Transition from star formation to quiescence in galaxies

Stages de Master 2 en Astrophysique
http://stages-masters.sf2a.eu/detail.php?offreid=502
Informations sur le stage
Catégories
Cosmologie, Univers primordial, origine et évolution des grandes structures de l'Univers et des galaxies
Sujet du stage
Transition from star formation to quiescence in galaxies
Description
Large samples of galaxies show that their fundamental properties are bimodal (York et al. 2000, Driver et al. 2011, Lilly et al. 2007).
The current favoured scenario is that the ‘star forming ‘ blue cloud evolves towards the passive red sequence. The mechanisms
responsible for this star formation shutdown, also called ‘quenching’, are actively studied. Two types of channels are discussed: (1) the
environment could play a key role with ram pressure stripping, harassment and strangulation, feedback from an AGN, alternatively,
(2) the star formation activity could slow down with the increase of the galaxy. On the observational side, Bel"ore et al. (2016) has
shown on large samples of local galaxies (SDSS, MANGA) using spatially resolved spectroscopy that low ionisation emission line
regions (LIERs) are witnessing the intermediate stage, the so-called ‘green valley’. They "nd a sequence of star forming galaxies,
central LIER galaxies, extended LIER galaxies up to line-less galaxies. They typically reached a spatial resolution of 1kpc.
In the Local Group, Andromeda is a typical example of a green valley galaxy, with a signi"cant bulge with a central LIER located at
780kpc. With an international collaboration, we have observed the central kpc with the Michelson interferometer SITELLE on CFHT.
We have acquired 10 arcmin x 10 arcmin data cubes with R=5000. This unprecedented 3D data enables to access the kinematics and
the properties of the ionised gas (Halpha, [NII], [SII], [OIII], Hbeta), the planetary nebulae, the stellar population…
The goal of the proposed work is to use this data cube to simulate a local galaxy sample i.e. taking into account the distance
distribution and resolution of a given sample. The Andromeda data cube will be degraded to reach the pixel size corresponding to
each galaxy of the sample. A sample of 73 LIER galaxies publicly available from CALIFA will be used as a "rst step. This will be further
analysed and compared to the CALIFA data. This will require a spectral analysis to understand if the central LIER observed in the local
Universe are similar to Andromeda bulge. Various issues will be investigated to understand the properties of this LIER: what is the
contribution of the planetary nebulae to the LIER classi"cation? Does the strong stellar absorption decrease arti"cially the intensity
of the Balmer lines? etc. As a second step, a comparison with the results of Bel"ore et al. (2016) will be performed.
Nature du travail demandé
Traitement de données
Pré-requis
python, sens critique
Informations complémentaires
LERMA, 77 avenue Denfert-Rochereau 75014 Paris
Observatoire de Paris
Laboratoire
UMR-8112 LERMA
Laboratoire d'étude du rayonnement et de la matière en astrophysique et atmosphères
Paris
Calendrier prévisionnel
Date initiale estimée : 2017-03-15
Durée proposée : 3 mois
Encadrant
Anne-Laure Melchior (Chercheur ou enseignant-chercheur en poste)
[email protected] +33140512061
Grati!cation
Acquise
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