My Research

1. Research Projects
2. Research Group

Research Projects


I am leading the SUNDIAL EU International Training Network, consisting of 9 nodes across Europe. For more details see here. See also SUNDIAL Science, SUNDIAL Outreach, and the SUNDIAL BLOG.

SUNDIAL is an interdisciplinary network. It contains researchers in astronomy and computer science. In one sentence: I am studying dwarf galaxies using tools developed in SUNDIAL. Here I list my most important contributions in the network.
a) Detection of faint galaxies. I am studying faint, low surface brightness galaxies. To detect them, powerful methods are needed. People mostly have been using SExtractor in various configurations. We have been working on the code MTO (Teeninga et al. 2016), which gives better results (see Haigh et al. 2021) Currently,as followup to SUNDIAL, Michael Wilkinson (Bernoulli Institute, Groningen) and I have a new PhD Student, Mohammad Faezi, who is working on improving MTO, especially for multi-band photometry.
b) Filament detection in astronomy. In SUNDIAL,   A large collaboration in SUNDIAL, led by Peter Tino (Birmingham), with Kerstin Bunte (Bernoulli Institute, Groningen), myself and Rory Smith (KASI, Korea), with PhD students/graduates Marco Canducci, Abolfazl Taghribi, Michele Mastropietro and Bihar Bidaran, has developed a probabilitic modelling pipeline to define filaments in n-dimensional point-clouds (Taghribi et al. 2020, Canducci et al., in preparation). This allows a detailed study of the manifolds, along or perpendicular to it. I have a new PhD student together with Kerstin Bunte, named Petra Awad, who is applying this method to different datasets (cosmic web, simulations and GAIA).
c) Studying dwarf galaxy properties in the Fornax Cluster. See for this the FDS project, just below this section.
d) Studying point-like sources, such as globular clusters and UCDs in the Fornax Cluster. Since the FDS is very deep, it offers possibilities studying sources that point-like or almost point-like from the ground, like globular clusters and UCDs. It is thought that the globular cluster (GC) system reflects the initial situation of the galaxy, at the first formation of its stars (see Harris et al. 2013), and that the number of GCs correlates with the dark halo mass. We have studied the GC system in all dwarf galaxies of the FDS Dwarf Catalogue (Venhola et al. 2018), and are trying to undestand the dark halo masses. This is the work of the master thesis of Lorraine Putman. We have also investigated a population of compact galaxies that has not been studied much, the Ultra Compact Dwarfs. Teymoor Saifollahi has made the first unbiased study of UCDs in the whole Fornax Cluster, finding several UCDs that are not associated with other galaxies.
e) We are studying the detailed stellar populations in dwarf galaxies in the Virgo and Fornax cluster, to obtain star formation histories, abundance ratios and metallicities.
f) Zooniverse citizen science

2. FDS, the Fornax Deep Survey

In recent years it has been shown that galaxies are surrounded by stellar streams that are remnants from past interactions. These streams are invaluable fossils of the interaction history of galaxies with their environment, providing a new and very powerful way of studying galaxy evolution. At the same, wide field imaging camera's have become available, which make it possible to study large parts of the sky, to look for such streams. In this project we perform an ultradeep multiband (u,g,r and i) survey of the Fornax cluster, a nearby galaxy cluster, to study the interaction of galaxies with their environment. The survey is performed using the OmegaCAM camera at the VLT Survey Telescope (VST) , situated at the Paranal observatory of the European Southern Observatory . In depth and design, the FDS survey is similar to the NGVS survey at the CFHT, imaging the much larger and environmentally different Virgo cluster.

The FDS survey, started in 2013, uses the telescopes at the European Southern Observatory and is performed by an international team consisting from researchers in various ESO member states and Chile. The survey is supported by observations using various other instruments and telescopes, amongst which VIRCAM on the VISTA telescope, and VIMOS and MUSE at the VLT.

The research in my group concentrates on the dwarf galaxies in the Fornax cluster. Aku Venhola, who finished his thesis in 2019 in Groningen with a double degree with Oulu, did the full data reduction, and defined the dwarf catalog (FDSDC). Seyda Sen (graduated in 2020) worked on
detailed stellar population modelling of the stellar populations in dwarf galaxies in Fornax. Elaheh Hamraz (graduated in 2020) worked on young populations in dwarfs in the Fornax and Virgo cluster. Sara Eftekhari is analyzing Integral Field Spectroscopy, to study the internal kinematics of dwarfs, and their resolved stellar populations. In the SUNDIAL project there are also other people outside Groningen, who work on the FDSDC: Alan Su (Oulu) is analyzing detailed morphology and nuclear clusters. Shivangee Rathi (Gent) is working on the stellar populations in the very outer parts, from deep colour profiles. Michele Mastropietro has been doing simulations on dwarf galaxies falling into the Fornax Cluster, with a particular emphasis on NGC 1427A.

We are also using FDS in a Citizen's Science project. Since it is difficult to find out whether a galaxy in the FDS field is a dwarf galaxy in the cluster, or a large, massive galaxy behind it, we have tried developing algorithms to do this, but have also built a programme on Zooniverse, where members of the public can answer this question. This programme is called Space Fluff. Space Fluff has been set up by Anna Lanteri, as a SUNDIAL internship student in Groningen, and analyzed by bachelor student Christiaan Seerden. A paper in the refereed literature is in preparation.

Click here for the main results of the FDS up to now.

The most important FDS papers are these:

- Iodice et al. 2016

- Iodice et al. 2017

- Venhola et al. 2017

- Venhola et al. 2018

- Iodice et al. 2019

-Venhola et al. 2019

- Raj et al. 2019

- Spavone et al. 2020

- Cantiello et al. 2020

- Raj et al. 2020

- Su et al. 2021

You can find all FDS-related papers here.

A counterpart for the FDS in the field and in groups is the VEGAS survey, led by my Italian collaborators, in particular, Enrica Iodice.

3. The X-Shooter Spectral Library (XSL) project

The X-Shooter Spectral Library is a collection of 300025000 Å all stellar spectra observed at a resolving power of R = λ/Δλ ~ 10 000 with the medium-resolution spectrograph X-shooter at the Very Large Telescope (VLT). The library enables a new generation of stellar population models to study the stellar populations in galaxies. The library is used to make stellar population models for integrated stellar populations. When making the library, we paid particular attention to cool stars, to optimize the models in the near-infrared.

I am a co-PI of this project. The project is led by Scott Trager, and the other co-PI is Ariane Lancon (Strasbourg). Involved, amongst others, are the ex-Kapteyn postdoc Mariya Lyubenova, Anais Gonneau, ex-Kapteyn postdoc and Matthijs Dries, Kapteyn PhD student, as well as my ex-PhD student Yanping Chen. Also collaborators Alexandre Vazdekis, Jesus Falcon-Barroso, Paola Coelho, Philippe Prugniel and Patricia Sanchez-Blazquez are involved. Most of the work at the moment is done by my PhD student Kristiina Verro.

The project is well underway. We published the following papers. Two data release papers:

2014: Chen et al. 'The X-shooter Spectral Library (XSL). I. DR1: Near-ultraviolet through optical spectra from the first year of the survey'

2020: Gonneau et al.: The X-shooter Spectral Library (XSL): Data Release 2

and 4 papers dealing with aspects of the library:

2016: Gonneau et al.: Carbon stars in the X-shooter Stellar Library

2017: Gonneau et al.: Carbon stars in the X-shooter Stellar Library. II: Comparison with Models

2019: Arentsen et al.: Stellar atmospheric parameters for 764 spectra from the X-shooter Spectral Library

2021: Lancon et al.: A comparison between X-shooter spectra and PHOENIX models across the HR-diagram

We also published several conference proceedings.

4. The KIWICS project and the WEAVE surveys

Deep INT imaging data of nearby galaxy clusters, to obtain photometric properties of their dwarf galaxies, to use dwarf galaxies as probes to study the evolution of galaxies in cluster. The PI's of KIWICS are Alfonso Aguerri (IAC) and myself. We published 2 papers on Ultra Diffuse Galaxies in KIWICS (Mancera Pina et al. 2018, 2019). This work is done in preparation of the WEAVE Cluster survey. In the WEAVE project I am co-leader (with Alfonso Aguerri) of the nearby tear of the WEAVE Cluster survey.

5. The CAVITY project

A study of properties of galaxies in voids. See

6. The BEARDS project

A study of bulge-less galaxies, to understand the how galaxies evolve without bulges. This is a La Palma CTI project.

My Research Group

  • Sara Eftekhari, PhD Student, Working on a project to measure stellar populations, dynamics and black hole masses in dwarf galaxies and UCDs, in collaboration with Steffen Mieske (ESO, Santiago). .2017-
  • Nelvy Choque, PhD Student, working on a project to study the population of dwarf galaxies and UDGs in nearby galaxy clusters, in preparation for the WEAVE-Cluster Survey, 2017-
  • Teymoor Saifollahi , SUNDIAL PhD Student, working on the FDS Project, 2017-
  • Kristiina Verro, PhD Student, Working on the XSL Stellar Library and Models. Co-supervising with Scott Trager, 2017-
  • Petra Awad, PhD Student, Working on filament extraction in astronomy, with applications towards GAIA and the Cosmic Web. Co-supervising with Kerstin Bunte (Bernoulli Institute for Computer Science, RUG), 2020-
  • Mohammad Faezi, PhD Student, Working on faint object detection in astronomy. Co-supervising with Michael Wilkinson (Bernoulli Institute for Computer Science, RUG), 2020-
  • Xu Xin, PhD Student, working on Understanding the Nature of Faint Dwarf Galaxies, 2021-
  • 2nd supervisor of Abolfazl Taghribi, PhD Student, SUNDIAL, working on developing probabilistic modelling algorithms to detect faint features in astronomy. 1st supervisor Kerstin Bunte (Bernoulli Institute for Computer Science, RUG), 2018-
  • 2nd supervisor of Marco Vasquez Beltran, PhD Student, working on developing piezoelectric deformable mirrors, with Bayu Jayawardhana (ENTEG), 2018-
  • 2nd supervisor of Jonas Bremer, PhD Student, working on the Epoch of Galaxy Formation, with Pratika Dayal, 2017-
  • 2nd supervisor of Michele Mastropietro, PhD Student, working on Simulations of Dwarf Galaxies in the Fornax Cluster, double degree with Gent University, SUNDIAL, co-supervising with Sven de Rijcke (Gent) and Michael Biehl (Bernoulli Institute for Computer Science, RUG), 2017-
  • 2nd supervisor of Jann Aschersleben, PhD Student, working on Combining Artificial Intelligence and Morphology for Dark Matter Searches. 1st supervisor Manuela Vecchi, other 2nd supervisor: Michael Wilkinson, 2020-
  • Bahar Bidaran, PhD Student, SUNDIAL, Honorary Group Member, working on kinematics and stellar populations of an infalling group in the Virgo Cluster. Supervisors: Anna Pasquali, Eva Grebel, Heidelberg, 2017-
  • Alan (Hung-Shuo) Su, PhD Student, SUNDIAL, Honorary Group Member, working on detailed morphology of dwarf galaxies in the Fornax Cluster. Supervisor: Heikki Salo, Oulu, 2017-

Former Members of my Research Group

  • Lorraine Putman, MSc Student, worked on the Globular Cluster Distribution in Fornax dwarf galaxies. Finished July 2021.
  • Antonio la Marca, MSc Student, worked on the dwarf and UDG population in the Hydra Cluster, Exchange Student, University of Naples, Italy. Finished February 2021.
  • Christiaan Seerden, Bachelor Student, worked on analyzing the Space Fluff Zooniverse results, Finished July 2021
  • Jesper Karsten, Bachelor Student, worked on faint object detection, Finished July 2021
  • Douwe Nobels, Bachelor Students, worked on Asymmetries in Dwarf Galaxies, Finished July 2021
  • Jill Straat and Alessandro Angrilli Muglia, Honours College students, worked on GAIA trails of globular clusters, 2021
  • Fabian Gunnink, Honours College student, worked on MUSE data of the active galaxy Fornax A, 2021
  • Lasse Vulto, Bachelor Student, worked on Darkness Measurements in the North of the Netherlands, Finished July 2021
  • Aku Venhola, PhD student, did a double degree in both Groningen and Oulu in Finland. Co-supervisor Heikki Salo. Worked on the FDS project. 2019
  • Elaheh Hamraz, PhD student, worked on young populations in Fornax Dwarfs. 2020
  • Seyda Sen, PhD student, worked on detailed stellar populations in dwarf elliptical galaxies. 2020
  • Nynke Visser, Bachelor Student,worked on Citizen Science to create awareness for Light Pollution, 2019
  • Kyung Lin Dong, Bachelor Student, worked on AGN activity in Jellyfish galaxies, 2019
  • Jaco Mentz, did a double degree with NWU in Potchefstroom, South Africa. Co-supervisor Ilani Loubser, working on dwarf galaxies in the Fornax Cluster. 2018
  • Pavel Mancera Pina, Master Student, worked on the population of dwarf galaxies and UDGs in nearby galaxy clusters, in collaboration with Alfonso Lopez Aguerri. 2018
  • Miguel Rodin Rodriguez, Master Student, studied the UDG population in the Coma cluster. 2018
  • Reinier Koet, Bachelor Student, worked on stellar population modelling, 2017
  • Akke Corporaal, Bachelor Student,worked on dust in Fornax dwarf galaxies, 2017
  • Mustafa Yildiz, PhD Student, worked on star formation and HI in elliptical galaxies, 2017
  • Anastasia Ponomareva, PhD Student, worked on Infrared Scaling Relations in Spiral Galaxies. 2017
  • 2nd supervisor of Benny Roeck, PhD Student, worked on Infrared Stellar Populations, IAC Tenerife, 1st supervisor Alexandre Vazdekis
  • Pece Podigacoski, PhD Student, worked on star formation in AGNs using Herschel data, so-supervised by Peter Barthel, 2016
  • Sofia Meneses-Goytia, PhD Student, worked in Infrared Stellar Population Models, co-supervised with Scott Trager, 2015
  • Anais Gonneau, PhD Student, worked on Carbin Stars in the X-shooter stellar library, double degree with the University of Strasbourg, supervised by Ariane Lancon (Strasbourg) and Scott Trager, 2015
  • Yanping Chen, PhD Student, worked on the X-shooter Stellar Library, co-supervised with Scott Trager, 2014
  • Mark den Brok, PhD Student, worked on Dynamics and Stellar Populations of Small Stellar Systems, 2012
  • Guido van der Wolk, PhD Student, worked on Mid-Infrared Imaging of Dust in Galaxies, 2011

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