The RCW Catalog

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RCW 161

Coordinates: (16.1°, -0.3°)
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RCW 161 is a large faint region of diffuse nebulosity located between the Eagle and Omega nebulae. It appears to form a connecting link between these much brighter HII regions. RCW 161, like the Eagle and Omega nebulae, appears to be ionised by members of the Ser OB1 association.

It is not clear that RCW 161 is a single object as the ionising stars in this direction appear to be spread across several hundred parsecs.

RCW 162

Coordinates: (16.6°, -0.3°)
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This nebula may be associated with the Scutum supershell in the Centaurus arm.

Avedisova places it in star formation region SFR 16.65-0.34 along with the molecular clouds SYCSW 164, SYCSW 164A and SRBY 52. She concludes that Sh 2-48 is ionised by the O8 V multiple star ADS 11285.

The newly discovered dense star cluster Kronberger 25 appears in the same direction as Sh 2-48, although a tentative distance estimate for this cluster of about 2000 parsecs suggests that it may be a foreground object.

RCW 163

Coordinates: (16.9°, -2.3°)
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RCW 163 is the optically brightest portion of a huge faint nebula below the galactic plane. It is much more visible in infrared as can be seen in this MSX image. Polycyclic aromatic hydrocarbons (PAHs) have been detected in this HII region, which is the bright spot below the right side of the arrow head formed by the dark nebula LDN 379.

Avedisova places RCW 163 in the star formation region SFR 16.84-2.32 with LDN 379, 6 masers and several infrared sources including IRAS 18265-1517, IRAS 18277-1517, and IRAS 18277-1516.

RCW 164

Coordinates: (16.93°, -1.07°)
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Sh 2-50 appears in the direction of the Sct OB3 association and the star cluster Dolidze 28, which has the Wolf-Rayet star WR 115 as its central star.

RCW 165

Coordinates: (16.8°, 0.75°)
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This is M 16, the Eagle Nebula. It is part of the W 37 molecular cloud and is ionized by the NGC 6611 star cluster, which is part of the Ser OB1 association in the Sagittarius arm. NGC 6611 is dominated by the massive and superhot O3.5V+O7.5V class multiple star HD 168076, which has 75-80 solar masses and provides about half the ionising radiation for the nebula.

There is a much better image of the Eagle nebula here. A region of M 16 was the subject of perhaps the most famous Hubble space telescope image, the 1995 Pillars of Creation.

RCW 166

Coordinates: (18.2°, -0.3°)
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Sharpless notes that Sh 2-53 consists of "About six detached portions". The area is prominent at both radio and infrared frequencies.

Avedisova places the nebula in the complex star formation region SFR 18.18-0.30, which includes 4 molecular clouds, a methanol maser and at least 4 additional HII regions visible at radio and infrared frequencies.

You can view a good black and white hydrogen-alpha image here.

RCW 167

Coordinates: (18.7°, 2.0°)
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This HII region is ionised by the young NGC 6604 star cluster, which includes the O5-8V+O5-8V+O8I supergiant multiple HD 167971 and the radio source W 35. It lies, unusually, about 70 parsecs above the galactic plane within the Ser OB2 association.

Ser OB2 contains over 100 OB stars with a common age of about 5 million years.

A good image of this nebula, which looks like a nest (Gum 84) carrying a tiny egg (Gum 85), can be seen here.

RCW 168

Coordinates: (21.3°, 2.5°)
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The RCW catalog describes this as a 1x1 arcminute bright object. There is no visible nebulosity at this location in SuperCOSMOS and no significant references in the scientific literature beyond the RCW catalog itself.

It seems likely that this nebula does not exist.

RCW 169

Coordinates: (21.97°, 0.06°)
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This HII region is visible in infrared as the luminous water maser GAL 021.88+00.02.

RCW 170

Coordinates: (22.6°, 0.3°)
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The RCW catalog describes this as a faint 7x5 arcminute nebula. There is no visible nebulosity at this location in SuperCOSMOS and no significant references in the scientific literature beyond the RCW catalog itself.

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.