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David Sobral supervises 4 postgraduate research students. If these students have produced research profiles, these are listed below:

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Dr David Sobral FHEA FRAS

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David Sobral

Physics Building

LA1 4YB

Lancaster

Tel: +44 1524 593529

Office Hours:

Friday, 10-11am + e-mail and open door policy

Research overview

I conduct a wide range of observations at various wavelengths and use the best telescopes in the world (and in space) in order to understand how galaxies like our own Milky-Way formed and evolved from the primitive Universe till today. See my research webpage. I discover and study some of the most distant, early galaxies and anyone can try to find distant galaxies with the same data that we use! Watch some of the videos explaining the research I do in my XGAL youtube channelMost of my research is done by conducting and exploring some of the largest/widest narrow-band surveys ever done, particularly for sources with emission lines which result from either very hot, young stars, or super-massive black holes. Due to the uniform and self-consistent selection, galaxies found with the narrow-band technique across cosmic time are ideal to understand how they have changed accross cosmic time, but also to conduct detailed follow-up studies that can really unveil the physics and nature of distant sources. See my Google Scholar page or my ADS list of all my publications and my CV here.


I provide a range of opportunities for students to experience and share state-of-the-art research, particularly by running the XGAL internships: https://xgalweb.wordpress.com. Since 2016, I have been able to take 3-5 students/year to observe in professional telescopes in La Palma: know more about it here. I also run the Astrophysics group project (PHYS369) in which students report on their research experiences and get their results published in our journal Notices of Lancaster University Astrophysics, NLUAstro (Freely available).

 


New for 2020: check out my XGAL youtube channel with Astronomy talk shows about the gas giants, dark matter, dark energy, galaxies, near and very far, galaxy clusters, super-massive black holes, super-active galaxies, galaxy archeology, globular clusters and how it was to discover the CR7 and other galaxies.

PhD supervision


Exploring Lyman-alpha emitters in the far-infrared with ALMA


Narrowband and 3D spectroscopic surveys have identified thousands of Lyman-alpha emitting galaxies (LAEs) in the distant, early Universe. Lyman-alpha, emitted at rest-frame 1216A, is the strongest emission-line resulting from ionising photons from either young massive stars or super-massive black holes, allowing LAEs to be detected at the furthest cosmological distances. However, interpreting their Lyman-alpha emission is challenging since it can originate from neutral Hydrogen in the inter-, circum- and intergalactic medium, and Lyman-alpha photons can also be self-absorpbed and are easily attenuated by dust. LAEs are typically primeval galaxies that are blue and with young, highly ionising stellar populations and some host active super-massive black holes. Analyses to date suggest that they are dust poor, but there have been few direct observational studies of dust in LAEs because the necessary far-infrared data haven’t been available. Now, with the commissioning of the Atacama Large (sub)Millimeter Array (ALMA) far-infrared observations of large samples of LAEs are available. This project will use ALMA to measure the dust in and around LAEs to understand the impact of dust on our understanding of LAEs and the role of dust and dust-forming processes in the formation and evolution of these primeval galaxies. This project will be jointly supervised by Dr David Sobral and Dr Julie Wardlow; please contact them for further information. This PhD project represents just one component of the research performed by the wider Astrophysics group at Lancaster University. Our PhD projects are offered on a competitive basis and are subject to availability of funding. For more general information about PhD study in Physics at Lancaster please contact our postgraduate admissions staff at py-pgadmiss@lancaster.ac.uk. You can also apply on our PhD page stating the title of the project and the name of the supervisor.

1216: Unlocking the secrets and physics of primeval galaxies with Lyman-alpha

Thousands of Lyman-alpha emitters (LAEs) have been found in the distant, early Universe through narrow-band and 3D spectroscopy surveys, including many luminous ones discovered by us at Lancaster (see e.g. https://youtu.be/tKb2osj3nkU). Lyman-alpha, emitted in the UV with a rest-frame of 1216A, is the strongest emission-line resulting from ionising photons from either young massive stars or super-massive black holes, allowing us to detect it to the highest cosmological distances. However, its sensitivity to neutral Hydrogen in the inter-, circum- and intergalactic medium makes it a challenging puzzle. Fortunately, the last few years have brought numerous discoveries and the development of several empirical and theoretical tools (e.g. Sobral and Matthee 2019). Recent results reveal that LAEs are primeval galaxies which are typically dust poor, blue and with young, highly ionising stellar populations, along with with some hosting active super-massive black holes. These properties make LAEs fantastic targets to study and understand the physics of primeval, early galaxies, along with their role in likely driving cosmic re-ionisation. This project will allow to explore and further establish Lyman-alpha as a means to identify distant galaxies but even more so to use it as an extremely powerful physics tool and to solve cosmic re-ionisation with direct observables (https://youtu.be/RlOcgsrot2c?t=2550). The project will allow the student to develop and use empirical and analytical tools, along with exploring deep spectra and deep narrow-band data taken at the VLT, together with proposing and exploring follow-up observations of distant LAEs. Results from JWST will allow to further test and advance our understanding of these distant primeval galaxies towards the end of the project.


Towards the direct discovery of first generation stars in our backyard


This project will allow the student to take part in a recent hunt for the most metal poor stars up to the outskirts of the halo of our own Milky Way. Finding such extreme stars born in the early Universe but still shinning today allow us to unveil their nature. Most interestingly, very metal-poor stars allow us to become “stellar archeologists” and understand the properties of the very first generation of stars that gave rise to the traces of heavy elements that led to their creation. Potentially, we may be able to find first generation stars which may have survived until today. Finding and studying first-generation stars that may still be shinning in the halo of the Milky Way will be a major breakthrough in Astrophysics, not only to provide new tests and constraints to state-of-the-art models, but also because we will be able to study the generation of stars that literally invented chemistry and that is directly linked with our cosmic origins. The project will involve modelling of several observed and model stars to mimic observations and confront predictions with brand new data taken by us. Data have been taken using the INT telescope in La Palma and the CFHT telescope in Hawaii with narrow-band filters that capture a strong Calcium absorption feature in stars which becomes weaker for the most metal poor stars. Our Lancaster-led data-set is the deepest ever done with this filter in the ultra-violet, and allows us to see metal poor stars individually up to the outskirts of the halo of our Milky Way.

Current Teaching

  • PHYS111: Functions and Differentiation (2016--)
  • PHYS263: Astronomy (2016--)
  • PHYS264: Astrophysics I (2017-2018)
  • PHYS369: Observational Astrophysics group project (2018--)

Research Interests

Galaxy formation and evolution; Emission-line galaxies; High-redshift galaxies; Re-ionisation of the Universe; The star formation history of the Universe; Hot/massive stars; Super-massive black holes

Web Links

Research Grants

  • Observational Astrophysics PATT grant (2018-2020)
  • Observational Astrophysics PATT grant (2016-2018)
  • NWO VENI grant (2012-2016): "From the First Galaxies to the Peak of the Star Formation History"
  • FCT Starting grant (2013-2015)

PhD Supervisions Completed

  • Dr. Andra Stroe (2015, Leiden University, co-supervision). Currently: CfA Clay fellowship at the Harvard-Smithsonian (previously: ESO fellow), U.S.A.
  • Dr. Behnam Darvish (2015, University of California Riverside, co-supervision). Currently a postdoctoral fellow at the California Institute of Technology (Caltech), U.S.A.
  • Dr. Jorryt Matthee (2018, MERAC prize for best thesis in Observational Astrophysics & IAU prize). Currently: Zwicky Prize Fellow at ETH Zurich, Switzerland.
  • Dr. Ali Khostovan (2018). Currently: NASA NPP Fellow at NASA Goddard, U.S.A.
  • Dr. Ana Paulino-Afonso (2019). Currently: Postdoctoral fellow at Lisbon University.
  • Dr. João Calhau (2020).
  • Dr. Sérgio Santos (2020).

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