Gum 48a
Also called
RCW 75Coordinates: (306.19°, 0.18°)
[ Catalog | Explorer | SIMBAD ]
This HII region surrounds and is ionised by the young cluster Stock 16, which is part of the Cen OB1 association and contains the reflection nebula complex VdBH 60a, VdBH 60b, VdBH 60c and VdBH 60d. The region is probably physically connected to the huge and diffuse m Cen nebula.
Kharchenko lists 9 ionising members of Stock 16, including the O stars HD 115455 (O8) and DM -61 3587 (O 9.5 V) as well as 7 B-class stars. She gives a distance of 1640 parsecs and an age of 6 million years.
Dutra places the infrared star group [DBS2003] 86 in VdBH 60b at 2400 parsecs and the infrared star group [DBS2003]85 in VdBH 60d at 2100 parsecs.
Avedisova places this nebula in star formation region SFR 306.20+0.18, along with the emission star IRAS 13168-6208 and the dark cloud Dcld 306.2+0.1.
Although the little documented m Cen HII region is named after the prominent G6 II giant m Cen near its core, it is of course ionised by several much hotter OB stars. Avedisova calls this huge diffuse nebula Ge 136 and lists HD 116796 (O9 V) as the main ionising star, along with two B2 class stars. SIMBAD gives an O9 II class for HD 116796 but curiously appears to be missing the surrounding nebula all together.
You can view a larger image of RCW 75 here and the full extent of the nebulosity (including the huge diffuse m Cen nebula) in this SuperCOSMOS hydrogen-alpha image. You can also see RCW 75 at the edge of the far larger (and twice as distant) RCW 74 nebular complex in this Spitzer infrared image.
Kharchenko lists 9 ionising members of Stock 16, including the O stars HD 115455 (O8) and DM -61 3587 (O 9.5 V) as well as 7 B-class stars. She gives a distance of 1640 parsecs and an age of 6 million years.
Dutra places the infrared star group [DBS2003] 86 in VdBH 60b at 2400 parsecs and the infrared star group [DBS2003]85 in VdBH 60d at 2100 parsecs.
Avedisova places this nebula in star formation region SFR 306.20+0.18, along with the emission star IRAS 13168-6208 and the dark cloud Dcld 306.2+0.1.
Although the little documented m Cen HII region is named after the prominent G6 II giant m Cen near its core, it is of course ionised by several much hotter OB stars. Avedisova calls this huge diffuse nebula Ge 136 and lists HD 116796 (O9 V) as the main ionising star, along with two B2 class stars. SIMBAD gives an O9 II class for HD 116796 but curiously appears to be missing the surrounding nebula all together.
You can view a larger image of RCW 75 here and the full extent of the nebulosity (including the huge diffuse m Cen nebula) in this SuperCOSMOS hydrogen-alpha image. You can also see RCW 75 at the edge of the far larger (and twice as distant) RCW 74 nebular complex in this Spitzer infrared image.
This HII region surrounds and is ionised by the young (3-5 million year) cluster Stock 16 which is associated with the OB association Cen OB1. The area also probably includes the adjacent m Cen nebula.[1]
The m Cen nebula is entry 136 in Georgelin and Georgelin's nebula catalog. [2]
The m Cen nebula is entry 136 in Georgelin and Georgelin's nebula catalog. [2]
Notes
1. ^ Turner, D. G. (1985). "The young open cluster Stock 16 - an example of star formation in an elephant trunk?", The Astrophysical Journal, Vol. 292, 148-154. [1985ApJ...292..148T]
2. ^ Georgelin, Y. P. & Georgelin, Y. M. (1970). "Radial velocities and distances of galactic H II regions.", Astronomy and Astrophysics, Vol. 6, 349-363. [1970A&A.....6..349G]
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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.