Università degli Studi di trieste Dipartimento di Fisica Divisione di Astrofisica Dust Evolution in Galaxy Cluster Simulations PhD Candidate: Supervisor: Eda Gjergo Dr. Gian Luigi Granato School Coordinator: Co-Supervisor: Livio Lanceri Dr. Giuseppe Murante School Coordinator: Academic Advisor: Livio Lanceri Prof. Stefano Borgani January 30, 2019 Doctoral Thesis Academic Year 2017:2018 Cycle XXXI Dust Evolution in Galaxy Cluster Simulations EDA GJERGO Department of Physics Division Astrophysics University of Trieste Trieste, Italy 2018 Dust Evolution in Galaxy Cluster Simulations EDA GJERGO Department of Physics, Astrophysics Division University of Trieste © EDA GJERGO, 2018. PhD Candidate: Eda Gjergo Supervisor: Dr. Gian Luigi Granato, INAF Astronomical Observatory of Trieste Referee: Prof. Alessandro Bressan, SISSA International School for Advanced Studies Referee: Prof. Manolis Plionis, Aristotle University of Thessaloniki Doctoral Thesis 2018:2019 Department of Physics Astrophysics Division University of Trieste Via Bazzoni 2, Trieste, 34143 Telephone +39 040 3199 133 Email [email protected] A thesis submitted in fulfillment of the requirements for the degre of Doctor Philosophiae in Physics Typeset in LATEX Trieste, Italy 2018 iv Abstract Gaseous astrophysical media are splattered with solid agglomerates of molecules we call cosmic dust. Dust ranges in size between a few Angstroms and a few microns. While dust accounts only for one percent of the mass in the interstellar medium (ISM) of a Milky Way-like galaxy, it reprocesses about a third of its starlight, mostly in the UV and optical bands, and reemits it in the infrared. It is almost impossible to interpret correctly the spectral energy distribution (SED) of a galaxy without accounting for dust in some way. Dust affects not only the observation but also the evolution of galaxies. In fact, its surface is a catalyst for the formation of molecules, most important of which is H2. These molecules are efficient gas coolants and accelerate the gravitational collapse of molecular clouds, the cradles for star formation. Observations, in particular, are quite sensitive to dust properties such as compo- sition and grain size. A need emerges to include dust within theoretical models of galaxy and galaxy cluster evolution. The INAF Astronomical Observatory of Trieste, among other things, has developed a custom state-of-the-art cosmological N-body simulation of galaxy clusters based on the GADGET-3 code. The code cal- culates dynamics with a tree-Particle-Mesh method, where the simulated ‘particles’ actually represent massive ensembles of substances of different types, specifically dark matter, gas, stars, and black holes. The interactions between gas particles are treated with Smoothed-Particle Hydrodynamics, there is also star formation, radiative cooling, stellar and active galactic nuclei (AGN) feedback, and chemical evolution by stellar nucleosynthesis. Adding dust to this framework however has not been feasible until now. Tracing the continuous grain size (or its discrete approximation) would burden with ad- ditional dimensions the already heavy particle structure and calculations, slowing down the runs to impractical rates. Dust was instead treated in post processing v Abstract (Granato et al., 2015), and its properties were assumed a priori. Then Hirashita (2015) proposed an approximation. Instead of computing the grain size continuum, he postulated that dust grains are divided between large (nominally 0.1µm) and small (nominally 0.01µm). He therefore adapted a comprehensive one-zone dust evolution model (Asano et al., 2013) to this approximation. The binary grain size distribution was selected for both observational and modeling reasons. When dust grains are produced in the envelopes of evolved stars or in supernova remnants, the dominant size is around 0.1µm. In the ISM however, smaller dust is often just as prevalent or at times even dominant. This suggests that ISM evolution alters the grain size distribution. The phenomenon is captured in the modeling. Some processes are most efficient on one grain size over the other, or at times they have opposite effects on each size domain. We successfully adapted the Hirashita(2015) model to our custom GADGET-3 cos- mological zoom-in simulation code, specifically we embedded the model so that each simulated gas particle will trace, on top of the usual gas elements obtained from stel- lar and supernovae yields, also small and large dust grains. We tested our method on 14 15 four massive ( two M200 ≥ 3 × 10 M and two M200 ≥ ×10 M ) galaxy clusters. We also improved on previous dust production routines, which assumed a fixed dust condensation efficiency for each element. Instead, we form the two most representa- tive dust species observed in nature: carbonaceous dust and astrophysical silicates, based on the element abundance produced by stellar or supernovae yields. At the peak of star formation activity at z & 3 when proto-clusters start to assemble, we find that the gas particles in our simulations are rich in dust, as expected. In order to test the impact of dust processes on dust growth other than stellar production, we ran simulations with dust production and destruction alone, without any grain-gas or grain-grain interactions. Dust is enhanced by a factor of two to three due to the processes occurring in the ISM. We investigated variations of the model through different runs to understand the interdependence of all the processes. We were able to reproduce the dust abundance to metallicity relations observed in local galaxies, however we under-produced the dust content of galaxy clusters around z . 0.5 observed by IRAS, Planck, and Herschel observations. This discrepancy can be mended only by assuming a lower sputtering efficiency, which erodes dust grains in the hot Intracluster Medium (ICM). The abundance of the two dust species, silicates and carbonaceous dust, is also slightly different from the Milky Way average, and from the common values adopted in calculations of dust reprocessing. These differences may have a strong impact on the predicted SED. This method lays the vi Abstract groundwork for further developments, such as cosmological simulations of single galaxies, , or the refinement of radiative cooling routines with H2 catalysis on grain surfaces. vii Abstract viii Dedication I am indebted to a long list of mentors and friends which have inspired me and will continue to do so for many years to come. First of all, I would like to thank my primary supervisor Gian Luigi Granato for disciplining my enthusiasm into a more attentive, careful, and critical approach to scientific research. I am grateful for his painstaking guidance over these years, and for the constructive discussions. I appreciate Giuseppe Murante’s generosity in sharing his knowledge and for always finding the time to help everyone. I owe him a great deal of my improvements in computing. I am lucky to have been inspired by Stefano Borgani’s humble excellence and passion for cosmological research. I benefited from fruitful conversations with PierLuigi Monaco who impressed me with a sharp and clear mind. Special thanks to Francesca Matteucci who, while not an official supervisor, has been a pillar of strength to me with her warmth, passionate character, and dynamic scientific in- tuition. I value the support and optimism I received from her through thick and thin. Thanks to Steve Kuhlmann, for being beyond a supervisor, a dear friend, for in- troducing me to the world of research with countless opportunities. Thank you for believing in my potential and for encouraging me to pursue a career in Astro- physics. Thanks to Arthur Lubin for inspiring me with his resilience, charisma, love of mathematics, and ability to always let me see and seek the big picture. Thanks to Yurii Shylnov for being one of the most honest, humble, yet excellent professors I have ever had. Thanks to Salman Habib, Katrin Heitmann, Sergei Shandarin, for the scientific perspicacity and thought-provoking conversations. Thanks to Fabio Pasian for encouraging me to apply to the PhD program in the first place. Thanks to Cinthia Ragone-Fuguera, Gabriella de Lucia, Gabriele Cescutti, Andrea Biviano, Emiliano Sefusatti, Emiliano Munari, Elena Rasia, Barbara Sartoris, Fabio Fontanot, Veronica Biffi, Umberto Maio, David Goz, Alex Saro, and Marta Spinelli for galvanizing my scientific curiosity with the arrays of research fields and person- alities they havex exposed me to. Thanks to my fellow PhD students who showed me excellence does not come at the cost of a balanced life, but because of it. Thanks ix Dedication to my friends Emanuele Spitoni, Fiorenzo Vincenzo, Lorenzo Gioannini, Carlo De Masi, Valeria Grisoni, Anna Zoldan, Chiara Moretti, Luigi Bassini, Federico Rizzo, Paolo Simonetti, Dan Eckhart, and Angela Faust, whom between jokes, intellec- tual curiosity, authenticity, and originality, brought fun into my days, softened my quarter-life crisis, and affected my outlook on important issues. Thanks to my dearest friends Carlo e Zina Magnelli, Linda Corsi, and Maria Luisa Princivalli, whose wisdom, optimism, affection, knowledge, and spiritual generosity brightened my life when I needed it most. You are like family. Margherita Hack, your memory lives within me every day. You showed me a way of being I aspire to master, with your relentless dedication, pure heart, minimalist lifestyle, scientific enterprise, devotion to humanity, to nature, to fairness. Thank you for having opened your heart to me and for believing in me from the very start. Dear Aldo de Rosa, I treasure you more than you could remember in your last years. I will never forget how nurturing, affectionate, and encouraging you’ve been to me, and how you helped me grow in between jokes and tease. I owe any and all of my achievements to my mother, who raised me to value integrity, kindness, justice, and excellence, and who devoted every ounce of herself to help me grow every day. Thank you for your unconditional love and positivity, for your trust and encouragement.