Showing posts from 2015

Pocket reading stats

Using the same Python code I used to look at my bookmarks, I looked at my reading habits using Pocket and here are the results.

I installed the app in 2014 and therefore, the number of articles I read in 2014 are fewer in number than those I read in 2015. The 2015 numbers should probably be my benchmark from this point on.
These are monthly reading habits. Apparently, I didn't read as much in Feb and March as I did in the following months. Well, I dug myself deep into two of my courses, General Relativity and Ultrafast lasers at that time, which could be the reason. And I might have read less in September/October than in August or November because I was apping those months. Maybe.

Now we come to days of the month. I can't write anything meaningful about this. It'll be better if I get weekly behavior i.e Monday through Sunday and, if I'm correct, see that I read a lot more on Friday/Saturday/Sunday than on the other days of the week.

And we finally come to hourly habit…

Arxiv author affiliations - Part II

Well, one part of the project is complete now that I have lists of affiliations of co-authors on a number of papers. I now need to convert this into an edge-weighted graph, where the edge weights convey how connected various universities are in terms of co-authorship. Previously, I had mentioned that I had information on all of the author affiliation but that I needed to sort them based on individual papers. As small tweak in the code was all that was needed to get that information. Following is the necessary code.
import urllib
from BeautifulSoup import BeautifulStoneSoupurl = ''
data = urllib.urlopen(url).read()
soup = BeautifulStoneSoup(data)

test = [tag for tag in soup.findAll('entry')]affiliationList = []
for i in range(len(test)):
        if test[i].findAll('arxiv:affiliation') != []:
                affiliationList.append([tag.string for tag in test[i].findAll('arxiv:af…

Arxiv author affiliations using Python

So, I wanted to get author affiliation information from papers on arXiv. arXiv provides with an API to bulk query their database and get information. Following that, I look for the attribute 'arxiv:affiliation' in the html data. Here's the code -

import urllibfrom BeautifulSoup import BeautifulStoneSoupurl = ''data = urllib.urlopen(url).read()soup = BeautifulStoneSoup(data)
#list = soup.findAll('arxiv:affiliation')#for i in range(len(list)):#        print list[i].contentstest = [tag.string for tag in soup.findAll('arxiv:aiffiliation')]
Now, the problem I'm having is that I'm getting affiliation of all authors which I want to split into sets of affiliations of authors of a paper, which I'm stuck on at the moment. Once I get that part, I can move on to the next part of this pet project, displaying these relations between the unive…

Looking at my bookmarking habits

So, I have finally been able to get the time stamps out of the html file into which I had exported my bookmarks. But preliminary analysis doesn't make much sense. So, I used the BeautifulSoup and time python library to extract and make sense of the time stamps. So, chrome stores the time stamps in this format - '1402120115'. You can look at this if you want to understand the time stamps.
Now here are the weird parts
1. It thinks that all of the bookmarks were made in 2014
2. It thinks that all of the bookmarks were made in the 6th month i.e June.
3. It doesn't show any bookmarks on the 1-6 days of the month
4. The hour stamps are GMT and not GMT +0530 which is Indian Standard Time.

The html file is available in blog and here's the code -

import numpyimport matplotlib.pyplot as pltimport BeautifulSoup
import time
soup = BeautifulSoup.BeautifulSoup(open('bookmarks.html'))
allAttrs = [tag.attrs for tag in soup.findAll('a')]
dates = []for string in allAttrs…

PhD advertisements in Astronomy

I have been hunting for open PhD position, mostly in Europe, over the last 4 months and I have had to follow about 4 websites, for the most part, constantly to check for new positions/advertisements. And while there were a few websites where people curated lists of places in the world or in the US where students can pursue graduate studies in Astronomy & Astrophysics, either the lists were outdated or the hyperlinks were broken. So I'm going to take a shot at it myself and curate a list of places to pursue graduate studies in A&A. You can follow this page for updates.

This week's Pocket reading list : Week 2 of Nov.

Rocket men : Human breath can be used to diagnose patients for certain illness. While people have tried developing instruments that can analyze our breath to look for symptoms, it's a very hard problem to crack given the low concentrations of molecules involved. Cue three rocket scientists - one who had worked on lasers, one who had worked on photonics and analyzing molecular spectral data and the third who had worked on gas flow. They developed a portable machine which can accurately detect Ammonia in human breath, thereby helping diagnose patients.

The Two Cultures of Computing : There are two kinds of people that I know of - the first kind who quarrel about which the best text editor is (VIM FTW) and the second kind who look at us and wonder why we're quarreling over which the best text editor is. This is such an account. More elaborate. More examples.

Everything You've Heard About Chastity Belts Is a Lie : For those who don't know what it is, a Chastity Belt is somet…

This week's pocket reading list : Week 1 of Nov

The WWII-Era Plane Giving the F-35 a Run for Its Money : It's interesting the hear that while technology has been making war more and more sophisticated, there have been people who are keen on using less-technologically advanced machines. This is the specific case where an older (turbo-propeller driven) plane is being preferred for ground support, instead of the more technologically advanced flying machines, as they are better at it than the rest.

How Politics Shaped General Relativity - It's almost been a 100 years since Einstein proposed the General Theory of Relativity, which gave rise to cosmology and helped us understand the universe as a whole. It's interesting to read about how the political ideologies of the time (WWI-WWII) contributed to adoption or dismissal of the theory in various parts of the world.

The things feminism has improved for me: A male perspective : A very interesting article that elaborates on the underlying principle - "Knowledge is Power"…

Isolated galaxies and AMIGA

Galaxy evolution is a tug of war between the nature of the galaxy (morphology, mass, etc) and nurturing environment of the galaxy (major or minor mergers, ram stripping, etc) and to understand it, we need to understand when nature rules over nurture or otherwise. An interesting way to resolve this question is to study isolated galaxies - isolated in the sense that there are hardly any galaxies in their vicinity. The qualitative 'hardly any' was quantified to create the Catalog of Isolated Galaxies (in 1973) and then revised by the AMIGA people for a more up-to-date study. Understanding the evolution of isolated galaxies inherently tells us more about the role that the nature of the galaxy plays in it's evolution.

Today, I was reading up on some interesting papers by the AMIGA people, all three on the HI (neutral Hydrogen) profiles of select isolated galaxies. The three papers can be found here, here and here. I came across this survey recently and only today, as I was rev…

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 …

First science from New Horizons of Pluto

The first official scientific publication from the data New Horizons has sent back to us got published last week and it's open access, available here. In my opinion, it's fairly accessible to the layman or one who's familiar with the basics of geology and basic science.

Broadly speaking, the paper talks about their observations of Pluto and it's three moons Charon, Hydra and Nix. Towards the end of the paper, they also talk about upper limits on size of possibly undiscovered moons and the the properties of a ring system, if any is present while still undetected. Going into the details, they talk about the changes in albedo (reflectivity of a surface) on Pluto's and Charon's surfaces and what the reasons might be. There are also numerous surface features, from ridges to valleys, from craters to mountains, from glaciers to possible sublimation pits. The paper discusses these diverse geological features and their possible origins. The paper also talks about the a…

Sifting through photographs : The comet 17P/Holmes' orbit from images on the WWW

I watched this video a long long time ago, where Dr. David W. Hogg using images publicly available on the internet to do science. Case in point is this paper they published where they tried understanding the trajectory of the comet 17P/Holmes from astrophotographers' images online. They searched for images of the comet, after it brightened and public interest in it had gone up. They then tagged the images to know what part of the sky they were looking at using They then did some math, which I will hopefully understand one day, to weigh different images depending on their authenticity and how their metadata of when the images were taken was compared with their predictions of when the comet was in the field of view of the picture. One day. They were, in fact, finally able to reconstruct the orbit of the comet, albeit a slight error.

The video mentioned above gives more examples of such, including one awesome example where they rediscover stellar tidal streams observ…

FIGGS : The Faint Irregular Galaxy GMRT Survey

For those who don't know, GMRT stands for the Gaint Meter-wave Radio Telescope. Meter because it observed radiation with wavelength of about a meter or about 300 MHz. Ohkay, with that out of the way, let's talk about the actual paper.

If you have been following my blog posts, you will understand why studying faint, irregular, dwarf galaxies is important. Faint dwarf galaxies have very low mass and understanding them will help us understand galaxy formation and evolution in the low mass case. Another interesting thing I learnt from the paper, that should've been obvious to me earlier, is that the gravitational force keeping the (gas in the) galaxy together is about the same as that produced by a few supernovae. The reason they are irregular makes sense now because once these galaxies start forming their first stars, which then go on to explode, the galaxy's gas gets pushed out by the explosions. Also interesting is figure 12 from the paper, that tells us that most of t…

Decadal vision document, Astronomy & Astrophysics - Indian Academy of Sciences & Astronomical Society of India

Decadal reports are used as a sort of a road map, a review of the current trends in the field, of what the field is moving towards in the next decade and recommendations put forth which can be used by the governing bodies to dispatch funds appropriately. I have come across decadal reports by the American Astronomical Society (AAS) and by the Astronomical Society of Australia (ASA) but only now have I come across one by the Astronomical Society of India (ASI)
Decadal vision document : Astronomy & Astrophysics (PDF file, 27 MB)
I skipped right to the recommendations part and I had my mind blown. Let me give you a brief summary of the recommendations put forth by the committee.
1. Bringing together the community to consolidate work and form Autonomous Working Groups spanning the astronomical research being carried out. The groups can bring together astronomers working on theory, observations and simulations to give a holistic picture. Working groups also help foster younger talent an…

This week's pocket reading list : Week 2 of Oct

Chinese scientists row over long-sought protein that senses magnetism : If you don't know already, all(?) birds and some animals can sense magnetic fields. Birds use the Earth's magnetic field to be able to migrate long distances. This article is about the story of how one researcher discovered the exact protein that the animal body uses to detect magnetic fields and how another researcher from a neighboring institution apparently broke an agreement between the two to wait for the first one to publish. Collaborations are commonplace in academia, more so now than ever before, and the legal ramifications of such collaborations where a large amount of money (and of course pride) is (are) involved are still in murky waters.

Curiosity wheel damage: The problem and solutions : I hope you know that NASA put a new (yes, there have been ones before it) rover on Mars called Curiosity and it's been there for over an year now if I'm correct. If you know about Curiosity, you probabl…

New born stars and the State-of-the-art.

If large cameras and telescope capable of probing the low surface brightness objects in the sky is one end of the state-of-the-art in astronomy, the following work would be the state-of-the-art at the other end of the spectrum. While surveys focusing on looking at all of the objects in the sky, choosing speed and number of astronomical objects found over spatial resolution, there are telescopes used specifically to study objects at the highest spatial resolution.

The paper (found here) talks about a narrow, edge-on disk resolved around the star HD 106906 using the SPHERE instrument on the VLT telescope. Note that I used to word resolved and not detected. For an astronomer, those two words are vastly different. The same way dark matter is discovered but not yet observed, astronomers knew that the aforementioned star had a dusty disk around it. How you ask? Well, for starters, if you have dust in front of a light source, the light source looks dimmer. Secondly, whatever light that the …

Maarten Schmidt and Jayant V. Narlikar : An Astronomer's life.

Well, I guess, if I'm being pedantic, Dr. Jayant V. Narlikar is more of a cosmologist and Dr. Maarten Schmidt is the astronomer, I guess. Moving that aside, they are two heavy weights in their respective professions and we younguns have a lot to learn from them.

I came across this autobiography (of sorts) of Dr. Maarten Schmidt wrote for the Astronomy & Astrophysics Annual Reviews journal, It's a beautiful account of his professional life as an astronomers, where all he traveled for the job and a historical perspective on what many astronomical concepts we now consider to be set in stone.

While I read the earlier article a long time back, I am only now coming around to post it here because I read this other biography [1] of Dr. Jayant V. Narlikar and his work by one of his colleagues Dr. Naresh Dadhich. You probably know Dr. Narlikar as one of those scientists who came up with the steady state theory of the universe, you know that theory that competed with the Hot big ban…

The TMT, India and the Indian astronomical community.

I am crazy about the Sloan Digital Sky Survey (SDSS). I worked on data from the SDSS for my first summer project. I learnt about SQLquery to acquire data from the SDSS's servers and I learnt Python to do the relevant data analysis. It's an unbelievable treasure trove of data and is in my opinion, the best place to start off if one is serious in pursuing a career in astronomy. Having said that, a while back I was looking at the various institutional members of the SDSS and I found out that there were NO Indian institution involved with the project. None whatsoever. Now, don't get me wrong, I'm sure that there were Indians involved in the project. I'm saying that there was no institutional support meaning that Indian universities weren't funding the project or actively building instruments for the project or had priority access to the data. And it kind of made me sad.

The good news now is the fact that India is a 10% partner in the Thirty Meter Telescope (TMT), …

Ohh my! 158 new dwarf galaxies discovered using the DECam!

Well, for starters, the DECam is the Camera on the 4-metre Blanco telescope at the CTIO (Cerro-Tololo Inter-american Observatory). It was originally designed for the DES (Dark Energy Survey) but I guess it's also being used for other astronomical observations. The authors are part of the NGFS (Next Generation Fornax Survey) efforts at the CTIO.

Coming to the paper (found here), the authors give a preliminary report of the 158 new dwarf galaxies they've discovered in the Fornax cluster central regions. There is a lot more science to come out of the data but a preliminary analysis shows that the dwarf galaxies seem to be clustered within the Fornax cluster core, clustering previous predicted in simulations. The authors also fit the surface brightness distribution for each of the dwarf galaxies found to estimate their effective radii. The dwarfs found seem to be fainter and smaller than similar ones (referred to as Ultra Diffuse Galaxies - UDGs) found in the Virgo cluster and th…

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 distribut…

Dwarf galaxies and all-sky HI surveys FTW \m/

I've been coming across a lot of work, in the optical and the radio domain to identify and understand dwarf/satellite galaxies, stellar tidal streams and neutral HI (HI is neutral Hydrogen and HII is singly ionized hydrogen i.e a proton) in the universe. This is one of many such efforts (a few of which I will write about later on) where the authors used the SKA pathfinder telescope BETA/ASKAP to observe the galaxy group IC 1459. The full paper can be found here.

Let me first tell you why it's a challenge to observe neutral HI in the local universe and why these results are so interesting, IMO. All galaxies form from HI (again, neutral Hydrogen) but once the galaxy/stars start(s) forming, neutral HI close to the sources of radiation get ionized into HII. Only HI in the outer reaches of the galaxy is left unionized. And given that it's at the edge of the galaxy, it's not nearly dense enough to emit strongly. Don't get me wrong, there is still a good amount of HI in-…

Why did I not know that there was a UV telescope on the MOON!!!

Well, I got to know a couple of days back that there was a Lunar-based Ultraviolet telescope. I finally got to read the paper today (that can be found here) and it's quite interesting. For those of you who remember, the Chinese landed a Lander on the moon and tried sending a rover on the lunar surface (which quickly failed). Apparently, that Lander had a UV telescope on it.

As soon as I read the abstract, the first questions that came to my mind was when exactly they observe. If you think about it, we see the moon at night because it reflects the sun's light meaning that if it's night time for us, it is day time on the moon. The same way, if I were on the moon, I'd be able to see the earth because it will reflect the sun's light. Astronomers on earth prefer moonless nights because the night skies are darker. In the same way, the lunar based telescope had to take into account the fact that earth shines bright at night time when designing their telescope and plannin…

Ultra-Compact Dwarfs and stellar streams : astrophysics @arXiv

Title : NGC 3628-UCD1 : A possible omega centauri analog embedded in a stellar stream.

Let me give you a bit of an introduction in the first place. Stellar streams are streams of stars around a central galaxy, streams assumed to be filled with left over stars from a galaxy merger between a minor galaxy and said central galaxy. In this case, NGC 3628 is the central galaxy and the newly discovered UCD1 is proposed to be a remnant of such a merger-interaction. Also, FYI UCDs stands for Ultra-Compact Dwarfs.

Moving on, as the authors mention in the second section, they were observing the galaxy NGC 3628 and it's associated stellar stream in 2009 when they discovered a bigger object/clump seemingly embedded in the stellar stream. They finally got around to observing the clump in 2014 (what i'm going to take away from this is the fact that there aren't enough grad students to reduce/analyze all the data being acquired so yeah, maybe I'll find a grad position somewhere! :D).

#FaveAstroPlot : Binary pulsars and general relativity

Another interesting astronomical plot is one that ended up providing an indirect evidence of a prediction of general relativity, gravitational waves. General relativity, proposed by Albert Einstein, predicts that gravitational masses can radiate energy in the form of gravitational waves but in reality, these waves are so weak (because gravity itself is weakly interacting) that it is hard to detect them directly. There are experiments to detect them directly (eg : LIGO and LISA) and indirectly (Pulsar Timing Array) but it was indirectly proved by Hulse & Taylor in 1974 when they discovered a double pulsar PSR 1913+16. This peculiar double pulsar had the interesting property that it's period was decaying, instead of remaining constant. As you can see from this plot on twitter, the horizontal line is what is expected if we assume that there is zero orbital decay and the data points are observed time periods over the course of a couple of decades. What's happening behind the …

Pocket reading list : Week 2, Sep

The Homeless Scientist Who Tried to Prove Selflessness Doesn't Exist - Dr. Price came up with an equation that quantified altruism, or it seemed like it for the most part. He developed a mathematical framework to understand the selfless behavior of various animals. This is the tale of what happened after.

The End of Gangs - A beautiful article about the gangs in Los Angeles, how they came to rule the streets there and how law enforcement finally figured out how to clean the streets and make neighborhoods safe again. I kept getting reminded of the TV show 'The Wire' as I was reading this, how empty lots becomes a cesspool for addicts, how streets are rules by gangs and the violence between gangs. It's also a story of how policing isn't just about beating the perpetrator with the other end of the stick but about community relations and foot work.

The Sign Language Interpreter of the Rappers - I was surprised to hear that deaf people went to concerts in the first place!…

#FaveAstroPlot : Pulsars

Here's a tweet showing the radio pulses observed from a pulsar, in fact the first radio pulsar discovered by Jocelyn Bell Burnell, for which her thesis adviser got a Nobel prize (which he didn't share with her but that's a whole different story). There's also a fairly interesting story behind the image itself that can be found here.

Firstly, put yourself in a time and age when radio astronomy was still nascent and people were just scratching the surface of various radio sources. Also, this wasn't the era of milli-arcsecond resolution radio astronomy but it was the era of single dish-arcminute resolution astronomy. Radio astronomers used to perform lunar occultations to reduce the uncertainty of an astronomical object's position. Secondly, this was before digital devices were ubiquitous for recording and displaying the radio signals. There were analog chart recorders which used to plot the total strength of the radio signal that the telescope receives on ginormo…

#FaveAstroPlot : Exoplanet transits

I won't be as verbose this time but it's still something that I find just as interesting. The in thing about astronomy at the moment is exoplanets. Everyone talks about them, everyone wants to know if there's another planet out there like earth and EVERYONE wants to know if there is alien life somewhere else in this universe. What I find more interesting is the science behind how exoplanets are found and characterized.

This is a tweet by Phil Plait of Bad Astronomy fame (if you don't already follow him on twitter, you definitely should!). It is a plot of intensity or brightness of a central star as a function of time. As mentioned on the x-axis, over the course of ~4 hours, the brightness of a star fell to 0.985 times it's prior brightness and then went back to normal. This dip in brightness is because this star is being eclipsed by a planet that is revolving around it (and luckily, in the plane of sight!). Astronomers were able to distinguish this drop of intensit…

#FaveAstroPlot : The HR diagram of brown dwarfs

An awesome thing happened over the weekend. To give you a bit of a backstory, I went a crazy over the last week and started following a bunch of Professors and grad students who pursue astronomy, all around the world. And over the weekend, someone started the hashtag #FaveAstroPlot and tweets started pouring in! There are probably a lot of curated lists of tweets and this is one such is by Emily Lakdawalla.

Now, I thought that it'll be interesting to take up a couple of those plots and write follow up articles detailing what exactly what the plots are about and why they are important/relevant. I also want to get back on the horse and start adding more things to my astro_data_projects repository on Github.

For this week, let's look at the HR diagram of brown dwarfs here. One can find the relevant data here which Trent Dupuy has kindly made available publicly (This is one thing I love about astronomy, most of the data is in the public domain!).

For the uninitiated, let me tell …

This week's reading list

Best Practices for Scientific Computing : Everyone needs to get their hansd dirty and write programs in this digital age of ours. It'd probably be for the best too, literacy could soon come to include the ability to program, in any language of choice. And the same way spoken languages are standardised such that no matter where you go, you can speak and understand the other person (for example in English.). Similarly, a lot of us will have to read other people's programs from time to time and from what i've experienced, it's one of the hardest things to do. A must read for any student or scientist to who are learning programming such that they can cultivate these rules into their workflow to produce not only working programs but readable and extendable programs.

Learning to Speak Lingerie : At some point or the other, we've all come across that shop run by an immigrant, one who might not even speak the same language as ours or maybe he can barely speak enough to keep…

Why do birds move their heads back and forth while walking?

Like I've mentioned a couple of times earlier, there are amazing things around us, wonderful science to learn from, if only we cared enough to ask the right questions. This was one such question I asked recently. There are a good number of birds here at IITM so a while back, I was looking at them as they were walking on the ground. And while they were walking, all of them were moving their head back and forth. Well, at least at the time it looked like that, as though they were moving their head with every other step they took on the ground. I asked friends of mine who were around at the time why they thought birds did so and they guessed that balancing themselves had something to do with it. I asked an ecologist friend of mine if she knew the answer and when she didn't know the answer, I gave up looking for the answer.

I noticed this again yesterday and I realized that I could've asked the internet the same question. So I did. Apparently, I was looking at it wrong apparen…

Pocket reading list : Part 7

Albert Woodfox’s Forty Years in Solitary Confinement : I don't know if there's such a thing as solitary confinement in Indian prisons but the idea sounds kind of absurd. I've read a couple of other articles on the short term and long term effects of long term isolation, isolation not just from human company but isolation from pretty much everything on Earth other than food, water or air. This is the absurd story of how one man has been confined in solitary confinement and his attempts to repeal the state's decision and get out of jail have all been in vain. This article goes brilliantly with another one that talks about how much power parole boards yield in the USA.

Mapping how the United States generates its electricity : I love beautiful visualizations and there are a couple of news outlets that make good ones. This is one of those. If you're looking for more, Upshot by the NYT might be a good place to start.

New Laws Explain Why Fast-Growing Networks Break : Human…