Voorwerping, Part 1
I’m working on the Suzaku data that we’ve obtained on IC2497, the galaxy next to Hanny’s Voorwerp. X-rays, especially the really energetic ones that Suzaku is able to detect are probably the best way to probe whether the black hole in a galaxy is actively feeding or not. Shanil Virani and I are currently working on the data reduction and analysis, which is quite challenging. Early indications are that the data will show us some really exciting things, but the problem is that they make us really scratch our heads. It may yet take us quite a while to see if we understand what’s going on and we may have to pick the brains of a theorist or two. So, stay tuned….
The Hyper-Velocity Stars Project: Serendipity at its Best
Hello everyone and thank you for reading this blog post. You will read how a group of people, non-professional astronomers, from around the world got together to seek a common goal.
My name is Aida Bergés and my Galaxy Zoo name is Lovethetropics. I’m Dominican by birth but live in Puerto Rico, and I hunt Irregular Galaxies, asteroids, Voorwerpjes and now Hyper-Velocity Stars.
The Hyper-Velocity Star Project was due to one of those many accidental discoveries that happen at Galaxy Zoo. I was looking for irregular galaxies for Waveney’s Irregular Project. I saw an intensely blue star and checked it out to see if it was a white dwarf (it amuses me to no end that white dwarfs are all blue). It wasn’t. SIMBAD said it was a Hyper-velocity star. I kept looking for more irregulars, five minutes later saw another very blue star and checked it too – expecting it to be a white dwarf; but it was another HVS. At that point I looked the name up because I had never heard of that type of star. It is a star moving at a vast speed relative to the rest of the galaxy. Possible explanations for this are being flung away from a black hole; being part of a galaxy merger; a binary system being disrupted either by a black hole, the proximity of another star, or one of the pair going supernova . . . and so on. They can travel at about 4000 kilometres per second, and seem to be heading out of our galaxy! All the ones discovered are massive and blue.
I posted the two stars and a brief explanation on the newbies thread. The newbies thread was started by Thomas Jennings, Thomas J or “Tommy” on the forum, on my “zoobirthday” – the day I came to the Galaxy Zoo Forum. A week or two later, Alice Sheppard, Galaxy Zoo moderator and close friend, asked me to post an Object of the Day. I said yes but had no idea what to write. Thomas J reminded me of the hyper-velocity stars I had posted on his thread.
Tommy and I started to look for papers about hyper-velocity stars and he found a powerpoint presentation made by one of the Zookeepers, Jordan Raddick. At the time Jordan created it (2003), there were only three confirmed hyper-velocity stars. All of this dialog was written on the Object of the Day thread, which meant we started to get the attention of and much help help from other zooites. Mark Redgwell – BlackProjects on the Zoo, from the UK – found more papers. When I wrote the Object of the Day we had found 10 hyper-velocity stars, but they didn’t have an SDSS number and I had no idea on how to get them. Tommy again came to the rescue and found their SDSS ObjIDs, and I posted these onto Object of the Day.
It was a hit! We started getting help and more papers, especially from Stellar, 14, child genius from the UK who should be in college already. We found out there were 16 confirmed hyper-velocity stars, most of which had been found by Dr. Warren Brown from the Smithsonian Astrophysical Observatory and Harvard University. He is the outmost authority on HVSs, and you’ll be hearing more about him in a minute . . .
The question came up on the Object of the Day: How can we find more of these mysterious stars? Many Zooites joined the discussion, especially Mukund Vedapudi from India, Jules Wilkinson from the UK, and Dave, Curtis Garrett and Gargleblaster, all from the USA.
We decided we needed our own place to talk, for one thing because we were burying newer Objects of the Day, and for another this was the time of the forum merger which caused a few technical problems. Waveney (Richard Proctor, UK), our “fairy godfather”, offered his test forum, where a handful of zooites play. It’s more private than this one, but nevertheless we kept getting links to papers and articles from Jamartins from Portugal. By now nine or so of us had decided we were a team.
I have an interview for our “She’s an Astronomer” blog project on October 1st, and as it loomed closer and closer I wanted us to have a first post back on the Galaxy Zoo Forum so as to have a link from my interview, and to invite all zooites to join us. Stellar and I worked for 16 hours with some help from Alice and Half65 from IT – both of whom became part of the team, too – we posted our own thread, started a blog and a twitter account, and got ourselves a gmail account so we could spread the word that we are looking for Hyper-Velocity Stars and help from anyone who would like to work with us or advise us.
Jules, Dave, and Mukund Vedapudi have between them found 40 possible hyper-velocity stars, about half of which have a known radial velocity, and which you can examine here. Our new thread has grown to six pages due to the interest of our fellow Zooites; and yesterday I received a lovely personal message from Oswgeo9050 presenting another possible candidate, just from examining the spectra! She’s just joined us, too.
Help is flooding in, some from astronomically unexpected quarters. Karen Masters , who works at Portsmouth University, runs the “She’s an Astronomer and Galaxy Zoo” project, and has been part of Galaxy Zoo’s work on dust in galaxies, red spirals, and outreach generally, just happens to be a former colleague of the very Warren Brown mentioned earlier! It is due to her kindness that we have just got in touch with him – he has heard about our work from Karen and has graciously sent us pointers on how to find more Hyper-Velocity Stars. It looks like it’s going to be tricky: there is only one of these for every 100 million “normal” stars, and there is in any case an error range of 220 kilometres per second (plus or minus) due to our own Solar System’s rotation round our spiral galaxy!
Just to add to this, on Wednesday 9th September, we heard from ZookeeperKevin that he was about to meet Warren Brown and hoped to set up a collaboration. We had a few hours to decide exactly what sort of help from the experts we wanted, and to send him our first e-mail! This was no easy task, not knowing the ins and outs of academic life. We waited on tenterhooks, our hearts pounding . . .
On Thursday evening Kevin got back to Alice. He and Warren Brown had taken a look at some of the candidates. He believed that none of them were hyper-velocity stars for many reasons, one being that the SDSS people have already combed the data. But, apparently, “one object looks interesting”. We don’t yet know what that is, and just have to wait for him to – and this is the good new – join the forum and talk to us more, which apparently he will be doing!
What will happen next? There are probably more stones to unturn. Even if we fail, we still set up an exciting project and discovered many things – as amateurs who decided to work together. In the meantime, please join us to put forward any questions, suggestions, and ideas.
Very special thanks to Zookeepers Jordan, Karen and Kevin for taking such an interest in our work and kindly providing so much information and hope. We also thank Geza Gyuk from Adler planetarium http://www.adlerplanetarium.org for his enthusiastic help.And thanks to our fellow zooites for being serendipities with all of us!
The Galaxy Zoo Library
Dear Zooites,
I’d like to throw open the doors and welcome you to a relatively new area of the forum: the Galaxy Zoo Library.
We’ve been constructing this for a while. The original idea was EigenState’s. He did a great deal of splendid work planing and putting up the first gleaming shelves. Sadly, he’s left now; so Waveney, Hanny and I have put up some more library areas; Geoff has offered to help me run the Library for the time being; and I’d like to invite you all to come in and use them.
The Library has several purposes. First of all, it’s a place to store the Galaxy Zoo papers. EigenState gave each paper two threads of its own: one, a locked one with bare information; second, a discussion thread for each one. You can find links to each of these in his Master Index.
Waveney has put up a concise storyline about the process of each paper, including the abstracts, and all the Galaxy Zoo Blog links about each one. Not all of our papers have actually been accepted yet. Those which are accepted appear as a link to their arXiv page. This way, you can follow the lives of each paper: their writing, their results, their acceptance – and those papers that build upon each other; for science is often a series of many steps.
Do you find scientific papers rather hard to understand? I do. I read lots of them for university and after four years still couldn’t make head or tail of them. I nicknamed their language “journalese”. Scientific papers are written for a special audience; and some people – not necessarily just scientists – can extract masses of information out of them. I’d like to invite any Zooite to write summaries of what each paper means, or to “translate” various parts of papers – whatever parts you like! – into easier language. That’s not to denigrate this wonderful blog; I’ll be linking to relevant entries whenever possible, too. What I’d really like us to do together, and I know it sounds ambitious, is to see if we can, together, when we’re ready, get more fluent in journalese. Dozens of us have in redshift and spectra. Let’s see what happens!
From SDSS: a flying notebook in space!
EigenState also created a Reading List of useful books to read: some hefty, formal, and academic, others not. He invited people to contribute their useful reads, and there is also a Reading List discussion. The subjects of these books include galaxies, cosmology, physics, gravity, quantum theory, practical astronomy, popular science, humour, and more.
Hanny wrote a list of Galaxy Zoo items in the media, which she blogged about a few days ago. You can find this both in Latest News and in the Library.
And what about sharing books ourselves? Chatting about them, recommending them to each other – and reviewing our favourites (or even least favourites!). I’d like to invite any of you to write a review of any books you liked, disliked, found useful, or would generally like to show us. You can send it to me or to Geoff. The reviews will be kept in this locked thread – but as you’ll see in that link, we now also have plenty of comfy threads to be more informal in and drink our coffee.
I’m hoping that this Library will cater for all tastes: those who like quiet, carpeted, stained-glass-windowed libraries with hushed footsteps and deliciously difficult volumes; and those who like bean bags, paper aeroplanes and a nice pile of books and fun websites to pelt each other with and enjoy. On that subject, I can’t imagine anything sadder than an empty, unused paper aeroplane thread; so do please post your favourite scientific sillinesses in there. I have a special fondness for Eric Idle’s Galaxy Song.
Voorwerpje Hunting for Beginners
Three months ago I like the rest of you had never heard of a Voorwerpje. Laihro had been working with Bill Keel on the hunting for active galaxies with ionized gas clouds, and had worked out a way to extract active galaxies from SDSS, and had the idea of using my hunting program to search through the list. Two further lists of likely candidates also came from Kevin (from X-ray galaxies) and Bill (known active galaxies). This hunt needed a good tutorial, which Bill wrote, and then the hunt was launched. Voorwerpje hunting was looking for needles in haystacks, most images didn’t have a Voorwerpje, but it included some very pretty and interesting galaxies – enough to keep me in OOTD candidates for a year.
You all agreed on this one (otherwise known as NGC 5256 or Markarian 266).
Flying amongst galaxies
As anyone who has created their own tour will tell you, Microsoft’s WorldWide Telescope is a fantastic tool for exploring the Universe. While the web based version will do for viewing your Galaxy Zoo favourites, the real power comes with downloading the new `Aphelion’ release – which depended on Galaxy Zoo users for one of its best features.
Worldwide Telescope gives you the chance to fly amongst the galaxies of the Sloan Digital Sky Survey. While before each galaxy was represented by a randomly selected image, in the new version the correct type of galaxy is shown in the correct position. The team at Microsoft relied on Galaxy Zoo to tell them where to put a spiral and where an elliptical, and then matched templates to the observed size and brightness. As a result, in flying around the Sloan you’re also exploring the results of all those clicks – which should inspire you to get back to Zoo 2 for more.
Stripe 82 and colour images from Sloan
As Chris blogged yesterday, Galaxy Zoo now contains colour images from the Sloan Digital Sky Survey’s Stripe 82.
The new Stripe 82 images you see are made of an addition of approximately 50 ordinary SDSS images, which means we can see things about 2 magnitudes fainter (about 7 times less light). It’s only over a relatively small patch of the sky – 270 square degrees compared to the full survey which is nearer 8000 square degrees – but the extra depth should be useful to us in many ways even though it’s only over a smaller area.
Many users will already have noticed that the standard images supplied through the Navigator interface are in black and white – they’re just in the r band (SDSS has 5 bands named u, g, r, i and z of which g, r and i are normally mapped to blue, green and red respectively). Naturally, we wanted to supply the Zoo with colour images like those in the ordinary Sloan survey.
This proved to be somewhat tricky as access to the data needed to compile the colour images comes in fairly large chunks called ‘fields’ – each field is 2048 by 1489 pixels, large enough to more than fill a typical computer monitor. So we had to download several of these images for each galaxy (one for each of the red, green and blue parts), combine them together, and extract just the bit around the galaxy we wanted to show you, scaled to the size of a normal Galaxy Zoo image. This took a fair bit of programming and many days worth of computer time for the downloads of the data and processing.
Two images from the same area, the upper from a standard SDSS image, and the lower from the coadded stack of about 50 images
Another complication was that astronomical images usually come in a format that’s not immediately suitable for viewing. They can have a tremendous dynamic range, from the tiny amount of light that comes from the dark bits of sky to the dramatic overloading the camera gets when it images a bright star. The task of reducing this down to fit in the brightness scale of 256 levels of each of red, green and blue that a computer monitor will display is not easy.
Fortunately, this problem had already been solved. For those interested in the gory details, there is a paper here by Lupton et al., which describes the system used in these images and the ordinary SDSS images you’ve been seeing before. It’s a bit mathematical, but what it does is three important things:
- For faint objects, the brightness of the pixel is roughly in proportion to the amount of light received. This shows up faint details nicely but…
- For bright objects, we’d hit the cap of 256 levels on the monitor too quickly, so it starts to scale things logarithmically instead. This means that doubling the light wouldn’t double the value of the pixel but just add a certain amount on. If 10 units of light were collected we might have a pixel value of 1, 100 units would be 2, and 1000 units would be 3, and in this way we can fit the brightest objects nicely into the range our monitors provide us with. This is the same way that astronomical magnitudes work as well.
- Lastly, we want to get the colour of objects right. If we had a really bright object we might find that even though it was very red, it still gave off so much green and blue light that the pixel ended up with high values of red, green and blue, and end up looking white as a result. The code we use compensates for that and makes sure everything has its actual colour represented properly.
In order to use this, we need to decide on how steep the slope of our conversion from light to pixel values is, and also at what point we tilt over from our function for faint light to our different function for strong light sources. This takes a bit of fiddling, and to be honest it’s as much an art as a science, and we have to use different values to the ordinary SDSS images as we have a different amount of light overall in them. This is why our background sky ends up looking more speckled than usual (there’s more background noise and having it more visible is the price we pay for having faint features of galaxies visible too) and the galaxies themselves look like they’re stretched differently.
One of the developers of this technique, Robert Lupton, has a webpage which shows part of the Hubble Deep Field coloured the conventional way and using this technique, and you can see how the colours of the galaxies are better preserved this way.
I hope that gives a bit more insight into these images, how they were made and why they look a little different from the usual. We look forward to finding out how the classifications go!
Galaxy Zoo 2 in Science Festival in Warsaw – Galaktyczne Zoo na Festiwalu Nauki w Warszawie
We would like to show Galaxy Zoo 2 on the special exhibition during the Science Festival in Warsaw, September 26th/27th, . The Galaxy Zoo stand will feature poster and 2 computers armed with internet access to allow visitors to taste the Galaxy Zoo on the spot.
Chcemy pokazać Galaktyczne ZOO 2 w czasie Festiwalu Nauki Młodego Człowieka, 26/27 września w Warszawie, . Na naszym stanowisku pokażemy plakat i udostępnimy dwa komputery, przy pomocy których widzowie będą mogli wypróbować Galaktyczne Zoo na miejscu.
We need your help to organize all this. Experienced Zooites, preferably from Warsaw and the neighbourhood, who could spend a few hours explaining Galaxy Zoo 2 to visitors during the exhibition, please contact us at galaktycznezoo@astronomia.pl .
Thank you very much for your help!
Your Galaxy Zoo PL team
Potrzebujemy Waszej pomocy przy organizacji tego przedsięwzięcia. Doświadczeni członkowie społeczności Galaktycznego Zoo 2 z Warszawy i okolic, którzy chcieliby spędzić kilka godzin na wystawie opowiadając widzom o Galaktycznym Zoo proszeni są o kontakt mailowy na adres galaktycznezoo@astronomia.pl
Dziękujemy za pomoc!
Zespół Galaktycznego Zoo
Stripe 82 : Digging Deeper
Anyone who has been classifying galaxies today may well have noticed a big change in the Zoo; the addition of some new images that don’t look quite like the previous set. These new galaxies come from a very special part of the sky known to the Sloan team as “Stripe 82”.
Over the first seven years of the Sloan survey, the telescope returned again and again to this part of the sky, comparing images from each visit in an attempt to discover supernovae (exploding stars) and detect objects which change in brightness. A nice side effect, though, is that we can add the different images together. This produces the same result as having left the telescope pointing at the same place for longer; images which show fainter objects and (hopefully) more detail in familiar ones.
This was too good an opportunity for us to pass up, and so we’ve added the Stripe 82 images to the Zoo. They look a bit different – more background noise, slightly different colours – but these are the deepest, most detailed images we’ve ever presented to Galaxy Zoo users. There are more than 40,000 new images – so get clicking!
Galaxy Zoo in the News!
Last year Kevin wrote about all the publicity we gained so far, from media covering the story of Hanny’s Voorwerp. In the meantime, that list kept growing. But also, with the launch of Zoo 2 and the discovery of the Peas, we got more and more attention.
Recently Kevin asked me to make a list of links to all those pages writing about Galaxy Zoo and to announce here where you can find it, which is on the Galaxy Zoo Forum. If you find an article I haven’t on my list yet, please feel free to send me a personal message so I can include it. And if you’re not a member yet, you can also send me an e-mail using: vampke83(at)hotmail.com.
Let’s keep spreading the word.
A Galaxy Zoo – WorldWide Telescope Mashup
Have you ever found yourself staring proudly at the collection of beautiful and exotic galaxies that fill your favourites list? Have you ever wanted to share these objects with a friend or loved one and realized there was just no easy way to do it? Sure, you can click on the image, delve into SkyServer, and copy and paste one image at a time into an email, but… That gets kind of tedious pretty quickly, and if your favourites list is like mine, it’s not a 5-minute copy and paste kind of task.
Well, now there is an easier way to inflict your favourites on others.
We’re excited to announce the integration of WorldWide Telescope with Galaxy Zoo favorites. Over the past few months we have had the opportunity to work with Microsoft Research to bring your favorite galaxies to WorldWide Telescope. Instead of seeing an isolated image of the galaxy you can now immerse yourself in the WorldWide Telescope environment through easy to save and easy to share sky tours. We hope this allows you to better see your galaxies in their home environments on the sky.
This new tool, available at http://wwt.galaxyzoo.org, was created by two of my Southern Illinois University Edwardsville undergraduate students: sophomores Jarod Luebbert and Mark Sands. To give you a taste of how this interface works, they’ve created this great teaser video. We plan to push this out to the public on September 2, but because you’re reading this, you get a special sneak peak of both the website and the video.
Galaxy Zoo – WorldWide Telescope Mashup! from Galaxy Zoo on Vimeo.
Galaxy Zoo 