Review of "Bubble-Like" Nebula in Cygnus Aug 2008

































Possible Undesignated "Bubble-Like" Nebula in Cygnus

 

Keith B Quattrocchi MD, PhD and Mel Helm, MD 

August 9, 2008

Copyright 2008

Keith B Quattrocchi

 

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Ha & NB Image of the Bubble-Like Nebula in Cygnus
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Imaged by Keith B Quattrocchi, MD, PhD

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As previously noted, we believe this nebula to be 'co-imaged" (again, pending the findings of the IAU, "discovered" would be technically less accurate, as it may be present in a catalogue or paper we have not seen), first by Dave Jurasevich (of the Mount Wilson Observatory) on July 6, 2008 and submitted by him to the IAU on July 10, 2008.  His images were not posted at the time of our independant "discovery" (or at least, "independant imaging") of July 17, 2008.  He deserves recognition as being the first to image and submit this object (again, pending any prior submissions noted by the IAU or other professional sources).  You can learn about Dave's excellent work at www.starimager.com and about his initial images of this nebula at http://tinyurl.com/5q4qnu

 

As for our work, on July 17, 2008, Dr. Mel Helm noticed an unusually symmetrical and "Bubble-Like" HII object in a wide field image he had taken (that evening) of the Crescent Nebula.  The image, shown below, was imaged at Sierra Remote Observatories.  This image was an average eight separate 10 minute sub-exposures with the FLI Microline 16803 and the Dream16” Astrograph on a Chronos HD32 mount.  The image below (Figure 1A) shows the initial image of the Crescent Nebula and the difficult to see bubble to the lower left.  Figure 1B shows the object, as originally circled, by Dr. Helm.  One interesting note.  When first posted we got an email from a noted planetary nebula hunter, Kent Wallace, who noticed the original image was a mirror image (Mel's images below have been properly flipped and rotated).  As with so many aspects of this "adventure", help seems to come from many places.  We appreciate his email and careful observation of Mel's orignial image.  I knew I was getting a headache using that orignal image to find the exact location of the "bubble" on "The Sky", and now I know why (what I don't know is why I didn't notice !).  You can check out Kent's work at http://www.ccastronomy.org/members_work_wallace.htm and his southern sky work at http://www.ccastronomy.org/members_work_wallace_australia.htm . 

Figure 1A: Crescent Nebula
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Imaged by Dr. Mel Helm, July 17, 2008

Figure 1B
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Imaged by Dr. Mel Helm July 17, 2008

Dr. Don Goldman reviewed older images of this region and circled the area of the object, in which a faint area of definition could be seen.  The resolution was poor, but it clearly required further inspection to determine whether it was real or artifactual, and if real, whether it was already designated.  Don wondered if this might be a Wolf-Rayet star. 

 

    At this point Mel and I talked further and we decided I should attempt to image this object in order to determine whether it was real (ie, a relatively symmetrical "bubble-like" object) and to find the objects exact location.  This was accomplished using my16” RCOS at prime, with it’s SBIG STL-6303/AOL.  The initial location was obtained by matching the star pattern of the object to Software Bisque’s “The Sky”, as shown below (Figure 3)

Figure 3:
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Figure 4 shows the first image (compilation of several 20 minute sub-exposures) from July 29, 2008, intentionally oriented in the same direction as “The Sky” image, above. 

 

Figure 4
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Imaged by Keith B Quattrocchi, MD, PhD, July 28, 2008

 A few calculations were then made of the image.  The image scale of my ion milled f/9 16” RCOS at prime is 0.51 arc-sec/pixel (i.e., imaging at prime f/9 with ion milled optics, aperture of 406 mm, FL of 3654, using a STL-6303 with 9 micron pixels at 3072 x 2048, chip size of 18,4 x 27.6 mm, all binned 1x1).  This yields a FOV of 17.3 x 26 arc-min.  In CCDStack the object measures with a diameter of 464 (height) x 496 (width) pixels in height, which gives an average of 480 pixels.  This calculates to the bubble size (diameter) of about 244 arc-sec, or 4.08 arc-min diameter.  The area would be 13.07 arc-min squared. 

 

            A noted Astrophysicist at Fresno State University, Dr. Frederick Ringwald, recommended that we check to see if the object has a designation in two stages.  The first was to check Skyview (http://skyview.gsfc.nasa.gov/), in particular its H-alpha survey, in order to get reasonable coordinates (right ascension and declination within a few arc seconds), and then feed these coordinates into the Simbad database (http://simbad.u-strasbg.fr/simbad/).  This was then done.  Although the Ha Comp view did not show useful images, the DSS images were available and did faintly demonstrate the object, as shown below (Figure 5)

Figure 5
figure5dssbubblecenter.jpg

                                                      X,Y: 147,145 -> J2000.0: 20 15 22.16 +38 02 41.9  

 

This gave us reasonably good coordinates:

RA: 20 15 22.16 and Dec +38 02 41.9

 

Using this information the Simbad site was used to look for objects with designations in this region.  The map which follows (Figure 6) is the closest map we were able to obtain, and the exact coordinates of the object are just to the right of the “X”, designating an X-ray object which is to the left of center, but within (but not centered in) the “Bubble”.   The quality of the downloaded plot is poor, but it can be gotten directly at the site (just below image).

Figure 6
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The actual link to the plot map is:

 http://simbad.u-strasbg.fr/simbad/sim-plot?coo=20+15+22.16+%2B38+02+41.9&ident=1RXS+J201523.8%2B380321&radius=10&radius.unit=arcmin&submit=plot+this+list+of+objects

 

If you click on the X-ray object, you get the image below.  The bubble is faint, but it’s center is just to the right of the X-ray source.  Since the FOV is 12.9 x 12.9 arc-minutes, the X-Ray source would be about 1.8 arc-minutes from the approximate center of the “Bubble”.  Note, the coordinates of the center of the “Bubble” are 20 15 22.16, +38 02 41.9, which differ from the X-Ray source, as noted in the plot below

 

See Figures 7 and 8 (image blown up), below.

Figure 7
figure7.xraysource.jpg

Figure 8 is a blown up DSS image of the above link with the approximate location of the “Bubble” circled, and therefore the X-ray source would presumably, if the image is centered properly, be off center from the “Bubble”.

Figure 8
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Other sources of prior information were also carefully checked. These sources include the Palomar Sky Survey images and the Harvard ADS abstract database, and other sources (this is detailed in the link:  www.lostvalleyobservatory.com/iaupncyg ), as requested by Dan Green of the IAU.  Based on this information the “Bubble” discovered near the Crescent Nebula may be an undesignated object.  It has been suggested, by Dr. Ringwald, that this could be a Wolf-Rayet bubble (like the Crescent Nebula), a true “Bubble Nebula” (such as NGC 7635), or an unusually symmetrical planetary nebula (such as Abell 39).  Determining whether the object is designated is still ongoing as of August 9, 2008. 
The Narrow Band Image of this object is shown below (Figure 9), or can be seen at the following link:  http://www.lostvalleyobservatory.com/page29crescentbubblenb/
The “Bubble” had a rich Ha and OIII content, accounting for the teal appearance.  The globular Ha region below the “Bubble” has been imaged and designated previously, as shown on the plot map above (as “HII rich regions”).

Figure 9
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Imaged by Keith quattrocchi, July 28-Aug 3, 2008

   Below, Figure 10, is a compsite of the original image by Mel Helm and the Narrow Band confirmatory image by myself, assembled in Photoshop CS/3.  It nicely shows the location of the object with respect to the Crescent Nebula and shows the difference in orientation between the two images. 

Figure 10
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Composite of Cygnus and Possible Undesignated "Bubble" Nebula

  At this point we believe this object is not designated (as of August 10, 2008).  As more information becomes available we will post such information on this page.  We hope you enjoyed this summary.  It has been an exciting and new experience from Mel and I, one we hope to repeat.  We intend to continue to take advantage of our very differing systems which work togther well in this setting.  Mel will continue his wide field of view imaging, using his short focal length Astrograph (16" Dream) and highly sensitive camera (FLI 16803).  When we find an area of interest then we'll point my longer FL RCOS (16" ion milled RC) and STL-6303 at the object, in order to get a "bettter look" in order to see if we have found a new object.  Whether this (or any other) object already has a designation or not will have no effect on the importance of this experience to us. 
















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