Sh 2-4
Also called
RCW 121Coordinates: (348.2°, -1.0°)
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Infrared imagery reveals that RCW 121 (Sh 2-4) and RCW 122 lie at the edge of an enormous bubble ionised by the star cluster Havlen-Moffat 1. This cluster is 2-4 million years old and contains the Wolf-Rayet stars WR 87 and WR 89 as well as several O-stars.
Vazquez and Baume provide a good overview of Havlen-Moffat 1, which may be associated with this HII region. [1]
It contains the infrared cluster [DBS2003] 118 at a distance of 2700 parsecs. [2]
Avedisova places it in star formation region SFR 348.31-1.05 with 2 masers and the radio source CTB 38.
The larger region around RCW 121, RCW 122 and RCW 123 (Sh 2-5) is spectacular in infrared. This Spitzer image shows only a part of this region. While not as detailed, this MSX image shows a wider view of the region in which the compact HII regions RCW 121 and 122 are seen to be bright knots at the rim of a vast star forming cavity centred on the ionising cluster Havlen-Moffat 1 and filled by the diffuse HII region RCW 123.
Curiously, a 2009 paper by Arnal, Duronea and Testori uses the 1972 distance estimate of 5000 pc despite the fact that this estimate was computed using the now discredited kinematic technique. The 2009 authors give no reason for this choice. [3] The lower estimates of approximately 3000 pc use photometric techniques and are more likely to be accurate.
It contains the infrared cluster [DBS2003] 118 at a distance of 2700 parsecs. [2]
Avedisova places it in star formation region SFR 348.31-1.05 with 2 masers and the radio source CTB 38.
The larger region around RCW 121, RCW 122 and RCW 123 (Sh 2-5) is spectacular in infrared. This Spitzer image shows only a part of this region. While not as detailed, this MSX image shows a wider view of the region in which the compact HII regions RCW 121 and 122 are seen to be bright knots at the rim of a vast star forming cavity centred on the ionising cluster Havlen-Moffat 1 and filled by the diffuse HII region RCW 123.
Curiously, a 2009 paper by Arnal, Duronea and Testori uses the 1972 distance estimate of 5000 pc despite the fact that this estimate was computed using the now discredited kinematic technique. The 2009 authors give no reason for this choice. [3] The lower estimates of approximately 3000 pc use photometric techniques and are more likely to be accurate.
Notes
1. ^ Vázquez, R. A. & Baume, G. (2001). "The open cluster Havlen-Moffat No. 1 revisited", Astronomy and Astrophysics, Vol. 371, 908-920. [2001A&A...371..908V]
2. ^ Dutra, C. M., Bica, E., Soares, J., et al. (2003). "New infrared star clusters in the southern Milky Way with 2MASS", Astronomy and Astrophysics, Vol. 400, 533-539. [2003A&A...400..533D]
3. ^ Arnal, E. M., Duronea, N. U., & Testori, J. C. (2009). "The molecular complex associated with RCW 121 and RCW 122", Revista Mexicana de Astronomia y Astrofisica Conference Series, Vol. 35, 48-49. [2009RMxAC..35...48A]
Distance estimates
2510 pc [2003A&A...397..213P]3300 pc [2001A&A...371..908V]
2900 pc +/- 400 [1977A&A....58..351H]
5000 pc [1972ApJS...24...49R]
2700 pc [2003A&A...400..533D]
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Most of the sources used to create these nebula descriptions are listed in the
notes section for each description. In some cases,
for example the Avedisova, Humphreys and Reed catalogs, the source is used extensively and is not listed in the
individual nebula descriptions. See this catalog overview
for more information on the catalogs and the general sources used
to create these descriptions and this introduction to HII regions
on the general history of this area of astronomy.
This image was 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.