Two interacting galaxies

Here are images of two more galaxies. These weren't taken during the current run, but in a previous run. Last November, I was also down at CTIO with some students. I was doing blazar work on the 1.0m telescope (not to be confused with the 0.9m telescope I'm using right now), and shot off some images of the galaxies that Katie was observing spectroscopically. The two galaxies below are those galaxies.

The first is NGC 1614:


This galaxy has what we in the biz call a "disturbed morphology." It's not just a clean spiral galaxy, and it's certainly not an elliptical galaxy. Sticking off down and to the left (to the southwest— yes, i got that right) is a big ol' tidal tail, the smoking gun that tells me that this galaxy is in fact an interacting galaxy. Indeed, this is a major interaction that is well on its way to being a major merger.

The second galaxy, also imaged last November, is ESO 420-G013:


When I show these color images, there has already been some handwaving. I've done a nonlinear conversion of the flux measured into a brightness, and have chosen that conversion in each of the red, green, and blue channels primarily for artistic purposes. In this case, though, in order to highlight the features of interest, I used the Gimp to further process the image to make two additional versions:

i-001ad0388e36681297859ae2677a9a1b-eso420-g013-lowlevel.png i-60b049ab1da189cf59dc6f5b1679a04a-eso420-g013-sat.png

In the image on the left, I cranked up the nonlinearity to bring out the low-level features. Notice the ringing or banding structure? The galaxy seems to have a "terraced" light distribution. That's another thing that tells me that this galaxy is in fact likely to be an advanced merger of two other galaxies.

On the right, I've cranked up the saturation to enhance the color contrast. There are a number of things to notice here, but the one I want to highlight is right at the nucleus. Notice how the nucleus is a bright red spot, and the brightest spot in blue light is acutally offset to the southwest (down and to the right)? What's going on here is that there is a lot of dust and gas right at the nucleus. Dust blocks light, but it lets through more redder light than bluer light. This is why the sky is always so red right at sunset. Because there's so much dust right at the nucleus of this galaxy, it shows up a lot redder than the other parts around it.

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Neat! Can you offer links to larger images? Much appreciate the little lesson in how to usefully manipulate images to bring out different details.

By Hank Roberts (not verified) on 16 Apr 2007 #permalink

The tidal tail in N1614 looks like it is down and to the right, which would be SW in canonically oriented images.

Yes. That's what I said :)