The High Redshift Universe
Next Door
Josh Simon
Carnegie Observatories
Things I Work On
Galaxy kinematics
Milky Way satellites and streams
HII regions/chemical
evolution
Supernovae
Dwarf galaxies
Dark
matter
Metal-poor stars
Pop Quiz, Hotshot
1. Is your primary research
(a) observational
(b) theoretical
(c) don’t know
If you answered (b) or (c), please skip to the last
question
Pop Quiz, Hotshot
2. At what wavelengths do you observe?
(a) gamma-ray
(b) X-ray
(c) UV
(d) optical
(e) IR
(f) radio
Pop Quiz, Hotshot
3. Are the objects you observe
(a) pretty close (solar system)
(b) far away (Galactic)
(c) really far away (extragalactic)
(d) really, really far away (cosmological)
Pop Quiz, Hotshot
4. What is your favorite color?
(a) Red.
(b) Orange.
(c) Green.
(d) Blue. No, yellow!
Outline
I. Formation histories of Local Group
dwarfs
a) What were the properties of the first stars and
galaxies?
b) What role did the dwarfs play in the buildup of the
Milky Way halo?
c) What distinguishes dwarfs from globular clusters?
II. Kinematics of dwarf galaxies
a) What is their dark matter content?
b) What is the nature of dark matter?
A Whole New Local Group
• 2011: 27 (!) Milky Way satellite galaxies
– New dwarfs up to 600 times fainter than any
previously known galaxies (Willman et al., Zucker et al., Belokurov et al.)
globular
clusters
tidal stream
new dwarf
Belokurov et al. (2006a)
Why Study Nearby Galaxies?
Oesch et al. (2009)
Belokurov et al. (2006b)
Why Study Nearby Galaxies?
Oesch et al. (2009)
Belokurov et al. (2006b)
1/r2 at z=7: 2  10-59
1/r2 at 100 kpc: 1  10-47
Spectroscopic Surveys of Dwarfs
• Metallicity distribution functions
– Dwarf galaxy evolution and the formation
of the halo
• Chemical abundance patterns as a
function of metallicity
• Search for the most metal-poor stars
– Nucleosynthesis and chemical evolution in
the early universe
Spectroscopic Surveys of Dwarfs
• Gas outflow (and infall)
needed to explain MDFs
• MDFs depend on luminosity
Kirby et al. (2011)
Luminosity-Metallicity Relation
• Faint dwarfs ≠
tidally-stripped
bright dwarfs
• Stars know what
luminosity system
they live in
Progress needed: How do
we match these dwarfs to
subhalos in simulations?
Kirby et al. (2011)
Universal Early Chemical Evolution?
[Mg/Fe]
[Ti/Fe]
[Ca/Fe]
[Cr/Fe]
Collaboration opportunity:
Compare abundance patterns
to high-z Ly-a systems?
MV
MV
MV
MV
MV
MV
MV
=
=
=
=
=
=
=
-20.5
-11.1
-6.6
-6.3
-5.7
-3.9
-3.8
Frebel et al. (2010)
Simon et al. (2010)
Search for the First Stars in
Dwarfs
2000 Stars in Sculptor
2000 Stars in Sculptor
[Fe/H] ~ -3.1
[Fe/H] = -3.8
[Fe/H] ~ -3.8
[Fe/H] ~ -3.6
A star?
M dwarf?
The Nature of Dark Matter
• The missing satellite problem
?
Belokurov et al. (2006a)
Springel et al. (2001)
Progress needed:
(1) More/deeper searches for dwarfs
(2) Larger spectroscopic surveys of kinematics
(3) Understanding observation-simulation comparison
The Nature of Dark Matter
• Indirect detection of dark matter
Fermi Space Telescope
Ursa Minor
Segue 1
Strigari et al. (2008)
Martinez et al. (2009)
Simon et al. (2010)
The Nature of Dark Matter
• The density profiles of dark matter
halos
1
2
cusp/core
Radial velocities only
Strigari et al. (2007)
Jeans equation:
2)
GM(r)
d(

2

r
r
=
—

—
2(r)



r
dr
r
The Nature of Dark Matter
• The density profiles of dark matter
halos
1
2
cusp/core
GMT/TMT
Radial velocities
proper only
motions
Strigari et al. (2007)
Jeans equation:
2)
GM(r)
d(

2

r
r
=
—

—
2(r)



r
dr
r
Other Projects
• How are heavy elements distributed
through galaxies?
• What are the progenitors of Type Ia
SNe?
• What is the effect of a low-metallicity
environment on star formation and gas
tracers?
Opportunities for Collaboration
• Observational: stellar kinematics of
Local Group dwarfs
• Theoretical: understanding the
matching between real dwarfs and
simulated subhalos
• Theoretical: predictions for observable
effects of dark subhalos on tidal
streams
New Opportunity for Students
http://obs.carnegiescience.edu/gradfellowships
Summary
• Local Group dwarfs are unique laboratories for
 Dark matter - missing satellites, indirect detection, dark
matter density profiles
 Early galaxy formation – first stars, chemical evolution
• Come talk to me about:




Comparisons between observations and N-body simulations
Spectroscopic surveys in the Local Group
Observational tests of dark matter models
Predicted properties of first stars and SNe