May 2017
May 1, Monday
12:10 pm (TAC)
Aurelian Hees, UCLA
Campbell 131
Searches for extensions to General Relativity: from the Solar System to our Galactic Center
In this talk, we will review the basic principles of General Relativity and give motivations to search for alternative theories of gravitation. Then, we will review some of the very recent tests of the gravitation theory performed in the Solar System insisting on their implications. We will also discuss how the monitoring of short-period stars orbiting the supermassive black hole in our Galactic Center can be used to test General Relativity. Recent results in the fifth force formalism will be presented and plans to measure relativistic effects during the closest approach of the star S0-2 in 2018 will also be developed.
May 4, Thursday
4 pm (RPM)
Manoj Kaplinghat, Irvine
LBL 50-5132
“The self-interacting dark matter paradigm: motivations and tests”
I will describe how a simple model where dark matter has large elastic self-interactions (cross section over mass of order barns per GeV) can fully explain the observed diversity of all galactic rotation curves. I will summarize the constraints imposed on model building by observations of clusters of galaxies and end with an outline of tests of this paradigm.
May 22, Monday
12:10 pm (TAC)
Dylan Nelson, Garching
Campbell 131
The next generation of cosmological hydrodynamical simulations: Introducing IllustrisTNG
I will introduce the new IllustrisTNG project, a next generation of cosmological magneto-hydrodynamical simulations. The first, "TNG100", realizes a 100 Mpc volume and is a close analog to the original Illustris simulation. The second simulation, "TNG300", includes 2500^3 resolution elements in a 300 Mpc box, a
volume more than twenty times larger hosting 280 massive clusters above 10^14 Msun and more than 12,000 Milky Way mass galaxies. Both simulations are run using the new TNG model for galaxy formation physics, developed in the moving-mesh code Arepo, incorporating several physical and numerical improvements, including a full treatment of cosmic magneto-hydrodynamics (MHD).
I will first discuss the TNG model for galaxy formation, including the specific
changes we made post-Illustris, and why, assessing the outcome of the new model on some benchmark runs. Leveraging the power of the new large-volume simulations, I will then show early results on the bimodal galaxy optical color distribution at z=0. Accounting for the attenuation of stellar light by dust, we compare the (g-r) colors of simulated galaxies to the observed distributions from SDSS, spanning 10^9 < Mstar/Msun <10^12. We find a striking improvement with respect to the original Illustris simulation, as well as excellent quantitative agreement with observations. I will discuss the relationships between the color of a galaxy and its SFR, gas content, and magnetic properties, among others. I will finish with some insights on the buildup of the color-mass plane, the role of the BH in quenching and color transition, and the formation of the red sequence in TNG.
May 25, Thursday
1:00 pm
Florian Kuhnel (KTH Royal Institute of Technology, Stockholm)
Place: 50B-4205
Primordial Black Holes as Dark Matter
Abstract: Primordial black holes are black holes that may have formed in the early Universe. Their masses span potentially a range from as low as the Planck mass up to many orders of magnitude above the solar mass. Besides their conceptual importance regarding our understanding of quantum effects and gravity, they may provide the dark matter. In order to constrain this possibility, a proper understanding of their formation mechanism is crucial. In my talk, after a general introduction on primordial black holes, I will discuss recent investigations on this issue, including so-called critical collapse, non-sphericity and non-Gaussianity. Furthermore, I will discuss how to properly compare extended primordial black-hole mass spectra to observational constraints, such as those deriving from recent microlensing surveys.
May 26, Friday
12 pm (INPA)
Titouan Lazeyras, Garching
LBL 50-5132
Dark matter halo bias from separate universe simulations
The large-scale local bias parameters of dark matter halos are essential to
describe the statistics of halos and galaxies on large scales, as well as for
the halo model of the matter distribution. Using so-called separate universe
simulations, we recently obtained precise measurements of the three leading
bias parameters. For b2 and b3, these are the most precise measurements
to date. We compare our results with bias parameters obtained from two
and three points cross-correlation functions and with theoretical predictions
from the excursion set peaks (ESP) model.
Using the same set of simulations, we further investigate halo assembly bias,
i.e. the dependence of the halo bias on properties other than the halo mass.
We focus on four halo properties : halo concentration, spin, ellipticity and
mass accretion rate. We measure assembly bias for b1 and nd good agree-
ment with previous studies. Furthermore, we present results for assembly
bias in b2 which are among the rst ones and most precise to date. To try
and better understand the physical mechanisms behind assembly bias, we
also look at the joint dependence of bias on two halo properties in addition
to the mass.
June 2017
June 1 , Thursday
4pm (RPM)
Florian Beutler, Portsmouth
LBL 50-5132
“On the reliability of Baryon Acoustic Oscillation (BAO) measurements”
In this talk I will discuss the reliability of the Baryon Acoustic Oscillation (BAO) signal in the distribution of galaxies. The solid theoretical understanding of this observable means that it represents one of only a few cosmological observables that are not yet dominated by systematic errors. This is one reason why BAO are one of the main science drivers for future galaxy surveys like DESI and Euclid.
I will discuss my recent work on the relative velocity effect as one potential systematic for BAO. The relative velocity effect originates from the same physical effects which imprinted the BAO signal and therefore acts on the same scale. I will introduce this effect in detail, discuss how we can include it in our modeling and present current constraints from the Baryon Oscillation Spectroscopic Survey (BOSS).
August 2017
September 2017
Sep 5, Tuesday
1:10 pm (Cosmology/ BCCP)
tba,
Campbell 131
Sep 12, Tuesday
1:10 pm (Cosmology/ BCCP)
held,
Campbell 131
Sep 19, Tuesday
1:10 pm (Cosmology/ BCCP)
tba,
Campbell 131
Sep 26, Tuesday
1:10 pm (Cosmology/ BCCP)
Andrina Nicola, ETH Zurich
Campbell 131
October 2017
Oct 3, Tuesday
1:10 pm (Cosmology/ BCCP)
tba,
Campbell 131
Oct 10, Tuesday
1:10 pm (Cosmology/ BCCP)
tba,
Campbell 131
Oct 17, Tuesday
1:10 pm (Cosmology/ BCCP)
tba,
Campbell 131
Oct 24, Tuesday
1:10 pm (Cosmology/ BCCP)
Mackenzie Jones, Dartmouth
Campbell 131
Oct 31, Tuesday
1:10 pm (Cosmology/ BCCP)
tba,
Campbell 131
November 2017
Nov 7, Tuesday
1:10 pm (Cosmology/ BCCP)
tba,
Campbell 131
Nov 14, Tuesday
1:10 pm (Cosmology/ BCCP)
Anze Slosar, BNL
Campbell 131
Nov 21, Tuesday
1:10 pm (Cosmology/ BCCP)
tba,
Campbell 131
Nov 28, Tuesday
1:10 pm (Cosmology/ BCCP)
tba,
Campbell 131
December 2017
Dec 5, Tuesday
1:10 pm (Cosmology/ BCCP)
tba,
Campbell 131
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