Category Archives: MUSE

An extended Lyman-alpha halo around a z=3.5 galaxy

Clusters, Galaxies, MUSE

Last week a CALENDS paper on MUSE commissioning data, led by Vera Patricio, was accepted in MNRAS. It is the study of a redshift 3.5 lensed galaxy, observed in the SMACS2031 cluster, that first caught our attention because of its extended Lyman alpha halo (check the figure below!), that traces the gas around the galaxy. Usually, these halos are studied by combining the signal of several dozens of galaxies, since they are not very bright, but by making use of MUSE and gravitational lensing we can see these galaxy outskirts individually and with higher detail. An interesting result that we were able to obtain from these data was a velocity map of the Lyman alpha and  CIII] line (see figure as well). The first line traces the neutral gas, and its analysis can give us some clues about its density and geometry, while the second line probes the regions where stars are being born and the hotter gas kinematics. From the same MUSE data, we also extracted high quality spectrum (that you can also see below) from which we learn much about this galaxy, confirming that it has the typical mass and luminosity of most galaxies at the same epoch,  deriving the temperature, density and chemical composition if its gas and the age and metallicity of its stars.

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1 — The SMACS2031 cluster observed by MUSE. The boxes indicate the place where the 5 multiple images of this z=3.5 galaxy can be found and the red line traces the mass model that allow us to predict its unlensed properties

2 — An image of the Lyman alpha emission of this object. On top of it, the magenta contours trace the CIII] emission

3 — The Lyman alpha (big figure) and CIII] (smaller figure on the bottom left) velocity fields.

4 — The spectrum of this object with some interesting emission and absorption lines, that allowed us to study the properties of the gas and stars of this galaxy.

Intoducing team members: Vera Patricio

Clusters, MUSE, observations, Recruitment

I was born and raised in Lisbon, Portugal’s capital, where I completed my physics degree at Instituto Superior Técnico. When the time to do my master thesis arrived, I had the amazing opportunity to work with Myriam Rodrigues, an ESO fellow in Chile, in her project which aimed to understand how much we can know about the stars that make up a galaxy by analysing its total spectrum. It was the first time that I had the change to study galaxies and I was in love with it at once. I even got the chance to stay a few days at the Very Large Telescope, learning about its instruments and about the work of observers. By the end of my Master, I had decided that the coolest job in the world was to observe galaxies and study their evolution. So I found the perfect place to do it here in Lyon, within the CALENDS team: I’ll be looking into very distant galaxies, whose details can only be disentangled thanks to magnification caused by gravitational lensing, and try to place them in the big picture of galaxy evolution.

During my PhD I will analyse several arcs – galaxies that we see very magnified but also very stretched due to distortion introduced by the lensing, and try to figure out what stars compose them, what chemical elements are there and how are their stars and gas moving. To do so, I will mainly use MUSE data, which offers us a unique combination of spectral and spatial analysis, perfect (also!) for this kind of study.

vera

 

  • Congres de doctorants

On October 23, PhD students both from the Observatoire de Lyon  got together to present their work at the 4th ‘Congrès des Doctorants’ (http://doctoraleslyon4.sciencesconf.org).  The congress was split into four sessions, that spanned topics from paleoenvironments to mantle convection, and was open to master students, university professors and researchers. I gave a talk in the ‘Star Wars’ session, cheered up by CALENDerS & Friends, to present my recent work on a galaxy at redshift 3.5 lensed by the SMACS2031 cluster. In the time let for questions, we learned that seismology uses very similar principles to lensing to study the mantle though seismic sound waves, just like we do with light waves!

doctorants