arXiv subjects

G. Santucci

Publications and source records attributed to G. Santucci.

9 recordsLinked to original sources

arXiv2026

The SAMI Galaxy Survey: Linking Tidal Features and Orbit Populations Using Schwarzschild Modelling

The evolution of angular momentum in galaxies is shaped by a combination of internal secular processes and external mechanisms such as mergers. Orbit-superposition based dynamical modelling provides a powerful means of linking the intrinsic orbital structures of galaxies to their global properties and merger histories. We construct Schwarzschild orbit-superposition models of massive ($\log(M/M_{\odot})>10$) SAMI galaxies using the DYNAMITE code, utilising deep KiDS photometry to accurately reproduce each galaxy's luminosity distribution. We find that the fractions of hot, cold, warm, and counter-rotating orbits all show significant correlations with the spin parameter proxy $\lambda_{R_e}$, with the strongest correlation arising from the combined hot plus counter-rotating fraction. When controlling for stellar mass and environment, we find that the fraction of hot and cold orbits show significant correlations with stellar age, whereas warm orbits do not. We further find that the lower values of $\lambda_{R_e}$ for young galaxies with shell merger features as compared to the full sample is driven by an excess of hot orbits and a deficit of cold orbits, with no dependence on warm orbits. We suggest that the kinematic transformation in this SAMI sample proceeds through stars transitioning directly from cold to hot orbits. As warm orbits are expected to arise from secular heating processes, these findings indicate that merger-driven heating is the dominant mechanism governing the redistribution of angular momentum and the reduction of rotational support in massive galaxies.

astro-ph.GA↗

arXiv2024

The MAGPI Survey: Evidence Against the Bulge-Halo Conspiracy

Studies of the internal mass structure of galaxies have observed a `conspiracy' between the dark matter and stellar components, with total (stars $+$ dark) density profiles showing remarkable regularity and low intrinsic scatter across various samples of galaxies at different redshifts. Such homogeneity suggests the dark and stellar components must somehow compensate for each other in order to produce such regular mass structures. We test the conspiracy using a sample of 22 galaxies from the `Middle Ages Galaxy Properties with Integral field spectroscopy' (MAGPI) Survey that targets massive galaxies at $ z \sim 0.3$. We use resolved, 2D stellar kinematics with the Schwarzschild orbit-based modelling technique to recover intrinsic mass structures, shapes, and dark matter fractions. This work is the first implementation of the Schwarzschild modelling method on a sample of galaxies at a cosmologically significant redshift. We find that the variability of structure for combined mass (baryonic and dark) density profiles is greater than that of the stellar components alone. Furthermore, we find no significant correlation between enclosed dark matter fractions at the half-light radius and the stellar mass density structure. Rather, the total density profile slope, $γ_{\mathrm{tot}}$, strongly correlates with the dark matter fraction within the half-light radius, as $γ_{\mathrm{tot}} = (1.3 \pm 0.2) f_{\mathrm{DM}} - (2.44 \pm 0.04)$. Our results refute the bulge-halo conspiracy and suggest that stochastic processes dominate in the assembly of structure for massive galaxies.

astro-ph.GA↗

arXiv2023

The MAGPI Survey: Drivers of kinematic asymmetries in the ionised gas of $z\sim0.3$ star-forming galaxies

Galaxy gas kinematics are sensitive to the physical processes that contribute to a galaxy's evolution. It is expected that external processes will cause more significant kinematic disturbances in the outer regions, while internal processes will cause more disturbances for the inner regions. Using a subsample of 47 galaxies ($0.27<z<0.36$) from the Middle Ages Galaxy Properties with Integral Field Spectroscopy (MAGPI) survey, we conduct a study into the source of kinematic disturbances by measuring the asymmetry present in the ionised gas line-of-sight velocity maps at the $0.5R_e$ (inner regions) and $1.5R_e$ (outer regions) elliptical annuli. By comparing the inner and outer kinematic asymmetries, we aim to better understand what physical processes are driving the asymmetries in galaxies. We find the local environment plays a role in kinematic disturbance, in agreement with other integral field spectroscopy studies of the local universe, with most asymmetric systems being in close proximity to a more massive neighbour. We do not find evidence suggesting that hosting an Active Galactic Nucleus (AGN) contributes to asymmetry within the inner regions, with some caveats due to emission line modelling. In contrast to previous studies, we do not find evidence that processes leading to asymmetry also enhance star formation in MAGPI galaxies. Finally, we find a weak anti-correlation between stellar mass and asymmetry (ie. high stellar mass galaxies are less asymmetric). We conclude by discussing possible sources driving the asymmetry in the ionised gas, such as disturbances being present in the colder gas phase (either molecular or atomic) prior to the gas being ionised, and non-axisymmetric features (e.g., a bar) being present in the galactic disk. Our results highlight the complex interplay between ionised gas kinematic disturbances and physical processes involved in galaxy evolution.

astro-ph.GA↗

arXiv2023

SimSpin v2.6.0 -- Constructing synthetic spectral IFU cubes for comparison with observational surveys

In this work, we present a methodology and a corresponding code-base for constructing mock integral field spectrograph (IFS) observations of simulated galaxies in a consistent and reproducible way. Such methods are necessary to improve the collaboration and comparison of observation and theory results, and accelerate our understanding of how the kinematics of galaxies evolve over time. This code, SimSpin, is an open-source package written in R, but also with an API interface such that the code can be interacted with in any coding language. Documentation and individual examples can be found at the open-source website connected to the online repository. SimSpin is already being utilised by international IFS collaborations, including SAMI and MAGPI, for generating comparable data sets from a diverse suite of cosmological hydrodynamical simulations.

astro-ph.GA↗

arXiv2021

A measurement of proton-carbon forward scattering in a proof-of-principle test of the EMPHATIC spectrometer

The next generation of long-baseline neutrino experiments will be capable of precision measurements of neutrino oscillation parameters, precision neutrino-nucleus scattering, and unprecedented sensitivity to physics beyond the Standard Model. Reduced uncertainties in neutrino fluxes are necessary to achieve high precision and sensitivity in these future precise neutrino measurements. New measurements of hadron-nucleus interaction cross sections are needed to reduce uncertainties of neutrino fluxes. We report measurements of the differential cross-section as a function of scattering angle for proton-carbon interactions with a single charged particle in the final state at beam momenta of 20, 30, and 120 GeV/c. These measurements are the result of a beam test for EMPHATIC, a hadron-scattering and hadron-production experiment. The total, elastic and inelastic cross-sections are also extracted from the data and compared to previous measurements. These results can be used in current and future long-baseline neutrino experiments, and demonstrate the feasibility of future measurements by an upgraded EMPHATIC spectrometer.

physics.ins-det↗

arXiv2020

Design and performance of a 35-ton liquid argon time projection chamber as a prototype for future very large detectors

Liquid argon time projection chamber technology is an attractive choice for large neutrino detectors, as it provides a high-resolution active target and it is expected to be scalable to very large masses. Consequently, it has been chosen as the technology for the first module of the DUNE far detector. However, the fiducial mass required for "far detectors" of the next generation of neutrino oscillation experiments far exceeds what has been demonstrated so far. Scaling to this larger mass, as well as the requirement for underground construction places a number of additional constraints on the design. A prototype 35-ton cryostat was built at Fermi National Acccelerator Laboratory to test the functionality of the components foreseen to be used in a very large far detector. The Phase I run, completed in early 2014, demonstrated that liquid argon could be maintained at sufficient purity in a membrane cryostat. A time projection chamber was installed for the Phase II run, which collected data in February and March of 2016. The Phase II run was a test of the modular anode plane assemblies with wrapped wires, cold readout electronics, and integrated photon detection systems. While the details of the design do not match exactly those chosen for the DUNE far detector, the 35-ton TPC prototype is a demonstration of the functionality of the basic components. Measurements are performed using the Phase II data to extract signal and noise characteristics and to align the detector components. A measurement of the electron lifetime is presented, and a novel technique for measuring a track's position based on pulse properties is described.

physics.ins-det↗

arXiv2019

EMPHATIC: A proposed experiment to measure hadron scattering and productioncross sections for improved neutrino flux predictions

Hadron scattering and production uncertainties are a limiting systematic on accelerator and at-mospheric neutrino flux predictions. New hadron measurements are necessary for neutrino fluxpredictions with well-understood and reduced uncertainties. We propose a new compact experimentto measure hadron scattering and production cross sections at beam energies that are inaccessibleto currently operating experiments. These measurements can reduce the current 10% neutrino fluxuncertainties by an approximate factor of two.

hep-ex↗

arXiv2018

Photon detector system timing performance in the DUNE 35-ton prototype liquid argon time projection chamber

The 35-ton prototype for the Deep Underground Neutrino Experiment far detector was a single-phase liquid argon time projection chamber with an integrated photon detector system, all situated inside a membrane cryostat. The detector took cosmic-ray data for six weeks during the period of February 1, 2016 to March 12, 2016. The performance of the photon detection system was checked with these data. An installed photon detector was demonstrated to measure the arrival times of cosmic-ray muons with a resolution better than 32 ns, limited by the timing of the trigger system. A measurement of the timing resolution using closely-spaced calibration pulses yielded a resolution of 15 ns for pulses at a level of 6 photo-electrons. Scintillation light from cosmic-ray muons was observed to be attenuated with increasing distance with a characteristic length of $155 \pm 28$ cm.

physics.ins-det↗

arXiv2016

Search for Neutrinos in Super-Kamiokande associated with Gravitational Wave Events GW150914 and GW151226

We report the results from a search in Super-Kamiokande for neutrino signals coincident with the first detected gravitational wave events, GW150914 and GW151226, using a neutrino energy range from 3.5 MeV to 100 PeV. We searched for coincident neutrino events within a time window of $\pm$500 seconds around the gravitational wave detection time. Four neutrino candidates are found for GW150914 and no candidates are found for GW151226. The remaining neutrino candidates are consistent with the expected background events. We calculated the 90\% confidence level upper limits on the combined neutrino fluence for both gravitational wave events, which depends on event energy and topologies. Considering the upward going muon data set (1.6 GeV - 100 PeV) the neutrino fluence limit for each gravitational wave event is 14 - 37 (19 - 50) cm$^{-2}$ for muon neutrinos (muon antineutrinos), depending on the zenith angle of the event. In the other data sets, the combined fluence limits for both gravitational wave events range from 2.4$\times 10^{4}$ to 7.0$\times 10^{9}$ cm$^{-2}$.

astro-ph.HE↗