Tag Archives: galaxies

VR and Space Board grants to Dr. Angela Adamo

Dr. Angela Adamo is a young researcher affiliated with the Stockholm University Astronomy department and the Oskar Klein Centre.  She has recently been awarded two prestigious grants. The first, a Starting Grant from the Swedish Research Council, provides resources to help junior researchers establish themselves. The second is a career grant from the Swedish National Space Board.  These grants will support Dr. Adamo’s position and will allow her to build up a small group formed by a graduate student and a post-doctoral researcher.

A picture of Dr. Angela Adamo in her office
Dr. Angela Adamo

Dr. Adamo’s research uses young star clusters as units of star formation history and stellar feedback in nearby galaxies. Young star clusters contain hundreds of thousands of stars which are gravitationally bound in a space of about 3 light years and which stay bound for hundreds of millions of years. See the image below for an example of a young star cluster in our Milky Way galaxy. Star clusters are a product of the star formation process; they are different than field stars which disperse quickly after they form. Dr. Adamo and her group will investigate the clustering properties of star formation to probe how star formation proceeds from the smallest scales (the size of our solar system) to galactic scales (the size of our Milky Way) in a self-consistent way. The goal is to provide important pieces of observational information that will help to build a consistent picture of galaxy formation and evolution.

This image shows the sparkling centerpiece of Hubble's 25th anniversary tribute. Westerlund 2 is a giant cluster of about 3000 stars located in the our Milky Way galaxy. Hubble's near-infrared imaging camera pierces through the dusty veil enshrouding the stellar nursery, giving astronomers a clear view of the dense concentration of stars in the central cluster.  Dr. Adamo and her group will study similar regions in other galaxies in order to understand the clustering nature of star formation.
This image shows the sparkling centerpiece of Hubble’s 25th anniversary tribute. Westerlund 2 is a giant cluster of about 3000 stars located in the our Milky Way galaxy. Hubble’s near-infrared imaging camera pierces through the dusty veil enshrouding the stellar nursery, giving astronomers a clear view of the dense concentration of stars in the central cluster. Dr. Adamo and her group will study similar regions in other galaxies in order to understand the clustering nature of star formation.

Star ripped apart by supermassive black hole

It’s a star!
It’s a supernova!
No, it’s … a Spinning Black Hole Swallowing a Star!

In the very first issue of the new journal Nature Astronomy, former Oskar Klein Centre (OKC) post-doc Giorgos Leloudas (now at the Weizmann Institute of Science and Dark Cosmology Centre) suggests a new interpretation for the event ASASSN-15lh, formerly known as the most luminous supernova ever.

Leloudas and colleagues performed follow-up observations after the luminous event and found that with ten months of additional data the event no longer resembled that of a supernova. Co-investigator, Christoffer Fremling from the OKC, did all of the image subtraction to extract the light curve for this event.  Instead, they suggest, ASSASN-15lh was a star ripped apart by a supermassive black hole – a tidal disruption event.

One interesting aspect is the suggestion that this supermassive black hole might be rotating rapidly, says co-investigator Jesper Sollerman from OKC. Maybe these kind of tidal disruption events will become a way to explore the rotation of supermassive black holes billons of light years away.

The research paper discussing these results is available here in Nature Astronomy (arXiv version).  The video below shows a spinning supermassive black hole as it rips a star apart (artist’s impression).

[Top image: This artist’s impression depicts a sun-like star close to a rapidly spinning supermassive black hole, with a mass of about 100 million times the mass of the sun, in the centre of a distant galaxy. Photograph: ESO, ESA/Hubble, M. Kornmesser]

Consolidator Grant to Dr. Matthew Hayes

Our investigation of how galaxies change with time was previously limited to direct study of the stars and gas that constitute the galaxy. It is now understood that the region of space around a galaxy, the circumgalactic medium, plays an important role in both fueling star formation inside a galaxy and absorbing the escaping energy produced by that star formation.

Matthew Hayes
Matthew Hayes

In order to enable further study of the circumgalactic medium in galaxies, the Swedish Research Council has awarded a Consolidator Grant to Dr. Matthew Hayes, lecturer in the Stockholm University Astronomy department. Consolidator grants are designed to give junior researchers the opportunity to expand and broaden their research activities.  The award provides two million crowns per year for a period of six years. Dr. Hayes will use the money to hire postdoctoral researchers and graduate students.

One of the galaxies that will be studied is shown below in optical light, ultraviolet light, and light from highly ionized oxgen atoms. The project relies on use of the Hubble Space Telescope to detect OVI (five times ionized oxygen) in emission from the circumgalactic medium surrounding star forming galaxies. The technique is presented in this recent paper (arXiv version).

Image of a galaxy in optical light, ultraviolet light, and the light from five times ionized oxygen atoms.
One of the galaxies that will be studied is shown here in optical light, ultraviolet light, and light from ionized oxgen atoms.

Unique study shows how Lyman alpha light travels through starburst galaxies

Credit: ESA/Hubble & NASA, M. Hayes
A study of nearby starburst galaxies by a team of scientists lead by OKC professor Göran Östlin, and involving several other OKC members, has been featured as a Hubble Space Telescope Picture of the Week last week. The study, the Lyman-Alpha Reference Sample (LARS), targeted 14 galaxies using the Hubble Space Telescope (HST). The galaxies were observed at many different wavelengths, making it the largest Swedish project ever to carried out on HST. The first publication from the team is now available(astro-ph: http://arxiv.org/abs/1303.0006). The first author of the article, Dr. Matthew Hayes (IRAP, Touolouse, France), will be joining the OKC as a researcher later this year. The main results is the discovery of an extended halo of Lyman-alpha radiation in most of the galaxies in the sample. The size of this halo is significantly larger than the sizes of the galaxies in ultraviolet light. The presence of the extended emission means that the Ly-alpha radiation escapes the galaxies far from the places, the sites with active star formation, where it was produced.

One of the main drivers for the LARS project is to understand how Ly-alpha radiation is produced and reprocessed in star-forming galaxies. By targeting nearby galaxies the study
can give very detailed clues to what is happening in these complicated systems. The knowledge gained by investigating the local galaxies can also be used to try and understand observations of Ly-alpha emitting galaxies much further away (at high redshift). Here are collected images of the all 14 galaxies (but using a different set of filters).
These first results from the LARS project are exciting, but the wealth of data collected by the HST for LARS means that there is much more to come later this year!

– Jens Melinder, OKC postdoc (jens@astro.su.se)

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

Workshop: clusters of galaxies as cosmic laboratories

Galaxy clusters occupy a central role in the ongoing efforts to understand some of the greatest questions in particle astrophysics and cosmology: the nature of Dark Matter and Dark Energy. Moreover, these huge mass concentrations serve as Nature’s own telescopes, capable of amplifying faint high-redshift sources that would otherwise be beyond our reach. At the same time, the use of galaxy clusters as probes for fundamental physics requires a good understanding of the state of the intra-cluster medium.

No wonder that the Oskar Klein Centre got involved in the organization of a workshop in Stockholm, 12-14 September. Ariel Goobar, professor at the Oskar Klein Centre, explains that there is a large effort by the community to collect multi-wavelength galaxy cluster data, which present a great opportunity to make significant progress over a broad range of topics: Continue reading Workshop: clusters of galaxies as cosmic laboratories