Object of The Week August 9 2020- I ZW 136 and A Big Telescope

[Jimi Lowrey]

I Zw 136 —Leda 3087279 and Leda 2387685

Type— Galaxy Pair

Hercules

RA 16 13 31
DEC + 51 03 39

Mag A 15.7 V
Mag B 15.4 V

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I observed this small cosmic crash last May and after my observation of it I was doing research on it and when I view the SDSS image of I ZW 136 I was surprised by the color of the pair in the Sloan image. The galaxy on the right I will call A (LEDA 3087279)and the galaxy on the left I will call B (LEDA 2387685) . The A galaxy was really blue and the galaxy on the left B was red looking. Over the years I have viewed hundreds of SDSS images and most or the time if you have an interacting galaxy pair at the same redshift they are the same color. I then looked at the redshift of the pair and B was at Z = .0334 and A had a bad redshift and was not to be trusted. Now I thought that because of the different color of the two galaxies that they were not interacting and one was foreground and the other was way behind thus the different color.

SDSS 3975image

So now I had to prove my assumption. I sent a note to my friend up the road at McDonald Observatory who is a resident astronomer and ask if we could get a spectrum of the A galaxy to get its redshift and prove my assumption. To my surprise he said that they were doing work on the 10.2 Meter HET telescope and were not doing science that night and could get my spectrum that night. What Luck!!

HET Telescope
3976

So on the last night of May I got my Spectrum of I ZW136 A. It takes a while to reduce and analyze the data. I have been waiting for the results.

Hubble image pushed of I ZW 136
3977

Yesterday in my in box I got the spectrum of I Zw 136. The redshift of the A galaxy is Z= .0334 that is the same as the B galaxy. So my theory of a discordant redshift of the two galaxies was completely WRONG! Oh well this often happens in science but as often happens when you answer one question it raises another.
My professional astronomer friends now want to know why the A galaxy is so blue. So Stand by for more from this unusual cosmic crash.

I observed I Zw 136 again last night and at 610X it was small and you could see the irregular shapes of A and B. Both galaxies look to be of equal brightness.

Give it a Go!

[Steve Gottlieb]

I've observed this pair (separation just 20") a couple of times in my 24-inch including last year's Golden State Star Party (GSSP). At 375x both galaxies appeared very faint and small, no more than 10" diameter, and were cleanly resolved. Individually, they're pretty dim -- V = 15.4 (LEDA 2387685) and V = 15.7 (LEDA 3087279).

The blue galaxy (LEDA 3087279) is classified as an "E+A" type. These galaxies (https://arxiv.org/pdf/astro-ph/0402062.pdf) display both a young stellar population (similar to A-type stars) and an old population (characterized by K-type stars). So, they resemble an elliptical with a young population. The spectrum exhibits strong Balmer absorption lines and no emission in [O II] or H-alpha. The phenomenon seems to occur mainly in interactions or mergers like I Zw 136.

The current model is a former starburst galaxy (within the past billion years) that suddenly terminated its activity (depleted its reservoir of gas?).

[Frank Richardsen]

What a nice and interesting object! At the end of the last week I was out for two nights with Uwe at our favorite place Edelweissspitze in the Austrian alps.
Amongst other things I observe I Zw 136 and the area around in my 36 inch.
LEDA 2387685 appears as dim as LEDA 3087279 20’ away and both galaxies shows their “ears” (irregular characteristics of interaction) on the opposite sides. The red and blue color on long exposured photos makes no significant difference in visual contemplation. Just a ‘few more minutes away” appear the elongated and slightly fainter E-Type Galaxy LEDA 3132495. In the same field of view appear the faint and elongated LEDA3132519. I observed the group with V=738x and 940x

[Jimi Lowrey]

Hi Frank glad you tried I ZW 136. Wish I could have been with you and Uwe at he Edelweisspitzer it is a special place.

I Zw 136 is a most interesting interacting pair. I look forward to understanding it better from the professional astronomers who are researching it. Send all my best to all of Connie and my friends in Germany.

[Uwe Glahn]

Like Frank just mentioned I also tried the Zwicky pair with my 27-inch. I noted:

already separated with the searching eyepiece, with higher power direct vision objects, somewhat diffuse with indicated ears opposite of both cores, third fainter galaxy to the NE