Beauty and Astrophysics
Michael S. Bessell, PASA, 17 (2), 179.

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Subsections

• Preamble
• Filters Used
• List of Images

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Atlas of Images

Preamble

Some examples of images from all these instruments will be shown. The images do not represent limiting observations but rather are illustrative of the information content and the astrophysical problems that they can address. The images are presented in a somewhat arbitrary progression from external galaxies to our galaxy, the Milky Way, then move along the galactic plane from Centaurus to Monocerotis commencing with the widest field views to the narrow views. The aim is to integrate what we see in our galaxy and the Magellanic Clouds with what we see in more distant galaxies.

The images of the external spiral galaxies show clearly the spatial distribution of the star forming regions, the giant HII regions (like red beads in a necklace) and the dust lanes lying along the arms and reaching right into the centre of the galaxies. The central bulges made up of older stars are also very obvious. When we look at the wide field images of the Milky Way we can recognise similar HII regions and dust lanes and we can then zoom in on these to reveal bright blue stars and shimmering curtains of ionised hydrogen. We can see the results of extensive stellar winds and the remnants of exploding stars with their delicate twisted shock fronts. By providing deep images of the interstellar region we can see the complicated interaction between hot stars and gas and marvel at the beauty of these interactions.

The image scale (12 arcsec/pixel) with the Nikon lens is good for most large scale structure but is unable to resolve the fine collimation of the Herbig-Haro jets associated with pre-main sequence stars or the disks of distant planetary nebulae, both of which are a couple of arcsec across. These are seen extremely well on the films of the new AAO Schmidt survey.

Filters Used

Many of the images combine two narrow band filters, (red) and [OIII] (green) with a short exposure B (blue). These bands are actually red (6563ц…), green (5007ц…) and blue (4300ц…). The combination of HII (13.6 eV) and [OIII] (35.1 eV) with their significantly different ionization potentials traces the ionization gradients. It highlights the hottest stars and the most energetic shocks. A few images will be shown that feature more subtle ionization differences using [SII], , and [NII], all 'red' lines but shown as RGB in order of wavelength. Two images will be also be shown with out-of-order colours that result in a more striking images.

List of Images

The images are available for viewing from http://www.mso.anu.edu.au/bessell/images/. Thumbnails of the images are displayed three per line for 21 lines. Table 2 lists the images and identifies them by line and position. It also gives the filters comprising the BGR of the colour image, the camera used (see Table 1), the observers, and a brief comment about the image or series of images. Detailed descriptions of many of the astronomical objects can be found with David Malin's images at http://www.aao.gov.au/images.html. The shorthand O3, S2, N2 are given for [OIII], [NII] and [SII] respectively. The code for the observers is msb: Bessell; b.w: Buxton & Watson; sung: Hwankyung Sung; murph: Murphy; b.dc.k: Bessell, Da Costa & Keller; suth: Sutherland; s.b: Sutherland & Bally.

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Next Section: Discussion
Title/Abstract Page: Beauty and Astrophysics
Previous Section: Introduction
Contents Page: Volume 17, Number 2

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б© Copyright Astronomical Society of Australia 1997