First author: D. Vohl
The vast majority of extragalactic, compact continuum radio sources are associated with star formation or jets from (super)massive black holes and, as such, are more likely to be found in association with starburst galaxies or early type galaxies. Recently, two new populations of radio sources have been identified: (a) compact and persistent sources (PRS) associated with fast radio bursts (FRB) in dwarf galaxies and (b) compact sources in dwarf galaxies that could belong to the long-sought population of intermediate-mass black holes.
First author: Alexander R. Livernois
The dynamics of binary stars provides a unique avenue to gather insight into the study of the structure and dynamics of star clusters and galaxies. In this paper, we present the results of a set of $N$-body simulations aimed at exploring the evolution of binary stars during the early evolutionary phases of ultra-faint dwarf galaxies (UFD). In our simulations, we assume that the stellar component of the UFD is initially dynamically cold and evolves towards its final equilibrium after undergoing the violent relaxation phase.
First author: Ryan K. Alexander
Ultra-faint dwarf galaxies are among the oldest and most metal-poor galaxies in the cosmos, observed to contain no traces of gas at the present time and a high dark matter mass fraction. Understanding the chemical abundance dispersion in such extreme environments could shed light on the properties of the first generations of stars in the cosmos. We present a novel inhomogeneous chemical evolution model, i-GEtool, that we apply to two ultra-faint dwarf galaxies, Carina II (Car II) and Reticulum II (Ret II), which are satellites of the Large Magellanic Cloud.
First author: D. Vohl
The repeating FRB 20121102A was localized to a star-forming region in a dwarf galaxy and found to be co-located with a persistent radio source (PRS). FRB 20190520B is only the second known source sharing phenomenology akin to FRB 20121102A’s, with similar burst activity, host galaxy properties, as well as being associated with a PRS. PRS emission is potentially a calorimeter, allowing us to estimate the energy output of the central FRB engine.
First author: L. Gajović
Weakly interacting massive particles (WIMPs) can self-annihilate and thus provide us with the possibility for an indirect detection of Dark Matter (DM). Dwarf spheroidal (dSph) galaxies are excellent places to search for annihilation signals because they are rich in DM and background emission is low. If magnetic fields in dSph exist, the particles produced in DM annihilation emit synchrotron radiation. We use the non-detection of 150 MHz radio continuum emission from dSph galaxies with the LOw Frequency ARray (LOFAR) to derive constraints on the annihilation cross-section of WIMPs into electron-positron pairs.
First author: Dhruba Dutta Chowdhury
Fuzzy Dark Matter (FDM), consisting of ultralight bosons, is an intriguing alternative to Cold Dark Matter. Numerical simulations solving the Schr"odinger-Poisson (SP) equation, which governs FDM dynamics, show that FDM halos consist of a central solitonic core (representing the ground state of the SP equation), surrounded by a large envelope of excited states. Wave interference gives rise to order unity density fluctuations throughout the envelope and causes the soliton to undergo density oscillations and execute a confined random walk in the central region of the halo.
First author: E. Crosby
We present initial results of a survey of host $L_{*}$ galaxies environments in the Local Volume ($D<10,$Mpc) searching for satellite dwarf galaxy candidates using the wide-field Hyper Suprime-Cam imager on the 8m Subaru Telescope. The current paper presents complete results on NGC2683 ($M_{B_T,0}=-19.62$, $D=9.36,Mpc$, $v_{\odot}=411,km,s^{-1}$), an isolated Sc spiral galaxy in the Leo Spur. At the distance of NGC2683, we image the complete volume out to projected radii of $380,kpc$ using a hexagonal arrangement of 7 pointings.
First author: Oliver Müller
Dark matter clusters on all scales, therefore it is expected that even substructure should host its own substructure. Using the Extragalactic Distance Database, we searched for dwarf galaxy satellites of dwarf galaxies, i.e. satellite-of-satellite galaxies, corresponding to these substructures-of-substructure. Going through HST data of 117 dwarf galaxies, we report the discovery of a dwarf galaxy around the ultra-diffuse M96 companion M96-DF6 at 10 Mpc. Modelling its structural parameters, we find that it is an ultra-faint dwarf galaxy which is 135 times fainter than its host.
First author: Matthew D. A. Orkney
We investigate the properties of mergers that are comparable to the Gaia-Sausage-Enceladus (GSE) using cosmological hydrodynamical simulations of Milky Way-like galaxies. It was previously shown that these mergers occur over a wide range of times ($6-10,$Gyr ago). We find that the merger progenitors span an order of magnitude in their peak stellar mass ($3\times10^8<M_{\star}/\rm{M}{\odot}<4\times10^9$) and include both rotation and pressure-supported galaxies ($0.10<D/T<0.77$). In a minority of cases, the GSE-like debris is comprised of stars from more than one merger progenitor.
Anna Frebel
This chapter presents an overview of the recent progress on spectroscopic observations of metal-poor stars with r-process element signatures found in the Milky Way's stellar halo and satellite dwarf galaxies. Major empirical lessons related to the origins of the r-process are discussed, including the universality of the observed r-process pattern and deviations from universality among the light r-process elements and actinides. Different astrophysical sites of the r-process based on theoretical expectations are presented, including common and rare supernovae and neutron star mergers.
