First author: Bradley C. Whitmore
A long-standing problem when deriving the physical properties of stellar populations is the degeneracy between age, reddening, and metallicity. When a single metallicity is used for all star clusters in a galaxy, this degeneracy can result in $$catastrophic$'$ errors for old globular clusters. Typically, approximately 10 - 20 % of all clusters detected in spiral galaxies can have ages that are incorrect by a factor of ten or more.
First author: Harry T. J. Bevins
Observations of the first billion years of cosmic history are currently limited. We demonstrate the synergy between observations of the sky-averaged 21-cm signal from neutral hydrogen and interferometric measurements of the corresponding spatial fluctuations. By jointly analysing data from SARAS3 (redshift $z\approx15-25$) and limits from HERA ($z\approx8$ and $10$), we produce the tightest constraints to date on the astrophysics of galaxies 200 million years after the Big Bang.
First author: J. M. DerKacy
We present a JWST/MIRI low-resolution mid-infrared (MIR) spectroscopic observation of the normal Type Ia supernova (SN Ia) SN 2021aefx at +323 days past rest-frame B-band maximum light. The spectrum ranges from 4-14 um, and shows many unique qualities including a flat-topped $[Ar III]$ 8.991 um profile, a strongly tilted $[Co III]$ 11.888 um feature, and multiple stable Ni lines. These features provide critical information about the physics of the explosion.
J. M. Diego
We present a free-form model of SMACS0723, the first cluster observed with JWST. This model makes no strong assumptions about the distribution of mass (mostly dark matter) in the cluster and we use it to study the possible correlation between dark matter with the intracluster light and distribution of globular clusters. To explore the uncertainty in mass modelling, we derive three lens models based on spectroscopically confirmed systems and new candidate systems with redshifts predicted by the lens model derived from the spectroscopic systems.
First author: William Sheu
The introduction of deep wide-field surveys in recent years and the adoption of machine learning techniques have led to the discoveries of $\mathcal{O}(10^4)$ strong gravitational lensing systems and candidates. However, the discovery of multiply lensed transients remains a rarity. Lensed transients and especially lensed supernovae are invaluable tools to cosmology as they allow us to constrain cosmological parameters via lens modeling and the measurements of their time delays.
Francois Hammer
Halo inhabitants are individual stars, stellar streams, star and globular clusters, and dwarf galaxies. Here we compare the two last categories that include objects of similar stellar mass, which are often studied as self-dynamical equilibrium systems. We discover that the half-light radius of globular clusters depends on their orbital pericenter and total energy, and that Milky Way (MW) tides may explain the observed correlation. We also suggest that the accretion epoch of stellar systems in the MW halo can be calibrated by the total orbital energy, and that such a relation is due to both the mass growth of the MW and dynamical friction affecting mostly satellites with numerous orbits.
First author: Scott A. Tompkins
We present a revised measurement of the extra-galactic background light (EBL) at radio frequencies based on a near complete compendium of radio source counts. We present the radio-EBL at 150 MHz, 325 MHz, 610 MHz, 1.4 GHz, 3 GHz, 5 GHz, and 8.4 GHz. In all cases the contribution to the radio-EBL, per decade of flux, exhibits a two-humped distribution well matched to the AGN and star-forming galaxy (SFG) populations, and with each population contributing roughly equal energy.
First author: Frederick Groth
Subsonic turbulence plays a major role in determining properties of the intra cluster medium (ICM). We introduce a new Meshless Finite Mass (MFM) implementation in OpenGadget3 and apply it to this specific problem. To this end, we present a set of test cases to validate our implementation of the MFM framework in our code. These include but are not limited to: the soundwave and Kepler disk as smooth situations to probe the stability, a Rayleigh-Taylor and Kelvin-Helmholtz instability as popular mixing instabilities, a blob test as more complex example including both mixing and shocks, shock tubes with various Mach numbers, a Sedov blast wave, different tests including self-gravity such as gravitational freefall, a hydrostatic sphere, the Zeldovich-pancake, and the nifty cluster as cosmological application.
First author: Divya Rana
We present the splashback radius measurements around the SRG/eROSITA eFEDS X-ray selected galaxy clusters by cross-correlating them with HSC S19A photometric galaxies. The X-ray selection is expected to be less affected by systematics related to projection that affects optical cluster finder algorithms. We use a nearly volume-limited X-ray cluster sample selected in 0.5-2.0 keV band having luminosity $L_X > 10^{43.5} {\rm erg s^{-1} h^{-2}}$ within the redshift $z<0.
First author: Asa F. L. Bluck
We identify the intrinsic dependence of star formation quenching on a variety of galactic and environmental parameters, utilizing a machine learning approach with Random Forest classification. We have previously demonstrated the power of this technique to isolate causality, not mere correlation, in complex astronomical data. First, we analyze three cosmological hydrodynamical simulations (Eagle, Illustris, and IllustrisTNG), selecting snapshots spanning the bulk of cosmic history from comic noon ($z \sim 2$) to the present epoch, with stellar masses in the range $9 < \log(M_/M_{\odot}) < 12$.
