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Herschel imaging of the dust in the Helix Nebula (NGC 7293) | | G.C. Van de Steene
; P. A. M. van Hoof
; K. M. Exter
; M. J. Barlow
; J. Cernicharo
; M. Etxaluze
; W. K. Gear
; J. R. Goicoechea
; H. L. Gomez
; M. A. T. Groenewegen
; P. C. Hargrave
; R. J. Ivison
; S. J. Leeks
; T. L. Lim
; M. Matsuura
; G. Olofsson
; E. T. Polehampton
; B. M. Swinyard
; T. Ueta
; H. Van Winckel
; C. Waelkens
; R. Wesson
; | | Date: |
17 Nov 2014 | | Abstract: | In our series of papers presenting the Herschel imaging of evolved planetary
nebulae, we present images of the dust distribution in the Helix nebula (NGC
7293). Images at 70, 160, 250, 350, and 500 micron were obtained with the PACS
and SPIRE instruments on board the Herschel satellite. The broadband maps show
the dust distribution over the main Helix nebula to be clumpy and predominantly
present in the barrel wall. We determined the spectral energy distribution of
the main nebula in a consistent way using Herschel, IRAS, and Planck flux
values. The emissivity index of 0.99 +/- 0.09, in combination with the carbon
rich molecular chemistry of the nebula, indicates that the dust consists mainly
of amorphous carbon. The dust excess emission from the central star disk is
detected at 70 micron and the flux measurement agree with previous measurement.
We present the temperature and dust column density maps. The total dust mass
across the Helix nebula (without its halo) is determined to be 0.0035 solar
mass at a distance of 216 pc. The temperature map shows dust temperatures
between 22 and 42 K, which is similar to the kinetic temperature of the
molecular gas, strengthening the fact that the dust and gas co-exist in high
density clumps. Archived images are used to compare the location of the dust
emission in the far infrared (Herschel) with the ionized (GALEX, Hbeta) and
molecular hydrogen component. The different emission components are consistent
with the Helix consisting of a thick walled barrel-like structure inclined to
the line of sight. The radiation field decreases rapidly through the barrel
wall. | | Source: | arXiv, 1411.4429 | | Services: | Forum | Review | PDF | Favorites | |
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