LERMA UMR8112

Laboratoire d’Études du Rayonnement et de la Matière en Astrophysique et Atmosphères



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Open PHD position in Astrophysics

par Valerie Audon - publié le

(October 2017)

Subject :

Sulphur-bearing molecules in star forming regions : Observational and laboratory investigations.

Supervisors :

L.E. Kristensen (Niels Bohr Institute & Natural History Museum of
Denmark, University of Copenhagen), F. Dulieu (LERMA, University of Cergy-Pontoise & Paris Observatory)

Thesis work.

The thesis aims at tackle the problem sulphur chemistry in star forming regions and in particular the of the origin of H2S in ices, as well as its link with other observed forms in shocks. One half of the work will be devoted to laboratory astrophysics. Using the experimental set-ups located in Neuville-sur-Oise (FORMOLISM and VENUS), the synthesis of H2S and the properties of the ice formed will be investigated. The experimental work will be done with the help of the team (https://lerma.obspm.fr/spip.php?article48). The other part will be devoted to the analysis of observations of sulphur bearing molecules in shocks, and will be mostly done in Copenhagen.

Practical details.

The grant will be a doctoral contract which is a 3 years working contract following
French/European regulations (1758€ monthly gross salary). The student will follow the courses and regulations of Doctoral School of Science and Engineering of Paris Seine University, (ED 417 http://www.collegedoctoral.u-cergy.fr/). The starting date is October 1st 2017 or as soon as possible thereafter. It is funded by ’Initiative excellence Paris Seine’

Application.

Applicant must have a master degree in Science, especially in Astrophysics, Physics or Chemistry. An experience (Internship, master diploma...) in radioastronomy or
experimental physics would be an effective positive aspect of the application.

Applicant must have excellent communication skills in English (oral and written), which will be the working language, although student will follow French language training (part of Doctoral School educational program), and may even learn Danish, Italian and few others languages with the team crews if motivated.

Applications should be constituted of a detailed CV, a letter of motivation and a letter of intent. The candidate should furthermore arrange for a recommendation letter from a professor familiar with the applicant to be sent to both Pr Dulieu and Dr Kristensen.
Applications received before 5th of september will receive full consideration.

More details : francois.dulieu@u-cergy.fr or lars.kristensen@nbi.ku.dk

Séminaires à venir

Vendredi 15 novembre 2019, 14h00
Salle de l'atelier, Paris
Excitation mechanisms in the intracluster filaments around the Brightest Cluster Galaxies
Fiorella POLLES
LERMA
résumé :
In the center of galaxy clusters lie giant elliptical galaxies, the Brightest Cluster galaxies (BCGs). These galaxies are often surrounded by a system of filaments (e.g. Salomé & Combes 2003) that emit in a wide range of wavelengths, illustrating the multi-phase nature of these streams. Many of these filaments do not have strong on-going star formation and the photoionization by stellar emission cannot reproduce their emission (Johnstone et al. 2007): what is preventing these structures to create stars and what heating mech- anisms are involved, are still open questions. I have investigated cosmic rays and X-rays as likely heating sources, combining multi-wavelength line emission (?23 lines: from optical to far-infrared) with Cloudy models (Polles et al in prep.). I have fully constrained the model of the ionized phase combining for the first time optical-to-infrared emission and self-consistent multi-phase models, pushing the analysis to the molecular phase on three off-nuclear regions of NGC 1275, the central giant elliptical galaxy of the Perseus Cluster. We showed that using X-ray emission as the main heating sources, all of the ionized line emission can be reproduced. We found that to reproduce [OI]63?m line, a small filling factor of the photodissociation phase is necessary. We also showed that adding an additional dense phase or an extra pressure component is required to robustly re- produce the H2 line emission.
 
Vendredi 29 novembre 2019, 14h00
Salle de l'atelier, Paris
The size of galaxies in the era of ultra-deep imaging
Nushkia CHAMBA
Instituto de Astrofisica de Canarias
résumé :
While the effective radius is a robust parameter, its use to
characterise galaxy sizes has provided a counter-intuitive definition of
what the actual extent of a galaxy is. Current deep imaging therefore
offers a unique opportunity to critically review the convention that the
size of a galaxy is its effective radius and rethink how one best
measures the extent of galaxies using a physically motivated parameter.
We introduce a new definition of galaxy size based on the gas density
threshold for star formation in galaxies. Remarkably, our new size
definition not only captures what the human visual system identifies as
the edge of a galaxy, but also dramatically decreases the scatter in the
stellar mass - size plane by a factor of three. Our size parameter
unifies galaxies spanning five orders of magnitude in stellar mass on a
single mass-size relationship. To demonstrate the implications of our
results, we show that ultra-diffuse galaxies have the same sizes as
regular dwarfs when a size indicator that describes the global structure
of galaxies is used. This work may be extended for larger samples of
galaxies using upcoming wide, deep imaging surveys.
 
Vendredi 6 décembre 2019, 14h00
Salle de l'atelier, Paris
Is accretion-driven turbulence a key process for galaxy growth ?
Pierre GUILLARD
IAP
 
Vendredi 13 décembre 2019, 14h00
Salle de l'atelier, Paris
Falsifying the concordance of cosmology with the large-scale structures
Benjamin L'HUILLIER
Yonsei University, Seoul
 
Vendredi 24 janvier 2020, 14h00
Salle de l'atelier, Paris
The accretion-ejection connection in planet-forming disks. New perspectives from high angular resolution observations
Benoît TABONE
Leiden
 
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