The Growth of Galaxies: Ways Forward toward a More Robust Understanding at High Redshift Mark Dickinson (NOAO)

GOODS: Great Observatories Origins Deep Survey 3 November 2006Mark Dickinson - MGCT2 The demographics of galaxy growth Star formation Stellar mass Galaxy merging

GOODS: Great Observatories Origins Deep Survey 3 November 2006Mark Dickinson - MGCT2 Cosmic star formation: a plethora of measurements… Hopkins & Beacom 2006

GOODS: Great Observatories Origins Deep Survey 3 November 2006Mark Dickinson - MGCT2 The global history of cosmic star formation The “cosmic” SFR(z): the comoving average SFR from galaxies, per unit volume, over cosmic time and redshift. What does it relate to? –Growth of stellar mass in galaxies (  (M*) vs. z) –Depletion of gas (  (HI) vs. z) –Build-up of metals (  (Z) vs. z) –Supernova rates vs. z –Ionizing background radiation –Extragalactic background light

GOODS: Great Observatories Origins Deep Survey 3 November 2006Mark Dickinson - MGCT2 Introduction, cont’d The era of multiwavelength measurements –UV –Mid-IR –Far-IR –Submm –Radio –Nebular emission lines –X-ray General challenges: –No one observable sees it all –Interpreting observables: model dependence –The IMF –Stellar population/evolution issues

GOODS: Great Observatories Origins Deep Survey 3 November 2006Mark Dickinson - MGCT2 SFR(z) vs.  *(z): tension at all redshifts? SFR(z)  stars (z) Derived SFR(z) may overproduce derived W*(z) at most redshifts Hopkins & Beacom 2006; see also Chary & Elbaz 2001; Dickinson et al. 2003; Ferguson et al. 2003

GOODS: Great Observatories Origins Deep Survey 3 November 2006Mark Dickinson - MGCT2 Stellar mass density, z~5 to 6 Stark et al. Eyles et al. Wiklind et al.  * (reion.), 6 < z < 10, C=30, f esc =1 Stars whose formation produces sufficient reionizing photons at 6<z<10 for 100% Lyman contin. escape fraction (Madau, Haardt & Rees 1999) Estimates for  * at z=5-6 are 5-50x smaller than at z~2-3 Yan et al. 2006

GOODS: Great Observatories Origins Deep Survey 3 November 2006Mark Dickinson - MGCT2 SFR demographics: GALEX UV at z < 1.2 Schiminovich et al Arnouts et al HDF N+S, Steidel’99 GALEX

GOODS: Great Observatories Origins Deep Survey 3 November 2006Mark Dickinson - MGCT2 Deep ISO surveys Chary & Elbaz 2001: Modeled deep number counts from ISO 15, 90, 170  m, SCUBA 850  m surveys, and the CIRB Minimal redshift information; small statistics Features: LIRGs dominate SFR at z~1 Fairly flat SFR(z) from 0.8 < z < 2; Turnover pushed toward lower z.

GOODS: Great Observatories Origins Deep Survey 3 November 2006Mark Dickinson - MGCT2 Into the Spitzer era Vastly improved statistics Deeper data Redshifts! Le Floc’h et al. 2005

GOODS: Great Observatories Origins Deep Survey 3 November 2006Mark Dickinson - MGCT2 Evolution of the IR luminosity density, 0 < z < 1 0 < z < 1:  UV (z) ~ (1+z) 2.5 (Schiminovich et al. 2005)  IR (z) ~ (1+z) 3.9 (Le Floc’h et al. 2005) Infrared/UV emitted energy from star formation: z=0 ~1.5 : 1 z=1 ~ 4 : 1 LIRGs ULIRGs Normal Galaxies Total IR UV Le Floc’h et al. 2005

GOODS: Great Observatories Origins Deep Survey 3 November 2006Mark Dickinson - MGCT2 Challenges: going deep enough 24  m-derived IR LFs, z < 1.2: Le Floc’h et al Spitzer wide surveys reach L IR ~ L o at z~1, ~ L o at z~2. Potentially large and uncertain LF extrapolation to total energy density: Have we really converged on  (SFR) at z ~ 1 ? Deep surveys (GOODS) cover small area and volume (cosmic variance).

GOODS: Great Observatories Origins Deep Survey 3 November 2006Mark Dickinson - MGCT2 GOODS MIPS 24  m ~  m sources with spectroscopic z GOODS MIPS data detects dust + PAH emission from LIRGs at z ~ 2-3

GOODS: Great Observatories Origins Deep Survey 3 November 2006Mark Dickinson - MGCT2 GOODS MIPS 24  m At 1 < z < 2.5, MIPS 24  m is ~10 to 1000x more sensitive to star formation than are deep VLA or SCUBA surveys.

GOODS: Great Observatories Origins Deep Survey 3 November 2006Mark Dickinson - MGCT2 z ~ 2-3: the ULIRG era? Chary et al. - Work in progress! Caveats: Spectroscopic (and photo-?) z samples incomplete) Templates for MIR- to-SFR conversion uncertain, esp. at higher L and higher z AGN identification uncertain SF component of AGN IR emission uncertain

GOODS: Great Observatories Origins Deep Survey 3 November 2006Mark Dickinson - MGCT2 Ways forward: SF demographics Forthcoming: –Deeper MIPS surveys over wider areas: Far-IR Legacy Survey; S-COSMOS Deeper at 24  m: hopefully below the LF knee at z~1; possibly convergence at z~2 Multiple fields: controlling cosmic variance Desperately needed: –Redshifts!! Especially for dusty galaxies/AGN at z > 1. Mid-IR K-corrections potentially very strong with small  z. Many of the galaxies which may dominate  (SFR) at z~2: –are not UV bright –have K > 20 Multiplexed NIR spectroscopy and wild heroism? Let’s hope so… Open issues: –AGN contribution to IR emission –Star formation contribution from those AGN –Mid-IR to SFR conversions

GOODS: Great Observatories Origins Deep Survey 3 November 2006Mark Dickinson - MGCT2 Challenges: MIR/SFR calibration rest frame 12  m at z ~ 1 z ~ 0 IRAS BGS 12  m L 12 ~ L IR < z < 1.2 GOODS 24  m vs. 1.4 GHz 20 cm fluxes -> LIR assuming z~0 radio/FIR correlation (Yun et al. 2001) MIPS 24  m -> L(12  m) with minimal k-correction Significant number of radio-loud outliers at z~1 (e.g., Donley et al. 2005) L 1.4GHz > WHz -1 : 38% outliers (>7% of z~1 sources with f(24  m) > 20  Jy) z=0 relation

GOODS: Great Observatories Origins Deep Survey 3 November 2006Mark Dickinson - MGCT2 PAH emission and SF SWIRE+SDSS: Tight 8  m / 70  m correlation, but with strong Z dependence 12+log(O/H) > 8.8: L 8 ~ L IR 0.9,  < dex Lower O/H -> low L 8 /L 70 Trend starts just below Z solar Monekiewicz et al. 2006

GOODS: Great Observatories Origins Deep Survey 3 November 2006Mark Dickinson - MGCT2 Challenges: calibrating 24  m/SFR at z~2 MIPS: =125  Jy, =1.9, and CE01 templates: = 1.7e12 L o, ~ 300 M o /yr UV continuum + reddening: ~ 220 M o /yr Radio: stacked VLA data = 17  Jy = 2e12 L o, ~ 340 M o /yr Sub-mm: stacked = 1.0 mJy (5  ) = 1.0e12 L o, ~ 170 M o /yr X-ray: stacked 8.5  soft-band detection, no significant hard-band. Far below expected AGN level. = M o /yr (Ranalli 2003, Persic 2004 conversions) On average, multiwavelength SFR tracers agree reasonably well with expectations from low-z correlations, templates & analogs. Daddi et al. 2005

GOODS: Great Observatories Origins Deep Survey 3 November 2006Mark Dickinson - MGCT2 Object by object SF comparisons at z~2 Daddi et al. in prep.Reddy et al. in prep. 24  m vs. H  24  m vs. radio

GOODS: Great Observatories Origins Deep Survey 3 November 2006Mark Dickinson - MGCT2 Submm emission, dust temperatures, etc. “warm” CE01“cool” CE01 (+ extra mid-IR extinction) 850mm too bright relative to radio or 24mm when compared With “warm” local ULIRG templates appropriate for these large L(IR). Pope et al. 2006

GOODS: Great Observatories Origins Deep Survey 3 November 2006Mark Dickinson - MGCT2 Implied dust temperatures Chapman et al  m/20cm flux ratios suggest cooler dust temperatures for the implied FIR luminosities, compared to the local L IR -T correlation.

GOODS: Great Observatories Origins Deep Survey 3 November 2006Mark Dickinson - MGCT2 Ways forward: SF calibration Measure true thermal far-IR dust emission: luminosities and temperatures –Deeper, wider Spitzer 70  m surveys –Herschel (  m) –SHARC2, SCUBA2, etc. (e.g  m) –ALMA Improved cross-calibration & diagnostic checks of SF: –Mid-IR vs. far-IR, submm, radio –Extensive mid-IR spectroscopy - Spitzer IRS

MIPS 24  m M81 = NGC  m

H  + R M81 = NGC 3031 H  + R

GOODS: Great Observatories Origins Deep Survey 3 November 2006Mark Dickinson - MGCT2 24  m rest frame emission traces star formation Calzetti et al M51 Calzetti et al. in prep.

GOODS: Great Observatories Origins Deep Survey 3 November 2006Mark Dickinson - MGCT2 600s GTO exposure Ultradeep 70  m imaging Frayer et al new MIPS Legacy Survey 10800s GO exposure, ~10’x10’

GOODS: Great Observatories Origins Deep Survey 3 November 2006Mark Dickinson - MGCT2 Spitzer Far-IR Legacy Survey GOODS-S E-CDFS: 30’x30’ EGS/AEGIS: 90’x10’ ~2000 arcmin 2 total 10x current GOODS 70  m 6.5x deep GOODS 24  m Sensitivities: ~3 70  m ~30  24  m L IR ~ L o at z=1 L IR ~ L o at z= arcmin 2 in GOODS-N

GOODS: Great Observatories Origins Deep Survey 3 November 2006Mark Dickinson - MGCT2

GOODS: Great Observatories Origins Deep Survey 3 November 2006Mark Dickinson - MGCT2 Deep 70  m matched to radio and submm 450  m 70  m 70  m survey limit well matched to very deep SCUBA  m surveys and to very deep 20cm VLA surveys: LIRGs at z~1 ULIRGs at z~2 24  m survey will reach “near-GOODS” depth over much larger areas: Normal galaxies at z~1 LIRGs at z~2

GOODS: Great Observatories Origins Deep Survey 3 November 2006Mark Dickinson - MGCT2 70  m constrains dust properties at high redshift 70  m/24  m: warm dust properties 450  m/70  m: bulk dust temperatures SCUBA-2! Dusty AGN

GOODS: Great Observatories Origins Deep Survey 3 November 2006Mark Dickinson - MGCT2 SFR(z): the first 2 Gyr At z > 3, UV is (almost) the only game in town: no direct measurement of reprocessed energy for most galaxies (yet). –Spitzer, Herschel, and near-term submm facilities can only detect hyperluminous (unlensed) objects –ALMA: L IR = Lo at z=6 in ~10 hours –JWST: H  at z < 6.5 Difficulties: –Uncertain extinction inferred from UV spectral slope alone. –Apparently very steep (but uncertain) UV LF slopes -> very large corrections to total luminosity density

GOODS: Great Observatories Origins Deep Survey 3 November 2006Mark Dickinson - MGCT2 Mass from light

GOODS: Great Observatories Origins Deep Survey 3 November 2006Mark Dickinson - MGCT2 Stellar mass: stellar population issues The IMF: The IMF almost certainly flattens/turns over at low mass. We use Salpeter because we’re lazy. Low-mass turnover is probably not a big problem: –It affects M*/L more or less uniformly at all wavelengths, including both stellar mass and SFR indicators. –Local evidence points to nearly universal low-mass IMF IMF slope at intermediate/high mass is a big deal! –Affects different SFR indicators differently –Changes luminosity evolution of stellar populations Fortunately, so far there’s not much convincing evidence for IMF slope variations.

GOODS: Great Observatories Origins Deep Survey 3 November 2006Mark Dickinson - MGCT2 SFR(z) vs.  *(z): tension at all redshifts? SFR(z)  stars (z) Derived SFR(z) may overproduce derived W*(z) at most redshifts Hopkins & Beacom 2006; see also Chary & Elbaz 2001; Dickinson et al. 2003; Ferguson et al. 2003

GOODS: Great Observatories Origins Deep Survey 3 November 2006Mark Dickinson - MGCT2 Stellar population issues (2) Star formation histories: Broad band SEDs are largely degenerate to a variety of possible past SF histories, which can lead to substantial M/L variations. Modeling often assume smooth, monotonic SF histories, but recent SF can mask hide high-M/L starlight from older stars. IRAC improves but does not eliminate this, especially for bluer, star-forming galaxies.

GOODS: Great Observatories Origins Deep Survey 3 November 2006Mark Dickinson - MGCT2 Mass from light

GOODS: Great Observatories Origins Deep Survey 3 November 2006Mark Dickinson - MGCT2 Composite stellar populations Significant mass from an older stellar population could be hidden by ongoing star formation. Papovich et al. 2001

GOODS: Great Observatories Origins Deep Survey 3 November 2006Mark Dickinson - MGCT2

GOODS: Great Observatories Origins Deep Survey 3 November 2006Mark Dickinson - MGCT2

GOODS: Great Observatories Origins Deep Survey 3 November 2006Mark Dickinson - MGCT2

GOODS: Great Observatories Origins Deep Survey 3 November 2006Mark Dickinson - MGCT2

GOODS: Great Observatories Origins Deep Survey 3 November 2006Mark Dickinson - MGCT2

GOODS: Great Observatories Origins Deep Survey 3 November 2006Mark Dickinson - MGCT2

GOODS: Great Observatories Origins Deep Survey 3 November 2006Mark Dickinson - MGCT2 IRAC observations of galaxies at z ~ 4-5 z~4 B-dropoutsz~5 V-dropouts

GOODS: Great Observatories Origins Deep Survey 3 November 2006Mark Dickinson - MGCT2 Stellar population issues (3) The models: No definite convergence on stellar population synthesis models yet. In particular, Maraston 2006 models: –Larger red light contribution from TP-AGB stars at Gyr –Different evolutionary tracks –Warmer RGB temperatures Redder colors and lower red/near-IR M/L at t < 2 Gyr Bluer colors at later times This reduces derived stellar pop. masses and ages at high redshift

GOODS: Great Observatories Origins Deep Survey 3 November 2006Mark Dickinson - MGCT2 Stellar population models Stellar mass may also be reduced by changing stellar population models: Maraston 2005 models with substantial TP-AGB contribution to red/near-IR light at ages of Gyr can reduce M/L significantly

GOODS: Great Observatories Origins Deep Survey 3 November 2006Mark Dickinson - MGCT2 Testing stellar M/L at high z Almost only SED modeling: at high redshift, almost no direct tests of stellar masses so far! –Galaxy kinematics to constrain M/L (mostly FP for early-type galaxies; see also RvdM talk) –Issues of dark matter effects in observed large-scale internal kinematics AO-fed integral field spectroscopy may be the best way forward.

GOODS: Great Observatories Origins Deep Survey 3 November 2006Mark Dickinson - MGCT2 Galaxy merging Galaxies grow their mass both by star formation and merging. A full understanding of galaxy growth requires understanding both. Stellar mass (M*) + star formation (dM*/dt) SF distribution functions versus time (t, z) are in principle sufficient … … but in practice real measurements of merger rates (ideally versus other galaxy properties (M*, SFR) would help a lot!! Observationally, still a highly debated topic, even at z < 1 In lieu of definitive data, models must guide us here.

GOODS: Great Observatories Origins Deep Survey 3 November 2006Mark Dickinson - MGCT2 The near-infrared data gap Near-IR data remain a huge bottleneck: –Much shallower than current deep optical or Spitzer/IRAC imaging. –Photo-z’s remain mandatory (unfortunately) and near-IR is the weakest link. Wide-field IR ground-based imagers: –WFCAM, WIRCAM, NEWFIRM, VISTA, HAWK-I, MOIRCS, FLAMINGOS-2, etc. HST/WFC3: –Detect fading red remnants of higher-z star formation –Differentiating stellar population components within galaxies –Measure UV spectral slopes (dust reddening) at z > 5 –Photometry/SEDs/photo-z’s for UV-faint galaxies at z > 5 –Reliable 2-color LBG selection at 6 < z < 10+

GOODS: Great Observatories Origins Deep Survey 3 November 2006Mark Dickinson - MGCT2

GOODS: Great Observatories Origins Deep Survey 3 November 2006Mark Dickinson - MGCT2 Stellar mass density, z~5 to 6 Stark et al. Eyles et al. Wiklind et al.  * (reion.), 6 < z < 10, C=30, f esc =1 Stars whose formation produces sufficient reionizing photons at 6<z<10 for 100% Lyman contin. escape fraction (Madau, Haardt & Rees 1999) Estimates for  * at z=5-6 are 5-50x smaller than at z~2-3 Yan et al. 2006

GOODS: Great Observatories Origins Deep Survey 3 November 2006Mark Dickinson - MGCT2 Ways Forward: a summary Fully exploit existing surveys: the era of “precision  L (z)” More redshifts! (and more reliable redshifts!) Extend multi- correlation studies at all redshifts –MIR, FIR, radio, UV, X-ray, H , etc. –Deeper radio and FIR vital: SCUBA-2, Herschel, ALMA… Mid-IR improvements: –Better mid-IR spectral templates –IRS spectral diagnostics for large high-z samples –Figure out the physics!!! (esp. MIR, PAHs, etc.) Measure dust temperatures at high z Get stellar evolution straight (stellar pop. models) It’s the IMF, dummy (esp. at intermediate & high masses) Better measurements of merger rates (vs. z & other properties) Insanely deep surveys at z~5-6 and beyond (WFC3; JWST; ALMA; TMT)

GOODS: Great Observatories Origins Deep Survey 3 November 2006Mark Dickinson - MGCT2

GOODS: Great Observatories Origins Deep Survey 3 November 2006Mark Dickinson - MGCT2 HDF-N: Negative serendipity Kajisawa et al. 2006: Subaru/MOIRCS distant red galaxies in GOODS-N

GOODS: Great Observatories Origins Deep Survey 3 November 2006Mark Dickinson - MGCT2 HDFN-JD1

GOODS: Great Observatories Origins Deep Survey 3 November 2006Mark Dickinson - MGCT2 HDFN-JD1 from Spitzer  m SED favors old, z~3 stellar population. No MIPS 24  m detection: probably not a dusty starburst/ERO.

GOODS: Great Observatories Origins Deep Survey 3 November 2006Mark Dickinson - MGCT2 Similar to AGN Evolution High luminosity AGN peak at z~2 Less luminous AGN / Seyferts peak at z~1 Ueda et al. 2003