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The 2013 Beatrice Tinsley Lecture: A Zoo of Galaxies
- 1. The 2013 Beatrice Hill Tinsley Lecture
- 2. Dr. Karen Masters University of Portsmouth, UK A Zoo of GALAXIES
- 5. Our galaxy
- 7. 120 thousand light years Artist Impression Credit: NASA You are hereEdge-on spiral NGC 4565 (NOAO)
- 12. What are these spiral nebula?
- 14. Red Massive In clusters Blue Less massive Not in clusters
- 15. Galaxies are made of stars
- 16. The Colours of Galaxies Beatrice Tinsley (1941- 1981)
- 17. Only old stars Still forming stars
- 18. How Many Galaxies Are There? 1929 24Distance -> Velocity->
- 19. How Many Galaxies Are There? 1986 1,110
- 20. 2008 1 million
- 21. Sloan Digital Sky Survey (2012)
- 22. Colour Magnitude Diagram Mass (Luminosity/magnitude) BluerRedder COLOUR Bigger/brighterSmaller/dimmer Mass division
- 23. Big Data
- 24. How to look at a million galaxies – ask for help!
- 29. Big Data
- 30. Red Spirals Bamford et al. 2009; Skibba et al. 2009 Masters et al. 2010a,b
- 31. Some galaxies appear to be crashing into each other.
- 32. High Velocity Clouds and the Milky Way Credit: B. Wakker et al. and NASA
- 36. Galaxy Zoo 2 Take the brightest ¼ million galaxies and ask more detailed questions (Feb 2009-April 2010)
- 37. Red Spirals have more bars Do bars kill galaxies?Blue = bars rare Red = bars more common Blue Red Masters et al. 2011 MNRAS
- 39. More bars where there’s less gas 0.01 0.1 1.0 10.0 Gas fraction (MHI/M★) Masters et al. 2012 MNRAS
- 40. Atomic HI (Walter et al. 2008) Optical from SDSS (DR8) Molecular H2 (Helfer et al. 2003) The bar and gas in Messier 95
- 41. What’s next for the Zoo?
- 42. Galaxy Zoo is Popular
- 43. Why Do People Do This? Galaxy Zoo: Exploring the Motivations of Citizen Scientists. (Raddick et al. 2009 astroph/0909.2925)
- 45. .org
- 46. Six years of Galaxy Zoo • July 2007-Feb 2009 • Original Galaxy Zoo (spiral vs elliptical, SDSS) • Feb 2009-April 2010 • Galaxy Zoo 2 (detailed morphology, SDSS) • Zooniverse launch (Dec) • April 2010 – Aug 2012 • Galaxy Zoo: Hubble • Aug 2012 - ? • Galaxy Zoo relaunched (more Hubble, more SDSS) • Aug 2013 - ? • Galaxy Zoo: Quench launched
Editor's Notes
- To say our understanding of the “zoo” of galaxies that can be found in the universe has changed a lot over the last century or two is a bit of an understatement. This the Whirlpool galaxy as drawn by Lord Rosse in 1854 looking through what at the time was the largest telescope in the world (in Ireland)And here’s one of the most modern views of this galaxy using the Hubble Space Telescope.
- To say our understanding of the “zoo” of galaxies that can be found in the universe has changed a lot over the last century or two is a bit of an understatement. This the Whirlpool galaxy as drawn by Lord Rosse in 1854 looking through what at the time was the largest telescope in the world (in Ireland)And here’s one of the most modern views of this galaxy using the Hubble Space Telescope.
- This is William Herschel’s map of the galaxy which he published in 1785 (from star counts). He clearly understood the galaxy as a collection of stars, and while he got a lot wrong (Sun at centre, ~7000 light years across) it’s the first example of such a map.
- By 1900 astronomers understood quite a lot about the basic structure of our galaxy – like in this map by Cornelius Easton which shows spiral structures (although the Sun is still in the centre, and it’s still too small). Easton used models of other spiral galaxies he saw in the sky to suggest the Milky Way might have this structure.
- Already in the 19th century, telescopes had been turned on the sky for over 200 years and we had a lot of examples of similar objects viewed from the outside. I already showed you Lord Rosse’s drawing of the Whirlpool galaxy. Whirlpool Galaxy (Messier 51), by Lord Rosse (1845)
- Here’s another example of a nearby galaxy, with a drawing from Charles Messier in 1807 next to a modern image from the Sloan Digital Sky Survey. This is what a disc galaxy will look like viewed almost edge on. Andromeda Galaxy (Messier 31) by Charles Messier (1807)
- And here’s a selection of galaxies drawn by William Herschel around beginning of the 19th century(add modern equivalents).
- Not all galaxies are spiral or disc galaxies. This beautiful picture of the central regions of the nearby Virgo cluster of galaxies shows examples of several large, smooth (or ellitptical) galaxies, as well as many other members of the Virgo cluster. Virgo Cluster Galaxies Image Credit & Copyright: Rogelio Bernal Andreo
- The variety of different galaxies in the sky caused people to wonder what they are – culminating in the famous great debate between Curtis and Shapley.Curtis – MW small, sun centre, other galaxiesShapley – MW very large, sun to side, spirals are gas clouds in it. One way to understand something better is to classify it, make categories etc.
- Probably the most famous of the early classifiers of galaxies was Edwin Hubble. Edwin Hubble looked at Images of Hundreds of galaxies in the 1920s and developed a classification scheme that we still use today.
- Galaxies are made of stars. For the most part, the colour of a galaxy tells the colour of the stars in the galaxy. When stars form, they form in a variety of masses. The most massive stars are extremely bright, and hot and so they look blue/white (in the same way very hot metal glows blue/white). They also live for very short times (astronomically). Just a few 100 million years. When they are around in a galaxy the galaxy will look blue because they totally outshine everything else. After a time all the massive hot blue stars will die, and all that is left in a galaxy will be the less massive, cooler, red stars. So a galaxy which hasn’t made new stars for while (more than a few 100 million years) will look red.
- 1000s of morphology, but for physical properties need distance too – redshift. 1929: Edwin Hubble discovers expansion of the Universe (24 galaxies)
- 1986: CfA redshift survey - discovery of large scale structure (1100 galaxies; Huchra & Geller57 yearsx 50
- 2008: Final release of SDSS Main Galaxy Sample (1 million galaxies)22 yearsx 1000
- The SDSS has a catalogue of million galaxies over 25% of the sky which has been used to revolutionise our understanding of the zoo of galaxies,
- Here it is with real data – the 1 million galaxies in the Sloan Digital Sky Survey Main Galaxy Sample.What was missing was morphology (or type) for more than a few thousand objects. It seemed impossible to do that to astronomers in the early part of the 21st century. But without this information they didn’t have the full picture.
- This one illustrates the 50-50 type classifications (or it did at HAG talk).
- Galaxy Zoo was popular so gave us lots of morphologies. And we found some interesting stuff.
- direct probe of evolution affecting star formation but not morphology route for most evolution from blue -> red (Bundy et al. 2010; COSMOS) huge samples - thanks to SDSS and Galaxy Zoo
- gas in the disk of spirals will run out in much less than a Hubble time (~2 Gyr) must be replenished from somewhere (Larson, Tinsley & Caldwell 1980) hot gas in halo continuous infall of gasshut off gas supply (remove it or make it too hot)red spiral
- Between 1 third and 2/3rds of massive spirals host bars (depending on how strict you are on the definition, and slightly on wavelength)
- Galaxies have all sorts of internal structuresNumber of spiral armsRingsDust lanesAnd bars….
- Work published in MNRAS in 2011 (Masters et al. 2011, MNRAS (411, 2026)“Galaxy Zoo: Bars in disk galaxies”)(~14000 galaxies in volume limited sample with reliable answer to bar question)Red, massive disk galaxies are much more likely to have bars than blue ones…Also see: Nair & Abraham (2010)
- We wanted to investigate role of gas in what a bar does to a galaxy – so we use the Arecibo telescope to do this. Hydrogen emits a characteristic spectral line at 21cm detectable by Arecibo, so we have neutral hydrogen content of about 25% of the Galaxy Zoo sample.
- What we did find is that there are more bars where there’s less gas, and this image might help explain why. This is ongoing work.
- Interesting about motivations – people like science.
- Words in abstracts of galaxy Zoo science papers
- Potential for seredipity – new images – you could find the next Voorwerp.
- From Alice
- Come and play in our ‘Xing (1) Xi (4) Zong (3) Dong (4) Yuan (2)’