The RCW Catalog

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RCW 1

Coordinates: (224.53°, -1.96°)
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RCW 1
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.

RCW 1a

Coordinates: (225.47°, -2.58°)
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RCW 1a
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.

RCW 1b

Coordinates: (223.61°, -0.20°)
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RCW 1b
RCW 1b does not appear to designate any specific object but rather is a region of stars and nebulosity towards the left wing of the Seagull nebula within the CMa OB1 association. The boundary box includes the star cluster NGC 2353.

RCW 2

Coordinates: (223.7°, -1.89°)
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RCW 2
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

RCW 3

Coordinates: (224.19°, 1.22°)
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RCW 3
According to Avedisova this HII region is ionised by an uncatalogued B0.5 V star (MFJ Sh 2-294 4). It contains the loose infrared star cluster [BDS2003] 95 which is divided into two sub-clusters, the denser one surrounding the ionising star.

Its odd shape looks like an upside down octopus - should it perhaps be called the Octopus nebula?

RCW 4

Coordinates: (224.4°, 3.2°)
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RCW 4
This large faint nebula appears to be part of the Seagull nebula emission associated with RCW 1 = Sh 2-296 surrounding the CMa OB1 association.

According to SIMBAD, there have been no references in the scientific literature to this nebula beyond the RCW catalog itself.

RCW 5

Coordinates: (227.75°, -0.15°)
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RCW 5
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.

RCW 6

Coordinates: (231.44°, -4.41°)
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RCW 6
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.

RCW 7

Coordinates: (232.56°, 0.89°)
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RCW 7
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.

RCW 8

Coordinates: (233.8°, -0.2°)
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RCW 8
Sh 2-305 is ionised by at least two O-class stars ([VM75] Sh 2-305 4 (O8.5 V) and [VM75] Sh 2-305 2 (O9.5 V)), and possibly two B0 class stars as well. It contains the loose infrared cluster [DBS2003] 5.

Avedisova places this nebula in star formation region SFR 233.75-0.18 along with 5 infrared sources, a water maser and the star cluster Mayer 3.

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.

RCW 9

Coordinates: (233.88°, -12.39°)
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RCW 9
According to a 1982 study, this nebula is ionised by the Wolf-Rayet star WR 6 (EZ CMa) along with Sh 2-304 and Sh 2-308. However, a look at this region in hydrogen-alpha suggests that Sh 2-304 lies at some distance from WR 6 and forms the brightest portion of a long ridge that lies below the large Gum 8 / Sh 2-310 HII region. The ridge may be ionised by the combined radiation from the many hot stars in this region.

RCW 10

Coordinates: (234.31°, -0.36°)
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RCW 10
Avedisova lists three ionising O-stars for this nebula, including the hot O5 V star LSS 458. The others are the O9 III giant LSS 499 and the O9.5 III giant LSS 467.

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.

A part of the much brighter Sh 2-309 (RCW 13) is visible in the bottom left of this image.

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Alex Rodgers, Colin Campbell, and John Whiteoak, working at Australia's Mount Stromlo observatory under the direction of Dutch-American astronomer Bart Bok, published their nebula catalog in 1960. The RCW catalog is largely an expansion of Colin Gum's 1955 catalog. Although astronomers publish articles referring to the RCW nebulae almost every month, there seems to be few places on the Internet that bring together information on these nebulae as a whole - unlike, for example, the Messier catalog. This is most likely because the Messier objects are visible to anyone with a pair of binoculars or a small telescope. Most of the RCW objects are clearly visible only in long exposure CCD images or photographic plates taken by large telescopes. Fortunately some of these plates have now been digitally scanned and made publicly available.

Many of the brightest and most beautiful Milky Way star formation regions visible from the southern hemisphere are in the RCW catalog so the 182 objects it contains are well worth examining carefully. (In fact there are more than 182 objects as subsequent research has shown that some of the RCW nebulae consist of more than one object.) At least 50 objects in the RCW catalog are also in the Sharpless catalog and I have noted this in the descriptions of these objects.

Most of the images used to illustrate the RCW 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.