Beauty and Astrophysics

Michael S. Bessell, PASA, 17 (2), 179.

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Atlas of Images


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 $H\alpha$ survey.

Filters Used

Many of the images combine two narrow band filters, $H\alpha$ (red) and [OIII] (green) with a short exposure B (blue). These bands are actually red (6563Å), green (5007Å) and blue ($\approx $4300Å). 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], $H\alpha$, 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$\sim$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 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.

Table 2.  List of Images
No. Name Filters Camera Obs. Notes
1a Antenna galaxies BV$H\alpha$ 40 inch msb Pair of colliding galaxies. Note knots of star forming regions
1b Centaurus A BO3$H\alpha$ 40 inch b.w Radio galaxy. Note green [OIII] jet top left
1c M 95 BV$H\alpha$ 40 inch msb Theta galaxy. Note the low surface brightness outer arms
2a NGC 1365 BV$H\alpha$ 40 inch msb Famous barred spiral. Note the dust lane leading into the core
2b NGC 2997 BV$H\alpha$ 40 inch msb Grand Spiral. Note the HII regions in the spiral arms
2c NGC 6744 BV$H\alpha$ 40 inch msb A different type of barred spiral
3a M 31 BV$H\alpha$ Nikon msb Andromeda galaxy. Note the dust lanes and HII regions
3b Magellanic Clouds BV$H\alpha$ Hasselb msb The closest galaxies to the Milky Way
3c SMC BV$H\alpha$ Nikon msb The SMC and wing + globular clusters 47 Tuc and NGC 362
4a SMC zoom BO3$H\alpha$ Nikon msb The gas-rich SMC. The HII regions dominate in this image
4b LMC BO3$H\alpha$ Nikon msb HII regions and the old stellar population in the bar
4c LMC zoom BO3$H\alpha$ Nikon msb 30 Doradus and shells of HII regions dominate this image.
5a 30 Doradus BVR 40 inch sung Three beautiful views of 30 Doradus. Stars dominate here
5b 30 Doradus BV$H\alpha$ 40 inch sung In this image stars and the gas share the stage
5c 30 Doradus BO3$H\alpha$ 40 inch sung Here the gas dominates. It appears 3 dimensional
6a Crux and pointers BV$H\alpha$ Hasselb msb The archetypal view of the southern skies
6b Scorpio BV$H\alpha$ Hasselb msb The huge constellation of Scorpio extends from the plane
6c Sag-Oph BV$H\alpha$ Hasselb msb View looking toward the centre of the Milky Way
7a Jewel Box BV$H\alpha$ 40 inch b.w A young cluster of massive stars near the Southern Cross
7b NGC 2004 164V$H\alpha$ HST b.dc.k A similar cluster in the LMC with many times more stars
7c NGC 2004 zoom 164V$H\alpha$ HST b.dc.k These are HST images. Note the blue main sequence stars
8a NGC 2100 zoom 164V$H\alpha$ HST b.dc.k Be stars (pink), red supergiants (orange);
8b NGC 330 zoom 164V$H\alpha$ HST b.dc.k A supergiants (white)
8c NGC 346 BO3$H\alpha$ 40 inch msb The largest cluster of young massive stars in the SMC
9a Eta Carina BO3$H\alpha$ Nikon msb The beautiful $\eta$ Car nebula. Note the lace work
9b Eta Carina BO3$H\alpha$ 40 inch msb A closer view of the nebula and young clusters
9c Eta Carina BV$H\alpha$ 40 inch sung Note the strange variable $\eta$ Car
10a Trumpler 24 BV$H\alpha$ 40 inch sung A young cluster and HII region
10b Bochum 14 BV$H\alpha$ 40 inch sung An HII region surrounding a Wolf Rayet star
10c Bochum 10 BV$H\alpha$ 40 inch sung Another young cluster and HII region
11a Lagoon & Trifid BO3$H\alpha$ Nikon msb The well known Lagoon and Trifid nebula
11b Trifid BO3$H\alpha$ 40 inch msb A blue reflection nebula, HII region and dust lanes
11c Lagoon zoom BO3$H\alpha$ Nikon msb Color change shows the ionization gradient.
12a Lagoon inner BO3$H\alpha$ 40 inch msb Yellow near the hottest stars. Red shows lower ionization
12b Lagoon inner BV$H\alpha$ 40 inch sung Beautiful dust lanes and starkly etched globules
12a Lagoon inner zoom BO3$H\alpha$ 40 inch msb Colours rotated to produce moody image `a Turner'
13a Eagle Nebula BO3$H\alpha$ 40 inch b.w Star forming region. HST image available.
13b Eagle Nebula zoom BO3$H\alpha$ 40 inch b.w Rotated field
13c CG4 Nebula BVR 40 inch msb Interesting reflection nebula with dust clouds
14a NGC 3603 BV$H\alpha$ 40 inch sung Young cluster
14b NGC 6188 BO3$H\alpha$ Nikon b.w Another interesting obscured nebulosity
14c Pismis 24 BV$H\alpha$ 40 inch sung Young cluster
15a IRAS 10.60.100$\mu$ IRAS IRAS From Sutherland & Bally
15b Orion-Eridanus BO3$H\alpha$ Hasselb suth Wide field view mosaic
15c Orion BO3$H\alpha$ Hasselb msb Showing Barnard's Loop around the Orion constellation
16a $\lambda$ Orionis BO3$H\alpha$ Nikon msb The 'bubble' surrounding the O star $\lambda$ Orionis
16b Orion BO3$H\alpha$ Nikon msb The region between the Belt and Sword of Orion.
16c Horsehead Nebula BO3$H\alpha$ 40 inch sung The famous dark cloud in Orion
17a The Orion Nebula BO3$H\alpha$ 40 inch msb Different views of the great nebula of Orion
17b The Orion Nebula BV$H\alpha$ 40 inch msb Different filters highlight small ionization differences
18a The Orion Nebula S2$H\alpha$N2 KPNO 1m b.s The seeing is much better in these next images
18b The Orion Nebula S2$H\alpha$N2 NTT 3.5m b.s Note the detail in this excellent ground based image
18c The Orion Nebula S2$H\alpha$N2 HST b.s Note the stellar tails all pointing away from the trapezium
19a NGC 2264 N BV$H\alpha$ 40 inch sung Part of young cluster in Monocerotis
19b NGC 2264 W BV$H\alpha$ 40 inch sung Note the beautiful reflection nebula and dust clouds
19c Rosette Nebula BO3$H\alpha$ Nikon murph Strong ionization produces these unusual colouring
20a Vela-Puppis BO3$H\alpha$ Hasselb msb This wide field view shows the comet Hale-Bopp lower right
20b Vela BO3$H\alpha$ Nikon msb Note the [OIII] and $H\alpha$ filaments of the SN remnant
20c Vela zoom BO3$H\alpha$ Nikon msb Note the details of the twisted [OIII] filaments
21a Crab Nebula BO3$H\alpha$ 40 inch b.w Note the green [OIII], red $H\alpha$ and blue synchrotron light
21b Helix Nebula BO3$H\alpha$ 40 inch b.w Planetary nebula. The blue and green colours have been reversed
21c Comet Hale-Bopp V Nikon msb Note the two globular clusters. The colors represent intensities

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

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