Just a quick post to say thank you for your contributions to Brand New Mens Air Foamposite One 314996-007 Black/Metallic Copper Size 8.5 in the last couple of weeks. I’m delighted to say that the bar drawing task is now completed. We still have a lot of spirals to draw though, so if you are ready for a challenge come join us in drawing these beautiful structures. Remember we collect 15 answers per galaxy, and use clever algorithms to combine them into a really reliable answer – so do your best, but don’t get too worried if your hand slips slightly! 🙂
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I’m posting this on behalf of Amelia Frasier-McKelvie, a postdoc at the University of Nottingham, UK.
Hi – I’m Amelia, and I’m a postdoctoral researcher at the University of Nottingham. I work on galaxy evolution using the Nike Zoom All Out Low 878670 107 Sportschuhe Gr. US 10.5 - (and yes, I know it’s a contrived acronym!) MaNGA aims to observe 10,000 galaxies using integral field spectroscopy, which means instead of just obtaining one spectrum of a galaxy, we take several hundred at all different points across a galaxy. From this, we can infer interesting spatial information on galaxy properties. For example, we can see the regions in which star formation is occurring, or compare the ages of the stars in the bulge regions of a galaxy to the outer disk. By breaking down a galaxy into its components (such as bulge, disk, spiral arms, and bar) we can discover more about how the galaxy formed, and how it has led its life so far.
I’m really interested in how bars affect their host galaxies. In particular, I’m looking for observational evidence that bars are involved in the quenching of star formation within a galaxy. This phenomenon is known as secular evolution/quenching. The one thing a galaxy needs to form stars is a reservoir of cool hydrogen gas. It’s been postulated that a bar can transfer matter (such as gas) radially inwards through a galaxy’s disk and into its central regions. If this is the case, then maybe it takes this gas required for star formation and funnels it towards the galactic centre, starving the disk, and ceasing star formation. Simultaneously, this gas that is funnelled into the central regions could either induce a final starburst, using up all gas, or feed an active galactic nucleus (AGN), which can heat the gas to a point where it cannot collapse to form stars.
If we wanted to catch a bar in the act of quenching a galaxy, we could look for tell-tale signs of this funnelling action, namely a difference in the age and chemical composition of the stellar populations in the bar region of a galaxy when compared to the disk.
This is where NIKE AIR MAX PLUS TN1 Tuned HERREN SCHUHE dunkelgrau / Volt comes in — I need to know where the bars actually lie in their host galaxies! Galaxy Zoo 3D citizen scientists mark out the bar (and spiral arm) regions of the MaNGA galaxy sample, which I can apply to our data cubes and extract spectra belonging to the galactic bar and disk regions. I can then analyse the bar and disk spectra separately and compare their properties. I’m interested in the global properties of a large sample of galaxies, so I need as many bar and disk region classifications as possible!
If I can find observational evidence that bars are helping to quench galaxies this will confirm the idea that internal secular evolutionary processes are important in galaxy evolution.
This will prove that along with external factors, internal structures such as bars are extremely important in determining a galaxy’s fate!
We hope you enjoyed hearing about how the masks made in Galaxy Zoo: 3D are being used. There’s still plenty of bars and lots and lots of spirals to mark in the project, so please join in if you’d like to help us complete our sample and help Amelia and others (including me!) with their research.
This is a guest post by Freya Pentz, who has spent much of this summer doing research with Galaxy Zoo.
Hi Galaxy Zoo volunteers!
I’m a summer student at the Zooniverse. I’m at university studying natural sciences about to go into my second year and for the past 5 weeks I’ve been working at the Zooniverse office here in Oxford. I wanted to let you know what I’ve been doing during that time.
I’ve been using data from the Galaxy Zoo: Bar Lengths project, writing code to process the information and making sure it looks sensible. Before I started working at the Zooniverse, I had done very little computing so I had to learn a lot! For those of you who are interested, I’ve been using python to extract the measurements you did on the galaxies and plotting graphs with all the data. Learning how to use python was like learning another language but it was definitely worth it.
The first thing I did was to find out how many of the galaxies that you’ve classified have bars. That meant looking at the answers to the first question about the galaxy in the Bar Lengths project ‘Does this galaxy have a bar’ and seeing for each galaxy if most people answered ‘Yes’ or if most people answered ‘No’.
Luckily, the code could do that for me; otherwise I would have had to look at over 66000 answers! So far, 4960 galaxies have been classified out of a total of 8612 in the project. Your classifications show that 700 of these have a bar, meaning that the fraction of classified galaxies with a bar is around 14%. This is similar to the 10% bar fraction referred to in the study recently done by the Galaxy Zoo and CANDELS teams on bar fractions out to z=2 (Mens NIKE LEBRON13 Low USA COSTAL BLUE/WHITE BRGHT CRMSN SIZE 9.5 **NEW** & Mens Nike Special Field SF AF1 QS Dust Grey 903270-001 Size 10). This number will probably change a little bit as more galaxies get classified, but it’s good that it is similar to known values so far.
The next thing was of course to find the lengths and widths of the bars. When you draw lines on the galaxy to mark the length and width, the database records this as coordinates. Each line has four coordinates, 2 x coordinates and 2 y coordinates. Once you have the coordinates, it’s fairly simple to turn them into lengths. All you need is some Pythagoras. When plotting a histogram of the lengths, the shape was a Gaussian distribution, or a bell curve. This shows that most of the galaxies have lengths between certain limits (5-15 kpc) and then as you go beyond these limits, the number of galaxies decreases.
During my time here, I found some interesting galaxies. When I first looked at the redshifts, there was a galaxy with a redshift of 4.25. I mentioned this to a couple of people on the Zooniverse team and they all said there wouldn’t be a galaxy with such a high redshift in the sample. I checked it out and this is the galaxy in question:
You can see that there is a bright blue smudge in the top left of the galaxy. When I first saw this, I thought it was a lens. It looks like one, and you can just see a small bit of blue on the other side of the galaxy’s core, suggesting a lens even more. According to the experts in the Zooniverse however, this is probably not a lens, as the galaxy does not look massive enough to lens light. Also, the blue curve is well inside the galaxy, instead of being around the outside. Usually, all the mass of the galaxy is needed to lens an object so the light would appear around the edge. The blue curve is most likely an unusual feature of the galaxy itself, which can explain why the reported redshift is so high. The redshift for this galaxy was measured photometrically. This is where astronomers use galaxy colours across a wide range of wavelengths to predict the likely redshift. This method of measuring redshift is much more prone to error than spectrometry (where the absorption lines for certain elements in a galaxy are observed and the shift of these lines is measured) so the blue smudge could have easily made the telescope think the redshift was higher than it is. This redshift is therefore almost definitely a mistake. We also know this from the high resolution of the image. You normally wouldn’t be able to see a galaxy with even a redshift of 1 this well!
The reason telescopes have to use photometric redshifts sometimes even though they are often wrong is that there is not enough time to take a spectrum of every galaxy when you are conducting a large survey of the sky. Telescope time is expensive and photometric measurements allow you to get a bit of information about lots of galaxies which can sometimes be more useful that getting a lot of information about a few.
When running into problems like this it was really useful to be able to look at a picture of the galaxy on the Galaxy Zoo: Bar Lengths website. Looking at the galaxies and seeing in real life what the data on the graphs was telling me was probably my favourite part of my time at the Zooniverse. It’s so amazing that thanks to the Sloan Digital Sky Survey, the Hubble Space Telescope projects and other mass surveys of the universe, we can actually look at pictures of thousands of galaxies easily.
The Zooniverse is such a cool organisation and I’m lucky to have worked for them this summer. The great thing about them is that you can get involved too! I know from my work with Bar Lengths that even if a few people log on and classify in any of the projects, it can be really helpful. None of the science can be done without you providing the data.
Or have a look at some of the other projects here:
We are pleased to announce that a Galaxy Zoo project is one of the first projects built on the new Zooniverse! Several years ago we measured the lengths of galactic bars in relatively nearby galaxies in the Sloan Digital Sky Survey, and Ben Hoyle wrote an excellent paper presenting new an interesting results on how bars, which are a distinct feature caused by a change in the nature of the orbits of some of the stars in a galaxy, relate to other physical properties of the galaxy, such as color (indicative of recent star formation) and the nature of spiral arms or rings. That work showed the power of measurements like these, which are not always easy for computers to get right.
Today, we’re hoping you’ll help us extend that set of detailed galaxy measurements into the distant Universe, with measurements of bars in about 8,000 galaxies from our previous projects using Hubble Space Telescope data, including the AEGIS, CANDELS, COSMOS, GEMS and GOODS surveys.
We’ve deliberately been pretty broad in our selection of galaxies which may have a bar, so the first thing the project asks you is to confirm whether you think the galaxy does indeed have one. There are many examples of barred and not-barred galaxies (including examples of sort-of-looks-like-barred-but-actually-isn’t-and-here’s-why) included in the project, and you can access them anytime by clicking the “NIKE KYRIE 4 MADNESS MARCH MEN'S BASKETBALL SHOE 943806104” button.
If the galaxy doesn’t have a bar, then you can move on to the next one. If it does, there are some follow-up questions about spiral arms and rings, and then we ask you to draw 2 lines on the image: one for the bar width and one for its length.
You can also join in the discussions after the classifications with our new Talk discussion tool, which is completely separate from the main Galaxy Zoo Talk (just like the rest of the project).
On a more personal note, this is a big step forward for the Zooniverse as a whole. The first draft version of this project came together in under 1 hour back in April. Afterward, we shared project links between science team members and iterated back and forth on the right questions to ask and the right data to use. This process would normally take at least 6 months and require a lot of one-on-one time with a Zooniverse developer. Instead, because the Zooniverse development team has done a brilliant job creating a Project Builder that’s flexible, powerful and also easy to use, we were able to create a new project in a way that’s analogous to, well, creating a blog.
In these early days of the new site’s release I’m sure there will be some bugs that need zapping, but even so the new capabilities of the Zooniverse are phenomenal. I suspect this is just the first of many new projects to be spun up in the New Zooniverse. (In fact, there are Nike Air Max 95 Essential Mens 749766-108 Obsidian Sand Coral Shoes Size 9)
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A new paper using Galaxy Zoo 2 bar classification has recently been accepted!
In this paper (which can be found here: http://arxiv.org/abs/1505.02802), we use hundreds of SDSS spectra to study the types of stars, i.e., stellar populations, that make up barred and unbarred galaxies. The reason for this study is that simulations predict that bars should affect the stellar populations of their host galaxies. And while there have been numerous studies that have addressed this issue, there still is no consensus.
A graphic summary of this study is shown here:
In this study, we stack hundreds of quiescent, i.e., non-star-forming, barred and unbarred galaxies in bins of redshift and stellar mass to produce extremely high-quality spectra. The center-left panel shows our parent sample in grey, and the cyan and green hash marks represent our galaxy selection for our bulge and gradient analysis. The black rectangle represents one of the bins we use. The upper and lower plots show the resultant stacked spectra of the barred and unbarred galaxies, respectively. We show images of barred and unbarred galaxies in the center, selected with the Galaxy Zoo 2 classifications. Finally, the center-right panel shows the ratio of these two stacked spectra at several wavelengths that reflect certain stellar population parameters.
Our main result is shown here:
We plot several stellar population parameters as a function of stellar mass for barred and unbarred galaxies. Specifically, we plot the stellar age, which gives us an idea of the average age of a galaxy’s stars, stellar metallicity ([Fe/H]), which gives us an idea of the relative amount of elements heavier than hydrogen in a galaxy, alpha-abundance ([Mg/Fe]), which gives us an idea of the timescale it took to form a galaxy’s stars, and nitrogen abundance ([N/Fe]), which also gives us an idea of the timescale it took to form a galaxy’s stars.
The main result of our study is that there are no statistically significant differences in the stellar populations of quiescent barred and unbarred galaxies. Our results suggest that bars are not a strong influence on the chemical evolution of quiescent galaxies, which seems to be at odds with the predictions.