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Galaxy Quartet NGC 3169, NGC 3166, NGC 3165, NGC 3156, and PGC 1253132, Sextans

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#1 rekokich

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Posted 12 February 2019 - 10:40 PM

Galaxy Quartet NGC 3169, NGC 3166, NGC 3165, NGC 3156, and PGC 1253132, Sextans

I had been disappointed in the quality of the subs for this image, and left them in storage for nearly two years. When I finally processed them last week, I still wasn't impressed with the result until I compared it to the Digitized Sky Survey 2 (DSS2) images taken with the Palomar 48 inch Schmidt astrograph. My tiny 4 inch astrograph showed nearly the same detail! This clearly illustrates the triumph of modern semiconductor and software technologies.

The image is a 25% crop of 14 x 240 sec exposures, iso 1600, Taken with the TSAPO100Q astrograph, Celestron AVX mount, unmodified Canon 600D camera, Sigma APO 1.4x tele-extender, and Orion 60mm F/4 SSAGpro autoguider. No filters were used. It was processed with DSS, XnView, StarTools, and Neat Image. At full resolution, the limiting magnitude is 18.5.

 

NGC3169 NGC3166 NGC3165 NGC3156 Sext 20170327-EL TS100 1.4x 100-812 2x 14x240''-1600-O-30F.jpg


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#2 rekokich

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Posted 12 February 2019 - 10:41 PM

DSS2 survey.jpg


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#3 rekokich

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Posted 12 February 2019 - 10:43 PM

NGC3169 NGC3166 NGC3165 NGC3156 Sext 20170327-ELA TS100 1.4x 100-812 2x 14x240''-1600-O-30F.jpg

 

 

NGC 3169 is an unbarred spiral galaxy with an asymmetrical arm and an extensive halo. Its nucleus is classified as a LINER, or a "low-ionization nuclear emission-line region" characterized by spectral emission from neutral or weakly ionized atoms. Its nucleus is also a source of high energy, short wavelength X-rays presumed to be generated by the accretion of matter around a supermassive black hole. According to the Simbad database, the galaxy has the apparent magnitude of 12.4, angular diameter of 4.2 arcmin, and spectroscopic redshift of 0.004180, which indicates it lies at the distance of 58 million LY, and is receding from us at 1253 Km/sec. The red H-II ring around the nucleus, and spectroscopic analysis revealing young stellar populations near the core suggest starburst activity in the central region which started about one billion years ago.

NGC 3169 is gravitationally bound to galaxy NGC 3166 (Mg = 11.3), and is connected to it with a delicate stream of matter spanning about 160,000 LY. Small galaxies NGC 3156 (Mg = 12.8) and NGC 3165 (Mg = 14.4) constitute two more members of the group, all enveloped by an immense cloud of neutral hydrogen gas. The quartet, lying within a volume of space about 500,000 LY in diameter, is a member of the Leo 1 galaxy group, which itself lies within the Virgo Supercluster.

PGC 1253132 is the most distant identified galaxy in the attached image. According to the Simbad database, its magnitude is 16.6, and angular diameter 0.34 arcmin. From its spectroscopic redshift of  0.06926, its proper recession speed can be calculated to be 20,764 Km/sec, and its proper distance 948.3 million LY. Taking into account the expansion of the universe during the time the light travelled, the "lookback time", or light travel time, is 917 million years. From its angular diameter, A = 0.34'/60 = 0.005667*, and distance D = 948.3E6 LY, we can calculate the diameter, S, of the galaxy to be:
S = D x Tan A = 948.3E6 x Tan 0.005667 = 93,788 LY, or approximately the same as the Milky Way.
From its apparent magnitude, m, and the distance in parsecs, D = 948.3E6 / 3.26 = 290.9E6, we can calculate the absolute magnitude of the galaxy as follows:
m - M = ( 5 x log D) - 5
M = m + 5 - ( 5 x log D ) = 16.6 +5 - ( 5 x log 290.9E6 ) = 21.6 - 42.32
M = -20.72
Absolute magnitude of the Milky Way is -20.6. PGC 1253132 is remarkably similar to our own galaxy in size and luminosity, and serves as an example of what we might look like from the distance of nearly one billion LY.

Arrows indicate several other distant galaxies which are not identified on DSS2.

Thank you for looking. C&C welcome.

 

 


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