As per the ΛCDM cosmological model, the halo of the Milky Way was built up by the merging of numerous progenitor galaxies, as these dwarf galaxies brought in their own stellar populations (in the form of stars and globular clusters). Over time, the dwarf galaxies were tidally stripped by the Galactic potential, eventually leading to the formation of “stellar streams”. Therefore, stellar...
During the cosmic dark ages, the Universe primarily consisted of neutral hydrogen (HI), which emits radiation via the 21-cm hyperfine transition. Radio interferometers, such as the Low-Frequency Array (LOFAR) and the future Square Kilometre Array (SKA), are attempting to measure its spherically averaged 21-cm power spectrum from the Epoch Of Reionization (EoR). The statistic is not only a...
The growing phase of supermassive black holes (SMBHs) in galaxies is one of the debated topics in modern astronomy.
Recent observations reveal that a fraction of (ultra) luminous infrared galaxies; (U)LIRGs host extremely compact and dusty nuclei.
Such compact obscured nuclei (CONs) are only realised in an environment with extremely high column density of materials surrounding the SMBH, and...
The roles of radiation-mediated shocks (RMSs) in the prompt emission of gamma-ray bursts (GRBs) have been thoroughly investigated theoretically. However, so far, no such model has been fitted to data due to the computational complexity of simulating RMSs from first principles. We aim to bridge this gap between theory and observation. In this talk, I will present an approximate model called the...
The most energetic explosions in the Universe after the Big Bang are Gamma-Ray Bursts (GRBs). They emit intense and brief flashes of gamma-rays initially during their prompt phase, followed by a long afterglow phase observed in all the wavelengths. Multi-wavelength observation of GRB afterglow provides some hints for the nature of the emission mechanism. However, the GRBs are not observed in...
While high-energy neutrinos have been detected by the IceCube neutrino observatory for more than a decade, their individual sources still remain unidentified. Some of the most prominent candidates for emission at such high energies are blazars, a type of Active Galactic Nuclei (AGNs) with powerful relativistic jets, and Gamma-ray Bursts (GRBs), both thought to be the birthing place of...
Through recent efforts using narrowband observations and integral field spectrographs, high redshift (3<z<6) Lyman alpha (Lya) emitting galaxies have been found to almost ubiquitously have spatially extended Lya emission, known as a Lya halo, extending significantly further out than their star formation (as traced by UV emission). At these redshifts, Lya is the highest surface brightness...
The cosmic microwave background (CMB) has played a foundational role in the establishment of the standard model of cosmology. Driven by significant technological advances, future experiments endeavour to revolutionise our understanding of the infant universe via detection of primordial gravitational waves and neutrino properties through their role in structure formation. In this talk, I will...
Active galactic nuclei (AGN) are galaxies which host active supermassive black holes (SMBHs) and present a crucial element in the evolution of galaxies. In this paper, we aim to contribute to the understanding of how the nuclear activity is related to its surrounding environment. We present results of an archival project, where we use the GAMA survey to compare the neighborhoods of quasars and...
Space debris is becoming an increased threat to the future use of space orbits. In order to counteract this threat, the field of Space Situational Awareness (SSA), and the sub-field Space Surveillance and Tracking (SST), have been developed to gather knowledge about the space debris and satellites surrounding Earth. The orbit of a satellite can be determined by acquiring images of the...
After the detection of numerous planetary systems outside of our own Solar System which tend to be extremely diverse and which show a wide range of evolutionary states, the focus is now shifting to a characterization of their formation and evolution, as well as to the architecture of planetary systems and planet habitability.
One of the astonishing discoveries in exoplanet research has been...
Statistical studies of exoplanet populations have shown that planets in the 2-3 $R_{\oplus}$ size range, the so-called mini-Neptunes, are one of the most common types of planets.
In this talk I will highlight some of the challenges associated with the detection and characterisation of such planets in transit and radial velocity timeseries as illustrated by the case of the TOI-1260 system....
The Planetary Spectrum Generator (PSG) is an online tool that synthesizes spectra of planetary atmospheres for a broad range of wavelengths (10nm to 100mm) simulating several space- or ground-based observatories/instruments. The 3D GlobES application of PSG allows us to synthesize observations of exoplanets based on different 3D General Circulation Models (GCM). In particular, we use GlobES to...
The discovery of planets around other stars (exoplanets) has fundamentally changed our view of the possible types of planets. With the discovery of a diverse population of planets, a class of highly irradiated gas giants has emerged that are unlike any planet in our solar system.
Ultra-hot Jupiters offer the opportunity to learn about the chemistry, thermal structure and dynamics in...
For the first time in over 60 years a meteorite was recovered in Sweden after an observed fall. The fall area was identified through a collaboration between the meteor camera networks in Norway, Finland, Denmark and Sweden. After a few weeks of searches, a 14-kg iron meteorite was found close to the small town of Ådalen (near Enköping). This meteorite is the first iron ever to be recovered...
Explaining the dynamics of a binary star system can be a tricky task, especially for students that may not be confident in using the disciplinary discourse of physics and astronomy. In this talk, we examine video data of a pair of physics students, showing how they successfully reason about binary star motion without the terminology of Newtonian mechanics, but rather by recruiting their bodily...
The “Vanishing & Appearing Sources during a Century of Observations” (VASCO) project uses existing survey data to search for exceptional/unknown astrophysical transients (see Villarroel et al. 2020) that might occur during a 70 years of time baseline, in particular vanishing objects. The broad set of astrophysical goals range from searching for natural astrophysical objects e.g. Active...
We investigate the thermal emission and extinction from dust associated with a nearby superluminous supernova (SLSN) at $z=0.0267$, SN~2018bsz, in order to determine its nature. We use the 7-channel imager GROND to extensively monitor the photometric evolution of SN~2018bsz. This is the first dataset with daily cadence and simultaneous optical and near-infrared (NIR) coverage for a SLSN. At...
The detection of an electromagnetic counterpart to the gravitational-wave source GW170817 marked year zero of the multi-messenger gravitational-wave era. This event was generated by the merger of two neutron stars and gave rise to an electromagnetic transient, dubbed a “kilonova”, which was intensively monitored with all the main ground-based and space-borne facilities. In this talk, I will...
The thermal transient following a binary neutron star merger, known as a kilonova (KNa), is expected to enter the steady state nebular phase several days to weeks after merge. In this state, the ejecta is optically thin and bolometric luminosity tracks instantaneous radioactive energy deposition. The steady-state phase is expected to last until reprocessing timescales become long, at which...
SNR 0540-69.3 is a ~1000 year-old-supernova remnant (SNR) located in the Large Magellanic Cloud. This remnant is associated with an active pulsar and a pulsar-wind nebula (PWN) and also possesses an oxygen-rich ejecta. Oftentimes, SNR 0540 is referred to as the Crab’s twin due to their similar properties, including the millisecond pulsar and PWN.
We study the continuum emission of the...
Core collapse supernovae (CC-SNe) are the violent and bright explosions that end the lives of massive stars (M>8M$_\odot$), leaving behind exotic remnants such as black holes and neutron stars. A currently unsolved question in supernova research is the origin of Type Ib and Ic SNe, which lack hydrogen, or hydrogen and helium, spectral signatures respectively, indicating that the outer stellar...
Supernovae are the end stages of stellar evolution, resulting in enormous energy release. They have a great impact on their environment, help us understand stellar and galactic evolution, shock physics and radiative processes, and are linked to life on earth. In the radio, synchrotron radiation from the interaction of the supernova ejecta with the dense circumstellar material is visible....
Despite the importance of massive stars and star clusters for the energy content, stellar population and evolution of galaxies, the mechanism that ignites their formation in molecular clouds is still poorly addressed. Infrared Dark Clouds (IRDCs) are a class of very massive and dense objects, likely to be the precursors of massive stars. Recent simulations have shown that interstellar shocks...
Core-Collapse Supernovae (CCSNe) are important objects in the scope of global nucleosynthesis, neutrino and gravitational waves emissions, and even cosmology. However, the early stages of these processes are not observable through the classical electromagnetic radiations observations. This is why we rely on simulations to explore the possible mechanisms leading to the final explosion. One of...
Fan-shaped jets can be observed above light bridges and are driven by reconnection of the vertical umbral field with the more horizontal field above the light bridges. Because these jets are not fully opaque in chromospheric lines, one cannot study their spectra without the highly complex considerations of radiative transfer in spectral lines from the atmosphere behind the fan.
We take...
We present a detailed study of the composition of 20 M giants in the Galactic center with 15 of them confirmed to be in the nuclear star cluster. As a control sample we have also observed 7 M giants in the Milky Way disk with similar stellar parameters. All 27 stars are observed using the NIRSPEC spectrograph on the KECK II telescope in the K-band at a resolving power of R=23,000. We report...
Stars on the asymptotic giant branch (AGB) lose a substantial part of their mass through stellar winds. Pulsations induce shock waves throughout the stellar atmosphere which compresses and elevates gas to cooler regions where dust can form. The newly formed dust particles are accelerated outwards by radiation pressure, dragging gas along, resulting in a wind. Dynamical atmosphere and wind...
M dwarfs have become an increasingly interesting target in the search for exoplanets. This is due to their small radii and low temperature which makes finding planets via both radial and transit methods easier. M dwarfs are however know to be tricky targets. The best option we have to characterise their atmospheres is using spectroscopy. This is not an easy task. M dwarf spectra are filled...
X-ray polarisation is set to open a new window into highly energetic astronomical sources like neutron stars and black holes. The upcoming launches of IXPE (a satellite-based soft X-ray polarimeter) in late 2021 and XL-Calibur (a balloon-borne hard X-ray polarimeter) in 2022 will soon provide sensitive X-ray polarisation measurements. These measurements can be used to study the strong magnetic...
Investigation of the magnetic fields on stars is important because they affect many different properties of stars at multiple stages of their evolution. The magnetic field is also a key component in the interaction between the star and its surroundings, possibly affecting habitability. The study of binaries offers a unique opportunity due to the fact that the formation of the components are...
Space and astronomy offer important opportunities for helping young people to increase their science capital. Motivated also by the UN's sustainability goals and the challenge of Earth's changing climate, Chalmers is building a new visitor centre and exhibition covering space and astronomy technology at Onsala Space Observatory, with kids in years 2-9 as a main target audience. We present...
I will present a handful of initiatives that we, the Swedish astronomical community, could choose to implement to support young researchers. In our current system, these groups (PhD students and postdocs) are the most vulnerable to exploitation, bullying, and general insecurity in their career situation.
