Download Sagittarius Dwarf Elliptical Galaxy

Planets in other
Galaxies
Most planets we know of are within 0.5 kpc of
the sun but our galaxy has a radius > 25 kpc
Is our sun special?
Most search programs for extrasolar planets
concentrate on solar-like stars in the solar
neighbourhood but is our sun special?
The two most atypical properties of the Sun are
its mass and orbit around the galaxy. The Sun
is more massive than 95%+/-2% of nearby
stars, and its orbit around the Galaxy is less
eccentric than 93%+/-1% of FGK stars within
40 pc.
Mass of the stars in the solar
neighbourhood
Initial mass function
(USco)
Rotation velocity of the stars (v sini),
The sun rotates more slowly than 83+/7% of the stars (mass range 0.9-1.1
Msun) in the solar neighbourhood.
Ages of the stars in the solar neighbourhood
Mean stellar galactocentric radius
distribution
Sun orbits at
7.62 +/-0.32 kpc
The co-rotation
radius is at
3.4 +/-0.3 kpc
Eccentricity of the orbit of the sun
Intermezzo I:
The rotation of spiral galaxies
As the name indicates spiral
galaxies have spiral arms. Spiral
arms are the sites of star formation. We
see the better well in the blue, because
of the young luminous OB stars
inhabiting them.
Spiral galaxies are found in low-density
regions of the universe.
Why do the spiral arms not wind up?
Lindblad: star formation caused by density waves of stars.
Star formation in spiral arms
Gas clouds are swept up by spiral arms
(clouds move into regions of enhanced
density of stars)
This increases density of matter in
clouds and may even results in cloudcloud collisions. The high density makes
the collapse of clouds more likely which
triggers star-formation.
M51: Herschel (70, 100, 150 mu), Optical
Intermezzo II:
The formation of galaxies
(bottom up process)
Grows of primordial fluctuations (universe
contains dark energy, dark matter, hydrogen,
helium)
As universe cools dark matter condenses
Gas flows into denser regions. Dark matter
stays in outer regions because it can only
interact gravitationally.
 Small proto-galaxies form
Galaxies grew by accreting smaller galxies
Universe at 0.47, 2.1 and
13.4 Gyrs (simulation,
box size 90 Mpc)
As a galaxy gains mass by accreting smaller
galaxies the dark matter stays mostly on the
outer parts. This is because the dark matter
can only interact gravitationally, and thus will
not dissipate.
The gas however can quickly contract, and as
it does so it rotates faster, until the final result
is a very thin, very rapidly rotating disk. It is
currently not known what process stops the
contraction, in fact theories of disk galaxy
formation are not yet successful at producing
the rotation speed and size of disk galaxies
(possibly AGN activity, star-formation, or the
gravitation pull of the dark matter stops it).
Galaxy formation
The role of mergers
 In recent years, a great deal of focus has been put
on understanding merger events in the evolution of
galaxies. Our own galaxy has a tiny satellite galaxy
(the Sagittarius Dwarf Elliptical Galaxy) which is
currently gradually being ripped up and "eaten" by
the Milky Way, it is thought these kinds of events
may be quite common in the evolution of large
galaxies.
Large
Mergers
Mass of the host galaxy: Milky way is more
massive than 99% of all galaxies!
A famous neighbour: the Large Magellanic Cloud
 distance 48.5 kpc;
 size 10.75x9.17
degrees
 Mass of the LMC:
6 109 Msun
 Mass of the
milky way:
5.8 1011 Msun
Sagittarius Dwarf Elliptical
Galaxy
 The Sagittarius dwarf galaxy is orbiting our galaxy
at almost a right angle to the disk. It is currently
passing through the disk; stars are being stripped
off of it with each pass and joining the halo of our
galaxy. There are other examples of these minor
accretion events, and it is likely a continual process
for many galaxies. Such mergers provide "new"
gas, stars and dark matter to galaxies. Evidence for
this process is often observable as warps or
streams coming out of galaxies.
Sagittarius dwarf elliptical galaxy I
The Sagittarius dwarf elliptical galaxy
gets tidally disrupted!
M54 is the core of the Sagittarius dwarf
elliptical galaxy!
The density of stars in the
Sagittarius dwarf elliptical galaxy
is quite low
Do not mix it up with the Sagittarius dwarf
irregular galaxy!
We can only search for planets of giant stars!
Is the sun metal rich?
Do planets form preferentially around
metal rich stars?
RV planets
Planets with transits
Formation of planets in the
core-accretion scenario:
heavy elements needed to
form core
Abundance of stars in the SDSG
RV-accuracy that can be achieved
RV-measurements of a giant star with a planet
Oscillations of a giant star
M/R and L/M relation
Determine the mass of the host star by
using the oscillations
Another problem: spots can cause
RV-variations
V = –Vrot
V = +Vrot
V=0
Activity of the star can be monitored in
CaIIH and K:
Sunspots in white light and in CaIIH and K
Ca II line
Strong absorption lines are formed higher up in the stellar atmosphere. The core
of the lines are formed even higher up (wings are formed deeper). Ca II is formed
very high up in the atmospheres of solar type stars.
Activity can also be monitored in X-rays:
The Sun in X-rays
The amplitude of the RV-variations of a
sunspot is larger in the optical then in the IR
The next step:
E-ELT
Adaptive Optics
Fried Parameter r0
 : Zenit Distanz
Da der Brechungsindex eine Funktion der Höhe in der Atmosphäre
ist, führt man den Parameter Cn ein.
Cn : Strukturkonstante der Variationen des Brechungsindex
integriert über die turbulenten Schichten.
r0 ( , )  0.185
6/5
6/5
  
r( )    r0
0 
cos
3/5

 C (d)dh
2
n
Die Aberration der Phase lässt sich als Summe
orthogonaler Pylonome (Zernicke Polynome) (in
Polarkoordinaten r,q) darstellen.

 (r, )   a j Z j (r, )
0
Shack Hartmann Sensor
OPTIMOS EVE
Konzept eines Spektrographen
Auflösung:
R  2(d /D)tan  Blaze
Die Bildelemente des Detektors müssen klein genug
sein, um diese feinen Details auch aufzulösen (bzw.
die Brennweite der Kamera lang genug):

focallengthcamera
c /  CCD
tan  Blaze
pixelsize
Zentralwellenlänge ( n+1) in der n+1 ten Ordnung ist
gegeben durch n/(n+1)n

Spectrograph with two channels:
optical and IR