1. Unveiling the inner structure of galaxies
www.dagalnetwork.eu@DAGAL_EU DAGALaxies
IamFrancescaIannuzzi,apostdocatworkingwithintheInitialTrainingNetworkDAGAL
TheprojectjoinseightEuropeaninstitutionsandisfundedbytheFP7‘sPeopleProgramme
We know everything of a simulated galaxy
We know one projection of a real galaxy...
2D positions of stars on the sky (projected morphology)
1D stellar velocities along the line of sight (from spectral lines)
...But the velocity behaviour of the stars
can give us hints on its invisible structure
Number of photons or
“Surface Brightness”
Asymmetric deviation from a Gaussian
Symmetric deviation
from a Gaussian
Mean velocity
Velocity dispersion
The Line-Of-Sight Velocity Distribution (LOSVD)
The LOSVD contains all the accessible information at
each point in an observed galaxy
It is commonly described by five quantities:
surface brightness and four velocity-related properties
Numerical simulations help us capture the effect of
specific structural features on the observed velocity
We can mimic the observational procedure on a simulated galaxy and
thereby extract the five aforementioned observables for a given viewing
angle. We know the full morphology of the simulated object. This allows us to
identify the structures responsible for different velocity behaviours in the stars
“ ”
Through the comparison between
simulated results and real observations
we can peer into the hidden dimension
My current work is aimed at understanding the effect of
the presence of structures like stellar bars and classical/
peanut bulges on the kinematic behaviour of a disk
galaxy like our Milky Way. Depending on the orientation
of the disk, some of these structures may be hidden or
deformed in appearance and cannot be identified
morphologically. The study of the line-of-sight kinematics
of stars in the presence of these structure provides the
only possible way to identify their presence in the galaxy
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Spiral structure
Stellar bar
Central bulge(s)
line-of-sightobservationalresults
chosenviewpointmimicobservations
3D positions of stars (full morphology)
3D stellar velocities
Simulated galaxy Real galaxy