arXiv subjects

Elena Arjona-Gálvez

Publications and source records attributed to Elena Arjona-Gálvez.

4 recordsLinked to original sources

arXiv2026

AGN-driven outflows in dwarf galaxies from cosmological simulations: Internal properties and observational signatures

While AGN feedback is a key driver of massive galaxy evolution, its physical properties and observational signatures in the dwarf regime remain poorly understood. We investigate the impact of AGN-driven outflows on the ISM of dwarf galaxies and assess whether these events can be robustly identified through emission-line diagnostics. We analysed a high-resolution cosmological magneto-hydrodynamical zoom-in simulation from the AURIGA project. We focused on a dwarf galaxy with 1e9.7 M*/Msun hosting a BH of 1e7 Msun. We identified individual outflow episodes via pressure peaks in the gas surrounding the central BH, tracked the thermodynamic and kinematic history of such gas, and computed synthetic, spatially resolved nebular emission using photoionisation models to construct BPT diagnostic diagrams. We show that AGN activity in this regime produces compact, over-pressurised central bubbles reaching >1e6 K temperatures. These structures accelerate the ISM up to 600km/s, exceeding those driven by stellar feedback: the outflowing material does not escape the halo, but instead decelerates and redistributes within 10kpc from the galaxy center. Synthetic emission-line modelling reveals clear, time-dependent signatures of such AGN-driven feedback. Over its life cycle, the simulated AGN-hosting galaxy traces the locus of observed dwarf AGNs and migrates from the SF sequence in the BPT diagrams through the composite region into the AGN regime, highlighting a self-regulation mechanism in which the BH accretes its fuel supply, progressively moving towards the low-ionisation nuclear region. Our results suggest that AGN-driven outflows in dwarfs primarily regulate the central ISM through episodic heating and rapid gas recycling, rather than large-scale gas ejection. These processes generate observable spectroscopic signatures, offering a promising avenue for identifying AGN feedback in low-mass galaxies.

astro-ph.GA↗

arXiv2026

Bulgeless Evolution And the Rise of Discs (BEARD) II. The role of mergers in shaping the Milky Way analogues in TNG50

We study the formation and evolution of bulgeless galaxies within the Milky Way-Andromeda analogue sample of the TNG50 simulation. Through kinematic decomposition with Mordor, we identified bulgeless galaxies with a bulge-to-disc mass ratio of B/D<0.08, in line with the Bulgeless Evolution And the Rise of Discs (BEARD) survey and Milky Way constraints. We compared them to bulge-dominated galaxies (B/D>1). We find that 74% of bulgeless galaxies experience at least one major merger (stellar mass ratio 1:4) over their lifetime. Bulgeless galaxies form later ($z_{50}\sim 0.7$) than bulge-dominated counterparts ($z_{50}\sim1.2$). Bulgeless galaxies have lower-mass haloes and higher specific stellar angular momentum, compatible with Milky Way observations. However, specific star formation rates and hydrogen gas fractions are slightly higher than Milky Way observations. Our analysis of the redshift evolution of stellar components reveals that bulgeless galaxies have gradual disc growth with high thin disc-to-total mass ratios (D/T>0.5) since $z\sim 1$ and minimal bulge growth (B/T<0.1) since $z\sim1.5$. In contrast, bulge-dominated galaxies have earlier disc formation, which is disrupted, resulting in higher morphology evolution. Bulgeless galaxies are more likely to undergo gas-rich, coplanar, and corotating mergers, promoting disc survival, compared to bulge-dominated galaxies that encounter a broader spectrum of mergers. We also observed differences in galaxy structure between bulgeless and bulge-dominated galaxies without major mergers, suggesting the relevance of early gas accretion and alignment. Bulgeless galaxies have younger stellar populations and more extended star formation histories than bulge-dominated galaxies, which rapidly quench and have older stellar populations. These findings elucidate the distinct merger-driven and secular pathways that give rise to Milky Way galaxies.

astro-ph.GA↗

arXiv2026

Bulgeless Evolution And the Rise of Discs (BEARD) III. A numerical simulation view of satellites around Milky-Way analogues

$Aims$. The existence of massive disc galaxies with little or no bulge challenges conventional $Λ$ cold dark matter model, which typically favours dynamically hot central structures due to early collapse and mergers. The study of these bulgeless disc galaxies is the aim of the Bulgeless Evolution And the Rise of Discs (BEARD) survey, as they offer a unique opportunity to investigate the link between galaxy morphology and the properties of their satellite systems. $Methods$. Using the high-resolution cosmological hydrodynamical simulation TNG50-1, we studied the satellite populations of 135 bulgeless galaxies. We compared their satellite properties to those of a bulge-dominated control sample with matched stellar masses. Our analysis focuses on satellite abundance, luminosity functions, spatial distribution, orbital alignment, and infall histories. $Results$. We find that satellite abundance is largely independent of host galaxy morphology. However, satellites around bulgeless galaxies exhibit luminosity functions with a steeper faint-end slope, are more centrally concentrated, and show stronger orbital alignment with the host disc plane. The orbital alignment originates from coherent post-infall dynamical evolution that depends on host galaxy morphology. The infall of more massive satellites can additionally perturb this process, contributing to a weakening or temporary stalling of the secular alignment. $Conclusions$. Due to the co-evolution of the host galaxy and the satellite system, the morphology of the central galaxy leaves a clear imprint on its satellite system. Bulgeless galaxies tend to have dynamically colder, more aligned, and more centrally concentrated satellite populations. These trends reflect a more quiet merger history and support the use of satellite properties as tracers of host galaxy formation pathways.

astro-ph.GA↗

arXiv2026

HI-bearing dark galaxies predictions from constrained Local Group simulations: how many and where to find them

Dark galaxies are small, DM-dominated halos whose gas remains in hydrostatic and thermal equilibrium and has never formed stars. They are of particular interest because they represent a strong prediction of the LCDM model. As of today, only a handful of candidates have been detected, the most intriguing of which being Cloud-9. Using several state-of-the-art hydrodynamical simulations, we aim to predict the abundance of dark galaxies expected within our Local Group (LG), characterise their properties and provide guidance for their potential detection. We analyse LG simulations with constrained initial conditions, run with different codes, implementing different baryonic physics, feedback prescriptions, and employing two distinct values of SF density threshold, n_th=0.13 and 10 cm^-3, to select samples of dark and bright galaxies harboured in haloes of similar mass. We demonstrate that dark galaxies exist in such simulations, though their number is larger in simulations that use a higher, more realistic n_th. These galaxies, whose gas remains diffuse and never forms stars, predominantly inhabit less-concentrated, higher-spin DM halos than their luminous counterparts. Dark galaxies are typically found in low-density regions at the outskirts of the LG, and their evolution across z indicate that both the DM and gas densities in their surroundings were consistently lower than those found around bright galaxies, making them less susceptible to interactions, mergers, or gas inflows. We estimate that up to 8 dark galaxies should be detectable in HI emission within 2.5 Mpc of the MW, with the FAST telescope, accounting for its sky coverage and minimum M_HI and N_HI. Current hydrodynamical simulations of galaxies, combined with upcoming HI surveys, will offer a direct and powerful test of LCDM through their ability to predict and measure properties of dark galaxies within and beyond the LG.

astro-ph.GA↗