Skip to main content

Katheryn's Wheel and colliding galaxies

The first thing that you should note about this work (available here) is that it has almost been a decade in the making. The peculiar object, named Katheryn's Wheel, was first discovered in 2005/6 and the authors have been performing follow up observations and digging up archival data on the object ever since. After first being discovered in the optical region, the authors dug up Near Infrared, Mid Infrared, Far Infrared and Radio observations. The authors also pursued follow up spectroscopic observations of specific regions of the object.

I think I should take a step back to give you a look at the bigger picture. Every once in a while, we see galaxies interacting. I'm sure you've heard by now that our own Milky way galaxy and Andromeda are on a path to collide sometime over the next billion years and will end up being one big mess of stars and gas. Similarly, in the past, a lot of galaxies have interacted with our Milky way galaxy. And if we look out into space, we will see many such examples of galaxies interacting. The reason this object is of peculiar interest is because of the spatial morphology of the interaction. Galaxy collisions rarely produce rings (rings where star are forming), because there are constraints on the initial interaction for the end product to be a ring of star formation. Collisional rings are also interesting because the star formation in the ring is manifested because it can help in understanding the density/shock wave that initiated star formation in the ring like structure.

Below is one of the images from the paper. If you neglect the bright star in the south of the picture, you will be able to see a galaxy roughly in the middle of the picture and a circle/oval shape surrounding the central galaxy. There is also a second bright object north west of the central galaxy/ring. The authors speculate that the larger galaxy at the center was disrupted by the smaller galaxy in the top left corner. The orange/red color indicates emission from newly forming stars and you can therefore notice that the central galaxy has almost no orange/red color, meaning that the star formation in the central galaxy was quenched by the collision. This doesn't appear to be the case with the smaller galaxy in the top right corner.

For more pretty pictures or a better understanding of exactly what's happening in this picture, read the paper. The authors are thorough in understanding the star formation rate, the abundances of higher elements and in estimating the time scale of interaction and so on.

Popular posts from this blog

Animation using GNUPlot

Animation using GNUPlotI've been trying to create an animation depicting a quasar spectrum moving across the 5 SDSS pass bands with respect to redshift. It is important to visualise what emission lines are moving in and out of bands to be able to understand the color-redshift plots and the changes in it.
I've tried doing this using the animate function in matplotlib, python but i wasn't able to make it work - meaning i worked on it for a couple of days and then i gave up, not having found solutions for my problems on the internet.
And then i came across this site, where the gunn-peterson trough and the lyman alpha forest have been depicted - in a beautiful manner. And this got me interested in using js and d3 to do the animations and make it dynamic - using sliders etc.
In the meanwhile, i thought i'd look up and see if there was a way to create animations in gnuplot and whoopdedoo, what do i find but nirvana!

In the image, you see 5 static curves and one dynam…

on MOOCs.

For those of you who don't know, MOOC stands for Massively Open Online Course.

The internet is an awesome thing. It's making education free for all. Well, mostly free. But it's surprising at the width and depth of courses being offered online. And it looks like they are also having an impact on students, especially those from universities that are not top ranked. Students in all parts of the world can now get a first class education experience, thanks to courses offered by Stanford, MIT, Caltech, etc.

I'm talking about MOOCs because one of my new year resolutions is to take online courses, atleast 2 per semester (6 months). And I've chosen the following two courses on edX - Analyzing Big Data with Microsoft R Server and Data Science Essentials for now. I looked at courses on Coursera but I couldn't find any which was worthy and free. There are a lot more MOOC providers out there but let's start here. And I feel like the two courses are relevant to where I …

Pandas download statistics, PyPI and Google BigQuery - Daily downloads and downloads by latest version

Inspired by this blog post :, I wanted to play around with Google BigQuery myself. And the blog post is pretty awesome because it has sample queries. I mix and matched the examples mentioned on the blog post, intent on answering two questions - 
1. How many people download the Pandas library on a daily basis? Actually, if you think about it, it's more of a question of how many times was the pandas library downloaded in a single day, because the same person could've downloaded multiple times. Or a bot could've.
This was just a fun first query/question.
2. What is the adoption rate of different versions of the Pandas library? You might have come across similar graphs which show the adoption rate of various versions of Windows.
Answering this question is actually important because the developers should have an idea of what the most popular versions are, see whether or not users are adopting new features/changes they provide…