The RCW Catalog

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RCW 141

Coordinates: (0.33°, -0.19°)
[ See details ]

This nebula is part of the Sh 2-15 to Sh 2-20 complex of HII regions located in the Sgr OB5 association in the Sagittarius arm. It contains the infrared star clusters [DB2000] 5 and [DB2000] 6.

RCW 142

Coordinates: (0.59°, -0.86°)
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This HII region is located in the galactic bar below the galactic plane and is associated with the infrared star clusters [DB2000] 7, [DB2000] 10, [DB2000] 11 and [DB2000] 12.

RCW 143

Coordinates: (3.5°, 2.1°)
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The RCW catalog describes this as a medium bright 7x6 arcminute nebula near the star cluster NGC 6432. However, there is no visible nebulosity at this location and NGC 6432 is not currently believed to be a true optical star cluster.

It seems likely that this nebula does not exist.

The infrared cluster candidates [DB2000] 44 and [DB2000] 45 lie in this direction.

RCW 144

Coordinates: (4.28°, 0.55°)
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This is a ring nebula surrounding the O8 III giant 63 Ophiuchi (HD 162978), which lies at the edge of the Sgr OB1 association in the Sagittarius arm.

You can see the full extent of this huge object in this SuperCOSMOS image.

RCW 145

Coordinates: (6.6°, 0.1°)
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This large faint HII region next to the Trifid nebula is ionised by the O9Ib supergiant LS 4551 and the O-class LS 4538, It lies in the direction of the supernova remnant SNR G006.4-00.1 (W 28).

You can view a SuperCOSMOS hydrogen-alpha image.

RCW 146

Coordinates: (6.6°, -1.5°)
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A large area of nebulosity in the direction of the Lagoon nebula. The RCW catalog breaks this up into the Lagoon nebula proper (RCW 146a), the much fainter Gum 74b nebula next to it (RCW 146b) and the three smaller Sharpless nebulae Sh 2-29, Sh 2-31 and Sh 2-32 further below the galactic plane (RCW 146c).

RCW 146a

Coordinates: (6.09°, -1.29°)
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The Lagoon nebula (M8 = NGC 6523-NGC 6530) is
a large HII region mainly ionized by two O-class stars, the ultrahot O4V class 9 Sagittarii and the binary HD 165052 (O6.5V + O7.5V). Sharpless also lists 12 B-stars that may also ionise the nebula. It also includes the radio source W 29.

The Lagoon nebula is a major feature of the Sgr OB1 association in the Sagittarius arm. It is embedded within a molecular cloud which extends to the star cluster NGC 6530. The Hourglass nebula lies within M8’s core. This is a blister-type HII region which has been produced by the O7.5V star Herschel 36.

There is a good image of the the Lagoon nebula here and an amazing wide angle image of the whole region that includes the entire RCW 146 complex and the Trifid nebula.

RCW 146b

Coordinates: (6.89°, -0.93°)
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This is a large area of faint nebulosity lying between the Trifid and Lagoon nebulae. It is ionised by the O9.5/B0 III giant HD 164971 as well as HD 165132 according to Vogt and Moffat. (SIMBAD gives a B5/B6Ib class for HD 165132, too cool to ionise the nebula.)

RCW 146c

Coordinates: (7.11°, -2.10°)
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Sh 2-29, Sh 2-31, and Sh 2-32 are a group of three nebulae next to the much larger Lagoon nebula. This group is combined together in the RCW (RCW 146c) and Gum (Gum 75) catalogs.

RCW 147

Coordinates: (7.0°, -0.2°)
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The Trifid nebula, M 20, is an HII region ionised by the O7.5 class multiple star HD 164492 (with seven known components), which is a member of the star cluster NGC 6514. It is divided into three parts by dust lanes. A blue reflection nebula surrounds the HII region.

The Trifid nebula is usually assumed to be part of the Sgr OB1 association in the Sagittarius arm, along with the Lagoon nebula. However, the surprisingly large range of distance estimates for the nebula leaves open the possibility that it lies much further away in the Centaurus arm.

RCW 148

Coordinates: (8.2°, 0.6°)
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The RCW catalog describes this as a 2x2 arcminute bright nebula, however, there is no visible nebulosity at this location in SuperCOSMOS and no significant references in the scientific literature beyond the catalog itself.

It seems likely that this nebula does not exist.

RCW 149

Coordinates: (8.72°, -0.51°)
[ See details ]

This large diffuse HII region, also called LBN 38, is near the Sgr OB1 association and the Lagoon nebula. According to Sharpless, it is associated with the B1 star HD 165516, which Humphreys places in the Sgr OB1 association. Gum also mentions the Wolf-Rayet star WR 111.

RCW 150

Coordinates: (9.3°, 0.3°)
[ See details ]

The RCW catalog describes this as a 2x2 arcminute bright object that is "Stellar in appearance".

There are no references in the scientific literature beyond the RCW catalog itself and there is no visible nebulosity at this location in SuperCOSMOS.

It seems likely that this nebula does not exist.

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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.