ArXiv ExgCo


 * Early-Type Galaxies
 * Galaxy Group and Cluster
 * Star Forming in Galaxies
 * Active Galactic Nuclei
 * Really High-Redshift Universe
 * The Large-Scale Structure and Cosmology

Structural Evolution

 * There is some strong evidence that giant elliptical galaxies grow their extended stellar haloes slowly, through accretion, around a dense, compact core (e.g. van Dokkum et al., 2010; van Dokkum & Conroy, 2012 ) [arXiv:1212.1451]


 * A variety of deep imaging studies show that many ellipticals have extended tidal debris from late accretion events (e.g., Malin & Carter 1983, Tal et al. 2009, Janowiecki et al. 2010 )

Stellar Population

 * For sufficiently nearby ellipticals, the discrete stellar populations can be imaged using the Hubble Space Telescope (HST), giving strong constraints on the age and metallicity of the stars (e.g., Rejkuba et al. 2005, 2011; Harris et al. 2007 ). [arXiv:1301.4898]


 * Ellipticals generally have a gradual radial decline in the mean metallicity over the inner few effective radii (re), with gradients of d[Fe/H]/dlog(r)~-0.1 to -0.3 (e.g., Peletier et al. 1990, Kobayashi & Arimoto 1999 )


 * Difficulties in using [alpha/Fe] to measure the SF timescale:
 * Unknown type Ia SNe delay time distribution.
 * Overall SN Ia rate may vary with some systematic way
 * Possibility of selective mass-loss such that Fe is preferentially lost from the system
 * Potential variation in the IMF
 * See: Worthey et al. 1992; Thomas et al. 1999; Trager et al. 2000
 * A promising alternative chronometer is Ba, which is believed to form predominately within the envelopes of asymptotic giant branch (AGB) stars via s-process neutron captures ( Burbidge et al. 1957; Busso et al. 1999; Herwig 2005 )
 * Sr is another neutron capture element with strong transitions in the blue. Like Ba, Sr is predominantly produced by the s-process, at least in the solar system. These two elements probe two of the three s-process peaks, with Sr belonging to the first (along with Y and Zr), and Ba belonging to the second (along with La, Ce, Pr, and Nd). While the nucleosynthetic origin of Ba is relatively secure, the same cannot be said for the elements in the first s-process peak ( Couch et al. 1974; Woosley & Hoffman 1992; Raiteri et al. 1993; Sneden et al. 2008 ).
 * Indeed, current chemical evolution models of the Galaxy are unable to reproduce the observed behavior of Sr-Y-Zr at low metallicity without appealing to exotic and/or ad hoc nucleosynthetic sites (e.g., Travaglio et al. 2004; Qian & Wasserburg 2008 )

Interstellar Medium

 * Early-type galaxies used to be regarded as purely stellar systems over the largest part of the last century, even though the presence of little or no interstellar medium in these old stellar systems was soon recognised as a problem by Faber & Gallagher (1976).
 * The finding by the Einstein observatory that early-type galaxies are surrounded by massive haloes of hot ($$\sim10^6 - 10^7 K$$) X-ray emitting gas ( Forman et al. 1979 )
 * Correlation between the X-ray luminosity of such haloes $$L_X$$ and the optical luminosity $$L_B$$ of the galaxies they contain (e.g. Forman, Jones, & Tucker 1985; Trinchieri & Fabbiano 1985 ), which when interpreted led to a relatively simple model linking the hot gas reservoirs to the stellar-mass loss material of early-type galaxies (e.g. Canizares, Fabbiano, & Trinchieri 1987 ). About the scatter of this relation, also see reviews by Mathews & Brighenti 2003 and Pellegrini 2012
 * Galaxies in dense galactic environment were found to be X-ray faint ( White & Sarazin 1991 )
 * S0s and flat Es show lower X-ray luminosities than rounder elliptical galaxies of the same optical luminosity prompted further theoretical studies concerning the role of intrinsic flattening (which reduces the binding energy of the hot gas and makes it harder to retain ( Eskridge, Fabbiano & Kim 1995a,b; Ciotti & Pellegrini 1996; D'Ercole & Ciotti 1998; Brighenti & Mathews 1996 )


 * Largest compilation of LX measurements obtained with ROSAT and Einstein: 401 early-type galaxies ( Ellis & O'Sullivan 2006; O'Sullivan, Forbes, & Ponman 2001 )


 * Effect of dust on the color gradients and the kinematics of elliptical galaxies ( Witt et al. 1992; Baes & Dejonghe 2001, 2002 )
 * The presence of dust in ETG has first been inferred from the absorption of stellar light ( Bertola & Galletta 1978; Ebneter & Balick 1985; Goudfrooij et al. 1994 ).
 * 40-60% of ETGs have been observed with dust emission in FIR band ( Knapp et al. 1989; Temi et al. 2004, 2007; see also Leeuw et al. 2004; Savory et al. 2009 )

Extragalactic Globular Clusters

 * Definition of specific frequency ($$S_N$$) of globular clusters: ( Harris & van den Bergh 1981 >)


 * Globular clusters around NGC 1399 in Fornax (also NGC1404, NGC1387): ( Bridges et al. 1991; Wagner et al. 1991; Ostrov et al. 1008; Dirsch et al. 2003 )
 * NGC 1404 GCs may have been tidally stripped by NGC 1399, resulting in a high SN value of NGC 1399 ( Forbes et al. 1997 )
 * Kissler-Patig et al. (1999) also proposed that the over abundance of NGC 1399 GCs can be explained by tidal stripping of GCs from neighboring galaxies and by the accretion of GCs in the gravitational potential of the Fornax cluster. (see also: Grillmair et al. 1999; Bekki et al. 2003; Bassino et al. 2006a )
 * First suggestion of color bimodity in NGC 1399 ( Ostrov et al. 1993 ), also see the following studies by Ostrov et al. 1998; Grillmair et al. 1999; Forbes et al. 1998; Dirsch et al. 2003; Forte et al. 2005
 * Blakeslee et al. (2012) found that the optical–infrared color distribution of NGC 1399 GCs is unimodal, whereas the optical colors of the GCs exhibit bimodality.
 * Analysis from ACS/Fornax survey: ( Mieske et al. 2010; Masters et al. 2010; Villegas et al. 2010; Liu et al. 2011 )
 * Kinematics and dynamics of GCs ( Grillmair et al. 1994; Kissler-Patig et al. 1999; Richtler et al. 2004; Schuberth et al. 2010 )
 * Stellar population and chemical properties ( Kissler-Patig et al. 1998; Forbes et al. 2001 )
 * For NGC1404 and NGC1387 ( Richtler et al. 1992; Forbes et al. 1998; Grillmair et al. 1999; Larsen et al. 2001; Bassino et al. 2006b )


 * GCs around isolated elliptical galaxies: [arXiv:1212.1451]
 * NGC 720 ( Kissler-Patig et al. 1996 )
 * NGC 821 ( Spitler et al. 2008 )
 * NGC 3585 ( Hempel et al. 2007; Humphrey et al. 2009; Lane et al. 2012 )
 * NGC 3818 ( Cho et al. 2012 )
 * NGC 5812 ( Lane et al. 2012 )


 * In many cases it seems that red (metal rich) GC populations may have formed in situ along with the galaxy, while the bluer (more metal poor) GCs arrived later as part of the hierarchical merger process, assuming mainly minor mergers ( Lee et al., 2008; Elmegreen et al., 2012 ) [arXiv:1212.1451]


 * The Washington photometric system ( Canterna, 1976 ) has been chosen as it has the advantage of being a good discriminator between compact blue background galaxies and GC candidates ( Dirsch et al., 2003a ); Furthermore, an apparently Universal peak exists in the (C−R) colour of old globular cluster populations associated with elliptical galaxies (e.g. Richtler et al., 2012 ) [arXiv:1212.1451]



Extragalactic Planetary Nebula

 * Planetary Nebulae (PNe) in external galaxies are mostly regarded either as tracers of the gravitational potential (e.g Romanowsky et al. 2003; Douglas et al. 2007 ) or as indicators for the distance of their galactic hosts (e.g., Ciardullo et al. 1989; Jacoby, Ciardullo, & Ford 1990; Jacoby et al. 1992 ), with the latter advantage owing to the nearly universal – though not fully understood – shape of the PNe
 * Extra-galactic PNe luminosity function (PNLF, generally in the [O III]λ5007 emission). can also be used as probes of their parent stellar population (e.g., Richer, Stasinka, & McCall 1999; Jacoby & Ciardullo 1999; Dopita et al. 1997 ) and understanding in particular the origin of the PNLF is a puzzle that, once solved, promises to reveal new clues on the late stages of stellar evolution and on the formation of PNe themselves (see, e.g., Ciardullo 2006 ).

Intra-Cluster Light

 * Important references: Gregg & West 1998; Mihos et al. 2005; Zibetti et al. 2005; Gonzalez et al. 2007; Krick & Bernstein 2007; Rudick et al. 2010; Burke et al. 2012


 * The importance of the ICL in the baryon budget is the subject of current debate: [arXiv:1212.1613]
 * Krick & Bernstein 2007 : 6-22% within 25% of Virial radius
 * Gonzalez et al. 2005; 2007 : 33% for BCG+ICL within $r_200$
 * McGee & Balogh 2010 : ~50% (mapping of hostless SN Ia)
 * Zibetti et al. 2005 : ~11% within 500kpc (stacking of SDSS cluster)


 * Its origin at least partly in matter ejections from galaxies during galaxy-galaxy or galaxy-cluster potential interactions (see e.g. Adami et al. 2005b, or Dolag et al. 2010 for recent simulations)

High-Redshift Early-Type Galaxies

 * Radio galaxies are known to be massive elliptical types which formed in the early Universe ( van Breugel et al. 1998; Pentericci et al. 2001; Zirm et al. 2003; Lacy et al. 2011 ).
 * This population is young but already massive (10^12M⊙) out to high z=4 redshifts ( Rocca-Volmerange et al. 2004 ).
 * The mid−IR, far−IR and sub−millimeter emission from distant radio galaxies were interpreted as starbursts mainly initiated by major mergers ( De Breuck et al. 2010; Ivison et al. 2008; Ivison et al. 2012; Engel et al. 2010; Seymour et al. 2010; Seymour et al. 2012 ).


 * The quiescent galaxies form a signiﬁcant fraction (30 − 50%) of all massive z~2 galaxies (e.g. Kriek et al. 2006; Williams et al. 2009; Toft et al. 2009 ) [arXiv:1212.1158]


 * The number density of massive quiescent galaxies has grown by almost a factor of 10 since z = 3 ( Labbe et al. 2005; Arnouts et al. 2007; Fontana et al. 2009; Taylor et al. 2009; Ilbert et al. 2010; Cassata et al. 2011; Brammer et al. 2011; Dominguez Sanchez et al. 2011; Bell et al. 2011 )

Model Fitting

 * Sersic functions are the most common distributions that have been used to describe and ﬁt the observed proﬁles of galaxies and their constituent morphological components (e.g. Hoyos et al. 2011, Simard et al. 2011, Kelvin et al. 2012, Haubler et al. 2012).
 * The derived Sersic indexes are then used (either by themselves or in combination with other photometric parameters) to classify galaxies as disk- or spheroid-dominated ones (e.g. Kelvin et al. 2012, Grootes et al. 2012 ) or in terms of a bulge-to-disk ratio when bulge/disk decomposition is performed ( Allen et al. 2006, Simard et al. 2011, Lackner & Gunn 2012 )

Thick Disc

 * Ever since the discovery that the luminosity distribution of edge-on S0 galaxies could be well ﬁt by including a thick and thin disk component ( Burstein 1979 ), evidence has accumulated for the ubiquity of thick disk components in galaxies.
 * van der Kruit & Searle (1981) found that the disk of the late type galaxy NGC 891 required three separate components to ﬁt its vertical proﬁle, a bulge, thick and thin disk.
 * Number counts of dwarf stars in the Solar Neighborhood found that the Milky Way disk also was well ﬁt using two distinct scale heights ( Gilmore & Reid 1983 )
 * Subsequent observations found that every observed disk galaxy are characterized by more than one single vertical scale height, but are well ﬁt by two components ( van der Kruit & Searle 1982; Dalcanton & Bernstein 2000, 2002; Seth et al. 2005; Yoachim & Dalcanton 2006; de Jong et al. 2007 ).


 * In the Milky Way, a number of spectroscopic studies have found distinct stellar abundances in stars that are kinematically associated with the thick disk. ( Majewski 1993; Gilmore et al. 1995; Fuhrmann 1998; Chiba & Beers 2000; Prochaska et al. 2000; Bensby et al. 2003, 2005; Wyse et al. 2006; Reddy et al. 2006; Fuhrmann 2008; Ruchti et al. 2010 ).
 * Stars in the thick disk components are more α-enhanced than kinematically cooler thin disk stars.

Bar

 * Stellar bars, in particular, constitute an efficient way to redistribute angular momentum among the different galaxy components – gas, stars and dark matter ( Bournaud & Combes 2002; Berentzen et al. 2007; Athanassoula & Misiriotis 2002 ).
 * Angular momentum redistribution is particularly efficient at resonances, and a coupling between the action of a bar and that of spiral arms can cause a rapid migration of stars through the disk ( Minchev & Famaey 2010; Minchev et al. 2011 ), with characteristic time scales significantly lower than those predicted when the action of spiral arms alone is taken into account ( Sellwood & Binney 2002; Roskar et al. 2008a ).


 * Cases where bulges seen in edge-on galaxies have a distinctly "boxy" or even "peanut-shaped" morphology. A series of imaging studies ( Jarvis 1986; de Souza & Dos Anjos 1987; Shaw 1987; Dettmar & Barteldrees 1990; Lutticke et al. 2000a ) gradually demonstrated that such structures are actually quite common
 * Even the Galaxy's own bulge has turned out to be boxy (e.g., Kent et al. 1991; Dwek et al. 1995 )
 * The peculiarity is not just morphological: several early stellar-kinematic studies noted that strongly boxy or peanut-shaped bulges exhibited cylindrical stellar rotation (e.g., Bertola & Capaccioli 1977; Kormendy & Illingworth 1982 )
 * Although several models have been proposed for boxy or peanut-shaped bulges, such as their being the results of minor mergers (e.g., Binney & Petrou 1985 ), the most successful explanation has come from investigations of bar formation and evolution. A pioneering 3D N-body study by Combes & Sanders (1981) noted that the bars which formed in their simulation showed "a peanut-shape morphology" when the model was viewed edge-on with the bar perpendicular to the line of sight
 * In the early 1990s, simulations of galaxy discs clearly showed that a vertically unstable \buckling" phase often followed the formation of a bar (e.g., Combes et al. 1990; Raha et al. 1991 ); the morphology and cylindrical kinematics of the resulting structure matched observations of boxy and peanutshaped bulges (see Athanassoula 2005 and Debattista et al. 2006 for reviews ).
 * This rapid, asymmetric buckling phase is usually assumed to be driven by a global bending instability (e.g., Merritt & Sellwood 1994 ). However, alternate formation mechanisms which involve the resonant heating or trapping of stellar orbits have been suggested ( Combes et al. 1990; Quillen 2002; Debattista et al. 2006 )
 * Other theoretical studies have investigated the underlying orbital structure which may support this morphology (e.g., Pfenniger 1985; Pfenniger & Friedli 1991; Patsis et al. 2002; Martinez-Valpuesta et al. 2006 ), explored conditions under which it may be promoted or suppressed (e.g., Berentzen et al. 1998; Athanassoula & Misiriotis 2002; Athanassoula 2005; Debattista et al. 2006; Wozniak & Michel-Dansac 2009 ), and even suggested that multiple phases of buckling and vertical growth can take place ( Martinez-Valpuesta et al. 2006 ).
 * Evidence confirming the association of bars with boxy/peanut-shaped (B/P) bulges in real galaxies has come primarily from spectroscopy of edge-on galaxies. The major axis kinematics of ionized gas ( Kuijken & Merrifield 1995; Merrifield & Kuijken 1999; Bureau & Freeman 1999; Veilleux et al. 1999 ) and stars ( Chung & Bureau 2004 ) in edge-on galaxies with boxy or peanut-shaped bulges displays the characteristic imprint of bars, as predicted by orbital analyses and simulations, both pure N-body ( Athanassoula & Bureau 1999; Bureau & Athanassoula 2005 ) and hydrodynamical (e.g., Athanassoula & Bureau 1999 ).
 * In addition, near-IR imaging of edge-on systems indicates that B/P bulges are accompanied by larger-scale extensions in the disc of the galaxy, suggestive of the vertically thin outer zones of bars ( Lutticke et al. 2000b; Bureau et al. 2006 ). The frequency of boxy and peanut-shaped bulges is consistent with most barred galaxies having vertically thickened inner regions ( Lutticke et al. 2000a ).

Galaxy Group and Cluster

 * First evidence of superclusters as agglomerations of rich clusters of galaxies: Abell 1961 [arXiv:1212.1597]
 * Superclusters are generally deﬁned as groups of two or more galaxy clusters above a given spatial density enhancement ( Bahcall 1988 )
 * The existence of superclusters was confirmed by: Bogart & Wagoner 1973; Hauser & Peebles 1973; Peebles 1974
 * Catalogs of superclusters: e.g. Rood (1976), Thuan (1980), Bahcall (1984), Batuski & Burns (1985), West (1989), Zucca et al. (1993), Kalinkov & Kuneva (1995), Einasto et al. (1994, 1997, 2001, 2007), and Liivamagi et al. (2012)

{\delta}^2=\frac{11}{{{\sigma}_v}^2}[(v_{loc}-{\overline{v}})^2+({\sigma}_{loc}-{\sigma}_v)^2] $$
 * The Dressler-Shectman test for substructure in galaxy cluster:( Dressler & Shectman 1988; Halliday et al. 2004 )
 * $${\overline{v}}$$ and $${\sigma}_v$$ is the mean velocity and velocity dispersion of the cluster.
 * $$v_{loc}$$ and $${\sigma}_{loc}$$ is the mean velocity and velocity dispersion of that galaxy and its ten nearest neighbours within the cluster
 * The sum of the $$\delta$$ value of each galaxy, $$\Delta$$, gives the measure of the total substructure present in a cluster.


 * Massive galaxy clusters are important astrophysical objects. As the largest virialized structures in the universe, their space density, mass function, and clustering provide robust constraints on cosmological models (e.g., Edge et al. 1990; Eke et al. 1998; Bahcall et al. 2003; Gladders et al. 2007; Vikhlinin et al. 2009; Rozo et al. 2010; Sehgal et al. 2011; Benson et al. 2011 ).
 * As the highest-density regions in the universe, they are also important cosmic laboratories for studying how environment aﬀects the evolution of galaxies (e.g., Dressler 1980; Balogh et al. 1999; Poggianti et al. 1999, 2006; Patel et al. 2009a,b; Vulcani et al. 2010; Wetzel et al. 2011; Muzzin et al. 2012, and numerous others).


 * Galaxy cluster at z>1.0: ( Stanford et al. 1997, 2005, 2006; Rosati et al. 1999 )
 * In previous decades searches for the highest-redshift clusters were almost completely dominated by X-ray surveys (e.g., Gioia et al. 1990; Rosati et al. 1998 )
 * The current large sample of z>1 clusters comes from:
 * X-ray surveys (e.g., Mullis et al. 2005; Stanford et al. 2006; Bremer et al. 2006; Pacaud et al. 2007; Henry et al. 2010; Fassbender et al. 2011a,b; Nastasi et al. 2011; Santos et al. 2011 )
 * Spacebased MIR surveys (e.g., Stanford et al. 2005; Eisenhardt et al. 2008; Muzzin et al. 2009; Wilson et al. 2009; Papovich et al. 2010; Demarco et al. 2010; Brodwin et al. 2011; Stanford et al. 2012; Zeimann et al. 2012 )
 * Ground-based NIR surveys (e.g., Gobat et al. 2011; Spitler et al. 2012 )
 * Millimeter SZE surveys (e.g., Brodwin et al. 2010; Foley et al. 2011; Stalder et al. 2012 )
 * Narrow-band and MIR searches around high-redshift radio galaxies (e.g., Venemans et al. 2007; Galametz et al. 2010, 2012 ).
 * The red-sequence method of finding high-z clusters: ( Gladders & Yee 2000, 2005; Muzzin et al. 2009; Wilson et al. 2009 )
 * 3.6mu-4.5mu Color method ( Papovich 2008; Papovich et al. 2010 )
 * The Stellar Bump Sequence method ( Muzzin et al. 2013 )


 * High-z Radio Galaxies (HzRGs) are signposts of large over-densities in the early Universe, or proto-clusters, which are believed to be the ancestors of local rich clusters (e.g. Miley & De Breuck 2008; Venemans et al. 2007 ).
 * Historically, HzRGs were often identiﬁed by the ultrasteep spectrum of their easily detectable radio continuum, which served as a beacon for tracing the surrounding faint proto-cluster ( Rottgering et al. 1994; Chambers et al. 1996 ).
 * e.g Spiderweb Galaxy: (z=2.16; Pentericci et al. 1997; Miley et al. 2006; Seymour et al. 2007, 2012; De Breuck et al. 2010; Hatch et al. 2009; Pentericci et al. 1997; Carilli et al. 1998, 2002; Nesvadba et al. 2006; Pentericci et al. 2000; Kurk et al. 2004; Croft et al. 2005; Doherty et al. 2010; Kuiper et al. 2011; Kodama et al. 2007; Zirm et al. 2008; Pentericci et al. 2002; Stevens et al. 2003; Ogle et al. 2012; ).

Birhgtest Cluster/Group Galaxies (BCG/BGG)

 * Brightest cluster galaxies (BCGs) form the massive end of the galaxy population. They are generally associated with old stellar populations, little star formation and large sizes ( von der Linden et al. 2007; Bernardi 2009 ), except in strong cooling ﬂows. In some clusters, BCGs are surrounded by a diﬀuse envelope of intracluster light. This additional light has been measured in a number of nearby clusters ( Gonzalez et al. 2005 ) as well as in stacks of BCGs from the Sloan Digital Sky Survey ( Zibetti et al. 2005 ).


 * There have been claims that the observed evolution of BCGs (e.g. Collins et al. 2009; Stott et al. 2011 ) disagrees with the predictions of semi-analytic models of galaxy formation ( De Lucia & Blaizot 2007 ).
 * However, recent results from Lidman et al. (2012) seem to indicate less tension between the models and observations


 * Repeated dissipationless mergers of galaxies as mechanism for the growth of BCG: ( Dubinski 1998; Ruszkowski & Springel 2009; Rudick et al. 2006; Laporte et al. 2012 )


 * Galactic cannibalism as a possible mechanism to explain the formation of cD galaxies ( White 1976; Ostriker & Hausman 1977 )

Radio and X-ray Emitting Gas in Cluster

 * '''Coincidence between cool X-ray emitting gas and Ha filaments:
 * ESO 137-001 in Abell 3627: ( Sun et al. 2007 )
 * BCG of Perseus Cluster: ( Sanders & Fabian 2007; Fabian et al. 2008, 2011 )
 * BCG of Centaurus Cluster: ( Sanders & Fabian 2002, 2008 )
 * Virgo: M87 ( Werner et al. 2010, 2012 ); M86 ( Ehlert et al. 2012 )


 * A fraction of galaxy clusters shows the presence of diﬀuse radio emission on Mpc scale. In general, we can distinguish between two morphologies: "radio halos" and "radio relics".
 * In the ﬁrst case, the emission comes from central cluster regions, while "relics" take place in the peripheral zones ( Giovannini et al. 2002; Ferrari et al. 2008; Venturi 2011; Feretti et al. 2012 ).
 * The synchrotron origin of this radio emission reveals the presence of a large-scale magnetic ﬁeld and relativistic particles spread out of the cluster.
 * Radio relics seem to be directly linked with merger shocks ( Ensslin et al. 1998; Roettiger et al. 1999; Ensslin & Gopal-Krishna 2001; Hoeft et al. 2004 ).
 * The turbulence following cluster mergers has been proposed as one of the most important eﬀects to produce giant radio halos ( Brunetti et al. 2001, 2009 ).

Compact Groups

 * Hickson Compact Groups: ( Hickson 1982; 1992 ): 100 nearby compact groups; 92 groups consisting of at least three accordant members
 * That many of the groups are real physical associations is further attested by the presence of hot intragroup gas in many of them ( Ponman et al. 1996; Desjardins et al. 2012 ). Signs of interactions within these groups include peculiar rotation curves and disturbed morphologies of group members ( Rubin et al. 1991; Mendes de Oliveira & Hickson 1994 ), as well as the presence of intragroup light ( Da Rocha et al. 2008 ).
 * HI deﬁciency in compact group galaxies has long been suspected (Williams & Rood 1987; Huchtmeier 1997)
 * An evolutionary sequence in which compact group galaxies become increasingly deﬁcient in neutral hydrogen is proposed by the HI study of 72 HCGs ( Verdes-Montenegro et al. 2001 )
 * More recent observations using the Green Bank Telescope, sensitive to extended, faint HI emission, have revealed a diﬀuse HI component in all the groups studied ( Borthakur et al. 2010 ), explaining in part the “missing HI”
 * Molecular gas properties and relation to star-formation: ( Leon et al. 1998; Verdes-Montenegro et al. 1998; Martinez-Badenes 2012 )
 * Study the evolution of Compact Group galaxies using color-color diagram from Spitzer ( Johnson et al. 2007; Walker et al. 2010, 2012 ; see also Tzanavaris et al. 2010; Bitsakis et al. 2011 about the sSFR of Compact Group galaxies and their position on color-magnitude diagram.)
 * AGN properties in Compact Group galaxies ( Bitsakis et al. 2011; Martinez et al. 2010; Rasmussen et al. 2008 ): High fraction, low-luminosity, no clear correlation with the dynamical state of the group. [arXiv:1301.4549]


 * Shock-heating as a viable mechanism in Compact Group: Powerful mid-infrared molecular hydrogem (H_2) line emission from an intergalactic shock wave in HCG92 (Stephans Quintet) ( Appleton et al. 2006; Cluver et al. 2010 )
 * The emission was found to be spatially associated with a 40 kpc-long Xray and radio-continuum ﬁlament believed to be formed as a result of a high-speed collision [arXiv:1301.4549]

Environmental Effect on Stars and Gas

 * 1) Ram-pressure Stripping: (Gunn & Gott )
 * 2) * Complex physics is required to account for the morphology of the stripped gas tails and their multiwavelength properties (e.g. Roediger & Bruggen 2006, 2007, 2008b; Tonnesen & Bryan 2010; Tonnesen et al. 2011; Tonnesen & Bryan 2012 )
 * 3) Viscosity of the ICM: (Roediger & Bruggen 2008a )
 * 4) Turbulence and Magnetic Fields: (Ruszkowski et al. 2012 )

Dwarf Galaxies

 * Indeed, it is currently well established that the low-mass haloes where dwarf galaxies probably reside are extremely inefficiant in retaining baryons and in converting them into stars, as indicated by their observed high total-to-baryonic ( Strigari et al. 2008; Walker et al. 2009 ) and gas mass fractions ( Geha et al. 2006; Warren et al. 2007 )


 * The SFH of Local Volume dwarfs: (Grebel 1997; Mateo 1998; Dolphin 2002; Tolstoy et al. 2009; Weisz et al. 2011)
 * The actual duration of starbursts and their role in the SFHs of the different dwarf types are still a matter of intense debate (Ostlin et al. 2001; Sanchez Almeida et al. 2008; Lee et al. 2009b; McQuinn et al. 2009)

Blue Compact Dwarf Galaxies

 * Nearby blue compact dwarf galaxies (BCDs) are a unique category of galaxies that have low metallicity and high gas fraction in the nearby Universe ( Sargent & Searle 1970; van Zee, Skillman, & Salzer 1998; Kunth & Ostlin 2000 )
 * Some BCDs are also experiencing the most active class of star formation with the formation of super star clusters (SSCs) ( Turner et al. 1998; Kobulnicky & Johnson 1999 ).
 * All these BCDs are also classiﬁed as Wolf-Rayet galaxies: the Wolf-Rayet feature indicates that the typical age of the current starburst is a few Myr ( Vacca & Conti 1992; Lopez-Sanchez & Esteban 2010 )

High Velocity Clouds

 * The discovery of HVC: Muller et al. 1966
 * Definition: |v_LSR|>90 km/s; (Intermediate Velocity Clouds, IVCs: 40km/s<|v_LSR|<90km/s
 * Review: Richter 2006; Wakker et al. 1998
 * HVCs span a relatively large range in metallicities from ~0.1 to 1 Solar ( Wakker et al. 1999, 2001; Richter et al. 1999, 2001; Gibson et al. 2001; Tripp et al. 2003; Collins et al. 2003; Richter et al. 2005, 2009; Shull et al. 2011 ), indicating that HVCs and IVCs have various origins.
 * Recent distance estimates of several IVCs and HVCs indicate that most of the IVCs appear to be located within 2 kpc from the Galactic disc, in accordance with the scenario that IVCs represent gas structures related to the galactic fountain ( Wakker et al. 2008; Smoker et al. 2011 ).
 * Most of the HVCs appear to be located at distances < 20 kpc ( Wakker et al. 2007; Thom et al. 2006, Thom et al. 2008 )
 * HVCs indicate gas circulation processes in the intermediate (d<100kpc) environment of the Milky Way. Their total HI mass is about ~10^8 Msolar; and contribute ~0.7M_solar/yr to the Milky Way's gas-accretion rate ( Richter 2012; Wakker 2004

Galactic Winds

 * Possible driving processes of GWs:
 * Thermal pressure due to supernova heating ( Larson 1974; Dekel & Silk 1986; Mac Low & Ferrara 1999; D’Ercole & Brighenti 1999; Strickland & Stevens 2000; Melioli et al. 2008, 2009; Hill et al. 2012 )
 * Radiation pressure on dust grains ( Martin 2005; Murray et al. 2005; Nath & Silk 2009 )
 * Cosmic ray pressure ( Breitschwerdt et al. 1991; Everett et al. 2008; Uhlig et al. 2012 )
 * Supersonic turbulence ( Scannapieco & Bruggen 2010</span》)
 * In most of these processes, SNe are the main source of energy injection which is then reprocessed.

Neutral Hydrogen (HI)

 * HI velocity dispersions typically vary between 5~15 km/s across a wide range of disk galaxy types, and generally decrease in the outskirts of galaxies to 6-10 km/s (e.g., Tamburro et al. 2009 )
 * Two stable temperatures for HI gas:~150 K for the cold neutral medium (CNM) and ~7000 K for the warm neutral medium (WNM). These temperatures correspond to velocity dispersions of 1 km/s and 7 km/s at typical ISM pressures, which is often smaller than the observed line widths in nearby galaxies. ( Wolfire et al. 1995 ). This mismatch suggests that the line widths are set primarily by turbulence.
 * However, the time scale for dissipating turbulent energy is ~10^7 yr ( Mac Low 1999 ). Energy must therefore be continually injected in order to maintain the Hi line widths we see in galaxies.
 * The sources of energy that drive turbulence are still debated:
 * Star formation ( Kim et al. 1998; Tamburro et al. 2009; Joung et al. 2009 ).
 * However, HI velocity dispersions are still substantial at large radii
 * Magneto-rotational instability (MRI; Sellwood & Balbus 1999 )
 * Shear from rotation curves (e.g., Schaye 2004 )
 * Gravitational instabilities (e.g., Wada et al. 2002 )

The X_CO Factor

 * A variety of observations have shown that $$\alpha\sim4.4 M_{\odot}{pc}^{-2} (K km s^{-1})^{-1}$$ is characteristic of the local area of the Milky Way ( Solomon et al. 1987; Strong & Mattox 1996; Abdo et al. 2010 ) [arXiv:1212.1208]


 * Different techniques to explore the possibility of a changing X_CO across different types of galaxies in nearby Universe:
 * These include virial mass measurements of individual GMCs in the Milky Way, the local group, and nearby spirals (e.g. Wilson 1995; Blitz et al. 2007; Bolatto et al. 2008; Fukui & Kawamura 2010, and references therein )
 * Estimating the molecular gas mass from dust far-IR emission modeling while constraining the dust-to-gas ratio and the contribution from atomic hydrogen ( Israel 1997; Leroy et al. 2011, 2012 )
 * Using the star formation rate (SFR) under the assumption of a known molecular gas depletion timescale to estimate the amount of H_2 ( Schruba et al. 2012; McQuinn et al. 2012 ).
 * X_CO shows higher values for lower metallicity systems. This increase is most likely driven not only by a decrease in the carbon and oxygen abundances, but mainly by a drop in the optical depth within GMCs due to a lower abundance of dust. The CO/C+ dissociation boundary moving inwards within the clouds, leaving behind large envelopes of "CO Dark" molecular gas (e.g Bolatto et al. 1999 )
 * The molecular gas in merging and starburst galaxies show X_CO value factors of a few lower than the MW value. ( Wild et al. 1992; Shier et al. 1994; Mauersberger et al. 1996; Solomon et al. 1997; Downes & Solomon 1998; Bryant & Scoville 1999; Meier et al. 2010 )
 * This eﬀect is thought to be caused by the impact of higher gas temperatures and stronger turbulence on the brightness temperature of the CO line and the escape probability of CO(1-0) photons. ( Shetty et al. 2011 )
 * The lower X_CO factor is also found in high-redshift "normal" star-forming galaxies ( Genzel et al. 2012 ) [arXiv:1212.4152]


 * A series of studies using analytic models, numerical simulations, and combinations of both, have examined the dependance of X_CO with metallicity, gas temperature, gas dynamics, and the local radiation ﬁeld (e.g. Krumholz et al. 2011; Shetty et al. 2011; Narayanan et al. 2012; Feldmann et al. 2012a ) [arXiv:1212.4152]


 * The value of X_CO has been shown to change as a function of galactocentric radius in the MW using a series of diﬀerent techniques:
 * Dust emission modeling ( Sodroski et al. 1995 )
 * Measurements of gamma-ray emissivity from cosmic-ray gas interactions ( Digel et al. 1996; Strong et al. 2004; Abdo et al. 2010 )
 * Direct virial mass measurements of GMCs ( Arimoto et al. 1996; Oka et al. 1998 ). [arXiv:1212.4152]

Star Formation Rate Calibration and Star-Formation Law

 * Schimdt-Kennicutt law ( Schmidt 1959; Kenicutt 1998 )
 * studies of this law in spatially resolved manner across the disk of nearby galaxies ( Kennicutt et al. 2007; Bigiel et al. 2008; Blanc et al. 2009; Verley et al. 2010; Onodera et al. 2010; Schruba et al. 2011; Liu et al. 2011; Rahman et al. 2012 )
 * About the uncertainty in the slope: ( Blanc et al. 2009; Rahman et al. 2012; Calzetti et al. 2012 )
 * The normalization is consistent with a depletion timescale for molecular gas of ~ 2Gyr at the typical molecular gas surface densities ( Leroy et al. 2008; Rahman et al. 2012 )


 * The relationship between gas and stars:
 * Single galaxy: e.g., Heyer et al. 2004; Kennicutt et al. 2007; Blanc et al. 2009; Verley et al. 2010; Rahman et al. 2011
 * Small sample: e.g., Wilson et al. 2009; Warren et al. 2010
 * Large sample: e.g., Young et al. 1996; Kennicutt 1998b; Rownd & Young 1999; Murgia et al. 2002; Leroy et al. 2005; Saintonge et al. 2011


 * The fraction of interstellar gas in the molecular phase varies strongly within and among galaxies, exhibiting correlations with interstellar pressure, stellar surface density, and total gas surface density among other quantities ( Wong & Blitz 2002; Blitz & Rosolowsky 2006; Leroy et al. 2008 )
 * They advocated a scenario for star formation in disk galaxies in which star formation in isolated giant molecular clouds is a fairly universal process while the formation of these clouds out of the atomic gas reservoir depends sensitively on environment (see also, Wong 2009; Ostriker et al. 2010 ).
 * Correlations between star formation tracers and CO emission extend into the regime where atomic gas dominates the ISM ( Schruba et al. 2011 )
 * This provides the strongest evidence yet that star formation in disk galaxies can be separated into star formation from molecular gas and the balance between atomic and molecular gas, a hypothesis that has a long history (e.g., Young & Scoville 1991 )


 * Molecular gas and star formation exhibit a first order one-to-one scaling but we observe important second order variations about this scaling. (Leroy et al. 2012)


 * Radio-FIR Correlation: ( de Jong et al. 1985; Helou, Soifer & Rowan-Robinson 1985 )

Black Hole Mass Estimation

 * The black hole mass is usually estimated using reverberation mapping calibrated scaling relations (the so–called “single epoch virial method”, or SE virial, Peterson 1993; Peterson et al. 2004; Onken et al. 2004; Vestergaard & Peterson 2006; Bentz et al. 2009). [arXiv:1212.1181]

Relation and Coevolution with Host Galaxy

 * Correlations between the mass of the central black hole and absolute magnitude (Magorrian et al. 1998; Marconi & Hunt 2003; Häring & Rix 2004 ), and/or stellar velocity dispersion (Gebhardt et al. 2000; Merritt & Ferrarese 2001 ) of the spheroidal component indicate that the mass ratio between a SMBH and its bulge is constant over a wide dynamic range in mass (0.0014) [arXiv:1212.2999]


 * Related Measurements:
 * Optical imaging from space with HST can be used to disentangle the light between an AGN and its host galaxy (e.g., Sánchez et al. 2004; Jahnke et al. 2004, 2009; Bennert et al. 2011b; Cisternas et al. 2011 )
 * Measure the stellar velocity dispersion from optical spectra for less luminous AGNs (Woo et al. 2008 )
 * Measure the stellar mass' content of AGN host galaxies through template ﬁtting of the broad-band photometric spectral energy distribution (Merloni et al. 2010; Brusa et al. 2009; Xue et al. 2010 )
 * Bulge luminosity from decomposition (Giavalisco et al. 2004)
 * Possible biases originating from selection of AGN (see  Salviander et al.2007; Lauer et al. 2007 )


 * Offsets from local $$M_{BH}-M_{Bulge}$$ relation: (see Peng et al. 2006a, b )
 * Evidence for elevated black hole masses as compared to either the bulge component (Woo et al. 2008; Bennert et al. 2011b) or total (Merloni et al. 2010 ) stellar mass of the host galaxy.
 * Undermassive bulge ? (Jahnke et al. 2009; Cisternas et al. 2011 )


 * Although local early type galaxies and QSOs presented a linear scaling relation of the central black hole masses and the masses of the stellar bulge, which motivated the theoretical perspective on the growth of the central black holes and the host galaxy formation, high redshift QSOs would be the key to a robustic check of the theoretical models ( Faber et al. 1997, McLeod & Rieke 1995, Silk & Rees 1998, Wang & Biermann 1998, Wang et al. 2000, 2003, Merrit 1998, Monaco et al. 2000, Bian et al. 2003, Peng et al. 2006, Schramm et al. 2008 )

Torus, BLR, Nuclear Gas et al.

 * By means of Adaptive Optics (AO) integral-ﬁeld spectroscopy, Hicks et al. (2009, hereafter H09) showed that the molecular gas in the central tens of parsecs of Seyfert galaxies relates directly to the largest structures associated with the obscuring torus, as predicted by clumpy torus models (e.g., Nenkova et al. 2002, 2008; Schartmann et al. 2008): it is in a rotating disk-like distribution, has a high velocity dispersion relative to rotation (V/σ<1), and is optically thick [arXiv:1212.1162]


 * HCN measurements of Seyfert galaxies suggest that the nuclear dense gas also has a large dispersion (Sani et al. 2012) [arXiv:1212.1162]

Outflows, Winds, and Jet

 * Outflow can be accelerated by :
 * magnetocentrifugal forces ( Everett 2005; de Kool & Begelman 1995 )
 * radiation pressure in lines and continuum ( Murray et al. 1995; Proga, Stone, & Kallman 2000 )
 * by thermal pressure force (e.g., Balsara & Krolik 1993; Krolik & Kriss 2001; Chelouche & Netzer 2005 ).
 * The outflowing winds play an important role in three ways:
 * the extraction of angular momenta from disks allows accretions to proceed (e.g., Blandford & Payne 1982; Emmering et al. 1992; Konigl & Kartje 1994; Everett 2005 ), leading to growth of black holes
 * the disk outflow also provides energy and momentum feedback to interstellar media of host galaxies and to intergalactic media (IGM), and inhibits star formation activity (e.g., Springel, Di Matteo, & Hernquist 2005 )
 * outflowing winds may induce the metal enrichment of the IGM (e.g., Hamann, Barlow, & Junkkarinen 1997b; Gabel et al. 2006 )


 * Broad Absorption Line QSO (BALs): are detected in about 10-20% of optically selected quasars (e.g., Hewett & Foltz 2003; Reichard et al. 2003a ), and their detection rate is slightly higher in radio-quiet quasars (e.g., Stocke et al. 1992; Becker et al. 2001; Green 2006 ).
 * BALs are thought to originate in the outflowing winds when our sight-line intersects this component. This idea is supported by the fact that there are no significant differences in the properties of quasars with BALs (BAL QSOs) and those without BALs (non-BAL QSOs) ( Weymann et al. 1991; Reichard et al. 2003a ).
 * Moreover, quasar spectra tend to be redder when BAL profiles, especially those with low ionization absorption lines (i.e., LoBALs and FeLoBALs), are observed, which is probably caused by dust reddening in the outflows (e.g., Sprayberry & Foltz 1992; Yamamoto & Vansevicius 1999 )


 * For black holes there is debate as to whether the jet driver is again the disc accretion energy (e.g. Blandford & Payne 1982; Livio et al. 1999 ) or instead the black hole spin ( Blandford & Znajek 1977 ).
 * Observations of jets from AGN often encourage suggestions that the jets precess (e.g. Falceta-Goncalves et al. 2010; Kharb et al. 2010; Gong et al. 2011; Marti-Vidal et al. 2011 )

Observed Properties

 * The X-ray/UV ratio (alpha_ox) is found to be strongly anti-correlated with the ultraviolet specific luminosity $$L_{UV}$$. (Strateva et al. 2005; Steen et al. 2006; Just et al. 2007; Gibson et al. 2008; Grupe et al. 2010; Vagnetti et al. 2010 )
 * About its dispersion, "artiﬁcial alpha_ox variability" due to non-simultaneity is not the main cause of dispersion (Vagnetti et al. 2010) [arXiv:1212.3432]


 * A subset of active galactic nuclei (AGN) show in their spectra emission lines from very highly ionised atoms, known as Coronal lines (CLs). They are collisionally excited forbidden transitions within low-lying levels of ionised species with ionization potentials IP > 100 eV. CLs have been detected in the optical and infrared spectra of all types of AGN, including Seyfert 1 and Seyfert 2 galaxies, narrow-line Seyfert 1 galaxies, and radio galaxies (e.g., Penston et al. 1984; Marconi et al. 1994; Nagao et al. 2000; Sturm et al. 2002; Rodr´ıguez-Ardila et al. 2002, 2006; Deo et al. 2007; Mullaney & Ward 2008; Komossa et al. 2008; Gelbord et al. 2009 )
 * The precise nature and origin of CLs are still a matter of debate. Diﬀerent scenarios have been considered in the literature, including:
 * Winds from the molecular torus (e.g. Pier & Voit 1995; Nagao et al. 2000; Mullaney et al. 2009 )
 * (X-ray) ionised absorbers (e.g., Komossa & Fink 1997a,b; Porquet et al. 1999 )
 * A high-ionization component of the inner narrow line region (e.g., Komossa & Schulz 1997; Ferguson et al. 1997; Binette et al. 1997 )
 * A low-density component of the interstellar medium ( Korista & Ferland 1989 )
 * Photoionization by the central source is the main driving mechanism of the CL emission (e.g. Oliva & Moorwood 1990; Marconi et al. 1996; Kraemer & Crenshaw 2000b; Mazzalay et al. 2010 )

'Bumps' in AGN SED

 * 1) Big Blue Bump: (BBB: 3000-10000\AA; Sanders et al. 1989; Elvis et al. 1994; Richards et al. 2006 )
 * 2) * Thought to be the thermal radiation from accretion disk
 * 3) Infrared Bump: (~10000\AA), accounts for 20-40% of the bolometric luminosity;
 * 4) * Thought to be the thermal radiation emitted from a dusty torus located a~1 pc from the black hole ( Sanders et al. 1989 )
 * 5) Small Blue Bump: (SBB: 2200-4000\AA); minor component that superimpose to the BBB
 * 6) * is likely the blending of several iron lines and hydrogen Balmer continuum ( Wills et al. 1985; Vanden Berk et al. 2001 )
 * 7) Synchrotron Bump: for radio loud AGN or powerful blazer, extending from radio to IR/optical wavelengths
 * 8) Compton Bump: for powerful blazer, extending from X–rays to TeV energies

Clustering of QSO

 * About a review of recent progress made on the studies of clustering of QSOs see (Shen et al. 2012) and the references within.
 * QSOs lived in massive dark matter halo.
 * Relative abundance of QSOs and their host halos can constrain the duty cycle of QSO.
 * While galaxy show a strong dependence of clustering on luminosity, the QSOs do not. Scatter between the instantaneous quasar luminosity and host halo mass dilutes any luminosity dependence of the clustering.

IMBH: Intermediate Mass Black Holes
galactic halo ( Matsumoto et al. 2001; Roberts et al. 2004; Farrell et al. 2009; Jonker et al. 2010 ).
 * Recent observations of oﬀ-nuclear ultraluminous X-ray sources (ULXs) suggest the presence of intermediate mass black holes (IMBHs) not only in the neighborhood of the galaxy nucleus but also in star clusters far out in the
 * A large population of IMBHs might reside inside a galaxy halo, perhaps the leftover population of initial “seed” holes that never grew into the supermassive variety
 * Seed holes may be produced by the direct collapse of $$10^4 - 10^6$$ M_sun primordial gas clouds, by the collapse of the ﬁrst nuclear star clusters, or be the remnants of $$10^2$$ M_sun Population III stars (e.g. Loeb & Rasio 1994; Madau & Rees 2001; Devecchi & Volonteri 2009 ).

Star-Forming and AGN

 * characterizing various global statistics of the high-redshift galaxy population, including their UV luminosity function, stellar mass function, and clustering properties (e.g., Steidel et al. 1999; Giavalisco et al. 2004a; Bouwens et al. 2007; Reddy & Steidel 2009; Ouchi et al. 2004a,b; Lee et al. 2006, 2009, 2012b; Gonzalez et al. 2011 ). In addition, the overall distribution of dust content, stellar population ages, and sizes have been determined at diﬀerent cosmic epochs ( Ferguson et al. 2004; Bouwens et al. 2004, 2009, 2012; Stark et al. 2009; Reddy et al. 2006, 2012a; Lee et al. 2012a; Finkelstein et al. 2012 ) [arXiv:1212.4835]


 * The star formation rate density (SFRD) in the Universe gradually increases toward z~3 from z>6, has a peak at z=1–2, and decreases sharply from z=1 toward z=0 (e.g., Lily et al. 1996; Madau et al. 1996; Hopkins & Beacom 2006; Sobral et al. 2012b ) [arXiv:1212.4905]
 * At z=1-2, the star formation rate (SFR) in typical galaxies is an order of magnitude higher than in the local Universe ( Reddy & Steidel 2009 )
 * The star formation rate density of the Universe peaks from z~1−3 (e.g., Bouwens et al. 2009; Magnelli et al. 2011; Murphy et al. 2011 ), an epoch in which the black holes within the center of massive galaxies are simultaneously building up their mass (Wall et al. 2005; Kelly et al. 2010 )[arXiv:1212.2971]


 * The total star formation rate density, the rate at which new stars are being formed, has dropped by a factor & 10 (e.g. Wilkins et al. 2008; Zhu et al. 2009; Rujopakarn et al. 2010 ). A similar decline is seen in the total rate of accretion onto supermassive black holes (SMBHs), which is tracked by the luminosity density of Active Galactic Nuclei (AGNs) (e.g. Barger et al. 2005; Silverman et al. 2008; Aird et al. 2010 ).


 * The star-forming main-sequence: ( Brinchmann et al. 2004; Noeske et al. 2007; Elbaz et al. 2007, 2011; Daddi et al. 2007; Pannella et al. 2009; Rodighiero et al. 2011; Karim et al. 2011; Sargent et al. 2012; Nordon et al. 2012; Magnelli et al. 2013 )
 * Deﬁned in the M∗−SFR plane, this main sequence (MS) represents the “secular” and dominant mode of baryon transformation into stars (e.g. Elbaz et al. 2011; Rodighiero et al. 2011; Wuyts et al. 2011b; Daddi et al. 2009, 2007; Elbaz et al. 2007 )


 * Recent results suggest that galaxies which are still starforming at the present time (redshift, z~0), e.g. latetype galaxies such as spirals have assembled more than 80% of their stellar mass between 0<z<2 (e.g. Moster et al. 2012; Yang et al. 2012; Leitner 2012 ).


 * The most massive galaxies appear to have older stellar populations than their less massive counterparts ( Cowie et al. 1996; Bower et al. 2006; Gilbank et al. 2010 )
 * More recently it has become clear that star formation at all z is probably dominated by normal, L* star forming galaxies ( Noeske et al. 2007; Wuyts et al. 2011 ).


 * Star forming galaxies at z~2 are a mix of "puffy" and often clumpy rotating disks, mergers, and more compact dispersion-dominated objects ( Genzel et al. 2008; Shapiro et al. 2008; Cresci et al. 2009; Förster Schreiber et al. 2009; Law et al. 2009; Jones et al. 2010; Mancini et al. 2011 )


 * The stellar mass function measures the comoving space density of galaxies of a given stellar mass, making it a powerful observational tracer of galaxy growth by in situ star formation, mergers, and galaxy transformations due to star formation quenching (e.g., Drory & Alvarez 2008; Peng et al. 2010 ). ** Measurements of the SMF are also important for connecting the physics of galaxy formation to the hierarchical assembly of dark matter halos, and large-scale structure (e.g., Conroy & Wechsler 2009; Cattaneo et al. 2011; Wang et al. 2012; Leauthaud et al. 2012; Behroozi et al. 2012 ).


 * It is well documented that mergers have, on average, enhanced SFRs relative to isolated counterparts (e.g. Kennicutt et al. 1987; Barton, Geller & Kenyon 2000; Bergvall et al. 2003; Lambas et al. 2003; Nikolic, Cullen & Alexander 2004; Alonso et al. 2004, 2006; Li et al. 2008; Ellison et al. 2008, 2010; Woods et al. 2010; Darg et al. 2010a; Patton et al. 2011 ).
 * Typical SFR enhancements are a factor of a few at both low and high redshift ( Robaina et al. 2009; Wong et al. 2011 ), a minority of galaxies can have SFR enhancements of a factor of ten or more ( Scudder et al. 2012 )
 * Interactions can also lead to nuclear activity, triggering AGN over a wide variety of energies from Seyferts to quasars ( Kennicutt et al. 1987; Ramos Almeida et al. 2011, 2012; Canalizo & Stockton 2001; Ellison et al 2011b; Silverman et al. 2011; Koss et al. 2012 ).
 * It is therefore not surprising that pairs also show increased LIR and that interactions can contribute signiﬁcantly to the IR luminosity (e.g. Lonsdale, Persson & Matthews 1984; Kennicutt et al 1987; Telesco, Wolstoncroft & Done 1988; Xu & Sulentic 1991; Xu et al. 2000; Hernandez Toledo, Dultzin-Hacyan, & Sulentic 2001; Bridge et al. 2007; Smith et al. 2007; Hwang et al. 2010, 2011 ).


 * At low redshift, the vast majority of ULIRGs are mergers, with recent work suggesting that mergers may also contribute signiﬁcantly to ULIRGs at high z (e.g. Dasyra et al. 2008; Kartaltepe et al. 2010, 2012 ). As the L_IR decreases, so does the fractional contribution from mergers (e.g. Kartaltepe et al. 2010 )
 * At ﬁxed L_IR, there is an increasingly important contribution from mergers at lower redshifts ( Melbourne, Koo & Le Floch 2005; Wang et al. 2006 ).
 * However, not all mergers lead to such prodigious IR emission. Space density of mergers (e.g. Chou, Bridge & Abraham 2011 ) is 3 orders of magnitude higher than ULIRG at low redshift ( Kim & Sanders 1998 )


 * At the highest redshifts, z>2, studies have shown that although quiescent galaxies exist, they are outnumbered by star-forming galaxies at all stellar masses (e.g., Whitaker et al. 2010; Dominguez Sanchez et al. 2011 ).
 * This early epoch is followed by a period of rapid growth in the space density of massive (>10^11M⊙) quiescent galaxies between z~2 and z~1 ( Arnouts et al. 2007; Ilbert et al. 2010; Nicol et al. 2011; Brammer et al. 2011; Mortlock et al. 2011 ).
 * By z~1, the stellar mass dependence of galaxy bimodality as observed locally is largely in place: star-forming galaxies outnumber quiescent galaxies at the low-mass end of the SMF, while quiescent galaxies dominate the massive galaxy population (e.g., Bundy et al. 2006; Borch et al. 2006 ).
 * Subsequently, between z~1 and z~0, the transformation of star-forming galaxies into quiescent, passively evolving galaxies continues, leading to an approximately factor of two increase in the integrated stellar mass density of quiescent galaxies ( Bell et al. 2004; Blanton 2006; Faber et al. 2007 ).
 * The bulk of this stellar mass growth appears to be due to a rapidly rising population of intermediate mass (10^10 M⊙) quiescent galaxies, although the extent to which massive galaxies also grow through stellar accretion (i.e., mergers) remains controversial ( Cimatti et al. 2006; Scarlata et al. 2007; Brown et al. 2007; Rudnick et al. 2009; Stewart et al. 2009; Ilbert et al. 2010; Pozzetti et al. 2010; Robaina et al. 2010 ).
 * By the current epoch, quiescent galaxies vastly outnumber star-forming galaxies above 3*10^10 M⊙, and account for more than half of the total stellar mass in the local Universe ( Bell et al. 2003; Baldry et al. 2004; Driver et al. 2006 ).
 * It is not known why the stellar mass growth by in situ star formation balances—almost perfectly—the stellar mass growth of the quiescent galaxy population due to quenching (see, e.g., Arnouts et al. 2007; Martin et al. 2007; Peng et al. 2010 )


 * In the high-redshift Universe the cold gas fraction in galaxies is higher than at low-redshift and thus there is more fuel for star formation (e.g. Tacconi et al. 2010; Geach et al. 2011 ).


 * The [OII] line is empirically calibrated and extensively utilised as a important SFR indicator for galaxies at z>1 (e.g., Kennicutt 1998; Moustakas et al. 2006; Gilbank et al. 2010 ) [arXiv:1212.4905]


 * X-ray is efficient in identifying AGN from z=1-3 (e.g. Alexander et al. 2003; Brandt et al. 2001; Giacconi et al. 2002 )
 * X-ray spectra show majority of sources are obscured by gas and dust (see review by Brandt & Hasinger 2005 )
 * Based on the presence of polycyclic aromatic hydrocarbons and continuum thermal dust emission, mid-infrared spectra can be decomposed into the relative contributions of SF and AGN activity (e.g., Laurent et al. 2000; Armus et al. 2007; Sajina et al. 2007; Pope et al. 2008; Kirkpatrick et al. 2012a ).
 * At NIR: SF galaxy has a 1.6 micron bump from old population; AGN is pure power-law
 * Dust temperature from FIR peak and shape: more warmer for more luminous AGN (Haas et al. 2003)


 * The AGN luminosity function provides the principal tracer of the distribution of SMBH accretion over the history of the universe. A variety of wavebands and identiﬁcation techniques have been used to measure the luminosity function of AGNs out to high redshifts (z<6) (e.g. Boyle et al. 1987; Page et al. 1997; Richards et al. 2006; Assef et al. 2011; Ueda et al. 2003; Ebrero et al. 2009; Aird et al. 2010 ).
 * A number of studies have indicated that AGNs are preferentially found in the most massive galaxies (e.g. Kauﬀmann et al. 2003; Dunlop et al. 2003; Schawinski et al. 2007; Nandra et al. 2007; Coil et al. 2009; Hickox et al. 2009; Bongiorno et al. 2012 ).
 * A number of more recent studies, however, have shown that AGN hosts have a similar distribution of colors to galaxies of equivalent stellar masses (e.g. Xue et al. 2010; Cardamone et al. 2010; Aird et al. 2012; Hainline et al. 2012; Bongiorno et al. 2012 ). [arXiv:1301.1689]


 * The rotational transitions of the carbon monoxide (CO) molecule provide a direct probe of the excitation of the molecular gas in galaxies. Local starburst galaxies and ULIRGs (e.g. Bayet et al. 2004; Weiß et al. 2005b; Papadopoulos et al. 2007; Greve et al. 2009 ) and high redshift SMGs and quasars (e.g. Weiß et al. 2005a; Riechers et al. 2006; Weiß et al. 2007; Riechers 2011; Riechers et al. 2011 ) show signatures of excited molecular gas: observed CO line spectral energy distributions peak at Jupper > 5 with thermalized lines up to Jupper>3.
 * In contrast, studies of the Milky Way ( Fixsen et al. 1999 ) and local SFGs (e.g. Mauersberger et al. 1999; Yao et al. 2003; Mao et al. 2010 ) find a wide spread of excitation conditions, with an average that implies less-excited gas, where the Jupper = 3 line is already sub-thermal.


 * The highest-redshift QSOs known, at z>6, are fascinating objects, providing crucial clues about the growth of supermassive black holes (SMBH), their host galaxies and their environment, when the Universe was less than 1 Gyr old, toward the end of the reionization epoch. Black holes of several 10^9 M⊙ were already in place ( Willott et al. 2003, Kurk et al. 2007; Jiang et al. 2007; Mortlock et al. 2012 ).
 * It might point to the existence of a more eﬃcient process for forming a massive black hole such as direct collapse without fragmenting ( Begelman et al. 2006; Volonteri 2012 ).

LBGs, LAEs and LABs

 * These rarer, more extended, and more luminous objects are what we now call Lyman Alpha blobs (LABs) (e.g., Steidel et al. 2000; Francis et al. 2001; Matsuda et al. 2004; Dey et al. 2005; Nilsson et al. 2006; Prescott et al. 2012 ). LABs are extremely large (~30–200 kpc) radio-quiet Lya nebulae in the high redshift universe.
 * There are currently three most widely discussed scenarios to explain both the large spatial extent and powerful Lya flux of these blobs.
 * Heated by photoionization from massive stars and/or AGN ( Geach et al. 2009 ).
 * Heated by cooling flows / cold accretion ( Haiman et al. 2000; Dijkstra & Loeb 2009 ).
 * Overlapping supernova remnants from massive stars after a powerful starburst producing superwinds. ( Taniguchi & Shioya 2000; Ohyama et al. 2003 )


 * At z~3, the velocity offsets between resonance and non-resonance absorption features of Lyman-break galaxies (LBGs) (e.g., Steidel et al. 1996; Adelberger et al. 2003; Shapley et al. 2003; Steidel et al. 2010 ) and the relative strengths and velocities of multiple-peaked profiles of Lya in emission (e.g., Verhamme et al. 2006; Tapken et al. 2007; Verhamme et al. 2008; Laursen et al. 2009; Barnes et al. 2011; Kulas et al. 2012 ) all point to outflows being common in these high luminosity systems.
 * Outflows are also common in lower-luminosity objects: the spectral analysis of Berry et al. (2012) clearly demonstrates that Lya emitting galaxies at z~3 have strong galactic winds.


 * LAEs: most have SFR~2M_sun/yr and M*<10^9M_sun; These are the objects that will likely evolve into today L* galaxies like the Milky Way ( Pirzkal et al. 2007; Gawiser et al. 2007; Guaita et al. 2010 ); LAEs are relatively metal-poor and dust-free, with internal extinctions A_V<0.5 ( Gawiser et al. 2007; Guaita et al. 2010; Acquaviva et al. 2011 )
 * Their starlight is dominated by young populations with characteristically low stellar masses ( Pirzkal et al. 2007; Finkelstein et al. 2007 ) and small sizes ( Bond et al. 2009; Malhotra et al. 2012 ). Yet, the correlation properties of these objects suggest that they are associated with moderately large halos (mass~$$10^{11}M_{\odot}$$; Kovac et al. (2007); Guaita et al. (2010) ).
 * First detection of [OIII] 5007 and Ha 6541 lines for LAE at redshift 2.2<z<3.1 ( McLinden et al. 2011; Finkelstein et al. 2011l Hashimoto et al. 2012 )

SMGs

 * The redshift distribution of the SMGs has a narrow distribution with a probable median redshift of 2−3 ( Chapman et al. 2005; Aretxaga et al. 2007 )
 * Surveys at submillimetre wavelengths show that the SMG population has a sharp falloff at the bright luminosity end of their luminosity function. Gravitational lensing by intervening galaxy clusters and groups modifies the observed number counts significantly ( Blain 1996; Lima et al. 2010b; Jain & Lima 2011; Hezaveh & Holder 2011 ).
 * The cross section due to gravitational lensing may be affected by halo ellipticity (e.g. Rusin & Tegmark 2001; Huterer et al. 2005 ), the radial profile of the lens halo ( Li & Ostriker 2002; Oguri & Keeton 2004 ) as well as the size of background galaxies ( Perrotta et al. 2002; Hezaveh & Holder 2011 )


 * Engel et al. (2010) have used CO interferometric data to conclude that most bright ($$L_{IR}>5\times10^{12}L_{\odot}$$) SMGs are major mergers.

IGM and CGM

 * Observed correlation between absorption lines in background quasars and the projected distance (and velocity offset) to the associated galaxy:
 * Low-Redshift : Chen et al. 2001; Chen & Tinker 2008; Thom & Chen 2008; Yao et al. 2008; Chen et al. 2010; Prochaska et al. 2011; Thom et al. 2011; Tumlinson et al. 2011
 * High-Redshift: Simcoe et al. 2004; Steidel et al. 2010


 * Heavy elements are at high redshifts most easily detected in absorption and Damped Lyman α absorbers (DLAs, Wolfe et al. (1986) ) allow us to trace the metallicity of the cold gas in galaxies back to redshifts of z~5 (e.g., Lu et al. 1996; Prochaska et al. 2003; Rafelski et al. 2012 ).
 * The relation between DLAs and LBGs was subsequently the subject of several studies ( Fynbo et al. 1999; Bunker et al. 1999; Warren et al. 2001; Møller et al. 2002; Weatherley et al. 2005; Rauch et al. 2008 ) and it was found that the difference between the two sets of galaxies can be understood from their very different selection functions (gas cross-section vs. UV luminosity selection).
 * DLA galaxies at z > 2 follow similar relations between metallicity and other fundamental galaxy parameters like luminosity, stellar mass, and SFR ( Møller et al. 2004; Ledoux et al. 2006; Fynbo et al. 2008; Pontzen et al. 2008; Prochaska et al. 2008; Krogager et al. 2012 ).


 * The radiation produced by the cooling of diffuse gas, on the other hand, is very diﬃcult to observe directly because of its very low surface brightness (e.g. Furlanetto et al. 2003, 2004, 2005; Yoshikawa et al. 2003; Fang et al. 2005; Bertone et al. 2010a,b, 2011; Goerdt et al. 2010; Faucher-Giguere et al. 2010; van de Voort & Schaye 2012; van de Voort 2012 )

Strong Lensing Systems

 * Study of strongly-lensed gravitationally lensed galaxies helps high-redshift studies in two ways.
 * First the ﬂux ampliﬁcation enables spectra of higher resolution and increased signal to noise, yielding unique constraints on the absorbing gas ( Pettini et al. 2002, Quider et al. 2009, 2010, Dessauge-Zavadsky et al. 2010 ) and detailed emission line studies of the ionised gas (e.g., Fosbury et al. 2003, Yuan et al. 2009, Hainline et al. 2009, Bian et al. 2010, Rigby et al. 2011, Richard et al. 2011, Wuyts et al. 2012, Brammer et al. 2012 ).
 * Second, the increase in the apparent size of the lensed sources enables characterisation of the internal kinematics and metallicity gradients on scales as small as 100 parsec (e.g., Stark et al. 2008, Swinbank et al. 2009, Jones et al. 2010a, 2010b, 2012b ).

Halo

 * In the modern Lambda Cold Dark Matter (LCDM) paradigm of galaxy formation, dark matter halos form via the continuous accretion of diffuse material, as well as mergers of smaller dark matter halos over time (e.g., Stewart et al. 2008; Fakhouri & Ma 2009; Diemer et al. 2012)

Models v.s Observations

 * Cooling Crisis: Gas cools radiatively during the hierarchical buildup of the halo population and condenses to form galaxies in halo cores, results in more massive galaxies than observed (Balogh et al. 2001; Lin & Mohr 2004; Tornatore et al. 2003 )
 * Additional source of non-gravitational heating to prevent a cooling crisis (White & Rees 1978; Cole 1991; White & Frenk 1991; Blanchard et al. 1992 )
 * Stellar feedback seems not enough (Borgani et al. 2004 )
 * People started considering AGN feedback (Churazov et al. 2002; Springel et al. 2005a; McNamara & Nulsen 2007 )
 * Which resulted in the improvement on:
 * luminosity-temperature relation of X-ray clusters (Valageas & Silk 1999; Bower et al. 2001; Cavaliere et al. 2002 )
 * luminosity function of galaxies (Croton et al. 2006; Bower et al. 2006; Somerville et al. 2008 ) [arXiv:1212.4131]

Inter-Stellar Medium

 * HI has long been the best tracer of Dark Matter (DM) in galaxies (e.g. Bosma 1981; van der Hulst et al. 1993).
 * Typically the projected DM surface density scales very well with the measured HI surface density (Bosma 1981; Sancisi 1983; Carignan & Beaulieu 1989; Carignan et al. 1990; Carignan & Puche 1990a,b; Jobin & Carignan 1990; Broeils 1992; Meurer et al. 1996; Hoekstra et al. 2001). [arXiv:1212.1502]

IGM and CGM

 * Cold and hot-mode accretion (e.g. Binney 1977; Birnboim & Dekel 2003; Keres et al. 2005; Ocvirk et al. 2008; Keres et al. 2009; Faucher-Giguere et al. 2011; Van De Voort et al. 2011 )
 * Observational identification of these cold stream could be hard due to low covering facter (3%-10% at z~2) (e.g Faucher-Giguere et al. 2011; Kimm et al. 2011 )
 * The cold streams at high-redshift contribute significantly to the observed population of Lyman-limit systems (Fumagalli et al. 2011 )


 * From the observed mass-metallicity relation and enrichment of the IGM, it is also clear that the baryons must have at one point entered galaxy halos and disks and been enriched, then were ejected ( Tremonti et al. 2004; Erb et al. 2006; Aguirre et al. 2001; Pettini et al. 2003; Songaila 2005; Martin et al. 2010 ) [arXiv:1301.0841]

Magnetic Field in Galaxies

 * In galaxies, magnetic fields are suspected to be particularly important as here the magnetic pressure in the inter-stellar medium (ISM) becomes comparable to the thermal pressure. Magnetic fields may hence be dynamically relevant for the evolution of galaxies (Beck 2009) [arXiv:1212.1452]


 * The structure and strength of magnetic fields in galaxies determines the propagation of cosmic rays (Strong & Moskalenko 1998; Narayan & Medvedev 2001)


 * Magnetic field strengths have been measured for a number of galaxies using:
 * Zeeman splitting in maser emission (Robishaw et al. 2008)
 * Radio Polarization measurements (Beck 2007)


 * The formation and amplification of magnetic field during galaxy formation (For recent review: Kulsrud & Zweibel 2008)
 * Weak initial magnetic field could be cosmological origin, or were created by Biermann batteries.
 * Further amplification can then proceed through:
 * Structure formation flows (Dolag et al. 1999)
 * Galactic Dynamo (Hanasz et al. 2004)
 * Turbulent amplification (Arshakian et al. 2009)

Extragalactic Background Light

 * The extragalactic background light (EBL), the diffuse, isotropic background radiation from far-infrared (FIR) to ultraviolet (UV) wavelengths, is believed to be predominantly composed of the light from stars and dust integrated over the entire history of the Universe (see Dwek & Krennrich 2012, for reviews). [arXiv:1212.1683]
 * The observed spectrum of the local EBL at z = 0 has two peaks of comparable energy density. The ﬁrst peak in the optical to the near-infrared (NIR) is attributed to direct starlight, while the second peak in the FIR is attributed to emission from dust that absorbs and reprocesses the starlight.
 * Measurements of EBL zt z~0 in optical and NIR is hampered by zodiacal light (Hauser & Dwek 2001); but see Matsuoka et al. 2011 for measurement from Pioneer 10/11.
 * Integration over galaxy number counts provide a ﬁrm lower bound on the EBL, and the observed trend of the counts with magnitude indicates that the EBL at z = 0 has been largely resolved into discrete sources in the optical/NIR bands (e.g. Madau & Pozzetti 2000; Totani et al. 2001; Keenan et al. 2010)
 * The EBL can also be probed indirectly through observation of high-energy gamma rays from extragalactic objects (Mazin & Raue 2007)
 * Observations of blazars by current ground-based telescopes have been able to place relatively robust upper limits to the EBL at z=0 and up to z~0.5 (e.g. Aharonian et al. 2006a; Albert et al. 2008).
 * Theoretical Models for EBL:
 * Backward evolution model: Malkan & Stecker 1998; Totani & Takeuchi 2002; Stecker et al. 2006; Franceschini et al. 2008
 * Forward evolution model: Kneiske et al. 2004; Finke et al. 2010
 * Semi-analytical Models of Hierarchical Galaxy Formation


 * The EBL in the X-ray, or cosmic X-ray background (CXB), is now known to be the relic emission of cosmic supermassive black hole (SMBH) accretion (e.g. Comastri et al. 1995) [arXiv:1212.3642]

Really High-Redshift Universe

 * Molecular hydrogen has been invoked as a signiﬁcant coolant of primordial gas leading to the formation of ﬁrst stars and galaxies (e.g. Haiman 1999; Bromm & Larson 2004; Glover 2005; Glover 2012 ) [arXiv:1212.2964]

Galaxies in Really High-Redshift

 * About the recent development in the luminosity function of galaxies at z~7-8, see Schenker et al. 2012 (arXiv:1212.4819) for a review. This work is based on HUDF12 results.


 * There is now overall evidence for the mass build-up of early galaxies at z~4-8 based on the evolution of the cosmic star-formation density ( Giavalisco et al. 2004, Bouwens et al. 2004, 2007, Bunker et al. 2004, McLure et al. 2006, 2009, Yan et al. 2006, 2010, Castellano et al. 2010, Oesch et al. 2010b ) [arXiv:1212.1448]


 * A wider variety of results have been obtained on the ultraviolet spectral slopes and stellar populations of these early star-forming galaxies at z~7-8 ( Bouwens et al. 2009, 2010, 2012, Ono et al. 2010, Bunker et al. 2010, Finkelstein et al. 2010, 2012b,a, Yan et al. 2011b,a, McLure et al. 2010, 2011, Grazian et al. 2011, 2012, Bradley et al. 2012, Dunlop et al. 2012a,b; Schenker et al. 2012; Lorenzoni et al. 2013 ) [arXiv:1212.1448]


 * About Lyman-alpha Emission:
 * The potential of HI Lyα to identify young galaxies at high redshift was noted over 40 years ago by Partridge & Peebles (1967).
 * In the absence of dust, the Lyα/Hα line intensity ratio is expected to be in the range 7 − 12 for recombination theory cases B-A ( Osterbrock & Ferland 2006 )
 * Due to its resonant nature, a Lyα photon is absorbed and re-emitted multiple times in HI. Resonant trapping reduces the mean free path of the Lyα photons increasing signiﬁcantly their probability of being destroyed by dust, shifted in frequency, or transformed to two-photon emission.
 * On the other hand, some eﬀects are favorable to the escape of Lyα photons from galaxies:
 * Neutral gas outﬂows Doppler-shift the Lyα photons from the optically thick line core to the optically thin line wings making it possible for some Lyα photons to escape ( Kunth et al. 1998; Verhamme et al. 2006 )
 * Lyα photons may also escape through holes of suﬃciently low dust and HI column densities ( Giavalisco et al. 1996; Atek et al. 2009 ).
 * In principle, after removing the observational and astrophysical biases, Lyα can be used for various applications.
 * To probe cosmic star formation rates ( Kudritzki et al. 2000; Fujita et al. 2003; Gronwall et al. 2007; Zheng et al. 2012 ).
 * To probe the ionization fraction of the intergalactic medium during the ﬁnal stages of re-ionization ( Kashikawa et al. 2006; Malhotra & Rhoads 2006; Dawson et al. 2007; Zheng et al. 2010; Bradac et al. 2012 ).
 * To probe the large-scale structure ( Ouchi et al. 2001, 2003, 2004, 2005; Venemans et al. 2002, 2004; Wang et al. 2005; Stiavelli et al. 2005; Gawiser et al. 2007 ).
 * To identify potential hosts of population III star formation ( Malhotra & Rhoads 2002; Shimasaku et al. 2006; Schaerer 2007 ).
 * And to constrain the nature and evolution of highredshift galaxies: Giavalisco (2002); Nilsson et al. (2007); Finkelstein et al. (2009); Shapley (2011); Malhotra et al. (2012); Gonzalez et al. (2012).

Reionization

 * About the calculation of escape fraction in high-z galaxies, see Benson et al. 2012


 * The Gunn–Peterson test, in which a non-trivial ion fraction creates a trough by line absorption at every redshift (Gunn & Peterson 1965), is the most direct test of the later stages of helium reionization. [arXiv:1212.1502]


 * Existing cosmological observations show that the reionization history of the universe at z > 6 is likely both complex and inhomogeneous (e.g. Haiman 2003; Choudhury & Ferrara 2006; Zaroubi 2012 )
 * When does the reionization started: from the polarization signal of the CMB anisotropy power spectrum, the total optical depth to electron scattering suggest it started around $$z_{ri}=11$$ ( Komatsu et al. 2011 )
 * Other possible probes:
 * 21-cm HI spin-flip line: Madau et al. 1997; Loeb & Zaldarriaga 2004; Santos et al. 2005; Santos & Cooray 2006; McQuinn et al. 2006; Bowman et al. 2007; Mao et al. 2008
 * Line emission associated with atomic and molecular:
 * CO: Gong et al. 2011
 * CII: Gong et al. 2012a
 * Lyman-alpha: Silva et al. 2012
 * H_2: Gong et al. 2012b (astro-ph:1212.2964)
 * More sensitive to the late stages of reionization (Righi et al. 2008; Visbal & Loeb 2010; Carilli 2011; Lidz et al. 2011 )


 * The reionization epoch of singly ionized helium (He II) is believed to start at redshifts z~3.5–4 and be nearly complete by z≃2.7 (Furlanetto & Oh 2008)
 * delayed because of the need for high-energy photons than stars provide (E>4 ryd)
 * This is consistent with redshift estimates from the intergalactic medium (IGM) temperature (e.g., Becker et al. 2011), which increases noticeably during helium reionization, as well as estimates from the redshift evolution of the He II Gunn–Peterson optical depth (e.g., Syphers et al. 2011a, 2012; Worseck et al. 2011; but see Davies & Furlanetto 2012) [arXiv:1212.1502]

Population III

 * Coincidently, the footprint of both PopIII star formation and gas cooling during gravitational accretion is the presence of Lyαλ 1216 and HeII λ 1640 emission lines in the spectra of the sources. Dual Lyαλ 1216 and He II λ 1640 emitters have been proposed by various authors as candidates hosting PopIII star formation ( Tumlinson et al. 2001; Schaerer 2003; Raiter, Schaerer & Fosbury 2010 ) [arXiv:1212.5270]
 * Strong Lyα+He II emission lines are commonly found in other astrophysical objects, such as Wolf-Rayet stars (W-R), AGN and supernovae driven winds. However, several diagnostics can be used to distinguish cooling radiation and PopIII star formation from these other mechanisms: AGN, W-R stars and emitters powered by supernovae driven winds typically show other emission lines in their spectra, such as CIII and CIV ( Reuland et al. 2007; Leitherer et al. 1996; Allen et al. 2008 ).
 * Moreover, W-R stars are associated with strong winds, and thus produce broad emission lines (a few 1000 km/s, Schaerer 2003 )
 * Brinchmann, Pettini & Charlot (2008) showed that the broad He II emission detected in the composite spectrum of z~3 galaxies by Shapley et al. (2003) can indeed be reproduced by W-R models.
 * Nebular He II emission also appears in some star forming regions in which the source of ionisation is not clearly identiﬁed as WR or O stars, but this is a rare event in the local universe ( Kehrig et al. 2011 )


 * The high Jeans mass of metal-free gas suggests a top-heavy IMF ( Abel et al. 2000; Bromm et al. 1999; Abel et al. 2002; Yoshida et al. 2003 ) for Population III stars (Pop-III) [arXiv:1212.1157]


 * Pop-III stars may lead to the occurrence of pair instability supernovae (PISNe) ( Heger & Woosley 2002 ) [arXiv:1212.1157]

HST Deep Fields

 * Hubble Deep Field (Williams et al. 1996)
 * Hubble Deep Field South (Casertano et al. 2000; Williams et al. 2000; Lucas et al. 2003)
 * Ultra-Deep Field (Beckwith et al. 2006; Thompson et al. 2005)
 * Following programs in 2005, PI.: M. Stiavelli, see Oesch et al. 2007; 2009
 * WFC3/IR follow-up in 2009, PI.: G. Illingworth, see Oesch et al. 2010a,b; Bouwens et al. 2011b
 * UDF12, PI.: R. Ellis, see Ellis et al. 2012; Koekemoer et al. 2012

Other Shallower HST Surveys

 * GOODS: (''Giavalisco et al. 2004)
 * GEMS : (''Rix et al. 2004)
 * AEGIS: (''Davis et al. 2007)
 * COSMOS: (Scoville et al. 2007; Koekemoer et al. 2007)
 * WFC3 ERS: (Windhorst et al. 2011)
 * CANDELS (Grogin et al. 2011; Koekemoer et al. 2011)
 * BoRG: (Trenti et al. 2011)
 * HIPPIES: (Yan et al. 2011b)
 * CLASH: (Postman et al. 2012)

Clustering of Galaxies

 * The two-point correlation function (along with is Fourier transform the power spectrum) is the most widely used statistic (e.g. Peebles 1980; Baumgart & Fry 1991; Martinez 2009 )
 * Nevertheless, the two-point correlation function represents a full description only in the case of a Gaussian distribution for which all higher-order connected moments vanish by definition. It is well known that the actual galaxy distribution is non-Gaussian (e.g. Fry & Peebles 1978; Sharp et al. 1984; Szapudi et al. 1992; Bouchet et al. 1993; Gaztanaga 1994 ).
 * Such a non-Gaussianity is already induced by nonlinear gravitational amplification of mass fluctuations, even if they originated from an initial Gaussian field (e.g. Peebles 1980; Fry 1984; Juszkiewicz et al. 1993; Bernardeau et al. 2002 )


 * First statistical studies of galaxy clustering: (Totsuji & Kihara 1969; Peebles 1973; Hauser & Peebles 1973, 1974; Peebles 1974 ) found the galaxy correlation function behaves like a power law, which is difficult to explain from first principle (Berlind & Weinberg 2001 )
 * Recent studies found deviations from a power law (Zehavi et al. 2005a),, and the deviation can be explained by a 3-parameter Halo Occupation Distribution model (e.g. Jing, Mo & Borner 1998; Ma & Fry 2000; Peacock & Smith 2000; Seljak 2000; Scoccimarro et al. 2001; Berlind & Weinberg 2001; Cooray & Sheth 2002 )
 * This deviation (a dip in the Correlation Function at 1-3$$h^{-1}$$Mpc) can be explained by the transition from the 1-halo to 2-halo term in the HOD model.
 * The deviation is larger for highly clustered bright galaxies (Zehavi et al. 2005a,b; Blake, Collister & Lahav 2008; Zheng et al. 2009; Zehavi et al. 2010 ), and at high redshift (Conroy, Wechsler & Kravtsov 2006 ), which agrees with theoretical predictions (Watson et al. 2011 ). [arXiv:1212.3610]


 * HOD modelling has been applying to galaxy clustering data from :
 * 2dFGRS: (Porciani, Magliocchetti & Norberg 2007; Tinker et al. 2006 )
 * SDSS : (van den Bosch, Yang & Mo 2003; Magliocchetti & Porciani 2003; Zehavi et al. 2005a,b; Tinker et al. 2005; Yang et al. 2005, 2008; Zehavi et al. 2010 )
 * VVDS (Abbas et al. 2010); Bootes (Brown et al. 2008); DEEP2 (Coil et al. 2006); LBGs in GOODS (Lee et al. 2006)


 * The measurements of the cosmological parameters heavily rely on accurate measurements of power spectra. Power spectra describe the spatial distribution of an isotropic random ﬁeld, deﬁned as the Fourier transform of the spatial correlation function. [arXiv:1212.3194]


 * The dependence of galaxy clustering on galaxy properties has been observed in numerous galaxy surveys (e.g., Davis & Geller 1976; Davis et al. 1988; Hamilton 1988; Loveday et al. 1995; Benoist et al. 1996; Guzzo et al. 1997; Norberg et al. 2001, 2002; Zehavi et al. 2002, 2005b, 2011; Budav´ari et al. 2003; Madgwick et al. 2003; Li et al. 2006; Coil et al. 2006, 2008; Meneux et al. 2006, 2008; Wake et al. 2008; Swanson et al. 2008; Meneux et al. 2009; Ross & Brunner 2009; Skibba et al. 2009; Loh et al. 2010; Ross et al. 2010, 2011a; Wake et al. 2011; Christodoulou et al. 2012; Mostek et al. 2012) [arXiv:1212.1211]


 * The subhalo abundance matching (SHAM) method makes use of subhalos in high resolution N-body simulations and connects them to galaxies to interpret galaxy clustering (see, e.g., Kravtsov et al. 2004; Conroy et al. 2006; Guo et al. 2010; Nuza et al. 2012). [arXiv:1212.1211]


 * The halo occupation distribution (HOD) framework (see e.g., Peacock & Smith 2000; Seljak 2000; Scoccimarro et al. 2001; Berlind & Weinberg 2002; Berlind et al. 2003; Zheng et al. 2005) or the closely related conditional luminosity function (CLF) method (Yang et al. 2003, 2005) describe the number of galaxies as a function of halo mass, and galaxy clustering is used to constrain the HOD or CLF parameters. [arXiv:1212.1211]

Weak Lensing

 * Weak gravitational lensing by large-scale structure provides valuable cosmological information, especially since weak lensing is sensitive to the distance-redshift relation and the time-dependent growth of structure, it is a particularly useful tool for constraining models of dark matter. (Bartelmann & Schneider 2001; Albrecht et al., 2006; Peacock et al., 2006; Albrecht et al., 2009 )
 * To constrain the dark energy, lensing signal must be measured at several redshifts--the so called weak lensing tomography (Hu 1999; Huterer 2002; Bacon et al. 2005; Semboloni et al. 2006; Massey et al. 2007; Schrabback et al. 2010 )

Cosmic Microwave Background

 * At z=0, $$T_0=2.72548\pm0.00057$$ K ( Fixsen 2009 )


 * Studies of the cosmic microwave background (CMB) have dramatically progressed over the past two decades (e.g., Smoot et al. 1992; Cheng et al. 1997; Baker et al. 1999; Miller et al. 1999; de Bernardis et al. 2000; Knox & Page 2000; Hanany et al. 2000; Lee et al. 2001; Romeo et al. 2001; Nettereld et al. 2002; Halverson et al. 2002; Kovac et al. 2002; Carlstrom et al. 2003; Pearson et al. 2003; Scott et al. 2003; Benot et al. 2003; Spergel et al. 2003; Johnson et al. 2007; Chiang et al. 2010 )


 * The current generation of arcminute resolution cosmic microwave background (CMB) experiments is providing researchers with a precise view of CMB anisotropies over a range of scales (500 < ℓ < 10000).
 * Over the so-called Silk damping tail of the CMB (500 < ℓ < 3000) these observations are revealing the subtle eﬀects that inﬂationary physics, primordial helium density and the energy density in relativistic degrees of freedom have on the acoustic oscillations in the photon-baryon plasma in the radiation-dominated era.
 * On smaller scales (ℓ > 3000) the primordial CMB signal diminishes and emission from radio galaxies and dusty star forming galaxies, as well as the thermal and kinematic Sunyaev-Zel’dovich eﬀects (Sunyaev & Zeldovich 1972) arising from the scattering of CMB photons by hot gas in galaxy clusters, dominate the power spectrum.[arXiv:1301.1037]

Measurement at high-redshift

 * Measuring the CMB temperature at high redshift has considerable cosmological interests, in:
 * Demonstrating that the CMB radiation is universal (Equivalence principle)
 * Tracing the evolution of its temperature with redshift, $$T_{CMB}(z)$$. Adiabatic expansion predicts that the CMB temperature evolution is proportional to (1+z). Alternative cosmologies, such as decaying dark energy models (e.g. Lima 1996; Lima et al. 2000; Jetzer & Tortora 2011 ) where dark energy can interact with matter via creation of photons, aﬀecting the CMB spectrum.
 * Two methods can be used to probe the CMB temperature at z>0.
 * The ﬁrst one is based on multi-frequency Sunyaev-Zeldovich (S-Z) observations toward galaxy clusters (see e.g. Horellou et al. 2005; Battistelli et al. 2002; Luzzi et al. 2009; de Martino et al. 2012 )
 * spectroscopic studies of lines in absorption against quasars and their excitation analysis. Most of the measurements at high redshift have used UV spectroscopy of atomic species (CI: Meyer et al. 1986; Songaila et al. 1994b; Ge et al. 1997; Roth & Bauer 1999; CII: Songaila et al. 1994a; Lu et al. 1996; Molaro et al. 2002; CI & CII: Srianand et al. 2000 )
 * Strictly speaking, these measurements are all upper limits on T_CMB, as the contributions from other local sources of excitation (collisions, local radiation ﬁeld) are yet largely uncertain and poorly constrained, and have to be accounted for.

S-Z Effect of Galaxy Cluster

 * Within the last few years, cluster surveys exploiting the Sunyaev-Zel’dovich effect (SZ; Sunyaev & Zel’dovich 1970 ) have also begun to deliver cluster samples (e.g., Staniszewski et al. 2009; Marriage et al. 2011; Williamson et al. 2011; Planck Collaboration 2011a; Reichardt et al. 2012b ) and constraints on cosmological parameters ( Vanderlinde et al. 2010; Sehgal et al. 2011; Benson et al. 2011; Reichardt et al. 2012b ).
 * Since the SZ signal is not diminished due to luminosity distance, it is nearly redshift independent; in principle SZ surveys can detect all clusters in the Universe above a mass limit set by the survey noise level (e.g., Birkinshaw 1999; Carlstrom et al. 2002 ).
 * Although current SZ cluster samples are small in comparison to existing X-ray and optical cluster catalogs, they provide very powerful complementary probes because they are sensitive to the high mass, high redshift cluster population (e.g., Brodwin et al. 2010; Foley et al. 2011; Planck Collaboration 2011b; Menanteau et al. 2012a; Stalder et al. 2012 ).

Dark Matter Halo Simulation

 * Simulations of individual dark matter halos have provided evidence for the inside-out growth of halos in a Lamda-CDM cosmological model. These studies have shown that the inner few tens of kpc remain almost unchanged since high redshift both in massive halos (e.g. Loeb & Peebles 2003; Gao et al. 2004 ) and in halos expected to host Milky-Way sized galaxies ( Wechsler et al. 2002; Diemand et al. 2007; Wang et al. 2011 ).
 * From studying the mass-concentration relation of halos in cosmological simulations, it has become clear that the central density of haloes is correlated with their epoch of formation, which provides additional evidence for inside-out growth ( Bullock et al. 2001a; Wechsler et al. 2002; Zhao et al. 2003 ).


 * While the acquisition of angular momentum in dissipation-less N-body simulations has been well studied (e.g., Bullock et al. 2001; Vitvitska et al. 2002; Maller et al. 2002; D’Onghia & Navarro 2007; Avila-Reese et al. 2005; Bett et al. 2007, 2010 ), our understanding of the extent to which gas behaves in the same manner has only recently started to be explored computationally ( Chen et al. 2003; Sharma & Steinmetz 2005; Brook et al. 2010; Kimm et al. 2011; Pichon et al. 2011; Sharma & Nath 2012 )
 * Recent simulations find that the gas in galactic disks has higher spin than that of the dark matter ( Chen et al. 2003; Sharma & Steinmetz 2005; Brooks et al. 2011 ) in agreement with the model of Maller & Dekel (2002).

Tidal Stripping and Merging

 * When dark matter haloes merge, these protogalaxies also merge; depending on the mass ratio the satellite galaxy can either rapidly merge with the central object or orbit around it for a consistent amount of time (e.g., Chandrasekhar 1943; Binney & Tremain 2008; Jiang et al. 2008; Boylan-Kolchin et al. 2008 )
 * About the possible progressive mass loss, both in dark matter and stellar component (e.g. Mayer et al. 2001a; Klimentowski et al. 2007; Penarrubia et al. 2008; Kazantzidis et al. 2011 )
 * N-body simulations about this topic: ( Moore et al. 1999; Gnedin 2003; Mastropietro et al. 2005; Mayer et al. 2001a, b; Klimentowski et al. 2009a; Kazantzidis et al. 2011; Villalobos et al. 2012; Chang et al. 2012 ) [arXiv:1212.3408]


 * Environmental effects (e.g. tides and stripping) have an important role in shaping the properties of the local dwarf spheroidal galaxies (e.g., Einasto et al. 1974; Faber & Lin 1983; Mayer et al. 2001a, 2001b; Kravtsov et al. 2004; Mayer et al. 2006, 2007; Klimentowski et al. 2007; Penarrubia et al. 2008; Klimentowski et al. 2009a, 2009b )


 * Using this new MHD code (+AREPO), we simulate the formation of isolated disk galaxies similar to the Milky Way using idealized initial conditions with and without magnetic fields. We found that the magnetic field strength is quickly amplified in the initial central starburst and the differential rotation of the forming disk, eventually reaching a saturation value. At this point, the magnetic field pressure in the interstellar medium becomes comparable to the thermal pressure, and a further eficient growth of the magnetic field strength is prevented. The additional pressure component leads to a lower star formation rate at late times compared to simulations without magnetic fields, and induces changes in the spiral arm structures of the gas disk. [arXiv:1212.1452]