Dust Across Galaxies

Universitàdegli Studi di Trieste Department of Physics Doctoral School of Physics Dust across galaxies PhD candidate: Supervisor: Lorenzo Gioannini Prof.ssa Francesca Matteucci Co-supervisor: Dott. Giovanni Vladilo Cycle XXX Contents 1 Introduction7 1.1 Dust in the Interstellar medium...................8 1.1.1 A picture of interstellar dust................9 1.1.2 Dust observations and properties.............. 11 1.2 Computing dust evolution in the ISM through chemical evolution models................................. 16 1.2.1 Plan of the thesis....................... 19 2 A new model of galactic chemical evolution with dust 23 2.1 Chemical evolution model...................... 23 2.1.1 Basic equations........................ 24 2.2 Dust chemical evolution model................... 26 2.2.1 Dust formation........................ 26 2.2.2 Dust destruction....................... 33 2.2.3 Dust accretion........................ 34 3 Dust properties in Damped Lyman Alpha systems 37 3.1 Introduction.............................. 37 3.2 Dust predictions for dwarf irregular galaxies............ 40 3.2.1 Dust-to-gas ratio....................... 44 3.2.2 Dust composition....................... 48 3.2.3 Dust processes and the critical metallicity......... 48 3.3 Dust depletion patterns of Si and Fe................ 49 3.3.1 How to study depletion in DLAs.............. 49 3.3.2 DLA data........................... 51 3.3.3 Results............................ 52 3.3.4 Discussion........................... 55 3.4 Dust chemical composition..................... 61 3.4.1 Abundance ratios in dust.................. 61 3.4.2 Comparison with galactic evolution models with dust production............................ 66 3.4.3 Interpretation: the composition of dust.......... 68 3.5 Conclusions.............................. 74 4 Dust in the Milky Way: the Galactic Habitable Zone 77 4.1 Introduction.............................. 77 4.1.1 Studying the GHZ with chemical evolution models.... 77 4.1.2 Dust in the GHZ....................... 79 3 4 CONTENTS 4.2 Probabilities of finding planets around FGK and M stars..... 80 4.3 Milky Way chemical evolution model that includes dust..... 82 4.3.1 Two-infall model....................... 83 4.4 Results................................. 85 4.4.1 Milky Way disk with dust.................. 85 4.4.2 Evolution of the Dust-to-gas ratio............. 87 4.4.3 Terrestrial habitable planets around FGK and M stars.. 88 4.4.4 GHZ maps for FGK and M stars.............. 93 4.5 Conclusions.............................. 95 5 Dust in elliptical galaxies 97 5.1 The model of an elliptical galaxy.................. 99 5.2 Dust mass at high redshift...................... 100 5.3 Stellar dust production........................ 102 5.3.1 The effect of Type Ia SNe.................. 102 5.3.2 AGB stars versus Type II SNe............... 104 5.4 Conclusions.............................. 107 6 Dust rate across the Universe 109 6.1 Introduction.............................. 109 6.2 Evolution of galaxies of different morphological type....... 111 6.2.1 The dust-to-gas ratio in the Local Universe........ 112 6.3 Cosmic Rates............................. 117 6.3.1 CSFR: Cosmic star formation rate............. 119 6.3.2 Cosmic dust budget and cosmic dust rate......... 121 6.3.3 Evolution of the cosmic mean metallicity......... 126 6.4 Conclusions.............................. 129 7 Conclusions 131 Summary of the thesis In this thesis, we investigate the evolution of dust mass and chemical composition in different galaxies by means of detailed chemical evolution models which account for the presence of dust. We present a new model (Gioannini et al., 2017a), in which we adopt updated prescriptions for dust formation in Asymp- totic Giant Branch (AGB) stars and Type II SNe (Piovan et al., 2011; Dell'Agli et al., 2017), as well as for dust processes in the interstellar medium (ISM), i.e. dust accretion and destruction (Asano et al., 2013). We relax the instantaneous recycling approximation and therefore we take into account stellar lifetimes. In this way, we can predict in detail the evolution of the abundances of single elements both in the dust and in gas phase of the ISM, and distinguish the contributions from different sources during the galactic time. We study the dust evolution in galaxies of different morphological type, i.e. dwarf irregulars, spirals, Milky Way-type and ellipticals: our model has proven to be very useful to study various dust properties in these galaxies, such as dust mass, dust-to-gas (DG) ratio and chemical composition. In our approach, the main difference between galaxies is the star formation history: in ellipticals it is assumed a very fast and intense star formation rate, and this rate decreases going towards spirals, irregulars and smaller galaxies. First, we compare our model predictions for a typical dwarf irregular galaxy with chemical abundances measured in Damped Lyman Alpha (DLA) systems (Wolfe et al., 1986, 2005). After having reproduced the abundances of volatile elements S and Zn (unaffected by the presence of dust), we study the depletion patterns of refractory elements (Si and Fe), which tend to be incorporated in the dust phase. Our study suggests that Fe and Si undergo a different history of dust formation and evolution. We show evidences that Fe is mainly incorporated into iron-rich solid nano-particles, which may form by dust growth in the ISM. This dust component has never been taken into account in previous models. We also provide a new method, based on DLA column density measurements and the ratio between volatile and refractory elements, to give for the first time an estimate of the chemical abundance ratios inside dust grains. In this way, we try to disentangle the main dust constituents and predict their evolution: in particular, we focus on the fraction between silicates and metallic particles and between pyroxenes and olivines. Concerning the Milky Way, we present the evolution (in space and time) of the DG ratio in the context of the galactic habitable zone (GHZ), defined as the region with highly enough metallicity to form planetary systems capable of sustaining life (Gonzalez et al., 2001). In this study, we provide theoretical prescriptions of the DG ratio and metallicity for models of planetary systems formation (Spitoni et al., 2017). 5 6 CONTENTS Then we focus our study on high redshift elliptical galaxies, and we try to disentangle the responsible processes for the sudden appearance of metals and dust observed in those objects. The first metals and dust appear very early since they are both produced by short living massive stars (core-collapse SNe), on the time-scales of few tenths of million years. In their initial burst of star formation, the metallicity can attain almost a solar value after one hundred million years and the same is true for dust, to which also AGB stars contribute on time-scales equal or larger than 30 million years. Finally, we study the cosmic dust rate (CDR) across the Universe by assum- ing that the cosmic dust abundance results from the contribution of galaxies of different morphological type averaged in a unitary volume of the Universe (Gioannini et al., 2017b). These galaxies are assumed to evolve in number density according to their weight in the luminosity function at different redshifts and different cosmological scenarios (Vincoletto et al., 2012; Pozzi et al., 2015). Parallel to the CDR we compute the cosmic star formation rate (CSFR) as well as the cosmic rate of metallicity. Our predictions are extreme important to understand the roles of dust production, accretion and destruction in the CDR evolution. Our best scenario predicts a dust rate peak between 2 < z < 3 and reproduce the observed CSFR. Eventually, we estimate the comoving dust density parameter Ωdust and we find a good agreement with data for z<0.5. Chapter 1 Introduction Light is the most important source in Astrophysics and it is the only media- tor we have to obtain information about astronomical objects outside the Solar System (except for the recent detections of gravitational waves, e.g. Abbott et al. 2016; The LIGO Scientific Collaboration et al. 2017; The LIGO Scien- tific Collaboration & The Virgo Collaboration 2017). In the interstellar and intergalactic medium, dust always modifies the light coming from background sources, and therefore we constantly must correct observations to perform a truthful interpretation of the Universe. In this way, the best we know dust the most accurate information of the Universe we can have. The first evidence for the presence of interstellar dust was performed by Struve(1847), when he noticed that star counts appear to decrease with in- creasing distance from the Earth. Kapteyn(1909) suggested that this effect could arise from the light absorption of the intervening material located between stars. It was Robert Trumpler who first discovered the wavelength dependent absorption of the light, called \extinction", and concluded that it was caused by the scattering and absorption by material made of solid grains in the interstellar medium (ISM) (Trumpler, 1930). When Astronomy was mainly conducted at optical wavelength, dust was considered as an annoying component, an obstacle to our understanding of the Universe. However, in the last decades this field of study has become extremely important, as dust it is involved in a great variety of physical processes. In fact, dust absorbs the ultraviolet (UV) stellar light and re-emits in the infrared (IR) band (Draine & Lee,

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