Spatially Resolved 3 um Spectroscopy of IRAS 22272+5435: Formation and Evolution of Aliphatic Hydrocarbon Dust in Proto-Planetary Nebula

Astrophysics, abstract
astro-ph/0301311

From: Miwa Goto <mgoto@duke.ifa.hawaii.edu>

Date: Thu, 16 Jan 2003 01:37:28 GMT   (164kb)

Authors:
M. Goto (1,2),
W. Gaessler (3),
Y. Hayano (4),
M. Iye (4),
Y. Kamata (4),
T. Kanzawa (1),
N. Kobayashi (1),
Y. Minowa (5),
D. J. Saint-Jacques (6),
H. Takami (1),
N. Takato (1),
H. Terada (1) ((1) Subaru Telescope, (2) Univ. of Hawaii, (3) MPI, (4) NAOJ, Mitaka, (5) Univ. Tokyo, (6) Univ. of Montreal)

Comments: 14 pages, 7 figures, Accepted for publication in the Astrophyical
Journal

We present medium-resolution 3 um spectroscopy of the carbon-rich
proto-planetary nebula IRAS 22272+5435. Spectroscopy with the Subaru Telescope
adaptive optics system revealed a spatial variation of hydrocarbon molecules
and dust surrounding the star. The ro-vibrational bands of acetylene (C2H2) and
hydrogen cyanide (HCN) at 3.0 um are evident in the central star spectra. The
molecules are concentrated in the compact region near the center. The 3.3 and
3.4 um emission of aromatic and aliphatic hydrocarbons is detected at 600–1300
AU from the central star. The separation of spatial distribution between gas
and dust suggests that the small hydrocarbon molecules are indeed the source of
solid material, and that the gas leftover from the grain formation is being
observed near the central star. The intensity of aliphatic hydrocarbon emission
relative to the aromatic hydrocarbon emission decreases with distance from the
central star. The spectral variation is well matched to that of a laboratory
analog thermally annealed with different temperatures. We suggest that either
the thermal process after the formation of a grain or the variation in the
temperature in the dust-forming region over time determines the chemical
composition of the hydrocarbon dust around the proto-planetary nebula.

References and citations for this submission:

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