The Gum Catalog

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Gum 1

Coordinates: (223.7°, -1.89°)
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The head of the Seagull nebula is both an HII region and reflection nebula (VDB 93). It is part of the CMa OB1 association and is ionised by the B0IV:e subgiant HD 53367, a young 20 solar mass star with a 5 solar mass companion in a highly elliptical orbit.

Avedisova places this nebula in star formation region SFR 224.20-1.60 with other parts of the Seagull nebula.

You can find good images of both the head and the wings of the Seagull nebula here and here and read a detailed commentary on the Seagull (230° - 220°) sector, which is part of the Commentary on the Galactic Plane

Gum 2

Coordinates: (224.53°, -1.96°)
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This large nebula forms the wings of the Seagull Nebula and in hydrogen-alpha can be seen to be an ionised shell surrounding the CMa OB1 star association (also sometimes identified as the CMa R1 association).

Avedisova lists 4 ionising stars for Sh 2-296, including 3 B-class stars and the O6.5V star HD 54662. (SIMBAD gives an O7III class for this star.) She places it in star formation region SFR 224.20-1.60 with other parts of the Seagull nebula.

You can find good images of both the head and the wings of the Seagull nebula here and here and read a detailed commentary on the Seagull (230° - 220°) sector, which is part of the Commentary on the Galactic Plane.

Gum 3

Coordinates: (225.47°, -2.58°)
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This HII region and reflection nebula is located at the tip of the right wing of the Seagull nebula. It is also known as the reflection nebula VDB 94. It is located next to the cold dark nebula LDN 1657A.

Avedisova lists 5 possible ionising stars, including the O7.5 V star HD 53975, the O9.5 V star HD 54879 and the B1 II/III star HD 53623. (SIMBAD gives the class of HD 53975 as B7, too cool to be an ionising star. SIMBAD may be incorrect, however.) She places Sh 2-297 in star formation region SFR 224.20-1.60 with other parts of the Seagull nebula.

You can find good images of both the head and the wings of the Seagull nebula here and here and read a detailed commentary on the Seagull (230° - 220°) sector, which is part of the Commentary on the Galactic Plane.

You can see more of the surrounding nebulosity in this image by Dean Salman and more detail in the nebula itself in this image by Adam Block.

Gum 4

Coordinates: (227.75°, -0.15°)
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Nicknamed Thor's Helmet, this nebula (also called NGC 2359) is a wind blown bubble ionised by the Wolf-Rayet star WR 7 (HD 56925).

You can view much better images of Thor's Helmet here and here.

Gum 5

Coordinates: (231.44°, -4.41°)
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According to Avedisova, Sh 2-301 is ionised by the O6 V star LSS 207 and the B1 V star LSS 212 and places it in star formation region SFR 231.44-4.41 along with several reflection nebulae including Bran 6 and Bran 7 A-D.

This HII region may be associated with the GS234-02 supershell.

You can see another image of this region here.

Gum 6

Coordinates: (232.56°, 0.89°)
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This HII region lies within the molecular cloud [JKK96] A and is located well in front of the GS234-02 supershell. It contains the infrared star cluster [DBS2003] 4. Avedisova concludes that it is ionised by stars associated with the Bochum 5 cluster, including the O9.5 V star HD 59986, and places it in star formation region SFR 232.56+0.89, along with several other HII regions and reflection nebulae including VDB 97.

The class for HD 59986 is supported by a 1995 paper by Russeil, the Georgelins and colleagues. SIMBAD, however, gives the class for HD 59986 as B5, which would make it too cool to be an ionising star.

Here's another image of this object from an astrophotographer who imaginatively calls it the Snowman nebula.

Gum 7

Coordinates: (234.56°, 0.83°)
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Avedisova lists the ionising stars as the O9 V BD -18 1920 and the B3 III giant LSS 566. Other sources also include the B0V star MFJ Sh 2-307 3. The nebula contains the infrared cluster candidate [DBS2003] 8.

A 1995 paper places Sh 2-299, Sh 2-300, Sh 2-305, Sh 2-306, Sh 2-307 and Sh 2-309 into the same giant molecular cloud complex. A 1996 paper places Sh 2-305 to Sh 2-309 into molecular cloud [JKK96] D within the enormous infrared ring called the GS234-02 supershell, in the Perseus arm.

You can view the enormous dust ring around the supershell in this WISE infrared image. Sh 2-299 and Sh 2-300 also appear in this direction.

Both Avedisova and a 2007 paper, however, give much closer distance estimates and thus appear to exclude this nebula from the supershell.

You can view a good Dean Salman image of this nebula here.

Gum 8

Coordinates: (237.25°, -6.5°)
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This vast nebula, one of the largest single HII regions known in the Milky Way, is ionised by two multiple star systems (Tau Canis Majoris and UW Canis Majoris) each made up of several O-class stars. This image shows only the brightest part of the enormous Sh 2-310 complex.

The intense radiation from the Tau Canis Majoris and UW Canis Majoris star systems has created a cavity in the molecular clouds at the centre of Sh 2-310, which is located beyond the upper right of the image.

Avedisova places Sh 2-310 in the star formation region SFR 237.25-6.50 with 62 components, including 4 masers, 14 infrared sources and the dark nebulae LDN 1660 and LDN 1664.

At least one scientific paper notes the "arrow-shaped bright rim" shown in this image. Perhaps Sh 2-310 should be known as the Arrowhead nebula?

Gum 9

Coordinates: (243.2°, 0.4°)
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NGC 2467, sometimes called the Mandrill nebula, is ionised by the ultrahot O3 V star HD 64568, the O6 IV subgiant HD 64315, and the B0 V star LSS 830, according to Avedisova. Besides the NGC 2467 star cluster itself, it includes the star clusters Haffner 18 and Haffner 19. The bright foreground star on the far left of the image is the B8 IV subgiant HD 64455.

It lies in the direction of the Pup OB1 and Pup OB2 associations (which overlap in the sky).

A good image of NGC 2467 is available in several resolutions from the European Southern Observatory. (Note: the ESO image is rotated 90 degrees, with north to the right.)

Gum 10

Coordinates: (253.8°, -0.5°)
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RCW 19 is part of a 200 thousand solar mass giant molecular cloud related to the Pup OB3 association and the O7f III giant star HD 69464. This image shows only the bright rim of the larger RCW 19 complex.

Avedisova adds the O9.5 III giant CD -35 4412 as a second ionising star. She places RCW 19 in the star formation region SFR 253.75-0.50 with the molecular cloud [MAB97] 253.63+0.00 (this may be the cloud mentioned above) and the reflection nebulae Bran 124b, Bran 125b and VdBH 9.

You can see RCW 19 and RCW 20 together in this SuperCOSMOS hydrogen-alpha image, which also shows the boundaries of Pup OB3 and the newly discovered Kharchenko cluster [KPR2005] 45 (labelled ASCC 1045).

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Colin Gum, working at Australia's Mount Stromlo observatory in 1951, completed the first major survey of HII regions visible in the southern hemisphere. He published his nebula catalog in 1955. Although Gum's catalog was largely superceded by the RCW catalog published in 1960, many HII regions are still referenced by their Gum numbers even today, so these pages provide an easy reference with cross references to the RCW and Sharpless catalogs.

Most of the images used to illustrate the Gum catalog were created using the SuperCOSMOS Sky Survey, with red = hydrogen-alpha, blue = UKST Blue and green = UKST Infrared. Because green represents infrared, the images are not quite the same as would be seen at purely visual frequencies. Green in these images usually reveals warm dust or red giant stars.

These images were created using the POSS-II/UKSTU data of the Digitized Sky Survey and SuperCOSMOS using the process described here.

According to my correspondence with the Royal Observatory Edinburgh and the Space Telescope Science Institute, I am allowed to use the POSS-II/UKSTU data to create and display images for non-commercial purposes so long as I include this fine print for the SuperCOSMOS data:

Use of these images is courtesy of the UK Schmidt Telescope (copyright in which is owned by the Particle Physics and Astronomy Research Council of the UK and the Anglo-Australian Telescope Board) and the Southern Sky Survey as created by the SuperCOSMOS measuring machine and are reproduced here with permission from the Royal Observatory Edinburgh.

and this acknowledgement taken from the DSS site:

The Digitized Sky Surveys were produced at the Space Telescope Science Institute under U.S. Government grant NAG W-2166. The images of these surveys are based on photographic data obtained using the Oschin Schmidt Telescope on Palomar Mountain and the UK Schmidt Telescope. The plates were processed into the present compressed digital form with the permission of these institutions.

The Second Palomar Observatory Sky Survey (POSS-II) was made by the California Institute of Technology with funds from the National Science Foundation, the National Geographic Society, the Sloan Foundation, the Samuel Oschin Foundation, and the Eastman Kodak Corporation.

The UK Schmidt Telescope was operated by the Royal Observatory Edinburgh, with funding from the UK Science and Engineering Research Council (later the UK Particle Physics and Astronomy Research Council), until 1988 June, and thereafter by the Anglo-Australian Observatory. The blue plates of the southern Sky Atlas and its Equatorial Extension (together known as the SERC-J), as well as the Equatorial Red (ER), and the Second Epoch [red] Survey (SES) were all taken with the UK Schmidt.

The "Second Epoch Survey" of the southern sky was made by the Anglo-Australian Observatory (AAO) with the UK Schmidt Telescope. Plates from this survey have been digitized and compressed by the ST ScI. The digitized images are copyright © 1993-5 by the Anglo-Australian Observatory Board, and are distributed herein by agreement.

The "Equatorial Red Atlas" of the southern sky was made with the UK Schmidt Telescope. Plates from this survey have been digitized and compressed by the ST ScI. The digitized images are copyright © 1992-5, jointly by the UK SERC/PPARC (Particle Physics and Astronomy Research Council, formerly Science and Engineering Research Council) and the Anglo-Australian Telescope Board, and are distributed herein by agreement.

The compressed files of the "Palomar Observatory - Space Telescope Science Institute Digital Sky Survey" of the northern sky, based on scans of the Second Palomar Sky Survey are copyright © 1993-1995 by the California Institute of Technology and are distributed herein by agreement. The compressed files of the "Palomar Observatory - Space Telescope Science Institute Digital Sky Survey" of the northern sky, based on scans of the Second Palomar Sky Survey are copyright © 1993-1995 by the California Institute of Technology and are distributed herein by agreement.