Observational Measures of Halo Properties Beyond Mass

Peter Behroozi

Department of Astronomy and Steward Observatory, University of Arizona

Abstract: Different properties of dark matter haloes, including growth rate, concentration, interaction history, and spin, correlate with environment in unique, scale-dependent ways.  While these halo properties are not directly observable, galaxies will inherit their host haloes’ correlations with environment.  As a result, measures of environment have the potential to reveal how galaxy properties are correlated with halo properties beyond halo mass.  We show preliminary results that different halo properties imprint distinct scale-dependent signatures in both the two-point correlation function and the distribution of distances to kth nearest neighbors.  We show that these signatures are strong, and are accessible even with low-resolution (e.g., grism) spectroscopy at higher redshifts.  Comparing observed two-point correlation functions for large and small galaxies at z=0, we use these results to show that classic galaxy size models (i.e., galaxy size being proportional to halo spin) cannot be correct.  Instead, we find that models where galaxy size depends inversely on concentration are a better match to observations.

یکشنبه 30 شهریور 1399، ساعت 19:00

Sunday 20 September 2020 – 19:00 Tehran Time

اتاق سمینار مجازی –Virtual Seminar Room

https://vc.sharif.edu/ch/cosmology

گزینه ورود به صورت مهمان – Enter as a Guest

Cosmological parameters from cosmic dynamics: new methods based on voids and flows

Guilhem Lavaux

Institut d’Astrophysique de Paris (IAP)

Abstract: Cosmology is in a golden age. The present paradigms are sufficiently firm to derive a large number of results on the universe, the data is becoming abundant and we have computers to analyze them. However some clouds are gathering at the horizon. There is an increase in tension on the Hubble constant, the properties of the hypothetical dark energy are still largely unconstrained and we will soon face an over-abundance of data which will reduce statistical errors to a negligible amount. Standard analyses have been relying a lot on statistics of the 2-point correlation function, which is not capable of handling well systematic effects. As such, we should look at other old and new probes of cosmology. I will discuss two probes of the dynamics to which I contributed significantly: the use cosmic voids to probe expansion, and the reconstruction of cosmic velocities to constrain the strength of gravity. We will see how the ideas have grown, and expanded recently and some new promising results concerning the reconstruction aspects.

دوشنبه 24 شهریور 1399، ساعت 19:00

Monday 14 September 2020 – 19:00 Tehran Time

اتاق سمینار مجازی –Virtual Seminar Room

https://vclass.ecourse.sharif.edu/ch/cosmology

گزینه ورود به صورت مهمان – Enter as a Guest

Testing MOG theory and CDM model at galactic and cosmic scales using observational data

Zahra Davari

Physics Department Sharif University of Technology

Abstract: In this talk, I will discuss one of the alternative theories to dark matter named MOdified Gravity (MOG) on both the galactic and cosmic scales.

 In the first part, I have investigated MOG theory and dark matter model by testing their ability to describe the local dynamics of the Milky Way in vertical and transverse directions by using observation data such as the vertical dispersion, rotation curve, surface density, and number density of stars.
The results show that two models of MOG and CDM are able to describe equally well the rotation curve and the vertical dynamics of stars in the local MW.
In the second part, I characterize the main aspects of the MOG theory at cosmological scales, analyzing the Friedmann equations and the expressions of the scalar fields of the theory. I use data from the binned Pantheon SNIa dataset,  Cosmic Chronometers (CC), and Big Bang Nucleosynthesis to test MOG predictions and comparing to the LCDM model.

یکشنبه 16 شهریور 1399، ساعت 19:00

Sunday 6 September 2020 – 19:00 Tehran Time

اتاق سمینار مجازی –Virtual Seminar Room

https://vclass.ecourse.sharif.edu/ch/cosmology

گزینه ورود به صورت مهمان – Enter as a Guest

Causal Set Theory and Cosmology

Yasaman Yazdi

Theoretical Physics Group, Blackett Laboratory, Imperial College London

Abstract: Causal sets are fundamentally discrete structures proposed to underlie spacetime. A causal set is made of ‘atoms’ of spacetime related according to the causal relations between them. Causal structure, discreteness, covariance, and nonlocality play a prominent role in the physics described by causal sets, including cosmology. Causal set theory has touched on a number of fundamental cosmological questions. These range from the cosmological constant problem to the origin of cosmological horizon entropy. In this talk I will review some of these studies and highlight how the unique features of causal sets come into play.

یکشنبه 2 شهریور 1399، ساعت 19:00

Sunday 23 August 2020 – 19:00 Tehran Time

اتاق سمینار مجازی –Virtual Seminar Room

https://vclass.ecourse.sharif.edu/ch/cosmology

گزینه ورود به صورت مهمان – Enter as a Guest

The Cosmological principle and the frame that never was

Mohamed Rameez

Niels Bohr Institute, University of Copenhagen

Abstract: The largest anisotropic feature of the Cosmic Microwave Background is the dipole, believed to originate from the relative motion of the heliocentric frame with a velocity of ~369 km/s with respect to the ‘rest frame of the Universe’ in standard cosmology. This should cause a dipolar modulation in the number counts of distant sources, through special relativistic aberration and Doppler boosting effects. We test this with various all-sky catalogues: NVSS and SUMSS radio galaxies, WISE galaxies and AGNs as well as GAIA-unWISE AGNs and consistently find a significantly larger dipole than expected, implying velocities > 1000 km/s at conservative statistical significances as high as 3.3 sigma. These and other observations hint at a bulk flow of matter in the local Universe, extending out to scales larger than is typical in \Lambda CDM N-body simulations. Convergence to the CMB rest frame has never been demonstrated. An observational effect of such a bulk flow would be a scale dependent dipolar modulation in the deceleration parameter. We look for this in the SDSS-II/SNLS-III Joint lightcurve analysis compilation of SN1a data and find such a modulation at ~3.9 sigma statistical significance, while the evidence for any isotropic acceleration of the Universe simultaneously drops to <1.4 sigma. These observations suggest that dark energy is an artefact of our idealized cosmological model.

یکشنبه 26 مرداد 1399، ساعت 19:00

Sunday 16 August, 2020 – 19:00 Tehran Time

اتاق سمینار مجازی –Virtual Seminar Room

https://vclass.ecourse.sharif.edu/ch/cosmology

گزینه ورود به صورت مهمان – Enter as a Guest

Loop quantum gravity and black hole interior

سعید راستگو

Saeed Rastgoo

Department of Physics and Astronomy, University of York

Abstract: Loop Quantum Gravity (LQG) is one of the few main top-down approaches to the quantization of spacetime that originated from the gravitation community.  It has various predictions regarding quantum cosmology and quantum black holes. This talk is divided into two parts. In the first part I will briefly explain what  LQG is all about and what are its main general predictions. In the second part, I will concentrate on black holes and sketch how this theory quantizes the interior of the Schwarzschild black hole and predicts the resolution of its classical singularity and a bounce to a white hole.

یکشنبه 19 مرداد 1399، ساعت 19:00

Sunday 9 August, 2020 – 19:00 Tehran Time

اتاق سمینار مجازی –Virtual Seminar Room

https://vclass.ecourse.sharif.edu/ch/cosmology

گزینه ورود به صورت مهمان – Enter as a Guest

Late time universe as a probe of cosmic origins

آزاده مرادی نژاد دیزگاه

Azadeh Moradinezhad Dizgah

Department of theoretical physics, University of Geneva

**لطفا  به ساعت نامتعارف سمینار توجه فرمایید** 

Abstract: The non-Gaussianity of the initial conditions leaves its imprints on the large scale structure. While the upcoming galaxy surveys will provide data with an unprecedented volume and precision, a novel observational technique referred to as line intensity mapping is also attracting significant amount of attention, given its unique potential to probe the universe at the range of scales and redshifts not accessible to galaxy surveys. In this talk, I will discuss a few different aspects of using these two observational windows to constrain primordial non-Gaussianity. In particular, I’ll discuss (a) the prospects of intensity mapping with CO and [CII] emission lines and its synergies with galaxy surveys, (b) the impact of modes larger than the size of a given survey on the measurement of clustering statistics within the survey, (c) the optimal estimators to extract information from clustering bispectrum.

یکشنبه 12 مرداد 1399، ساعت 19:00

Sunday 2 August, 2020 – 19:00 Tehran Time

اتاق سمینار مجازی –Virtual Seminar Room

https://vclass.ecourse.sharif.edu/ch/cosmology

گزینه ورود به صورت مهمان – Enter as a Guest

The dark matter distribution from simulations and observations

نسیم بزرگنیا

Nassim Bozorgnia

Department of Physics and Astronomy University of York

**لطفا  به ساعت نامتعارف سمینار توجه فرمایید**

Abstract: High resolution cosmological simulations of galaxy formation are powerful tools, which provide important information on the properties of the dark matter halo. Combined with the information obtained from the second data release of the Gaia satellite, simulations can significantly improve our understanding of the dark matter distribution in the Solar neighborhood. Determining the local dark matter velocity distribution is crucial for the correct analysis and interpretation of data from dark matter direct detection experiments. I will discuss the local dark matter distribution of Milky Way-like galaxies extracted from state-of-the-art hydrodynamic simulations, and present an analysis of direct detection data using this distribution. I will also discuss the properties of the dark matter component of the radially anisotropic stellar population recently discovered in the Gaia data, using the Auriga simulations. In particular, I will present the local dark matter density and velocity distributions of the simulated Milky Way-like galaxies with and without the anisotropic substructure, and discuss their implications for dark matter direct detection.

یکشنبه 5 مرداد 1399، ساعت 19:00

Sunday 26 July, 2020 – 19:00 Tehran Time

اتاق سمینار مجازی –Virtual Seminar Room

https://vclass.ecourse.sharif.edu/ch/cosmology

گزینه ورود به صورت مهمان – Enter as a Guest

کارگاه مجازی تارکیهان و شبیه‌سازی‌های کیهانی

دکتر علی اکبر ابوالحسنی
دکتر شانت باغرام
محمد انصاری فرد
احسان ابراهیمان
حامد منوچهری
سینا هوشنگی
سینا تاملی
زهرا باغخانی
لعیا قدسی

زمان : پنج‌شنبه  ۲ مرداد ماه ۱۳۹۹
https://vclass.ecourse.sharif.edu/ch/cosmology 

در خواست جهت ثبت نام در کارگاه و اطلاعات بیشتر:

m.ansari1373=AT=gmail.com

برنامه کارگاه

چکیده سخنرانی‌ها

Gravitational microlensing and pulsing stars

صدیقه سجادیان

Sedighe Sajadian

Department of physics, Isfahan University of Technology (IUT)

Abstract: Gravitational microlensing refers to the temporary enhancement in the stellar brightness due to the gravitational effect of a collinear massive object. In this talk, I will explain the microlensing of pulsing stars. Discerning and characterizing the properties of distant, faint pulsating stars are achievable through high-cadence microlensing observations. Mutually, combining stellar variability period with microlensing gives the source distance, type, and radius and helps better determine the lens parameters. For radial pulsing stars, considering periodically variations in their radius and surface temperature, their microlensing light curves are resulted from multiplication of the magnification factor with variable finite size effect by the intrinsic brightness curves of the pulsing source. Whereas, for non-radial pulsing stars, the light curve is not a simple multiplication of the magnification curve and the interstice luminosity curve of the source star, unless the effect of finite source size can be ignored. Other properties of microlensing light curves from pulsing stars will be discussed in the talk.

یکشنبه 29 تیر 1399، ساعت 17:00

Sunday 19 July, 2020 – 17:00 Tehran Time

اتاق سمینار مجازی –Virtual Seminar Room

https://vclass.ecourse.sharif.edu/ch/cosmology

گزینه ورود به صورت مهمان – Enter as a Guest