This is NGC 5278, as imaged by the Sloan Digital Sky Survey. This color image was built by putting together broadband ugriz images, with the g filter mostly mapped to the blue channel of the image, r to the green channel, and i to the red channel. (u influenced blue and z influenced red as well.)
This was one of the galaxies in Chloe Wightman’s keystone project at Quest in 2013; she was looking at Galaxy Zoo-identified merging galaxies, and comparing morpological features to optical emission lines.
Holy cow, it’s been a long time since I blogged.
The class I’m teaching right now is 3d Computer Modelling and Animation. Perhaps the hardest thing about it is figuring out if the word Modelling has one or two l’s in it… it depends on whether you’re in the USA or Canada, I think.
For this class, I’m making all of the students do a major project. Some of them are doing some pretty interesting things, and already several of them have figured out things about Blender (the 3D software we’re using, a quite powerful free package that you should check out yourself) that I don’t know myself. A couple are playing around with motion tracking, in order to add 3D rendered elements into a live action video scene. One is building a game using the Blender game engine. Others are doing various other animations.
I’ve decided to take on a project myself. For this project, I am going to model a white dwarf in a mutual orbit with a main sequence or red giant star, pulling matter off of it into an accretion disk. During the animation, the white dwarf will go critical, and explode in a supernova, blowing itself way, and blowing off some of the outer layers of the companion star.
So far, I’ve managed to create the basic progenitor model, and do a little bit of animation of the textures so that the disk is spinning, the star’s surface is roiling, and the gas bridge between the star and the disk looks a little like it’s streaming. Here’s a rendered frame from what I’ve done so far:
I’ll certainly post the full animation once I’ve completed it. Next, I’m going to have to start worrying about how to deal with the supernova. Eventually, I’ll set the whole thing to music.
I just moved from Nashville, TN to Squamish, BC, where I’m starting teaching at Quest University.
Moving is always painful. There’s the administration of it all, of course, and the sadness of leaving friends and community behind. And, there’s all the boxes, the packing, the unpacking. This move is complicated by the fact that we’re moving into a much smaller place (housing costs in Squamish are much higher than in Nashville!). We got rid of a lot of stuff in Nashville, but getting everything unpacked is still turning out to be a bit of a puzzle.
There are some advantages, though. Squamish is in a beautiful location in British Columbia, on the highway between Vancouver and Whistler. There’s this massive cliff face (called “The Chief”) overlooking the town– and a harbour on the other side. We’re in an apartment building, and below is a picture I took at 8:20 PM yesterday from our balcony. It had been a cloudy day, but it wasn’t hazy (as it had been the previous day). Some of the low clouds were hovering below the height of the Chief, which made for quite an impressive sight.
Click to embiggen a bit
NGC 7331 is a spiral galaxy, probably not too dissimilar from our own (except that it lacks a bar), which is relatively nearby. (At a mere 49 million light-years, it’s not in our own back yard, but it’s just down the block.)
Image: Paul Mortfield and Dietmar Kupke/Flynn Haase/NOAO/AURA/NSF
Several years ago, the first time I thought Astronomy 253 (“Galactic Astrophysics”), I had an entire problem set entitled the “NGC 7331 problem set.” In fact, this was a general problem set about the properties and dynamics of spiral galaxies, but I chose NGC 7331 as the example that was referenced in all of the problems.
Before I say the next thing, I want to say that the students in this class were a great bunch of students. One of them the next year would do research with me, and is now in graduate school at Colorado. I really enjoyed teaching this class, and really enjoyed working with that group of students.
So, disclaimers laid, so you don’t read the rest of this the wrong way. I walked into the conference room that the particle physicists on my floor use for meetings and videoconferences; I’ve occasionally used it for the same purposes. That year, sometimes students would work together there. I walk into this room, and what do I see written on the whiteboard?
“I hate NGC 7331.”
NGC 5135 is a barred spiral, similar in some ways to NGC 1365. Both galaxies are members of the IRAS “Bright Galaxy Sample,” meaning that they are very luminous in the infrared as a result of vigorous star-forming activity. Both have very strong bars. Both harbor an active galactic nucleus at their core. (All large galaxies are believed to have a supermassive black hole at their core, but only a small fraction of those black holes are actually being fed; it is the feeding of the black hole that triggers the AGN.) And, both have been observed by Katie Chynoweth and I as part of our (sadly unfunded) project to build maps of the relative Doppler shifts and spectral line intensities of the ionized gas throughout the galaxy.
This image was taken in April 2007 at the CTIO 0.9m, on the same run as the image of ESO 264-G057 that I posted previously.
The image below is an image taken in 1994 with the Hubble Space telescope of galaxy NGC 4526:
Image: NASA, ESA, The Hubble Key Project Team, and The High-Z Supernova Search Team
The bright spot in the lower left is the supernova known as SN1994D. This is a Type~Ia supernova, type type of supernova that has been used by several times (initially two, the one that I was in, and the one that this image is credited to) to measure the expansion history of the Universe, and to discovery that the expansion is accelerating (requiring that there be that which we now call “Dark Energy” filling the Universe). The supernova here occurred in the outskirts of the galaxy— which isn’t particularly surprising for this type of supernova.
The galaxy itself is a dusty disk galaxy. Most disk galaxies have a fair amount of dust in them; you can see the dust in our own galaxy if you look at the sky at the right time of night from a very dark site.
VV114 is a very interesting galaxy. It’s a major merger of at least two big galaxies. If I might go out on a limb, it may even be an advanced merger (on the left) currently strongly interacting with another galaxy (on the right).
The left galaxy is extremely dusty. Sunsets are red because particles in the atmosphere preferentially scatter away the bluer light. Redder light penetrates the dust better. Just before the Sun sets, we’re looking at it through as much atmosphere as we ever see it, so it has to go through the most number of particles in the atmosphere. similarly, very dusty galaxies are red in color. In VV114, this is most striking when you compare the optical light to the infrared light. The left galaxy is nearly invisible in blue light, but is the brighter galaxy in the infrared.
The IR images was taken back in the 1990s, and were part of my first published paper in grad school. The optical image was taken a year or two ago with the CTIO 1.0m telescope. Both images are “false color” — I’ve enhanced the colors to bring out the contrast, and of course no IR image can be “true” color, as it would just look all black to our eyes! However, longer wavelengths have redder colors, so qualitatively the colors are what you would expect.
Are you ready for this? This week’s Friday Galaxy is Mk509:
Admittedly, the image of this galaxy does not rank very high on the “wow, what a cool and pretty looking galaxy” scale. However, this is an interesting galaxy because of what’s going on at the nucleus. Like all large galaxies, there is a supermassive black hole at the core of this galaxy. The black hole in this galaxy is being fed, giving rise to what we call an Active Galactic Nucleus (AGN). If you drop gas down into an accretion disk near a supermassive black hole, a tremendous amount of gravitational potential energy is released. That energy goes into heating up the accretion disk, and the radiation from the accretion disk energies all sorts of other fun behavior in the galaxy.
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:
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.
I apologize for my silence of the last few weeks; real life gets busy at times. This time, I was in a crunch finishing up things before running off to an observing run at the CTIO Observatory in Chile. That’s where I am right now. I’m at the 0.9 meter telescope doing imaging of “blazars,” a class of active galactic nuclei that sometimes vary on timescale of minutes (which is surprising if you know how big galaxies are). My graduate student Katie Chynoweth is observing on the 1.5 meter telescope, doing spectroscopy of infrared-luminous galaxies.
Below is an image — really, a composite of 27 images taken over the course of about 2 hours through red, green, and blue filters — i took with the 0.9m telescope:
The target I’m interested in is the galaxy that’s right at the center:
This galaxy goes by the romantic name ESO 264-G057, and is in fact one of the infrared luminous galaxies that is a part of Katie’s project. She’s been observing that galaxy and one other (whose picture will probably show up here in a day or two!) this week, and I took this image in support of that project.
So this is an image of the galaxy that’s only two days old! Well, plus the 230 million years it took the light to reach Earth….