Bibcode
Phillips, J. P.; Mampaso, A.; Vilchez, J. M.; Gomez, P.
Bibliographical reference
Astrophysics and Space Science (ISSN 0004-640X), vol. 122, no. 1, May 1986, p. 81-96.
Advertised on:
5
1986
Citations
16
Refereed citations
16
Description
Near infrared maps of the planetary nebula IC 418 taken at 5 arc sec
spatial resolution are presented. These show an extremely compact source
structure at 1.65 microns, and very much broader and more elliptical
emission distributions at 2.2 and 3.6 microns. The possibility that the
near infrared continuum derives from small grains with low thermal
capacity is discussed, and synthetic spectra are derived. These indicate
a very much slower variation of flux with wavelength than would be
deduced for grains at unitary temperature, and imply a near infrared
continuum which is significantly cooler than maximum grain temperatures.
Fits to the spectrum of IC 418 suggest that peak grain temperatures may
approach 1000 K; for instance, compared to the observed color
temperature of about 650 K. Finally, the relevant grains are required to
be refractory and, given the large C/O ratio in this nebula, probably
consist of graphite. Their mass is also required to be small, and is
probably of order 2 x 10 to the -7th solar masses. This compares with
the probable total mass for large dust grains of about 0.0001 solar
masses. Although they are both small and warm, such grains would be
expected to persist over the lifetime of the nebula, and may also be
responsible for various NIR band emission features.