HWR Princeton, 2005 III. The Growth of Galaxy Disks and the Evolution of Galaxy Sizes Observed galaxies occupy a small fraction of possible structural configurations: size, surface brightness, shapes, etc.. Stability? Initial Conditions? Feed-back during the formation? Present-day structural properties Observed Evolution of Galaxy Structure Comparison to theoretical Expectations

HWR Princeton, 2005 Present-Day Parameter Relations I Spheroids/Ellipticals: the Fundamental Plane Djorgovski and Davis 1987 Dressler et al 1987 Joergensen et al 1996 Any two parameters of r e,I e, predict the 3 rd well Explanation elements: virial theorem quite uniform (M/L) * stars dominate at center (?) Joergensen et al 1996

HWR Princeton, 2005 Present Structural Parameter Relations for Disk Galaxies I: Disk Size vs Mass/Luminosity Galaxy size scales with luminosity/stellar mass At given luminosity/size: fairly broad (log normal) distribution R d ~M * 1/3 Disks Spheroids Disks Spheroids Shen et al 2003 SDSS

HWR Princeton, 2005 What determines sizes of stellar disks? Angular momentum Arising from halo size and spin parameter Dark halo and its adiabatic contraction do matter Peebles 69,Fall+Efstathiou 80 Conversion of gas to stars Toomre64,Kennicutt 98 Internal re-distribution of angular momentum Bar instabilities? Ostriker&Peebles 73, Norman et al 96 Direct disk formation simulations have been largely unsuccessful sub-clump problem Katz 91,Navarro&Steinmetz 90s,etc.. Semi-analytic approaches to disk formation Dalcanton et al 97,Mo, Mao & White 98, van den Bosch 99, Naab&Ostriker 05

HWR Princeton, 2005 Structural Relations for Disks II the Tully-Fisher (1976) relation Tight L B/V vs v circ relation historically exploited for distance estimates Tully-Fisher observations to constrain disk formation –Pizagno et al 2005 –Complement SDSS info with H rotation curves for 250 galaxies –Sample selection: B/D mass < 0.2; all colors Pizagno, Weinberg, Rix, et al 2005

HWR Princeton, 2005 Tully-Fisher and the structure of disks 2-param. relation3-param. relation Maximal disk Only need L (or M * ) to predict V circ (2.2R d ) in disk systems Size does not help to predict V circ Stellar disks in most galaxies sub-maximal v * ~0.6v tot d )

HWR Princeton, 2005 Lets use look-back observations to tackle disk formation

HWR Princeton, 2005 Disk evolution with redshift: What might we expect? Sizes from Initial Angular Momentum (Fall and Efstathiou, 1980) Growth of Halos – Growth of Galaxies (Mo, Mao and White, 1998) R exp (M * ) ~ M * 1/3 x m d -4/3 j d x H (z) - 2/3 When did the presently existing disks form? –1/3 of all stars at z~0 are in disks –40% of all stars (now) have formed since z~1 (mostly in disks) –Majority of the Milky Way disk stars have formed in the last 7Gyrs z~1 z~0 is the most important epoch for building todays stellar disks –Note: higher SFRs at z>0 higher surface brightness(?)

HWR Princeton, 2005 But first: some lore Disk Evolution from high-z to now If stellar (disk) sizes reflect halo size + constant z observation = z formation of halo then R d ~H -1 (z) for fixed v circ (halo) R d ~H -2/3 (z) for fixed Mass(halo) R d ~H -1 (z) R d =const (phys.) R d ~H -2/3 (z) Ferguson et al 2004 GOODS But what is observed? UV-size = f(z) in UV flux-limited sample Agreement likely fortuitous !?

HWR Princeton, 2005 Observing Galaxy Size Evolution How does the currently observed L V -R d, M * -R d, and L V -v c evolve with redshift? Data Sets –GEMS: 2-band HST imaging redshifts ( Barden et al 2005 ) 30x previous samples (Lilly et al 98; Simard et al 99) –FIRES: JHK imaging (0.45) redshifts ( Trujillo et al 2003/5 ) Data/Analysis Issues –Understand the (surface brightness) selection function well –Measure sizes at constant rest-frame wavelength >4000A –Consistent tie-in to z~0 data

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HWR Princeton, 2005 Disks to z~1 in GEMS Sample Selection Barden, Rix et al 2005 n<2.5 Thats our operative definition of disks == low concentration radial profile

HWR Princeton, 2005 Observed color gradients at z~0.5,1.0 2-bands HST images in GEMS check for color-gradients in distant disks Same gradients as local Correction to rest-frame V is straightforward Difference R d (mass) and R d (V) is constant with z Redshift slices from GEMS

HWR Princeton, 2005 Disk Evolution to z~1 from GEMS Data Selection Function GOODS selection box (Ravindranath et al 2004) v =const

HWR Princeton, 2005 How did the surface brightness of disk galaxies evolve since z~1? For luminous galaxies, the mean surface brightness has dropped by 1mag over the last 7Gyrs M V <-20 1 mag Freeman law brighter

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HWR Princeton, 2005 Evolution of the mean surface mass density of disks since z~1 M * >10 10 M o

HWR Princeton, 2005 Redshift Evolution of the Tully-Fisher Relation Barden, Genzel, Lehnert 2005 Expected change in surface brightness from the observed stellar population changes

HWR Princeton, 2005 If r(M) is not f(z) disks grow inside out

HWR Princeton, 2005 Now lets extend this type of analysis to z~3 (FIRES, Trujillo et al 2003/5)

HWR Princeton, 2005 Are there sizeable (disk?) galaxies at high redshift? (Labbe et al 2003; see also Lowenthal et al 1997) M81 At the present, normal disk galaxies look completely different in the UV than in the optical Z spec =2.9 peculiar, or star- forming ring seen in the UV Older / redder bulge / bar?

HWR Princeton, 2005 Are the FIRES data deep enough? (FIRES data, Trujillo et al 2003/5)

HWR Princeton, 2005 V-band Sizes of FIRES Galaxies compared to SDSS (Trujillo et al 2005;Shen et al 2003)

HWR Princeton, 2005 Size-evolution from z~2.5 to z~0 Trujillo et al 2005 At a given (V-band) luminosity, galaxies were about 2.5x smaller at z~2.5 than now. At a given stellar mass, they were only 1.4x smaller than now. Galaxies at high-z were bigger than the naïve halo-scalings lead us to expect! H 2/3 (z)

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HWR Princeton, 2005 But while NFW halos were denser (within the virial radius) at high-z, they had lower concentrations.. (Somerville, Rix, Trujillo, Barden, Bell 2005 in prep.) Simulated Z=3 Z=1

HWR Princeton, 2005 H 2/3 (z)

HWR Princeton, 2005 The Role of Bars Should we expect radial re-distribution due to internal processes? How prevalent/strong were bars in the past? Claim (Abraham et al 1999): Bars only appear at z~0.6 (in HDF) Analysis of bar frequency in GEMS algorithmic bar detection Accounting for (1+z) 4 local comparison sample

HWR Princeton, 2005 Bars in GEMS Jogee, Rix, et al 2004 Abundance and strength of bars seems not to have changed since z~1 In n Sersic <2.5 selected galaxies t bar x N reform > f bar x t Hubble bars long-lived

HWR Princeton, 2005 Summary spheroids and disks at high-z ( ) seem to live on the same locus in the M *,R,( ) plane Evolution of this locus in the L V,R plane, reflects changes in stellar mass-to-light ratio This argues for galaxies evolving along those relations. (?) disks grow inside out, along R(M)~M 1/3 If disks were to grow in mass along with their halos, R d (M) ~ H -1 (z) or H -2/3 (z), we would have expected them to be smaller at high-z than observed.

HWR Princeton, 2005 Open Issues / Next Steps Technicalities: –Get more dynamical masses (vz SED masses) –Exploit the potential of IRAC on Spitzer for rest-frame near- IR selection. –Get much more comprehensive merger rate estimates Avenues –Modelling lagging consideraby behind the wealth of new data –Look-back studies of the environments role in galaxy evolution. –Host galaxies at high-z (vs normal): a key to understanding BH growth

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