Target

The eighth stage of ShaRA project led us on a beautiful trio of galaxies: NGC 3169, NGC 3166 and NGC 3165.
The former, is a spiral galaxy about 75 million light-years away in the constellation Sextant, of SA(s)a pec type, i.e., pure, unbarred spiral galaxy with tightly coiled arms and peculiar features: in fact, it has an asymmetric spiral arm and a deformed extended halo all around the main body. It is a member of the NGC 3166 group of galaxies, which in turn is part of the Leo II groups, a series of galaxies and galaxy clusters that emerge from the right edge of the Virgo supercluster.
It is a LINER 2 galaxy that exhibits extensive X-ray emission in the core region, most likely due to the presence of an active galactic nucleus (AGN) and thus a super massive black hole at the center. The stellar population in the core appears to be very young (1 billion years old) and is arranged along a ring with an angular radius of about 6″. This suggests that a star-forming explosion took place in the core about a billion years ago and that strong AGN activity was the contributing factor.
The second one, NGC 3166, is a lenticular galaxy with an estimated separation from NGC 3169 of about 160 kly (50 kpc) and is interacting gravitationally with it. The resulting gravitational distortion has deformed its disk. Also in the “cosmic vicinity” is NGC 3165, smaller and classified as SA(s)dm. The three galaxies are embedded within an extended ring of neutral hydrogen centered on NGC 3169. Huge bridges of matter and stars eventually unravel from one galaxy to another, with the presence of stellar clusters that have the appearance of dwarf galaxies being part of the group.

The collaboration

As usual, also this project was financed with the contribution of all the members of ShaRA Team but only 3 of them decided to join forces to create an "Astrobin version" of the project (me, Simone Curzi and Andrea Iorio).
We used the Chilescope T1 (RC1000 f/6.8) working in a classical LRGB composition. We then mounted 44 frames of 600s in Luminance and 19 frames of 600s for each RGB color channel (all in bin1), for a total of about 17 hours of exposure. 

Personal contributions and merging

Following are the 3 personal elaborations of me, Simone and Andrea.

Massimo's version (rev. C):


Simone's version (rev. D):


Andrea's version (rev. E):


The final image (the "Astrobin version") was obtained merging the 3 personal images with Pixelmath in PixInsight, using the following formula: Massimo*0,4+Simone*0,4+Andrea*0,2.
The coefficients were decided according to the results of the votation af all the Team images.

Extra contents

To play a little bit, Alessandro Ravagnin (the Boss of ShaRA) produced also the inverted and “pumped-up” version, that shows very interesting features, to best highlight the morphology of the wonderful cluster of interacting galaxies. Analyzing the tidal tails, one can see two distant arms of NGC 3169 that appear to have been targeted and punctured probably by a satellite galaxy that passed through them tangentially and smeared itself in the passage, creating those two “holes” (a similar situation is clearly visible in the Spitzer shots of an arm of M31, “punctured” by one of several passages made by M32).
Below the inverted picture (rev. F) and the detail of the strange arms of NGC 3169 (rev. G).