Annelia Anderson | Searcharxiv

arXiv2026

High-S/N Quasar Observations with HST/COS: Deep Fields for Spectroscopy

Hubble is still in prime observing condition for making transformative discoveries in UV astronomy. In this white paper we describe the science case for a deep (S/N>30) UV spectroscopic survey with HST/COS targeting approximately 20 QSOs at 0.5<z<1.5 at good resolution (20 km/s). This survey would capitalize on our current UV capability, produce a legacy dataset enabling community science in many areas of galactic and extragalactic research, and pioneer a path for future UV science with the Habitable Worlds Observatory. Such high-S/N spectra are largely missing from the MAST archives, and would be analogous to the deep Hubble imaging fields (HDF, UDF, Frontier Fields) that have been enormously successful and far-reaching in their science impact. This legacy dataset would enable frontier science programs in several areas, including (1) studies of the CGM and IGM at unparalleled sensitivity, covering a wide range of UV metal lines and reaching very low H I column densities of log N=12.6 and low metallicities near [Z/H]=-2, enabling precision studies of the chemical abundances, ionization, temperature, and baryon and metal budgets of the CGM and IGM; (2) diffuse gas in the Milky Way and Local Group, including high-velocity clouds and gas streams from satellite mergers; (3) AGN outflows, which would be probed in the rest-frame extreme ultraviolet (EUV), covering continuum-generation mechanisms and diagnostics of gas in accretion-disk outflows.

astro-ph.GA↗

arXiv2022

Coupling Semi-Analytic and N-body Galaxies (CoSANG) for cosmological stellar halo simulations I- Methods and the structure of dark matter halos

We present CoSANG (Coupling Semi-Analytic and N-body Galaxies), a new hybrid model for cosmological dark matter and stellar halo simulations. In this approach a collisionless model (Gadget3) is used for gravitational interactions while a coupled semi-analytic model (SAGE) calculates baryonic effects at each time-step. This live self-consistent interaction at each time-step is the key difference between CoSANG and traditional semi-analytic models that are mainly used for post-processing. By accounting for the gravitational effect of the baryons, CoSANG can overcome some of the deficiencies of pure N-body simulations, while being less computationally expensive than hydrodynamic simulations. Moreover CoSANG can produce stellar halo populations via tagging tracer dark matter particles. We demonstrate the performance and dynamical accuracy of this approach using both controlled test simulations and a set of three cosmological zoom-in simulations of Milky Way (MW) mass halos. We simulate each target halo both without the coupling (dark matter only, hereafter DMO) and with the coupling (CoSANG). We compare the internal structure (subhalo distribution, shape and orientation) of the halos. The following changes are observed in the CoSANG model compared to the DMO model: 1) the total number of subhaloes close to the center of the halo is reduced, 2) the $V_{\mathrm{max}}$ distribution peaks at a lower value and lies below the DMO model, 3) the axis ratio is smaller. The difference between DMO and CoSANG simulations is more significant in early forming halos.

astro-ph.GA↗