Research

The feedback of actively accreting supermassive black holes in the centers of galaxies (i.e. active galatic nuclei (AGN)) can severely affect the evolution of its host galaxy by truncating or triggering/amplifying the star formation. Therefore, it is of utmost interest to understand the processes involved in the triggering of those black holes. For decades, it was a widely accepted scenario that the occurrence of AGNs are a result of a merger of massive gas-rich galaxies. However, over the last years the relevance of major interactions for the growth of black holes has been extensively tested, leading to a model in which the merging of two such galaxies is playing only a sub-dominant role.

With my work I focus on the question whether this conclusion is also valid for black holes with highest Eddington ratios, in other words black holes with the highest accretion rates relative to their mass. As a large amounts of gas and its transfer to the central region in a short time frame is required, it may very well be that for this particular population of black holes, major galaxy mergers are still the best or maybe only suitable mechanism.

To examine this question I analyze the fractions of merging AGN host galaxies at redshift z∼2 (peak of black hole growth) and at z∼0.2, and subsequently compare them to the respective merger fractions of two matched samples of inactive galaxies. A significant increase of the AGN merger fractions with respect to the control samples would mean that major galaxy mergers are indeed a dominant trigger for the selected population of AGNs with the highest Eddington ratios.

The plot shows the results of the two studies. While there is no significant difference in the merger fractions for the sources at redshift z∼2, a discrepancy appears in the merger fractions at z∼0.2. This indicates that major galaxy mergers play only a negligible role in triggering AGNs at z∼2, but becomes an essential driver for comparable AGNs in the local universe. More details can be found in Marian et al., 2019 and Marian et al., 2020 (accepted).

Currently I am working with simulated data from the cosmological simulation IllustrisTNG to verfiy the observational results presented above and to find any possible distinctions between simulation and observations.

To order the sources with respect to the strength of their merger features I also developed an easy-to-use tool to classify images. It offers the possibility to sort an arbitrary number of images by drag and drop and/or keyboard commands, features a fanybox gallery to view all the images in an overlayed and larger version, and the option to export the final order into a generic text file. You can find more detailed info and a guide on how to use it on Github.

Publications

ADS link

  • Marian V., Jahnke K., et al., "A significant excess in major merger rate for AGNs with the highest Eddington ratios atz < 0.2", 2020, accepted
  • Taufik Andika, I.,[...], Marian V., et al., "Probing the Nature of High Redshift Weak Emission Line Quasars: A Young Quasar with a Starburst Host Galaxy", 2020, in press
  • Marshall, M. A.,[...], Marian V., et al., "Limits to Rest-frame Ultraviolet Emission from Far-infrared-luminous z ∼ 6 Quasar Hosts", 2020, ApJ, 900, 21
  • Gibbs, A.,[...], Marian V., et al., "EDEN: Sensitivity Analysis and Transiting Planet Detection Limits for Nearby Late Red Dwarfs", 2020, AJ, 159, 169
  • Marian V., Jahnke K., Mechtley M. et al., "Major mergers are not triggering high-accretion AGNs at z ∼ 2", 2019, ApJ, 882, 141
  • Marian V., Ziegler B., Kuchner U. & Verdugo M., "Color gradients reflect an inside-out growth in early-type galaxies of the cluster MACS J1206.2-0847", 2018, A&A, 617, A34
  • Marian V., "Internal color gradients and distributions of stellar populations of early-type galaxies in z ∼ 0.4 CLASH clusters", 2016, Master thesis
  • Marian V., "Das System der Zwerggalaxie um die Milchstraße", 2012, Bachelor thesis

Contributed talks

Curriculum Vitae

You can find a (german and more detailed) pdf version of my CV here


Employment

03/2017- PhD, Max-Planck-Institut für Astronomie (Supervisor: Knud Jahnke)
10/2010 - 08/2015 T-Mobile Austria GmbH: Retail Sales Agent
09/2009 - 10/2010 Gigaset Communications Austria GmbH: Promotion
08/2007 - 09/2008 Cosmos Elektrohandel GmbH: Retail Sales Agent

Education

11/2016 - 02/2017 Project Managment (IPMA), AkademikerInnenzentrum Wien/University of Graz: Modern Management VI
03/2013 - 07/2016 MSc in astronomy, University of Vienna (Supervisor: Bodo Ziegler)
10/2003 - 02/2013 Bakk. rer. nat. (BSc) in astronomy, University of Vienna (Supervisor: Gerhard Hensler)

Schools

2020 Various Coursera courses on Machine Learning and Data Science (with Python and SQL)
2019 IWR School: A Crash Course in Machine Learning with Applications in Natural- and Life Sciences
2018 48th Saas-Fee course: Black hole formation and growth
2017 Opticon NEON Observing School

Outreach

2020 Report in October edition of Sterne und Weltraum about a pulsating white dwarf in an eclipsing binary system
2019 Nacht der Forschung
2019 Expert for students of Deutsche Schülerakademie with focus on UV, optical and IR observations
2019 Explore Science
2018 Max-Planck-Tag/MPG-Week
since 2017 Führungen (Guided tours)

Skills

Programming Python (NumPy, Matplotlib, Seaborn, scikit-learn, SciPy, AstroPy, IPython, pandas), FORTRAN, HTML/CSS, R
Astronomy TopCat, SAO DS9, SkyCat, Source Extractor, Galfit, EzGal, Galapagos, Megamorph, PSFMC, THELI
Office LaTex, SAP, MS Office (Word, Excel, Powerpoint), Prezi
OS MS Windows, Linux (Ubuntu, Linux Mint, openSUSE)
Languages German (mother tounge/C2), English (proficient/C2), Romanian (basic/A1)

Observing experience

2 nights Leopold-Figl-Observatory (Lab course)
2 nights Nordic Optical Telescope (Opticon NEON Observing School)
1 night Isaac Newton Telescope (Opticon NEON Observing School)
9 nights MPG/ESO 2.2m
4 nights CAHA Calar Alto 1.23m (remote)

Outreach

Being in the privileged position to get paid to study the wonders of the Universe, I feel a certain responsibility to participate in activities which gives the general public the chance to learn about our daily work and what and why astronomers are doing what they are doing. Additionally it makes a lot of fun and it is always a pleasure to see the fascination in the eyes of the people.

To that end I work as an outreach fellow at the Haus der Astronomie (Center for Astronomy Education and Outreach) and give guided tours, in which I present for example our digital planetarium (including an interactive journey through the Universe), the KING telescope or a model of the 100 stars neighboring our Sun. In addition I am always happy to contribute to outreach events like Explore Science or Nacht der Forschung. I also had the chance to write a report for the October edition of Sterne und Weltraum, the biggest german magazine to present astronomy/astrophysicis in a popular scientific way.

About me

Since life has countless things to offer my devotion for a hobby changes on a regular basis, which means that I don’t have this one and only hobby. I am rather interested in numerous things. Still, there are some activities and interests that come around repeatedly, which rekindle my enthusiasm and passion:

Data Science & Machine Learning

While working with large datasets during my PhD studies, my interest in machine learning, data science and visualization grew. I took the courses 'Machine Learning' by Andrew Ng and 'Applied Data Science with Python Specialization', which were offered on Coursera in order to fill possible knowledge gaps and to put existing skills on a good foundation. The art of extracting and displaying information from huge, staggering datasets, as well as making predictions based on that data, is one of the most exciting topics for me.

Photography

Playing (Emphasis on "playing"!) around with our Nikon D90 and our different lenses is always a pleasure, especially at and in foreign places or during a starry night. Consequently my main focus lies on landscape/animals and architecture as well as astrophotography. For the latter I am hoping to utilize the KING telescope on our MPIA campus a little bit more in the future. By clicking below on the respective images you can open three galleries showing a few examples of the pictures I have taken during the last couple of years. (All images are not post processed.)

Architecture

Landscapes

Astrophotography

Lego

Since my early days I enjoy to build models with the Danish bricks. In the last couple of years I started to try to collect as many UCS Star Wars models as possible, which is more or less constrained by my wallet and space at home. At the moment I call 10 models ( TIE Interceptor, X-Wing Fighter, Rebel Blockade Runner, Imperial Star Destroyer, Y-Wing Attack Starfighter, Imperial Shuttle, Obi-Wan's Jedi Starfighter, B-Wing Starfighter, Snowspeeder & Millenium Falcon and counting) my own.
Furthermore I am always interested in the fan-made models presented on Lego Ideas (former Cuusoo), a portal where everyone can upload his/her creation. Occasionally a model with enough votes will get selected by Lego itsel for global production and distribution. Examples in my possesion are the Ecto-1, the DeLorean from Back to the Future, Wall-E, the Mars rover Curiosity or the Saturn V incl. Command and Lunar module. A model especially every astrophysicist should check out is the (E-)ELT by Frans Snik. And with a little luck you can even build the JWST before it launches!
Finally, I try to create my own models as well. After a model of Star Trek's Enterprise-B I am currently trying to design the Enterprise-E. The ultimate goal of course is to actually build those sets...

Video games & Comics

If time allows and to relaxe I like to indulge myself into sophisticated, story-driven, immersive video games, mostly created by Indie studios. ABZU, Botanicula, Northgard, Ori, The Talos Principle, Firewatch, Portal, The Turing Test, Jotun, The Stanley Parable, That Dragon Cancer or the Town of Light are a selection of games I already played or have yet to enjoy.

Since I am a huge fan of Scrooge McDuck I am a big admirer of the works of Carl Barks , the inventor of this character, and especially Don Rosa, who built on the creations of Carl Barks in a uniquely fashion. His drawing style combined with his sense of humor are always a delight for me. Meeting him at a comic convention in Vienna, getting some of his works autographed, and also receiving a handful of his home-grown chilli peppers, was a memorable occasion for me.