Tag Archives: star forming galaxies

The young star cluster perspective of star formation

Star formation is one of the fundamental process contributing to galaxy evolution and therefore in shaping the Universe. Yet it is extremely challenging to build a complete view of this process and its interplay with galactic scale properties. The most challenging aspect is to reconcile physical mechanisms, which operate at the smallest spatial scales (i.e. the size of our solar system) all the way up to galactic scale features such as the large star-forming complexes.

Two teams lead by Angela Adamo have now succeeded in putting forward two different observational projects that aim at understanding the nature of star formation at parsec scales and probe the link between these small scales and the host galactic environment. The projects are based on two recently accepted proposals at two world-class telescopes, the Hubble Space Telescope (HST) by Nasa and ESA, and the Very Large Telescope (VLT) by ESO.

The Hi-PEEC (Hubble imaging probe of extreme environments and clusters) project will use the new observations to look at the closest analogs of the high-redshift starburst galaxies. Galaxies today still carry with them witnesses of those experienced starburst periods, i.e. their globular cluster populations. We want to understand how these ancient populations formed and whether local galaxies can still experience star formation in a similar fashion as at high redshift. The Hi-PEEC team includes 20 astronomers (including OKC members: Göran östlin, Matthew Hayes, Matteo Messa, and Johannes Pushing) from 6 countries.

Fig.1. The Hi-PEEC sample in HST optical archival data. The new observations will  provide ultraviolet and optical information which will allow a detailed study of the young star cluster populations that are forming in these starbursts. The aim is to understand how these clusters form and whether they share properties of the ancient globular cluster populations.
Fig.1. The Hi-PEEC sample in HST optical archival data. The new observations will provide ultraviolet and optical information which will allow a detailed study of the young star cluster populations that are forming in these starbursts. The aim is to understand how these clusters form and whether they share properties of the ancient globular cluster populations.

The second project, based on VLT observations, consists of 21 hours to sample the nearby spiral galaxy Messier 83 (M83) with the integral field spectrograph unit (IFU) MUSE. MUSE is one of ESO’s newest instruments and it is the largest IFU currently available. The observations are organised such to produce a unique mosaic of the M83 spiral system. We will be able to study the effect of stellar cluster feedback on the interstellar medium of the galaxy from the smallest local scales achievable to date with optical spectroscopy to galactic scales. M83 has a very compelling collection of different environments characterised by different star formation properties. The centre of the galaxy is

Fig.2. The contours of the MUSE mosaic are overlaid on a visual band image of the spiral galaxy Messier 83. This unique dataset will be used to understand the interplay between cluster feedback and the ISM conditions.
Fig.2. The contours of the MUSE mosaic are overlaid on a visual band image of the spiral galaxy Messier 83. This unique dataset will be used to understand the interplay between cluster feedback and the ISM conditions.

perturbed by an ongoing starburst. The inter arm regions have very low starformation, conditions which are typical of the lowest efficient star-froming galaxies in the local universe. Finally, the star formation in the arm is typical of local star-forming spirals. The M83 dataset will be a key factor in our understanding of the effect of star formation feedback from local to galactic environments. The team responsible of this dataset counts 18 members (together with OKC members Göran Östlin, Arjan Bik and Matteo Messa) from 11 different institutes in Europe.

– Angela Adamo (adamo@astro.su.se)

Angela Adamo is a postdoc fellow at the Astronomy department at Stockholm University and a member of the Oscar Klein Centre since 2014. She is part of the Galaxy group, lead by Prof. Göran Östlin. Her main research aims at understanding star formation in the framework of galaxy evolution.

The Lithium problem. Primordial, cosmological or stellar?

Fabio Iocco is one of the Postdoc working within the OKC on Dark Matter. He is also interested in one of the puzzles keeping astronomers and cosmologists busy: the Lythium problem. Fabio has recently organized a conference dedicated to this mystery and he is getting ready to give the next OKC colloquium, this is why I asked him to tell us a bit more about this topic.

Credit: Belèn Roncoroni

Alright: the “Lithium problem”.
The “Cosmological” Lithium Problem.
The “Primordial” Lithium problem.
We all have heard about it since kindergarden, but would you bet 5000 SEK you know exactly what it is? I did not, so had to look it up. And here is what I have learned.
First of all, let’s play it fair: there’s two stable lithium isotopes, lithium-six and lithium-seven. In the last years it seemed both had problems, but we are talking about the bigger brother here, the one who has had problems for a longer time. Since 1982, 30 years ago -when my brother was born- there have been observations of lithium-seven in metal poor stars of the galactic halo. The most metal poor stars, the smallest mass, therefore the oldest stars to be around. Or at least a good approximation of a lot, a lot old. Ancient, pristine maybe. Ay, there’s the rub: “maybe”. Would you bet they were the first stars to be formed? I would not, but that’s another story. What matters here is that the stars were not the first generation, but the stuff in their atmosphere, what you observe when you take spectra of their surface may have been whatever had been produced “as far back in the past” as we could get with chemistry observations in our galaxy.
Continue reading The Lithium problem. Primordial, cosmological or stellar?

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