About Me

Hello and Welcome!

I am an astrophysicist, currently working as a post doctoral researcher at Stockholm University. I have mostly studied Lyman alpha line radiation from Hydrogen in the hope of being able to use it as a tool for exploring neutral gas around galaxies and even the Epoch of Reionization



PASSAGE is a large JWST cycle 1 program to obtain parallel wide field slitless spectroscopy with NIRISS.


The Lyman Alpha Reference Sample (LARS) is a long running project aimed at studying Lyα at low redshifts to provide a reference atlas for details about Lyα emission. The observations for the project span many wavelengths between the Lyα to radio 21 cm.

Lyα Halos

We are studying Lyα halos of a sample of 7 low redshift galaxies with the aim of comparing them to high-redshift samples and understanding the production of extended Lyα emission.


On the evolution of the size of Lyman alpha haloes across cosmic time: no change in the circumgalactic gas distribution when probed by line emission

Runnholm, Axel; Hayes, Matthew J.; Lin, Yu-Heng; Melinder, Jens ; Scarlata, Claudia; Adamo, Angela ; Augustin, Ramona; Bik, Arjan ; Blaizot, Jérémy ; Cannon, John M. ; Cantalupo, Sebastiano; Garel, Thibault ; Gronke, Max; Herenz, Edmund C. ; Leclercq, Floriane; Östlin, Göran ; Peroux, Celine; Rasekh, Armin ; Rutkowski, Michael J. ; Verhamme, Anne ; Wisotzki, Lutz 2023

We measure the extents of Lya halos around seven galaxies at redshift ~0.3 and show that they appear to be consistent with high redshift measurements. This is in contrast to other low redshift Lya measurements that have previously appeared to show evolution when compared to high-z LAEs. We speculate that this may be due to systematics in low-z Lya measurements. Also indications are that Halpha is more extended than FUV emission potentially indicating the escape of ionizing radiation to large radii.

Spectral Shapes of the Lyα Emission from Galaxies. I. Blueshifted Emission and Intrinsic Invariance with Redshift

Hayes, Runnholm, Gronke, Scarlata; ApJ 2021

We demonstrate the redshift evolution of the spectral profile of H I Lyα emission from star-forming galaxies focusing especially on blue emission. We use the LASD and stacking analysis to show that the contribution of blue emission from Lyα decreases with redshift in a manner that is consistent with the evolution of the transmission of the intergalactic medium

The Lyman Alpha Spectral Database (LASD)

Runnholm, Gronke, Hayes 2021

We present an online database for Lyman Alpha spectra where users can upload and retrieve spectra as well as get many automatically and homogenously measured quantities from the spectra. The site is available ![here](https://lasd.lyman-alpha.com)

The Lyman Alpha Reference Sample. X. Predicting Lyα Output from Star-forming Galaxies Using Multivariate Regression

Runnholm et al. 2020

We use multivariate regression techniques to tease out the information in many scattered Lyman Alpha correlations and create a predictive model that can explain more than 90% of the variability in our Lyman Alpha observations.

Recent Blog Posts

Learning in Public

By Axel | Jan. 13, 2023, 12:25 p.m.

This will be my first post on this new platform and a format that I am not used to so this will be a