Research

The feedback of 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 growth of black holes. For decades, it was a widely accepted scenario that the occurrence of AGNs are a result of a merger of 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 gas-rich galaxies is playing a sub-dominant part for the occurrence of an AGN.

Probability distributions for the inferred merger fractions of our AGN host galaxies (blue) and inactive galaxies (red) at z∼2. The solid line shows the mean of the AGN merger fraction, while the dashed lines denote the 1σ interval. Click on the image for a larger version.
With my work I focus on the question whether this conclusion is also valid for black holes with highest accretion rates. As large amounts of gas and its transfer to the central region is needed, it may very well be that for this particular population of black holes major mergers are still the best or maybe only suitable mechanism.

To examine this question we analyze the merger fractions of AGN host galaxies at z∼2 (peak of black hole growth) observed by HST, and at z∼0.2 observed with VLT/FORS2 and subsequently compare them to the fractions of two matched samples of inactive galaxies. As all other parameters (mass, redshift, S/N, instrument and filters, residuals) between the AGN samples and the respective selections of inactive galaxies are comparable, a significant increase of the AGN merger fractions means that major merging is in those particular cases a dominant trigger for the growth of black holes.

The plot shows our result for our z=2 sample. We derived merger fractions for both samples, amounting to fm,AGN = 0.24 ± 0.09 for the AGN host galaxy sample and fm, ina = 0.19 ± 0.04 for the inactive galaxies. We find no significant enhancement of the merger fractions for the AGN host galaxies with respect to the sample of inactive galaxies, which leads us to the conclusion that even black holes showing highest accretion rates at the peak of cosmic AGN activity are not fueled by major mergers, but rather by secular evolution, bar instabilities or minor merger events. More details can be found in Marian et al., 2019.

Publications

ADS link

  • Marian V., Jahnke K., Mechtley M. et al., "Major mergers are not triggering high-accretion AGNs at z ∼ 2", 2019, ApJ, accepted, arXiv:1904.00037
  • 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


Education

2017- PhD, Max-Planck-Institut für Astronomie (Supervisor: Knud Jahnke)
2013 - 2016 MSc in astronomy, University of Vienna (Supervisor: Bodo Ziegler)
2003 - 2016 Bakk. rer. nat. (BSc) in astronomy, University of Vienna (Supervisor: Gerhard Hensler)

Schools


Employment

2010 - 2015 T-Mobile Austria GmbH: Retail Sales Agent
2009 - 2010 Gigaset Communications Austria GmbH: Promotion
2007 - 2008 Cosmos Elektrohandel GmbH: Retail Sales Agent

Skills

Programming Python (NumPy, Matplotlib, SciPy, AstroPy, IPython, pandas), FORTRAN, HTML/CSS
Astronomy TopCat, SAO DS9, SkyCat, Source Extractor, Galfit, EzGal, Galapagos, Megamorph, GILDAS
Office LaTex, SAP, MS Office (Word, Excel, Powerpoint), Prezi
OS MS Windows, Linux (Ubuntu, Linux Mint, openSUSE)
Languages German, English, Romanian

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), KING telescope or model of the 100 stars neighboring our Sun.

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:

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) 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.