Nature and nurture a theoretical perspective Gabriella De
“Nature” and “nurture” a theoretical perspective Gabriella De Lucia INAF – Astronomical Observatory of Trieste
The morphology-density relation “There are some indications of a correlation between characteristic type and compactness, the density of the cluster diminishing as the most frequent type advances along the sequence of classification” Hubble, “The Realm of the Nebulae”, 1936 Heredity or Nature against Nurture or Environment Dressler 1980 R [Mpc] projected density INAF – Astronomical Observatory of Trieste Gabriella De Lucia, November 5, Bologna
Outline ✔ Techniques we use to model galaxy formation in a cosmological framework (limits & aims) ✔ Overview of the most relevant physical processes, and of their relative importance at different masses, times, and environments ✔ Critical review of recent progress and open issues. ✔ The role of “heredity” ✔ A brief presentation of the project(s) ongoing in a new group recently formed in Trieste INAF – Astronomical Observatory of Trieste Gabriella De Lucia, November 5, Bologna
A premise ✔ Theoretical (and observational) studies trying to assess the influence of the environment on galaxy evolution have mostly focused on galaxy clusters (“good laboratories”, “easy” to find, etc) INAF – Astronomical Observatory of Trieste Gabriella De Lucia, November 5, Bologna
A premise ✔ Theoretical (and observational) studies trying to assess the influence of the environment on galaxy evolution have mostly focused on galaxy clusters (“good laboratories”, “easy” to find, etc) ✔ Clusters are biased environments and represent rare objects. In addition, in order to really establish if some cluster-dependent physics is playing a role, one would need to establish a difference between the evolution of galaxies in clusters and that of identical galaxies in the field. INAF – Astronomical Observatory of Trieste Gabriella De Lucia, November 5, Bologna
A premise ✔ Theoretical (and observational) studies trying to assess the influence of the environment on galaxy evolution have mostly focused on galaxy clusters (“good laboratories”, “easy” to find, etc) ✔ Clusters are biased environments and represent rare objects. In addition, in order to really establish if some cluster-dependent physics is playing a role, one would need to establish a difference between the evolution of galaxies in clusters and that of identical galaxies in the field. ✔ If we live in a hierarchical Universe, then structure grows hierarchically. In this framework, a simple distinction between “nature” and “nurture” is difficult to accommodate and both are likely playing a role in determining the observed environmental dependences INAF – Astronomical Observatory of Trieste Gabriella De Lucia, November 5, Bologna
Cooling (metallicity, halo structure, conductivity) Dust (formation, distribution, heating and cooling) Star formation (threshold, efficiency, initial mass function) GALAXY FORMATION SN Feedback (IGM heating, IGM enrichment, efficiency, winds) BHs and AGNs (BH growth, quasar winds, radio bubbles) INAF – Astronomical Observatory of Trieste Mergers and Galaxy interactions (morphological transformations, induced star formation) Stellar evolution (spectro-photometric evolution, yields, feedback) Gabriella De Lucia, November 5, Bologna
Dark matter haloes & galaxies #1 ✔ Halo occupation models (bypass modeling of physical processes, provide a statistical characterization of the link between DM and galaxies) P(N|M) + spatial distribution Berlind et al. 2002 INAF – Astronomical Observatory of Trieste Gabriella De Lucia, November 5, Bologna
Dark matter haloes & galaxies #2 Roediger & Brueggen (2007) ✔ Hydrodynamical simulations (explicit description of gas dynamics, limited mass and spatial resolution, computational time, “sub-grid” physics) z = 0. 8 Courtesy: Volker Springel INAF – Astronomical Observatory of Trieste Gabriella De Lucia, November 5, Bologna
Dark matter haloes & galaxies #3 z=3. ✔ Semi-analytic models (simple but physically and observationally motivated prescriptions, large dynamic range, fast) Cold Gas Croton et al. 2006 - AGN heating Hot Gas cooling star formation feedback Ejected Gas Stars De Lucia et al. 2004, De Lucia & Blaizot 2007 INAF – Astronomical Observatory of Trieste Kauffmann et al. 1999 re-incorporation z=1. z=0. Gabriella De Lucia, November 5, Bologna
Physical mechanisms Galaxy mergers: WHERE : field + low velocity dispersion groups e. g. Negroponte & White ‘ 82, Barnes & Hernquist ‘ 91, ‘ 96 Mihos & Hernquist ‘ 94, ‘ 96, WHAT : strong internal dynamical response INAF – Astronomical Observatory of Trieste Gabriella De Lucia, November 5, Bologna
Galaxy mergers Toomre & Toomre, 1972 Springel, Ph. D Thesis, 1999 M 51 Mihos 2004 Barnes & Hernquist, 1996 INAF – Astronomical Observatory of Trieste Cox, Ph. D thesis, 2004 Gabriella De Lucia, November 5, Bologna
Galaxy mergers in SAMs Effective # of mergers fraction formation time assembly time redshift Mstar [M h-1] De Lucia et al. 2006 INAF – Astronomical Observatory of Trieste Observational evidence for dry mergers (e. g. van Dokkum 2005) but mergers rates are not accurately measured Gabriella De Lucia, November 5, Bologna
Physical mechanisms Galaxy mergers: WHERE : field + low velocity dispersion groups e. g. Negroponte & White ‘ 82, Barnes & Hernquist ‘ 91, ‘ 96 Mihos & Hernquist ‘ 94, ‘ 96, WHAT : strong internal dynamical response Harassment: WHERE : in massive clusters e. g. Spitzer & Baade ‘ 51, Richstone ‘ 76, Farouky & Shapiro ‘ 81, Moore et al. ‘ 96, Moore et al. ‘ 98 WHAT : some damage but less than mergers – at least on luminous members INAF – Astronomical Observatory of Trieste Gabriella De Lucia, November 5, Bologna
Harassment Mastropietro et al, 2005 INAF – Astronomical Observatory of Trieste Gabriella De Lucia, November 5, Bologna
Physical mechanisms Galaxy mergers: WHERE : field + low velocity dispersion groups e. g. Negroponte & White ‘ 82, Barnes & Hernquist ‘ 91, ‘ 96 Mihos & Hernquist ‘ 94, ‘ 96, WHAT : strong internal dynamical response Harassment: WHERE : in massive clusters e. g. Spitzer & Baade ‘ 51, Richstone ‘ 76, Farouky & Shapiro ‘ 81, Moore et al. ‘ 96, Moore et al. ‘ 98 WHAT : some damage but less than mergers – at least on luminous members Gas stripping: WHERE : in the central regions of clusters e. g. Gunn & Gott ‘ 72, Cowie & Songaila ‘ 77, Nulsen ‘ 82, Quilis et al. ‘ 00 WHAT : suppression of star formation and indirect effect on morphology INAF – Astronomical Observatory of Trieste Gabriella De Lucia, November 5, Bologna
Ram-pressure in SAMs “we find that ram-pressure stripping is not important for colours and star formation rates of galaxies in the cluster core” Okamoto & Nagashima 2003 B-V Lanzoni et al. 2005 “including or neglecting ram-pressure stripping in the model, galaxy properties only show mild variations” INAF – Astronomical Observatory of Trieste r/R 200 Gabriella De Lucia, November 5, Bologna
Physical mechanisms Galaxy mergers: WHERE : field + low velocity dispersion groups e. g. Negroponte & White ‘ 82, Barnes & Hernquist ‘ 91, ‘ 96 Mihos & Hernquist ‘ 94, ‘ 96, WHAT : strong internal dynamical response Harassment: WHERE : in massive clusters e. g. Spitzer & Baade ‘ 51, Richstone ‘ 76, Farouky & Shapiro ‘ 81, Moore et al. ‘ 96, Moore et al. ‘ 98 WHAT : some damage but less than mergers – at least on luminous members Gas stripping: WHERE : in the central regions of clusters e. g. Gunn & Gott ‘ 72, Cowie & Songaila ‘ 77, Nulsen ‘ 82, Quilis et al. ‘ 00 WHAT : suppression of star formation and indirect effect on morphology Strangulation: WHERE : anytime the galaxy falls in a larger system WHAT : suppression of star formation and indirect effect on morphology e. g. Larson, Tinsley & Caldwell ’ 80, Balogh, Navarro & Morris ‘ 00 INAF – Astronomical Observatory of Trieste Gabriella De Lucia, November 5, Bologna
The colour-magnitude bimodality ✔ Tail of blue bright object (despite a “strong” AGN feedback – a “dust” problem? ) ✔ Excess of faint red satellites ✔ Transition region not as well populated as in the observational data Quantitatively, the CM bimodality is not well reproduced (see discussion in De Lucia 2007) INAF – Astronomical Observatory of Trieste Gabriella De Lucia, November 5, Bologna
The stripping of the hot reservoir Strangulation is usually assumed to be instantaneous. Mc. Carthy et al. 2008 Transition from blue cloud to red sequence occurs on very short time -scales (because there is also an efficient feedback from supernovae) Recent numerical studies suggest that the stripping of hot gas occurs on longer time-scales. This can potentially help keeping satellite galaxies active for longer times INAF – Astronomical Observatory of Trieste dark matter gas Gabriella De Lucia, November 5, Bologna
The colours of satellites Assume a noninstantaneous stripping of hot material + this material can cool on satellite galaxies Central galaxies are basically unaffected but a larger fraction of satellites become now bluer (qualitative agreement with obs. data) See also Kang et al. 2008 Font et al. 2008 INAF – Astronomical Observatory of Trieste Gabriella De Lucia, November 5, Bologna
Physical mechanisms - continued WHERE : centre of massive groups/clusters e. g. Tabor & Binney 1993, Churazov et al. ‘ 01, Brueggen et al. ’ 02, Sijacki & Springel ’ 06, +++++++ WHAT : suppression of “cooling flows” INAF – Astronomical Observatory of Trieste Bower et al. 2006 Mc. Namara et al. 2005 Croton et al. 2006 AGN heating: Gabriella De Lucia, November 5, Bologna
Physical mechanisms - continued AGN heating: WHERE : centre of massive groups/clusters e. g. Tabor & Binney 1993, Churazov et al. ‘ 01, Brueggen et al. ’ 02, Sijacki & Springel ’ 06, +++++++ WHAT : suppression of “cooling flows” Cannibalism: WHERE : groups and clusters e. g. Ostriker & Tremaine ‘ 75, White, ‘ 76, Makumuth & Richstone ‘ 84, Merritt ‘ 85 WHAT : formation of BCGs? INAF – Astronomical Observatory of Trieste Gabriella De Lucia, November 5, Bologna
The merger tree of a BCG De Lucia & Blaizot 2007 INAF – Astronomical Observatory of Trieste Gabriella De Lucia, November 5, Bologna
The role of “heredity” Halo properties do depend on the “environment”: ✔ Present day haloes in clusters are on average more concentrated, more spherical, and rotate slower than haloes in the field (e. g. Avila. Reese et al. 2005, Wechsler et al. 2006) ✔ Haloes in high-density environments form earlier and a higher fraction of their mass is assembled during major mergers, compared to haloes in low density environments (e. g. Sheth & Tormen 2004, Maulbetsch et al. 2007) This is bound to leave an “imprint” on galaxies that inhabit different regions today INAF – Astronomical Observatory of Trieste Gabriella De Lucia, November 5, Bologna
The role of “heredity” Gao et al. 2004 INAF – Astronomical Observatory of Trieste De Lucia et al. 2006 Gabriella De Lucia, November 5, Bologna
The role of “heredity” Symbols: objects with M > 1010 M M = 1. 3 x 1011 M MV = -22. 11 B - V = 0. 79 Cluster M = 1. 4 x 1011 M MV = -22. 15 B - V = 0. 77 “Field” Color-coding: B - V INAF – Astronomical Observatory of Trieste Gabriella De Lucia, November 5, Bologna
1 VVDS mock Masses from SED fitting The agreement with the observed mass functions is quite good. No significant deficit rather an excess of faint and intermediate mass galaxies Courtesy: Lucia Pozzetti (see also Stringer et al. 2008) INAF – Astronomical Observatory of Trieste Gabriella De Lucia, November 5, Bologna
Conclusions ✔ Unsurprisingly, both heredity and environment affect galaxy evolution, but what is their relative importance? ✔ Little attention has been devoted so far in “quantifying explicitly the importance of conditions at formation (nature rather than nurture). Not surprising either… this is difficult… ✔ We need to have gain a better understanding about physical processes at the group scale. This is the most common galaxy environment ✔ We also need to improve (and better understand) our definitions of environment INAF – Astronomical Observatory of Trieste Gabriella De Lucia, November 5, Bologna
Tidal stripping of stars Stellar Mass [1010 Msun/h] Saro et al. submitted Tidal stripping of stars (stellar halo, intracluster light) Obs measurements are, unfortunately, very uncertain (from few % to more than 50%!!!) Lookback time [Gyr] INAF – Astronomical Observatory of Trieste Tidal stripping is not the main channel for the production of ICL (Rudick et al. 2006, Murante et al. 2007). Unfortunately, results do not converge. Gabriella De Lucia, November 5, Bologna
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