Agenda de Lagrange

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Novembre 2017

Séminaire Lagrange
What sets the central density structure of dark matter halos?
 mardi 7 novembre 2017, 10h30, NEF - Mont Gros - CION - talk in english - retransmis à Valrose
Go Ogiya - Lagrange, OCA
Dark matter (DM) halos near the free-streaming cutoff scale of the density perturbations provide important hints to understand the formation and evolution of cosmic structures because they are the progenitors of
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    all larger systems formed later. Recent simulations have found when the free-streaming cutoff is resolved, the central density structure of DM hales near the scale, formed through monolithic collapse, follows the r^{-a} profile with a=1.5, which is steeper than that of the universal Navarro-Frenk-White (NFW) model with a=1, and the slope becomes shallower as their masses grow. We study the formation and evolution of the DM halos using idealized N-body simulations of the collapse of proto-halo patches and of mergers between DM halos of the a=1.5 profile. We find (i) the density core formed by the free-streaming motion in the center of patches leads the rapid collapse and leads DM to free fall motion to form the a=1.5 profile (Ogiya & Hahn 2017); and (ii) mergers drive the slope to approach that of the NFW model which is robust to mergers and serves an attractor solution for the density structure of DM halos (Ogiya et al. 2016).
Séminaire Lagrange
Histoire de la Nucléosynthèse stellaire
 mardi 14 novembre 2017, de 10h00 à 12h00, NEF - Mont Gros - CION - présentation en français - retransmis à Valrose
Nicolas Prantzos - IAP
Séminaire Lagrange
Getting ready for JWST with new-generation spectral models and interpretation tools
 mardi 21 novembre 2017, 10h30, NEF - Mont Gros - CION - talk in english - retransmis à Valrose
Jacopo Chevallard - ESTEC
The James Webb Space Telescope (JWST), scheduled for launch in October 2018, will open a largely unexplored observational window at near- to mid-infrared wavelengths (0.6-28 micron). In particular, the Near-InfraRed Spectrograph
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    (NIRSpec) on board JWST will allow the detection of standard UV and optical emission lines out to redshift ~ 10 and beyond for large samples of galaxies. This will provide unique insight into, for example, the star formation activity and early chemical enrichment of galaxies, the co-evolution of galaxies and AGNs, the impact of stellar and AGN feedback, and the main drivers of cosmic reionization. One of the first large programs to exploit the new observational capabilities of JWST will be the NIRSpec Guaranteed-Time-Observations (GTO) program, which includes a multi-layered survey in Multi-Object-Spectroscopy (MOS) mode targeting ~104 galaxies at 1.5 < z < 10, as well as an Integral-Field-Unit (IFU) survey targeting ~60 galaxies and AGNs out to z~9. In this talk, after a short review of JWST and the NIRSpec GTO program, I will present a set of physically-motivated simulations of NIRSpec and NIRCam (the Near-Infrared Camera on board JWST) observations, which we have used to optimise the survey design, and which will be made available to the community on time for the preparation of Cycle-1 General-Observer (GO) observations (call for proposals on 30/11/2017). I will also discuss a new set of state-of-the-art population synthesis+photoionization models, developed in collaboration with the NEOGAL team at the IAP, tailored to the interpretation of high-redshift galaxy observations. I will show how these models, incorporated into our new-generation analysis tool "Beagle", successfully reproduce a broad range of UV and optical features from high-quality spectra of nearby galaxies, as well as the high-ionization UV lines observed in galaxies at z > 6. The ability to self-consistently measure the physical properties of gas and stellar populations across a broad range of redshifts and stellar masses will be crucial to maximise the scientific return of JWST and gain unique insight into the evolution of galaxies across cosmic times.
Séminaire Lagrange
tba
 mardi 28 novembre 2017, 10h30, NEF - Mont Gros - CION - talk in english - retransmis à Valrose
Nicolas Gac - Université Paris Sud
tba.

Décembre 2017

Séminaire Lagrange
The Sphinx simulations: the first billion years and cosmic reionisation
 mardi 5 décembre 2017, 10h30, NEF - Mont Gros - CION - talk in english - retransmis à Valrose
Joakim Rosdahl - CRAL Lyon
The epoch of reionisation marks a major shift from a cold neutral Universe to a warm ionised one, a transition which was thought to be powered by UV radiation emitted from
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    young massive stars in the first galaxies. Our understanding of this epoch is still very limited: observationally we only glimpse a handful of the most luminous galaxies existing at the end of the epoch, but with the advent of the James Webb Telescope and other upcoming instruments we will soon start getting statistical information about the sources powering reionisation. Theoretically, the best way to gain an understanding is with cosmological simulations. However, those are very expensive, so either people simulate large patches of the reionising Universe without resolving the galactic sources, or go for tiny patches where the stellar sources inside one or a few galaxies are resolved, but the large-scale process is lost. I will present a new suite of simulations, called the Sphinx project, where we have developed new methods that allow us to perform radiation-hydrodynamical simulations of cosmic reionisation, resolving the emission and escape of radiation on parsec scales inside hundreds of galaxies all evolving together in the same patch of the Universe, hence capturing the interplay of small- and large-scale processes. I will describe the simulations and the key developments that make them possible, and show results from a pilot Sphinx study looking into the surprising impact of spectral energy distribution (SED) models containing binary populations on reionisation, compared to more classical SEDs.
Séminaire Lagrange
tbd
 mardi 12 décembre 2017, 10h30, NEF - Mont Gros - CION - talk in english - retransmis à Valrose
Fernando Buitrago - Astronomical Observatory of Lisbon
Séminaire Lagrange
TBD
 mardi 19 décembre 2017, 10h30, Salle O. Chesneau, Valrose - talk in English
Philippa HARTLEY - Manchester University

Janvier 2018

Séminaire Lagrange
A window on the TeV sky: recent results from H.E.S.S. II
 mardi 9 janvier 2018, 10h30, NEF - Mont Gros - CION - talk in english - retransmis à Valrose
Matteo Cerruti - LPNHE
      

Mise à jour : 23/10/17 05:51