Master thesis proposals: Astrophysics and Space Science

Title: The role of the first non-massive stars in the chemical evolution of the early universe.

Advisor: Pilar Gil-Pons

Abstract:: The nature of the first stellar generations and their role in the evolution of the early universe has been a matter of debate during the last decades. Recent 3D hydrodynamical simulations of stellar formation support the occurrence of low- and intermediate-mass primordial (or metal-free) stars. However, the traditional view was that the first stars had to be massive. As a consequence the evolution, the nucleosynthetic yields, and the contribution to the chemical evolution of the universe, of the most metal-poor non-massive stars is not thoroughly understood.

We aim to develop techniques to compare the observed surface abundances of the most metal-poor stars in the Galactic halo to the recently calculated yields of low- and intermediate-mass stars of metallicity Z≲10-5 .Results will be analysed in order to draw conclusions on the role of these stars in the evolution of the early universe.

Contact e-mail:


Title: Characterizing filaments harboring high-mass star formation

Advisor: Gemma Busquet, Robert Estalella

Abstract:: Filaments are ubiquitous structures in star-forming complexes, which often intersect in high-density regions associated with star formation, known as hub-filament systems. Despite filaments having been recognized more than 30 years ago, the ubiquity of such structures in star-forming regions, which has been recently highlighted by Herschel programs, has brought special attention to their formation mechanism and their role in the star formation process. The aim of this project is to analyze the (J,K)=(1,1) and (J,K)=(2,2) inversion lines of ammonia (NH3) obtained with the 100m Green Bank Telescope to derive the main physical properties of two filamentary Infrared Dark Clouds using the hyperfine structure technique.


[1] Estalella, R. "HfS, Hyperfine Structure Fitting Tool" 2016, PASP in press (arXiv: 1608:04088)

[2] André, P. , Di Francesco, J. ,Ward-Thompson, D. Inutsuka, S.-I., Pudritz, R.E., Pineda, J.E. "From Filamentary Networks to Dense Cores in Molecular Clouds: Toward a New Paradigm for Star Formation" 2014 Protostars and Planets VI, 27-51.

Contact e-mail: ,

Title: Unveiling the nature of the HH377 shock throught Herschel-PACS observations

Advisor: Gemma Busquet, Robert Estalella

Abstract:: 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.


[1]  Flower, D.R. & Pineau Des Forêts, G. 2010, MNRAS 406, 1745

[2] Hollenbach, D. & McKee C.F. 1989, ApJ 342, 305

[3] Lefloch, B. , Gusdorf, A., Codella, C., Eislöffel, J. , Neri, R. , Gómez-Ruiz, A. I., Güsten, R. , Leurini, S., Risacher, C. & Benedittini, M. 2015, A&A, 581, A4

contact e-mail:


Title: Finding an accurate fitting formula for major merger timescales

Adivsor: Josep Maria Solanes

Abstract:: The student will perform binary major merger simulations of galaxies using pre-prepared, cosmologically consistent N-body model and compare the measured timescales with theoretical predictions available from the literature based on the Chandrasekhar formula [e.g. 1,2,3]. The simulations will probe different mass ratios, orbital configurations, halo spins, galaxy morphologies, and orbital energies. Recent calculations [4] have shown that existing analytical predictions, which apply to a wide range of M_sat/M_host ratios, systematically overpredict timescales for major mergers. The main goal of this work is to propose a new, easily implementable fitting formula that accurately predicts the merger timescales in the range M_sat/M_host > 0.25.

Requirements: a minimum level of computer literacy.


[1] Jiang, C.Y. et al. 2008, ApJ, 675, 1095

[2] Boylan-Kolchin, M., Ma C.-P. & Quataert, E. 2008 MNRAS, 383, 93

[3] McCavana, T., et al. 2012, MNRAS, 424, 361

[4] Solanes, J.M., et al, in preparation


contact e-mail:


Title : Detection of Ultra Faint Dwarf Galaxies in the halo as probes for cosmological models

Advisor: F. Figueras, T. Antoja

Abstract:: Several galaxies with very low luminosity and surface brightness, dominated by dark matter, called "Ultra Faint Dwarf Galaxies" (UFDGs), have been found in the halo of the Milky Way. The detection of more of these systems is extremely relevant for the so-called "missing satellite problem", which is a dramatic discrepancy between the observed number of galaxy satellites and the large number predicted by the state-of-the-art cosmological Lambda-CDM simulations. The Second Data Release of the Gaia catalogue will have full sky coverage and stellar kinematics to review this problem. With the aim to obtain a new and unbiased census of UFDGs in the MW halo with Gaia data we will adapt, improve and test the use of the Wavelet Transform techniques for the UFDG detections [1].


[1] T. Antoja et al. (2016), Detection of satellite remnants in the Galactic Halo with Gaia-III. Detection limits for ultrafaint dwarf galaxies, MNRAS 453, 541. (

contact e-mail:

Title: Inhomogeneous stellar wind accretion and jet formation in high-energy emitting binaries

Advisor: Valentí Bosch

Abstract:: It is thought that gravitational capture by a compact object of wind from a companion star is not an efficient process to form an accretion disc, as there is not enough angular momentum in the accreted material. The presence of an accretion disc has been considered necessary to form jets, which are emitters of non-thermal emission. On the other hand, as massive star winds are known to be inhomogeneous, the inhomogeneities may have enough angular momentum with respect to the compact object to form small, relatively short lived discs. These discs could be able to launch jets, and fuel the production of high-energy radiation.


 The Effect of Porosity on X-Ray Emission-Line Profiles from Hot-Star Winds Owocki, S. P., Cohen, D. H. 2006, ApJ, 648, 565O

 Direct wind accretion and jet launch in binary systems Barkov, M., Khangulyan, D., 2012, MNRAS, 421, 1351

contact e-mail: 

Title: Accretion processes in the first Be/BH binary system

Advisor: Marc Ribó.

Abstract:: The study of accretion and its coupling with ejection processes around black holes in binary systems has improved considerably during the last two decades, providing constraints for theoretical models. MWC 656 has recently been discovered as the first binary system containing a black hole (BH) orbiting a Be star. While several BH have been discovered orbiting low-mass stars, MWC 656 is just the second confirmed case in high-mass star after Cygnus X-1. Optical photometry of MWC 656 shows a maximum close to periastron, expected in an accretion scenario. However, other diagnostics indicate the presence of a hot spot produced when the accretion stream impacts the accretion disk. To unveil if the increase in the optical flux is solely due to an increase in the accretion rate (at constant temperature) or if it is due to the presence of the hot spot (varying temperature) we are conducting multi-filter optical photometry of MWC 656 with the Telescopi Joan Oró (TJO, Observatori Astronòmic del Montsec). The goal of this project is to reduce and analyze a data set of BVRI photometry of MWC 656 obtained along 60 nights during summer/fall 2015 with the TJO and to interpret the obtained results in the context of accretion physics in binary systems. This will shed light on the accretion processes in the only Be/BH binary known.

Requirements: programming skills in Fortran and Python.


Casares, Negueruela, Ribó, et al. 2014, Nature, 505, 378

Paredes-Fortuny, Ribó, et al. 2015, 575, L6

Dubus 2013, A&ARv, 21, 64 

Contact e-mail:

Title: Reconstruction of directional distributions of solar energetic particles in the inner heliosphere

Advisor: Neus Agueda

Abstract:: Solar eruptions release huge amounts of solar energetic particle (SEP) radiation in the heliosphere that can damage satellites and impair terrestrial aviation. Our understanding of SEP events is mostly based on remote electromagnetic observations of the Sun (in white light, X-rays, and radio) and detailed in-situ observations of their directional distributions, energy spectra, composition and time evolution. The goal of this project will be to assess how well the EPD experiment to fly on board the upcoming Solar Orbiter mission will be able to map particle directional distributions. Solar Orbiter will travel to the innermost regions of our solar system to better understand and predict the Sun. Being closer to the Sun will be a challenge from a technological point of view, and it will modify the properties of the observed SEP distributions. Will four fields of view be enough to resolve the anisotropic particle distributions expected close to the Sun?

Requirements: programming skills in IDL or Fortran


Contact e-mail:

Title: Metal line absorption systems as probes to galaxies in formation

Advisor: Jordi Miralda

Abstract: Numerous absorption systems that are detected in spectra from the Sloan Digital Sky Survey correspond to gas in high-redshift halos in which galaxies are forming, and show absorption lines of many ionized elements that can be used to study the physical state. We would like to measure correlations among these lines and their positions relative to quasars, which can be used to measure the effect of quasar ionizing radiation and establish the physical conditions of the gas.

Contact e-mail:

Title: The effect of radio-mode heating on galaxy evolution

Advisor: Alberto Manrique


The most important feedback from AGNs is the mechanical reheating of the gas inside galaxies (Springel 2005). A second AGN feedback is the so-called radio-mode heating of the hot intrahalo gas (Croton et al. 2006) taking place when the MBH lies within a naked spheroid directly fed by cooling flows with small angular momentum. In this case, a small fraction of the bolometric AGN luminosity is transferred mechanically to the hot gas in the halo through relativistic jets (Croton et al. 2006, Allen et al. 2006), which slows down the cooling of the hot gas there, possibly even halting it. Such reheating is completely determined by the amount of cold gas feeding the MBH and the AGN radiation.

The aim of the work is to implement a self-consistent computation of the radio-mode heating in the semianalytic model AMIGA (that follows the formation and coupled evolution of galaxies and the inter-galactic medium) to reliably assess the strength of this AGN feedback on galaxy evolution.


Allen, S. W., Dunn, R. J. H., Fabian, A. C., Taylor, G. B., & Reynolds, C. S. 2006, MNRAS, 372, 21

Croton, D. J., Springel, V., White, S. D. M., et al. 2006, MNRAS, 365, 11

Springel, V. 2005, MNRAS, 364, 1105


Title: Find a virialized halo finder

Advisor: Josep Maria Solanes

Abstract:: Galaxies within galaxy groups and clusters nowadays can be routinely identified in numerical simulations using methods based on identifying locally overdensities. Most popular halo finders include a final step in which all substructure candidates are subjected to a gravitational unbinding procedure where only the self-bound part is retained (see, e.g. [1]). However, distinguishing the central truly virialized galactic halo from the extended infall region surrounding it is usually a notoriously difficult task.

One possibility, used e.g. by [2], is to measure the spherical mass density profile of galaxies, and determine the radius at which the profile begins to level off and be dominated by the background density. Among the disadvantages of this procedure are that galaxy halos usually are not intrinsically spherical, and that the mass profiles of neighboring galaxies may overlap one another, complicating the calculations.

Another possibility is to attempt a dynamical distinction to separate the two components in velocity space [3]. This works well for central cDs of massive galaxy clusters, but is less robust when the velocity dispersions of the two components are similar and therefore difficult to discriminate. The source of this unsolved problem can be traced to the arbitrariness that accompanies the calculation of the binding energy of a particle, because the potential energy of particles depends on the total mass and shape of the source region adopted [4]. This means that there is no way to tell a priori which mass contributes to the galaxy's virialized core and which does not.

Without a doubt this Master project is not for the faint hearted. If you consider yourself a person with great brains and you like to solve complex problems this challenge suits you: would you be able to find a technique that unambiguously separates the relaxed cores of galaxies from their secondary infall region?


[1] Maciejewski, et al. 2009, MNRAS, 396, 1329. Link

[2] Rudick, et al. 2011, ApJ, 732, 48

[3] Dolag, K., Murante, G., & Borgani, S. 2010, MNRAS, 405, 1544

[4] Han, et al. 2012, MNRAS, 427, 2437


Title: Microlensing events observed by Montsec Observatory in Gaia Science Alerts programme

Tutor: Carme Jordi i Nebot

Advisor: Josep Manel Carrasco Martínez


Some of the Gaia satellite (ESA, 2013) photometric alerts (sources suddenly increasing its flux to be followed up from ground telescopes) are due to gravitational microlensing events. Gravitational microlensing are produced when two stellar type objects are aligned in the line of sight magnifying the light of the background object. This can be used to study in better conditions both the background and the foreground objects using its temporally magnified fluxes. Microlensing is a powerful tool in finding invisible objects, including planets on Earth-like orbits, massive black holes or even Tidal Disruption Events (TDE):

1. Microlensing planets in Gaia

In order to detect a potential planet around the lens an intense follow-up observational campaign is necessary. In this project we propose to observe selected Gaia microlensing events with Observatory Montsec in order to detect a tiny deviation due to planet.

2. Stellar mass black holes from Gaia

In order to recognise if the lens was a black hole it is necessary to obtain good coverage of the light curve to derive the parameters of the lens and to constrain potential black hole mass and distance. The project will require involvement in the observations of microlensing events with Observatory Montsec, data reductions and studies of individual events.

3. Hunt for Tidal Disruption Events

Supermassive black holes in centres of galaxies are often waken up by a star passing a bit too near. The accretion of the star produces a luminous blue flare, called Tidal Disruption Event. Gaia and other transient surveys detect candidates for central transients, however their multi-colour observations from the ground and space (Swift) are required to prove the transient is not just a supernova. In this project selected transients will be observed in detail from Observatory Montsec in order to find new examples of Tidal Disruption Events and measure masses of black holes in nuclei of galaxies.

Contact e-mail:

Title: Stellar parameter determination using JPLUS photometry

Tutor: Carme Jordi i Nebot

Advisor: Josep Manel Carrasco Martínez


The Javalambre-Photometric Local Universe Survey, J-PLUS (, is defined to observe 8500 deg2 of the sky visible from the Javalambre Observatory (Teruel, Spain) with the panoramic camera T80Cam at the JAST/T80 telescope, using a set of 12 broad, intermediate and narrow band optical filters. The Project is particularly designed to carry out the photometric calibration of J-PAS ( For this reason, some J-PLUS filters are located at key stellar spectral features that allow to retrieve very accurate spectral energy distributions for more than 5 millions of stars in our Galaxy.

Some of the photometric passbands used in J-PLUS programme were originally proposed by the UB team while designing a photometric system for Gaia Mission in its early instrument design phase, and they were selected due to its ability to disentangle the effect of the astrophysical parameters (effective temperature, surface gravity, metallicity, alpha elements abundances, ...) of the stars in the spectral energy distribution of the stars.

This work aims to define a methodology and code an algorithm able to be used for stellar classification/parameterisation in J-PLUS programme. This methodology can be based on the original studies developed for Gaia passbands using colour-colour diagrams and should be able to do the parameterisation for all stars observed in an automatic and not-supervised way.

Contact e-mail:

Title: Open clusters as seen by Gaia

Advisor: Carme Jordi /Xavier Luri

Abstract:: Gaia is an space astrometric mission by European Space Agency with launch in November 2013. It is a full sky scanning satellite aiming to measure positions, proper motions and parallaxes for a billion stars in the Milky Way with an unprecedented precision of 15 microarcseconds at magnitude 15. In addition, Gaia will obtain low and high resolution spectra of the observed stars. All this information together will allow to unveil the history of formation and evolution of our Galaxy.

The aim of this master thesis is to analyse the astrometric, photometric and spectroscopic capabilities of Gaia to study open clusters using the simulated Gaia observations produced by the Gaia Object Generator (GOG) simulator developed by the UB team.

Why open clusters? Stellar clusters are crucial in the study of a variety of topics including the star formation process, stellar structure and evolution, dynamical interaction among stars, or the assembly and evolution of galaxies. In fact, most stars, including the Sun, are formed in stellar clusters although most of them are dissolved in the first few Myr. Globular clusters, formed by old and metal poor populations are used to trace the first stages of the Galaxy formation. Open clusters, which cover larger ranges of ages and metallicities, are located in the Galactic disk. Therefore, they are key to investigate its formation and evolution.

The concrete goals are:

  • to simulate Gaia observations of a set of clusters of different richness (i.e. different masses), different ages, different locations in the Milky Way disk in combination with the foreground and background stellar population
  • to analyze the HR diagrams, proper-motion vector point diagrams, etc with their corresponding error bars, that can be used to discuss the capabilities of Gaia for those clusters


About Gaia mission: Perryman et al 2001, A&A 369, 339

About Gaia performances:

About Gaia Universe Model simulation: Robin et al 2012, A&A 543, A100


Title: Outskirts of open clusters

Advisors: Lola Balaguer, Carme Jordi

Abstract:: Stellar clusters are crucial in the study of a variety of topics including the star formation process, stellar structure and evolution, dynamical interaction among stars, or the assembly and evolution of galaxies. In fact, most stars, including the Sun, are formed in stellar clusters although most of them are dissolved in the first few Myr. Open clusters are usually distinguished by their higher stellar density in contrast with the sourrounding sky. Most often, their study is restricted either to the brightest stars and/or to the their central part, the nucleus. Although this may be enough for the determination of distance and age, it does not suffice to derive the present-day mass function, the total mass, the extension or the internal structure and mass segregation.

High quality proper motions of a selection of 40 open clusters have been acquired in a project conducted with the meridian circles of San Fernando at El Leoncito (Argentina) and La Palma. The area covered by the observations is few times larger than the quoted radius of the clusters in the literature, which will let us study their coronas with unprecedented accuracy. For several of those clusters, our team have Stroemgren photometry obtained with the Wide Field Camera at INT.

In this framework, the master thesis projects aims to:

  • select the most promising 2-4 clusters out of the total list of 40 observed, taking into account distance, age, brightness, precision of astrometry and photometry, existing data in the literature, availability of Stroemgren photometry, availability of data from the Gaia-ESO survey, and so on
  • separate stars from the cluster and from the field, using as many information available as possible (proper motions, colour-magnitude diagrams, radial velocities)
  • establish the extension of the selected clusters, their present-day mass function and the degree of mass segregation; and discuss the relationship with age and position in the disk


Balaguer-Núñez, L.; Jordi, C.; Muiños, J. L.; Galadí-Enríquez, D.; Masana, E. Studies on the corona of open clusters. Highlights of Spanish Astrophysics VII, Proceedings of the X Scientific Meeting of the Spanish Astronomical Society (SEA), held in Valencia, July 9 - 13, 2012. Eds.: J.C. Guirado, L.M. Lara, V. Quilis, and J. Gorgas., pp.644-644 (05/2013) ADS link

Balaguer Núñez, L.; Jordi, C.; Muiños, J. L.; Galadí-Enríquez, D.; Masana, E. New Membership Study on the Corona of the Open Cluster M 67. Stellar Clusters & Associations: A RIA Workshop on Gaia. Proceedings. Granada, Spain, May 23 - 27, 2011. Edited by: Alfaro Navarro, E. J.; Gallego Calvente, A. T.; Zapatero Osorio, M. R., pp.375-376 (00/2011). ADS link

Moyano Loyola, Guido R. I.; Hurley, Jarrod R. Stars on the run: escaping from stellar clusters. Monthly Notices of the Royal Astronomical Society, Volume 434, Issue 3, p.2509-2528 (09/2013)


Title: Optimization of the Besançon Galaxy model code

Advisors: C. Figueras, X. Luri

Abstract:: The Besançon Galaxy Model ( is the best stellar population synthesis model of our galaxy currently available. It has been originally developed by A. Robin and collaborators at the Besançon Observatory, but its latest upgrade and extension has been done in collaboration with our team at the ICCUB.

This model is implemented in Fortran and is the heritage of more than 20 years of development. We plan now to update the code in order to optimize it and prepare its future evolution.

The proposed work is the first step in this process: carry out a full review of the Fortran code in order to

  • Review and update the set of input parameters and ingredients definig the galaxy model, and document them
  • Streamline and simplify the code to prepare it for future applications: IMF and SFH testing
  • Upgrade the code to be able to apply the new philosophy for star generation (Czekaj, 2012 PhD) to the thick disk, the halo and the bulge population

With this work the student will have an opportunity to learn how a galaxy model is built and will obtain first-hand experience on its actual implementation.


A. C. Robin, C. Reylé, S. Derrière and S. Picaud. A synthetic view on structure and evolution of the Milky Way, 2003, Astron. Astrophys., 409:523

Contact e-mail: