About Me

Welcome to my webpage! I am Martje, a PhD candidate at Leiden Observatory, in the Netherlands. I work on the formation and evolution of galaxies, with a particular interest in the stellar and kinematic properties of distant quiescent galaxies. My advisor is Mariska Kriek.

Outside of astronomy I love playing my guitar (see picture above), cycling, cooking, reading, and doing many different sports!

Education:

Research Interests:
I have broad interests in galaxy formation and evolution. More specifically, I use absorption spectroscopy to unravel the early formation and evolution of distant massive galaxies by studying their (stellar) kinematics and stellar population characteristics. For more details, see my Research section.

Publications:
Here is are ADS links to my first-author or co-author papers.

Research

I currently work on distant quiescent galaxies at cosmic noon using NIR spectroscopy and multi-band photometry. I am broadly interested in the evolution and formation of galaxies, and in my current research I examine the formation histories of distant galaxies using a variety of galaxy properties using absorption spectroscopy. Previously I have studied the earliest stages of galaxy formation from a radio perspective, by studying extremely young radio galaxies. Below is a summary of my major projects.

Unraveling the star-formation histories of distant quiescent using the JWST-SUSPENSE Survey
One of the most remarkable discoveries in extra-galactic astronomy from the past two decades is the existence of a population of quiescent galaxies at z ~ 2 and beyond. Observations have shown that compared to their local counterparts, these distant quiescent galaxies have lower metallicities, and have rotating disc structures similar to star-forming galaxies. These results challenge our models for the formation and subsequent evolution of high-z quiescent galaxies. However, pre-JWST it was extremely challenging to obtain deep, high-resolution spectra for these systems, leading to small sample sizes and a limited understanding of the properties of the population.

In Cycle 1 of JWST, we obtained 16 hours of NIRSPec/MSA data for the JWST-SUSPENSE program, which obtained ultra-deep high-resolution spectra for a sample of 20 quiescent galaxies at z=1-3. Using the full SED fitting code Prospector we obtained detailed star-formation histories (SFHs) and stellar population parameters for these galaxies. From these SFHs we find that distant quiescent galaxies form earlier and over shorter star-formation timescales compared to low redshifts. This is consistent with the idea that distant quiescent galaxies went through their star-formation and quenching phase very rapidly.

This work was published in Slob et al (2024).

Identifying the youngest radio galaxies using LOFAR surveys.
Our understanding of how a radio galaxy evolves remains embarrassingly incomplete. In particular, the first stages of radio galaxy evolution are ill-understood, with far too many small radio galaxy precursors identified relative to the number of giant radio galaxies. These precursors are peaked-spectrum (PS) sources, and can be identified by their compact sizes and turnover in the radio SED. One competing theory for the origin of these PS sources is that these galaxies are not small due to youth but instead because they are confined to small scales by a dense environment ("frustrated").

In this project, we used the International LOFAR telescope, in particular data produced by the LOFAR all-sky survey (LoTSS) and its lowest frequency counterpart (LoLSS), to select the largest sample of these young radio galaxy candidates in the Northern Hemisphere at the time. With this sample we inferred how the luminosity function and number densities of these PS sources evolve over redshift compared to the general radio galaxy population, and found that the PS phase is extremely short compared to the rest of a radio galaxy's lifetime. This showed that the majority of our sample are indeed the young precursors to radio galaxies.

This work was published in Slob et al. (2022).