galaxies

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: Andrew J. Levan The majority of long duration ($>2$ s) gamma-ray bursts (GRBs) are believed to arise from the collapse of massive stars \cite{Hjorth+03}, with a small proportion created from the merger of compact objects. Most of these systems are likely formed via standard stellar evolution pathways. However, it has long been thought that a fraction of GRBs may instead be an outcome of dynamical interactions in dense environments, channels which could also contribute significantly to the samples of compact object mergers detected as gravitational wave sources.

First author: Gopika K. A large number of observations have shown that the dark matter halo surface density, given by the product of halo core radius and core density is nearly constant for a diverse suite of galaxies. Although this invariance of the halo surface density is violated at galaxy cluster and group scales, it is still an open question on whether the aforementioned constancy on galactic scales can be explained within $\Lambda$CDM.

First author: Polychronis Papaderos Since the k correction depends on the spectral energy distribution (SED) of a galaxy, any high-z galaxy with a spatially non-homogeneous SED will experience a spatially varying relative dimming or brightening in addition to the pure distance effect. The morphology of galaxies will therefore change with z. For instance, an early spiral galaxy observed in the V band would show a prominent bulge at z=0, whereas, if at z=1, the V filter probes the rest-frame near-UV where the bulge is faint and the disk relatively brighter, thus the galaxy may appear as bulgeless.

First author: Yi Xu We present demography of the dynamics and gas-mass fraction of 33 extremely metal-poor galaxies (EMPGs) with metallicities of $0.015-0.195~Z_\odot$ and low stellar masses of $10^4-10^8~M_\odot$ in the local universe. We conduct deep optical integral-field spectroscopy (IFS) for the low-mass EMPGs with the medium high resolution ($R=7500$) grism of the 8m-Subaru FOCAS IFU instrument by the EMPRESS 3D survey, and investigate H$\alpha$ emission of the EMPGs. Exploiting the resolution high enough for the low-mass galaxies, we derive gas dynamics with the H$\alpha$ lines by the fitting of 3-dimensional disk models.

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: Ece Kilerci We report on 167 infrared (IR) galaxies selected by AKARI and IRAS and detected in the Atacama Cosmology Telescope (ACT) Data Release 5 (DR5) sky maps at the 98, 150 and 220 GHz frequency bands. Of these detections, 134 (80%) of the millimeter counterparts are first-time identifications with ACT. We expand the previous ACT extragalactic source catalogs, by including new 98 GHz detections and measurements from ACT DR5.

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: Floor van Donkelaar Nuclear star clusters (NSCs) are massive star clusters found in the innermost region of the majority of galaxies. While recent studies suggest that low-mass NSCs in dwarf galaxies form largely out of the merger of globular clusters and NSCs in massive galaxies have assembled most of their mass through central star formation, the formation channel of the Milky Way’s NSC is still uncertain. In this work, we use GigaEris, a very high resolution $N$-body hydrodynamical cosmological zoom-in'' simulation, to investigate NSC formation in the progenitor of a Milky Way-sized galaxy, as well as its relation to the assembly and evolution of the galactic nuclear region.

First author: R. K. Cochrane Without AGN feedback, simulated massive, star-forming galaxies become too compact relative to observed galaxies at z<2. In this paper, we perform high-resolution re-simulations of a massive (M*~10^11M_sol) galaxy at z~2, drawn from the FIRE project. In the simulation without AGN feedback, the galaxy experiences a rapid starburst and shrinking of its half-mass radius at z~2.3. In this paper, we experiment with driving mechanical AGN winds using a state-of-the-art hyper-Lagrangian refinement technique to increase particle resolution.