\contentsline {chapter}{\numberline {1}Introduction}{4}
\contentsline {section}{\numberline {1.1}Historical perspective}{4}
\contentsline {section}{\numberline {1.2}Bringing order to the zoo of galaxies}{5}
\contentsline {subsection}{\numberline {1.2.1}Vocabulary}{5}
\contentsline {subsection}{\numberline {1.2.2}Galaxy properties}{7}
\contentsline {section}{\numberline {1.3}Summary}{12}
\contentsline {chapter}{\numberline {2}The discovery of the Milky Way and of other galaxies}{13}
\contentsline {section}{\numberline {2.1}The main observables}{13}
\contentsline {section}{\numberline {2.2}The main players, their measurements, and their mistakes}{16}
\contentsline {subsection}{\numberline {2.2.1}Time-line}{18}
\contentsline {section}{\numberline {2.3}Absorption, scattering and reddening}{20}
\contentsline {section}{\numberline {2.4}Summary}{22}
\contentsline {chapter}{\numberline {3}The modern view of the Milky Way}{23}
\contentsline {section}{\numberline {3.1}New technologies}{23}
\contentsline {subsection}{\numberline {3.1.1}Radio-astronomy}{23}
\contentsline {subsection}{\numberline {3.1.2}Infrared observations}{24}
\contentsline {subsection}{\numberline {3.1.3}Star-counts, again}{25}
\contentsline {section}{\numberline {3.2}The components of the Milky Way}{25}
\contentsline {subsection}{\numberline {3.2.1}The disk}{26}
\contentsline {subsection}{\numberline {3.2.2}The thick disk}{27}
\contentsline {subsection}{\numberline {3.2.3}The bulge}{27}
\contentsline {subsection}{\numberline {3.2.4}The stellar halo}{28}
\contentsline {subsection}{\numberline {3.2.5}The dark matter halo}{29}
\contentsline {section}{\numberline {3.3}Metallicity of stars}{29}
\contentsline {subsection}{\numberline {3.3.1}Galactic Coordinates}{30}
\contentsline {section}{\numberline {3.4}Summary}{33}
\contentsline {chapter}{\numberline {4}The Interstellar Medium}{34}
\contentsline {section}{\numberline {4.1}Interstellar dust}{34}
\contentsline {section}{\numberline {4.2}Interstellar gas}{36}
\contentsline {subsection}{\numberline {4.2.1}Collisional processes}{36}
\contentsline {subsection}{\numberline {4.2.2}Photo-ionisation and HII regions}{37}
\contentsline {subsection}{\numberline {4.2.3}21-cm radiation}{40}
\contentsline {subsection}{\numberline {4.2.4}Other radio-wavelengths}{41}
\contentsline {subsection}{\numberline {4.2.5}The Jeans mass}{41}
\contentsline {section}{\numberline {4.3}Summary}{44}
\contentsline {chapter}{\numberline {5}Dynamics of galactic disks}{45}
\contentsline {section}{\numberline {5.1}Differential rotation}{45}
\contentsline {subsection}{\numberline {5.1.1}Keplerian rotation}{45}
\contentsline {subsection}{\numberline {5.1.2}Oort's constants}{46}
\contentsline {subsection}{\numberline {5.1.3}Rotation curves measured from HI\nobreakspace {}21-cm emission}{49}
\contentsline {section}{\numberline {5.2}Rotation curves and dark matter}{50}
\contentsline {section}{\numberline {5.3}The Oort limit}{51}
\contentsline {section}{\numberline {5.4}Spiral arms}{52}
\contentsline {section}{\numberline {5.5}Summary}{55}
\contentsline {chapter}{\numberline {6}The Dark Halo}{56}
\contentsline {section}{\numberline {6.1}High velocity stars}{56}
\contentsline {subsection}{\numberline {6.1.1}Point mass model}{56}
\contentsline {subsection}{\numberline {6.1.2}Parameters of dark halo}{57}
\contentsline {section}{\numberline {6.2}The Local Group}{58}
\contentsline {subsection}{\numberline {6.2.1}Galaxy population}{58}
\contentsline {subsection}{\numberline {6.2.2}Local Group timing argument}{59}
\contentsline {section}{\numberline {6.3}Summary}{62}
\contentsline {chapter}{\numberline {7}Elliptical galaxies. I }{63}
\contentsline {section}{\numberline {7.1}Luminosity profile}{63}
\contentsline {section}{\numberline {7.2}Stellar populations and ISM}{69}
\contentsline {section}{\numberline {7.3}X-rays}{72}
\contentsline {subsection}{\numberline {7.3.1}Thermal bremsstrahlung}{72}
\contentsline {subsubsection}{radiated power}{73}
\contentsline {subsection}{\numberline {7.3.2}Spectrum}{75}
\contentsline {section}{\numberline {7.4}Evidence for dark matter from X-rays}{75}
\contentsline {section}{\numberline {7.5}Summary}{78}
\contentsline {chapter}{\numberline {8}Elliptical galaxies. II}{79}
\contentsline {section}{\numberline {8.1}Relaxation in stellar systems}{80}
\contentsline {section}{\numberline {8.2}Jeans equations}{83}
\contentsline {subsection}{\numberline {8.2.1}A continuity equation}{83}
\contentsline {subsection}{\numberline {8.2.2}Boltzmann's equation}{84}
\contentsline {subsection}{\numberline {8.2.3}Moments of the Boltzmann equation}{86}
\contentsline {section}{\numberline {8.3}Summary}{89}
\contentsline {chapter}{\numberline {9}Groups and clusters of galaxies}{90}
\contentsline {section}{\numberline {9.1}Introduction}{90}
\contentsline {subsection}{\numberline {9.1.1}Evidence for dark matter from galaxy motions}{91}
\contentsline {section}{\numberline {9.2}Evidence for dark matter from X-rays observations}{92}
\contentsline {section}{\numberline {9.3}Metallicity of the Intra-cluster medium.}{94}
\contentsline {section}{\numberline {9.4}The dark matter density of the Universe}{94}
\contentsline {section}{\numberline {9.5}Summary}{98}
\contentsline {chapter}{\numberline {10}Galaxy statistics}{99}
\contentsline {section}{\numberline {10.1}The density-morphology relation}{100}
\contentsline {section}{\numberline {10.2}Galaxy scaling relations}{100}
\contentsline {subsection}{\numberline {10.2.1}The Tully-Fisher relation in spirals}{100}
\contentsline {subsection}{\numberline {10.2.2}The Faber-Jackson relation in ellipticals}{104}
\contentsline {section}{\numberline {10.3}Tully-Fisher and Fundamental plane relations as standard candles}{107}
\contentsline {section}{\numberline {10.4}Galaxy luminosity function}{108}
\contentsline {section}{\numberline {10.5}Epilogue}{110}
\contentsline {section}{\numberline {10.6}Summary}{112}
\contentsline {chapter}{\numberline {11}Active Galactic Nuclei}{113}
\contentsline {section}{\numberline {11.1}Discovery and observational properties}{114}
\contentsline {section}{\numberline {11.2}The central engine, and unification schemes}{115}
\contentsline {section}{\numberline {11.3}Evidence for a SMBH}{117}
\contentsline {subsection}{\numberline {11.3.1}Photometry}{117}
\contentsline {subsection}{\numberline {11.3.2}Stellar kinematics}{118}
\contentsline {subsection}{\numberline {11.3.3}Stellar kinematics in the MW centre}{119}
\contentsline {subsection}{\numberline {11.3.4}Methods based on gas kinematics}{119}
\contentsline {subsection}{\numberline {11.3.5}Profile of X-ray lines}{120}
\contentsline {section}{\numberline {11.4}Discussion}{121}
\contentsline {section}{\numberline {11.5}Summary}{122}
\contentsline {chapter}{\numberline {12}Gravitational lensing}{123}
\contentsline {section}{\numberline {12.1}The lens equation}{124}
\contentsline {subsection}{\numberline {12.1.1}Bending of light}{124}
\contentsline {subsection}{\numberline {12.1.2}Point-like lens and source}{125}
\contentsline {subsection}{\numberline {12.1.3}More realistic lensing}{127}
\contentsline {section}{\numberline {12.2}Micro-lensing}{131}
\contentsline {section}{\numberline {12.3}Strong lensing}{132}
\contentsline {section}{\numberline {12.4}Weak lensing}{134}
\contentsline {section}{\numberline {12.5}Summary}{136}