35 replies to this topic

[Pcbessa]

I just spotted the galaxy LEDA 1561869.

Like SNH reported, I also had several glimpses, it was easier than I thought. I saw it with my 10". And it was a dark and dry night tonight. I saw also a few nearby mag 15.5 stars near the galaxy.

And saw also Leo I and Sextans B galaxies, also quite faint targets.

[timokarhula]

Last night, I was also able to glimpse the distant galaxy LEDA 1561869 (PGC 1561869) in the cluster Abell 900 (Leo) with my 12-inch Dob.  I believe I could see the galaxy already in March, but I wanted to have another observation of it and to see a fainter star than LEDA 1561869 in the field.  During more than a half an hour of concentration and using magnifications up to 434x, I got several glimpses of LEDA 1561869 and it was about as difficult as a V=16.0 field star.  The galaxy did not look sharp to me which indicates that I could see it as an extended object (Simbad says 0’.27x0’.21).  LEDA 1561869 is my new personal galaxy distance record!  My sky darkness in my back-yard was SQM-L 21.44.  April nights are fine!

 

/Timo Karhula

[quazy4quasars]

Last night, I was also able to glimpse the distant galaxy LEDA 1561869 (PGC 1561869) in the cluster Abell 900 (Leo) with my 12-inch Dob.  I believe I could see the galaxy already in March, but I wanted to have another observation of it and to see a fainter star than LEDA 1561869 in the field.  During more than a half an hour of concentration and using magnifications up to 434x, I got several glimpses of LEDA 1561869 and it was about as difficult as a V=16.0 field star.  The galaxy did not look sharp to me which indicates that I could see it as an extended object (Simbad says 0’.27x0’.21).  LEDA 1561869 is my new personal galaxy distance record!  My sky darkness in my back-yard was SQM-L 21.44.  April nights are fine!

 

/Timo Karhula

I first posted about this Galaxy (also known as 2MASX J09562806+1831023 or OGC 68) back in April 2019 -after the OGC was published (See the thread "Distant Galaxies and Clusters") - and that suggestion was based on the very high stellar density of its inner regions compared to almost all other sources at a similar red-shift to be found in that awesome list of the most luminous galaxies in the local (z<.3) universe:

 

 http://simbad.u-stra...ApJS..243...14O

 

 Of the 1527 optically luminous galaxies listed, a few are visible in 10"-12" where conditions allow.  It's easy to forget that one is looking at one of the very largest and brightest of galaxies, many times brighter then the Milky Way or M31, or even M87 and the Giants of Coma.  Galaxies as intensely bright as this are rare, literally one in a million. 

 

 Great Job and thanks for sharing your successes!  You guys are hard-core.  Q4Q is proud of you.   

Edited by quazy4quasars, 07 April 2021 - 02:35 PM.

[SNH]

Thanks Q4Q for letting me know that it was you who first brought LEDA 1561869 to our attention a few years ago! Great job by the way on doing so -- it allowed me to be possibly the first person to ever see an entire galaxy 2 billion light-years distant with a 10-inch!! I first learned of it from @Starman1, who did tell me that he had learned of it from a post here on CN. Suspected it was from you...

 

Hey, Q4Q, you write "Of the 1527 optically luminous galaxies listed, a few are visible in 10"-12" where conditions allow." If you have any other galactic suggestions to pass along for our "small" telescopes, please feel free to do so! I can usually look at a 15' wide DSS image and decided if I have a chance at seeing it with my 'scope.

 

 

Scott

[quazy4quasars]

  Hi, Scott,  No doubt it would profit you greatly to review the "Distant Galaxies and Clusters" thread as well as "The three-Billion light-year club" and "The one billion light-year club"  as some of the galaxies posted therein by myself and others would yield within the grasp of your excellent detection skills.  

 

  I spent a lot of time evaluating Mr. Ogle's catalog entries as well as searches of several vizier and other catalogs on luminous BCGs and shared what I considered to be many of the likeliest to see based on my experience and other criteria, many of them are also on Starman1's list.  

 

   IC2657,  2MASX J17120987+6143147,  PGC 60004  leap to mind.  Also, the other very odd Galaxy I mentioned, PGC 1480586  might just tickle your rods.   I think all of these will be worth attempting. Clearly; your 10" thinks it's a 20"!  

 

   And check out Arp 148; the "wormhole galaxy"  too.  

 

   -Q4Q

[timokarhula]

One way to grasp the distance to LEDA 1561869 is that it is almost 1000 times more distant than the Andromeda galaxy, and thus one million times fainter than M31!  It's mind-blowing.

 

/Timo Karhula

[quazy4quasars]

One way to grasp the distance to LEDA 1561869 is that it is almost 1000 times more distant than the Andromeda galaxy, and thus one million times fainter than M31!  It's mind-blowing.

 

/Timo Karhula

  Another way to think of this is to consider the relative brightness of LEDA 1561869 vs. M31.

 

  Consider that M31 is mag 3.6 apparent: then, placing M31 at almost One-Thousand times further out will add nearly 15 mags (NED gives the distance modulus of M31 as 24.4 versus a luminosity distance modulus of 39.3 for LEDA 1561869, for M-m =14.9)  giving around V~ 18.5.   The cosmological dimming would be +0.6 mag(NED),  and is already factored in to the luminosity distance modulus.   

 

  Then we consider the spectral scotopic fall-off for z~.16, perhaps half a mag(-37% of SB flux), yielding  +19.0 (apparent scotopic) for M31 viewed at 2 Gyr distance.  Pretty darn faint. 

 

  If we then accept a working scotopic mag 16.0 for LEDA 1561869,  per TImo- we find that galaxy to appear 16 times as bright (-3 mags) as M31 would appear if seen from a 2 Gyr distance.

 

Correspondingly, If we Placed LEDA 1561869 at the distance of M31, it would shine at around mag +0.6,  though that light would be spread across a similarly greater area of sky as well.   Mind blown!   

Edited by quazy4quasars, 08 April 2021 - 02:20 PM.

[timokarhula]

 

Well, magnitude +0.6 is about the total magnitude of the Large Magellanic Cloud.  It is a beautiful specimen in the southern skies.  :-)

 

/Timo Karhula

Edited by timokarhula, 08 April 2021 - 04:32 PM.

[Robin]

Thanks for the observing suggestions!

 

Earlier this week I observed PGC 37477 with my 20" Dobsonian. It seemed to be quite faint considering that its blue magnitude is 15.6 according to Hyperleda. At 256x magnification I saw an elongated and diffuse patch without structure. At averted vision it was visible again and again.

 

Must be a very large galaxy, considering that Hyperleda lists its size to be 1.2' x 0.4' and radial velocity 42832 km/s, which means approximately 1.9 billion light years distance. If it was 19 million light years away, its size would have been 120' x 40'. Wow!

 

Please find attached my sketch.

 

Next time at a dark location I might try some of the further galaxies that you folks mentioned in this thread.

 

Clear skies,

Robin

 

 

 

 

 

Attached Thumbnails

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[Robin]

I searched for magnitudes of some of these galaxies and found the following:

 

blue mag (bmag) from Hyperleda, Vmag ("Visible") from NED, calculated B-V from these, radial velocity from Hyperleda, light-travel time assuming 73 km/s/Mpc Hubble constant:

 

PGC 37477: 15.6 bmag, 13.9 Vmag, 1.7 mag B-V, 42832 km/s, 1.91 billion light years

 

PGC 1561869: 16.9 bmag, 14.6 Vmag, 2.3 mag B-V, 48208 km/s, 2.15 billion light years

 

PGC 2276277: 18.3 bmag, 15.7 Vmag, 2.6 mag B-V, 74087 km/s, 3.31 billion light years

 

Wow that's quasar territory. :-)

 

For many closer galaxies B-V is around 1 mag or slightly less. Is B-V so large in these 3 cases due to large redshift? Or are the NED visual magnitudes too bright?

 

It makes me wonder what the farthest non-quasar galaxy ever observed and documented visually is.

 

 

Clear skies,

Robin

[quazy4quasars]

PGC 2276277  appears core weak and super-spiral.  It's light is dimmed by stretching(cosmological dimming), and the red-shift of a lot of its emission out of the range of our night adapted vision sensitivity.  That B 15.7 is total mag integrated to some isophote and is spread out, ergo real real dim, as DSS B and SDSS g images attest. marginal  AV on a really good night, I'd guess. 

 

The B-V vulues reflect the red-shifting of the broiad optical emmision maximum toward the red, replaced by low and declining flux from blueward.  It is literally as if stars of the galaxy were 1000s k cooler and dimmer.  

 

The furthest strictly non-AGN galaxy that has been observed in 20" class scopes and described here on CN is the monster BClG in Abell 2261, if I remember aright, at z~.22.  

Edited by quazy4quasars, 10 April 2021 - 04:13 PM.