A Spindle in the Dragon
This week’s OOTW features Alice’s OOTD posted on the 30th of December 2010.
NASA, ESA, and The Hubble Heritage Team STScI/AURA
This is the Spindle Galaxy, otherwise known as NGC 5866. It’s a beautiful lenticular that lurks 44 million light years away from us in the constellation Draco.
Lenticular galaxies are a bit like spiral galaxies in the fact that the main part of the galaxy is a flattened disk of stars, but like an elliptical galaxy they have no arms. The star forming material in lenticulars is mostly used up, so these galaxies mostly consist of old stars rather than new ones.
NGC 5866, unlike most of the galaxies that share its morphology, has a dust line stretching through its galactic plane – its disk – and as the dust lane is perfect for churning out stars, it has a string of hot, young, blue stars accompanying it.
The images on MAST and the Hubble Legacy Archive are certainly worth a look too!
Happy New year! 🙂
When do we see the Hubble results? The final countdown.
Now it can be told – the Hubble results on Hanny’s Voorwerp and IC 2497 will be released in a press conference on Monday, January 10, at 12:45 p.m. Pacific Standard Time. This is during the meeting of the American Astronomical Society in Seattle, where two presentations will discuss recent work on Hanny’s Voorwerp (and a couple of additional poster papers deal with “voorwerpjes” from the Zoo). You will see some familiar names on the press event schedule, and more should be there for the event itself (we’re keeping a little bit of mystery still). That time converts to 2045 UT, 2145 in the Netherlands, and so on). At that time, the processed color display images will also be visible and available for download. Watch the blog – we will have a lot more to say at that time, with full background on what the data show and what it means.
Keep in mind – there will be a lot more detail to see than this image from the WIYN telescope shows! Not only that, but the Hubble data span from the ultraviolet to the near-infrared. That let us pick out PHRASE EMBARGOED and quite unexpectedly, see TOPIC NOT YET RELEASED. Only 11 days to go – I really need to get our presentation graphics finished!
Galaxy Zoo in der Süddeutschen Zeitung
Ein Artikel über Citizen Science und Galaxy Zoo ist in der Süddeutschen Zeitung erschienen, inklusive Kommentare von einem Mitglied des “Peas Corps”.
Mergers Author Poster
The final in our series of Zooniverse project posters, created from the names of contributors, is Galaxy Zoo Mergers. The posters features an image of the Antennae Galaxies made up of the names of the 13,000 mergers participants who agreed to have their names published.
You can download the large, 5000-pixel version (15 MB) or the smaller 3,000-pixel version (6 MB).
Galaxy Zoo Multi Mergers
Our latest merger paper is called “Galaxy Zoo: Multi-Mergers and the Millennium Simulation.” We used the original catalogue of 3003 mergers from the previous mergers study to find the interesting subset of systems with three or more galaxies merging in a near-simultaneous manner. We found 39 such multi-mergers (which you can see in the image below) and from this we estimated the relative abundance of such multi-mergers as being ~2% the number of binary mergers (which were themselves ~3% the number of isolated ‘normal’ galaxies). We also examined the properties of these galaxies (colour, stellar mass and environment) and compared them to the properties of galaxies in isolated and binary-merger galaxies; we found that galaxies in multi-mergers tend to be more like elliptical galaxies on average: they’re large, red and in denser environments.
Describing what we see in the world is all well and good, but the equally important thing in science is to compare what we see with what others have claimed to see or to have predicted through theory. Since ours is effectively the first such catalogue of multi mergers, there simply are no other observational sets to compare to. We therefore compared these merger fractions and galaxy properties to a large and well-known simulation called the Millennium Run. This is a cosmic scale simulation of Dark Matter that starts off smoothly distributed (similar to the CMB) within a 500 Mpc box and, over time, clumps together to form structures. Now, galaxies are of course made out of normal matter, so to model how galaxies form and evolve within the Dark Matter, one can take the resulting clumps of Dark Matter from the simulation and, using sensible sounding rules (e.g. bigger Dark Matter clumps get more normal matter because they’ll gravitationally attract more), come up with predictions for numbers of stars formed within the simulation (and where, when, etc.). This means that one can create (with enough fiddling) predictions of what galaxies will look like in such a Dark Matter dominated Universe. These are called ‘Semi-Analytic Models’ and are an important strategy for simulating the Universe since computers would struggle to compute the many many additional interactions between particles in a full N-Body simulation with both Dark Matter and normal matter (Dark Matter is relatively easy since it only feels the 1/r^2 force of gravity).
So what we did in the paper was to compare the results of our multi-merger galaxies to those of the Semi-Analytic Models in the Millennium Simulation (double ‘n’ because it’s a largely German initiative). This is a good test of the Semi Analytic Models because there is no way they could have been fiddled to get the right answer because ours is the first such observational constraint on what multi-mergers look like. And what we found is that the Simulation did rather well – it predicted the relative abundance of multi-mergers to within a few percent and it predicted that galaxies in these systems should have properties more like a typical elliptical rather than a typical spiral. This gives us independent confidence that these Simulations are on the right track and that the assumptions that went into them are sensible ways to get at how the Universe behaves.
In the future, the Galaxy Zoo interface might well allow users to indicate the presence of multi-mergers!
Many thanks to you all for your help in making this interesting study happen.
New content. New images. A refreshed Galaxy Zoo.
This month the advent calendar has brought you beautiful images (some covered in your name), new Zoos, and much laughter. On the 22nd day of advent the Zooniverse brings to you a new way of exploring galaxies. It’s not another galaxy related Zoo (we did that already with The Milky Way Project). It’s not a new task in Galaxy Zoo. It’s something a lot simpler: It’s words and images and even history discussing what we know and how we know it about extragalactic astronomy. We call this new section of the website “Explore Galaxies.”
Along with bringing you new content, we’re also bringing you new images!
Through your combined efforts, you’ve classified your way through the Hubble Space Telescope’s GOODS, GEMS and AEGIS images. This means it’s time for new images! Today we’re introducing to Galaxy Zoo a large batch of images from COSMOS: The Cosmic Evolution Survey. These images, taken during 590 orbits of the Hubble Space Telescope, map out a 2 square-degree region of the sky. While tiny compared to the area of the Sloan Digital Sky Survey, these images are sensitive enough to see objects almost 100 times fainter! (For those of you wanting the numbers, SDSS gets to i = 22.3, while COSMOS gets to I > 27!) These images have been used to map out the distribution of dark matter and the large-scale structure of the universe. Now, thanks to you, these images can extend our understanding of galaxy morphology out to more distant galaxies and down to fainter nearby galaxies.
Day 22: Galaxies and Content, these are our gifts to you.
And more will be coming. The content we have up today isn’t comprehensive: it’s a base layer that will be growing over time. As you search for content, we’ll track what you search for and add needed content. As the Zooniverse continues to discover new things – as you discover new things – we’ll work to add that content too. For advent, we offer you a chance to start learning about galaxies on the Galaxy Zoo website, and we’ll work to make it possible for you to keep learning in the times to come.
In addition to adding content to Galaxy Zoo, we also added a set of quiz questions. This your chance to test your knowledge of galaxy related concepts, one question a day. Any of you who have used Moon Zoo (which should be all of you – really, if you haven’t already, go try it out at http://www.moonzoo.org) have seen these types of questions before. Just as we use your responses to the classification tasks to do astronomy research, we use your responses to these quiz questions to do learning research. When you answer these questions, we’ll tell you if you got them right or wrong, but because you may see the questions again (and because that friend or family member looking over your shoulder may see the question later), we can’t explain the right answer if you get the question wrong. This is only a temporary problem however. After we get enough data (sadly, this may take a year) to see what you are learning, we will post all the answers in Explore Galaxies.
On this 22nd day of Advent, our gift to you is information. Please: go read, go learn, go search, and know that more content is coming as we learn what you want to know (and let us know what you do know by answering the once a day quiz questions).
Galaxy Zoo Image of the Year
The 19th door opened of the Zooniverse Advent Calendar leads us to M51, the beautiful Whirlpool Galaxy, taken on the SDSS telescope that we used for Galaxy Zoos 1 and 2.
For a few days after 25th November, the Galaxy Zoo Forum nominated their favourite galactic images from the thousands gathered over our three and a half years of existence, and voted on 48 of them. Here was the selection – as you see, it was a tough choice!
The winner was the stunning blue spiral, merging with a yellow galaxy so torn apart by gravitational forces that it would be hard to classify!
M51 is 33 million light years away and so bright that it has potential to fry the SDSS camera’s delicate optical instruments – so SDSS avoided looking at it too directly. Therefore, it has no reference number; but you can go into its pages and move up, down, right and left by adjusting the RA and DEC until you can more or less centre in on it.
M51 was discovered by Charles Messier, and put into his collection of objects that he thought were pain-in-the-neck smudges giving him false hopes of having discovered a comet! Jules wrote an Object of the Day about him and some of our other Messier Objects on the forum here. The pair of galaxies are also known as NGC 5194 and 5195. I’ve seen them described as 23 million, 31 million and 33 million light years away. The spiral is large, and famous for its dust lanes and intense star formation. You can resolve it in dark skies with a good pair of binoculars; it’s in the constellation Canes Venatici, though you find it just south-west of the brightest star of the Plough’s “saucepan handle”.
You can see a great deal more of this gorgeous object at Hubblesite, Astrocruise, NOAO and four different views altogether (and probably quite a few more) on APOD! The SDSS Telescope also has it proudly displayed on its home page, with a caption if you zoom in.
It won by only 1 vote; many other galaxies got almost as many. We’ve had plenty of time at Galaxy Zoo now to decide which galaxies we love best . . . and the answer is quite often “all of them”. M51 has never had any special attention on the forum that I recall, though it has of course had its fair share of admiration. I guess there are just too many things there to love!
A galactically happy Christmas to all our zooites from our oldest Zooniverse project.
A Dark Secret in Virgo
This week’s OOTW features my OOTD ‘A Dark Secret in Virgo‘ posted on the 11th of December 2010.
On the 17th of March 1781, Pierre Méchain discovered this beautiful galaxy. NGC4254 lurks 50 million light years away in the constellation Coma Berenices. It’s a disturbed spiral, with its right arm jutting out further than the other. So what’s caused this? Let’s zoom out…
There’s nothing to see that could have caused the disruption, right? Well, let’s zoom into this patch of sky in Coma Berenices’ next door neighbour, Virgo:
Is it a black hole? No. Is it a gigantic cloaked alien ship that tugs galaxies?! Nope. It is in fact VIRGOHI21; a HI region 50 million light years away that was first detected by the Lovell telescope. A HI region is a mass of neutral hydrogen, and in this case it has hardly any or no stars. But there’s something more to this object than meets the eye…
This is a screenshot of an animation (my attempts at posting the animation here failed!) which shows a map of VIRGOHI21. According to this website here the larger brighter mass is NGC 4254, and you can see the cloud is cascading down from the disturbed spiral arm in a stream of neutral hydrogen to the centre of the image. Astronomers have calculated that the total mass of this HI region is 2×10^8 Mʘ (solar masses), but the velocity and spin of this object indicates that there is more mass than we can detect and so the object actually has a mass of 10^11 Mʘ! So where does the rest of the mass come from…?
Dark matter! It is currently thought that VIRGOHI21 is a dark galaxy, which is a starless galaxy made up of mostly dark matter with little else apart from dust and hydrogen. This dark galaxy is interacting with NGC 4254 like any other normal galaxy would!
VIRGOHI21 is currently the best dark galaxy candidate out there, but others include HE0450-2958 which is a quasar that appears to be galaxy-less! Usually quasars have a host galaxy, but this one doesn’t appear to have one that we can see, so it has been proposed that the Quasar is actually part of a dark galaxy.
A survey called AGES uses the Arecibo observatory to find HI regions that are in connection with dark galaxies: http://www.naic.edu/~ages/
Zoo Limericks
Of the many things that the Zooniverse produced this year (2010 was a busy one!) a highlight for me were the Zooniverse limericks over on the Galaxy Zoo forum. For Day 17 of the advent calendar I have picked out a few of my favourites. Crowd-sourced and often puntastic.
From DJJ on the influx of spammers in October:
]When spammers invade our vicinity,
Two zooites, the one called Infinity,
The other called Alice
(I won’t say with malice)
Despatch them, and earn zoo divinity.
From Budgieye on an infrared quasar in the SDSS:
From the edge of our space-time, it shrieks
“I’m a quasar”, then Expansion tweaks
its Lyman UV,
redshifted, to be
a whisper of infrared peaks.
From DJJ on Pluto’s demise:
When Tombaugh had managed to scan it,
They christened it Pluto — a planet,
But in twenty-o-six
With their ‘dwarf planet’ fix,
The IAU voted to can it.
From DJJ (again! There a lot of great DJJ limericks) on Galaxy Zoo Hubble vs Zoo 2:
I don’t half miss the SDSS,
Where the edge-ons were sexy, no less;
Here it’s clusters of clumps,
Or hoops with the mumps —
And some edge-ons are simply a mess!
Finally a defence from Zooite Jules, who is often taken for a man thanks to her forum name:
So many have thought me a bloke
In fact it’s become quite a joke
But those who I’ve met
Will vouch for me yet
I’m a LADY. Tis true! Ask these folk!!
There are plenty more on the enormous limericks thread!
A Universe Brimming with Red Dwarfs
This week’s OOTW features Lightbulb500’s OOTD posted on the 4th of December 2010.
This star, with a mass of around half of that of our own star and a temperature many degrees cooler; is a red dwarf. They are the most common stars in the universe, 85% of our galaxy’s stellar population is composed of red dwarfs and it was thought that there was 1×10^23 (or 100 sextillion) in the universe. They are also the longest lived with a lifespan of up to ten trillion years!
The number of red dwarfs in the universe has been recently changed to a much higher number, as Lightbulb500 writes:
[…] New data that confirms the presence of red dwarfs in eight elliptical galaxies between 50,000 and 3 million light years distant. As well as confirming their presence the number of red dwarfs per galaxy has been calculated and reveals that these elliptical galaxies contain 20 times the number of red dwarfs as the Milky Way!
Such a large jump in the number of red dwarfs in elliptical galaxies has necessitated a ‘slight’ revision to the number of stars inhabiting our universe.
The figure has been revised from 100 sextillion or (if I may have an infant moment) 100,000,000,000,000,000,000,000, or 1×10^23 if you like standard form to 300 sextillion – It has been tripled!
Such an increase has other knock on effects – more stars means more ‘normal’ matter so the universe would ‘need’ less dark matter to ‘work’.
It could also have an effect on how dark matter is concentrated around galaxies.
Galaxy Zoo 
