The RCW Catalog

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RCW 151

Coordinates: (10.95°, -1.65°)
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Sh 2-35 and Sh 2-37 are part of a 130 thousand solar mass giant molecular cloud. Sh 2-35 appears along the western edge of this cloud. Sharpless connects this nebula to a number of stars, the hottest of which is the B0 IVPE star HD 312973, which Humphreys locates in the Sgr OB7 association.

SIMBAD reports that HD 312973 is actually an O-class star.

RCW 152

Coordinates: (12.3°, 4.3°)
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The RCW catalog describes this as a 2x2 arcminute medium bright object that is "Stellar in appearance". There is no visible nebulosity at this location in SuperCOSMOS and no references in the scientific literature beyond the catalog itself.

It seems likely that this nebula does not exist.

RCW 153

Coordinates: (12.2°, -1.8°)
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RCW 153 is a faint nebular ring that includes the much brighter Gum 78 (Sh 2-37 / RCW 153a).

RCW 153a

Coordinates: (11.63°, -1.78°)
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Sh 2-37 lies in the direction of the ionising star cluster Dias 5. It is also known as IC 1283/1284 and the powerful radio source W 34.

Sh 2-35 and Sh 2-37 are associated with a 130 thousand solar mass giant molecular cloud and appear to be part of the Sgr OB7 association. Sh 2-37 is visible through a hole in this molecular cloud. This is a very active star formation region.

You can find an infrared image of part of this region here, full colour images here and here, and an analysis of the correct names for these objects here.

RCW 154

Coordinates: (12.7°, 2.0°)
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This faint diffuse nebula is visible in SuperCOSMOS surrounding the B0 III multiple giant LS 4659, which is the ionising star according to Vogt and Moffat.

RCW 155

Coordinates: (12.72°, 0.35°)
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Sh 2-40 appears as several bright knots of nebulosity extending above the much larger nebula Sh 2-41.

Avedisova suggests that Sh 2-40 is ionised by the B-class star LSS 4756.

The RCW catalog lists the bit of Sh 2-40 that is furthest from the galactic plane as RCW 155a and the brighter bits closer to the galactic plane as RCW 155b.

RCW 155a

Coordinates: (12.83°, 0.47°)
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RCW 155a consists of the larger and dimmer nebular knot within RCW 155 that lies further from the galactic plane.

RCW 155b

Coordinates: (12.82°, 0.35°)
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RCW 155b consists of the three brighter nebular knots of RCW 155 that lie closer to the galactic plane.

RCW 156

Coordinates: (13.52°, -0.4°)
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This faint diffuse nebula is close in direction to the suspected supernova remnant GAL 013.1-00.5 and appears to be located in an empty region bordered by the OB regions Sgr OB1, Sgr OB7 and Sct OB3.

Avedisova places Sh 2-43 / RCW 156 into star formation region SFR 13.62-0.76 along with two infrared sources and many molecular clouds.

No ionising star for Sh 2-43 has been identified in the scientific literature and no ionising star in this direction appears in the Reed catalog or SIMBAD either. The bright star in this image is the K2 III giant HD 167720.

RCW 156a

Coordinates: (13.68°, -0.45°)
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This is a slightly brighter region within the diffuse nebula RCW 156. The bright star in this image is the K2 III giant HD 167720.

RCW 157

Coordinates: (14.2°, -0.1°)
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This huge almost circular nebula is very prominent in hydrogen-alpha as can be seen in this SuperCOSMOS image.

Avedisova concludes that it is ionised by the O6 V star HD 167633. Humphreys places this star in the Ser OB1 association in the Sagittarius arm.

However, several other sources give larger distance estimates, placing this nebula in the Centaurus arm, where it may be part of the Scutum supershell.

RCW 158

Coordinates: (15.18°, 3.33°)
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This isolated nebula is located well above the galactic plane.

Avedisova concludes that it is ionised by the potential runaway O9.5 Iab supergiant HD 165319, which may have been ejected from NGC 6611, the central star cluster of M 16, the Eagle nebula, about 1.8 million years ago.

RCW 159

Coordinates: (15.3°, -1.8°)
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This mysterious faint ring appears below M 17 in the direction of the supernova remnant SNR 015.1-01.6. Although some filaments are visible, the image in SuperCOSMOS resembles a diffuse ring nebula rather than a filamentary supernova remnant. However, no central ionising star is mentioned in the scientific literature, the Reed OB star catalog or SIMBAD,

Papers published in 2008 and 2011 show that the hydrogen-alpha emission matches the radio emission from the supernova remnant closely, providing strong evidence that RCW 159 is identical to SNR 015.1-01.6.

Oddly, none of the researchers who published these papers appear to have realised that the hydrogen-alpha nebula they were studying was already catalogued as RCW 159!

RCW 160

Coordinates: (15.1°, -0.7°)
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This is M 17, the Omega nebula, also called W 38, the Swan nebula, and the Lobster nebula among other names. This nebula is found in the Ser OB1 association.

M 17 is ionised by an O4V-O4V double star system (Kleinmann's star) at the core of the massive young cluster NGC 6618 (about one million years old), which contains over 800 stars, including 2 O5V star systems and 100 stars hotter than B9 (by comparison, the Orion nebula contains 8 stars hotter than B9). The total ultraviolet flux is about 25 times higher than for the Orion nebula.

A large part of the nebula is hidden by a dark dust lane that runs near the central cluster and splits the main visible nebula (Gum 81a) from two attached nebulae on the other side of the dust lane (Gum 81b - IC 4706 and IC 4707).

M 17 is a blister on the side of a much larger giant molecular cloud and star formation region (M 17SW) that contains 30 thousand solar masses of molecular hydrogen.

You can see a more detailed image of part of this massive star formation region and view a good overview of this entire region.

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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.