Studying (Analogues to) the Earliest Galaxies
in the Universe
SDSS
Stephanie Greis (University of Warwick), Elizabeth Stanway (University of
Warwick), Luke Davies (The University of Western Australia)
Why
Why Study
Study Distant
Distant Galaxies?
Galaxies?
Galaxies
Galaxies began
began forming
forming about
about 11 billion
billion years
years after
after the
the Big
Big Bang.
Bang. Those
Those early
early galaxies
galaxies are
are thought
thought to
to be
be the
the precursors
precursors of
of
today's
today's elliptical
elliptical galaxies
galaxies and
and spiral
spiral galaxies'
galaxies' central
central bulges.
bulges. They
They are
are also
also thought
thought to
to be
be responsible
responsible for
for making
making the
the Universe
Universe
transparent
transparent through
through the
the heat
heat generated
generated by
by their
their constituent
constituent stars.
stars.
By
Universe
By studying
studying those
those galaxies
galaxies we
we are
are not
not only
only learning
learning about
about the
the history
history and
and evolution
evolution of
of the
the Universe,
Universe,
but also
also about
about the
the origin
origin
Universe but
of
Way
of our
our own
own Milky
Milky Way,
Way,
and therefore
therefore ultimately
ultimately our
our own
own origin.
origin.
Way and
How
How to
to Study
Study the
the Earliest
Earliest Galaxies?
Galaxies?
The
The First
First Galaxies
Galaxies
After
After the
the formation
formation of
of the
the first
first stars
stars when
when the
the Universe
Universe
was
was approximately
approximately 500
500 million
million years
years old,
old, the
the first
first
galaxies
galaxies formed
formed out
out of
of millions
millions of
of them.
them.
Problem:
Problem:
The
The earliest
earliest galaxies
galaxies are
are approximately
approximately 12-13
12-13 billion
billion light
light
years
years away,
away, so
so they
they appear
appear both
both faint
faint and
and small
small –– making
making
itit difficult
difficult to
to study
study their
their light.
light.
NASA and the European Space Agency
These
These massive
massive young
young stars
stars produced
produced enough
enough ultraviolet
ultraviolet
light
light to
to heat
heat the
the interstellar
interstellar and
and intergalactic
intergalactic medium
medium and
and
to
to cause
cause aa change
change in
in its
its state,
state, making
making itit transparent
transparent to
to
almost
almost all
all light.
light. This
This process
process is
is called
called reionisation
reionisation and
and
ended
ended the
the cosmic
cosmic “dark
“dark ages”
ages” that
that went
went before
before it.
it.
Astronomers
Astronomers study
study the
the light
light emitted
emitted by
by the
the stars
stars in
in aa
galaxy
galaxy to
to learn
learn about
about the
the constituents
constituents of
of the
the galaxy:
galaxy:
massive
massive young
young stars
stars produce
produce aa lot
lot of
of UV
UV light,
light, while
while
interstellar
interstellar dust
dust particles
particles emit
emit infrared
infrared light.
light. By
By looking
looking at
at
the
the spectrum
spectrum of
of aa galaxy,
galaxy, these
these properties
properties can
can be
be studied.
studied.
The galaxies in this image are several billion
light years away.
When
When this
this first
first and
and short-lived
short-lived population
population of
of stars
stars died,
died,
the
the resulting
resulting supernovae
supernovae explosions
explosions created
created most
most of
of the
the
heavier
heavier elements
elements which
which make
make up
up humans
humans and
and the
the Earth.
Earth.
Solution:
Solution:
Study
Study galaxies
galaxies which
which are
are more
more nearby
nearby and
and appear
appear
similar
similar to
to the
the earliest
earliest ones,
ones, but
but due
due to
to their
their smaller
smaller
distance
distance from
from us
us they
they appear
appear brighter
brighter and
and larger.
larger.
My
My Research
Research
In
In my
my research
research II compare
compare the
the light
light profiles
profiles observed
observed for
for 22
22 nearby
nearby (up
(up to
to about
about 22 billion
billion light
light years
years away)
away) star-forming
star-forming
galaxies
galaxies with
with models
models of
of stellar
stellar evolution.
evolution. The
The best-fitting
best-fitting model
model can
can tell
tell us
us about
about the
the stellar
stellar population
population in
in the
the galaxy,
galaxy, its
its age
age
and
and mass,
mass, as
as well
well as
as how
how quickly
quickly the
the stars
stars formed
formed and
and how
how much
much dust
dust there
there is.
is.
The
The analogue
analogue galaxies
galaxies are
are found
found to
to be
be less
less massive
massive than
than the
the Milky
Milky Way
Way by
by about
about aa
factor
factor of
of 100-10,000,
100-10,000, and
and range
range in
in age
age between
between 77 million
million and
and 1.5
1.5 billion
billion years.
years.
Their
Their star
star formation
formation rates
rates are
are comparable
comparable to
to those
those of
of the
the earliest
earliest galaxies,
galaxies, forming
forming on
on
the
the order
order of
of 10
10 solar
solar mass
mass stars
stars per
per year.
year.
Future
Future Plans:
Plans:
Further
Further study
study of
of their
their spectrum
spectrum will
will tell
tell us
us about
about the
the chemical
chemical abundance
abundance within
within them,as
them,as
well
well as
as provide
provide another
another measure
measure of
of how
how dusty
dusty they
they are.
are.
Comparison of Model with Observed Spectrum
Obtaining
Obtaining radio
radio data
data for
for them
them should
should confirm
confirm that
that their
their observed
observed brightness
brightness is
is due
due to
to
their
their stars
stars and
and not
not another
another physical
physical process.
process.
For
Forfurther
furtherinformation,
information,please
pleasesee:
see:Stanway
Stanway&&Davies
Davies(2014);
(2014);Stanway,
Stanway,Greis
Greiset
etal.
al.(2014,
(2014,submitted);
submitted);Greis
Greiset
etal.
al.(2014,
(2014,ininprep).;
prep).;
my
website
(http://www2.warwick.ac.uk/fac/sci/physics/research/astro/people/greis/)
on
the
Warwick
Astronomy
and
Astrophysics
Group;
my website (http://www2.warwick.ac.uk/fac/sci/physics/research/astro/people/greis/) on the Warwick Astronomy and Astrophysics Group;
Or
Oremail
emailme
meat:
at:s.m.l.greis@warwick.ac.uk
s.m.l.greis@warwick.ac.uk