Please remember to click on the FULL image to scroll around and enjoy the background galaxies.

NGC 3660 is a galaxy that has been on my radar for more than 20 years. My first attempt was in 2003 with the 20-inch telescope I was using at the time for the public programs I was running at Kitt Peak National Observatory. Later I attempted it again 2010 with the 24-inch telescope (identical to the one I am using) when I was at Mount Lemmon SkyCenter. I founded the SKyCenter in 2008 and the 24-inch was on loan to me from RCOS ( I can be persuasive! ) while they were building the 32-inch telescope for me.

At each of these prior attempts there was something always very wrong with the images such that I did not pursue making a final great image. I believe I did publish the 2003 image at the time on a webpage and what was called the SBIGUSER group- the Astrobin of the day.

📷 2003 Image (Kitt Peak)📷 2010 image (SkyCenter)The 2003 Kitt Peak image suffers from TDE (Turned Down edge) from the primary. Later the telescope’s primary was masked and completely cleaned this up. The 2010 image suffered from the scattered light disease that sometimes happens when bright stars are outside of the field and scatter light. There is really (currently) no great fix (though I show a few on my site). I was not happy with the data for this image and the scattered light just soured my motivation to continue.

That being said, both of these images ARE USEFUL in light my new image. If you look closely at this image you will note there is an extra star in the galaxy. This is a recent supernova. The moment the first images rolled in (back in March) I instantly noted this star looked out of place. However, a short bit of research found that I had missed discovery by one month. You can read about it here.

I have accidentally (serendipitously) found a supernova in NGC 6240 many years ago using this “random” luck method. :)

📷 NGC 3660 with SN labeled with red arrow.It is remarkable what 20 years of improvement in equipment and technique can do as seen in the comparison.

However, by far the most interesting thing in this field that I have not talked about yet is the beautiful ringed galaxy PGC 1000714. This galaxy was famously (resulted in TED talks) studied by astronomer Dr. Burcin Pakdil in 2017. Most embarrassingly she uses my old crappy TDE image in her talk! Damn. I wish she had this one! As of the date I took the picture in 2003 I may have been one of the few humans in the world that knew about this ring galaxy. It isn’t clear when the classification was given or the source. I am pretty certain there are some references. However, I am more certain that as crappy as it is/was… the old 2003 image was probably the first high-resolution (color) image of this field that shows not only NGC 3660 but also Burcin’s galaxy.

This galaxy at first appears to be a Hoag’s type galaxy. The paradigmatic example was made famous by an HST image and is seen in the image I took below many years ago:

📷 Hoag’s Galaxy (See large version by clicking on this image…I really need to revisit this… )📷 HST of Hoag's Object Hoag's_object.jpg PGC 1000714 is an exceptionally rare galaxy located approximately 359 million light-years away in the constellation Crater. While it superficially resembles a Hoag-type galaxy, which represents less than 0.1% of all observed galaxies, the 2017 photometric study by Mutlu-Pakdil et al. revealed something entirely unprecedented: two distinct, fairly circular rings surrounding a pure elliptical core. The inner ring is a faint and diffuse stellar population of old reddish stars, while the outer ring is blue and actively forming stars. No galaxy with this precise double-ringed, non-barred elliptical structure had been described in the literature before this work.

What makes PGC 1000714 particularly compelling is that these two rings tell different stories. They have distinct stellar population ages which means they did not form together. The central body itself is essentially a naked elliptical suspended inside two rings of very different origins. The authors conclude that a recent accretion event is the most plausible explanation, with infalling material triggering ring formation at separate epochs. It represents an extreme case that challenges secular evolution models and continues to inform how rings form in galaxies.

The method they used to tease out this information is similar to what I did with the recent 3C273 quasar image. They subtracted a source from the data (central elliptical) and looked at the residuals. In my case I used a field star as a model PSF function to subtract from the quasar. But in this case there isn’t an example in the data. Instead the astronomers created a synthetic model of the correct intensity profile to subtract. Look at the bottom row of the figure from their paper. You can see how the “ring” appears in the R (red filter basically) filtered image after subtraction. It is pretty subtle. It does not appear as strongly in the other filters which is how the color of the stars is known. The other rows indicate subtractions with different fitting parameters.

📷 Burcin_figure_8_ab.jpgThis figure is found in A photometric study of the peculiar and potentially double ringed, non-barred galaxy: PGC 1000714 Burçin Mutlu Pakdil ,Mithila Mangedarage ,Marc S. Seigar ,Patrick Treuthardt

Monthly Notices of the Royal Astronomical Society, Volume 466, Issue 1, April 2017, Pages 355–368, https://doi.org/10.1093/mnras/stw3107 30 November 2016

Again..the background has some amazing far-away galaxies. Here are just a few…but you should look at the full image to find more.

📷 📷 background_galaxies2.jpg📷 Lensing?In the last example above I note that some background galaxies make a curious arc near a massive elliptical galaxy (left of nucleus) in the foreground. I am not saying it is lensing… but I am saying it just in case it is. :)

On a final note with regards to the background galaxies- 95% of sources in this image are easily galaxies. The background is awash with small mostly red, yellow and a few blue star-like objects. Most are not stars at all. Before the use of BXT (which I used modestly here at a non-stellar amount of “30”) all faint stars and galaxies are quite fuzzy. However, for most of these I am only detecting the brighter nuclei of the galaxies. After BXT these tiny things sharpen a bit and it is not possible to distinguish them from stars. But when you look at the end all of that “stuff” that is seen… pretty much galaxies on almost every pixel.

One final note- because its a small world….

I work at the department of astronomy at the University of Arizona (Steward Observatory) and Burcin worked there around 2018 and for some odd years afterwards as a postdoc. I believe she used to be in a room across from another I would frequent in the building. We shared something in common though decades apart. I was always fascinated with this ringed galaxy and knew it was special. Not but 30 feet away a young lady would eventually find it equally interesting- and here we are in the same place each not knowing the shared galactic interest. I actually only put this together while creating this writeup.