Archive | August 2012

Recycling features from around the Zooniverse

Cecile Faure and Brian Carstensen

At the Zurich workshop we looked at some of the already existing or in development zooniverse projects, to see what features we could borrow, copy or adapt in the lens zoo. There’s some useful bits and pieces we can recycle – see what you think!

  • Visible progress on the starting page: We  thought it might be nice to have a “skywalker” on the starting page, showing the total area of sky being investigated. In our first case, this would be the CFHT-LS survey.  This feature will be in use in some of the new projects (e.g. Sea-floor explorer) – it’s a nice way for us to see how far we have got. We also would like a progress report on this page such as in the Milky Way Project.

  • Pop-up tutorials: The majority of the people who met in Zurich thought that the initial classification process should be guided by little pop-up help boxes, like it is in Moon Zoo
  • Online scientific discussion: To enable this, we think we’d like to use a Talk-like forum, as is done in PlanetHunters – although there are some aspects of it we’d like to change as well. In addition to the ability to discuss candidates, we would like you to be able to vote on them, to make the most of the expert volunteers’ experience. This would be a new feature – none of the Zoos have this yet!

  • Annotating images: In order to have a good discussion about a lens candidate, we need to know which features we are talking about! We could do this by enabling you to put markers – like thumbtacks – on the images, during the classification stage. We think this would help a lot in the discussion, as each volunteer could indicate exactly what he/she is talking about. We could also then collect the coordinates of the objects in a database to make further analysis easier. A similar feature  is already in use in Ancient lives.

  • Links to social networks: It was not much discussed, but it feels like this is necessary: new users might well find it fun to show off their new discoveries on facebook, etc, and this might then encourage more people to get involved. We’d like to find as many new LensHunters as we can!

  • Volunteer achievements: At the moment, Galaxy Zoo users are labelled as newbies, heros and so on, according to their activity level on the forum. This is great – new users can see who has been there longest and is most active in helping others get started. Is there more feedback we could give users, that would improve their experience? Would you like to see your achievements logged in terms of the number of images you have inspected? Or the number of good lens candidates successfully detected? Or something else?
  • Zoonibot:  Wikipedia has various “robots” that wander around its system, automatically making small corrections and suggestions. The Zoonibot is a first attempt at one of these robots for the Zooniverse Talk system. There are many things the Zoonibot could help with – such as pointing new users towards some of the reference and tutorial material on the site, if they seem sto be getting stuck. While we don’t want it to replace human interactions in the forum, it seems like the Zoonibot could be helpful in some situations. What do you think?


One more consensus came out of the workshop: it’s great if a zoo website *looks good.*  There are some very talented designers working at the Zooniverse, who can help turn your ideas into reality. Keep them coming in the comments!

 

 

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The first LensZoo project preview: beat the robots of the CFHT Legacy Survey!

Anupreeta More, Surhud More and Phil Marshall

Gravitational lensing is a spectacular phenomenon found in the Universe.  Predicted by Fritz Zwicky in the 1930’s, galaxies and clusters of galaxies acting as lenses are not just beautiful to look at but they also have plethora of applications, including revealing the whereabouts of the elusive Dark Matter. Gravitational lenses are rare objects since we require the foreground and background galaxies to be aligned on the sky to within a few thousandths of a degree.

Over the coming decade, larger and larger imaging surveys will map out ever wider and deeper regions of the Universe. This means we should be able to find more gravitational lenses, but it also means that we will have increasing amounts of data to inspect in order to find them. As a result, we would like to automate the process of finding gravitational lens systems from these vast treasure troves of data. However, as you know, discovering gravitational lens systems requires some skill, and the lens candidates need to satisfy a varied set of criteria before they can be tagged as promising lens systems. Our brains are more suited to carry out such tasks than are simple computer algorithms, so it makes sense for humans to look at the candidates that the robots flag as interesting. However, so far, astronomers have had difficulties in building robots that are capable of finding all the different kinds of lens systems that are potentially interesting. This is partly because we have not yet discovered very many lenses, nor exhaustively cataloged all the things that look like lenses but are not lenses in reality. To understand how to make the robots work better, we need to jump in to the data alongside them!

Our first project in the Lens Zoo is going to be a slightly unusual one, in that it’s focus will be on beating a lens finding robot, rather than checking through its outputs. We are going to use the optical and infrared data from the Canada-France-Hawaii Telescope Legacy Survey (CFHTLS) for this project. With the help of computer algorithms called “ArcFinder” and “RingFinder”, we have found a sample of lens candidates from the CFHTLS – but we know that these algorithms don’t do a very complete job. Opportunity knocks!  We would like the citizen scientists of the Lens Zoo to help us search the images of the CFHTLS to discover a variety of lenses which were missed by our robots.

The CFHTLS spans an area of about 170 square degrees of sky. It’s images are both higher resolution than those of the SDSS, with median seeing in the i’ band of around 0.7 arcsec, and deeper (i’ < 24.5 magnitudes) – which means that more gravitational lenses should be visible per square degree. The picture on the left shows a lens from CFHTLS that the ArcFinder did spot, a small galaxy group that is lensing a background star-forming blue galaxy. On the right is the SDSS image of this system, to show you the difference in image quality.

     

 

 

 

 

 

 

We have two goals for this project. First, we want to find all the gravitational lenses that the aforementioned algorithms missed – perhaps because the sources are quasars, or distant red galaxies, or because the lenses are complex, or confusing. Second, we want to catalog all the objects that look like lenses, but are not: these “false positives” will make an important training set for us to test our improved robots on.  This will be the first time that this survey’s images will have been exhaustively inspected – so there are bound to be some surprises!