Tag Archives: astronomy

Interview with Emily Freeland

Emily Freeland is one of the OKC fellows that joined the Oskar Klein Center after the summer. I asked her to tell us a bit about her research to get to know her better.

Hi Emily and welcome! Can you tell us a bit of yourself? Where are you from?
I am from the US. I grew up in Bloomington, Indiana, did my graduate work at the University of Wisconsin with Eric Wilcots, and my first postdoc with the newly formed astronomy group at Texas A&M University with Kim-Vy Tran.

What is your field of research?

The main theme that runs through the majority of my research is an exploration of the role that environment plays in galaxy evolution. The universe has a filamentary structure and these filaments are populated by individual galaxies and groups of galaxies. The group environment is the most common environment in the local universe so characterizing its influence is an important part of understanding the physical processes affecting the majority of galaxies.

Isolated galaxies tend to be disky, gas-rich, and currently forming stars. At the other extreme, galaxy clusters contain thousands of galaxies, many of which are red in color, ellipsoidal in shape, and not forming new stars. Galaxy groups span the range of properties intermediate between isolated galaxies and clusters. In our hierarchical universe, galaxy groups are the building blocks of galaxy clusters and as such we would like to understand to what extent galaxy morphologies and star formation rates are transformed in the group environment prior to their assembly into clusters.
Continue reading Interview with Emily Freeland

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. Continue reading Interview with Lucia Guaita

The end for supermassive population III stars?

Snapshot showing fragmentation and multiple star formation in a medium of primordial composition (Clark et al. 2011)

Are the first stars really very massive? Some 10 years ago, the idea that the first, metal-free stars would be very massive, became popular. Simple theoretical arguments about radiative cooling and complex numerical simulations both seemed to point to the formation of metal-free stars of masses of several 100s solar masses. Because of their zero metallicity they were dubbed Pop III stars. Early simulations of their formation are commonly associated with Tom Abel and Volker Bromm. Continue reading The end for supermassive population III stars?

Herschel finds enormous stores of dust in supernova 1987A

Supernova (SN) 1987A continues to surprise us. It exploded in February 1987 as a blue supergiant, not a red one, and it later displayed three circumstellar rings whose origin are still not completely understood. The latest finding is that between 160,000 and 230,000 Earth masses of dust may have been created since the explosion in 1987. It has been known from other core-collapse supernovae that they can produce of order 100 Earth masses of dust, but that another factor of 1000 was possible came as a complete surprise. The detection of the dust was made possible with the Herschel Space Observatory, which operates in the very far infrared, and is sensible to cold dust. Herschel detected SN 1987A in 2010 as part of a survey of the Magellanic Clouds. The detection was made in several wavelength bands, and the emission in those bands forms a spectrum which is the same as emission from very cold dust with a temperature of around 20 K. The finding was reported last week in a paper in Science with Mikako Matsuura (University College London) as first author, and OKC-member Peter Lundqvist as one of the co-authors. Continue reading Herschel finds enormous stores of dust in supernova 1987A

Observing supernovae with the Gran Telescopio Canarias

Rahman Amanullah is one of the post doc working within the Oskar Klein Centre. He is currently spending a few nights observing supernovae in the Canarias so I asked him to tell me what they are up.

We are just about to finish our second night at the world’s largest optical telescope, the 10.4m Gran Telescopio Canarias (GTC) on the summit of the island of La Palma. For me personally, observing surely confirms that the only difference between children and scientists are the prices of their toys. The pricetag of the GTC is roughly 650000 times more than the telescope I got in the 8th grade, but on the other hand it also has about 10000 times light collecting capability. Continue reading Observing supernovae with the Gran Telescopio Canarias