Interview with Lucia Guaita

Lucia Guaita is one of the Oskar Klein Centre postdocs, working at the astronomy department here in Stockholm. She started as postdoc at OKC about one year ago, on November 2010, and is working on high-redshift star forming galaxies. Let’s get to know her better.

Why did you choose the okc for doing your postdoc?

This is my first post doc. I chose to apply to this position because the topic would have been very close to what I was doing during my PhD. It seemed quite a nice continuation of my PhD thesis work and it is.

What is your field of research?

I am working on star forming galaxies at high redshift. We are interested in observing these galaxies where the Universe was less than 3 billion years old (redshift more than 2). In a star forming galaxy there are regions where stars, of different mass, are continuously produced.
The high-energy radiation produced by the just-formed high-mass stars interacts with neutral Hydrogen in the interstellar medium. One of the consequences of this interaction is the production of Lyman alpha photons. It was proposed since the 60’s that star forming galaxies at high-redshift should show a strong Lyman alpha emission line, even if they are faint in the continuum. In these last 10 years a lot of surveys were designed to detect Lyman alpha emission from star forming galaxies at high redshift, the so called Lyman Alpha Emitters (LAE). The technique, we used, involves a narrow band filter, about 50 Angstrom wide, centered at the redshifted Lyman alpha emission line. The idea is to detect an excess in narrow-band flux density with respect to the continuum.
As Lyman alpha photons are absorbed by dust, LAEs are thought to be dust-free galaxies in their first phases of star formation.

How is this connected with your PhD thesis?

During my PhD I used the Cerro Tololo 4 meter telescope in Chile to take data about LAEs at redshift around 2. I am part of the MUSYC (MUlti-wavelength survey by Yale and Chile) survey. The principal investigator is Prof. Eric Gawiser, one of the two advisors of my PhD thesis. He is professor at Rutgers, the State University of New Jersey. The other one was Prof. Nelson Padilla from Pontificia Universidad Catolica de Chile.
It turned out that, at redshift 2, also in galaxies with a moderate amount of dust Lyman alpha photons can escape and compose a Lyman alpha emission line. Therefore, it was proposed that the geometry of dust and Hydrogen in the interstellar medium are key ingredients for a galaxy to be an LAE.
Lyman alpha line strength and profile, ratio between Lyman alpha and other emission lines typical of star forming galaxies, such as Halpha line, less affected by the presence of dust, are studied to investigate the intrinsic characteristics of interstellar medium geometry and galaxy outflows in LAEs.

What is your work now at the Oskar Klein Centre?

I am right now involved in a spectroscopic survey with the purpose to study Halpha emission in LAEs. The data were taken with the 6.5 meter telescope at Magellan telescope in Cerro Las Campanas, Chile.
I am also studying the relation and properties between galaxies detected thanks to their Lyman alpha emission versus those detected thanks to their Halpha emission. About this I am working in Prof Goran Östlin’s research group at Stockholm University. We are using the 2.5 meter Nordic Optical Telescope at La Palma for the photometric data.
The presence of dust could completely block the escape of Lyman alpha photons, while the Halpha ones would still be visible.
The view of sight of the galaxy could not allow us to see any emission. However, Lyman alpha photons are resonantly scattered by neutral Hydrogen and can reach the outskirt of the galaxy, far from the region where they were originally produced. Therefore, we could see Lyman alpha but not Halpha photons simply because they are coming from a become-favorable view of sight.

What do you find unique for your field of research about the OKC?

In this institute I found a very good environment to work in. I think it is very well organized in terms of space and meeting points.
Here it is possible to develop projects, expensive also in terms of money and I do not think it is obvious either in other places of Sweden or other countries.
For example I had the possibility to invite a visitor and she felt very well thanks to the organization and efficiency here.

Also, because the Oskar Klein centre includes people working on different topics, I am offered the possibility to attend seminars on subjects other than mine, such as particle physics. I would not attend them in another astronomy department.

What is your story before the OKC?

I am from Italy. I got y PhD in Santiago Chile at Pontificia Universidad Catolica de Chile. I was very lucky during my PhD to be able to use one of the biggest telescope in the world, quite easily. Chilean Universities as 10% of the observing time for the telescope on Chilean ground. I enjoyed Santiago very much, because it is full of activities, mainly in summer season. I also enjoyed very much to have sunny day always basically from October to April. I enjoyed very much hiking on Cordillera de los Andes.
I spent few periods in Rutgers, New Jersey to visit my professor Eric Gawiser. I found very nice scientific atmospheres in Chile and at Rutgers. Many astronomers, every year, travel to Chile to use European and U.S. telescopes. Therefore, high-quality seminars are organized in Chilean institutions.
I came back to Europe last year for the first post doc.

I can think of a lot of differences between Chile and Sweden. Did you get used to the weather in Stockholm?

Stockholm is a very organized city. It is very well organized for difficult weather too. For me the weather has not been a problem this year.
Something that I missed is the daylight. In Chile the Sun is very bright and the days are much longer than here.

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