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I
N S T I T U T E O
F A
S T R O N O M Y |
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Extragalactic
Astrophysics & |
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Pascal Oesch |
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Curriculum
Vitae
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ETH |
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Research
Interests
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I
am currently doing my PhD with Marcella
Carollo
using state of the art data of the universe to study galaxy evolution
through cosmic time and in different environments. My main
research interests include
A brief
summary of my past research activities can be found below.
Lyman
Break Galaxies My first two
papers
used the extremely Hubble Ultra Deep Field and its extension, an additional HST Large
Program of 204 orbits to increase the depth and area of the UDF
(the UDF05;
GO10632, Cycle 14). I have determined the Lyman Break Galaxy Luminosity
Function (LF) at z~5 (Oesch et al. 2007) and also z~7 (Oesch et al. 2009a), where we were able put first
constraints
on the LF with the small number of
objects that were detected in the UDF/UDF05 NIR data. From the
evolution of the LF from z~3 - 7 (i.e. already into the Epoch of
Reionization) we could derive the contribution of Lyman Break Galaxies
to the reionization of the universe (see also here).
 Filling
factor of ionized hydrogen as a function of redshift. The solid lines
show the evolution of the filling factor calculated by assuming a faint
end slope alpha=-1.74 and an evolution of the galaxy LF by 0.35 mag per
unit redshift, and by integrating down to different limiting SFRs (~1,
0.01, 0.0001 Msol/yr; lower gray, black, and upper gray lines,
respectively). The dashed line assumes the same evolution in M* but
alpha=-1.9. The dash-dotted line corresponds to no evolution of the LF
from z~6 out to z=20; the dotted one assumes the same but with the z~7
LF. If not stated otherwise all curves are integrated down to SFRs of
10^-2 Msol/yr. The corresponding electron scattering optical depths are
also indicated.
First Results of the HUDF09 WFC3/IR program
The
work on the very high redshift side has been extended with the much
improved NIR capabilities of
the WFC3/IR camera. We
are part of a collaboration which has
been granted time for an ultra-deep NIR imaging survey around the UDF
(the HUDF09; GO11563,
Cycle 17).
This data will allows us to derive much stronger constraints on the
evolution of the LBG LF to z~8-10 into the EoR and on the contribution
of
these galaxies to reionization. The first epoch data of the HUDF09
consists of 62 orbits covering the optical HUDF09 field with three NIR
filter imaging in the Y, J, and H band. The sensitivities are ~29 mag
in all three bands, nicely complementing the optical depths. In my
first two papers I was concentrating on the z~7 galaxy population. We
have identified 16 such objects, based on the Lyman Break Technique and
their z-Y vs. Y-J colors. This has allowed us to put first constraints
on the faint end slope of the LBG luminosity function at z~7, for which
we have derived a value of alpha=-1.77+-0.20. This very steep slope
underpins the large contribution of very faint galaxies to the
reionization of the universe (Oesch et al. 2009b).
A
sample of the 7 brightest (out of 16) z-drop galaxies that we have
identified in the HUDF09 WFC3/IR images. The sizes of the postage
stamps are 2.2" x 2.2". As can be seen, these galaxies are undetected
in all the optical bands of the HUDF blueward of the z-band, which
samples the 8500 A. This is attributed to the absorption of UV photons
by intergalactic neutral hydrogen, which is abundantly present at these
early cosmic times, and is the basis of the Lyman Break Technique. (For
stamps of all z~7 galaxies see Oesch et al. 2009b or here.)
The
Lyman Break Galaxy luminosity function at z~7 as derived from our 16
candidates in the HUDF09 WFC3/IR imaging (red dots). The black solid
line corresponds to our best-fit LF with alpha=-1.77, phi*=1.4x10^-3
Mpc^-3 mag^-1 and M*=-19.91.
This value of the faint end slope is consistent with no evolution
since z~2. Datapoints from previous estimates are shown as open
symbols; orange circles: Bouwens et al. 2008, green diamonds: Oesch et
al. 2009a, dark red squares: Ouchi et al. 2009. The latter ones have
been used in our fit to constrain the bright end of the LF. The
remaining lines show the LF at z~5 (light gray solid line; Oesch et al.
2007), and z~6 (dark gray solid line; Bouwens et al. 2007). Note that
the z~7 points of Bouwens et al. (2008) and Oesch et al. (2009) are
partially based on NICMOS data from the HUDF and are thus not
independent from our new measurements. Additionally,
I have studied the structural and morphological properties of the z~7-8
galaxies that our team has identified. Maybe unsurprisingly, they seem
to be extremely compact, with only a small fraction of galaxies showing
double cores, unlike at lower redshifts. The size evolution of LBGs
from z~3-8 is well described by a scaling of approximately 1/(1+z),
independent of luminosity. Furthermore, we have found that the average
star-formation density in these objects is surprisingly constant over
the entire redshift range z~4-8. For more information see Oesch et al. 2009c.
ZEBRA In
parallel I developed ZEBRA+, the extension of ZEBRA,
the Zurich Extragalactic Bayesian Redshift
Analyzer.
Apart from the photometric redshift estimation, ZEBRA+ returns stellar
masses, average ages and
other key diagnostics of galaxy evolution. It is based on fitting
synthetic stellar population models to galaxy photometry. I have
applied it to the
100'000 galaxies in COSMOS and
I am using the measurements to study the build-up of stellar mass in
different galaxy types out to z~1.2 (Oesch et al. 2009d and Oesch et al. 2010, in preparation). As
a spin-off of my COSMOS activities I am also involved in the zCOSMOS
survey, where I compute absolute magnitude estimates based on ZEBRA and
photometric redshifts complementing the spectroscopic measurements.
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Selected
Papers
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The UDF05 Follow-up of the HUDF: I. The Faint-End Slope of the Lyman-Break Galaxy Population at z~5 Oesch, P. A.; Stiavelli, M.; Carollo, C. M.; Bergeron, L. E.; Koekemoer, A. M.; Lucas, R. A.; Pavlovsky, C. M.; Trenti, M.; Lilly, S. J.; Beckwith, S. V. W.; Dahlen, T.; Ferguson, H. C.; Gardner, J. P.; Lacey, C.; Mobasher, B.; Panagia, N.; Rix, H. -W. 2007, ApJ, 671, 1212 arXiv:0706.2653 (preprint) The UDF05 Follow-up of the HUDF: II. Constraints on Reionization from z-dropout Galaxies Oesch, P. A.; Carollo, C. M.; Stiavelli, M.; Trenti, M.; Bergeron, L. E.; Koekemoer, A. M.; Lucas, R. A.; Pavlovsky, C. M.; Beckwith, S. V. W.; Dahlen, T.; Ferguson, H. C.; Gardner, Jonathan P.; Lilly, S. J.; Mobasher, B.; Panagia, N. 2009, ApJ, 690, 1350 arXiv:0804.4874 (preprint) z~7 Galaxies in the HUDF: First Epoch WFC3/IR Results Oesch, P. A.; Bouwens, R. J.; Illingworth, G. D.; Carollo, C. M.; Franx, M.; Labbe, I.; Magee, D.; Stiavelli, M.; Trenti, M.; van Dokkum, P. G. 2009, ApJL accepted arXiv:0909.1806 (preprint) Structure and Morphologies of z~7-8 Galaxies from ultra-deep WFC3/IR Imaging of the HUDF Oesch, P. A.; Bouwens, R. J.; Carollo, C. M.; Illingworth, G. D.; Trenti, M.; Stiavelli, M.; Magee, D.; Labbe, I.; Franx, M. 2009, ApJL accepted arXiv:0909.5183 (preprint) The Build-Up of the Hubble Sequence in the COSMOS Field Oesch, P. A.; Carollo, C. M.; Feldmann, R.; Hahn, O.; Lilly, S. J.; Sargent, M. T.; Scarlata, C.; Aller, M. C.; Aussel, H.; Bolzonella, M.; Bschorr, T.; Bundy, K.; Capak, P.; Ilbert, O.; Kneib, J. -P.; Koekemoer, A. M.; Kovac, K.; Leauthaud, A.; Le Floc'h, E.; Massey, R.; McCracken, H. J.; Pozzetti, L.; Renzini, A.; Rhodes, J.; Salvato, M.; Sanders, D. B.; Scoville, N.; Sheth, K.; Taniguchi, Y.; Thompson, D. 2009, submitted to ApJL arXiv:0911.1126 (preprint)
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About us
