همه‌ی نوشته‌های MojahedParsi

Formation of Multiple Stellar Populations in globular clusters

25 فوریه 2023 MojahedParsi دیدگاه‌تان را بنویسید:

Asiyeh Yaghoobi

Department of Physics, Ferdowsi University of Mashhad

Formation of Multiple Stellar Populations in globular clusters

Abstract: Globular clusters (GCs) can provide useful information from the early star-forming subsystems to study the formation history of their parent galaxies. They are composed of low-metal ([Fe/H] <1), low-mass (< 0.8 Msun), and old (> 10 Gyr) stars. Traditionally, it was assumed that all stars in GCs have similar chemical compositions to the initial cloud from which GCs and host galaxies have already been formed. However, recent observations have revealed that stars within GCs display anomalous variations in light elements (e. g. He, C, N, O, Na, Al, and sometimes Mg) that are not expected to occur inside the low-mass stars of GCs. These populations with anomalous abundance variations in GCs are known as “Multiple Stellar Populations” (MSPs) or second generation (SG), and their formation is still shrouded in mystery. In this talk, I investigate the formation of MSPs within young clusters using 3D hydrodynamical simulations in the context of the asymptotic giant branch (AGB) scenario. I will start by introducing the AGB model and then explain some proposed problems for this scenario, such as ram pressure and ionizing radiation. After that, I will present our most important results based on the two papers below. Our results imply that the formation of SG stars in the AGB scenario needs to occur within massive star clusters located in dense environments, consistent with properties of the ambient surrounding of GCs in star-forming disk galaxies observed at redshift z > 2.

https://ui.adsabs.harvard.edu/abs/2022MNRAS.517.4175Y/abstract
https://ui.adsabs.harvard.edu/abs/2022MNRAS.510.4330Y/abstract

یکشنبه 7 اسفند 1401، ساعت 17:00

Sunday 26 February 2023 – 17:00 Tehran Time

Hybrid Seminar

آمفی تئاتر دانشکده فیزیک-تالار جنابPhysics Department – Amphitheater- Jenab Hall/

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

گزینه ورود به صورت مهمان – Enter as a Guest

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دفاع کارشناسی ارشد

19 فوریه 2023 MojahedParsi دیدگاه‌تان را بنویسید:

Mohammad Reza Ebrahimi

Department of Physics, Sharif University of Technology

Simulation of Structure Formation in the presence of Fuzzy Dark Matter using Gevolution Code

Supervisor: Ali Akbar Abolhasani

Abstract: In this thesis, the formation of cosmic structures in the presence of fuzzy dark matter (FDM) is investigated using the Gevolution code. In the FDM model, dark matter is composed of ultralight bosons. In fact, the mentioned bosons are the remnants of a scalar field present in the early universe. Simulations of structure formation in the presence of FDM that have been carried out so far (for example with Gadget and RAMSES) are based on Newtonian gravity, which have a number of limitations. The Gevolution code is an N-Body simulation that, unlike other existing simulations, is based on General Relativity, which can lead to interesting results. In fact, in this simulation, the weak field limit in General Relativity is looked at and metric degrees of freedom are calculated. Other advantages of Gevolution code are higher simulation speed and less hardware limitations. In addition, in this code, a number of theories can be studied.

یکشنبه 26 بهمن 1401، ساعت 17:00

Sunday 19 February 2023 – 17:00 Tehran Time

تالار جناب – آمفی تئاتر دانشکده فیزیک

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Is gravity the only dark matter interaction that matters in the physics of galaxies?

2 اکتبر 2021 MojahedParsi دیدگاه‌تان را بنویسید:

Jesus Zavala Franco

Centre for Astrophysics and Cosmology at the University of Iceland

Is gravity the only dark matter interaction that matters in the physics of galaxies?

Abstract: One of the most relevant problems in Physics is to identify new particles beyond the Standard Model, which can fit the properties of the cosmological dark matter. Despite decades of searching for candidates, the nature of dark matter remains a mystery even though its role in explaining cosmic structure formation has become progressively more fundamental. Analysing the properties of the galaxy population is arguable among the most promising short-term avenues to look for clues to solve the dark matter enigma. In this talk, I will present a broad overview of the status of the allowed impact of new dark matter physics (i.e., beyond its gravity) in the physics of galaxies.

یکشنبه 11 مهر 1400، ساعت 19:00

Sunday 3 October 2021 – 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

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2 می 2020 MojahedParsi دیدگاه‌تان را بنویسید:

Halo formation in self-interacting dark matter models

امید سمیعی

Omid Sameie

Department of Astronomy, University of Texas Austin

**لطفا به ساعت نامتعارف سمینار توجه فرمایید**

Abstract: Strong dark matter interactions are proposed to alleviate the tension between observations and theoretical predictions in CDM. Among different interaction channels, self-interacting dark matter (SIDM) models have received considerable attention. However, most of the models and simulations have so far neglected the contribution of the baryons. First, I will present a combination of results from idealized SIDM simulations that explore the effect of a baryonic disk/bulge on the shape and density profile of dark matter halos. We find that the inclusion of baryons in these models help to alleviate two of the longstanding issues within CDM: i) the diversity of rotation curves on the scale of dwarf galaxies and ii) the high sphericity measured for the dark matter halo of our own Milky Way. The observations of Milky Way satellite galaxies have also revealed a large spread in their central dark matter densities. In the second part of my talk, I discuss how dark matter self-interactions plus environmental effects such as tidal stripping can reproduce the observed diverse central densities in the Milky Way dwarf spheroidal galaxies. In the third part of my talk I will discuss an analytical model to study the effects of dark matter-dark radiation interactions on the abundance of faint galaxies at high redshifts.

یکشنبه 14 اردیبهشت 1399، ساعت 18:00

Sunday 3 May, 2020 – 18:00 Tehran Time

اتاق سمینار مجازی –Virtual Seminar Room

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

گزینه ورود به صورت مهمان – Enter as a Guest

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