The 2013 Beatrice Hill Tinsley Lecture

Dr. Karen MastersUniversity of Portsmouth, UK

A Zoo of GALAXIES

Our galaxy

120 thousand light years

Artist ImpressionCredit: NASAYou are hereEdge-on spiral

NGC 4565 (NOAO)

The Spiral Nebulae

The Andromeda Galaxy

William Herschel c1800

What are these spiral nebula?

Red

Massive

In clusters

Blue

Less massive

Not in clusters

10 m

illion

yea

rs

100

billio

n ye

ars

100

milli

on y

ears

10 b

illion

yea

rs

Galaxies are made of stars

The Colours of Galaxies

Beatrice Tinsley (1941-1981)

Only old stars

Still forming stars

How Many Galaxies Are There?

192924

Distance ->

Vel

ocity

->

How Many Galaxies Are There?

19861,110

20081 million

Sloan Digital Sky Survey (2012)

Colour Magnitude Diagram

Mass (Luminosity/magnitude)

Blu

erR

edde

r

CO

LOU

R

Bigger/brighterSmaller/dimmer

Red sequence – ellipticals

Blue cloud

– spiral galaxies

Mass division

Green valley (very sparse)

Big DataRed sequence - ellipticals

Blue cloud - spirals

How to look at a million galaxies – ask for help!

Big DataRed spirals!

Blu

e el

liptic

als!

Elliptical

galaxies

Spiral galaxies

Red Spirals

Bamford et al. 2009; Skibba et al. 2009Masters et al. 2010a,b

Some galaxies appear to be

crashing into each other.

High Velocity Clouds and the Milky Way Credit: B. Wakker et al. and NASA

Galaxy Zoo 2

Take the brightest ¼ million galaxies and ask more detailed questions (Feb 2009-April 2010)

Red Spirals have more

bars

Do bars kill galaxies?Blue = bars rare

Red = bars more common

Blue Red

Masters et al. 2011 MNRAS

More bars where there’s less gas

0.01 0.1 1.0 10.0Gas fraction (MHI/M★)

Masters et al. 2012 MNRAS

Atomic HI (Walter et al. 2008)

Optical from SDSS (DR8)

Molecular H2 (Helfer et al. 2003)

The bar and gas in Messier 95

What’s next for the Zoo?

Galaxy Zoo is Popular

Why Do People Do This?

Galaxy Zoo: Exploring the Motivations of Citizen Scientists. (Raddick et al. 2009 astroph/0909.2925)

.org

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

Credit: Alice Sheppard