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(1)Thesis. Kinematics of star-forming galaxies at cosmic noon. GIRARD, Marianne. Abstract Integral field spectrographs are able to capture simultaneously hundreds of spectra covering the whole area of a galaxy with good spatial and spectral resolution. These instruments in the near-infrared allow us to study emission lines in the optical of high-redshift galaxies (1 < z < 3) to obtain different physical properties of the galaxies, such as their kinematics. The kinematics of galaxies around the peak of the star formation rate density, at cosmic noon, can give key information to understanding their evolution over cosmic time. In this thesis, I analyse the kinematics of distant lensed galaxies to explore how the kinematics depend on galaxy physical properties, such as the stellar mass and morphology. The gravitational lensing also allow me to obtain a better spatial resolution to study star-forming clumps and compare different kinematic tracers.. Reference GIRARD, Marianne. Kinematics of star-forming galaxies at cosmic noon. Thèse de doctorat : Univ. Genève, 2019, no. Sc. 5349. DOI : 10.13097/archive-ouverte/unige:120367 URN : urn:nbn:ch:unige-1203676. Available at: http://archive-ouverte.unige.ch/unige:120367 Disclaimer: layout of this document may differ from the published version..

(2) UNIVERSITÉ DE GENÈVE Département d’astronomie. FACULTÉ DES SCIENCES Professeur Daniel Schaerer et Dr. Miroslava Dessauges-Zavadsky. Kinematics of Star-Forming Galaxies at Cosmic Noon. THÈSE présentée à la Faculté des Sciences de l’Université de Genève pour obtenir le grade de Docteur ès sciences, mention Astronomie et Astrophysique. par. Marianne Girard de Sherbrooke (Québec, Canada). Thèse N◦ 5349. GENÈVE Observatoire Astronomique de l’Université de Genève 2019.

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(6) Résumé Les spectrographes à champ intégral sont maintenant capable d’obtenir simultanément des centaines de spectres sur tout l’étendue d’une galaxie, et ce, avec une excellente résolution spatiale et spectrale. L’arrivée de ces instruments dans l’infrarouge proche, comme KMOS et SINFONI au Very Large Telescope (VLT), permet d’étudier les raies d’émission du visible des galaxies distantes, avec un grand décalage vers le rouge (1 < z < 3), et d’obtenir diverses propriétés de ces galaxies, comme leur cinématique. La cinématique des galaxies autour du pic de densité du taux de formation stellaire, au midi cosmique, peut donner de l’information essentielle afin de comprendre l’évolution des galaxies. Dans cette thèse, j’analyse la cinématique des galaxies distantes qui sont lentillées gravitationnellement en dérivant les cartes de vitesse et de la dispersion des vitesses et en étudiant les courbes de rotation et leur classification cinématique. J’explore comment la cinématique de ces galaxies distantes dépend de propriétés telles que la masse stellaire et la morphologie. L’effet de lentille gravitationnelle permet aussi d’obtenir une meilleure résolution spatiale et aussi d’observer des objets moins lumineux, comme des galaxies de faibles masses. Le premier travail que j’ai effectué est sur une galaxie lentillée observée avec l’instrument SINFONI. Cette galaxie possède des régions de formation stellaire qui sont très lumineuses et qui sont visibles dans les cartes de flux Hα. L’objectif de ce travail est d’analyser les propriétés physiques de chacune de ces agglomérations afin de les comparer entres elles, mais aussi aux propriétés globales de la galaxie. Faire de telles comparaisons permet de mieux comprendre la formation de ces agglomérations dans les galaxies distantes. La deuxième partie de mon travail est sur l’étude des galaxies de faible masse à l’aide d’observations de deux différentes études: le KMOS LENsing Survey KLENS et le KMOS Lens-Amplified Spectroscopic Survey - KLASS. Il a été possible de comparer comment la cinématique de ces galaxies de faible masse, qui sont les ancêtres de la Voie Lactée, diffèrent de celles des galaxies massives, majoritairement observées jusqu’à maintenant. J’ai aussi exploré les propriétés qui influencent la fraction de galaxies qui sont dominées par la rotation ainsi que l’évolution des propriétés cinématiques, comme la dispersion de vitesse avec le décalage vers le v.

(7) rouge et la masse stellaire ainsi que la relation de Tully-Fisher. De plus, j’ai pu comparer la cinématique de deux galaxies, le Cosmic Snake et A521, en utilisant deux traceurs différents, soit la raie d’émission [OII] qui trace le gaz ionisé et le CO qui trace le gaz moléculaire observés avec MUSE et ALMA, respectivement. J’ai ensuite exploré comment le rayon et l’épaisseur des disques de gaz ionisé et moléculaire peuvent influencer la cinématique que l’on observe dans les galaxies.. vi.

(8) Foreword Integral field spectrographs are able to capture simultaneously hundreds of spectra covering the whole area of a galaxy with good spatial and spectral resolution. These instruments in the near-infrared, such as KMOS and SINFONI installed at the Very Large Telescope (VLT), allow us to study emission lines in the optical of highredshift galaxies (1 < z < 3) to obtain different physical properties of the galaxies, such as their kinematics. The kinematics of galaxies around the peak of the star formation rate density, at cosmic noon, can give key information to understanding their evolution over cosmic time. In this thesis, I analyse the kinematics of distant lensed galaxies by deriving their velocity and velocity dispersion maps and studying their rotation curves and kinematic classifications. I explore how the kinematics depend on galaxy physical properties, such as the stellar mass and morphology. The gravitational lensing also allow me to obtain a better spatial resolution and to observe fainter galaxies. The first part of my work is on a lensed galaxy observed with SINFONI/VLT. This galaxy is characterized by luminous star-forming regions or clumps, that are visible in the Hα map. The objective of this work is to analyse the physical properties of each clump in order to compare them to each other, but also to the global properties of the galaxy. These comparisons can help us to understand how these giant clumps formed in high-redshift galaxies. In the second part, I focus on the kinematics of low-mass galaxies, using observations from two surveys: the KMOS LENsing Survey, KLENS; and the KMOS Lens-Amplified Spectroscopic Survey, KLASS. I compare the kinematics of these low-mass galaxies, which are the progenitors of the Milky Way, to massive galaxies to understand how they differ from each other. I explore the properties that can influence the fraction of rotation-dominated galaxies and study the evolution of the Tully-Fisher relation and different kinematics properties, such as the velocity dispersion and stability ratio with redshift and stellar mass. In the last part of this thesis, I compare the kinematics of two highly magnified galaxies, the Cosmic Snake and A521, using two different tracers: the [OII] emission line tracing the ionized gas and the CO line tracing the molecular gas from MUSE/VLT and ALMA observations, respectively. I investigate how the ionized vii.

(9) and molecular gas disk geometrical properties, such as the radius and thickness, can affect the observed rotation curve of galaxies.. viii.

(10) Acknowledgements Youhou, I’m done! I can now rest and watch the three extended version of LOTR. But it would not have been possible without many friends and people around me that helped and encouraged me in many ways. First, I wish to thank my supervisors, Mirka and Daniel, for their support during my PhD as well as the galaxy people and collaborators. A special thank to Corinne for everything she did and still do for women in astronomy. I want to thank all the great people I met since I moved to Switzerland: Anth, David H., David M., John, Jon, Pascal to name just a few, with whom I had lot of fun in the past couple of years eating fondue at the ice rink and Bain des Paquis, going to the hockey, hiking, karaoké, at cave ouvertes, the cow festivals, and without forgetting some great trips to Zurich, Copenhagen and Croatia. I will definitely miss all of you as well as the paprika chips, cheese, wine and mountains of Switzerland. Also had a great time having tea, more fondue and wine on the roof with the planets people: Ati, Emily, Heather, Helen, Louise, and many other. Hope I will see you all in Australia! :) Finalement, un gros merci aussi à ma famille qui m’a toujours encouragé à poursuivre et étudier même si cela m’a amené à partir vivre de l’autre côté de la planète. Et un merci à Marie-Ève et mes amis du Québec qui sont même venus me voir en Suisse pendant mon séjour ici.. ix.

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(12) Contents Résumé. v. Foreword. vii. Acknowledgements. ix. Contents. xi. List of Tables. xv. List of Figures. xvii. 1 Introduction 1.1 A brief history of galaxies . . . . . . . . . . . . . . . . . . . . . . 1.1.1 Discovery of the galaxies . . . . . . . . . . . . . . . . . . 1.1.2 First kinematic measurements . . . . . . . . . . . . . . . 1.2 The nearby galaxies . . . . . . . . . . . . . . . . . . . . . . . . . 1.2.1 Global properties of nearby galaxies . . . . . . . . . . . . 1.2.2 Kinematic properties of nearby galaxies . . . . . . . . . . 1.2.2.1 Rotation of nearby galaxies . . . . . . . . . . . 1.2.2.2 Velocity dispersion of nearby galaxies . . . . . . 1.2.2.3 The Tully-Fisher relation in the local Universe . 1.3 The distant galaxies . . . . . . . . . . . . . . . . . . . . . . . . . 1.3.1 Global properties of high-redshift galaxies . . . . . . . . . 1.3.2 Kinematic properties of high-redshift galaxies . . . . . . . 1.3.2.1 Recent surveys . . . . . . . . . . . . . . . . . . 1.3.2.2 Main results from the surveys . . . . . . . . . . 1.3.2.3 The Tully-Fisher relation at high redshift . . . . 1.3.3 Kinematics of low-mass galaxies . . . . . . . . . . . . . . 1.3.3.1 Previous surveys on low-mass galaxies at z > 0.5 1.3.3.2 Observing low-mass galaxies with gravitational lensing . . . . . . . . . . . . . . . . . . . . . . 1.4 Main questions . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 Observations and Analysis of Galaxies xi. . . . . . . . . . . . . . . . . .. 1 1 1 3 4 4 6 7 9 9 10 10 15 15 18 23 25 26. . 27 . 31 33.

(13) 2.1 2.2 2.3. Imaging . . . . . . . . . . . . . . . . . . . . Spectroscopy . . . . . . . . . . . . . . . . . 2.2.1 Emission lines . . . . . . . . . . . . . 2.2.2 Characterising the interstellar medium Integral Field Spectroscopy . . . . . . . . . . 2.3.1 Instruments description . . . . . . . . 2.3.2 Mapping and modeling the kinematics 2.3.3 Measurement of υrot and σ0 . . . . . 2.3.4 Kinematic classification . . . . . . . .. . . . . . . . . .. . . . . . . . . .. . . . . . . . . .. . . . . . . . . .. . . . . . . . . .. . . . . . . . . .. . . . . . . . . .. . . . . . . . . .. . . . . . . . . .. . . . . . . . . .. . . . . . . . . .. . . . . . . . . .. 33 34 34 36 38 38 39 43 46. 3 Detailed analysis of a clumpy lensed galaxy at z ∼ 1.6 49 3.1 Context . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 49 3.2 Publication : Girard et al. 2018b . . . . . . . . . . . . . . . . . . . 49 4 Kinematic Analysis of Low-Mass Galaxies at Cosmic Noon 4.1 Context . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.2 KMOS LENsing Survey - KLENS . . . . . . . . . . . . . . . . . 4.2.1 Publication : Girard et al. 2018a . . . . . . . . . . . . . . 4.2.2 Unpublished work: Galaxies from the clusters A2744 and RXJ1347 . . . . . . . . . . . . . . . . . . . . . . . . . . 4.3 KMOS Lens-Amplified Spectroscopic Survey - KLASS . . . . . . 4.3.1 Publication: Fontana et al. 2019 . . . . . . . . . . . . . . 4.3.2 Publication: Girard et al. (in preparation) . . . . . . . . . 4.3.2.1 Data reduction, emission line measurements and SED fitting . . . . . . . . . . . . . . . . . . . . 4.3.2.2 Kinematic maps and modeling . . . . . . . . . . 4.3.2.3 Velocity dispersion measurement comparison . . 4.3.2.4 Kinematic classification . . . . . . . . . . . . . 4.3.2.5 The Tully-Fisher relation . . . . . . . . . . . . . 4.3.2.6 Evolution of the kinematic properties . . . . . . 4.3.2.7 Conclusion and future work . . . . . . . . . . . 4.3.2.8 Figure of the kinematic maps . . . . . . . . . .. 61 . 61 . 61 . 61 . . . .. 82 83 85 90. . . . . . . . .. 90 91 92 94 95 99 102 102. 5 Comparison of the ionized and molecular gas kinematics of two strongly lensed galaxies at z ∼ 1 111 5.1 Context . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 111 5.2 Publication: Girard et al. (submitted) . . . . . . . . . . . . . . . . . 111 6 Conclusion and future prospects 123 6.1 Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 123 6.2 Future prospects . . . . . . . . . . . . . . . . . . . . . . . . . . . . 126 7 Publication list. 129. A Contributing author publications. 133 xii.

(14) A.1 The galaxy CR7 – by Matthee et al. (2017) . . . . . . . . . . . . . . 133 A.2 The CORALIE survey for southern extrasolar planets – by Rickman et al. (2019) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 148 A.3 SIGNALS – by Rousseau-Nepton et al. submitted . . . . . . . . . . 163 References. 183. xiii.

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(16) List of Tables 4.1 4.2 4.3. Galaxy properties of KLENS . . . . . . . . . . . . . . . . . . . . . . . 82 Galaxy properties of KLASS . . . . . . . . . . . . . . . . . . . . . . . 93 Kinematic properties of KLASS obtained with GalPaK3D . . . . . . . . 96. xv.

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(18) List of Figures 1.1 1.2 1.3 1.4 1.5 1.6 1.7 1.8 1.9 1.10 1.11 1.12 1.13 1.14 1.15 1.16 1.17. The spiral nebulae M51 in 1910 . . . . . . . . . . . . . . . . . . . Hubble-Reynolds diagram of the local Universe . . . . . . . . . . . Example of a galaxy velocity field . . . . . . . . . . . . . . . . . . Hubble-Reynolds diagram of distant galaxies . . . . . . . . . . . . Morphology as a function of redshift and stellar mass . . . . . . . . The main sequence of galaxies . . . . . . . . . . . . . . . . . . . . The history of star formation . . . . . . . . . . . . . . . . . . . . . Velocity fields of the KROSS sample . . . . . . . . . . . . . . . . . Rotation-dominated galaxy fraction evolution with redshift . . . . . Velocity dispersion evolution with redshift . . . . . . . . . . . . . . Stability ratio evolution with redshift . . . . . . . . . . . . . . . . . Tully-Fisher relation at high redshift . . . . . . . . . . . . . . . . . Mass growth of galaxies with time. . . . . . . . . . . . . . . . . . . Rotation-dominated fraction evolution with stellar mass and redshift Evolution of the velocity dispersion with redshift and stellar mass . . Illustration of gravitational lensing . . . . . . . . . . . . . . . . . . Kinematics of a strongly lensed galaxy . . . . . . . . . . . . . . . .. . . . . . . . . . . . . . . . . .. . . . . . . . . . . . . . . . . .. 3 5 6 11 12 13 14 16 18 19 20 24 26 27 28 28 29. 2.1 2.2 2.3 2.4 2.5. Example of a dendogram . . . . . . . . . . . . The multi-objects spectrograph KMOS . . . . Velocity field models . . . . . . . . . . . . . . Beam-smearing effect on the velocity dispersion Morpho-kinematic decision tree . . . . . . . .. . . . . .. . . . . .. . . . . .. . . . . .. . . . . .. . . . . .. . . . . .. . . . . .. . . . . .. 35 40 42 44 47. 4.1 4.2 4.3 4.4 4.5 4.6 4.7 4.8. KLENS - Galaxy from A2744 and RXJ1347 . . . . . . . First results from KLASS . . . . . . . . . . . . . . . . . Histograms of the main properties of the KLASS sample Velocity dispersion comparison . . . . . . . . . . . . . . Tully-Fisher relation from KLASS . . . . . . . . . . . . Evolution of the velocity dispersion with redshift . . . . Evolution of the velocity dispersion with stellar mass . . Evolution of the stability ratio with stellar mass . . . . .. . . . . . . . .. . . . . . . . .. . . . . . . . .. . . . . . . . .. . . . . . . . .. . . . . . . . .. . . . . . . . .. . . . . . . . .. 83 84 90 94 97 98 100 101. xvii. . . . . .. . . . . .. . . . . .. . . . . ..

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(20) Chapter. 1. Introduction The kinematics of distant galaxies is the main subject of this thesis. Astronomers have studied the nearby galaxies present in the local Universe and our own Galaxy, the Milky Way, for over a century. We have been able only recently to observe distant galaxies that have existed more than 5 billions years ago. This chapter will summarise the first observations of galaxies and the discovery of their rotational motion. I will then describe the global properties and kinematics of nearby and distant galaxies.. 1.1 1.1.1. A brief history of galaxies Discovery of the galaxies. For thousands of years, people have been observing the Milky Way with their naked eyes. Already over 2000 years ago, philosophers and scientists such as Democritus and Aristotle suggested that the bright white band visible in the sky at night could be due to stars clustering together. Later in the 10th century, Abd al-Rahman al-Sufi, a Persian astronomer, recorded for the first time observations of objects outside our Galaxy. He mentioned Andromeda, the closest galaxy to the Milky Way, and the Large Magellanic Cloud, a dwarf galaxy orbiting around the Milky Way, in his book named Book of Fixed Stars. However, the nature of these objects was still not well understood. The invention of telescopes and further advances in instrumentation, hundreds of years later, finally allowed astronomers to study in detail these diffuse objects visible on the sky, named nebulae at the time, but now called galaxies. 1.

(21) 2. Chapter 1. Introduction. The Milky Way was observed for the first time with a telescope by Galilei in 1610. Galilei was able to see that the Milky Way was made up of many stars. Following this invention, other astronomers such as Messier used small telescopes (∼ 4 inches) to look at the sky. Messier was interested in observing comets. However, he found that many bright and diffuse objects looked similar. To not confuse them with the comets, he published a list of these nebulae in 1771 and 1781. This list is now known as the Messier Catalogue. In 1845, an astronomer named Parsons used the biggest telescope in the world at the time, a telescope with a 72-inch mirror, to observe the M51 nebula. He observed for the first time a spiral shape (Parsons 1926). He detected more than a dozen spiral nebulae in the following years. Figure 1.1 shows an image of the M51 spiral nebula, but taken years later, in 1910 by the astronomer Ritchey. Parsons, with his assistant Dreyer, started to catalogue these objects in the New General Catalogue (NGC) of Nebula and Star Clusters, a catalogue still used today. Ritchey observed at Mount Wilson with the Hooker telescope (100-inch mirror) a nova, a new star that was not present in previous observations, in a spiral nebula. At the same time, Curtis also observed similar objects at the Lick observatory, and he noticed that the magnitude of these objects was about 5.5 in the Milky Way, but more than 10 magnitude fainter in the spiral nebulae. He suggested that if these novae were the same type of star, the novae in the spiral nebulae should be 100 times farther away than the novae in the Milky Way. Shapley estimated a distance of a million light years for the Andromeda nebula, but later rejected the idea of these spiral nebulae being extragalactic objects. His main argument was based on Van Maanen’s measurement of the rotation in M101. The nature of these spiral nebulae was unclear. Astronomers were not sure if these objects were part or not of the Milky Way. This question led to an important event in 1920: the Shapley-Curtis debate, or Great debate. The subject of this debate was the nature of the spiral nebulae and the size of the Universe. Shapley was convinced that the spiral nebulae were inside the Milky Way while Curtis was arguing that they were extragalatic objects, and similar objects to the Milky Way evolving by themselves far away from us. After the debate, other scientists were able to verify the different measurements. It was found that the rotation measurements from Van Maanen were wrong, and scientists finally agreed with Curtis arguments. The final proof in favour of the Curtis theory was the work of Hubble on cepheids. Cepheids are a type of stars with a luminosity that varies or pulsates. The measurements from Hubble of Andromeda with the Hooker telescope allowed him to derive their distances. He found that this galaxy was at least 10 times farther away than the stars observed in the Milky Way. Therefore the idea that other independent galaxies, similar to the Milky Way, existed was finally accepted. For the first time, the Universe was seen as something much bigger than our Galaxy..

(22) 1.1. A brief history of galaxies. 3. Figure 1.1: M51 spiral nebula photographed in February 1910 by Ritchey with the 60-inch reflecting telescope of the Mount Wilson. From Ritchey (1910).. 1.1.2. First kinematic measurements. After the discovery of spiral nebulae, astronomers thought that the spiral shape was due to the rotation of the nebulae on itself. The first evidence of rotation from spectroscopic data were made by Slipher in 1912 (Brémond 2009). Slipher (1914) and Wolf (1914) observed that the absorption lines in the nuclear spectra of nearby galaxies were inclined. Slipher concluded that it was a direct evidence of a rotational motion. Following these observations, Pease (1918) confirmed this result observing the nuclear region of Andromeda. He found a velocity of 58 km s−1 at 2’ from the.

(23) 4. Chapter 1. Introduction. center. He also derived a linear relation between the velocity and distance from the center. Already in the 1940s, Oort (1940), who was also studying the rotation of galaxies, noticed a discrepancy between the distribution of mass and light, with a very high ratio of mass to light in the outer region of the galaxy NGC 3115. More than a decade later, it was finally possible to measure rotation curves with Hα and [NII] emission lines tracing the ionized gas (Page 1952; Burbidge & Burbidge 1960) and using radio observations that trace the neutral hydrogen, HI, (e.g. van de Hulst et al. 1957; Volders 1959; Argyle 1965), allowing to probe rotation curves more easily in the outer region of galaxies. One of the first astronomers to confirm that some galaxies were actually showing flat rotation curves in their outer region was Albert Bosma in the 1970s (e.g. Bosma & van der Kruit 1979). Vera Rubin also studied the rotation curves of edge-on galaxies starting in the late 1960s, but the results were only published in 1980. The presence of flat rotation curves suggested that either the law of gravity was wrong or that a large fraction of the mass was undetected in a dark galactic halo (e.g. Rubin 1983). Later in 1990, it was finally possible to study the rotation curves from CO observations tracing the molecular gas (e.g. Sofue 1996, 1997).. 1.2. The nearby galaxies. Nearby galaxies have been studied extensively because of their proximity. They represent present-day galaxies, where the cosmic evolution effects are negligible. This section will describe the global properties and the kinematics of these nearby galaxies.. 1.2.1. Global properties of nearby galaxies. Several types of galaxies are present in the local Universe: spiral, elliptical, spheroidal, irregular, dwarf, in interactions, etc. To better understand their origin, different systems of classification have been developed. These systems divide the galaxies according to their morphology, mostly in the visible. The Hubble-Reynolds classification, for example, splits the galaxies first between the spirals, ellipticals, spheoridals and irregulars (or peculiars), but also in sub-categories according to their type of spiral arms and bars, in the case of spiral galaxies, or ellipticity, for elliptical galaxies (Reynolds 1920; Hubble 1926). Fig. 1.2 presents the Hubble-Reynolds classification, with two branches for the barred and unbarred galaxies. Spirals or disky galaxies, also called late-type galaxies, represent a total of ∼ 75% of the galaxies in the local Universe (Conselice 2006). They have a disk shape and they can be distinguished by their large fraction of gas and dust, which.

(24) 1.2. The nearby galaxies. 5. Figure 1.2: Hubble-Reynolds sequence of the local Universe. The elliptical, spheroidal, spiral and peculiar galaxies represent ∼ 3%, ∼ 15%, ∼ 72% and ∼ 10% of the local galaxies, respectively. The diagram has two branches: the top one presents the spirals with no bar, and the bottom one the spirals with a bar. Credit : NASA, ESA, Sloan Digital Sky Survey, R. Delgado-Serrano & F. Hammer (Observatoire de Paris).. often leads to star formation. Stellar formation can be observed in HII regions, regions where the gas is ionised by hot and young stars of O and B types that also give a blue color to these galaxies. The average star formation rate (SFR) in spiral galaxies varies between 1 and 2 M yr−1 (Bauer et al. 2005). Spiral galaxies can also host starbursts, regions where the SFR can reach 10 to 100 M yr−1 (Dopita et al. 2002) and decreases after a couple of millions year. Spiral arms also play an important role in the star formation of a galaxy since they host large molecular clouds, dense regions where stars are created (Lin & Shu 1964). HII regions are therefore numerous and the massive stars in these regions cause the high luminosity of the arms. Two third of the spiral galaxies have a bar (de Vaucouleurs 1963). A bar can bring gas to the center and be responsible for increases in star formation (Combes 2006). The center of spiral galaxies is often a superposition of different structures such as a bar, disk and bulge. The bulge, often compared to an elliptical galaxy, presents old stellar populations. The center of a galaxy can also host an active galactic nucleus (AGN). These AGN can eject a large amount of energy and ionise their surrounding. This ionisation, different from the ionisation by the HII regions, also shows different spectral signatures (Osterbrock & Ferland 2006)..

(25) 6. Chapter 1. Introduction. Figure 1.3: XDSS blue band image (left panel) and Hα velocity field (right panel) of UGC 7154, a galaxy from the GHASP survey. The black line indicates the kinematic major axis. From Epinat et al. (2008a).. Ellipticals and spheroidals represent ∼ 20% of the galaxies in the local Universe (Conselice 2006). These galaxies, also called early type, have an ellipsoidal shape and are divided in the Hubble-Reynolds classification according to the ratio between their major and minor axis. They are mainly composed of old stellar populations with low-mass stars, which give them a red colour. The fraction of gas and dust is very low compared to the spiral galaxies and there is no, or relatively low, star formation. It is believed that they are the result of galaxy interactions or mergers of spiral galaxies that occurred at early time. Irregular or peculiar galaxies represent < 5% of galaxies in the local Universe according to Conselice (2006). They are most of the time relatively small and contain a lot of gas and dust. They often experience a starburst, with active star formation and do not have any regular structure. Irregular galaxies are most likely formed by gravitational interactions and through mergers of galaxies.. 1.2.2. Kinematic properties of nearby galaxies. Several surveys have focused on nearby galaxies. There are many objectives : to put constrains on the mass distribution and properties of the dark matter halo; to understand the role of feedback, environment, inflows and outflows on star formation and galaxy evolution; to study the nature of shocks, random motions and the small-scale dynamics of the interstellar medium; or even to look at the stellar populations and metallicity distribution to have insight into the star formation histories of galaxies. Here I will focus on surveys that used the kinematics of mainly spiral galaxies to answer to these questions. The kinematics can be observed from the.

(26) 1.2. The nearby galaxies. 7. emission lines of the ionized gas, absorption lines from the stars, 21-cm line from the neutral hydrogen gas (HI), and CO lines from the molecular gas (H2 ) that trace different gas disks. I will first briefly mention some important surveys that provided the kinematics of spiral galaxies and follow with a discussion on their main results. • GHASP: The Gassendi HAlpha survey of SPirals (GHASP) obtained Hα emission lines of ∼ 200 spiral and irregular galaxies with a median mass of log(M?/M ) = 10.6 using Fabry-Perot observations (Epinat et al. 2008a,b). Figure 1.3 shows one galaxy part of their sample that is representing a typical velocity field of a spiral galaxy in the local Universe. • SAMI: The Sydney Australian astronomical observatory Multi-object IntegralField spetrograph (SAMI) is an instrument on the 4 meter of the AngloAustralian Telescope at Siding-Spring Observatory. The goal of the survey was to observe more than 3000 galaxies in different environnements. Using this survey, Bloom et al. (2017) studied the Hα emission lines to obtain the ionized gas kinematics. • THINGS: One of the most important HI surveys is The HI Nearby Galaxy Survey (THINGS; Walter et al. 2008). THINGS is a sample of 34 objects at distances between 3 and 15 Mpc that have been observed at the NRAO Very Large Array (VLA) to detect the 21-cm HI line with an angular resolution of 7” and a spectral resolution of 5 km s−1 . • HERACLES: The HERA CO-Lines Extragalactic Survey (HERACLES) observed the CO emission using the IRAM 30-m telescope (Leroy et al. 2009). Their final sample traces the CO(2-1) of 48 nearby galaxies out to large radii, with an angular resolution of 13” and spectral resolution of 2.6 km s−1 . • CALIFA-EDGE: The Calar Alto Legacy Integral Field Area Survey (CALIFA) observed more than 600 galaxies in the visible (Sánchez et al. 2012). In parallel, the Extragalactic Database for Galaxy Evolution (EDGE-CALIFA) targeted ∼ 100 CALIFA galaxies to study their CO emission (Bolatto et al. 2017) with the E- and D-arrays. 1.2.2.1. Rotation of nearby galaxies. The nature of the gravitational support of a galaxy in equilibrium can be determined by comparing the turbulent motions, probed with the local intrinsic velocity dispersion, σ0 , and the rotational motion probed with the rotation velocity, υrot , which is the rotation velocity reached in the outer regions of a galaxy (see Fig. 1.3). When the rotation velocity is higher than the velocity dispersion, it means that the disk is gravitationally supported by the rotation, but when the intrinsic velocity dispersion is higher, the system is pressure supported. Using the ratio υrot /σ0 as a disk stability diagnostic can therefore give information on the dynamical state of a galaxy..

(27) 8. Chapter 1. Introduction. An important result from these surveys is that all nearby spiral galaxies have a rotating disk, meaning that they show a velocity gradient in their velocity field. They are also dominated by the rotation with υrot /σ0 > 1. In the GHASP survey, they found a rotation-dominated fraction of 100% (Epinat et al. 2008a,b). Figure 1.3 presents a typical rotation-dominated galaxy, with a clear velocity gradient in the velocity map. They also obtained a mean stability ratio of υrot /σ0 ∼ 13. Similar values were found by other surveys in the local Universe and indicate that the nearby galaxies are dominated by rotation and dynamically stable. Even if the spirals are rotating, several present asymmetries in their velocity field. For example, they found in the SAMI survey an asymmetry in ∼ 23% of their sub-sample of 360 rotating galaxies, where they identified the remaining ∼ 77% as kinematically normal (Bloom et al. 2017). They also showed that the asymmetries are stronger and more frequent for low-mass galaxies. These asymmetries could be due to the concentration of star formation, to the presence of internal structures in the galaxies or to gravitational interactions. The shape of the rotation curves of galaxies can also give information about their content and internal structures. de Blok et al. (2008) using the HI observations from THINGS traced rotation curves out to very large radii, since the HI disk is often more extended than the stellar and ionized gas disks. The shape of the rotation curves is consistent with a curve that rises steeply and flattens out in the outer regions. These results are in good agreement with previous studies on rotation curves (e.g. Rubin et al. 1980), and are direct evidence of dark matter. de Blok et al. (2008) also found that the rotation curves of the low-mass galaxies in their sample rise more slowly and do not always flatten, meaning that the dark matter halo model varies with stellar mass. They also observed in some cases a small decrease in the rotation curve, but never steep enough to explain the observed velocity without the presence of a dark matter halo. Recent studies have also compared the rotation curves with different tracers. Frank et al. (2016) compared the rotation curve in CO (with HERACLES) and HI (with THINGS) and found good agreement between the two with only small differences in the inner part of some galaxies due to a bar or other internal structures. Levy et al. (2018) using the EDGE-CALIFA survey found that ∼ 75% of the galaxies in their sample showed a lower rotation velocity for the ionized gas (Hα) than for the CO. They suggested that it was due to the presence of extraplanar diffuse ionized gas in a thick disk. Therefore, we can wonder if the ionized gas is actually a good tracer of the galaxy dynamics. This could significantly influence results on the dynamical masses used to constrain the fraction and properties of the dark matter for example..

(28) 1.2. The nearby galaxies 1.2.2.2. 9. Velocity dispersion of nearby galaxies. Local galaxies are known to have a thin gas disk where we can find molecular gas, dust and star formation. In the Milky Way, the molecular gas velocity dispersion is between 5 and 10 km s−1 and the scale height of 50 pc (Glazebrook 2013). Tamburro et al. (2009) obtained a mean value of 10 km s−1 at a galactocentric radius of R25 studying the HI velocity dispersion of the THINGS sample . They also found that the velocity dispersion correlates with SFR, which could mean that stellar feedback drives turbulences. Mogotsi et al. (2016) compared the HI velocity dispersion from THINGS with the CO velocity dispersion using the HERACLES survey. They found a value of 7.3±1.7 km s−1 for the CO compared to 11.7±2.3 km s−1 for the HI in the regions where CO is detected. According to this study, this result is evidence that local galaxies have a thin CO disk with a low velocity dispersion and also a fainter diffuse HI disk component with a higher dispersion. The thin stellar disk has a larger scale height (∼ 200 − 500 pc) than the thin gas disk and has a higher velocity dispersion (∼ 20 km s−1 ) since the velocity dispersion increases due to stars that scatter slowly from their orbits when they are aging. Nearby galaxies can also have a thick stellar disk, with older stellar populations and a higher scale height and velocity dispersion. The velocity dispersion of the stellar thick disk of the Milky Way is about ∼ 40 km s−1 (Chiba & Beers 2000; Pasetto et al. 2012). Typical velocity dispersion values in the local Universe for the ionized gas (traced with Hα for example) are between 10-20 km s−1 . For example, Bloom et al. (2017) with GHASP found a ionized gas velocity dispersion between 6 and 23 km s−1 with a mean value of 13 km s−1 . Levy et al. (2018) found intrinsic velocity dispersions of 9 - 19 km/s and 22 - 40 km/s from the CO (molecular gas) and Hγ (ionized gas), respectively, with the CALIFA-EDGE survey, which support the presence of a thick ioinized gas disk. Looking at the velocity dispersion in the SAMI sample, Zhou et al. (2017) found that there was no correlation between the velocity dispersion (from Hα) and the star formation rate surface density. They concluded that the velocity dispersion cannot be only driven by feedback since the majority of their galaxies have a higher velocity dispersion than predictions by feedback-driven models. It is therefore possible that other sources, such as gravity or differential galactic rotation, are responsible for the observed random motions. 1.2.2.3. The Tully-Fisher relation in the local Universe. Scaling relations link together important physical properties that are observed in galaxies. One important relation is the Tully-Fisher, first published by two astronomers named R. B. Tully and J. R. Fisher in 1977 (Tully & Fisher 1977) using radio observations. They found a correlation between the optical luminosity and the.

(29) 10. Chapter 1. Introduction. rotation velocity in spiral galaxies. Originally, Tully & Fisher (1977) used the blue magnitude and the velocity width of the integrated HI line. There is an equivalent empirical relation for elliptical galaxies, the Faber-Jackson relation, that describes the trend between the stellar mass and velocity dispersion. The Tully-Fisher relation was first used to measure distances and absolute magnitude (e.g. Strauss & Willick 1995; Courteau et al. 2000; Masters et al. 2006). More recent studies have found many other uses to this relation since it actually gives a measure of the ratio between the dynamical mass, that includes the baryonic and dark matter, and the stellar mass. Thus, this relation probes the variation of the baryonic to dark matter fraction and can be used, for example, to study the dark matter haloes of galaxies and constrain galaxy formation and evolution models (Dutton et al. 2007; Gnedin et al. 2007; Dutton et al. 2010; Trujillo-Gomez et al. 2011). The Tully-Fisher relation has been re-measured and re-calibrated by many surveys. The GHASP survey for example found a very tight correlation. One important work I want to mention here is the study by Reyes et al. (2011) that used a relatively small sample of ∼ 200 galaxies to obtain the Hα kinematic properties and applied their results to a larger sample of ∼ 170 000 galaxies from SDSS. This work is now used regularly as a reference for the Tully-Fisher in the local Universe in many studies on high-redshift galaxies.. 1.3. The distant galaxies. Distant galaxies are much more difficult to study than nearby galaxies, but with advances in instrumentation, it is now possible to detect galaxies up to z ∼ 10. Deep surveys have allowed us to get observations of large samples of galaxies at high redshift. In this section, I will briefly mention important results about the evolution and properties of these galaxies in the distant Universe. I will then focus on their kinematics by summarizing several large surveys and presenting their main results.. 1.3.1. Global properties of high-redshift galaxies. A key result from the studies of high-redshift galaxies is the evolution of their morphology with time. There is a significant decrease in number of disks and an increase of the irregulars with redshift (Conselice 2014) as shown is Fig. 1.4. When we get to higher redshift, irregular galaxies, also bluer because of their higher SFR, become more frequent (see Fig. 1.5). The evolution of the morphology also depends on the stellar mass. The low-mass galaxies are mainly irregulars at lower redshift (z ∼ 1), when the fraction of irregulars is much lower for the massive ones at this redshift (Mortlock et al. 2013). However, at z ∼ 3, the fraction of irregular galaxies.

(30) 1.3. The distant galaxies. 11. Figure 1.4: Hubble-Reynolds sequence for distant galaxies. The elliptical, spheroidal, spiral and peculiar galaxies represent ∼ 4%, ∼ 13%, ∼ 31% and ∼ 52% of the galaxies at z ∼ 0.7, respectively. The diagram has two branches: the top one presents the spirals with no bar, and the bottom one the spirals with a bar. Credit : NASA, ESA, Sloan Digital Sky Survey, R. Delgado-Serrano & F. Hammer (Observatoire de Paris).. is the same for both low-mass and massive galaxies. Galaxies at z > 1 are observed to be more compact, which means that they have a smaller radius than local galaxies at the same stellar mass (Trujillo et al. 2007; Buitrago et al. 2008). The spiral galaxies are also much more clumpy than what is observed in the local Universe (e.g. Elmegreen & Elmegreen 2005; Elmegreen et al. 2007), meaning that their luminosity profile often differs from a smooth exponential or Sersic profile, but shows several peaks of luminosity from massive star-forming regions present in the disk. These clumps are seen in the stellar component (e.g. Elmegreen & Elmegreen 2005) and in the Hα map (e.g. Genzel et al. 2011; Livermore et al. 2015). These clumps have a higher star formation rate density and are more massive than in the local Universe. Their presence could mean that the star formation was due to different mechanims in the distant Universe. Characterizing these structures could therefore bring information on the evolution of star formation over cosmic time. It is also believed that these clumps could result from the fragmentation of the galaxy disks due to gravitational instabilities since galaxies are more gas-rich and turbulent at high redshift (Dekel et al. 2009). Regions in the disk can collapse into clumps.

(31) 12. Chapter 1. Introduction. Figure 1.5: Fraction of spheroidal types (red triangles), disky types (blue semicircles), peculiar types (black circles) as a function redshift for log(M?/M ) > 10.5 (left panel), 10.25<log(M?/M )<10.5 (middle panel) and log(M?/M )<10.25 (right panel). From Mortlock et al. (2013).. if the disk becomes unstable to gravitational fragmentation, when the strength of gravity is stronger than the dynamical and thermal pressure. It can be described by the Toomre stability criterion, Q: Q=. σ0 κ , πG Σgas. (1.1). where σ0 is the intrinsic velocity dispersion, κ is the epicyclic frequency, Σgas is the gas surface density, and G is the gravitational constant. When Q > 1, the disk is stable since the pressure and rotation dominate over the gravity. When Q < 1, the gravity dominates and the disk is unstable. It is unclear how these clumps evolve after their formation. They could dissipate completely into the galaxy disk or some clumps could even migrate toward the galactic center and evolve into a bulge (Genzel et al. 2011). Another important result is the tight correlation observed between SFR and stellar mass of star-forming galaxies, often referred to as the main sequence of star-forming galaxies (Noeske et al. 2007). The correlation is mostly linear at low masses, meaning that the more massive the galaxy, the more it forms stars. The relation flattens out at higher masses and follows a power law: SF R ∝ M?a,. (1.2). where a ∼0.8-1 (e.g. Daddi et al. 2007; Noeske et al. 2007; Schreiber et al. 2015; Tomczak et al. 2016). This main sequence evolves with redshift, as we can see in Fig. 1.6. It means that for a fixed mass, the SFR increases at higher redshift. The specific star formation of galaxies, sSFR=SFR/M?, is therefore globally higher in the distant.

(32) 1.3. The distant galaxies. 13. Figure 1.6: Star formation rate as a function of stellar mass for different redshift bins. From Tomczak et al. (2016).. universe. However, it is difficult to determine the main sequence at high redshift for galaxies with a lower mass since they are more difficult to detect. To explain the tight correlation between M? and SFR seen in the local Universe and at high redshift, similar processes have to regulate galaxies and keep them on this main sequence. A common model, named the bathtub model, suggests that galaxies are actually systems in equilibrium, self-regulated by the different star formation mechanisms. According to this model, their total gas mass depends only on the accreting gas from the surroundings (inflows), the recycled gas from the star formation, and the gas ejected (outflows). Therefore, a small amount of gas available in a galaxy would lead to low star formation and a large amount of gas available would lead to more intense star formation. This means that galaxy properties such as M? and SFR should not strongly depend on their initial conditions. One of the main results about galaxy evolution, summarized by Madau & Dickinson (2014) is the observation of a peak of the star-formation rate density at z ∼ 2 (Fig.1.7). This means that the average star formation rate density is higher at z ∼ 2.

(33) 14. Chapter 1. Introduction. Figure 1.7: Star formation rate density from FUV+IR rest-frame measurements as a function of redshift. From Madau & Dickinson (2014).. than in the local Universe, and therefore that most of the stars form at this redshift. The clumpy galaxy fraction seems to follow a similar trend with a peak observed at the same redshift (z ∼ 1.5 − 2), meaning that the clump formation and star formation are strongly correlated (Shibuya et al. 2016). Therefore, the clumps are an indirect way to study the disk formation history. However, it is still unclear how these galaxies assembled and what sustained the intense star formation at this epoch, but several scenarios have been suggested. For example, a higher merger rate could drive more quiescent galaxies into burst of star formation (e.g. Conselice et al. 2003; Hammer et al. 2009; Conselice et al. 2009; Bluck et al. 2009; Man et al. 2012) or a higher gas accretion rate could lead to higher gas densities and SFR (Dekel et al. 2009; Conselice et al. 2013). These different results together give us a general picture of the distant Universe where the galaxies are highly star-forming and gas-rich with a more compact irregular and clumpy morphology. This can be interpreted as galaxies that are starting to build their disk and stabilized while also converting their gas reservoir into stars to become the local spiral galaxies we observe around us. We can now wonder if their.

(34) 1.3. The distant galaxies. 15. kinematics agree with this picture and if the kinematic properties can bring insights on their rapid evolution.. 1.3.2. Kinematic properties of high-redshift galaxies. The kinematics of star-forming galaxies at z ∼ 2, when the SFR rate density is at its peak, can give key information on their fundamental properties. It can also allow us to establish the dynamical state, stability and turbulent motions of these galaxies in order to learn more about the formation and evolution of these early systems that are believed to evolve into the regular spiral galaxies observed in the local Universe. Early studies at high-redshift used long-slit spectroscopy and allowed us to study only the integrated spectrum (Glazebrook et al. 1995; Lilly et al. 1995), and integrated velocity dispersion (Koo et al. 1995; Forbes et al. 1996). Using the Keck telescope, Vogt et al. (1996) obtained rotation curves for galaxies at 0.1 < z < 1 and found that galaxies at these redshifts show similar kinematics as the ones in the local Universe, meaning that galaxy disks were already formed at this epoch. However, it was also found that a large fraction does not show a rotating disk (∼ 25 − 30% Simard & Pritchet 1998; Ziegler et al. 2002; Böhm et al. 2004). First studies at z > 2 were on the velocity dispersion of Lyman Break Galaxies and UV-selected objects by Pettini et al. (1998, 2001) and Erb et al. (2006), respectively. They also determined the rotation curves for several of these galaxies. 1.3.2.1. Recent surveys. Integral field spectrographs (IFS) provide spatial and spectral information simultaneously, allowing us to map the galaxy kinematics (see Fig. 1.8). In this section, I will present a summary of several large IFS surveys that were performed in the past years. Most of these surveys observed the emission lines from the ionized gas, such as Hα and [OIII] that are redshifted to the near-infrared. Other tracers are more difficult to observe at high redshift, however, some studies reported CO (e.g. Calistro Rivera & Hodge 2018) and stellar kinematics of several galaxies (e.g. Guérou et al. 2017), but the HI line is still impossible to detect. The [CII] line was also used to get the kinematics at higher redshift (z > 4) (e.g. Matthee et al. 2017; Smit et al. 2018). • SINS: The SINS survey used SINFONI/VLT to observe the Hα emission line of 80 galaxies at z ∼ 1−3 with a median log(M?/M )=10.6 (Förster Schreiber et al. 2009). They observed a velocity gradient typical of rotating galaxies in the majority of their objects. More precisely, they found a rotation-dominated fraction of 33%, a dispersion-dominated fraction of 33%, meaning that a velocity gradient is seen in the velocity field, but that the dispersion is higher.

(35) 16. Chapter 1. Introduction. Figure 1.8: Star formation rate as a function of stellar mass for 584 galaxies of the KROSS sample. Each point represents the velocity field of the galaxy. From Stott et al. (2016).. than the rotation velocity, and a fraction of galaxies in interactions of 33% (Förster Schreiber et al. 2006, 2009). Their galaxies also show a turbulent disk with a high velocity dispersion and a relatively low stability ratios of 2 < υrot /σ0 < 4. They also studied the morphology and observed that the disks are different than in the local Universe for similar mass. They found that the Hα morphologies of their galaxies are clumpy, with kpc-scale clumps. This clumpiness is also seen in the UV, and the near-IR continuum (Förster Schreiber et al. 2011). They also observed a sub-sample with adaptive optics (AO) to get to a spatial resolution of 0.1” (Cresci et al. 2009). They got for this sub-sample of massive galaxies a velocity dispersion between 40-80 km s−1 . • MASSIV: The Mass Assembly Survey with SINFONI (MASSIV) observed 84 galaxies at 0.9 < z < 1.8, including 11 with AO (Contini et al. 2012). Epinat et al. (2009) and Epinat et al. (2012) presented an analysis of the kinematics. They found that 44% of their galaxies are rotators and 35% are.

(36) 1.3. The distant galaxies. 17. non rotators, while the remaining galaxies were not classified due to low signal-to-noise ratios. They found that 29% of their galaxies are mergers or in interactions, some of them being also rotators. The typical velocity dispersion in their sample is ∼60 km s−1 , with similar velocity dispersion for rotators and non rotators. The non rotators also show an anti-correlation between the size and velocity dispersion. • KMOS3D : The KMOS3D survey targeted more than 600 galaxies at 0.7 < z < 2.7 using KMOS/VLT. From their first sample of ∼ 200 galaxies with masses of 9.5 <log(M?/M ) < 11.8, they obtained that 83% of their resolved galaxies are rotation-dominated (Wisnioski et al. 2015). They also found a high dispersion of 50 km s−1 for their sample at z ∼ 2.3 and 25 km s−1 for their sample at z ∼ 0.9. They showed that this dispersion follows an evolution that is consistent with a velocity dispersion depending on the gas fraction predicted by a marginally stable disk theory (see Sect 1.3.2.2). Wisnioski et al. (2018) studied the kinematics of compact massive objects and obtained a similar fraction of rotation-dominated galaxies as the full sample. • KROSS: The KMOS Redshift One Spectroscopic Survey (KROSS) is a survey that observed 795 star-forming galaxies between 0.8 < z < 1.0 with KMOS/VLT. They obtained the kinematics of 584 galaxies, as presented in Fig. 1.8 (Stott et al. 2016). They found a fraction of rotation-dominated galaxies of 83% and concluded that the disk is more turbulent with a high gas to baryonic mass fraction. They did not find a strong correlation between the velocity dispersion and SFR. They concluded that the feedback from stars were not the cause of the high dispersion. Johnson et al. (2018) studied in more detail the cause of the high dispersion and the effect of the beam smearing in this sample (see Chap. 2). They obtained a median intrinsic velocity dispersion of 43.2 ± 0.8 km s−1 and a ratio of υrot /σ0 = 2.6 ± 0.1. When combining their data to the SAMI survey and MUSE observations (z ∼ 0.5), they obtained a weak trend between velocity dispersion and stellar mass. At fixed mass, they found a strong increase of the dispersion with redshift. They also obtained a weak trend between the dispersion and SFR. Finally, Harrison et al. (2017) studied the rotation velocities and angular momentum and found an evolution of the angular momentum with redshift. • MUSE/KMOS: Swinbank et al. (2017) studied 405 galaxies from MUSE and KMOS observations at 0.28 < z < 1.65 (median of 0.84), with 0.1<SFR [M yr−1 ]<30 and 8<log(M?/M )<11. They found that 49 ± 4% of their sample is rotating, 24±3% is unresolved, 5 ± 2% is a merger, and 22 ± 5% has a complex or irregular kinematics. They obtained an evolution of the specific angular momentum with redshift and a correlation between the specific angular momentum and the disk stability, with a higher angular momentum for the.

(37) 18. Chapter 1. Introduction. Figure 1.9: Rotation-dominated galaxy fraction as a function of redshift. The mean stellar masses (log(M?/M )) of each survey is indicated next to the name of each survey. From Turner et al. (2017a).. most stable galaxy. Looking at the morphologies, they also found that the galaxies with the highest angular momentum look like spiral galaxies, and the galaxies with a low angular momentum have more complex and clumpy morphology, with an unstable disk. • Other: Many other surveys have been performed, for example, AMAZE/LSD (Gnerucci et al. 2011), DEEP2 (Kassin et al. 2012), DYNAMO (Green et al. 2014), PHIBSS (Tacconi et al. 2013) , IMAGES (Yang et al. 2008; Neichel et al. 2008), and OSIRIS (Law et al. 2009).. 1.3.2.2. Main results from the surveys. Despite different kinematic classifications, sample selections and modelling methods, there are some general trends and results for which all the previous surveys agree..

(38) 1.3. The distant galaxies. 19. Figure 1.10: Velocity dispersion as a function of redshift. From Wisnioski et al. (2015).. First of all, as found by the first studies before using IFS data, there are still a lot of galaxies rotating at high redshift (1 < z < 3). Different fractions of rotationdominated galaxies are found, but this fraction seems to decrease with the redshift, as shown in Fig. 1.9. Swinbank et al. (2017) suggested that it could be due to the low specific angular momentum of these systems. These rotating galaxies have, however, a different morphology and properties than the local ones. They are more clumpy, more compact and they have a higher SFR. Indeed, the fraction of rotationdominated galaxies is higher than the fraction of galaxies with a disky morphology at the same redshift (Fig. 1.5), which means that many clumpy galaxies show a rotating disk. We can also wonder if this rotation-dominated fraction depends on other galaxy properties such as the stellar mass and SFR and if there is a link between the morphology of these galaxies and their dynamical stability. These distant galaxies have a high velocity dispersion with values between ∼ 40 − 70 km s−1 on average (e.g. Förster Schreiber et al. 2009; Epinat et al. 2009; Wisnioski et al. 2015; Swinbank et al. 2017; Johnson et al. 2018). These high velocity dispersions lead to a large fraction of dispersion-dominated galaxies at z > 1, with υrot /σ0 < 1. The galactic disks are therefore more turbulent and.

(39) 20. Chapter 1. Introduction. Figure 1.11: Stability ratio, υr ot /σ0 , as a function of redshift. From Wisnioski et al. (2015).. unstable at high redshift than in local galaxies. We can now wonder what causes these high velocity dispersions and turbulent motions. The higher molecular gas fraction, f gas , observed at high redshift has been suggested as the cause of the high dispersion. Wisnioski et al. (2015) derived a relation of the velocity dispersion as a function of redshift using the evolution of the molecular gas fraction in the framework of the equilibrium (or bathtub) model. Using the Toomre stability criterion (Toomre 1964), they can get the following relation : Q=. 2 R σ0 κ σ0 a Mtot σ0 a (υrot σ0 a disk /G) = = = . 2 πG Σgas υrot (πRdisk υrot Mgas υrot f gas Σgas ). (1.3). √ where a = 2 for a constant rotation velocity of a disk and the epicyclic frequency is 2 /R2 2 κ 2 = 4υrot disk + Rdisk d(υrot /Rdisk ) /dRdisk (e.g. Dekel et al. 2009; Genzel et al. 2011). By re-arranging the equation they obtained:.

(40) 21. 1.3. The distant galaxies. υrot f gas (M?, z) Q , (1.4) a where Q = 1 for a quasi-stable thin gas disk (Förster Schreiber et al. 2006; Genzel et al. 2011). For a thick gas disk, the value of a quasi-stable disk is Q = 0.67, and for a stellar and gas disk, we expect a higher value, typically 1 − 2 times higher. They described the gas fraction as σ0 (M?, z) =. f gas =. Mgas 1 = , Mgas + M? 1 + (t dep sSFR) −1. (1.5). where the depletion time is defined as t dep = Mgas /SFR and the specific star formation rate as sSFR=SFR/M?. The depletion time is found observationally to vary with redshift as t dep [Gyr] = 1.5 × (1 + z) α,. (1.6). sSF R = 10a × (1 + z) b,. (1.7). where α can vary between -0.7 to -1.0 from observations (Tacconi et al. 2013). The specific star formation rate relation as a function of redshift can be obtained from observations when studying the evolution of the main sequence with redshift. In the work of Wisnioski et al. (2015), they used the relation from Whitaker et al. (2014) which is valid for log(M?/M )=9.2-11.2 :. with. 1.26. , (1.8) 1 + e (10.49−logM? )/(−0.25) 1.57 b = 1.85 + . (1.9) (10.35−logM ? )/(0.19) 1+e The relation obtained from this equation by Wisnioski et al. (2015) is presented in Fig. 1.10. The velocity dispersion increases with redshift and is consistent with the mean values obtained in several surveys. We can also look at the evolution of the dynamical state with the stability ratio as a function of redshift from the same equation (see Fig. 1.11). The stability ratio decreases with redshift, meaning that galaxies are more dynamically unstable at high redshift, which follows the idea of the decrease of rotation-dominated galaxy fraction with redshift. Other explanations have been suggested to explain the high velocity dispersion, such as interactions between clumps (Dekel et al. 2009), disk instabilities (Ceverino et al. 2010; Bournaud et al. 2014), and minor mergers (Bournaud et al. 2009). Turbulence due to the feedback from stars have also been suggested, but only a weak trend has been reported between the velocity dispersion and star formation rate. Johnson et al. (2018) found that both feedback-driven and gravity-driven models a = −10.73 +.

(41) 22. Chapter 1. Introduction. predict turbulence that is consistent with the observations. Moreover, Newman et al. (2013) found that the spatial resolution can bias the results toward higher dispersions. According to this study, gaining in spatial resolution decreases the fraction of dispersion-dominated galaxies. However, when taking this effect into account, there is still a relatively large fraction of dispersion-dominated galaxies at z > 1. They suggested that these pressure supported objects could be transient structures or objects that are not in equilibrium. Observations at high resolution also showed that the velocity fields of distant galaxies often present asymmetries. Hammer et al. (2009) found that 41% of their galaxies show anomalous kinematics, which is higher than in the local Universe. They concluded that major mergers can reproduce peculiar morphology and anomalous kinematics, since two disks can either merge together and become an elliptical galaxy (e.g. Hernquist 1992), or result in a new disk (e.g. Hammer et al. 2005; Hopkins et al. 2008; Hammer et al. 2009). It is, however, difficult to establish a merger rate using the velocity maps of high-redshift galaxies, since their kinematics can often show rotation even if the morphology looks like a merger. The data are also not deep enough to see well the outskirts of the galaxies. Surveys such as AMAZE (z ∼ 3.5), MASSIV (z ∼ 1.3), SINS (z ∼ 2) and Hammer et al. (2009, z ∼ 0.65) found a major merger fraction of ∼ 30%. Swinbank et al. (2017) obtained a major merger fraction of less than 5% for a sample at 0.28 < z < 1.65. These fractions seem to depend a lot of the criteria chosen to classify a galaxy with anomalous or regular kinematics (see Chap. 2). Simons et al. (2019) also pointed out that the merger rate could be under-estimated due to the lack of spatial resolution and that we are not probing the outskirts of galaxies well enough. They found that the disk fraction could be overestimated by 5-15% depending on the stellar mass. Mergers might therefore play a more important role at these redshift than what is currently seen. I also want quickly to mention without going into too much detail that these recent large surveys have also started looking at the profile of the rotation curves at high redshift to infer the dark matter fraction and distribution over the galaxies. Lang et al. (2017) and Genzel et al. (2017) found that the rotation curves in their galaxy sample are falling in the outer regions. They concluded that the dark matter fraction is very low in the internal part of these galaxies and that they could therefore be baryon-dominated. However, Tiley et al. (2018) found flat rotation curves for the same sample and concluded differently. The evolution of the dark matter fraction is therefore still unclear at high redsfhit. Deep observations are needed to get rotation curves of individual galaxies out to large radii. To summarize this section, galaxies at high redshift appear to be more clumpy, gas-rich and highly star-forming, with a disk that is less dynamically stable and more turbulent. They are in many cases dominated by the dispersion and their.

(42) 1.3. The distant galaxies. 23. velocity field is often disturbed. The interactions between galaxies are also more frequent. However, several questions remain: is there any link between their clumpy morphology and their kinematics? What are the mechanisms behind this high velocity dispersion? And do the kinematics also depend on other galaxy properties such as their mass and SFR? Do we miss important information by not probing well the outskirts of the galaxies? 1.3.2.3. The Tully-Fisher relation at high redshift. The Tully-Fisher relation has also been studied at higher redshift to establish if an evolution of this relation exists with redshift. An evolution would indicate a change in the dynamical to stellar mass ratio, giving information on when and how the gas mass was converted into stars, but also on the variation of the baryonic to dark matter fraction. Different results have been reported from recent surveys, but these results are not always consistent. Already with long-slit spectroscopy survey, Vogt et al. (1996) found that galaxies at 0.15 < z < 1 seem to follow a Tully-Fisher relation with only a small offset from the Tully-Fisher observed in the local Universe. Similarly, Harrison et al. (2017), with the KROSS sample at z ∼ 0.9, found a good agreement of the slope and normalisation with local galaxies. At similar redshifts, Ziegler et al. (2002) and Böhm et al. (2004) also obtained only a very small evolution with redshift for massive galaxies, but a strong evolution for low-mass galaxies for a sample of 113 galaxies observed with FORS2/VLT. Simons et al. (2015, 2016) found that the lowmass galaxies (log(M?/M ) < 9.5) in a sample at 0.1 < z < 0.375 are really scattered and do not see a tight relation. Recent surveys also allowed us to study the Tully-Fisher at z > 1. For example, Christensen & Hjorth (2017) with a sample at 0 < z < 3 and with stellar mass of 7.0<log(M?/M )<11.5 found a power-law slope and normalisation independent of the redshift, but they reported a break with a steeper slope for low-mass galaxies. Straatman et al. (2017) obtained a negative evolution for their sample at z ∼ 2 − 2.5. Similarly, Übler et al. (2017) found for their massive galaxies a negative evolution between a sample at z = 0 and z = 0.9, but no evolution between z = 0.9 and z = 2.3. The evolution of the slope and zero point is unclear, however, all these high redshift studies found that the scatter around the Tully-Fisher relation is much higher than in the local Universe. A negative offset of the Tully-Fisher, as seen in Fig. 1.12 (top panel) can be explained by the increase of pressure support at high redshift, which can be interpreted as an increase of velocity dispersion to the detriment of the rotation velocity (Burkert et al. 2010; Simons et al. 2017). For the galaxies with a high stability ratio υrot /σ0 > 3, strongly dominated by rotation, the effect.

(43) 24. Chapter 1. Introduction. Figure 1.12: Tully-Fisher relation at high redshift. Top : Rotation velocity of galaxies as q 2 a function of stellar mass. Bottom: Total velocity, Vtot = υr ot + 4σ02 , as a function of stellar mass. The dispersion-dominated galaxies are in red and the rotation-dominated are in blue. The blue and red contours represent the density of the KROSS sample (Harrison et al. 2017) starting at 10 and increasing in increments of 10 and 3, respectively. From Turner et al. (2017b)..

(44) 25. 1.3. The distant galaxies. due to turbulent motions is negligible. For galaxies with a lower stability ratio, the dispersion should also be taken into account to estimate the dynamical mass. For resolved galaxies, when the intrinsic velocity dispersion is available, a total velocity, Vtot , can be derived by correcting for the asymmetric drift to take into account the pressure support in the galaxies (e.g. Epinat et al. 2009; Burkert et al. 2010; Newman et al. 2013): r. R × σ02, (1.10) Rd where Rd is the disk scale length. A value of 2R/Rd = 4 has been used in the work of Turner et al. (2017b), similar to 3.4 derived for an exponential mass distribution at a radius R = Re , where Re is the effective radius and equals to 1.7 × Rd (Burkert et al. 2010; Newman et al. 2013; Price et al. 2019). Kassin et al. (2007) suggested a slightly different version of this total velocity using the integrated velocity dispersion, σint , which is measured from the integrated spectrum of a galaxy: q 2 + σ2 . S0.5 = 0.5υrot (1.11) int Vtot =. 2 +2 υrot. These relations give impressive results by reducing considerably the scatter around the Tully-Fisher due to the dispersion-dominated galaxies. Figure 1.12 shows an example of the Tully-Fisher relation using the rotation velocity and the total velocity of the KDS sample (Turner et al. 2017b). They found, using this total velocity, a positive offset. It could be due to a decrease of the stellar mass to gas mass ratio and an increase of the baryonic to dark matter fraction with redshift, or also to the gas mass converting to stellar mass at a constant rate. However, it is still unclear why a disagreement between the different studies is observed and why a larger scatter is found compared to galaxies in the local Universe even when using the total velocity to trace the dynamical mass of galaxies.. 1.3.3. Kinematics of low-mass galaxies. Several large infrared surveys have observed galaxies around z ∼ 2, for example, MASSIV, KMOS3D and SINS. These studies have revolutionised our understanding of high-redshift galaxies, but the picture is still incomplete since these surveys have mostly observed massive galaxies with log(M?/M )>10 and high luminosity (SFR> 30 M yr−1 ). Low-mass galaxies, typically with stellar masses of log(M?/M ) <10, are more numerous at this epoch and are also very interesting to study since they are the progenitors of the Milky Way. Indeed, local Milky Way type galaxies with stellar mass of log(M?/M )=10-11 and a halo mass of log(Mh /M )∼12 are expected to have a stellar mass of log(M?/M )∼ 9.5 around z ∼ 2 as seen in Fig. 1.13 (Behroozi et al. 2013). We can now consider if the results found for massive galaxies, such as.

(45) 26. Chapter 1. Introduction. Figure 1.13: Mass growth of galaxies as a function of redshift. The different colors represent different halo masses. From Behroozi et al. (2013).. a decrease of the rotation-dominated fraction with redshift and the evolution of the velocity dispersion with redshift, are still valid for these low-mass galaxies. A few recent studies have explored the kinematics of star-forming galaxies at z > 0.5 in this new parameter space of low SFR and low stellar mass. I will present here a brief summary of the main work on low-mass galaxies that has been done so far. 1.3.3.1. Previous surveys on low-mass galaxies at z > 0.5. Low-mass galaxies have been observed using gravitational lensing (see next section) and direct observations (Gnerucci et al. 2011; Kassin et al. 2012; Contini et al. 2016; Simons et al. 2016, 2017; Swinbank et al. 2017; Turner et al. 2017a). Kassin et al. (2012) reported, using the DEEP2, survey that the most massive systems at z ∼ 1 show a more settled disk than the low mass ones, at all times. Similarly, Simons et al. (2016) found that massive galaxies at z ∼ 2 are mostly rotation-dominated, and showing marginally stable disks with υrot /σ0 ∼ 2 − 5, while the low-mass galaxies are more often dispersion-dominated. Fig. 1.14 shows.

(46) 1.3. The distant galaxies. 27. Figure 1.14: Fraction of galaxies with υr ot /σ0 > 1 (left panel) and υr ot /σ0 > 3 (right panel) as a function of redshift. The different colors represent different stellar mass bins. From Simons et al. (2017).. that the rotation-dominated fraction decreases with redshift, for all the mass bins, but that the low-mass galaxies always show the lowest rotation-dominated fraction at a fixed redshift. Following this study, Simons et al. (2017) found that the velocity dispersion is independent of stellar mass at all redshift, but they observed an increase with redshift as observed for the massive galaxies. Contini et al. (2016) used the Hubble Deep Field South to investigate low-mass galaxies at 0.2 < z < 1.4. They found that most of their galaxies are rotating disks. They obtained a dispersion-dominated fraction of ∼ 20% and a merger rate of ∼ 30%, which is similar to the results for massive galaxies. They concluded that the dynamics and interactions are not strongly correlated to the stellar mass. Turner et al. (2017a) found with the KDS survey a mean velocity dispersion of ∼ 71 km s−1 for galaxies at z ∼ 3.5 with 9.0<log(M?/M )<10.5. They obtained only 35% of rotation-dominated galaxies. They did not find a trend of the velocity dispersion as a function of the stellar mass as shown in Fig. 1.15 (left). They also argued that the velocity dispersion is increasing with redshift, with lower values for the massive galaxies at each epoch, as presented in Fig. 1.15 (right). 1.3.3.2. Observing low-mass galaxies with gravitational lensing. Studies of distant galaxies are limited to the brightest objects. Our instruments cannot see the smaller and fainter objects. One way to detect fainter objects and to gain in spatial resolution is by using gravitational lensing. Gravitational lensing is the effect of light being curved by the mass. It can happen around planets, stars, galaxies, and star and galaxy clusters. For example, the grav-.

(47) 28. Chapter 1. Introduction. Figure 1.15: Intrinsic velocity dispersion as a function of stellar mass (left panel) and redshift (right panel) from the KDS sample. From Turner et al. (2017a).. Figure 1.16: Representation of gravitational lensing. The light of a galaxy behind a galaxy cluster is bent. Several distorted images of the same galaxy can be observed from Earth. Credit: NASA, ESA & L. Calçada..

(48) 1.3. The distant galaxies. 29. Figure 1.17: Example of a strongly lensed galaxy from the sample of Jones et al. (2010). The top panel shows the multiband image in the image plane. The red line represents the critical line. The bottom panel presents the galaxy reconstructed in the source plane. The broad-band emission is shown on the left, the line intensity at the middle-left, the velocity field at the middle right, and the velocity dispersion on the right. From Jones et al. (2010)..

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