After a long (and needed summer break) I have come back to the internship this week and was very excited to jump straight back in. While most of the fantastic people that I shared my first four weeks with have unfortunately finished their internship, I have got a lot done this week.
This week was extremely outreach heavy, but with some interesting variety as well. I started off the week continuing the work that Heather had started, working on the masterclasses for secondary school students that you can find here. Specifically I have been working on the ‘Mapping the Universe’ masterclass. In this masterclass I attempt to teach students how to use TOPCAT (a software often used to work with astrophysical catalogues and graphing of large amounts of astrophysical objects) whilst mapping over 3700 distant galaxies from the COSMOS field (see figure 1) and linking them to real images of the galaxies from SUBARU and Hubble Telescopes.
Figure 1: the style of graph created on TOPCAT in the Mapping the Universe masterclass
Linked to these masterclasses, I also worked on an article for STEM magazines in order to promote the classes and have them reach more schools and more students that could be interested in learning about what the university does and what astrophysicists do. Finally, I have been working on some video promoting the La Palma trip that David Sobral does for second to fourth year students to go observing at the Roque de los Muchachos Observatory.
Next week I will hopefully put the finishing touches on the Mapping the Universe masterclass and have it fully ready and published, and the same with a couple La Palma videos. Furthermore, I’ll be helping David prepare for the LancAstro conference on Friday the 4th of October, as well as preparing my own talk for it speaking about my internship experience. Here’s to another week of physics and outreach!
Welcome to the second instalment of my blog, covering weeks 3 and 4 of my internship. Previously, I had completed the theory video for the ‘Hunting For Distant Galaxies’ task, but now if you take a look at XGAL-DIY you’ll see that the whole task is online!
The task involves using data for the COSMOS field to find distant galaxies, with a little warm up of finding CR7. Using DS9, you set up the files so that two images of the same area of space, seen through 2 different filters, automatically switch between themselves – the distant galaxies are seen in one image, but not the other. An extragalactic spot-the-difference!
The majority of these 2 weeks were spent writing the script for the video, recording (and re-recording) the instructions and editing everything together. Thankfully, this task already had very clear, well-written instructions, thanks to David, Sergio, Joao and Amaia. I essentially had to create a video with very clear, slow, step-by-step instructions, and we decided it would be even more useful to have the written instructions on the screen as well, just for everything to be as simple as possible for kids of all ages. There was also some more information about CR7 and what the catalogues are showing which needed to be included – lots of images and time-lapses from La Palma were used again! For more information about Lancaster Astrophysics trips to La Palma click here.
The reason these tasks are so exciting is the fact that the kids will be using real data and finding high redshift galaxies in a similar way to how real astronomers find them. We’re hoping to encourage the kids to become astrophysicists, or at least have some fun while doing this task.
To make everything as simple as possible for both teacher and students, there’s also a separate XGAL-DIY page which is more step-by-step. This was just so we can access as many people and as many different ability levels as possible.
Another great part of this task, is the Google Form where you submit the coordinates of the galaxies that you found but also get to ask an astrophysicist a question – all David’s idea of course. This means that we will receive the answers and then the students will get feedback from a real astrophysicist – so many reasons to be excited! There’s also questions regarding how challenging and fun the activity is, meaning that we get useful feedback too.
Due to links David has with the local schools, this task will be being used in schools when the year starts in September, so then we’ll get more feedback, but more importantly, spread the word about how exciting being an astrophysicist is!
Still to come…
Hopefully there will be a ‘Level 3’ to this task coming at some point. In the larger COSMOS images, there are some ‘fake’ galaxies that have been artificially added in order for younger kids to be able to complete the task and also to make the objective easier to spot. So Level 3 will involve using real HST images in order to check the coordinate of the galaxies that you’ve found and see where it actually is a galaxy. Again this should be exciting because the kids will be using real data and using resources that professional galaxy hunters find.
However, this is not my task for the minute, as I am currently beginning the next task – Mapping The Universe. Look out for my next blog post and updates to the XGAL-DIY page to learn more about how to map the Universe.
A big part of the internship that I have been working on is the educational videos for XGAL-DIY part of the XGAL Blog. The general idea of XGAL-DIY is to have a task that people of any age can carry out which involves finding high redshift, very distant galaxies, presented in an exciting way which is super easy to follow. This is all linked to the discovery of CR7, which was a real and impressive discovery by a group led by Dr David Sobral here at Lancaster University, hence the excitement of the XGAL team to share it with the public.
So here’s the theory video! Feel free to like the video and subscribe to the XGAL channel.
This is the initial video of the series, which is the theory video, explaining a lot of the background concepts. I was working from an initial draft made by Amaia, which definitely made my job easier. In order to build on it though I had to refresh my knowledge of redshift and telescope filters but entirely learn from scratch about the Lyman break. This is the feature seen in the spectra of high redshift galaxies where, below a wavelength of 1216Å (Å = Angstrom = 10^-10m), no light is collected by the telescope for the galaxy. The reason that wavelengths shorter than 1216Å are not seen by the telescope is because they are absorbed by the clouds of neutral hydrogen within the galaxy itself and along the line of sight (in between the galaxy and the telescope). The value of 1216Å refers to the rest-frame wavelength (the wavelength actually emitted by the galaxy), but the observed wavelength (the wavelength collected by the telescope) where the Lyman break occurs will depend on the redshift of the galaxy, described by the following equation:
Here, λ is the wavelength and z is the redshift. In order to fully explain the concepts of both the Lyman break and redshift, I made this video:
Figure 3: A visualisation of how redshift changes the wavelength at which the Lyman break is observed.
This is the spectrum of a test galaxy and it shows that increasing the redshift also increases the wavelength that the Lyman break is seen. It also involves the filter profiles of the telescope used to collect this galaxy’s data. These were added to illustrate the idea that, depending on the redshift of the galaxy, it will be visible in some filters but not visible in others, due to the Lyman break.
The graphs used in this clip were made using a Python script which implements one of the fancy new LancAstro.py methods to plot the spectrum. For more information of the LancAstro.py project, check out the blog: https://xgalweb.wordpress.com/lancastro-py/.
The Plot2D.py script from LancAstro.py made it very simple for me to plot graphs which looked incredible without having to spend hours adjusting all of the axes and ticks etc; this had already been done for me! In order to have the redshift increase by 0.1 repeatedly, I needed a ‘for’ loop. This essentially meant that the equation shown above was calculated for values of redshift from 0 to 10, in steps of 0.1. Hence, 100 graphs were made, each one with the spectrum shifted slightly to the right compared to the previous one. This was converted into a smooth video using iMovie, which was really simple to use.
So this is just the theory part of the task, meaning the next steps are to produce the instructions video, so people can find their own galaxies from real data. This is a super exciting thing to be involved with and I really hope it gets a lot of engagement and teaches people some astrophysics whilst they also have fun!
Another part of the project that I have been working on is the 3D visualisation of a ‘fly through’ of the COSMOS field data. This initially felt like an overwhelming task that would never be completed! However, when broken into simple steps is seemed much more achievable. First of all, I had to learn how to use DS9, reacquaint myself with Python (it has been a while since I finished my MPhys project) and more specifically learn how to use .fits files in Python. Oh, and learn how to use a Mac! DS9 is a super useful program which makes viewing and editting images taken by telescopes.
Figure 1: The most basic fly-by, just positioning galaxies and zooming in on them.
Figure 2: A dramatically improved fly-by with many more galaxies, but still in need of a lot of improvements.
The first little clip, Figure 1, is a little example which just took a few images that had been created by hand in DS9 and, using a Python script, they were zoomed in on in a way that kind of represented us flying, but in an extremely basic way which didn’t include the redshift or true positions of the galaxies – this was just one of the many small steps necessary to complete on the way to the final video!
The next, Figure 2, is slightly more impressive. This actually involves all of the galaxy images in the COSMOS field which had been created fully in Python rather than DS9. However some adjustments to these images need to be made, because, as you can see, some are just blurs or grainy images that don’t even slightly look like galaxies. The first 20 seconds actually looks like we are flying towards all these galaxies, as we zoom in on them gradually. However, after 20 seconds, things get a bit…. Weird. The zooming just has a mind of its own as we zoom outwards again and then everything gets a little warped and stretched, but fear not – improvements are on the way!
So this explains the first two weeks of my internship, and I’m super excited for the next four! I’d like to thank everyone else in the AstroLab – Emma, Charlie, Amaia, Cass, Josh and Harry – for all the help with coding and ideas and, more importantly, all the fun we have in between working and making me feel really welcome here. Amaia also gets a special shout-out for being my internship buddy, producing the first draft of the theory video and helping out whenever I don’t know how to use the Macs.
Keep your eyes out for more blog posts, updates on the visualisation and more uploads to the XGAL-DIY section!
I think I’ve been thrown straight into the deep end with this project, but it’s leading to a lot of growth and learning on my part. As a first year, I’ve never coded and many of the concepts of the Lyman-Alpha emitting galaxies started off being completely foreign. So I thought I’d start with the relatively simple aspect of my project, outreach videos, while following along on an online course to learn Python coding.
For the first two weeks of the project, I created video tutorials for some of the masterclasses that the Lancaster University Astrophysics Department provides for groups of students, teaching them how the Cosmos Redshift 7 galaxy was found, including some background on Lyman-Alpha high redshift emitters, and helping them map out a 3D version of the SC4K galaxy catalogue on Topcat to get cool looking images like shown below in order to spark an interest in physics, particularly astrophysics, in the students following the masterclasses, with interactive and visually appealing methods.
Figure 1: SC4K galaxies plotted by their RA and DEC coordinates, as well as their distance in MegaParsecs, with a color scale of Lyman-Alpha Redshift
While doing this, I was also learning how to code on Python, starting off with the classic print(‘Hello World!’), that anyone that’s ever learnt how to code has begun with. Starting with absolutely no knowledge of coding whatsoever, I have made massive progress and can now understand some astropy codes, and even write basic ones of my own.
The final outcome of this project, as well as the outreach videos, is meant to be a flyby of the 3908 SC4K galaxies as they are situated in space formed of colored images of them. Over the past few weeks, I’ve been testing how to combine Hubble Space Telescope (HST) images (that are high resolution but in black and white) with SUBARU images of three different filters (COSMOS.B, COSMOS.gp, COSMOS.rp) that give color to the image but are low resolution. The quality of the images I have produced has gone up over time (starting with the…. interesting psychedelic image I first created), as I learn the scale parameters that are appropriate to get the right coloring of the galaxies (progress shown below).
Figure 2: Progress of an image produced of the SC4K-NB392-2 galaxy
At points in the internship, I’ve felt like I’ve not made progress, and often felt very very dumb when comparing myself to the other fantastic interns working with me. However, they’ve done a fantastic job to reassure me that, after all I am only a first year and that this experience is serving to learn a lot, and that I’m making really good progress considering how little knowledge I had when I started. Further along in the project, a code needs to be made to automate this process (because doing it by hand for 3908 galaxies is quite the job!), as well as a code to create the actual flyby.
I also now have Heather Wade that has joined me on the project, meaning that hopefully we’ll be making faster progress in order to get this project done in time, and having her to work with has so far made the experience even more enjoyable.
So far I truly am really enjoying this internship, it’s been a great learning experience and something that I can take forward into future projects. I’m loving working surrounded by interesting people, and getting an insight of what I’ll eventually be able to do with my degree and how the department works.
If you have been interested by the work I have been doing keep checking this blog, as I shall upload further updates in the next week or two.
XGAL: Time travelling through the Universe 