Skip to main content

HI Rogues

As I follow the endless path, looking for references in papers, I came across this - the HI rogues gallery. It is a "Collection of maps of HI in Weird Galaxies and Weird HI in otherwise Normal Galaxies" and wow is it a beautiful collection.

The whole reason astronomers are interested in HI (neutral Hydrogen) in the universe is because it is the fundamental fuel that makes stars. Also, there's loads and loads of it in galaxies and in the Inter-galactic medium (theoretically).  And in galaxies, this HI extends wayy beyond the boundary defined by the stellar population of the galaxy. This fact can be used to understand the (baryonic) gravitational potential of the galaxy it is embedded in, and the dark matter halo it is embedded in. If you dig through the gallery, you will come across interesting examples showing intergalactic debris with no optical counterparts! This is interesting as it helps us understand the history of the galaxies, their environments and the distribution of dark matter cusps in the galactic environment.

Now I'm reminded of how I came across this gallery. I was reading through the paper by Kilborn et al. 2006 on Gaseous Tidal Debris found in the NGC 3783 group. They used the ASKAP to study the galaxy group surrounding NGC 3783 and used the ACTA to do a follow up survey on objects whose ASKAP observations clashed with those from legacy Parkes radio telescope data. They discovered new radio counterparts to optical galaxies in literature and they discovered a new HI cloud without any optical counterpart. They expect the cloud to have been part of another galaxy closeby, one that looks to have been disrupted tidally (with significant evidence).

A rough idea for a PhD project has started forming in my head. I am currently applying to a professor who wants to work on simulating the neutral HI in the universe and understand how galaxy evolution works : through feedback and given an environment. And apart from simulations, there are more and more interesting observations, in the optical and the radio domain, where people are discovering lower and lower mass galaxies. A thorough study of dwarf/satellite galaxies, stellar tidal streams, intergalactic HI clouds and HI in tidally interacting galaxies is going to become accessible over the next decade, with the upcoming ASKAP/Apertif(WSRT) in the radio domain and the LSST/GMT/TMT in the optical domain. It is going to be rich in observations and it looks like something I'm interested in working on for the next decade or so. Now to see if I find a prof who is as interested in working on it as I am...

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 …

On programmers.

I just watched this brilliant keynote today. It's a commentary on Programmers and the software development industry/ecosystem as a whole.



I am not going to give you a tl;dr version of the talk because it is a talk that I believe everyone should watch, that everyone should learn from. Instead, I am going to give my own parallel-ish views on programmers and programming.
As pointed out in the talk, there are mythical creatures in the software development industry who are revered as gods. Guido Van Rossum, the creator of Python, was given the title Benevolent Dictator For Life (BDFL). People flock around the creators of popular languages or libraries. They are god-like to most programmers and are treated like gods. By which, I mean to say, we assume they don't have flaws. That they are infallible. That they are perfect.
And alongside this belief in the infallibility of these Gods, we believe that they were born programmers. That programming is something that people are born wit…