras, C. 2001, A&A, 377, 868
Bujarrabal, V., Gómez González, J., Bachiller, R., & Martín Pintado, J. 1988, A&A, 204, 242
Cantó, J., Meaburn, J., Theokas, A. C., & Elliott, K. H. 1980, MNRAS, 193, 911
Cardelli, J. A., Clayton, G. C., & Mathis, J. S. 1989, ApJ, 345, 245
Carsenty, U., & Solf, J. 1982, A&A, 106, 307 (CS82)
Cernicharo, J., Guélin, M., Martín Pintado, J., Peñalver, J., & Mauersberger, R. 1989, A&A, 222, L1
Dalgarno, A., & McCray, R. A. 1972, ARA&A, 10, 375
Frank, A. 1999, NewA Rev., 43, 31
Gammie, C. F., Knapp, G. R., Young, K., Phillips, T. G., & Falgarone, E. 1989, ApJ, 345, L87
Goodrich, R. W. 1991, ApJ, 376, 654
Gottlieb, E. W., & Liller, W. 1976, ApJ, 207, L135
Gurzadyan, G. A. 1997, The Physics and Dynamics of Planetary Nebulae (Berlin: Springer)
Hajian, A. R., Phillips, J. A., & Terzian, Y. 1996, ApJ, 467, 341
Hartigan, P., Morse, J. A., & Raymond, J. 1994, ApJ, 436, 125
Hartigan, P., Raymond, J., & Hartmann, L. 1987, ApJ, 316, 323 (HRH87)
Hollenbach, D., & McKee, C. F. 1989, ApJ, 342, 306
Howarth, J. D. 1983, MNRAS, 203, 301
Kaler, J. B. 1978, ApJ, 220, 887
Kastner, J., Soker, N., & Rappaport, S. A., eds. 2000, ASP Conf. Ser. 199, Asymmetrical Planetary Nebulae II: From Origins to Microstructures (San Francisco: ASP)
Kelly, D. M., Latter, W. B., & Rieke, G. H. 1992, ApJ, 395, 174
Knapp, G. R., & Morris, M. 1985, ApJ, 292, 640
Knapp, G. R., Sandell, G., & Robson, E. I. 1993, ApJS, 88, 173
Kwok, S. 2000, The Origin and Evolution of Planetary Nebulae (Cambridge: Cambridge Univ. Press)
Kwok, S., & Bignell, R. C. 1984, ApJ, 276, 544
Kwok, S., & Feldman, P. A. 1981, ApJ, 247, L67
Lambert, D. L., Gustafsson, B., Eriksson, K., & Hinkle, K. H. 1986, ApJS, 62, 373
Leuenhagen, U., Hamann, W.-R., & Jeffery, C. S. 1996, A&A, 312, 167
Martín Pintado, J., Bujarrabal, V., Bachiller, R., Gómez González, J., & Planesas, P. 1988, A&A, 197, L15
Martín Pintado, J., Gaume, R., Bachiller, R., & Johnson, K. 1993, ApJ, 419, 725
Meixner, M., Campbell, M. T., Welch, W. J., & Likkel, L. 1998, ApJ, 509, 392
Mendoza, C. 1983, in IAU Symp. 103, Planetary Nebulae, ed. D. R. Flower (San Francisco: ASP), 143
Neri, R., García Burillo, S., Guèlin, M., Guilloteau, S., & Lucas, R. 1992, A&A, 262, 544
Osterbrock, D. E. 1989, Astrophysics of Gaseous Nebulae and Active Galactic Nuclei (Mill Valley: University Science Books)
Phillips, J. P., Williams, P. G., Mampaso, A., & Ukita, N. 1992, A&A, 260, 283
Reipurth, B., Yu, K., Heathcote, S., Bally, J., & Rodríguez, L. F. 2000, AJ, 120, 1449
Riera, A., Phillips, J. P., & Mampaso, A. 1990, Ap&SS, 171, 231
Sahai, R., & Trauger, J. T. 1998, AJ, 116, 1357
Sánchez Contreras, C., Bujarrabal, V., Miranda, L. F., & Fernández Figueroa, M. J. 2000, A&A, 355, 1103
Schmidt, G. D., & Cohen, M. 1981, ApJ, 246, 444
Schwarz, H. E., Aspin, C., Corradi, R. L. M., & Reipurth, B. 1997, A&A, 319, 267
Spergel, D. N., Giuliani, J. L., & Knapp, G. R. 1983, ApJ, 275, 330
Trammell, S. R. 2000, in ASP Conf. Ser. 199, Asymmetrical Planetary Nebulae II: From Origins to Microstructures, ed. J. Kastner, N. Soker, & S. A. Rappaport (San Francisco: ASP), 147
Trammell, S. R., Dinerstein, H. L., & Goodrich, R. W. 1993, ApJ, 402, 249
Tylenda, R., Acker, A., & Stenholm, B. 1993, A&AS, 102, 595
Welch, C. A., Frank, A., Pipher, J. L., Forrest, W. J., & Woodward, C. E. 1999, ApJ, 522, L69
Westbrook, W. E., Becklin, E. E., Merrill, K. M., Neugebauer, G., Schmidt, M., Willner, S. P., & Wynn-Williams, C. G. 1975, ApJ, 202, 407