Hello World!

I am a Postdoctoral Researcher in the Extragalctic Astronomy research group at the Astronomical Observatory of Rome (INAF-OAR), Italy. The main focus of my research is to study the evolution of the physical properties of very distant galaxies using state-of-the-art telescopes around the world.

I am currently studying high-redshift (distant) galaxies that are in the very early stages of their evolution. To do this, I use the VANDELS dataset, which is a survey of small patches of the sky using the Very Large Telescope (VLT) in Chile. The VANDELS survey targeted thousands of galaxies to obtain very high quality spectra that enables studying their properties in incredible detail.

I am also interested in studying distant radio galaxies (massive galaxies that appear very bright at radio wavelengths) and using them to study the evolution of both galaxies and the large-scale structure of the universe. At redshifts (z) of 6 and above, into the epoch of reionisation (EoR), a bright radio galaxy can be used as a background to search for the elusive 21-cm absorption signal from the neutral hydrogen that pervaded the universe at that time. Constraining when and how the universe made a phase transition from neutral to completely ionised is one of the most exciting challenges in cosmology today and radio galaxies at z > 6 may hold some clues!

On this page you can find more information about my research interests, what I like to do in my free time, a short CV and my contact information.


Physical properties of distant galaxies in VANDELS

We now know a fair amount about our own Milky Way galaxy, and several other galaxies that are relatively close to the Milky Way. However, there are still several open questions about galaxies that are further away from us. Studying distant galaxies also helps us understand how galaxies like our Milky Way formed, and what were the physical processes that shaped its evolution. Thanks to the deep VANDELS survey, we can now study in great detail the physical properties of galaxies almost 13 billion light years away from us (z ~ 6), when the universe was a tiny fraction of its current age.
Click on the image below to find out more about the VANDELS survey:

Discovery of the most distant radio galaxy to date

In June 2018, my research team discovered the most distant radio galaxy observed to date, named TGSS J1530+1049, at a distance of 12.7 billion light years away (redshift = 5.72)! In comparison, the age of the Universe is 13.6 billion years. Therefore, this is a galaxy that was formed within the first 7% of the Universe's lifetime! This discovery broke the distance record for a radio galaxy after almost 20 years. Radio galaxies are some of the most massive galaxies in the Universe and harbour a supermassive black hole in their centres that is actively eating up the gas and dust that surrounds it. Discovering such an object at such a large distance from us poses some interesting challenges about how and when the seeds of this galaxy and the supermassive black hole were sown, and how they evolved to be so massive in such a short period of time after the Big Bang.
The paper reporting this discovery has now been published in the Monthly Notices of the Royal Astronomical Society and can be found here:
Discovery of a radio galaxy at z = 5.72, 2018

In the media:
Astronomy Now: Most distant radio galaxy, host to a voracious black hole, is found
Phys.org: The most distant radio galaxy discovered
Astronomie.nl: Astronomen ontdekken verst verwijderde radiostelsel ooit (Astronomers discover the most distant radio galaxy ever)
BBC Brasil: Radiogaláxia mais distante da Terra é descoberta com participação de brasileiro - e dá mais pistas sobre o Big Bang (Most distant radio galaxy is discovered with Brazilian participation - and gives more clues about the Big Bang)
Media INAF: Scoperta la radiogalassia più lontana (The most distant radio galaxy discovered)

High-redshift extreme spectrum project (HiZESP)

We have started a large campaign to hunt for distant radio galaxies by taking advantage of the new all-sky surveys at low radio frequencies using telescopes such as the Giant Metrewave Radio Telescope (GMRT) in India, the Very Large Array (VLA) in USA and the Low Frequency Array (LOFAR) in the Netherlands and all of Europe. Early results from this project can be found here:
A search for faint high-redshift radio galaxy candidates at 150 MHz, 2018

In addition to studying these sources at radio wavelengths, it is essential to also observe them at optical and infrared wavelengths. As part of this project, we have been awarded observing time on telescopes all over the world to a) obtain spectra and determine redshifts of candidate high-redshift radio galaxies and b) observe our targets at near-infrared wavelengths to study the underlying stellar populations.

The telescopes being used for this project include the Hobby-Eberly Telescope (HET), Gemini North, William Herschel Telescope (WHT) and the Large Binocular Telescope (LBT) (Saxena et al. in preparation).

Modelling luminosities and sizes of radio sources across cosmic time

One of the first projects of my PhD was to build a model capable of tracking the evolution of radio galaxies from first principles, and predicting the luminosity and size distribution of radio sources at any given epoch. This model included recipes for a host of physical phenomenon and the results can be found here:
Modelling the luminosities and sizes of radio sources: radio luminosity function at z = 6, 2017

Other interests

In addition to astronomy, I have had the pleasure to be a part of various activities in and around town. Here you can find some of the things that I care about!

Leiden International Short Film Experience (LISFE)

The 10th edition of LISFE at the artsy cinema, Het Kijkhuis, was a wrap this spring and it was a huge success! LISFE has grown from a day or two of screening short-films in a student centre in Leiden to one of the biggest national level short-film festivals in The Netherlands! LISFE received over 800 films from 70 countries for the 2018 edition and we are looking forward to expand and grow again this year. Click on the image on the left to know more!

Leiden Football Factory

After achieving the second place in the lower divisions of the Dutch Amateur Leauge, the new football (soccer) season starts again this autumn and we will be back to challenge for the division title! Click on the image on the left to follow updates (hopefully you click only when we've won a few games)!

Astronomy on Tap Leiden

Astronomy on Tap is a unique concept that combines an astronomy public talk with the joy of drinking beer in the local pub! I gave a public talk about distant radio galaxies and their supermassive black holes on 30 July, 2018! Join us at AoT at Grand Cafe de Burcht on the last Monday of every month starting at 8pm to learn more about astronomy while chugging pints with your mates.

Public Engagement = Fun!

Here at Leiden Observatory, we take public engagement activities very seriously and believe it to be an integral part of astronomy research. I am involved with our outreach wing called Universe Awareness (Unawe), founded by one of my co-supervisors George Miley. One of my personal best experiences was giving a talk about my research to 5th graders at American School The Hague. Follow the link by clicking on the image to find out more!

Short CV

Here you can find a short version of my CV:

Research positions

Postdoctoral Researcher, INAF-OA Roma, Italy, Feb 2019 -
Postdoctoral Researcher, Leiden Observatory, The Netherlands, Nov 2018 - Jan 2019


PhD Astronomy and Astrophysics, Leiden Observatory, The Netherlands, 2014 - 2018
MSc Astrophysics, University College London, UK, 2014


First author
  • Discovery of a radio galaxy at z = 5.72 (2018), Saxena, A. et al., Monthly Notices of the Royal Astronomical Society (MNRAS)
  • A search for faint high-redshift radio galaxy candidates at 150 MHz (2018), Saxena, A. et al., MNRAS
  • Modelling the luminosities and sizes of radio sources: radio luminosity function at z = 6 (2017), Saxena, A.; Röttgering, H. J. A.; Rigby, E. E., MNRAS
Contributing author
  • Optical detection of a GMRT-detected candidate high-redshift radio galaxy with 3.6-m Devasthal optical telescope (2019), Omar, A., Saxena, A., et al., Journal of Astrophysics and Astronomy
  • The LoTSS view of radio AGN in the local Universe. The most massive galaxies are always switched on (2019), Sabater, J. et al. (including Saxena, A.), A&A
  • The LOFAR Two-metre Sky Survey. II. First data release (2019), Shimwell, T. W. et al. (including Saxena, A.), A&A
  • Investigating the unification of LOFAR-detected powerful AGN in the Boötes field (2017), Morabito, Leah K.; Williams, W. L.; Duncan, Kenneth J.; Röttgering, H. J. A.; Miley, George; Saxena, A., et al., MNRAS
  • The WEAVE-LOFAR Survey (2016), Smith, D. et al. (including Saxena A.), Conference proceedings
  • Gender Stereotypes in Science Education Resources: A Visual Content Analysis (2016), Anne H. Kerkhoven, Pedro Russo, Anne M. Land-Zandstra, Aayush Saxena, Frans J. Rodenburg, PLOS-ONE

Successful observing proposals

  • MUSE (VLT), PI, 8 hours
  • XSHOOTER (VLT), PI, 4 hours DDT
  • William Herschel Telescope, PI, 7 dark nights
  • VLA A-configuration, Co-I/contact person, 9+ hours of priority-A time
  • Hobby Eberly Telescope, Co-I, 20+ hours
  • Gemini North, Co-I, 14 hours
  • Large Binocular Telescope, Co-I, 10+ hours

Contact Me

Here is where you can find me both physically and online.

Office Address

Office 464, Oort Building
Niels Bohrweg 2, 2333 CA Leiden
The Netherlands
Leiden Observatory
Leiden University

Email and phone

Email: saxena@strw.leidenuniv.nl
Phone: +31 71 527 8435

If you'd like to get in touch, either to find out more about my research or to complain about anything that you did not like on this website, why not send me an email by clicking on the link above or the little envelope icon on the bottom-right corner of this page?