|
|
Extragalactic Astrophysics &
Observational Cosmology Group
|
|
| Martin Bernet |
Postal Address:
ETH Zurich
Institute of Astronomy
HIT J22.3
Wolfgang-Pauli-Strasse 27
8093 Zürich
SWITZERLAND
Phone: ++41 (0)44 633-6466
Fax: ++41 (0)44 633-1238
email: mbernet@phys.ethz.ch
|
| Curriculum
Vitae |
Education:
|
Employment:
2006 -
|
PhD Student, Institute of Astronomy, ETH Zurich
|
|
| Research
Interests |
I'm working with Prof. Simon Lilly and Francesco Miniati on a project about cosmic magnetic fields. We use a large
sample of ~1000 Rotation Measures (RM) from radio galaxies and QSOs provided by P.P. Kronberg(LANL) to study
the different contributions to the observed RM.
Statistical analysis of RM distribution with z
We
used a subsample of 270 QSOs at high galactic latitudes (|b| > 45d)
up to z ~ 3.0 to look for evolution in the RM distribution with
z. We have found that the RM distribution at z > 1.0 is
significantly broader than that at low redshift. We have developed
models taking into account RM contributions local to the QSO,
contributions from intervening MgII systems (galaxies) and
contributions from the magnetic fields within the Milky Way to
reproduce the observed trend. We found that the data are best
reproduced with models with intervening MgII systems.
Width
of the RM distributions within are 68% (left) and 90% (right) of the
data points. The solid lines show a model with intervening strong MgII
absorbers. The dashed lines show a model taking into account Milky
Way RM contributions and contributions local to the QSO.
The dotted lines show an intervenor model where additional to the
strong MgII absorbers also weak MgII absorbers are considered.
.
Large scale magnetic fields in galaxies at z ~ 1
In
order to test the hypothesis if intervening MgII systems contribute to
the observed RM we took spectra of 77 QSO at UVES/VLT to do a
complete census of strong (EW > 0.3A) intervening MgII absorption
systems. Strong MgII absorption systems are know to originate in the
haloes of normal galxies with a covering factor close to unity for
impact parameters < 50 kpc. We could show that l.o.s. with strong
MgII absorption have indeed a broader RM distribution than those
without. The difference between the RM distributions imply that a
typical RM contribution per intervenor is around 140 rad m^2. This
implies that there are mikroGauss large scale magnetic fields in these
systems. It means that at the time when the Universe was only about one
third of its present age the magnetic fields were already at comparable
strength to those seen in today's galaxies. This significantly reduces
the number of e-foldings available in dynamo mechanism for the build-up
of coherent magnetic fields in galaxies. (It is normally assumed that
tiny seed magnetic fields in galaxies are amplified by a dynamo
mechanism to their present value)
Cumulative
|RM| distribution functions for l.o.s with zero(red), one(blue) and
two(black) strong MgII absorption lines along the lines of sight.
.
Probing the extension of magnetic fields in galaxies - dependence on galactic properties
We
have done imaging of the QSO fields for the l.o.s with strong MgII
absorption in the g,r,i,z bands at EFOSC2/NTT. At the moment I am
identfying the galaxies responsible for the MgII absorption. I will
then analyse how the observed RMs are related to the impact parameters
of the galaxies and can thus probe the extension of the magnetic fields
in these galaxies. I will also look if and how the RM is related to
other galactic properties, e.g. luminosity, color.
30x30''
stamps of 3 QSO fields where strong intervening MgII absorption systems
are detected. The QSO psfs are subtracted. In each field a candidate
galaxy is detected within 5''. (i-band images EFOSC2/NTT)
|
| Selected
Papers |
A Global Probe of Cosmic Magnetic Fields to High Redshifts
Kronberg, P.P., Bernet, M.L., Miniati, F., Lilly, S.J., Short, M.B., Higdon, D.M., ApJ,676 (2008)
Strong magnetic fields in normal galaxies at high redshift
Bernet, M.L., Miniati, F., Lilly, S.J., Kronberg, P.P., Dessauges-Zavadsky, M., Nature, 454 (2008)
MgII
absorption systems with EW > 0.1 A for a radio selected sample of 77
QSOs and their associated magnetic fields at high redshifts"
Bernet, M.L., Miniati, F., Lilly, S.J., ApJ, 711 (2010)
|
| Conferences, Workshops |
Espinho, Portugal, 08/2008: "The role of disk/halo interaction in galaxy evolution: Outflow vs infall", contributed talk
Bonn, Germany, 04/2008: "Astronomy in the next decade: Synergies with
the Square Kilometer Array", MCCT SKADS workshop, contributed talk
Bonn, Germany, 10/2007: European Radio Interferometry school 2007
Zurich, Switzerland, 09/2007: "From protostellar cores to disk galaxies", poster presented
|
| Time lapse movies |
The rise of the Milky Way above the 3.6m telescope in La Silla
The rise of the Milky Way in La Silla
|
|
About us