Slide 1

Galaxy Formation: Simple or Not? The Cosmic Dark Age Telescope: 6.5 m Infrared Optimized Next Generation Space Telescope to Launch in 2013 (+ . Years) Slide 2 Background Material Cosmological Players Cosmic Time Scale and the Dark Ages Matter-Radiation Coupling/Radiation Drag Galaxy Mean Density as Fundamental Constraint Redshift Age of the Universe Relation Basic Framework of Perturbation Growth Slide 3 Slide 4 Slide 5 Temperatures in the Dark Ages Spin Temperature of H I Kinetic Temperature of Atoms Radiation Field Temperature For a few million years MWB photons absorbed by H and the 3 Temps are equal (gas cant cool) Ten million years after decoupling, radiation field is too dilute and gas can rapidly cool Kinetic and Spin temperatures equal; lower than radiation field (absorption state) 100 million years later atomic collisions diluted and spin temperature lowered until in equilibrium with background radiation When sources appear, spin temperatures warmer again than backgound (emission) Key thing to Observe Slide 6 SKA: Not Yet under construction Slide 7 Slide 8 This Means Purely baryonic fluctuations are smoothed out by radiation drag All fluctuations up to mass 10 12 solar masses are damped out by radiation There can not be larger baryonic fluctuations because those would produce anisotropies in the CMB than are larger than observed Dark Matter Seeds seem required for galaxies to exist Slide 9 Galaxy Mean Density Typical massive galaxy has mean over density of 10 5 Typical massive galaxy has mean over density of 10 5 Background density scales as (1+z) 3 Background density scales as (1+z) 3 Therefore co-moving galaxy density = background at z = 50 Therefore co-moving galaxy density = background at z = 50 Galaxies can not form earlier else their observed mean densities at z=0 would be higher Galaxies can not form earlier else their observed mean densities at z=0 would be higher Slide 10 Age-Redshift Values Precision Age of Universe = 13.7 Gyr Precision Age of Universe = 13.7 Gyr At z = 100 Universe is 13.5 Myr old At z = 100 Universe is 13.5 Myr old At z = 20 Universe is 142 Myr old At z = 20 Universe is 142 Myr old At z = 10 Universe is 375 Myr old At z = 10 Universe is 375 Myr old At z = 5 Universe is 930 Myr old At z = 5 Universe is 930 Myr old At z = 3 Universe is 1.7 Gyr old At z = 3 Universe is 1.7 Gyr old At z = 1 Universe is 4.8 Gyr old At z = 1 Universe is 4.8 Gyr old Slide 11 CMB Anisotropies are well measured now Slide 12 Slide 13 Slide 14 Fluctuations grow faster in the radiation dominated era Dark Matter Seeds greatly facilitate galaxy formation! Slide 15 Reality Check Matter Dominated era: z a(t) 2/3 ; z = 1100 2.7 x 10 -5 Matter Dominated era: z a(t) 2/3 ; z = 1100 2.7 x 10 -5 fluctuations present at decoupling (consistent with WMAP) a(t) ; assume fluctuations in dark matter can start growing at t=10 -15 seconds (z = 10 28 ) ; then fluctuations in dark matter number density of 10 -33 amplify to 10 -5 at recombination implies dark matter halos of 10 66 particles mixed in with 10 68 protons. Radiation Dominated era: z a(t) ; assume fluctuations in dark matter can start growing at t=10 -15 seconds (z = 10 28 ) ; then fluctuations in dark matter number density of 10 -33 amplify to 10 -5 at recombination implies dark matter halos of 10 66 particles mixed in with 10 68 protons. Slide 16 Problems With Simple Model of Monolithic Collapse of Baryons Slide 17 Slide 18 Slide 19 Dynamical Timescales Monolithic Collapse can not occur on faster time scale Monolithic Collapse can not occur on faster time scale For large galaxy, timescale is 2 x 10 8 years For large galaxy, timescale is 2 x 10 8 years Z = 10-20 (obs. Problems) Z = 10-20 (obs. Problems) 500 solar mass per year 500 solar mass per year Huge ionization sources Huge ionization sources We find very few galaxies Composed of purely old stars Slide 20 But 10 11 solar mass Jeans type objects dont exist at recombination 10 11 solar mass Jeans type objects dont exist at recombination This demands merger of subunits to maker larger units bottom up galaxy formation This demands merger of subunits to maker larger units bottom up galaxy formation This takes time and re-ionization/reheating becomes a serious problem This takes time and re-ionization/reheating becomes a serious problem CMB polarization signal suggests re-ionization epoch ends by around z =8 and galaxy collapse might start unimpeded then CMB polarization signal suggests re-ionization epoch ends by around z =8 and galaxy collapse might start unimpeded then Means that a monolithic collapse could reveal itself at z = 6.5 Means that a monolithic collapse could reveal itself at z = 6.5 First candidate object discovered/announced on April 22, 2009 Slide 21 Current Wisdom: Bottom UP Slide 22 NASAs Over Simplification Slide 23 Hubble Data Confirms High Densities of Bulding Blocks Slide 24 Dark Matter Makes Galaxy Formation Possible Purely baryonic fluctuations damp out Purely baryonic fluctuations damp out Dark Matter is not subject to radiation pressure in the Early Universe Dark Matter is not subject to radiation pressure in the Early Universe Dark Matter therefore has several hundred more e-folding times to concentrate itself compared to the baryons Dark Matter therefore has several hundred more e-folding times to concentrate itself compared to the baryons Expect merging of dark matter building blocks into large halos which then capture baryonic material. Expect merging of dark matter building blocks into large halos which then capture baryonic material. Slide 25 Dark and Baryonic Matter Slide 26 Dark Matter Network Slide 27 Now Slide 28 The Detailed Properties of Galaxies Are not so easily reconcilable with the simple dark matter halo + baryons picture Are not so easily reconcilable with the simple dark matter halo + baryons picture Annoying result: BMF = 0.13 +/- way too small Annoying result: BMF = 0.13 +/- way too small Also, why no purely DM galaxies maybe there are (Cortese etal 2008) Also, why no purely DM galaxies maybe there are (Cortese etal 2008) Slide 29 Slide 30 Galaxy Components Slide 31 Wavelength and Structure Slide 32 Slide 33 Interactions Slide 34 The Assembly Process May Still be occurring M31 Pine Mountain Project to map debris in the Local Group XUV Extensions around Galaxies Slide 35 Slide 36 XUV Disks Remarkable New Discovery with GALEX mission Remarkable New Discovery with GALEX mission 30% of all disk galaxies show this XUV phenomenon 30% of all disk galaxies show this XUV phenomenon SF should not be occurring at these radii SF should not be occurring at these radii Very Large UV Disks have Implications for distant Galaxy observations Slide 37 Narrow Band Imaging Hydrogen gas falling into halo at z = 3; Ionized gas glows in the filter that is ON source Lyman-Alpha Imaging Slide 38 The Cosmic Blob Discovered April 2009 in Narrow Band Survey Discovered April 2009 in Narrow Band Survey Presumed to be Lyman-Alpha at z = 6.5 Presumed to be Lyman-Alpha at z = 6.5 First of its kind discovered First of its kind discovered Slide 39 Implications of Himiko Dimensions are similar to size of galactic halo Dimensions are similar to size of galactic halo Mass of ionized gas is very large Mass of ionized gas is very large Good candidate for re-ionization events Good candidate for re-ionization events May be first example of monolithic halo formation (size and mass are about right) May be first example of monolithic halo formation (size and mass are about right) This is a new kind of object (unless its really H-alpha) This is a new kind of object (unless its really H-alpha) Slide 40 Summary We have no understanding of what determines bulge versus disk dominance We have no understanding of what determines bulge versus disk dominance Constancy of BMF very weird; No Dark Haloes weirder Constancy of BMF very weird; No Dark Haloes weirder Nature of DM now very important Nature of DM now very important We are actively searching for sources of re-ionization We are actively searching for sources of re-ionization We do understand a lot about galaxy modification via their interacting environment still ongoing We do understand a lot about galaxy modification via their interacting environment still ongoing No idea still, when, in redshift space/time the first bound objects with baryons in them really formed No idea still, when, in redshift space/time the first bound objects with baryons in them really formed If Himiko is real this is a major challenge to Bottom Up scenario. If Himiko is real this is a major challenge to Bottom Up scenario.