Research
Astrophysics research
Active Galactic Nuclei, k-means for spectra and a supernova. My contributions from my years as an astrophysicist.
My astrophysics work started in the Canary Islands while I was studying, and continued in Santander at the Institute of Physics of Cantabria, where I did my PhD. During the PhD I was also a visiting research fellow at the Brera Observatory in Milan and the National Observatory of Athens.
The full list of papers and contributions is on NASA ADS.
Active Galactic Nuclei
During the 18th and 19th centuries it was not clear whether the “nebulae” seen in the sky were part of our galaxy or “island universes” made of stars (Kant 1755). The discovery in 1924 of a Cepheid variable star in M31 (Hubble 1929), whose properties reveal its distance, showed that some of them were galaxies like the Milky Way. Spectroscopy soon revealed that some galaxies have emission lines of highly ionised elements in their nuclei (Seyfert 1943) that stars alone cannot explain. In some of them this non-stellar light completely outshines the galaxy. These are Active Galactic Nuclei (AGN).
Today we know this emission comes from supermassive black holes of 106–109 solar masses at the centres of galaxies. Material falling into their gravitational well releases energy through accretion, which powers the electromagnetic emission.
I studied the relation (or lack of it) between optical extinction, X-ray absorption and the classification of AGN.
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Extinction and AGN over host galaxy contrast effects on the optical spectroscopic classification of AGN
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A multifrequency view of Active Galactic Nuclei
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AGNs with discordant optical and X-ray classification are not a physical family: diverse origin in two AGNs
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Searching for luminous absorbed sources in the WISE AGN catalogue
K-means clustering in astrophysics
My first experience with machine learning was my Master’s thesis, supervised by Jorge Sánchez Almeida at the Instituto de Astrofísica de Canarias. I applied k-means to galaxy spectra using a modified, single-pass version of the algorithm that updates cluster centroids on the fly. Later I collaborated on the first steps of a study applying k-means to stars in the APOGEE survey.
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Machine learning in APOGEE. Unsupervised spectral classification with K-means
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A fast version of the k-means classification algorithm for astronomical applications
Supernova classification
At the NEON Observing School 2015 in Asiago (Italy), I took part in an observing campaign where we classified a supernova six days after its peak brightness. The classification was published in The Astronomer’s Telegram.
Talks and posters
I presented my research at conferences and seminars, including two invited seminars. All my talks, including data science and outreach, are on the Speaking page.
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Jul 2019
A thorough investigation on the classification of AGN and its X-ray/optical obscuration
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Jul 2018
Dust-to-gas ratio in a complete sample of type-1 AGN
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Oct 2017
Dust-to-gas ratio in a complete sample of AGN
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Jul 2016
On the relation between X-ray absorption and optical extinction in AGN
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Jun 2016
On the relation between X-ray absorption and optical extinction in AGN
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Mar 2016
Comparison of the optical and X-ray obscuration in AGN
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Sep 2015
Discordant optical and X-ray classification of AGN
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Jun 2015
Discordant optical and X-ray classification of AGN
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Sep 2014
Discordant optical and X-ray classification of AGN
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Jul 2013
Large databases in astronomy: searching for new automatic analysis methods
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Jul 2013
Master's thesis: a fast, single-pass k-means for classifying galaxy spectra
Research stays
- Brera Astronomical Observatory, Milan (Italy), Sep–Oct 2015, supervised by Alessandro Caccianiga.
- National Observatory of Athens (Greece), Sep–Oct 2016, supervised by Ioannis Georgantopoulos.
Teaching and outreach
I taught 35 hours of astronomy lab sessions for the Physics degree at the University of Cantabria:
- Astronomy (in Spanish): 5 hours in 2015–16, and 10 hours each in 2016–17 and 2017–18.
- Astronomy (in English): 5 hours each in 2015–16 and 2016–17.
During my PhD I also prepared and took part in outreach activities organised by the Institute of Physics of Cantabria: public astronomical observations, popular science talks and visits to the institute, among others.
More recently, in August 2026 I gave an outreach talk and helped with the public activities organised by the Luz Cero Astronomical Association in Alustante (Guadalajara) for the total solar eclipse of 12 August 2026, the first total eclipse visible from mainland Spain in over a century. Photos on the Speaking page.