Date:
Tue, 01/12/201512:30-13:30
Location:
Kaplun building, Room No. 200
Lecturer: Dr. Santi Roca
Affiliation: Racah Institute of Physics,
The Hebrew University of Jerusalem
Abstract:
Simulations have shown to be one of the best
tools to study properties of galactic large scale
structures and their effects on the local
kinematics of stars. In this thesis, using high
resolution simulations obtained with different
codes and initial condition techniques, we
have observed two different behaviors for the
rotation frequency of transient spiral arms like
structures. Whereas unbarred disks present
spiral arms nearly corotating with disk
particles, strong barred models (bulged or
bulge-less) quickly develop a bar-spiral
structure dominant in density, with a pattern
speed almost constant in radius (Roca-
Fàbrega et al. 2013). Preliminary results also
indicate that particles in barred models move
inside the spiral structures.
A second result we present in the thesis is
that the sign of the kinematic parameter
known as vertex deviation (lv) can be used to
trace resonance radius of non-axisymmetric
structures. This parameter changes its sign
from negative to positive when crossing the
spiral arms toward disk rotation, in regions
where the spiral arms are in between
corotation (CR) and the Outer Lindblad
Resonance (OLR). By contrast, when the arm
sections are inside the CR and outside the
OLR, lv changes from negative to positive
(Roca-Fàbrega et al. 2014).
Finally we present a new cosmological Milky
Way sized galaxy simulation that includes
both the collisionless N-body and also the gas
components. The system has been evolved
inside a 28 Mpc cosmological box with a
spatial resolution of 109 pc. At z=0 the system
has an Mvir = 7.33•10^11 Msun. We have
observed how a well-defined disk is formed
inside the dark matter halo and the overall
amount of gas and stars is comparable with
MW observations. Several non-axisymmetric
structures arise out of the disk: spirals, bars
and also a warp. We have also observed that a
huge reservoir of hot gas is present at large
distances from the disk, embedded in the dark
matter halo region, accounting for a fraction
of the "missing baryons". Gas column density,
emission (EM) and dispersion (DM) measure
have been computed from inside the
simulated disk at a position of 8 kpc from the
center and in several different directions. Our
preliminary results reveal that the distribution
of hot gas is non-isotropic according with
observations Gupta et al. 2012 and Gupta et
al. 2013. Also its metallic content presents a
clear bimodality what is a consequence of a
recent accretion of a satellite galaxy. After a
careful analysis we confirm that due to the
anisotropy in the gas distribution more than
50 random observations of different sky
regions are needed to recover the real
distribution of hot gas in the galactic halo with
a relative error lower than 5% (Roca-Fàbrega
et al. 2015 in preparation).
Additional details of the upcoming Astrophysics'
seminars can be found on the following link.
האירוע הזה כולל שיחת וידאו ב-Google Hangouts.
הצטרף: https://hangouts.google.com/hangouts/_/mail.huji.ac.il/astrophysics?hceid=bWFpbC5odWppLmFjLmlsX2c0czhydDlpcmhwZzRvdGNybWIzZGFqcjdvQGdyb3VwLmNhbGVuZGFyLmdvb2dsZS5jb20.7tbmqakutjolvb6vgd2p6bvrl0&hs=121