High-Redshift Galaxies IV! - Galaxy Main Sequence : Relevance! - Star Formation Law, Gas Fractions! - First Light and Reionization!

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1 Dec 02, 2015! High-Redshift Galaxies IV! - Galaxy Main Sequence : Relevance! - Star Formation Law, Gas Fractions! - First Light and Reionization! HII HI! An electronic version of your final paper is due Dec 10! Remember: the content should be at least ~60% on the science!

2 The star formation main sequence of galaxies! The general high-redshift galaxy population:! BzK, BX/BM, LBG-selected galaxies ( typical / normal ), SMGs ( starbursts )! - There appears to be a relation between SFR and M * for actively starforming galaxies, a main sequence (MS) of star formation! - passive galaxies fill the triangular region below! - Merger-driven starbursts deviate from the MS (few times higher SFR)! - The normalization appears to evolve with redshift towards higher SFR! (caution: there are some mergers/starbursts on the MS, but they are a minority)! Daddi et al. 2007, Noeske et al. 2007!

3 Physical relevance of the star formation main sequence of galaxies! - where disk galaxies are located at high z! - 90% of cosmic star formation out to z~2 occurs on main sequence! - MS galaxies have typically high duty cycles, are mostly not starbursts (but they can have high SFRs)! Herschel/PACS! e.g., Adelberger et al. 2004, Noeske et al. 2007, Daddi et al. 2007, Foerster Schreiber et al. 2009, 2012, Rodhigiero et al. 2011, Wuyts et al. 2012!

4 Evolution of the Main Sequence! Specific SFR:! ssfr = SFR/M *! Comparison of 25 studies in the literature (Speagle et al undergrad student):! - MS is constrained out to z~6! - When putting all on a common calibration scale, remarkable agreement! - Width of the MS: remarkably narrow, 0.2 dex! - Slope and normalization of the MS: both are likely time-dependent:! SFR(M *, t cos ) = (0.84 ± ± " t cos )log M * - (6.51 ± ± 0.03 " t cos ),! where t cos is the age of the universe in Gyr!

5 Galactic star formation in equilibrium with cosmic accretion & outflows! e.g., Keres et al. 2005, 2009, Guo et al. 2009, Oppenheimer & Dave 2006, Dekel et al. 2009, Dave et al. 2010!

6 Simplest Version of Star Formation Law : Spatially Integrated Observables L CO vs. L FIR as a surrogate for M gas vs. SFR One super-linear relation or Two sequences (quiescent/starburst) Bimodal or running conversion factor many subtleties, but: High-z galaxies higher on both axes Quiescent and Starburst Galaxies Carilli & Walter 2013 ARAA; after Daddi et al. 2010, Genzel et al. 2010!

7 const.? Even main sequence galaxies (defined as typical SFR/M * (z)) show 10-30x higher gas fractions at z=1-3 compared to present day " Increased SF history driven by high gas fractions of galaxies (not by extreme merger rates) Carilli & Walter 2013 ARAA; after Magdis et al. 2012, Tan et al. 2013! " L FIR = L sun is the new normal " L FIR = L sun are high starbursts (SMGs) " Star formation is elevated, but underlying physics are the same " Gas depletion makes z=0 special " Evolution at z>3 poorly known

8 cold gas history of the universe! # SFR # M(gas) Epoch of galaxy assembly! Present day! Stellar Light Stars+Dust?" First galaxies! connection:! star formation law (M gas vs. SF rate)! Star formation law:! SF history of the universe is a reflection of the cold gas history of the universe (gas supply)!! " Studies of galaxy evolution are shifting focus to cold gas (source vs. sink)! " Epoch of galaxy assembly = epoch of gas-dominated disk galaxies?! Problem: populations at high-z so far are highly selected (IR, radio, UV/optical luminosity)! " may miss cold gas rich, quiescent galaxy populations!! solution: unbiased census of molecular gas, the fuel for star formation!

9 Big Bang f(hi) ~ 0! History of Normal Matter (IGM ~ H)! 0.4 Myr Recombination! f(hi) ~ 1! z = 1100 Once the H-atoms form (380,000 yrs), the universe is filled with neutral gas which should emit in the 21 cm line (ground state, spin-flip transition)! Gyr Reionization! z ~ 6 to 12 The universe continues to expand and cool; the gas remains neutral in the absence of any source of ionizing radiation.! 13.8 Gyr f(hi) ~ 10-5! z = 0 Djorgovski/Caltech! Dark Ages : there are no sources of light.! Once the first objects formed, the hydrogen was reionized!! " The Epoch of Reionization!

10 Numerical simulation of the evolution of the IGM! Three phases!! Dark Ages! Isolated bubbles (slow)! Percolation (bubble overlap, fast): cosmic phase transition! 10cMpc F(HI) from z=20 to 5 Mean free path of ionizing photons depends on IGM density structure!! Note: galaxy clustering drives the evolution! (Gnedin & Fan 2006)!

11 Three stages! Pre-overlap Overlap Post-overlap From Haiman & Loeb!

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13 Sources of re-ionization! Population III stars:! Need to seed heavy elements even in first galaxies and oldest Pop II stars! Star formation/nuclear fusion in primordial abundance material different! Very high T: good for re-ionization!! Not yet observed! QSOs:! How do SMBHs form? (One of biggest mysteries is how first QSOs formed)! Are there enough? Perhaps not.! But, good source of high E photons! First galaxies:! Likely the main source: faint, but numerous! Did not yet find enough sources to explain re-ionization, there must be more, faint sources at very high z than we know thus far!

14 Evolution of the IGM neutral fraction: Robertson et al. 2013! 1 Gyr 0.5 Gyr F HI_vol! Ly-!-galaxies Quasar Near-zones Gunn-Peterson

15 Large scale polarization of the CMB! Temperature fluctuations = density inhomogeneities at the surface of last scattering! Polarized = Thomson scattering local quadrupol CMB! WMAP Hinshaw et al. 2008!

16 Large scale polarization of the CMB (WMAP)! Angular power spectrum (~ rms fluctuations vs. scale)! Large scale polarization!! Integral measure of $ e back to recombination! Earlier => higher! e Sachs- Wolfe Baryon Acoustic Oscillations: Sound horizon at recombination! e ~ " T #L ~ (1+z) 3 /(1+z) ~ (1+z) 2! Large scale ~ horizon at z reion l < 10 or angles > 10 o! Weak: $K rms ~ 1% total intensity $ e = / Jarosik et al. 2011, ApJS 192, 14!

17 CMB large scale polarization: constraints on F(HI)! 1-F(HI) " Rules out high ionization fraction at z > 15! " Allows for small ( 0.2) ionization to high z! " Most action at z ~ 8 13! Two-step reionization: 7 + z r! Dunkley ea 2009, ApJ 180, 306!

18 CMB large scale polarization: constraints on F(HI)! F HI_vol!! Systematics in extracting large scale signal!! Highly model dependent: Integral measure of $ e

19 "#$%&'!!()*+,-!.!/0&&'1+-+*,)&!23+4-! \0%,%*,! " "#'!!M)*+,-! " /0&&'1+-+*,)&!+3+4-! "

20 Gunn-Peterson Effect! Ly-! resonant scattering by neutral gas in IGM clouds! Linear density inhomogeneities, & ~ 10! N(HI) = cm -2! F(HI) ~ 10-5! $ 1+ z' " GP # 6x10 5 x HI & ) % 10 ( 3 / 2

21 6.4 Gunn-Peterson effect! SDSS z~6 quasars! Opaque (! > 5) at z>6! " pushing into reionization?! 5.7 SDSS quasars! Fan et al. 2006!

22 Gunn-Peterson constraints! on F(HI)! Diffuse IGM: $ GP = 2.6e4 F(HI) (1+z) 3/2 Clumping: $ GP dominated by higher density regions => need models of #, T, UV BG to derive F(HI)! eff z<4: F(HI) v ~ 10-5 z~6: F(HI) v % 10-4 Becker et al. 2011!

23 Gunn-Peterson constraints on F(HI)! F HI_vol! GP => systematic (~10x) rise of F(HI) to z ~ 5.5 to 6.5! Challenge: GP saturates at very low neutral fraction (10-4 )!

24 Quasar Near Zones! White et al. 2003! J : Host galaxy redshift: z=6.419 (CO + [CII])! HI Quasar spectrum => photons leaking down to z=6.32! HII Time bounded Stromgren sphere (ionized by quasar?)! cf. proximity zone interpretation, Bolton & Haehnelt 2007! z host z GP => R NZ = 4.7Mpc ~ [L & t Q /F HI ] 1/3 (1+z) -1

25 Quasar Near-Zones: 28 GP quasars at z=5.7 to 6.5! L UV R L & 1/3 Carilli et al. 2010! L UV # No correlation of UV luminosity with redshift! # Correlation of R NZ with UV luminosity! Note: significant intrinsic scatter due to local environ., t Q!

26 Quasar Near-Zones: R NZ vs. redshift! [normalized to M 1450 = -27]! <R NZ > decreases by ~10x from z=5.7 to 7.1 z ' 6.4 Carilli et al. 2010! 5Mpc z=7.1 0Mpc <R NZ > decreases by factor ~ 10 from z=5.7 to 7.1! If CSS => F(HI) 0.1 by z ~ 7.1!

27 Highest redshift quasar (z=7.1)! Simcoe et al. 2012! (Bolton et al.; Mortlock et al. 2011)! Damped Ly-! profile: N(HI) ~ 4 x cm -2! Substantially neutral IGM: F(HI) > 0.1 at 2 Mpc distance [or galaxy at 2.6 Mpc along LOS; probability ~ 5%]!

28 Highly Heterogeneous metallicities: galaxy vs. IGM! Z/H < -4 Simcoe et al.! [CII] + Dust detection of host galaxy => enriched ISM, but,! Very low metallicity of IGM just 2 Mpc away! Venemans et al. 2012! [CII] 158 $m Intermittency: Large variations expected during epoch of first galaxy formation!

29 Quasar near zone constraints on F(HI)! F HI_vol! QNZ + DLA => rapid rise in F(HI) z~6 to 7 (10-4 to > 0.1)! Challenge: based (mostly) on one z>7 quasar!

30 Galaxy demographics: effects of IGM on apparent galaxy counts! Ly-!% z=7.1 quasar Ly-!% Typical z~5 to 6 galaxy (Stark et al.) Neutral IGM attenuates Ly-! emission from early galaxies! Search for decrease in:!! Number of Ly-! emitting galaxies at z>6!! Equiv. Width of Ly-! for LBG candidates at z > 6!

31 Galaxy demographics: Ly-! emitters! NB survey COSMOS + GOODS-North! Space density of LAEs decreases faster from z=6 to 7 than expected from galaxy evolution! Expected 65, detected 7 at z=7.3!! Modeling attenuation by partially neutral IGM => F(HI) ~ 0.5 at z ~ 7! Konno et al. 2014! z Ly-! = 7.3!

32 Galaxy demographics: effects of IGM on apparent galaxy counts! Strength of Ly-! from LBGs! LBGs: dramatic drop in Ly-! EW at z > 6! F(HI) > 0.3 at z~8! Tilvi et al. 2014; Treu et al. 2013!

33 Galaxy constraints on F(HI)! LAEs F HI_vol! LBGs Galaxy demographics suggests possibly 50% neutral fraction at z~7!! Challenge: separating galaxy evolution from IGM effects!

34 F(HI): Synergy! 1Gyr 0.5Gyr F HI_vol! Robertson et al. 2013! Amazing progress (paradigm shift): rapid increase in neutral fraction from z~6 to 7 (10-4 to 0.5) = cosmic phase transition?! All values have systematic uncertainties: suggestive but not compelling => Need new means to probe neutral IGM!

35 Summary of Reionization Constraints! Neutral fraction! Quasars! GRBs! Ly-alpha! CMB! Redshift! Zahn et al. 2012!

36 Did Galaxies Re-Ionize the Universe?! (*++!+ '!,4%_+*A&B!)?-J!>+?-E! Robertson et al. 2010! Galaxies seem to have a tough time w/ taking responsibility for the observed ionization state of the universe!

37 What could be responsible for shortfall in photons?! Some component of WMAP opt. depth (~0.02) measurement may be due to first generation of massive stars at z>10, not all has to arise in z>7 galaxies! The faint end slope of the luminosity function could be steeper than we think! Exotic stellar populations (e.g., top heavy IMF?)! High escape fraction f esc of ionizing photons! Faint, sub-sdss/ulas AGN?! " Need detailed studies of z>7 galaxies and populations, down to faint levels in very/ultra/extreme deep fields (H-UDF/XDF, )!

38 HI 21cm line: Most direct probe of the neutral IGM! Low frequencies: z reion ~ 6 to 12 => ' obs = 1420MHz/(1+z)! = 110MHz to 200MHz! Advantages of the 21cm line! Direct probe of neutral IGM! Spectral line signal => full three dimensional image of structure formation (freq = z = depth)! Low freq => very (very) large volume surveys (1sr, z=7 to 11)! Hyperfine transition = weak => avoid saturation (translucent)! Ly-! lifetime ~ 1nanosec; 21cm lifetime ~ 10 7 yrs!

39 Seeing Through the Fog : # HI 21cm to 5 (67 to 240 MHz)! Gnedin et al. (2006)!

40 HI 21cm emission from neutral IGM: large scale structure, not individual galaxies ( intensity mapping )!! = 0.008( T CMB T S )( 1+ z 10 )1/2 f HI (1+") M sun Large scale structure! " cosmic density, (% " neutral fraction, f(hi)! " Temp: T K, T CMB, T spin! 10 9 M sun ~ Milky Way

41 Richest of cosmological data sets!! = 0.008( T CMB T S )( 1+ z 10 )1/2 f HI (1+") A. z>200: T CMB = T K = T S by residual e -, photon, and gas collisions. No signal.! E T cmb D C T S T K B A B. z 30 to 200: gas cools as T k (1+z) 2 vs. T CMB (1 + z), but T S = T K via collisions => absorption, until density drops and T S $ T CMB! C. z 20 to 30: first stars => Ly-! photons couples T K and T S => 21-cm absorption! D. z 6 to 20: IGM warmed by hard X-rays => T K > T CMB. T S coupled to T K by Ly-!. Reionization is proceeding => bubble dominated! E. IGM reionized! First stars Pritchard & Loeb 2010;! Loeb & Furlanetto textbook ch. 12!

42 Signal I: HI 21cm Tomography of IGM! z=12! 9! " )T B (2 ) ~ 20 mk! " SKA rms ~4 mk! " Pathfinders: rms ~ 80 mk! 7.6! " Requires SKA (> )! Furlanetto, Zaldarriaga et al. 2004!

43 Signal II: Pathfinder science goals! Evolution of 3D power spectrum in 21cm line! 30, 3MHz 3, 0.3MHz mk 2 10cMpc! Mpc -1 McQuinn!

44 Signal III: 21cm absorption toward the first radio galaxies! 19 mjy! z=12! z=8! SKA+Gnedin simulation! 130 MHz! 159 MHz! radio GP ($=1%)! 21 cm Forest (10%)! Only probe of small scale structure! Requires radio sources: expect 0.05 to 0.5 deg -2 at z > 6 with S 151MHz > 6 mjy!

45 Signal IV: quasar near zones at z > 6! " Ly-! spectra provide evidence for existence for CSS! 5Mpc Wyithe et al. 2006! " Size ~ 15! " Signal ~ 20 f(hi) mk = 0.5 f(hi) mjy! " rms (HERA, 100hr, 1MHz) ~ 0.08 mjy! " 3D structure = powerful diagnostic! " Rare but surveys will observe huge volume: >10s-100s deg 2 ; z=6 to 11! 0.5 mjy

46 Reionization! After recombination, the universe was neutral! At z~20 30, the first generation of galaxies and mini quasars formed! At z~6 15, the UV radiation from the first generation objects ionized most of the HI in the universe! The neutral fraction of the universe changed from 1 to 10-5 (phase transition in ionization state)! The temperature of the IGM electrons changed from CMB temperature to 10 4 K (phase transition accompanied by temperature change)! IGM becomes transparent to UV radiation, the universe is like a giant HII region (temperature change accompanied by opacity change)! Riechers 2013!