Matteo Viel

SISSA-International School for Advanced Studies,

INFN, Sezione di Trieste,

INAF – Osservatorio Astronomico di Trieste,

IFPU, Institute for Fundamental Physics of the Universe

Hydrogen as a tracer of cosmic structures: fundamental physics and astrophysical aspects

Abstract: I will review the use of neutral hydrogen (HI) in the post reionization era as a tracer of the structure formation process. I will focus on atomic hydrogen both in absorption (IGM) and in emission (21cm intensity mapping). IGM is a probe of HI in volume, while intensity mapping is sensitive to the HI mass distribution. This combined information is thus highly complementary. The IGM, diffuse matter between galaxies (the so-called cosmic web) allows to measure the matter perturbations down to small scales and at high redshift. In recent years, baryonic acoustic oscillations have been detected at high redshift and unprecedented tight constraints on dark matter nature and neutrino mass have also been obtained, using IGM data (mainly from low resolution BOSS and high resolution quasar spectra from HIRES/Keck). On the other hand, emission at 21cm will probe is going to be an important probe that will also probe structure formation at high redshift. The IGM and intensity mapping can be used to address fundamental physical questions like the nature of dark matter, neutrino masses, possible extension of the standard cosmological model, and offer important clues on the cosmic cycle of baryons and the galaxy/IGM interplay.

سه شنبه 11خرداد 1400، ساعت 19:00

Tuesday 1 June 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

https://www.psi.ir/farsi.asp?page=bookrelease1

Zahra Sattari

Department of Physics and Astronomy, University of California, Riverside

Evidence for Gas-phase Metal Deficiency in Massive Protocluster Galaxies at z ~2.2

Abstract: We study the mass-metallicity relation for 19 members of a spectroscopically confirmed protocluster in the COSMOS field at z=2.2 (CC2.2) and compare it with that of 24 similarly selected field galaxies at the same redshift. Both samples are Hα emitting sources, chosen from the HiZELS narrowband survey, with metallicities derived from the N2 ([NII]λ6584/Hα) line ratio. For the mass-matched samples of protocluster and field galaxies, we find that protocluster galaxies with 10^9.9 M⊙ ≤ M* ≤ 10^10.9 M⊙ are metal deficient by 0.10 ± 0.04 dex (2.5σ significance) compared to their coeval field galaxies. This metal deficiency is absent for low-mass galaxies, M* < 10^9.9 M⊙. Moreover, relying on both spectral energy distributions derived and Hα (corrected for dust extinction based on M*) star formation rates (SFRs), we find no strong environmental dependence of the SFR-M* relation; however, we are not able to rule out the existence of small dependence due to inherent uncertainties in both SFR estimators. The existence of 2.5σ significant metal deficiency for massive protocluster galaxies favors a model in which funneling of the primordial cold gas through filaments dilutes the metal content of protoclusters at high redshifts (z≳2). At these redshifts, gas reservoirs in filaments are dense enough to cool down rapidly and fall into the potential well of the protocluster to lower the gas-phase metallicity of galaxies. Moreover, part of this metal deficiency could be originated from galaxy interactions that are more prevalent in dense environments.

یکشنبه 2 خرداد 1400، ساعت 19:00

Sunday 23 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

Dear Colleagues, as you may know, a series of events are ongoing by the Astronomy Society of Iran. You can find the events on the web-page of the ASI

Please note that

* Friday   24 Ordibehesht / 14 May Professor Yousef Sobouti will be the guest of the program.

* Sunday 26 Ordibehesht / 16 May Professor Sohrab Rahvar will participate in a discussion on professional and amateur astronomy.

Also, there are two colloquiums in the Physics Departments of Tehran University and Sharif University as

*Nima Khosravi on “Cosmological tensions”- Saturday 25 Ordibehesht 1400 / 15 May 2021 @ 15:30 – UT – Please see the attachment.

*Shant Baghram on ” Cosmology’s century: Large scale structure of Dark Universe”-  Sunday 26 Ordibehesht 1400 / 16 May 2021 @ 13:30 – SUT – Please see the attachment.

Zeinab Kalantari

Department of Physics, Sharif University of Technology

Imprints of Gravitational Microlensing on the Light Curve of Gamma-Ray Bursts

Abstract: Gamma-ray bursts (GRBs) are one of the most luminous and prolific high-energy transients that have been observed since their discovery in 1963. The theoretical investigations of gravitational lensing of GRBs have been carried out in the past half-century. In this talk, I will briefly review of Gamma_Ray Bursts (GRBs) detections and GRBs progenitors. Next, I will give a general overview of gravitational microlensing and its observable signature on a GRB light curve for a point mass model of lens. Then, I will concentrate on the Autocorrelation method and its efficiency in finding microlensed candidates. Finally, I will highlight the results of our recent probe in the Fermi/GBM catalog and the estimation of the dark matter density parameter in the form of black holes in the Universe.

یکشنبه 26 اردیبهشت 1400، ساعت 15:00

Sunday 16 May 2021 – 15:00 Tehran Time

اتاق سمینار مجازی –Virtual Seminar Room

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

گزینه ورود به صورت مهمان – Enter as a Guest

Martin Kunz

Department of Theoretical Physics and Center for Astroparticle Physics, University of Geneva

A brief introduction to Euclid and what we can learn from it 

Abstract: Euclid is an ESA medium class astronomy and astrophysics space mission. Euclid was selected by ESA in October 2011 and its launch is planned for 2022. Euclid will explore how the Universe evolved over the past 10 billion years to address questions related to fundamental physics and cosmology on the nature and properties of dark energy, dark matter and gravity. Euclid will also provide insightful information on the physics of the early universe and on the initial conditions which seed the formation of cosmic structure.

I will give a brief general overview of the Euclid satellite and its mission, and describe the main probes and how they observe the evolution of the Universe. Focusing particularly on dark energy models, I will then briefly review what we know now, and how Euclid will improve our knowledge.

یکشنبه 19 اردیبهشت 1400، ساعت 19:00

Sunday 9 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

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