Maryam Saberi

Rosseland Centre for Solar Physics, University of Oslo

Institute of Theoretical Astrophysics, University of Oslo

UV chemistry in the circumstellar envelopes around evolved stars

Abstract: Low- and intermediate-mass stars (M < 8M☉) evolve towards the asymptotic giant branch (AGB) phase, where they eject a substantial amount of their material (up to 80%) into the interstellar medium (ISM). Therefore, AGB stars play a significant role in the galactic chemical evolution by ejecting the synthesised elements to the ISM through strong stellar winds. An extended circumstellar envelope (CSE) will be created around the star as a consequence of the intense mass loss. Observations of molecular species and dust content in CSEs help us to broaden our knowledge on mass-loss process, stellar properties, and the CSE chemistry. In this presentation, I will give an introduction to the CSE chemistry with a focus on the ultraviolet (UV) chemistry. Then, I will show how high spectral and spatial resolution observations of the Atacama large millimetre array (ALMA) can help us to quantify the impact of various sources of UV radiation in the CSE chemistry around evolved stars.

یکشنبه 12 اردیبهشت 1400، ساعت 19:00

Sunday 2 May 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

Dragan Huterer

Department of Physics, University of Michigan

Mapping the Universe with Dark Energy Survey

Abstract: I will briefly review how progress in cosmology over the past two decades has greatly improved our measurements of dark-energy parameters, yet has not really shed light on the physical nature of this component. Then I will discuss measurements of cosmological parameters from the Dark Energy Survey. In particular, I will concentrate on the so-called “3×2” correlation-function measurements, and technical innovations in year 1 and the forthcoming year-3 analysis. I will highlight results that are most interesting to general-purpose cosmologists.  Finally, I will highlight how these and other upcoming measurements of dark energy will help us better understand the physical mechanism behind the accelerating universe.

یکشنبه  5 اردیبهشت 1400، ساعت 19:00

Sunday 25 April 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

The mystery of the distance of galaxies that apparently lacking dark matter

Hosein Haghi

Physics Department, Institute for advanced studies in basic sciences (IASBS)

Abstract: Recently, van Dokkum et al. reported the detection of a couple of ultra-diffuse dwarf (UDG) galaxies lacking dark matter (NGC 1052-DF2 and NGC 1052-DF4). If correct, this could be one of the most important discoveries in Extragalactic Astrophysics and represents a possible challenge to our understanding of the properties of these galaxies and galaxy formation in general. They used surface brightness fluctuation technique yielding a distance of about 20 Mpc implying these galaxies to be dark matter deficient with the larger than expected size, and brighter and larger than expected globular clusters system. But, if the galaxy is a factor of two or three closer to us than the adopted distance of 20 Mpc nearly all the unusual properties vanish. Several authors asked whether these galaxies could be at a smaller distance. Different distance measurement methods that have been applied on these galaxies so far, yielding a distance in the range 10 to 20 Mpc implying it to be “normal” or “dark matter deficient” galaxies. In this talk, first, I will briefly review the current challenge in determining the distance of these galaxies. Then, I will give you a brief report on our recent publication on the IMF-induced intrinsic uncertainties on measuring the ultra-diffuse galaxy distances based on the surface brightness fluctuation technique. 

یکشنبه 22 فروردین 1400، ساعت 19:00

Sunday 11 April 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

Tracing the stellar mass assembly within galaxies over the past 10 Gyr

Moein Mosleh

Biruni Observatory, School of Science, Shiraz University 

Department of Physics, School of Science, Shiraz University

Abstract: One of the important questions in galaxy formation and evolution is to understand how the stellar mass has been assembled within galaxies. The formation of prominent central densities known as bulges is an example of this evolution and the true mechanisms behind this transformation are a matter of debate. In this talk, I will overview the importance of addressing this question and describe the observational methods that we used for tracing the assembly of stellar mass within galaxies. I will also explain how we can benefit from studying the scaling relations such as size-mass relations. In addition, possible connections of the structural evolutions with star-formation activities and environments will be discussed.

یکشنبه 24 اسفند 1399، ساعت 19:00

Sunday 14 March 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

Primordial Black Holes and Gravitational Waves

Antonio Riotto

Department of Theoretical Physics, University of Geneva

 Abstract:  We will discuss the relation between primordial black holes and gravitational waves in the view of the recent Ligo/Virgo and NanoGrav data.

سه شنبه 19 اسفند 1399، ساعت 19:00

Tuesday 9 March 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

The Hubble-constant crisis

Valerio Marra

Núcleo de Astrofísica e Cosmologia & Departamento de Física, Universidade Federal do Espírito Santo, Brazil

 INAF – Osservatorio Astronomico di Trieste, Italy.

IFPU – Institute for Fundamental Physics of the Universe, Italy.

Abstract:  The determination of the Hubble constant H0 – the present-day expansion rate of the universe – is one of the key goals of cosmology, for it impacts all measurements of cosmological properties. Determinations of H0 from Cosmic Microwave Background observations disagree with local determinations from calibrated supernovas Ia: this tension is now approaching the 5 sigma level. After reviewing the present status of cosmology, I will present recent work on model-independent determinations of H0 and their implications for cosmologies beyond LCDM.

سه شنبه 12 اسفند 1399، ساعت 13:30

Tuesday 2 March 2021 – 13:30 Tehran Time

اتاق سمینار مجازی –Virtual Seminar Room

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

گزینه ورود به صورت مهمان – Enter as a Guest

Tracing the galaxy evolution and morphologies using the DM and Stellar halo from the cosmological hydrodynamical simulations of TNG

Razieh Emami

Institute for Theory and Computation

Harvard-Smithsonian Center for Astrophysics

Abstract:  One of the fundamental questions about the galaxy evolution is the redshift evolution of the galaxy morphology as traced by DM and stars. Tracking the galaxy morphology enables us to shed light about how the galaxies are evolved with time and also to connect the visible matter, traced by stars, with the invisible matter, DM. In this talk, we will use the next generation (TNG) of cosmological simulations and study the morphology of DM and stars in a sample of Milky Way like galaxies at zero redshift. We will also present how does the galaxy morphology vary with the time. It is intriguing to investigate how does the major mergers affect the galaxy morphology.

یکشنبه 3 اسفند 1399، ساعت 19:00

Sunday 21 February 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

A conclusive test of the cold dark matter model

Carlos Frenk

Institute for Computational Cosmology, Durham University

Abstract:  The “Lambda cold dark matter” (LCDM) cosmological model is one of the great achievements in Physics of the past thirty years. Theoretical predictions formulated in the 1980s turned out to agree remarkably well with measurements, performed decades later, of the galaxy distribution and the temperature structure of the cosmic microwave background radiation. Yet, these successes do not inform us directly about the nature of the dark matter. Indeed, there are competing (and controversial) claims that the dark matter may have already been discovered, either through the annihilation of cold, or the decay of warm, dark matter particles. In astrophysics the identity of the dark matter manifests itself clearly on subgalactic scales, including the dwarf satellite galaxies of the Milky Way and especially less massive dark matter halos, too small to have made a galaxy.  I will discuss predictions from cosmological simulations assuming cold and warm (in the form of sterile neutrinos) dark matter, including for the properties of the very first halos that ever formed, and show how forthcoming astronomical observations can conclusively distinguish between the two.

یکشنبه 26 بهمن 1399، ساعت 19:00

Sunday 14 February 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

Characterizing the non-linear evolution of dark energy models

Farbod Hassani

Institute of theoretical astrophysics of the University of Oslo

Abstract: Understanding the reason behind the observed accelerating expansion of the Universe is one of the most notable puzzles in modern cosmology, and conceivably in fundamental physics. In the upcoming years, near future surveys will probe structure formation with unprecedented precision and will put firm constraints on the cosmological parameters, including those that describe properties of dark energy. In light of this, during past years I mainly focused on precision cosmology by characterizing the non-linear evolution of cosmological components using N-body simulations. In this talk, first I will introduce gevolution and the idea of developing EFT-evolution N-body code, in which we consistently study the dark matter and dark energy structures up to non-linear scales. Then I will discuss the consequences of clustering dark energy on cosmological observables.

 یکشنبه 19 بهمن 1399، ساعت 19:00

Sunday 7 February 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