Scientific projects

International projects

AKARI

The AKARI (ASTRO-F) satellite mission was launched on 2006 February 22, and carried out a series of infrared photometric surveys in the near- (NIR), mid- (MIR) and far-infrared (FIR) passbands until the satellite termination in 2011. During its operation, AKARI performed deep survey of the north ecliptic pole in NIR and MIR passbands, survey of south ecliptic pole in FIR and all-sky survey in MIR and FIR.

Results obtained by the AKARI satellite contributed a lot to our understanding of the dust astrophyscis and galaxy evolution. Currently AKARI provides one of the most complete and deep infrared survey data. The NCBJ group is involved in the AKARI project from the very beginning. Main fields of scientific interest of our group in the AKARI project are focused on galaxy evolution physics, observational cosmology and machine learning application.

The Advanced Telescope for High-ENergy Astrophysics (ATHENA)

Athena (Advanced Telescope for High Energy Astrophysics) is an X-ray mission accepted by the ESA to address the Hot and Energetic Universe science theme. The mission will be launched in 2030 and placed at the second Sun-Earth Lagrangian point (L2). The planned mission lifetime is five years, but the mission is expected to last longer. ATHENA will be equipped with two scientific instruments: the X-ray Integral Field Unit and the Wide Field Imager.

The X-ray Integral Field Unit (X-IFU) will provide spatially resolved high-resolution X-ray spectroscopy from 0.2 to 12 keV, with energy resolution of 2.5 eV for the energies lower than 7 keV (for higher energies E/dE=2800).

The WFI has a large field of view 40'x40', and very high angular resolution, 5''. It will observe in the energy range 0.2 -- 15 keV with resolution 170 eV at 7 keV. The planned time resolution for this instrument is 80 µsec. It's scientific goals are related to high energy phenomena, and include studying hot baryons in groups and clusters of galaxies, accretion processes onto compact objects, and GRBs and other transient objects.

The Astrophysics Centre for Multimessenger studies in Europe (ACME)

The Astrophysics Centre for Multimessenger studies in Europe is a new Horizon Europe-funded project for the years 2024-2028. It gathers 40 world-class collaborating institutions from 14 countries and brings together the astroparticle and astronomy communities for long-term collaboration.

ACME is a pathfinder to broaden and improve access to the research infrastructures services and data, assess and evaluate new models for better coordination and provision of at-scale services, provide harmonized trans-national and virtual access, develop centres of expertise, improve science data products management, improve interoperable systems for rapid identification of astrophysical candidate events and alert distribution to optimize follow-up observations, provide training for a new and broader generation of scientists and engineers, open the astrophysics and astroparticle physics data sets to other disciplines and increase citizen engagement. ACME will also organize several dedicated workshops for scientists and students to provide training in the use and combination of multi-messenger data. NCBJ is coordinating access to time-domain archives and follow-up of multimessenger targets.

Polish PI: prof. dr hab. Łukasz Wyrzykowski (BP4)

BP4 contact person: prof. dr hab. Łukasz Wyrzykowski

Internal projects

Barely visible

Barely visible: low surface brightness galaxies in the LSST era
MAESTRO 2023/50/A/ST9/00579 (funded by National Science Centre, Poland)

PI: prof. dr hab. Agnieszka Pollo

All existing surveys of astronomical objects have limitations, due to the accuracy of the instruments and, in the case of ground-based observations, also to the fact that the Earth's atmosphere interferes with our observations. Consequently, our knowledge of the Universe is mainly based on observations of relatively bright objects.

Meanwhile, we have known since the 1980s that there are galaxies in the Universe that very easily escape observation. These are so-called low surface brightness galaxies, or more precisely, galaxies with a brightness lower than the typical brightness of the night sky. The first such galaxy was discovered by astronomer David Malin in 1986 - it is called Malin 1 and remains one of the largest known spiral galaxies to this day. Most of the currently known galaxies of this type are much smaller dwarf galaxies, but the variety of types among these galaxies is similar to that of their bright cousins.

The number of known low surface brightness galaxies has been increasing over the years. Initially, they were discovered mainly by chance, on the occasion of deep observations of selected areas of the sky. A systematic search for these objects has only recently begun. It turned out that they are virtually everywhere. Also, bright galaxies are surrounded by a faint glow, which sometimes extends over enormous distances.

There are still more questions about these objects than answers. How many are there? How much 'normal' baryonic matter is in them, and can they help explain the so-called 'missing baryons' puzzle - the fact that we observe less baryonic matter in the Universe today than in earlier cosmological epochs? Can they explain another cosmological problem - the so-called problem of missing satellites, i.e. the fact that we observe fewer small galaxies than predicted by theoretical models? What processes led to their formation, and why are they different from 'normal' galaxies? When did such galaxies form, and what did they look like in the past?

The atmosphere has been heated by studies of so-called ultra diffuse galaxies, a particular subtype of low surface brightness galaxies found in galaxy clusters. Among these, galaxies have been found that consist almost entirely - 99% - of dark matter, as well as galaxies that appear to be completely devoid of dark matter. How is this possible and what processes lead to such extreme objects? Can their existence be explained on the basis of the currently accepted cosmological model? Or do we need to change the laws of physics for them?

Answering these questions requires observing large areas of the sky with large telescopes capable of observing the faint glow of low surface brightness galaxies. A revolution in sky observation will be brought about by the Very Rubin Observatory, whose construction in Chile is just finishing and whose main objective is to create the Legacy Survey of Space and Time (LSST). The 8.4-metre telescope installed there, equipped with the world's largest wide-angle camera, will start scouring the entire southern sky in two years' time.

The aim of the proposed project is to build a team that, using simulations and currently available data, will develop new and improved methods to search for and classify low surface brightness galaxies, improve and develop new methods to study their physical properties, and finally, after applying the developed methods to the LSST data, try to answer questions about the role of low surface brightness galaxies in the evolution of the Universe - and the relevance to the laws of physics that govern it.

DINGLE

DINGLE - Dust IN Galaxies: Looking through its Emission
SONATA BIS 2020/38/E/ST9/00077 (funded by National Science Centre, Poland)

PI: dr Ambra Nanni

Just after the Big Bang, the Universe was only made up of hydrogen and helium.

We need to wait for the birth of the first stars to witness the appearance of heavier elements (metals) which can only be synthesised in their interiors, where temperatures reach tens of millions degrees. Metals are later released in the interstellar medium at the end of stellar evolution and new generations of stars are then formed from the metal-enriched gas. This process is known as the life-cycle of metals in galaxies. Metals are only the 2% of all the visible matter but they give origin to almost the totality of what we see on Earth, including living beings.

During their evolution stars can lose a substantial fraction of their mass, developing a dense and extended circumstellar envelope around them. This is one of the main sites for the formation of small solid particles starting from the available metals, known as "dust grains". In space, about half of the metals are condensed in dust. Despite dust being a small fraction (1%) of the total visible matter, it plays a crucial role in the evolution of the objects populating the Universe, including the formation of stars and planets that could harbour life.

The only way we have to study the properties of dust around stars and in galaxies is by investigating its effect on the radiation of stars. Indeed, dust grains absorb stellar radiation, heat up and re-emit this energy at longer wavelengths. Thus, the overall effect of this process is to modify the radiation originally emitted by stars and, consequently, the radiation that we receive and that we study. This effect is clearly shown in figure 1: in the upper panel we see the Milky Way in the visible band. The presence of dust clouds in the Galactic plane absorb the light from the stars and originates some "black spots". In the lower panel the Milky Way is shown in the infrared bands where dust re-emits the absorbed energy. We therefore see a bright emission at the Galactic plane where we have dust. By employing reliable theoretical models of the light emitted by stars and reprocessed by dust, it is possible to derive the physical properties of galaxies and to study how dust evolves from the beginning of the Universe up to the present days.

Figure 1: Upper panel: view of the Milky Way in the optical where stars emit: the black spots in correspondence of the galactic disc are due to dust clouds which absorb the radiation from the stars behind them (credits: Axel Mellinger). Lower panel: view of the Milky Way in the infrared bands where the light absorbed from the stars is re-emitted by the dust grains in the clouds (credits: COBE satellite)

The project DINGLE aims to model dust formation around mass-losing stars and in the interstellar medium of galaxies, and to develop a reliable description of light absorption and re-emission from dust grains. The aim is to study dust in different galaxies and compare our theoretical models with their observations.

The project will increase our understanding of the life-cycle of metals and dust from the first galaxies formed to the present day.

DUSTiny

DUSTiny: dust influence on galaxy properties in new generation surveys
OPUS 2024 2024/53/B/ST9/00230 (funded by National Science Centre, Poland)

PI: prof. dr hab. Katarzyna Małek

The star formation history of galaxies is characterised by the current rate of formation of young stars and the mass of already mature individuals. The complex interaction between adult and newborn stars and the dust intrinsic to star formation makes measuring and modelling these fundamental galaxy quantities (e.g., stellar mass, star formation rate, dust mass) a surprisingly challenging task. Star-forming galaxies are filled with clouds of dust that obscure young stars and the structures they form. The dust absorbs some of the light emitted by the young stars and re-emits this light in the infrared range. The exact course of this process depends on the properties of the dust and its geometry in the galaxy. Therefore, powerful ground- and space-based telescopes observe various galaxy types at different electromagnetic wavelengths to understand the effect of the dust and, thus, the 'life processes' of galaxies.

However, there are galaxies that we are not able to observe even in our Local Universe, and, therefore, we cannot study their star formation history. These galaxies are very diffuse and usually much larger than the well-known galaxies we observe in the beautiful images from the Hubble Telescope or the new James Webb Space Telescope. In addition, their low amount of less stellar light in the optical wavelength range makes it very difficult for current telescopes to detect them. These galaxies are called low surface brightness galaxies. They are a highly mysterious population of galaxies, as we have only accurately observed a few of them so far. Fortunately, soon, thanks to new observational projects and very high-tech astronomical instruments, we will be able to observe our Universe much more deeply and accurately, and these mysterious objects will no longer be so rare. In particular, we expect to track them in huge numbers in the planned 10-year Legacy Survey of Space and Time (LSST) scheduled for the Vera C. Rubin Observatory. The first light from this instrument is expected as early as 2025.

The main goal of the DUSTiny project is to analyse dust attenuation in both bright and low surface brightness galaxies. By participating in the LSST project, we will have access to optical observations of millions of galaxiesin function of their shapes (morphology). We are already preparing for our task by studying the properties of galaxies in a deep but tiny field located in the NEP's northern part of the ecliptic. As a result, our project will answer the question of whether the relative mass of galactic dust varies with galactic surface brightness and whether galaxies below the brightness level of previous observations require special treatment due to the different dynamics of dust-star interactions than in bright objects.

Listening to the silence

Listening to the silence: Investigating the interstellar medium in evolved galaxies across cosmic ages
PRELUDIUM 2023/49/N/ST9/00746 (funded by National Science Centre, Poland)

PI: mgr Krzysztof Lisiecki

Starting from baryonic matter, including stars, dust, and gas, through mysterious dark matter, to gravitational and electromagnetic interactions, galaxies encompass a vast majority of the physical processes known to modern science. Simultaneously, they are a crucial aspect of contemporary astronomy due to their relation to the evolution of the entire Universe. For this reason, investigating their formation, evolution, and the circulation of matter within these systems is of fundamental importance.

Observations confirmed by theoretical models show that dust and the entire interstellar medium accumulated within a galaxy are essential factors shaping its evolution. From the formation of molecular clouds to the significant influence on star formation and the absorption of high-energy electromagnetic radiation, galaxies as we know them could not exist without dust. However, modelling and studying galaxies based on observations are challenging due to the mentioned absorption of ultraviolet light by dust. By absorbing a significant portion of the radiation produced by young and massive stars and then reemitting it in the infrared, dust shifts the energy spectrum of the galaxy towards longer wavelengths. Until recently, studying the interstellar medium, including dust, in the young Universe was very challenging due to insufficient infrastructure. However, the recent launch of the James Webb Space Telescope may shed new light on these previously unnoticed infrared-quiet galaxies.

Until recently, it was believed that the majority of these passive galaxies were elliptical. However, recent analyses indicate that galaxies in the young Universe may have looked and behaved slightly differently than previously assumed. Therefore, conducting large surveys using state-of-the-art instruments from the aforementioned space telescope can shed new light on many aspects of galaxy evolution. This ranges from the dust content in the interstellar medium in the early Universe to the relationships between star-forming activity and morphology, as well as the influence of the environment on galaxy evolution.

In this project, we intend to utilize the latest data from the James Webb Space Telescope, which, in conjunction with other observations, including those from the Hubble Space Telescope, will help us understand the global dependencies of galaxy and interstellar medium evolution, particularly with regards to dust. Our goal is to uncover the origins of galaxies as they exist today.

Macroscopic Dark Matter

Search for macroscopic dark matter by the ground-based and space-based high sensitivity cameras
OPUS 2020/37/B/ST9/01821 (funded by National Science Centre, Poland)

PI: dr Kenji Shinozaki

The research project “Search for macroscopic dark matter by the ground-based and space-based high sensitivity cameras” aims at discovery of mysterious dark matter. Already in the 19th Century, scientists recognized “something” filling in Our Universe even though they are not visible to our eyes. Last fifty years, we are more confident “they exist”. Moreover, recent observations indicate no more than 4% of Our Universe is visible. So far, many efforts were made to discover dark matter, however, no successful results have been report.

In this project, we try the never tried new approach to search for such mysterious dark matter. In 1984, De Rujúla and Glashow published an attractive theory on the Nature journal. They postulated a new type of dark matter called “nuclearite”. Interestingly, they demonstrated nuclearites can be “observed” if they exist and pass in the atmosphere. Nuclearites may be even seen like shooting star meteors. Nuclearites are a type of dark matter particle called “strange quark matter”. Like ordinary element like carbon, oxygen, iron, etc., they are made of elementary particles called quarks which are as very dense as 360,000,000,000,000 (= 360 trillion) times heavier than water of the same volume. Nuclearites may have any mass. Theoretically, it can be as heavier than the Sun and as big as ~20 km quark star like already discovered compact stars called “neutron stars”.

Copernicus proposed Earth revolving the Sun in the 16th Century. Now, we know the Sun is not the center of the Universe. It revolves around Our Milky Way Galaxy at ~27,000 light years from the center of the Galaxy. Along with Sun, we move the toward the direction of the Cygnus constellation at about 250 km/s. Scientists cannot explain such a high speed without dark matter. Nuclearites have a mass and are bound by the Milky Way gravity. Near the Sun, they also move at similar speed to any direction if nuclearites exist. From the observers on the Earth, they look a bright light spot with a speed up to ~500 km/s.

The model of De Rujúla and Glashow indicates 1 kg nuclearites has a ~600 nm size. Very fast moving nuclearites hit the atoms and heat these atoms to result in the well-known black-body radiation emitting light until they cool down. This phenomenon takes place along the all path of the nuclearite. This light emission is similar to meteor shooting stars but happens near the sea level where air density is high. The speed is also different from meteors. The source of the meteors is considered the dust of comets revolving the Sun like planet, i.e. they are bound the Sun's gravity. The speed limit of meteors is no faster than 72 km/s to our eyes on the Earth. To find the nuclearites, we have to be able to take the video of even faster speed flying objects.

In this project, we are interested in nuclearites by two experiments. One is Mini-EUSO and the other is DIMS. We started the operation of Mini-EUSO a 25 cm telescope on the International Space Station (ISS) in October 2019 to monitor the Earth in the nighttime in the ultra-violet band. DIMS operates ultra-high sensitivity digital cameras for the meteor observation in the West Utah Desert, USA. DIMS group plans to build four automatic observation camera units deployed for meteors, particularly those with the origin out of the Solar System. This project will add another unit to specialize the nuclearite search.

The Mini-EUSO telescope is able to make a ultra-fast video at maximum 400,000 frame per second for 2000 pixels to study in details about the lighting and other phenomena. In orbit, Mini-EUSO keeps taking chronophotographic images about 24 frames every second to makes videos of 300 km x 300 km area. We already succeeded in making a first image of central Poland in the UV band. Many meteors were also observed. Seen from 400 km orbit, “500 km/s” looks slow enough by analyzing the Mini-EUSO data to search for kilogram nuclearites.

DIMS uses commercial digital cameras but with specially high sensitivity CMOS (Complementary Metal-Oxide-Semiconductor) sensor. These cameras make it possible to take ultra-fast nuclearite near the ground from the first time since the 1984 article. Even with only 1/30 s exposure, stars of the magnitude 10 can be recoginzed. In the test in Utah, we found ~3800 meteors in 40 hours by using two CMOS cameras. These cameras are able to take a video at ~60 frames per second with 2 mega-pixels. We aim at searching for about 1 gram nuclearite passing within ~30 km in this project.

In this project, if we find something consistent with the nuclearite, it may be the first long awaiting discovery of dark matter. Even no discovery is made, we will be still able to claim nuclearites would not exist no more than a particular value depending on how long we can monitor the night sky. We also expect the future application of CMOS technology in the space. Stay tuned and thank you for your support to our project!

Mapping merger histories

Mapping meger histories and AGN evoltion with Euclid
MINATURA 2025/09/X/ST9/01569 (funded by National Science Centre, Poland)

PI: dr Subhrata Dey

Galaxy mergers are crucial drivers of galaxy evolution, influencing their morphology, star formation history, and the activity of their central supermassive black holes. The gravitational interactions during the merger process funnel gas into the central regions, triggering intense star formation and active galactic nuclei (AGN) activity. Despite extensive studies, a key gap remains in our understanding: How does AGN activity evolve during merger stages? This project aims to address this gap by developing a deep learning computer vision model to identify galaxy mergers as a function of time using Euclid data, providing a solid foundation for future studies on AGN enhancement over time. The primary objective of this Miniatura grant is to fund two one-month research visits to the Netherlands Institute for Space Research (SRON), where I will work with Dr. Lingyu Wang, a leading expert in galaxy evolution and AGN studies, and the lead of the Galaxy and AGN Science Working Group within the Euclid Consortium. Dr. Wang's group is actively involved in leveraging Euclid's high-resolution imaging to study galaxy mergers, AGN activity, and their co-evolution, with access to both the Euclid Q1 data and Euclid-like mock datasets for training deep learning models. Euclid observes in the optical to near-IR (0.53-2.02 μm) across four bands with sub-arcsecond resolution. The Euclid Q1 data release offers sub-arcsecond imaging with a resolution of 0.15", comparable to that of the Hubble Space Telescope (HST), covering 63.1 square degrees in the Euclid Deep Fields (EDFs). Euclid's depth and resolution allow detection of faint tidal features and subtle morphologies, making it well-suited for accurate merger time identification. Over these two months, I will develop and train a deep learning network designed to classify galaxy mergers at different stages of evolution and assign accurate time stamps to these stages.

Massive Stars

The impact of massive stars: from the Milky Way to nearby galaxies
SONTATA 2022/47/D/ST9/00419 (funded by National Science Centre, Poland)

PI: dr Miguel Figueira Sebastiao

Galaxies that can be seen through amateur telescopes or on popular science images seem to be made of three components: an abundant quantity of stars and planets rotating around a central black hole. Nonetheless, the major part of galaxies is made of dust and gas at a temperature close to the absolute zero (−273 °C) and invisible to our eyes. Gas and dust tend to gather into huge clouds which are the birthplace of stars. For instance, one of the most popular stellar nurseries consists of three gigantic column of dust known as ”the Pillars of Creation”, and became famous thanks to the Hubble Space Telescope (and lastly with JWST).

When astrophysicists study the stars in our Galaxy, they have to distinguish between low-mass and high-mass stars because their formation, evolution and death are completely different. In particular, massive stars are able, at the very beginning of their formation, to sweep-up their surroundings thanks to powerful stellar winds and to the huge quantity of ultraviolet photons they emit. This phenomenon creates a layer of material around the massive stars and the whole structure is commonly called a ”bubble”. What is very interesting with these bubbles is that the surrounding dense layer of material is an excellent stellar nursery where a lot of massive newborn stars can be observed.

In my research project, I propose to observe these bubbles to study their properties and understand if they can efficiently form massive stars. Since the dust and gas are invisible to our eyes, we have to use specific telescopes dedicated to the observations of the coldest regions of our Galaxy. Using the data from the Herschel space satellite, I will study several bubbles, extract all the clumps of dust and gas found at their edges, and evaluate if these bubbles have the potential to form massive stars.

I will also observe the smallest structures inside these clumps thanks to very detailed observations from the ALMA interferometer, a system of 66 antennas working together to mimic an unique telescope of more than 1 km of diameter. I will also study the magnetic field with specific instruments able to detect the polarization of the light. These observations will tell us how the layer of dust and gas found around the bubbles is fragmenting, what physical processes govern this fragmentation mechanism and how massive stars are forming by unveiling the early beginning of their evolution. We will also compare bubbles in the Milky Way with bubbles in other galaxies to broaden our knowledge on the star-formation process.

This project aims at a better understanding of the role of bubbles in the formation of high-mass stars in our Galaxy. This is particularly important because thousands of bubbles are present in all galaxies and their crucial role in promoting the formation of a new generation of massive stars may change our view of the Universe’s history. Therefore, it is crucial to understand their role in the star-formation process in the global framework of galaxy evolution. Last but not least, due to the huge development of interferometry and the still unsolved question of high-mass star formation, I want, through this project, to promote the place of the National Centre for Nuclear Research (NCBJ), with a new Polish Community of students and researchers, to make it at the forefront of this promising research field.

RedWine

Uncovering the evolution of dust attenuation in galaxies: the role of the environment
PRELUDIUM 2022/45/N/ST9/01336 (funded by National Science Centre, Poland)

PI: mgr Mahmoud Hamed

In the last two decades, astronomers have gained massive knowledge of how galaxies form and evolve. This advancement in the field of extragalactic astronomy was coupled with the rapid development of the instrumentation aspect of astronomy, which led to accumulating a large amount of observations of galaxies at different epochs of the lifetime of the Universe. With giant multiwavelength datasets, we realized that galaxies are not just entities in space and time. They are more like living organisms: They are born, they get old and then they die! Such evolution of a lifetime of galaxies is governed by the amount by which they form stars.

The vital organ of galaxies is their interstellar medium, where the building blocks of future stars are found. In the interstellar medium, dust plays a major role in the life cycle of galaxies, it shields the molecular clouds from hot radiations, promoting new stars to be formed. However, dust absorbs a big amount of the ultraviolet photons that originate in the young stars, and emits them in the infrared thermally. This effect is known as dust attenuation.

Galaxies emit across the full electromagnetic spectrum, and every wavelength range reveals to us information about underlying physical and chemical mechanisms. Ultraviolet photons give us information about the rate at which galaxies are forming stars, since newly-born stars emit predominantly in the ultraviolet range. Older stars shine their light in the visible range, and interstellar dust grains emit in the infrared. Detected fluxes across these wavelengths help us to construct spectral models of these galaxies. To model galaxies’ emission, it is essential to account for dust attenuation, by using an attenuation law

Different attenuation laws exist, but they are not universal and we still lack the knowledge of how to correctly attenuate the stars in different types of galaxies to reproduce their observed spectra. Not knowing the exact shape of the attenuation restricts us from correctly interpreting fundamental properties of galaxies, such as their age, mass and the rate at which they are forming stars.

Years worth of observations provided us with unprecedented high quality detections of millions of galaxies at different epochs of the Universe. With telescopes that observe across all the wavelength ranges, we are now able to study and analyze galaxies’ spectra to better constrain the properties of interstellar dust, and therefore understand the nature of dust attenuation laws and how they vary in galaxies with different spectral properties, various morphologies and that are located in different environments. The various wavelengths through which these galaxies are detected will help us in modeling the total spectrum coming from them. This in turn will allow us to constrain the physical properties of these galaxies, and to understand what is the role of dust in their interstellar medium.

In this project, I will statistically investigate dust attenuation in galaxies at different epochs of the Universe, to better understand the role of dust attenuation in the context of galaxy evolution, and to better estimate physical properties of galaxies. This motivates the quest to understand how galaxies form, and what is the role of dust in converting interstellar gas efficiently into stars.

Smashing galaxies into dust

Smashing galaxies into dust
SONATA 2023 2023/51/D/ST9/00147 (funded by National Science Centre, Poland)

PI: dr William Pearson

Galaxies, large structures of stars, dust, and gas, do not live in isolation but tend to find oneanother and collide. During these collisions, the stars, dust, and gas in the galaxies are forced to move around violently, forming the beautiful structures we see in images of galaxy mergers. This motion of material can cause more stars to be formed at a much higher rate than would otherwise happen. This star-formation also has implications for the amount of dust and metals that are present in the galaxies, and how the dust obscures light. However, we do not have a solid idea of how the galaxy mergers change the amount of dust and metal present in a galaxy, or how the dust attenuates emission from the stars. To add to this, finding galaxy mergers is a non-trivial endeavour.

This project will investigate how we can more reliably identify galaxy mergers using their morphologies and how mergers influence their dust content, dust attenuation, and metallicity. This will be done by combining artificial intelligence (AI) with more traditional methods to detect galaxy mergers as well as use state of the art observations and techniques to study the galaxies' dust and metal.

For detecting galaxy mergers, this project will use images and morphological data of known galaxy mergers to compare AI results with results using morphology. It will continue to create new morphological parameters that can function with a similar ability to AI, assuming that AI works the best in the first experiment. This project will also use data from large simulations of our universe to train an AI to identify galaxies that are about to merge (pre-mergers) and have just collided with another galaxy (post-mergers).

Parallel to this, the project will study the dust content of galaxy mergers and compare it to the dust found in non-merging galaxies. This will use state of the art tools to extract the best information form state of the art data in the infrared, a key component for dust mass estimation. These data will also be used to help better understand how this dust hides optical light in merging galaxies compared to non-merging systems. These dust studies will be done for merging galaxies as well as pre-merging and post-merging galaxies, once the AI to detect these two merger stages has been finalised.

The project will also look at the metallicity of merging galaxies compared to non-merging galaxies. This will help us understand how galaxy interactions influence the amount of heavier elements present in galaxies.

With highly accessible techniques that will be developed in this project, the modern technologies used, and modern and near-future data sets, this work will be highly impactful and will influence future galaxy merger research.

Previous projects

AstroDust

ASTROdust: a complete census of dust attenuation in galaxies based on the analysis of millions of galaxies observed by Herschel
SONATA BIS 2018/30/E/ST9/00082 (funded by National Science Centre, Poland)

PI: dr hab. Katarzyna Małek

Stars are seldom found alone in the universe. They are formed and live out their lives together with other stars in massive associations known as galaxies. Optical telescopes show that our Universe if full of such islands. But the visible light is not the best source of information about galaxies and the structures inside them. Massive stars can emit in visible wavelengths such amount of energy that they seem to be disproportionally more significant than they really are. In the infrared this imbalance is less extreme, so we can get a more representative view of how the structure of the galaxy looks like, and how stars are actually distributed. Additionally, many galaxies are also filled with dust clouds that obscure our view of the overall structure of the galaxy. But thanks to the characteristic of dust, which become more transparent towards longer wavelengths, and is some ranges – it re-emits the ultraviolet light emits by young stars, galaxies observed in infrared light shows all the inaccessible in visible light structures of the galaxy. All those reasons cause that observation of galaxies in infrared range allows uncovering of areas inaccessible for optical observations.

The main aim of the project is to statistically investigate the attenuation of dust in galaxies and its dependence on the types of galaxies in different space ages. We will use a unique sample of one million galaxies observed in the infrared by the Herschel satellite. We plan to construct the correct attenuation curves for different types of galaxies and to examine how they have evolved over the past 10 billion years. This will lead to a re-evaluation of the basic physical properties of star-forming galaxies and will provide new tools to astronomers who occupy themselves with these fascinating objects.

ASTROdust project

Final Report

Classification if z~1

Classification if z~1
SONATA 2013/09/D/ST9/04030 (funded by National Science Centre, Poland)

PI: dr Katarzyna Małek

Final Report

Clustering of Infrared Galaxies

Klasyfikacja i badanie grupowania podczerwonych galaktyk
FUGA 2015/16/S/ST9/00438 (funded by National Science Centre, Poland)

PI: dr Aleksandra Solarz

Final Report

Cosmological Models Testing

Cosmological models testing with deep galaxy surveys
OPUS 2012/07/B/ST9/04425 (funded by National Science Centre, Poland)

PI: dr hab. Agnieszka Pollo

Final Report

Dusty Giants

Dusty Giants: How galaxies produce and destroy their dust in extreme environments
SONATA 2020/39/D/ST9/00720 (funded by National Science Centre, Poland)

PI: dr Darko Donevski

Galaxies in the Universe are complex systems that consist of gas, stars, metals and dust. The nature of galaxies is not only affected by the interplay of these baryonic components, but they also share a strong relation with surrounding halos of invisible, dark matter, into which they are embedded. As galaxy progressively ages since it’s formation, it passes through multiple evolutionary stages. Understanding physical mechanisms behind this evolution is one of the main goals of modern astronomy.

It has long been postulated that dust plays vital role in evolution of galaxies and their stars. It induces the formation of molecular clouds, supporting the birth of new stars. Dust grains also absorb stellar ultraviolet light at shorter wavelengths and re-emit it into in infrared, dramatically affecting the observed galaxy spectra. Major advances in far-infrared instrumentation in recent years, both space-based and ground-based, has led to the detection of more than a million, so-called dusty star-forming galaxies, very distant and massive objects that form large amount of dust and young stars. These discoveries posses a serious challenge to astronomy: many of these dusty ’Giants’ have been formed when the Universe was very young, sometimes even less than 1 billion years after the Big Bang, and we wonder how could such large amount of stars and dust have been produced so early in time?

Many theoretical models postulate that nature of dusty star-forming galaxies is key to understand formation of most massive structures in the Universe. The reason: these are thought to be direct evolutionary link between the most distant, active star-forming galaxies, and the most massive elliptical galaxies that reside in huge clusters we see in the local Universe. Probing and understanding this connection is a key task for modern infrared astronomy, but it is also highly challenging and under-investigated.

The project Dusty Giants aims at understanding the role of dust in galaxies and their large scale environments in galaxy evolution. The Project will pioneer the the methods to investigate the link between galaxy dark matter halos and life cycle of dust. This will be achieved by combining observations and state-of-the-art simulations in order to quantify how the relative ratio between dust and stars changes in different galaxy populations over cosmic time.

One of the expected outcomes will be a new technique of selecting and understanding distant proto-clusters. The Project is thus timely for providing the solid ground needed for interpreting future unprecedented data sets of large scale surveys of galaxies in the distant Universe (e.g. Euclid mission, Vera C. Rubin observatory) and their synergy with current millimetre telescopes on Earth (NIKA2, ALMA).

Experiment EUSO-TA

Experiment EUSO-TA - detector calibration and Ultra High Energy Cosmic Rays measurements of cosmic rays in coincidence with Telescope Array experiment
PRELUDIUM 2015/19/N/ST9/03708 (funded by National Science Centre, Poland)

PI: mgr inż. Zbigniew Plebaniak

The group of scientists from the National Centre for Nuclear Research are participating in the international satellite experiment JEM-EUSO (Japanese Experimental Module – Extreme Universe Space Observatory). The main JEM-EUSO objective are measurements of the ultra high energy cosmic rays (UHECR). UHECR are extremely energetic particles which come from the Universe. Their arrival direction distribution is nearly isotropic, as measured so far. The JEMEUSO detector is very fast camera (400 000 frames/sec) which would be placed at the International Space Station (ISS), and observe the Earth atmosphere from about 400 km. It will measure Extensive Air Showers (EAS) which are huge cascades of particles (and anti-particles) generated by the primary cosmic ray particle of very high energy in collisions with atmosphere nuclei. The cascade is moving in the atmosphere with the speed nearly to the speed of light in vacuum. The high speed camera is required to measure step by step time development of the cascade. The single measurement will allow to determine primary particle energy and direction. Many measurements (we expect to measure about 1000 particles with energies above 3×10¹⁹ eV) shall allow for search for astronomical sources of these particles, since their trajectories (if they are protons) shall be only slightly bended in cosmic magnetic fields. We expect to be able to confirm GZK cut-off, as well as measure events with still higher energies (like from „local” sources within GZK radius). JEMEUSO has also large scientific program for atmospheric phenomena measurements. In the JEM-EUSO project there are a few test projects. One of them is EUSO-TA experiment with objectives to calibrate the detector module and ground measurements of UHECR from the Telescope Array (TA) detector side (in Utah, USA), and with coincidence with TA.

Telescope Array is the largest cosmic ray experiment in the Northern Hemisphere. In the Utah desert it is far from any human made light sources, and it measures huge EAS during Moonless nights.

The main tasks of this project are calibration of EUSO-TA detector by set-up of many parameters of the camera to enable measurements of EAS, and measurement of EAS with EUSOTA working in coincidence with the Telescope Array experiment. The EUSO-TA detector is a single photo detection module (PDM) made of 36 photomultipliers (each with 64 anodes/pixels), similar to used or plan to use in another test experiments EUSO-Balloon, SPB-EUSO and Mini-EUSO.

Calibration can be made in a way to enable measurement and identification of stars which are in the field of view during the night measurements. With know brightness these stars are the reference objects for EAS measurements

During earlier measurements I have participated we had observed stars, air planes, lightnings, and several events which were probably EAS detections (it was the first test run of the EUSO-TA).

Elaboration of the automatic method for search for “cosmic ray” events in the hundreds of millions registered frames is part of this project, as well.

Within this project I have a plan to participate in measurements (shifts) in Utah. During these shifts I expect to observe EAS events with primary particle energies above 10¹⁸ eV. Events found and recognised as EAS would be compared with results of EAS simulations performed by other JEM-EUSO Collaboration members, and results will be published in the Experimental Astronomy (most likely). I am going to publish a paper with would describe performance of the high voltage power supply unit (HVPS) design and made in the Łódź Cosmic Ray Laboratory of the Astrophysics Department of NCBJ, where I am a PhD student.

The EUSO-TA detector has better angular resolution and faster camera than fluorescence detectors of the Telescope Array experiment. In this sense the EUSO-TA results are interesting complement of TA data base.

Realisation of this project would be important step towards the bigger projects like participation in experiments and data analysis from Mini-EUSO, SPB-EUSO and finaly in JEMEUSO. All these experiments are directed to measure and study of still poorly know nature of cosmic ray origin.

Final Report

Galaxy Clashes

Galaxy clashes: Making stars in the Universe’s biggest collisions
OPUS 2020/37/B/ST9/00466 (funded by National Science Centre, Poland)

PI: dr William Pearson

Galaxies, large structures of stars, dust and gas, do not live in isolation and are known to collide with one another. During these collisions, the galaxies become disrupted as the stars, dust and gas are moved around by the tidal forces created during these events. This movement of material can cause the gas to be compacted, resulting in periods of highly enhanced star-formation rates, know as starbursts. There is a wealth of observational and simulation information that shows that starburst galaxies are typically merging galaxies. However, what the observations cannot tell us is when these starbursts occur during a merger: are they early in the merger sequence, at the very end or somewhere in between. As a merger takes well over a billion years to complete, it is not feasible to watch a merger from start to finish to answer this question. On the other hand, simulations are able to see this but may not completely and accurately reflect what goes on in the real universe.

This project will determine how the star-formation rate of a galaxy changes as a merger progresses using observations. This is something that has not been done before and we have only recently developed the techniques needed to undertake such a study. While it is not possible to watch a single galaxy through an entire merger, it is possible to create a large sample of galaxies at different merger stages. However, identifying the merger stage is difficult, with only a simple pre-merger or post-merger classification having been done in the last year. This project will use the latest advances in artificial intelligence (AI) to identify the time before or after a merger event for a statistically large sample of galaxies. From this, an observed merger sequence will be determined and we will, for the first time, be able to see how star-formation rates in galaxies change as they merge and when these changes occur.

For this, we can use simulations of galaxy mergers. While not a perfect reproduction of the Universe, cosmological simulations are able to accurately reproduce the shapes of galaxies and how interactions distort these shapes. The simulations also provide a known time before or after a merger event. Thus, using images from simulations with known times before or after a merger event, an AI will be trained to be able to accurately determine the time before or after a merger happens. This AI will then be applied to thousands of images of real galaxies, providing accurate estimates of how long it is until a merger or how long it has been since the galaxies merged. The star-formation rates from these galaxies will then be determined and all the galaxies will be used to generate a statistical picture of how the star-formation rate of galaxies changes during a galaxy merger. From this, we will better understand why the universe looks like it does today.

The results of this work will provide a catalogue of merger times for use by other astronomers. Other physical properties of galaxies are believed to be changed as they undergo a merger and this catalogue will allow other groups to study these different phenomena, or find new properties that were not previously understood to be influenced by a galaxy merger. The AI will also be released, allowing other astronomers, and the wider public, to use and adapt it for their own needs.

Final Report

High-energy Interaction Models

Badanie wpływu parametrów modeli oddziaływań wielkich energii na rozwój WPA i możliwości pomiarowe eksperymentu JEM-EUSO
ETIUDA 2016/20/T/ST9/00589 (funded by National Science Centre, Poland)

PI: dr Zbigniew Plebaniak

Final Report

JEM-EUSO Collaboration

The highest energy cosmic ray measurements within JEM-EUSO Collaboration - detector elements preparation, participation in measurements and data analysis.
OPUS 2017/27/B/ST9/02162 (funded by National Science Centre, Poland)

PI: dr Jacek Szabelski

We want to measure and explore cosmic phenomena of extremely high energies: cosmic rays of ultra high energy. We do not know what objects emit so much radiation, nor how they do it. That is why we want to measure them with new satellite techniques. We participate in two big international scientific Collaboration JEM-EUSO. We have built high voltage power supply systems for all EUSO test experiments

Cosmic rays are energetic and stable particles and atomic nuclei coming from outside our Solar System. The most energetic ones are extremely rare. We observe them using the Earth's atmosphere as a target in which these particles interact and generate cascades of secondary particles, the number of which exceeds billions. We measure these cascades. The biggest experiment - Pierre Auger Observatory - has detectors on an area of about 3000 km² and observes about 1 cascade of ultra-high energy once every 2-3 weeks. The particles that generate such cascades have energies several million times greater than energy of each proton currently accelerated at CERN in a supercomplicated accelerator. To measure even more of these cosmic ray particles, we want to build a detector - a space telescope that will observe much larger part of the atmosphere from the International Space Station. This will be a complicated, big, heavy and expensive experiment (EUSO). For now, we have built a few small experiments: two for balloons, one in the desert next to the second largest cascade detector - the Telescope Array and one small test experiment for the Space Station. We will analyze the data and build more detectors.

By the way, we will measure solar flares (also very energetic phenomena) and lightning and so called ionospheric discharges (most energetic phenomena in the atmosphere).

The main scientific task of this project is analysis of the data that has been obtained and will be obtained during the project. We also plan to continue our commitment to building subsequent experiments.

Properties of Galaxy Clustering

Properties of galaxy clustering in the early stages of universe evolution
SONATA 2015/17/D/ST9/02121 (funded by National Science Centre, Poland)

PI: dr Anna Durkalec

Cosmology by its definition is the study of the origin, evolution and eventual fate of the universe. However, there is a lot of unknowns about the beginning of the universe, only uncertain theories about its future, and some huge questions about what happens in the middle. One of the most important of these questions is how the complex structure of galaxies observed in the local universe formed and evolved through time.

According to the modern cosmological models, which describes the state of our current understanding of the shape and evolution of the universe, the vast majority of its structure is build of something we can't directly observe. Because of that we named this component the ’dark’ matter, in opposite to the ’luminous’ matter we can observe. Studies showed that these two components are related and galaxies (or in general luminous matter) reside inside the dark matter haloes. Thus, in theory by tracing the evolution of the galaxy structures it should be possible to trace the evolution of the underlying dark matter structure. There is however one problem. This dark-luminous matter relation is never straightforward and depends, among others, on the different physical properties of galaxies. In result understanding the relationship between galaxies and the underlying dark matter become one of the key elements and the biggest questions of modern cosmology. The aim and purpose of our project is concentrated around this issue.

At first we address the problem measuring the level of galaxy concentration (clustering). Although this kind of studies have been conducted (extensively) on local Universe data, they have not been performed at early cosmic epoch, when the universe was very young. So seem natural and necessary to extend the analyses.

In this research project we propose an unprecedented study of the large scale structure performed at very early epochs of the evolution of the universe (when it was only 1.5 billions years old). Studies which were previously impossible due to the lack of good enough methods and technology allowing observations of the very weak objects. Now is possible thanks to the first of its type large spectroscopic galaxy survey aimed at observations of the young universe - the VIMOS Ultra Deep Survey (VUDS).

These analyses will allow us to answer the following questions: How, the highly concentrated large scale structure of the universe observed nowadays, has formed and evolved through time? What is the difference between the underlying dark matter density distribution and the observed luminous structures at different cosmic times? What is the physical relation between these two components: dark and luminous, and how this relation changed through time? What processes drive, regulate and truncate the formation of stars inside galaxies? When and what kind of mechanisms dominated the evolution of different galaxy types with given properties at different cosmic epochs. By answering these questions, we want (i) to test if our observations and measurements fit into the modern commonly accepted cosmological model framework and (ii) contribute to the developement of models of galaxy formation and star formation in the early cosmic epochs, which at present are still highly uncertain and lack sufficient observational evidence. This project aims at providing such an evidence.

The level of galaxy concentration can be quantify by measurements of two point correlation function, which will be the very base of all our the studies. This function is based on the very simple idea of measuring the probability of finding two galaxies separated by a given distance. Although the idea is relatively simple, this definition cannot be straightforwardly applied to compute the correlation function from real data samples, because of the limitations of galaxy surveys themselves. In principle, to retrieve ideal correlation functions one would need an access to an unlimited survey which covers the whole sky, and includes all galaxies. Naturally, in practice such surveys are unreachable. So the very first task in our kind of studies is always finding the appropriate method of correlation function estimation. All necessary tools and computer codes have been already prepared and tested by the PI of this project and they are ready for planned new measurements.

Naturally measurement of the correlation function alone would not help us at all. We need to use its approximation in for of accurate and physically justified model. Obtaining the best-fit model parameters allows to interpret the measurements and drive conclusions. There are many prescriptions for such of models. In the first place we are going to use recently the most extensively used ones - so called the halo occupation distribution (HOD) models. However we are also going to challenge the standard construction of the existing HOD models, by modifying their components and possibly adding new parameters. This become a crucial task as the 'standard' prescriptions are slowly ageing. The existing models served (still serve) great in the past decade or so, but they need to be update as there is increasing number of upcoming large galaxy surveys, which statistic will allow to measure very detailed correlation functions. Hence also detailed approximation, without simplified components, is now required.

In conclusion most of planned in this project measurements are going to be among the first ones ever performed with a high accuracy for data form early epochs of galaxy formation. As such, they will provide a valuable benchmark for the interpretation of the co-evolution of galaxies and Large Scale Structure at early epochs of galaxy formation (from the times when the Universe was only 1.5 billion years old) and put constrains on the efficiency of the processes which drive the star formation and mass assembly in galaxies at that time. All of this information can be used, among others, as an input to improve galaxy formation models and simulations, which are still uncertain and need to be informed by improved observational constraints. The measurements and results provided by this project can also be considered as a precursor of next generation studies coming with the advent of the new powerful facilities like e.g. the James Webb Space Telescope (JWST) or Extremely Large Telescopes (ELTs)

Our project will put some new perspective and will improve understanding of the Universe as it was at the early stages of its evolution. For sure our studies will serve as the basis for new follow-up studies, taking us even closer to definitive answers for the unanswered, major cosmological questions.

Final Report

Red Passive Galaxies

Evolution and star formation history in red passive galaxies
PRELUDIUM 2016/23/N/ST9/02963 (funded by National Science Centre, Poland)

PI: mgr inż. Małgorzata Siudek

The most common classification of galaxies, proposed by Edwin Hubble in 1926, distinguishes four classes: elliptical and lenticular known as early-type, spiral and irregular, known as late-type galaxies. This classification was only slightly modified later. However, elliptical and spiral galaxies are still considered as two main classes. Elliptical galaxies are usually larger, more luminous, redder and populated by older stars. They are known as “red and dead”, as there is no trace of formation of new stars in them. Spiral galaxies are in contrast smaller, less luminous, bluer and populated by young stars due to still on-going star formation. Thus, evolutionary scenario picturing young, spiral galaxies evolving into mature elliptical galaxies, seems quite natural. However, there is a crucial problem: such an evolution would need more time than the age of our Universe. Moreover, spiral galaxies contain not only young stars but also very old ones. Thus, understanding the evolution of galaxies, and the history of star formation in them, is one of the most important problems in modern astronomy

Astronomers are still searching for a detailed and robust description of the process of galaxy formation and evolution - processes leading to the formation of spiral and elliptical galaxies along radically different evolutionary paths. The fact that complex physical mechanisms regulate these processes is certainly one key contributor to the current state of uncertainty. Another contribution to our lack of understanding can be ascribed to the incomplete census that astronomers have been able to assemble for the properties of galaxies, and for their large-scale distribution, over a large fraction of the 13.5 billion years long history of the Universe. Nowadays we know quite well local Universe – the Universe in the radius of only 2-3 billions of light years from now. The lack of precise measurements of distant, faint galaxies makes it difficult to verify theoretical evolutionary paths of galaxies.

The recently completed VIMOS Public Extragalactic Redshift Survey (VIPERS, http://vipers.inaf.it ), a Large European South Observatory Programme, may change this situation. VIPERS observed almost 100,000 galaxies at 0.5 < z < 1.2, which means that the light traveled from them to Earth for 5-9 billions years. This means that we see these objects as they were at an epoch when the Universe was at approximately half its current age. VIPERS increased significantly the completeness of the census of galaxy properties at those early epochs of the Universe past history providing a unique opportunity to study galaxies and their evolution.

The goal of our project is to study the evolution of red passive galaxies and the history of their star formation over the last 8 billions years. Results of this work will be unique, as so far there was no spectroscopic survey so wide in an area (24 deg2) and reaching beyond z = 1, which means that for the first time the analysis in this redshift range will be so well-grounded from the statistical point of view, and the findings of this project will play a significant role in understanding the evolution of stellar populations in red passive galaxies.

The proposed project is dedicated for studies of a particular type of galaxies: red and passive. This population of massive, elliptical galaxies contains the oldest stellar populations observed in the local Universe. However, astronomers still do not know when and how they formed stars and became quiescent. If we look at the Universe at the half of its age are we also going to observe red and dead galaxies or they will be just in the stage of the formation? Did their stellar populations form during a violent starbust at high redshift or vice versa, they were gradually assembling their mass till relatively low redshift? The project focuses on addressing these questions by spectral and photometric analysis of red passive galaxies observed by VIPERS.

To determine properties and history of star formation in red passive galaxies, I will analyze spectral absorption lines (age and metallicity indicators) and the whole spectra (not only particular lines but also continuum). I will perform also an analysis of broad band magnitudes (from UV to infrared), which allows to describe simultaneously stellar content and dust part (spectral energy distribution fitting). The proposed project is focused on tracing the build up of stellar content in galaxies observed over the last 8 billion years using spectral and photometric information from VIPERS and local surveys (such as SDSS). Finally, I may be able to constrain evolutionary paths leading to formation of red, elliptical and blue, spiral galaxies observed in the local Universe.

Final Report

VIPERS and beyond

VIPERS and beyond: evolution of galaxies inside the large scale structure through cosmic ages
HARMONIA 2018/30/M/ST9/00757 (funded by National Science Centre, Poland)

PI: prof. dr hab. Agnieszka Pollo

How galaxies were formed? A simple question, but no simple answer. Even if modern galaxy surveys push our understanding of galaxy physics and evolution further and further, we have no final answer. In the present-day Universe large galaxies are often divided into two basic types. Elliptical galaxies look on the pictures like roundish clouds with no interesting substructure; usually they are filled with old stars and contain no material to form new stellar populations. The other type – spiral galaxies – are those which we most often admire in the pictures made e.g. by the Hubble Space Telescope. They have very complex structure, with spiral arms, bulges, lanes of dust and clouds of gas, dotted by areas where new stars are still being born. These two types are not all yet – the real zoo of galaxies is much more rich. There is a large and mysterious population of lenticular galaxies – “red and dead”, with no new stars forming any more but disk-shaped, often with central bulge, however, with no spiral arms. We have a variety of irregular galaxies, dwarf galaxies and many others. What led to the formation of so different types of galaxies? Some theories say that fate of galaxies was determined when it was born by the properties of the dark matter halo in which it was formed. Other approach attributes a crucial role to interactions with other galaxies. Astronomers agree now that the reality is most like more complex and both these factors played a role in formation and evolution of galaxies. Different combinations of different processes ultimately led to the formation of today’s variety of galaxies.In our project we plan to make use of the unique 3D map of the Universe as it was when it was a half its present age, 8 bln years ago, which we created in the framework of the project VIPERS – VIMOS Public Extragalactic Redshift Survey, which was a Large program of the European Southern Observatory.This map provides us not only the positions of galaxies in the space but also a possibility to investigate their physical properties – masses, shapes, stellar populations - by different means, even if it is obviously much more difficult than in the case of galaxies from our cosmic neighborhood. In our project we will weight and measure these galaxies, compare their properties, classify them, look how they are located in the cosmic web – a sponge-like structure woven of galaxies and dark matter. And we will compare them with galaxies we find in the local Universe, as well as with more distant objects. This will allow us to draw evolutionary paths of different types of today’s galaxies and to understand processes behind them.Shall we catch spiral galaxies turning elliptical – red handed (or at least red)? Shall we see lenticular galaxies just turning red? Huge and unprecedented data of the VIPERS project gives us real chances for such discoveries!

Wide-angle Tomographic Analysis of LSS

Wide-angle tomographic analysis of the large-scale structure and its imprint on the cosmic microwave background
PRELUDIUM 2018/31/N/ST9/03975 (funded by National Science Centre, Poland)

PI: mgr Szymon Nakoneczny

The universe is expanding and the pace of this expansion has been increasing for last several billions of years. The cosmic matter-energy budget is dominated by two mysterious components: dark matter and dark energy. The first one is responsible for the emergence of the large-scale structure of the Universe - the cosmic web of galaxies, galaxy clusters and superclusters, separated by enormous voids. The second one leads to the accelerated expansion - without it, the universe would slow down its expansion due to the attractive nature of gravity.

Those few sentences summarize our current knowledge about the Universe on the largest scales, which we have been gathering for many decades by various observations. This has led to the so-called standard cosmological model, in which few parameters are sufficient to describe the past and the future of our Universe. It is based on known physical laws, especially the most accurate theory of gravity so far - the general theory of relativity. While elegant mathematically and consistent with various astronomical measurements, unfortunately it does not provide an explanation about the nature of dark components, especially the dark energy which is responsible for the accelerated expansion of the Universe.

The goal of this project is to get closer to resolving the dark energy problem, by using two independent, however closely related, types of astronomical observations. The first one is galaxy distribution on the largest scales, about which we learn from large cosmological surveys. The second one is the remnant of the very early and hot stage of the Universe: cosmic microwave background, which was emitted when stars and galaxies did not even exist yet, and the cosmos was filled with a mixture of hot gas and light particles (photons). Studying these two probes, we are able to precisely measure most of cosmological parameters, especially the amounts of dark matter and dark energy, which play key roles in the evolution of the Universe

Large-scale structure and cosmic microwave background characteristics, which we learn about using quite different observational techniques, are inseparably bond together. Photons of the background radiation, travelling through the Universe since the very moment of their emission about 14 billions of years ago, interact in many ways with matter of the large-scale structure. One of such interaction is a change in photons’ energy when they approach large masses such as superclusters of galaxies, as well as their “opposites” - cosmic voids. The same structures also slightly curve photon paths, as a result of relativistic gravitational lensing. The scales of those effects depend on the global amount of dark matter and the rate of cosmic expansion, thus on the dark energy itself. In particular, the net change of background photons’ energy on their way since the emission to us - known as the Sachs-Wolfe effect - would not take place if not for dark energy.

In the proposed project, both the Sachs-Wolfe effect and background radiation gravitational lensing will be used to study dark energy properties as a function of cosmic time. The basic method consists of direct comparison of background radiation and galaxy distribution statistical properties, as well as in studying the imprint of the latter in the former, created as a result of the above mentioned interactions. Precise all-sky background radiation measurements from the Planck satellite will be used together with the largest available galaxy catalogs, which currently include hundreds of millions of objects. Reliability of the results will be ensured by carefully preparing maps and catalogs. The measurements will be eventually compared with many theoretical models which predict different properties of dark energy, as well with those that postulate deviations from general relativity on the largest scales.

Final Report

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