Astrophysics Seminar

"Astrophysics Seminar: Upper limits on the Epoch of Reionization from LOFAR"

Location: 
Kaplun building, Room No. 200
Tue, 03/03/2015 - 12:30 to 13:30

Lecturer: Prof. Saleem Zaroubi Affiliation: University of Groningen Abstract: The Epoch of Reionization marks one of the last major phase transitions in the Universe. Our understanding of this period is very limited with most of the details of the process are still unknown. The redshifted 21 cm radiation from neutral hydrogen provides one of the most promising probes of the EoR. Currently, there are a number of telescopes in the world targeting this radiation. In this seminar I will talk about recent results from The LOw Frequency ARray, LOFAR,

Astrophysics Seminar: "The growth and death of galaxies: MAD Science"

Location: 
Kaplun building, Room No. 200
Tue, 08/12/2015 - 12:30 to 13:30

Lecturer: Prof. Marcella Carollo Affiliation: ETH, Zurich Abstract: I will summarize a number of results on the growth of mass and size of galaxies with time, and discuss a perspective that provides a unified answer to three major open questions in galaxy evolution, namely: (1) How do massive galaxies quench their star formation activity? (2) How do quenched galaxies grow their dense bulges? (3) What causes the observed growth with time of the average size of the quenched galaxy population? I will conclude with a look ahead on the MUSE Atlas of Disks (MAD), a just-

"Astrophysics Seminar: A New Look at AGN Accretion Discs and Black Hole Spin"

Location: 
Kaplun building, Room No. 200
Tue, 21/04/2015 - 12:30 to 13:30

Lecturer: Dr. Daniel Capellupo Affiliation: Tel-Aviv University Abstract: At the center of every active galactic nucleus (AGN) is a supermassive accreting black hole (BH). The physics of active BHs is governed by three key parameters: their mass, spin, and accretion rate. We therefore observe a sample of z ~ 1.5 AGN, selected to cover a wide range in BH mass and accretion rate, with X-shooter on the VLT. Using this unique dataset, we test models of AGN accretion discs and find that most of the observed spectral energy distributions (SEDs) can be

"Astrophysics Seminar: A critical phase in galaxy formation"

Location: 
Kaplun building, Room No. 200
Tue, 24/02/2015 - 12:30 to 13:30

Lecturer: Dr. Greg Stinson Affiliation: MPIA Heidelberg Abstract: As galaxies grow and evolve, they go through a violent phase of their evolution where intense star formation drives outflows. I will examine this phase using cosmological galaxy formation simulations. The simulations show that starbursts and outflows have implications for many observed properties of galaxies including their gaseous halos, morphology, potential, and star formation history. Additional details of the upcoming Astrophysics'

Astrophysics Seminar: "Unraveling GRB 060218"

Location: 
Kaplun building' Room No. 200
Tue, 16/02/2016 - 12:30 to 13:30

Lecturer: Dr. Christopher Irwin Affiliation: The University of Virginia Abstract: We consider a model for the long-duration, low- luminosity gamma-ray burst GRB 060218 that plausibly accounts for multiwavelength observations to day 20. The components of our model are: (1) a long-lived (t ~ 3000 s) central engine and accompanying low-luminosity (L ~ 1e47 erg/s), mildly relativistic jet; (2) a low- mass (~ 1e-2 Msun ) envelope surrounding the progenitor star; and (3) a modest amount of dust (A_V ~ 0.1) in the circumstellar or interstellar environment. Blackbody emission

"Astrophysics Seminar: Electromagnetic Counterparts to Gravitational Waves"

Location: 
Kaplun building, Room No. 200
Tue, 30/06/2015 - 12:30 to 13:30

Lecturer: Prof. K. Ioka Affiliation: The High Energy Accelerator Research Organization, KEK Abstract: Direct detection of gravitational waves (GWs) is on the horizon, with the most promising sources being the mergers of two neutron stars (NS-NS) or a black hole and a neutron star (BH-NS). Maximizing the scientific return of this new window into the universe requires identifying a coincident electromagnetic (EM) counterpart. One probable EM counterpart is a short gamma-ray burst (GRB) but the emission is highly collimated. Isotropic EM emissions are also suggested by the general

"Astrophysics Seminar: Pair-instability supernova progenitors with large mass loss"

Location: 
Kaplun building, Room No. 200
Thu, 22/01/2015 - 14:00 to 15:00

Lecturer: Dr. Takashi Moriya Affiliation: University of Bonn Abstract: Pair-instability supernovae (PISNe) are thermonuclear explosions of very massive stars. The stellar core needs to be heavier than about 60 Msun for stars to be PISNe. Mass loss prevents massive stars from making large enough cores to be PISNe, and PISNe are presumed to exist in metal-free or metal-poor environment where radiation-driven mass loss is small. Stellar evolution models show that such PISN progenitors evolve to red supergiants (RSGs) shortly before their explosions. However, RSGs are suggested to be

Astrophysics Seminar: "Dynamics and evolution of planetesimals in gaseous protoplanetary disks - the role of gas dynamical friction"

Location: 
Kaplun building, Room No. 200
Tue, 12/04/2016 - 12:30 to 13:30

Lecturer: Mr. Evgeni Grishin Affiliation: Technion - Israel Institute of Technology Abstract: The growth of small planetesimals into large planetary embryos occurs much before the dispersal of the gas from the protoplanetary disk. The planetesimal - disk interactions cause migration and orbital evolution of the planetesimals/planets. Small planetesimals are dominated by aerodynamic gas drag. Large protoplanets, >1000km in size, are dominated by type I migration torque. There is an additional size range, 200- 1000 km, of intermediate mass

"Astrophysics Seminar: Astrometric mock observations for determining the local dark matter density"

Location: 
Kaplun building, Room No. 200
Tue, 24/11/2015 - 12:30 to 13:30

Lecturer: Dr. Shigeki Inoue Affiliation: Racah Institute of Physics, The Hebrew University of Jerusalem Abstract: It is a classical problem in astronomy to determine the local dark matter density (LDMD) of the solar system. The DM density at the solar radius can be estimated from the Galactic rotation curve using a spherical assumption for the dark matter halo. However, dark matter haloes are generally aspherical, therefore the DM density deduced from the rotation curve can differ from the LDMD around the solar system. In other words, the difference between

"Astrophysics Seminar: Investigating the links between galaxy structure and environment in the high redshift Universe"

Location: 
Kaplun building, Room No. 200
Tue, 14/04/2015 - 12:30 to 13:30

Lecturer: Dr. Caterina Lani Affiliation: Tel-Aviv University Abstract: It has been long known that, in the local Universe, galaxy morphology is strongly related to environment. Furthermore, massive passive galaxies were observed to be 2 - 4 times more compact at z ~ 2 compared to the present day. Environment, in the form of mergers, halo mass and interactions, could explain the observed size increase as well as morphological transitions. I will present compelling evidence for a strong correlation between galaxy size and environment to z ∼

"Astrophysics Seminar: Detecting gravitational waves with small systems: future relativistic quantum technologies"

Location: 
Kaplun building, Room No. 200
Tue, 02/12/2014 - 12:30 to 13:30

Lecturer: Dr. David Edward Bruschi Affiliation: Racah Institute of Physics, Hebrew University of Jerusalem Abstract: The field of quantum information has reached the point where commercial applications are being developed. Although quantum mechanics has proven to be very successful as the core for quantum information, it is still unknown how relativity enters the game. Cutting edge experiments are now reaching regimes where effects at the overlap between quantum and relativistic theories can be investigated. Therefore, it seems natural to

Astrophysics Seminar: "Balmer-dominated shocks around supernova remnants SN1006 and Tycho"

Location: 
Kaplun building, Room No. 200
Tue, 09/02/2016 - 12:30 to 13:30

Lecturer: Dr. Sladjana Knezevic Affiliation: Weizmann Institute of Science Abstract: I will present high-resolution spectrophotometric imaging of Balmer- dominated shocks (BDSs) around two historical supernova remnants, SN1006 and Tycho. BDSs are characterized by strong hydrogen emission lines with a narrow (~10 km/s) and a broad (~ 1000 km/s) component. The emission originates very close to the shock front and provides several important diagnostics for the physical processes in fast collisionless shocks. The line shapes and their spatial profiles are used

"Astrophysics Seminar: Structure and Properties of the Intra-Cluster Medium and the Role of Gas Streams"

Location: 
Kaplun building, Room No. 200
Tue, 02/06/2015 - 12:30 to 13:30

Lecturer: Mr. Elad Zinger Affiliation: Racah Institute of Physics, The Hebrew University of Jerusalem Abstract: We discuss the structure and properties of galaxy clusters with an emphasis on the dynamical state of the clusters. We show that inflowing gas streams play an important role in determining the properties of the ICM and whether a cluster is dynamically relaxed or disturbed. In addition, collisions of inflowing streams are shown to be a viable mechanism for generating shocks and 'Cold Fronts' in the ICM. The hot ICM, found behind the virial

"Astrophysics Seminar: A Cabinet of Curiosities in Near-Field Cosmology"

Location: 
Kaplun building, Room No. 200
Tue, 06/01/2015 - 12:30 to 13:30

Lecturer: Prof. James Peebles Affiliation: Princeton University Abstract: The LCDM cosmology is well established but certainly not the final theory of what happened as the universe expanded and cooled. I will review phenomenology on the scale of galaxies that seem to me to challenge LCDM and perhaps offer clues to a still better cosmology. Additional details of the upcoming Astrophysics' seminars can be found on the following link.

Astrophysics Seminar: "Could UHECRs originate from GRBs?"

Location: 
Kaplun building, Room No. 200
Tue, 29/03/2016 - 12:30 to 13:30

Lecturer: Dr.Noemie Globus Affiliation: Racah Institute of Physics, The Hebrew University of Jerusalem Abstract: Could UHECRs originate from gamma-ray bursts? To explore that very question, we performed numerical calculations of UHECRs accelerated at GRB internal shocks, taking into account all the relevant energy loss mechanisms. For various choices of the GRB parameters, we calculated the spectrum of cosmic rays escaping from the GRB environment as well as secondary particles produced either during the acceleration or extragalactic propagation. I will discuss the