Data Science

Computational Cosmology

aaorsi at gmail dot com


I am currently a Principal Scientist at PlantTech Research Institute, a New Zealand Regional Research Institute that develops AI and machine learning for the NZ horticulture industry. Before joining PlantTech I did Computational Astrophysics in Spain, the UK and Chile. This page describes my activities in Astrophysics.

During 2015-2019 I was a Staff Researcher at Centro de Estudios de Fisica del Cosmos de Aragon (CEFCA) in the city of Teruel, Spain. I obtained a PhD in 2010 from Durham University, UK, under the supervision of Prof. Cedric G. Lacey and Prof. Carlton M. Baugh. My thesis title is "The Nature of Emission-Line galaxies in Hierarchical Cosmologies", and it's available here.

I was a coordinator of the Galaxy Evolution Science Working Group of the J-PAS survey. This survey aims to map ~8500 square degrees survey of the northern sky with 56 optical narrowband filters. J-PAS will be carried out at the OAJ observatory operated by CEFCA.

I was also a member of the Survey Science Committee of the J-PLUS project. This ongoing survey is the precursor of J-PAS, and is mapping thousands of square degrees with 7 narrowband filters and 5 broad bands covering the full optical spectrum.

I was also a member of the Euclid collaboration, ESA's Cosmic Vision space mission to map the geometry of the Universe, and of ATLAS Probe, a concept for a NASA probe-class mission to map the 3D distribution of sources up to very high redshifts.

I organised two meetings to bring together the astronomical community that works on emission-line galaxies and foster inter-disciplinary (i.e. observational vs. theoretical) collaborations. The first one was an international workshop called Understanding Emission-line galaxies for the next generation of cosmological surveys, and it took place in Teruel during September 2018. The second one was organised for the astronomical community in Chile in November 2018, and it was called Lyman-alpha and friends.

Research highlights and more

Back in September 2018 I organised an international workshop called "Understanding ELGs for the next generation of cosmological surveys". Check out the presentations here

Galaxy formation

A semi-analytical model of galaxy formation predicts how radio galaxies (pink) are surrounded by star-forming galaxies (blue), tracing the underlying dark matter distribution (gray)

Monte Carlo radiative transfer

The complicated escape of Lyman-alpha photons from a neutral gas cloud is simulated in a Monte Carlo code.

Structure formation in the Universe

The evolution of Dark matter tracked in an N-body simulation throughout cosmic time

AMNH Exhibit

A 2009 visual exhibit for the American Museum of Natural History featuring my research on galaxies at the cosmic dawn (i.e. the first galaxies in the Universe).

Galaxies in the cosmic web

A galaxy formation model predicting the spatial distribution of distant galaxies to be discovered by NASA's concept mission ATLAS Probe.

TV interview

In 2013 a meteorite crashed in Russia. I was interviewed for several radio, TV and online media during that time to discuss this event. Here's one of those interviews for Chilean TV discussing meteorites and how to protect from them.

Galaxy formation and Cosmology

This is a recent paper describing the impact of galaxy formation on cosmological analysis of clustering measurements. Check my Publications tab for a full list of publications.


25th September, 2018

ELG Workshop presentations

The Workshop "Understanding Emission-line galaxies for the next generation of cosmological surveys" took place during September 3-6 in Teruel, Spain. Around 70 people came from all over the world to discuss ELGs from current and future observational projects, and also from theoretical models and cosmological forecasts. Check out the presentations and programme of the meeting in this link

7th July, 2018

Lyman-alpha emitters in a cosmological volume I

Our student Siddhartha has submitted his first paper about LAEs, and the preprint is available here

In this work we describe how to incorporate Ly-alpha radiative transfer effects in a cosmological simulation to predict the Ly-alpha luminosity of star-forming galaxies. Our method can be easily implemented in large cosmological simulations, allowing to predict how LAEs probe the underlying dark matter distribution. We find that radiative transfer effects are crucial to interpret the properties of this galaxy population, and thus to obtain unbiased measurements from future large datasets of LAEs at high redshifts.

10th April, 2018

The J-PLUS presentation paper is out!

Check out the preprint of J-PLUS Paper 0, submitted to A&A,. The paper features a description of the instrumental and survey designs, and a brief description of many science cases being actively exploited. As written in the abstract,

"J-PLUS has the potential to contribute to a wide range of fields in Astrophysics, both in the nearby universe (Milky Way, 2D IFU-like studies, stellar populations of nearby and moderate redshift galaxies, clusters of galaxies) and at high redshifts (ELGs at z~ 0.77, 2.2 and 4.4, QSOs, etc)"

7th February, 2018

Workshop announcement

We are very happy to announce a workshop on "Understanding Emission-line galaxies for the next generation of cosmological surveys" to be held in Teruel, Spain, 3-6 of September 2018.

The main goal of this workshop is to bring together and foster collaborations between people working in

i) Current and future cosmological surveys targeting ELGs;

ii) Galaxy formation models and mock catalogues of ELGs, and

iii) Detailed studies of ELGs in the optical + NIR at high redshift.

Detailed information can be found here:…/understanding_emission_line_galaxies

The deadline for registration is the 15th of June.