Master Thesis Proposals: Astrophysics and Space Science

Transient sources in the high energy (HE, GeV) and very-high energy (VHE, TeV) gamma-ray domain have turned out to be excellent laboratories to test particle acceleration, emission, and absorption processes under extreme conditions, thanks to the multiple discoveries of transient phenomena at GeV and TeV energies reported during the last decade [1]. These transients can have either a Galactic origin (e.g., Novae explosions, flares from Pulsar Wind Nebulae, outbursts from binary systems like Microquasars, Gamma-ray Binaries, Magnetars or Accreting Millisecond Pulsars, or even Supernova explosions), or an extragalactic nature (e.g., flares from Active Galactic Nuclei, Gamma-ray Bursts, or electromagnetic counterparts to Gravitational Waves or Neutrino alerts reported by dedicated observatories). 

For the follow-up of these short-lived events in gamma-rays, Cherenkov telescopes like MAGIC, H.E.S.S. and VERITAS operating in the VHE domain are particularly well suited given their large collection areas. In the near future, the Cherenkov Telescope Array (CTA) is being designed to be the next generation ground-based observatory for gamma-ray astronomy at VHEs [2]. It will be composed of telescopes of different sizes and will be installed in two sites, at Paranal (Chile) in the southern hemisphere and at the Observatorio del Roque de los Muchachos (ORM) in the Canary Island of La Palma in the northern hemisphere. The Large Size Telescopes (LSTs), featuring 23-m diameter dish reflectors, will be the largest telescope class of CTA. The first LST prototype, the LST-1 is finishing its commissioning phase and is already starting to produce relevant scientific data [2]. 

In this Master Thesis Project, we will make use of the Group’s affiliation to LST-CTA to analyze scientific data of a transient source observed with LST-CTA. On the other hand, the Thesis should also provide with a physical interpretation of the processes taking place in the observed transient source. We emphasize that acquiring expertise in the analysis and interpretation of LST-CTA in these first stages of its scientific operations will bring a unique opportunity to carry out future studies on gamma-ray sources with CTA. 

A leading candidate to explain the existence of dark matter in the Universe is the axion, which is detectable in experiments that use resonant cavities embedded in a strong magnetic field to turn an ambient axion of the dark matter halo of the Milky Way into a resonant photon. Superconducting qubits can be used to detect these photons without absorbing them, allowing for multiple detections of the same photon with minimal noise at mK temperatures, as demonstrated by Dixit et al. 2019. One of the collaborations working to make this detection possible is RADES, as part of the International IAXO Collaboration, of which the University of Barcelona is a member. 

Two master thesis are proposed to develop this project in the context of the RADES Collaboration. Im the first, the goal is to acquire experience working with qubits to reliably perform these single-photon detections, to reproduce the results of measurements of the quantum state of the qubit that indicates the presence or absence of a resonance photon, measure the qubit coherence time in different physical conditions, and optimize the detection and analysis method. For this, the master student will travel to work with RADES collaborators in Paris or Aalto (Finland) where the cryogenic laboratories and qubits to be used will be available. 

The second master thesis project focuses on tuning of the cavity resonant frequency by means of a ferromagnetic crystal inserted into the cavity that modifies the frequency through a variation of the magnetic permeability of the crystal with the magnetic field strength. This experimental project is to be performed in collaboration with the ICMAB, where a 16T magnet will be used to test a cavity and crystal developed in RADES.

GMV offers the possibility to participate on a remunerated project for the final master work (TFM). The number of satellites being launched into orbit has grown exponentially in the last years [1]. Even though they provide valuable information, they also create important challenges and concerns regarding their possible impact on the sky quality, their effect on astronomical observations or the space traffic management (see, e.g., [2] and [3]). For this reason, having a good understanding of the CubeSat and other very faint object (VFO) population is mandatory to address any possible threats. The main difficulty to understand the possible threats of VFOs is its relatively small size (down to 10 cm). Following the exact position of these space objects becomes a very challenging task, even for the largest telescopes dedicated to space traffic management (see, e.g., [2]). For this reason, studying the possibility to follow VFOs with larger telescopes becomes a natural development in space traffic management. The current TFM will focus on the use of 2-m class telescopes to study its possible use to characterize the VFO population. During this TFM, the student will learn how to prepare an observation plan to follow artificial satellites with Senplanner, how to prepare and execute the observations in a 2-meter class telescope, to perform the astrometric reduction of the images obtained with Gendared and to use orbit determination tools to accurately determine the orbit of VFOs with Sstod.

The VLA Orion A Large Survey (VOLS) large project will perform the deepest survey at subarcsecond resolution of the Orion A molecular cloud with the Karl G. Jansky Very Large Array (PI: G. Busquet, see  https://vols.fqa.ub.edu).  The superb sensitivity of the VLA combined with the large field of view of VOLS (~1 deg x 0.5 deg) requires a new strategy to identify regions of line emission. The VOLS project includes the emission lines of OH and CH3OH masers, 18 Hydrogen Radio Recombination lines and the line thermal emission of HC5N and SO molecules. The goal of this Master Thesis is to develop automatic algorithms based on Deep Learning/Machine Learning techniques to identify regions of line emission in the visibility domain. This is crucial for the next generation of radio interferometers such as the Square Kilometre Array (SKA) or the next generation VLA (ngVLA), which will perform deep surveys over large areas in the sky being 10 times more sensitive than the current radio facilities.

cOrion A is the nearest star-forming complex containing a broad range of environments populated by protostars and Young Stellar Objects (YSOs) with different masses and evolutionary stages, representing a testbed for star formation theories. The VLA Orion A Large Survey (VOLS, PI: G. Busquet; see https://vols.fqa.ub.edu) large project has been granted with 306 hours of observing time with the Karl G. Jansky Very Large Array to perform the deepest survey at subarcsecond resolution of the Orion A molecular cloud. VOLS will observe at two frequency bands (8-12 GHz or 6 cm and 12-18 GHz or 2 cm) the northern part of the Orion A molecular cloud covering an area of ~0.5 deg2. The aim of the Master Thesis is identify non-thermal emitters in the VOLS field of view and investigate the origin of this emission. Non-thermal emission is characterised by a negative spectral index and it can be associated to shocked spots in the radio jets or stellar winds due to synchrotron emission or to very active magnetospheres in Class II/Class III YSOs.

The formation process of stellar cluster requires a high degree of cloud fragmentation. Both simulations and observations show that cloud fragmentation leading to the formation of stellar cluster is controlled by a complex interaction of gravitational instability, turbulence, magnetic fields, cloud rotation, and stellar feedback. The infrared dark cloud G14.225-0.506 hosts two hubs harbouring two deeply embedded protoclusters. All derived physical properties (density and temperature structures, level of turbulence, cloud rotation, and magnetic field strength) are remarkably similar despite they present different levels of fragmentation. The aim of this project is to investigate whether the different fragmentation is due to evolutionary effects and/or due to the external UV radiation field. This will be done by analysing observations from the Submillimter Array (SMA) at 1mm and from the NOEMA interferometer at 3 mm. The continuum emission, by means of the spectral index, can be related to grain growth of dust, while the chemical composition of the clusters members provides information on the evolutionary stage and the physical conditions.

The large-scale structure of the universe commonly refers to the distribution of galaxies at scales above 100Mpc, spanning across a wide range of redshifts, 0<z<3. This is currently one of the wealthiest sources of cosmological information in modern cosmology exploited by surveys such as the Dark Energy Spectroscopic Instrument (DESI, https://www.desi.lbl.gov/) or the EUCLID mission (https://sci.esa.int/web/euclid). In this TFM the student will be able to choose one of the hot-topic in cosmology today: 1)  studying and exploiting the techniques to measure the expansion history of the universe and the effect of Dark Energy through Baryon Acoustic Oscillations; 2) understanding the theory of gravity that rules at inter-galactic scales through Redshift Space Distortions; 3) studying the impact of neutrinos on the distribution of matter and galaxies at large scales; 4) employing higher-order statistics to measure gravitational and/or primordial non-Gaussianities and study their connection to the inflationary era;  just as a few examples. The student will have the opportunity to work with several members of the cosmology unit at the ICCUB and use real data from the DESI survey, in which the cosmology team is highly involved.

The quality of GaiaDR3 proper motions make them suitable for mapping for the first time the 3D velocity field of the Large Magellanic Cloud disc kinematics. These maps show a high degree of complexity and comparison with controlled N-body simulations becomes essential. We plan to use  KRATOS simulations, a suite of 24 LMC-like N-body simulations, to understand the disc kinematics and transform them to a Gaia mock catalogue and/or an Euclid mock catalogue.

The gravitational interaction between the Large Magellanic Cloud (LMC) and the Small Magellanic Cloud is evident when GaiaDR3 reveals the shape of the Magellanic bridge in the young stellar evolutionary phase and the velocity flow also in older and evolved populations. The imprint of the interaction in the LMC in-plane velocity field is not clear. The radial velocity field in the outer parts of the disc of the LMC is not consistent with a disc in equilibrium. We plan to use the KRATOS simulations, a suite of 24 LMC-like N-body simulations, to analyse the effect of the SMC on the LMC disc kinematics.

The radial and residual tangential velocity map in the Large Magellanic Cloud bar with GaiaDR3 data shows that the expected quadrupole pattern is asymmetric. We plan to analyse the cause of asymmetries using KRATOS simulations, a suite of 24 LMC-like N-body simulations.

Gamma-ray emitting binaries hosting a massive star are among the most efficient and powerful accelerators of the Galaxy. The closest vicinity of the binary is believed to be the region where electrons (and possibly protons and nuclei) are accelerated, reaching in some cases energies approaching 100 TeV. This implies that these sources are potential Pevatrons, in particular if protons and nuclei are also accelerated, as they are less affected by energy losses than electrons, close to the binary. However, once the particles are accelerated, they will have to propagate a large distance before reaching the interstellar medium (ISM), if they are to contribute to the Galactic cosmic rays. These particles may suffer adiabatic losses in the way, which would strongly reduce the energy at which they are injected in the ISM. This project aims at calculating the energy evolution of cosmic rays after being accelerated close to the binary system, and while they are transported by the powerful outflows emerging from those regions.

In the last decade very-high-energy (VHE) astronomy has emerged as a new astronomical window, allowing for the study of the most extreme astrophysical processes in our Universe. The current generation of Cherenkov Telescopes H.E.S.S, MAGIC and VERITAS has revealed the presence of about two hundred of such VHE sources in the gamma-ray sky [1]. This is however just the tip of the iceberg, and the improved capabilities of the next generation of instruments, the Cherenkov Telescope Array (CTA) [2], is expected to increase this number by about one order of magnitude. 

Among the VHE sources that CTA will be able to study in detail, Galactic sources are particularly interesting, as they offer the opportunity to deepen into the physics leading to the observed gamma-ray emission both from a spectral and a morphological perspective. The improved capabilities of CTA in sensitivity and angular resolution will allow a detailed characterization of the high-energy processes taking place in pulsars and pulsar wind nebulae (PWNe), Gamma-ray binaries (GBs), microquasars (MQs), Supernova Remnants (SNRs), Novae explosions or Galactic Stellar Clusters (GSCs). 

In this Master Thesis project, we will study the VHE emission from Galactic sources as observed with CTA. The candidate will make use of dedicated simulation and analysis pipelines (Python-based) to retrieve the observation strategy and the array configuration required to constrain the timing, morphology, and spectral properties of these sources. Mastering these CTA pipelines will also provide the candidate with the needed expertise on the analysis of high-level scientific data on a given Galactic/Extragalactic VHE gamma-ray source that the observatory will deliver (open-source) in the next years.

Molecular outflows are among the most conspicuous manifestations of a nascent star. These outflows are known to result from the entrainment of circumstellar gas, swept up by the primary jet, where a shock front is generated as a consequence of the supersonic impact of the jet with the natal cloud. Shocks heat, accelerate, and compress the ambient gas material switching on a complex chemistry that leads to an enhancement of the abundance of several species. The goal of this project is to investigate the physical conditions of the Herbig-Haro object HH377 of the Cepheus E outflow using spectroscopic data from PACS instruments onboard of Herschel satellite. The observational results will be compared with the shock-model predictions to understand the nature of the HH 377 shock.

In this project, the student will use publicly available high-resolution simulations of Milky-Way-like galaxies (e.g. from the APOSTLE, NIHAO, Auriga projects, [1]) and compare the chemo-kinematic properties to new spectroscopic and astrometric observations of millions of stars in the Milky Way. All simulations were tailored to resemble our Galaxy, but which one comes closest when we look at the details?

The mere existence of large stellar datasets and high-resolution simulations is insufficient to ensure a major knowledge gain about the formation and evolution of our Galaxy. Many datasets are subject to non-trivial selection effects, systematic uncertainties (especially for ages of field stars), and correlated errors that impede straightforward conclusions and affect simplistic model-to-data comparisons [2,3]. There is now an urgent need for more quantitative comparisons of Gaia observations to state-of-the-art Milky Way models and clear indications where such models should be improved.

In this project the student will learn to analyse complex observational and simulation data with python, and how to make physical sense of them. Basic knowledge of Galactic astronomy, statistics, and python programming are necessary.

It is expected that about 10^8 isolated black holes (IBH) produced by stellar evolution populate the Galaxy. These objects are expected to accrete from the medium, subsequently producing winds, thermal emission, and potentially, jets and non-thermal energetic radiation. The aim of this project is to estimate the number of IBH that could fill the densest regions of the Galaxy, and explore whether relatively
nearby objects could be detectable from the Earth. As dense environments make detection difficult due to absorption, only the most energetic non-thermal emission will be considered.

Dark Matter constitutes most of the matter in the Universe, but we do not know what it is. The detailed study of orbital motions of galaxies may lead to the discovery of new clues to the nature of dark matter.

New data from the Gaia mission and other observations of nearby dwarf galaxies opens a new opportunity: we are now measuring not only sky positions and redshifts for many stars and dwarf galaxies in the Local Group, but also proper motions and distances. The project will explore a simple way of computing the orbital evolution of many dwarf galaxies
in our Local Group, from the original Hubble expansion after the Big Bang to the present collapse of the Local Group and tidal disruption of dwarfs generating tidal tails. This will combine simple techniques of cosmological simulations
and Local Group dynamical modeling.

The Transiting Exoplanet Survey Satellite (TESS) [1] is delivering outstanding results in several areas of planetary science.

The two largest TESS catalogs of stellar flares have been just released: [2,3] and [4], respectively. These comprise ~25,000 M-dwarfs and ~200,000 FGKM studied stars, both with 2 min. cadence, observed during the first two TESS sectors and the first two years of the mission, respectively.

Our multidisciplinary team, is involved in the study of M-dwarfs flares and their implications in exoplanets habitability. This way, the ultimate goal of this MSc Thesis is to develop from [5] a flare-exoplanet atmosphere interaction photo-chemistry model.
This model should be able to provide depleted/catalyzed species rates, and finally be validated by the observed TESS flare frequency distributions.

More in detail, the student will:
1-get a working sample of flaring stars from TESS flares catalogs,
2-obtain the stellar parameters for the flaring stars,
3-obtain a sub-sample of flaring stars with known transiting planets,
4-obtain the orbital elements from the previous planets,
5-get another sub-sample with only those planets within the habitable zone,
6-as regard as the adaptation and implementation of the photo-chemistry model in [5],
this project considers two distinct evolutionary scenarios:
6.1-the current Earth atmosphere, where the ozone depletion would be the species to model,
6.2-the putative Archean Earth atmosphere, where prebiotic chemistry processes linked to species,
such as SO^2−_3 and HS^− [6], could be catalyzed by UV radiation from flares.

The outer disc of the Milky Way (MW), where orbital timescales are of the order of ~1Gyr holds valuable information about the Galaxy's past and current interactions with satellite galaxies. These interactions cause the formation of tidal arms in the outer disc which remain coherent over several Gyrs and can be witnessed at present as long thin stream-like structures with witdth ~1-10 degrees and spanning lengths of ~180degrees on the sky. The dynamic of these tracer structures is simple, following a single particle orbit which can be exploited to measure the potential and its flattening close to the midplane (Laporte et al. 2019).

In this project, we will use the Anticenter Stream (ACS, Grillmair 2006) to constrain the potential and its flattening in the midplane at ~20kpc (similarly to Koposov 2010). This will also probe the impact of baryons on the sphericalisation of dark matter halos. We will map the ACS in 6-D using the astrometric data from Gaia eDR3 combined with radial velocities from legacy surveys (APOGEE, SEGUE, LAMOST) and fit the orbit of the ACS stream. The results and robustness of the method will also be compared with self-consistent N-body simulations of the interaction of the Milky Way with Sagittarius (Laporte et al. 2018).

The Gaia data release revealed that the stellar halo is dominated by a highly anisotropic and non-Gaussian structure pointing to the remains of a massive merger at high-redshift now better known as the Gaia-Sausage-Enceladus (GSE) merger event (Belokurov et al. 2018, Helmi et al. 2018). While much work has focused on the properties of the Sausage (e.g. Fattahi et al. 2019), little is known about its satellite population (Bose et al. 2020). The aim of this project is to shed some light on the population of galaxies that came with the Sausage galaxy through group infall.

In this project we aim to characterize the accretion history of the Milky Way using a statistical sample of MW-like realisations in order to place the Galaxy in a cosmological context. We will look for systems with accretion histories resembling that of the Galaxy (e.g. those with Gaia-Sausage-Enceladus-like satellites merging at high-z vs those without) and characterise their population of satellite galaxies in particular at the low-mass end (the so-called ultra-faint galaxies, UFDs). We will use the Munich semi-analytic model (Henriques et al. 2020) to track the evolution of ultra-faints and identify systems GSE-host MW-like systems and characterise their luminosity function and chemical properties of their UFDs and compare them to rest of the population of MW-like halos. We will then also look into Auriga (Grand et al. 2017) and TNG50 to find analogues of the Sausage and study their satellite they brought with them as well as their survival and compare them with observations of the stellar halo with Gaia and legacy spectroscopic surveys. Interesting systems will be used to set-up some dynamical numerical experiments to study the fate, distribution and properties of the remains of the galaxies brought with the GSE merger.

Determining the structure of the Galactic disc in the optical in the midplane through photometry alone is complicated due to the presence of dust. Recently, using the kinematic information provided by the Gaia eDR3 data, a new map of the Milky Way's outer disc was presented (Laporte et al. 2021) revealing a hierarchy of substructure in the disc using a peak detection algorithm inspired by those used to identify halo centers in cosmological simulations (Power et al. 2003). Nonetheless this is only the tip of the iceberg as close inspection reveals the presence of multiple kinematic peaks coinciding on the sky at a given position on the Celestial sphere. How long and extended are the various coherent disc stream-like structures, what is their overall kinematics, chemistry, age distribution of their stellar populations? Are all these substructures excited as a result of kinematic perturbations from satellite galaxies or do they represent folds in the disc seen in projection?

In this project you will devise an algorithm to refine the current algorithm and identify substructure across the whole disc using data from the Gaia satellite beyond the volume probed by the radial velocity survey (RVS). You will track every peak and connect them as individual coherent structures using Gaussian Mixture models (e.g. Bovy 2011). One obvious application would be to better characterise the outer disc of the Milky Way by dissecting it in a coherent way, but one could equally apply the algorithm to study other parts of the Galaxy (e.g. the bar) if time allows it.

When a massive satellite merges within a larger host, it sinks through dynamical friction which not only leaves a wake of particles behind the satellite but also carries out large scale disturbances in the halo which can propagate all the way down to the disc causing warps to form (Weinberg 1998). This sloshing of the dark matter halo acts on larger timescales than direct tidal interactions with the main body of a satellite with the disc and its long-term effects on Galactic discs is not fully understood/known. In this project, you will investigate the effect of the dark matter halo wakes and tides from satellites on discs using a Basis Function Expansion code (EXP, Petersen et al. 2021) to re-simulate to much higher resolution the interaction of a Milky Way-like galaxy in the presence of Sagittarius from a self-consisten N-body run (Laporte et al. 2018) to study the response of the outer disc to a sloshing halo on an extended timescale and the type of fine-grained signatures this leaves imprinted on a disc and compare it with observations in the Milky Way (Laporte et al. 2021).

The most distant quasars provide important clues to the formation of supermassive black holes at the early Universe.  First data for those quasars are usually discovery spectra in the rest-frame UV band, taken by optical telescopes. They contain a few imprints of nuclear activities, such as outflows, as well as Lyman alpha emission for determining their redshifts. The SHELLQs project using the Subaru HSC survey discovered more than 160 quasars, mainly in the lower-luminosity regime, at redshift ranging from 5.7 to 7.1, corresponding to the epoch ~1 Gyr after the Big Bang. The data of their discovery spectra are available and their shapes could be grouped into a limited number of types. The main task is to classify these spectra and identify the most important feature to characterise each type. At the same time, a student is expected to learn  the basic knowledge of quasars: how the large energy output of quasars is generated, how those high-redshift quasars can be discovered, what are the important questions to be answered as to the formation of supermassive black holes.

Interactions between galaxies have been studied since long ago. However, the impact of nearby dwarf galaxies on the disk of the Milky Way has been the focus of relatively fewer recent studies. Some of the disturbances seen in the Gaia data (substructures in the R-Vphi plane or the phase spiral) can be due to the past interactions of our Galaxy with the Sagittarius dwarf that approached in several past pericenters. Typically, these interactions leave imprints in the phase space of the perturbed disk that persist but transform with time (phase mixing or self-gravitating). In this project we will study the different imprints that different orbits of the perturber satellite galaxy produce in a disk and how these imprints evolve with time. We will compare these models to a more realistic simulation and evaluate how much the observed imprints can tell us about the conditions of the interactions in the pericenter times.

In this project the student will learn to analyse different simulations (from simple toy models to zoom-in cosmological simulations) and to use Gaia data.