M101 – the Wonder Galaxy

Karl D. Gordon, STScI, 29 Jan 2009, IYA09

Why M101

M101 = Pinwheel Galaxy

Large, bright, and face-on

Apparent size is >0.5 degrees

2x larger than the Milky Way

Not inclined

Lots of star formation

Very weak bulge

Large metallicity gradient

Strong change in metals (> He) with radius

Optical

StarsYoung (blue)Old (red)

GasEmission lines(not shown)

Dust (obscuration)

Infrared

StarsOld (blue)

DustAromatics(Organics)(green)

Hot DustStar formation(red)

X-ray

Point-sourcesX-ray binaries(black holes/ neutron stars)Supernovae remnants

Extended EmissionStellar clustersHot gas

Other Views of M101

Very popular galaxy

Observed with other NASA space mission

And ground based observatories

A clear view of star formation from:

GALEX – ultraviolet

Radio – 21cm HI line

Spitzer - infrared

Ultraviolet

Hot Young Stars(unobscured)

Dust (obscuration)Dust scattered light

GALEX far-UV (0.15 micron)

Infrared

Hot Young Stars(obscured)

Hot Dust Emission

Spitzer/MIPS (24 micron)

Radio

21cm emission lineAtomic hydrogenFuel for stars

Ground-basedVery Large Array

Star Formation

Fuel (green)Unobscured (blue)Obscured (red)