# Upcoming and Previous Seminars (Past months or Previous years)

Note that if the talk's pdf or ppt is available after the talk, you can get it by clicking on the talk title.

Physics/Astronomy C290C Cosmology and Cosmology-BCCP Seminar
The Physics/Astronomy C290C series consists of the Cosmology-BCCP LBNL-Physics-Astronomy Cosmology seminars held Tuesdays 1:10-2:00 pm in room 131 Campbell Hall. Because this room is hard to keep clean, please don't bring your lunch (this is a change).

Speaker/Visitor Info is here.

 BOSS and Nyx (Image by C. Stark) Note that there are also other talks which generally might be of interest, including: Theoretical Astrophysics Center Seminars (Mondays, 12:10 pm, 131 Campbell Hall) RAL seminars (usually Mondays 3:10 pm, tba Campbell Hall) Physics Dept. Colloquia (Mondays, 4:15 pm, 1 LeConte) arXiv discussion: Cosmology, Astrophysics, Neutrino arXiv Discussion (Tuesdays 11:15 am, Cosmology Commons, 3rd floor Campbell south side ). Sign up and vote for papers at http://www.benty-fields.com/ . Tuesday and Thursday RPM's at LBNL (4 pm, 50A-5132) Tuesday, 3:30-4:30 pm, 501B Campbell Hall, GalForm discussion (informal galaxy formation discussions) Thursday arxiV coffee (11:15-11:45 am, Campbell 6th floor lounge) register here Astro Thursday Lunch (lunch, short talks/paper discussions/talks by visitors), 12:30 pm Campbell 131 A&B Astronomy Colloquium (4 pm Thursdays, 2 LeConte Fall, 1 LeConte spring) INPA journal club (Friday at noon, occasionally other days, in LBNL, 50-5132). This week in particle theory talks on campus and at LBL SSL Colloquia, (11 am Fridays, Addition conference room or annex conference room, SSL) Center for Time Domain Informatics Seminar Series, dates/times variable

October 2016
Oct 4, Tuesday
1:10 pm (Cosmology/ BCCP)
Irene Shivaei, Riverside
Campbell 131
A Multi-Wavelength Census of Star Formation and Dust in Galaxies at z ~ 2
Redshift of z ~ 2 is an important era in the history of the universe, as it contains the peak of star formation rate density and quasar activity. I will talk about the properties of galaxies during this era from two different, yet complementary, aspects: star formation and mass assembly, and galactic dust enrichment. In this study, I use a wealth of spectroscopic data obtained by the MOSDEF survey. I will introduce the MOSDEF survey, which is a multi-institutional project that uses the near-IR MOSFIRE spectrograph on the Keck I telescope to characterize the gaseous and stellar contents of ~ 1500 rest-frame optically selected galaxies at 1.37 < z < 3.80. Furthermore, I incorporate the mid- and far-IR data from the Spitzer and Herschel telescopes to obtain a complete census of obscured and unobscured star formation in galaxies. Specifically, I explore the star-formation rate and stellar mass relation at z ~ 2, using multi-wavelength star-formation rate tracers (UV, Hα, 24 micron, and far-IR). Moreover, I investigate, for the first time, the variation of the PAH emission at 7.7 micron, traced by Spitzer/MIPS 24 micron, in galaxies spanning a wide range in metallicity at z ~ 2. Our results have important implications for high-redshift studies that adopt 24 micron flux to derive total IR luminosity and star-formation rate.
Oct 11, Tuesday
1:10 pm (Cosmology/ BCCP)
Derek Inman, CITA
Campbell 131
Non-linear neutrino effects in large scale structure
Detecting the cosmic neutrino background, either through observation or experiment, has proven to be a substantial challenge due to the very small neutrino mass. Typical cosmological studies rely on two point statistics and must distinguish small neutrino effects from much larger cold dark matter (CDM) and baryonic ones. Higher order statistics, in which generic CDM effects can be cancelled by design, are a promising avenue to improve constraints on neutrino properties. However, utilizing them requires an accurate understanding of neutrino co-evolution with the non-linear CDM. Surprisingly, the low neutrino mass makes this computation a significant numerical challenge. I will describe our N-body simulations that study this problem, including the TianNu simulation, which contains nearly three trillion particles. I will then describe three non-linear effects: the evolution of the neutrino power spectrum, the relative velocity dipole between neutrinos and cold dark matter, and differential neutrino condensation onto halos.
Oct 18, Tuesday
1:10 pm (Cosmology/ BCCP)
Chen He Heinrich, Chicago
Campbell 131
Complete Reionization Constraints from Planck 2015 Polarization
I will present a recent analysis of the Planck 2015 data that is complete in the reionization observables from large angle CMB polarization measurements using principal components. By allowing for an arbitrary ionization history, this technique tests the robustness of total optical depth inferences from the usual instantaneous reionization assumption. A reliable measurement of the total optical depth is important for the interpretation of many other cosmological parameters such as the dark energy and neutrino mass. We found that Planck 2015 data not only allow a high redshift z>15 component to the optical depth but prefer it at the 2σ level. This high redshift component contributes to a higher total optical depth than in the instantaneous reionization analysis, illustrating the need for a complete treatment of reionization observables. I will further demonstrate the power of the principal component method to efficiently constrain models given predictions of ionization history by applying our effective likelihood code.
Oct 20, Thursday
4 pm (RPM)
Marilena LoVerde, Stony Brook
LBL 50-5132
Neutrinos, Quintessence and Structure Formation in the Universe
The large-scale structure of our universe (the distribution of galaxies on very large-scales for instance) contains a wealth of information about the origin, evolution, and matter content of the universe. Extracting this information relies crucially on understanding how galaxies and other biased objects trace the large-scale matter distribution. In a universe such as our own, with both cold dark matter and massive neutrinos, or in alternative cosmologies with clustered quintessence, this problem is much more complicated. I will discuss new tools that my group has developed to study gravitational evolution in cosmologies with multiple fluids, the novel signatures we have identified including a new probe of neutrino mass, and the broader implications for models of large-scale structure.
Oct 21, Friday
12 pm (INPA talk, noon, not 12:10)
Enea Di Dio,
LBNL 50-5132
Relativistic effects on LSS: power spectrum and bispectrum
I will discuss the Large Scale Structure power spectrum and bispectrum in a relativistic framework. To first order, a relativistic description includes terms beyond the Kaiser approximation (Doppler effects and galaxy evolution), gravitational potentials and integrated terms (cosmic magnification, integrated Sachs-Wolfe and Shapiro time-delay). I will show how they can be isolated by correlating different probes, or by using the so-called multi-tracer technique. Through this technique future surveys may be able to detect some relativistic contributions. I will also discuss relativistic effects beyond linear theory, the relativistic bispectrum and how the lensing deflection angle smears out the BAO wiggles.
Oct 25, Tuesday
1:10 pm (Cosmology/ BCCP)
Alessandro Manzotti, Chicago
Campbell 131
Delensing CMB B-modes: results from SPT
A promising signature of cosmic inflation is the presence of a "B-mode" component in the polarization of the Cosmic Microwave Background (CMB) induced by primordial gravitational waves. For many inflation models, this B-mode signal is predicted to be at a level detectable in the near future. However current searches are limited by a "lensing B-mode" component that is produced by gravitationally lensing primordial E modes. In order to potentially detect the inflationary signal from B-mode measurements, lensing B modes must be characterized and removed in a process referred to as "delensing." This process has been studied extensively theoretically and with simulations, but has not been performed on polarization data. In this talk, we present the results of CMB B-mode delensing using polarization data from the South Pole Telescope polarimeter, SPTpol. Furthermore, using realistic simulations that include filtering and realistic CMB noise, we will show what is currently limiting the delensing efficiency and how it will rapidly improve in the near future.
Oct 27, Thursday
4 pm (Astronomy Colloquium)
Shirley Ho, LBL
Le Conte

Oct 28, Friday
**1 pm** (INPA talk), time change due to runaround
Samuel Flender, Argonne
LBNL 50-5132
The kinematic Sunyaev-Zel'dovich effect as a cosmology probe?
Future data from galaxy redshift surveys, combined with high-resolutions maps of the cosmic microwave background, will enable measurements of the pairwise kinematic Sunyaev-Zel'dovich (kSZ) signal with unprecedented statistical significance. This signal probes the matter-velocity correlation function, scaled by the average optical depth (tau) of the galaxy groups and clusters in the sample, and is thus of fundamental importance for cosmology. However, in order to translate pairwise kSZ measurements into cosmological constraints, external constraints on tau are necessary. In this talk I will present the current state of kSZ measurements, including a recent measurement by SPT and DES, insights from simulations, as well as recent progress in modeling the tau profile of galaxy clusters.

November 2016
Nov 1, Tuesday
1:10 pm (Cosmology/ BCCP)
Alison Strom, Caltech
Campbell 131
"Star-formation history and chemical enrichment in the early Universe: clues from the rest-UV and rest-optical spectra of high-redshift galaxies"
Galaxies at the peak of cosmic star formation (z~2-3) exhibit significantly higher star formation rates and gas fractions at fixed stellar mass than nearby galaxies. These z~2-3 galaxies are also distinct in terms of their nebular spectra, reflecting important differences not only in the physical conditions of their interstellar medium (e.g., electron density and gas-phase metallicity), but also in the details of their massive stellar populations, especially their ionizing radiation fields. Jointly observing galaxies' HII regions, at rest-UV and rest-optical wavelength, and massive stars, in the rest-UV bandpass, is central to constructing a framework for understanding the differences between z~2-3 and z~0 star-forming galaxies and for self-consistently explaining the trends observed in the high-redshift population. I will present results from the Keck Baryonic Structure Survey (KBSS), which uniquely combines observations of the rest-optical spectra of ~400 individual galaxies (obtained with Keck/MOSFIRE) with deep rest-UV spectroscopy of many of the same galaxies (obtained with Keck/LRIS). These measurements represent one of the most comprehensive spectroscopic studies of z~2-3 galaxies to date and, when compared with predictions from photoionization models, offer compelling evidence that high-redshift galaxies exhibit chemical abundance patterns distinct from local galaxies, likely as the result of systematic differences in their star-formation histories.
Nov 4, Friday
12 pm (INPA talk, noon, not 12:10)
Colin Hill,
LBNL 50-5132
New Information in Ancient Photons: Novel Approaches to CMB Secondary Anisotropies
Cosmic microwave background (CMB) experiments have recently entered a new era in which cosmological and astrophysical constraints derived from the secondary anisotropies (due to late-time effects) substantially improve upon those derived from the primary anisotropies alone. In this talk, I will discuss new approaches to extract information from these signals, placed in the broader context of component separation in CMB analysis. I will describe novel methods for studying the thermal Sunyaev-Zel'dovich (SZ) effect --- the inverse-Compton scattering of CMB photons off hot electrons --- using cross-correlations, stacking, and beyond-Gaussian statistics. I will present projections for thermal SZ extraction from Advanced ACT data based on a new component-separation pipeline, as well as new foreground-marginalized forecasts for the all-sky tSZ (and $\mu$) spectral distortion monopole from the proposed PIXIE satellite. I will then present a measurement of the kinematic SZ effect (due to electrons moving with a net bulk velocity along the line-of-sight) with Planck, WMAP, and WISE data using a novel estimator that does not require redshift estimates for individual tracers. This measurement yields the tightest kinematic SZ-derived constraint on the low-redshift baryon fraction to date. The result is consistent with constraints derived from the primary CMB and Big Bang nucleosynthesis, thus resolving the long-standing "missing baryon problem".
Nov 8, Tuesday
1:10 pm (Cosmology/ BCCP)
Michael Wilson, ROE
Campbell 131

Nov 15, Tuesday
1:10 pm (Cosmology/ BCCP)
Vanessa Boehm, Garching
Campbell 131

Nov 17, Thursday
4 pm (Astronomy Colloquium)
Michael Boylan-Kolchin, Austin
Le Conte

Nov 18, Friday
12 pm (INPA talk, noon, not 12:10)
Daniele Sorini, Heidelberg
LBL 50-5132

Nov 22, Tuesday
1:10 pm (Cosmology/ BCCP)
no talk
Campbell 131

Nov 29, Tuesday
1:10 pm (Cosmology/ BCCP)
Luke Kelley, Harvard
Campbell 131

December 2016
Dec 1, Thursday
4 pm (Astronomy Colloquium)
Alexie Leauthaud, Santa Cruz
Le Conte

Dec 2, Friday
12 pm (INPA talk, noon, not 12:10)
Sebastian Cantalupo, Zurich
LBNL 50-5132

Dec 6, Tuesday
1:10 pm (Cosmology/ BCCP)
Sukhdeep Singh, CMU
Campbell 131

Dec 9, Friday
12 pm (INPA talk, noon, not 12:10)
Julian Munoz, JHU
LBNL 50-5132

## Past Months ( Previous Years )

August 2016
Aug 29, Monday
12:10 pm (TAC)
Dan Whalen, ICG, Portsmouth
Campbell 131
Finding the First Cosmic Explosions
Primordial stars formed about 200 Myr after the Big Bang, ending the cosmic dark ages. They were the first great nucleosynthetic engines of the universe and may be the origins of the supermassive black holes (SMBHs) found in most massive galaxies today. In spite of their importance to the evolution of the early universe not much is known for certain about the properties of Pop III stars. But with the advent of JWST, Euclid, WFIRST and the ELTs it may soon be possible to directly observe their supernovae in the NIR and thus unambiguously constrain the properties of the first stars. I will present radiation hydrodynamical calculations of the light curves of the first SNe in the universe and discuss strategies for their detection. I will also describe how some high-z SNe may already have been found in surveys of galaxy cluster lenses such as CLASH and Frontier Fields. I will conclude my talk with new calculations of the evolution and collapse of supermassive primordial stars that constrain the masses of the first quasars at birth.
Aug 31, Wednesday
12 pm (INPA talk, noon, not 12:10)
Dan Whalen, ICG, Portsmouth
LBL 50-5026
How Supermassive Black Holes Form by z ~ 7
Over 100 quasars have now been discovered at z > 6, less than a Gyr after the Big Bang. The discovery of supermassive black holes (SMBHs) by this epoch posed severe challenges to current theories of structure formation because it is not known how objects so massive appeared by such early times. However, we have now developed numerical simulations that show that these quasars can form from direct collapse black holes at z ~ 20 if they are fed by strong, cold accretion streams, like those thought to fuel the rapid growth of some galaxies at later epochs. I will discuss these simulations and formation channels for DCBHs at high redshift. I will also discuss prospects for their detection in the NIR and at 21 cm by Euclid, JWST and the SKA.

September 2016
Sep 6, Tuesday
1:10 pm (Cosmology/ BCCP)
Miguel Aragon-Calvo, Riverside
Campbell 131
A cosmic web model of galaxy formation and some adventures in data visualization
The cosmic web is the stage where galaxy formation and evolution occurs. However, current models of galaxy formation ignore the effect of cosmic environment beyond basic descriptors and rely on crude approximations that do not capture the complex interplay between galaxies and their environment. In this talk I will discuss the Cosmic Web Detachment (CWD) model recently proposed to describe the effect of cosmic environment on galaxy formation and evolution. The CWD model can naturally reproduce a range of galaxy properties and provides a framework to interpret observations in a truly cosmological context.
During the talk I will make use of innovative visualization techniques including stereo 3D , 3D printing and natural interaction and discuss how data visualization can be used as a driver for scientific discovery.
Sep 13, Tuesday
1:10 pm (Cosmology/ BCCP)
Andrea Petri, Columbia
Campbell 131
Cosmology with Weak Gravitational Lensing: the information beyond the Power Spectrum ,
also movies here and here

The LambdaCDM model of the Universe has been proven tremendously successful in explaining experimental data with only a few free parameters. While observations from a variety of sources (CMB, Supernovae IA, BAO, Large Scale Structure) have done an outstanding job in constraining the standard parameter space, the Dark Energy equation of state, w, remains essentially unconstrained. Weak Gravitational Lensing (WL) is a promising observational technique in this sense, because of its sensitivity to late universe physics, when Dark Energy dominates. Because of late time non-linearities, WL observables are not Gaussian distributed, and quadratic statistics such as Power Spectra likely miss some of the cosmological information contained in observations. Possible complementary statistics one could consider include higher order moments, peak counts and topological descriptors. I will review the fundamentals of WL, as well as the ray--tracing formalism on which our numerical simulations are based. I will also summarize our efforts in improving parameter constraints using a variety of higher order statistics, with both galaxy and CMB lensing data. I will also outiline some recent results on analytical prediction and origin of WL convergence peaks. To conclude, I will discuss some of the numerical subtleties that one must take into consideration when using higher order statistics to analyze WL data sets.
Sep 15, Thursday
4 pm (RPM)
Nick Kaiser, Hawaii
LBL 50-5132
The Physics of Gravitational Redshifts in Clusters of Galaxies
Wojtak, Hansen and Hjorth and others have measured the long-predicted gravitational redshift of light escaping from galaxy clusters using Sloan Digital Sky Survey data. The effect is very small, corresponding to a velocity shift of only ~10 km/s in clusters with internal random motions of order 600 km/s, but the result appears to be robust and is in good agreement with general relativity predictions and possibly in conflict with some alternative theories. It was soon realised that the interpretation of this measurement is more complex than initially thought as one needs to allow for the transverse Doppler (TD) redshift. In this talk I will describe how there are actually two more rather subtle and unexpected physical effects that need to be considered in interpreting these observations; there is a `light cone' effect that augments the TD shift, and there is a competing effect that reverses the sign of the transverse Doppler effect so that we actually observe a transverse Doppler blue-shift. I will discuss how these observations constrain gravitation theory, and along the way discuss some issues concerning the interpretation of astronomical redshifts in a broader context.
Sep 15, Thursday
4:10 pm (Astronomy Colloquium)
Freeke van de Voort, UCB and Taiwan
1 Le Conte
Cosmic gas flows: the key to understanding galaxy formation
The evolution of galaxies is critically linked to the gas flows in and the assembly history of their surrounding haloes. Although observationally gas is harder to detect than stars, it lies at the heart of our understanding of galaxy formation. The circumgalactic medium provides the gas reservoir to fuel star formation in galaxies, but galaxies do not just grow passively. Strong outflows driven by supernovae and supermassive black holes heat and enrich the galaxy's environment, thus completely changing its evolution. And it doesn't end there: galaxies can also grow through merging and they can be stripped of their gas and stars when they become satellites. I will discuss results from cosmological, hydrodynamical simulations and focus on the interaction of galactic feedback and gas accretion, their effect on the growth of galaxies, and on ways to probe this baryonic cycle observationally.
Sep 16, Friday
12 pm (INPA talk, noon, not 12:10)
Nick Kaiser, Hawaii
LBNL 50-5132
The Effect of Gravitational Lensing on Cosmological Parameter Estimation
A very long standing question in cosmology is whether gravitational lensing biases the distance-redshift relation D(z) or the mean flux density of sources. Interest in this has been rekindled by recent results in 2nd order relativistic perturbation theory which, if correct, would have profound implications for cosmological parameter estimation from both SN1a and the CMB. In this talk I shall first review the somewhat confusing history of the subject, going back to the early '60s and including both Weinberg's 1976 argument that there should be no effect on grounds of flux conservation and the general relativistic "focusing theorem" of the '80s that foreshadows the more recent results. I then show how the claimed subtle relativistic effects actually result from confusion between different types of averaging (specifically between averaging over sources and averaging over directions on the sky). I also show that while Weinberg's argument conceals a hidden loop-hole, in that he assumes that the area of a surface of constant redshifts is unaffected by lensing, the error incurred is only a one part in a million effect. This result validates conventional methods for analysis of the CMB and shows that, counter to claims in the literature, the focusing theorem does not in fact reveal an intrinsic tendency for structure to cause focusing of light rays.
Sep 19, Monday
12:10 pm (TAC)
Sarah Wellons, Harvard/CfA
Campbell 131
The diverse progenitors and descendants of (compact elliptical) galaxies in cosmological simulations
bservations of the high-redshift universe have revealed a population of galaxies which are already very massive (~10^11 Msun at z=2) and have typical sizes of < 2 kpc, much smaller than their counterparts in the local universe. How such dense, massive galaxies form, and why they appear to be less common at low redshift, have been questions of interest for both theorists and observers. I will discuss these questions in the context of the Illustris simulation, a hydrodynamical cosmological simulation in which tens of thousands of galaxies form, evolve, and interact with each other, situated within a cosmological context. I select a group of massive compact galaxies at z=2 in the simulation and trace them back and forth in time to discover both how they formed at high redshift, and what they evolve into at the present day. I find a variety of both progenitors (our compact galaxies form either via central starbursts generally brought on by mergers, or by racing out to the tip of the SF main sequence and forming very early) and descendants (many formerly-compact galaxies lurk at the core of a more massive galaxy today, others were consumed in mergers, and some evolve passively and undisturbed). Finally, I will discuss the implications of these results for observational methods of connecting galaxy populations across redshifts - in particular, the assumption of a constant cumulative comoving number density - and suggest an improvement to this method which takes the complexity and variety of galaxy evolutionary paths into account.
Sep 20, Tuesday
1:10 pm (Cosmology/ BCCP)
Hy Trac, CMU
Campbell 131
New Ways to Use Dynamical Measurements of Galaxy Clusters
Galaxy clusters contain large amounts of cold dark matter, hot ionized gas, and tens to hundreds of visible galaxies. The abundance of clusters as a function of mass and redshift can be used to probe the growth of structure and constrain cosmological parameters. Dynamical measurements probe the entire mass distribution, but standard analyses yield unwanted high mass errors. First we show that modern machine learning algorithms can improve mass measurements by more than a factor of two compared to using standard scaling relations. Support Distribution Machines are used to train and test on the entire distribution of galaxy velocities to maximally use available information. Second we show that cluster abundance can be quantified with the distribution of direct observables rather than inferred mass to avoid uncertainties in the mass-observable relation. A novel statistic called the velocity distribution function (VDF) is constructed by stacking the probability distribution of galaxy velocities for a select number of clusters in a given volume. The VDF can be measured directly and precisely, and produces unbiased constraints on cosmological parameters. Finally we discuss how our approaches can be generalized to multi-wavelength observations of gravitational lensing, SZ effect, and X-ray emissions.
Sep 27, Tuesday
1:10 pm (Cosmology/ BCCP)
Emmanuel Schaan, Princeton
Campbell 131
Understanding large-scale structure from the CMB
In this seminar, I will present two promising ways in which the cosmic microwave background (CMB) sheds light on critical uncertain physics and systematics of the large-scale structure.
Shear calibration with CMB lensing (arXiv:1607.01761): Realizing the full potential of upcoming weak lensing surveys requires an exquisite understanding of the errors in galaxy shape estimation. In particular, such errors lead to a multiplicative bias in the shear, degenerate with the matter density parameter and the amplitude of fluctuations. Its redshift-evolution can hide the true evolution of the growth of structure, which probes dark energy and possible modifications to general relativity. I will show that CMB lensing from a stage 4 experiment (CMB S4) can self-calibrate the shear for an LSST-like optical lensing experiment. This holds in the presence of photo-z errors and intrinsic alignment.
Evidence for the kinematic Sunyaev-Zel'dovich (kSZ) effect (arXiv:1510.06442); cluster energetics: Through the kSZ effect, the baryon momentum field is imprinted on the CMB. I will report significant evidence for the kSZ effect from ACTPol and peculiar velocities reconstructed from BOSS. I will present the prospects for constraining cluster gas profiles and energetics from the kSZ effect with SPT-3G, AdvACT and CMB S4. This will provide constraints for galaxy formation and feedback models.
Sep 29, Thursday
4:00 pm (Astronomy Colloquium)
Joop Schaye, Leiden
Le Conte
Simulating the formation of galaxies
The realism of hydrodynamical simulations of the formation and evolution of populations of galaxies has improved considerably in recent years. I will try to give some insight into the reasons behind this success, focusing in particular on the importance of subgrid models and the associated limitations. I will also present recent results from the cosmological EAGLE simulations as well as from other projects.

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