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Massive quiescent galaxies at cosmic noon Robert Feldmann UC Berkeley R. Feldmann, SnowPAC, March 2016 1 nt redshifts, finding good agreement between the semi-analytic mented in the literature (e.g. Damen et al. 2009). Further, in the Bimodality of nearby galaxies Star forming The Astrophysical Journal, 735:86 (21pp), 2011 July 10 • • • high SFR per unit mass young ages dominate the low mass end • • • Quiescent low SFR per unit mass old ages, red colors dominate the massive end U-V color (u-r) The Astrophysical Journal, 735:86 (21pp), 2011 July 10 V-J Figure 17. Rest-frame UVJ diagram for NMBS galaxies with S/N > 8 in the K band out to a redshift of 3.5. The gray scale rep lines indicating the separation between quiescent “red sequence” galaxies and star-forming galaxies (both blue and red). The qu highest redshift interval 2.5 < z < 3.5. Apparently, the first quiescent galaxiesOesch stopped forming stars by that redshift (see also M e.g. Kauffmann+03, Baldry+04,06, Scarlata+07, +2010, Peng+10, Wong+12, Ciambur+2013, Kelvin+2014 ... Additionally, we modify the limits in U − V and V – J such that R. Feldmann, SnowPAC, March 2016 galaxies is therefore ideal for ch NIR medium-band filters relative 2 filters. Galaxies at Cosmic Noon (z~1.5-3) • the two populations exist already at peak of cosmic SF history The Astrophysical Journal, 739:24 The Astrophysical (14pp), 2011 September Journal,20 739:24 (14pp), 2011 S 10 M • ~equal number of SF and quiescent galaxies at M*≳few 10 ☉ The Astrophysical Journal, 739:24 (14pp), 2011 September 20 The Astrophysical Journal, 739:24 (14pp), 2011 September 20 Brammer et al. The Astrophysical Journal, 739:24 (14pp), 2011 September 20 • => factors aside from mass likely important in “quenching” of SF The Astrophysical Journal, 739:24 (14pp), 2011 September 20 Magnelli+2014 z ~ 0.6 z~2 Figure Stellar mass functions sample (top panels) split using thesaq Figure 4. Stellar mass functions for the full NMBS sample (top panels) Figure and split4.4. using themass quiescent/star-forming selection shown infunctions Figure 2panels) (middle panels). The Stellar functionsfor Figure forthe thefull full 4. NMBS Stellar NMBS mass sample (top forand theand full split NMBS using Brammer+2011 points shown are simple redshift histograms divided byby thethe volume ofhistograms the NMBS, with Pois points shown are simple redshift histograms divided by the volume of the NMBS, Poisson error bars. for Representative Schechter (1976) function fitssplit aredivided shown, points shown are simple redshift points histograms shown divided are simple redshift volume ofand the NMBS, with b Figure 4.with Stellar mass functions the full NMBS sample (top panels) using the with the rest-frame slope fixed to α = −0.99, −1.4, and −0.7 for the full, star-forming, and with the rest-frame slope fixed to α = −0.99, −1.4, and −0.7 for the full, star-forming, and quiescent samples, The dotted lines show the local stellarPoi points are simple divided byslope the −0.7 volume NMBS, with with theshown rest-frame sloperedshift fixed tohistograms with α =respectively. the −0.99, rest-frame −1.4, and fixed for toof the αthe =full, −0.99, star-forming −1.4, a mass function of all (black), early-type (red), and late-type (blue) galaxies (Bell et al. 2003), mass function of all (black), early-type (red), and late-type (blue) galaxies (Bell et rest-frame al. 2003), as described the text. The light hatched regions the with the slope fixed to mass α = in −0.99, −1.4, and −0.7 for the full, show star-forming, an mass function of allscaled (black), early-type function (red), and of late-type all (black), (blue) early-type galaxies (red), (Bell and et90% al. late2 completeness limit for red galaxies at the high-redshift end of each bin. Note that we determin completeness limit for red galaxies at the high-redshift end of each bin. Note that we determine number and mass densities below by simply counting objects at masses mass function of all (black), early-type (red), and late-type (blue) galaxies (Bell et al. 2003 completeness limit for red galaxies completeness at the high-redshift limit forend redofgalaxies each bin. at the Note high-redshift that we dete where thebottom NMBS isforcomplete, rather thanhigh-redshift integrating the Schechter functions. Thewe pa where the NMBS is complete, rather than integrating the Schechter functions. The panels show the fraction of red, quiescent galaxies as a function ofbottom stellar completeness limit red galaxies at the end of each bin. Note that determi where the NMBS is complete, rather where than the integrating NMBS issample complete, the Schechter rather functions. than integrating The botto t 3 R. Feldmann,mass SnowPAC, March 2016 Figure 4. Stellar mass functions for the full NMBS (top panels) and split using massand andearly+late redshift. The dottedfunctions, line showswhile the ratio of thelines Bell show et al. (2003) andSchechter early+latet and redshift. The dotted line shows the ratio of the Bell et al. (2003) early Schechter the solid the ratioearly of the galaxy inferred from photometric data. ptical galaxies but much 8–13 significant recent structural onsiderable attention , Galaxies Massive at Cosmic Noon and dynamica galaxies over the past 10 Gyr. The uncerta rown in size by a factor of ALMA: 870μm + CO Extreme Star-bursts (SMGs) was determined from simulations~1.4that i rs (10 Gyr). A key test of Gyr and template mismatch. However, w ellarHighest kinematics of• one form of stars atnoise rates ~1000 times possibility that some subtle systematic effe objects are as extreme asour Galaxy, that of very dusty the analysis, given the low signal-to-noise ed to have much• higher extremely luminous in sub-mm laxies of the same mass. We observed the galaxy, dubbed 1255–0, • few examples in today’s Universe: 1’’ the Gemi tellar velocity dispersion Infrared Spectrograph (GNIRS) on all major 5 2.186, corresponding to galaxy totalmergers of 29 h. The de-redshiftedOteo spectrum et al. 2016 Star formation activity The ISM of two interacting distant Lowest • ncom ~ 10-5 Mpc-3 (today’s clusters) Quiescent galaxies • low star formation, little dust • often very compact (≲ 1 kpc) • ncom ~ 10-4 - 10-5 Mpc-3 (today’s groups & clusters) HST image ~3 Gyr Fig. 2.— Upper : ALMA 870µm continuum map of SGP38326. The three detected SMGs are indicated. The grey contours represent the integrated 12 CO(5–4) emission. This line is clearly detected in both SMG1 and SMG2, but there is no 12 CO(5–4) detection in SMG3. The beam sizes of the 12 CO(5–4) (grey ellipse, 1.1!! × 1.0!! ) and dust continuum (white ellipse, 0.16!! × 0.12!! ) observations are shown, and clearly highlight the impressive increase in spatial resolution. Bottom: Velocity map of SMG1 derived from the 12 CO(5–4) emission using moment masking (Dame 2011). It can be seen that, despite the lack of spatial resolution, the 12 CO(5– 4) observations already indicate that SMG1 presents a disk-like rotation. In both panels, north is up and east is left. 28.6 ± 5.8 mJy, S500µm = 46.2 ± 6.8 mJy. SGP38326 was subsequently observed with SCUBA-2 at 870 µm (S870µm = 32.5 ± 4.1 mJy) and, by fitting a set of FIR templates to its SPIRE and SCUBA-2 flux densities, we determined a best-fit photometric redshift zphot ∼ 4.5. The ALMA spectral scan in the 3mm window confirmed its redshift to be z = 4.425 ± 0.001 via detection of the 12 CO(4–3) and 12 CO(5–4) emission lines (Fig. 1). The total IR luminosity of SGP38326, obtained from an SED fit to the Herschel and SCUBA- 0.5″ b van Dokkum et al. 2009 R. Feldmann, SnowPAC, March 2016 Model 13 4 C.M. Casey et al. / Physics Reports 541 (2014) 45–161 50 C.M. Casey al. / Physics Reports 541 (2014) 45–161 Merger based paradigm etReports al. /etPhysics Reports 541 (2014) 45–161 C.M. CaseyC.M. et al. Casey / Physics 541 (2014) 45–161 50 C.M. Casey et al. / Physics Reports 541 (2014) 45–161 50 Star-burst interacting galaxies B AGN /Quasar D C Hopkins et al. 2008 quiescent galaxy isolated disk galaxies A A B C D E E e.g. Di Matteo+2005, Springel+2005, ... also see Mark Brodwin’s talk yesterday R. Feldmann, SnowPAC, March 2016 5 Merger based paradigm Success of this picture • explains/links origin of star-bursting and quiescent galaxies • many galaxies in a young Universe show disturbed morphologies Challenges • fails to reproduce observed number density of star-bursting galaxies • short duty cycle of star-bursts • rate of major mergers between galaxies is too low • mergers do not produce enough sub-mm flux efficiently • Unclear whether super-massive black hole regulate/stop star formation R. Feldmann, SnowPAC, March 2016 6 Basic Questions: • Why are some massive galaxies at Cosmic Noon quiescent and others of the same stellar mass are star forming? • What is the origin of the extreme star-bursting population at Cosmic Noon? • How important is the moment/energy injection from supermassive black holes? • Which role does the cosmological environment / halo assembly play? R. Feldmann, SnowPAC, March 2016 7 Massive PI: Feldmann in collaboration with: F RE Feedback In Realistic Environments E. Quataert (Berkeley), P. F. Hopkins (Caltech), C-A. Faucher Giguere (NorthWestern), D. Keres (UC San Diego) Goals: . Feldmann (Berkeley), E. Quataert (Berkeley), P. F. Hopkins (Caltech), -A. Faucher Giguere (NorthWestern), D. Keres (UC San Diego) Farthest observed galaxies Peak epoch of galaxy formation Today 1. Study the peak era of galaxy formation in the Universe Specs SPH / FIRE with high-resolution cosmological simulations • 18 zoom-in regions in a (144 Mpc)3 box http://www.astrophoto.com/M82.htm (pressure-entropy) SPH . & improved art. viscosity • main halos ~ 3×1012 M (a few billion years after the Big Bang) (~14 billion years after the Big Bang) – 3×1013 M (end of re-ionization) 4 • downprocesses to z=2 2. Explore the physical that shape the tional softening • mSPH ~ 3×104 M at those times nergetic FB galaxy from SNe &population stellar • pressure, metal+mol. cooling , 100% efficiency per tff minimal gravitational softening for gas, stars ~10 pc • ~1 billion SPH particles 3. Prepare synthetic observations that guide the interpretation of upcoming galaxy surveys with current and future instruments 9 • Atacama Large Millimeter/SubMM Array (ALMA) • James Webb Space Telescope (JWST) • LSST, TMT, GMT, ESO E-ELT R. Feldmann, SnowPAC, March 2016 8 MassiveFIRE • Suite of cosmological, hydrodynamical zoom-in simulations • Run with GIZMO (pressure-entropy SPH) • Star formation and stellar feedback modeling based on Feedback in Realistic Environments (FIRE) approach (Hopkins et al. 2014) • star formation not tuned to empirical scaling relations • stellar feedback physically modeled (no “recipes”): radiation pressure, stellar winds, supernovae • no energy / momentum injection from • High numerical resolution: ~10 pc, ~104 M⊙◉☉ R. Feldmann, SnowPAC, March 2016 credit P .F. Hopkins supermassive black holes 9 Selection • 18 individual zoom-in simulations (range of assembly histories) • ~40 massive galaxies (~50% centrals) z=2 3 × 10 1 3 M ! 1 × 10 1 3 M ! 3 × 10 1 2 M ! 3 halo mass bins at z=2: 3×1012, 1013, and 3×1013 M☉ • secondary selection based on environmental density • Largest sample of simulated massive galaxies at z~2 with highly resolved internal structure ] [ solar halo mass M( < R vi r) [ Mmasses ! ] • primary selection based on halo mass 14 10 13 10 12 10 11 10 0 13.7 2 3.3 4 1.5 z 6 1 0.68 cosmic time [ Gyr ] R. Feldmann, SnowPAC, March 2016 10 Validation of the physical model • properties of galaxies in today’s Universe, e.g., relations between star formation rate, gas content, mass-metallicity relation (e.g. Hopkins et al. 2014, Ma et al. 2016) • properties of outflows driven by stellar energy/momentum injection (Muratov et al. 2015) • Variability of the star formation rate in galaxies (Sparre, Hayward, RF et al. 2016) • covering fractions of neutral hydrogen in massive halos (Faucher-Giguère, RF, et al. 2016) • presence of large star forming clumps in massive, young galaxies (Oklopčić, Hopkins, RF, et al. submitted) • Soft X-ray emission, Sunyaev-Zel’dovich signal (van de Voort, Quataert, RF et al. in prep) • Properties of dwarf galaxies (see Andrew’s talk) • ... R. Feldmann, SnowPAC, March 2016 11 Stellar mass - halo mass relation 10 10 Mstar[Msun] 10 12 MassiveFIRE 11 10 10 10 10 10 10 z=2 z=5 z=9 High resolution Medium resolution Centrals Satellites 9 8 7 Moster et al. 2013 z=2 z=5 z=9 6 5 R. Feldmann, SnowPAC, March 2016 10 9 10 10 11 10 10 Mvir[Msun] 12 10 13 10 14 RF et al. 2016 MNRAS 12 Separating star forming and quiescent galaxies • physical classification: low star formation rates per unit stellar mass • observational classification: galaxy colors consistent with low/high SF (U-V)restframe t = 3 Gyr U V J Straatman et al. 2014 Tomczak et al. 2014 R. Feldmann, SnowPAC, March 2016 (V-J)restframe 13 Star forming and quiescent galaxies star formation rate / galaxy sSFR [yr-1] mass [ yr-1 ] 10 10 10 10 10 -8 • SF/Quiescent classification based on U-V, V-J colors (from mock images) -9 MassiveFIRE Star forming Quiescent -10 • matches well the split of galaxies into those on and those below the SF sequence Centrals Satellites High res. Medium res. -11 z=2 z=1.7 Schreiber et al. 2015 -12 • Quiescence: factor of a few below the SF sequence; not fully “quenched” z=2 z=1.7 10 10 10 11 galaxy stellar M mass solar [M[ sun ] masses ] star R. Feldmann, SnowPAC, March 2016 14 Star forming galaxies • dusty • disturbed morphologies • disky / irregular Quiescent galaxies • dust-poor • spherical/elliptical • yellow-ish colors R. Feldmann, SnowPAC, March 2016 15 Growth history of halos and galaxies Quiescent galaxy Star forming galaxy 12 12 10 10 0.05M D M M b a r≤ 1 . 5 × 1 0 4 K M star M g a s≤ 1 . 5 × 1 0 4 K 11 11 10 Mass (< r) [ M sun ] Mass (< r) [ Msun ] 10 10 10 9 10 0.05M D M M b a r≤ 1 . 5 × 1 0 4 K M star M g a s≤ 1 . 5 × 1 0 4 K 10 10 9 10 10 fi t t e d gr ow t h r at e s [ X , R ] : d l nM X ( < R ) /d z [ D M, R v i r] : 0. 54 [ st ar s + gas ≤ 1. 5 × 10 4 K , 0. 1 R v i r] : 0. 14 [ st ar s , 0. 1 R v i r] : 0. 24 ID 9:0 Q 7 10 SF 8 8 10 ID 223:0 fi t t e d gr ow t h r at e s [ X , R ] : d l nM X ( < R ) /d z [ D M, R v i r] : 1. 49 [ st ar s + gas ≤ 1. 5 × 10 4 K , 0. 1 R v i r] : 1. 67 [ st ar s , 0. 1 R v i r] : 2. 24 2 3 4 5 6 7 7 10 8 M (t) / e R. Feldmann, SnowPAC, March 2016 3 4 5 6 7 8 z z z(t) 2 [1 + z(t)] “smoothes out” individual mergers • estimate growth rates at z=2 • 16 1.25 1 Star forming Quiescent Centrals Satellites log 10 0.75 M star 10 10.5 11 11.5 0.5 stronger baryon growth d lnM H I + H 2 + s t a r ( < 0.1R vi r ) /d t [ Gyr − 1 ] galaxy growth (stellar + gas mass) 1.5 0.25 0 −0.25 stronger DM growth −0.25 0 0.25 0.5 0.75 1 d lnM D M ( < R vi r ) /d t [ Gyr 1.25 −1 ] 1.5 RF et al. 2016 MNRAS, see also RF & Mayer 2015 dark matter halo growth • galaxy & halo growth are strongly correlated (similar timescales) • Low specific growth rates necessary to become quiescent R. Feldmann, SnowPAC, March 2016 17 log10(S H 11 10 10 1.0 -1.0 10 0 1 0.5 2 z 3 4 5 Simple Toy Model 6 7 8 • Identify SF/Quiescent with galaxies with increasing/decreasing SFR shift. The overlaid white lines show average mass accretion histories for halos as mass of >1015.5 M! at z = 0 and therefore are not expected to exist. Right panel: or galaxies at z = 0. This figure shows the historical star formation rate for stars is so low, this is equivalent to the star formation rate traced along the white mass • What (specific) baryonic growth rate corresponds to dSFR/dt = 0? 10000 10 Time [Gyr] 4 7 11 1 Behroozi+13 Mh(z=0) = 10 MO • 1000 2 12 • Mh(z=0) = 10 MO d ln Mbar 1 R + dtdep /dt |dSFR/dt=0 = crit (M⇤ , t) ⌘ dt tdep + M⇤ /SFR 14 Mh(z=0) = 10 MO • • -1 SFR [MO yr ] • 10 • Specific growth rates > crit => increasing SFR, increasing gas reservoir 1 0.1 0.01 0 d R)SFR + SFR tdep dt Mh(z=0) = 10 MO 13 100 d d Mbar = (Mstar + Mgas ) = (1 dt dt 0.5 1 2 z 3 4 5 6 7 8 alo mass and redshift (lines). Shaded regions indicate the 1σ posterior distribution. nes). Shaded regions indicate the 1σ posterior distribution. Histories for 1015 M! • SFR ~ c SFR crit => decreasing SFR, limit: SFR ~ net inflow rate onto galaxy , c determined from dSFR/dt=0 condition, c ~ 0.16 - 0.3 MS in Figure 6. We show similar plots with 1σ uncertainties The left-hand panel demonstrates that the SFR at fixed halo mass has been monotonically decreasing since very early • ratedep redshifts. This of decrease is different for different halo masses. At moderate to high redshifts (z > 2), larger halo masses generically have larger average SFRs. However, at lower redshifts, the highest mass halos (Mh ! 1014 M! ) become so inefficient that they have lower SFRs than group-scale (1013 M! ) halos or Milky-Way sized (1012 M! ) halos. From the perspective of individual galaxies, it is more illuminating to look at the SFH in the right panel of Figure 6. Because halos continually gain mass over time, and do so R. Feldmann, March more rapidly atSnowPAC, early redshifts, the 2016 SFH for galaxies is not t • Specific growth rates < (Genzel et al. 2015), SFRMS (Schreiber et al. 2015) crit ~ 0.25, 0.27, 0.4 Gyr-1 for M*~1010, 3×1010, 3×1011 M☉ 18 Let’s do the numbers 1 10 10.5 MassiveFIRE (hydro) simulations N-body simulation + analytic model fquiescent(>M) 0.7 simulations 0.6 0.4 0.3 Xcrit x1.1 x1.0 0.2 0 1.5 model observations 0.5 x0.9 0.1 M growth 1.25 quiescent fraction 0.8 10 10.5 11 11.5 11.2 z~2 Tomczak et al. 2014 Muzzin et al. 2013 0.9 og10 Mstar log10Mstar[Msun] 10.8 11 11.1 12 12.5 13 log10Mvir[Msun] 13.5 14 Figure 5. Fraction of quiescent, central galaxies residing in halos e of baryonic Model:above Quiescent galaxies are those with dbylnMassiveFIRE Mhalo/dt <are a given mass. The fractions predicted DM masses of shown standard deviaR. Feldmann, SnowPAC, March 2016by filled circles. Error bars indicate 1 how quiescent crit 19 Normalize Normaliz Normalized 10–1 1 a 1 10–2 100 Normalized quantities 31 2 1012) 2 23 12 10 ) (M 2 3 SFR/1,526 (M yr–1) Normalized Normalized quantities Normalizedquantities quantities 10–1 10–2 10–3 star formation rate 6 30 1 10 M /(1.1 × ) d bc * 10 S850/31.9Dust (mJy) mass/(1.5 × 10 ) (M ) b 1× (M ) SFR/1,526 10–1 ass/(1.5 × 1010(M ) (M yr) –1) Normalized quantities LETTER RESEARCH Extreme star-bursts LETTER Time since Big Bang (Gyr) RESEARCH Time since Big Time Bang since (Gyr) Big Bang (Gyr) since Big Bang (Gyr) 100Time b 10 10 d 5 4 z 3 2 sSFR/10.0 (Gyr–1) 10–1 6 100 Time since Big B 3 1 Time Time since Big (Gyr) since BigBang Bang (Gyr) 10–2–2 10 0 10 1000 10 b 1 100ac 2 2 c sSFR/10.0 (Gyr–1) 12 M /(1.1 × 10 ) (M SFR/1,526 ) /31.9 (mJy) SS850 (mJy) 850/31.9 * mass/(1.5 × 1010) (M ) Dust 5 mJy = 5 10-29 W m-2 Hz-1 10–1 3 100 3 d d b (M yr–1) 10–1–1 SFR/1,526 (M yr–1) 10 10–1 10–1 z –2 = 2 MS –2 10 10 –3 –2 10–3 10 10 65 100 6 sub-mm flux c 4 55 z S850/31.9 (mJy) 3 44 zz 323 10–2 22 66 d Normalized quantities –2 10 of physical and observable properties of the 11| |Evolution includes a correction factor of 0.7 forTurk, massof loss. major g Narayanan, RF, etLocations al. 2015 of Nature Figure Evolution ofphysical physical and observable observable properties of the includ Figure of and properties the includ 100the central galaxy. In each on region and panel, the emission mergers (.1:3) arethe noted by green vertical tickspanel, on thethe top axis merge of b. T submillimetre emission region and the central galaxy. In each each panel, the merge submillimetre region and central galaxy. In c star dwhenare • extreme sub-mm emission kpc submillimetre emission regionformation are shown withrate, thick purple shaded in c shows theshown galaxywith would be detectabl properties ofthe thehigh 200 kpc submillimetre emission region shown with thick purpl 10–1 region properties of 200 kpc submillimetre emission region are thick purpl 5 mJy). pinkdashed and purple regio e of the central galaxy are S given/31.9 by thin(mJy) dashed lines. SMG SCUBA (S850 . solidlines, lines, whilethose those ofwith thecentral central galaxy are given The by thin thin dashed lines.shadedSMG SMG –1 galaxy solid while of the are given by lines. 850 10 –1galaxy” d10show rough ranges for the z 5850 2 main-sequence (MS) andddstarb ss; b, SFR; c,•predicted 850 mma,a, flux density; wouldobserved be classified as “sub-mm sho Stellar anddust dustmass; mass; b,the SFR; predicted observed 850 mm flux flux density; density; sho Stellar and b, SFR; c,c, predicted observed mm d quantities 0 region timescales, andsSFR regime; the 10 grey in d denotes below main sequence. M*/SFR). The SFR is averaged on 50 Myrd,d, /SFR). The SFRisisaveraged averaged on 50 50 Myrthe timescales, and regim regim specificSFR, SFR, sSFR (M * /SFR). The SFR on Myr timescales, and specific (M –1* –1 (Gyrd) 10–2 of real sub-mm galaxies sSFR/10.0 (Gyr ) •–1spectrum agrees sSFR/10.0 well with observations 10 1.9 (mJy) density projections of six arbitrarilypresent chosengas snapbetween z< 2–3 and toof outliers. One consequence of a model i present gas surface density projections of six arbitrarily arbitrarily chosen snapsnapbetwe surface density projections six chosen betwe 20 R. Feldmann,ofSnowPAC, March 2016 evolution the submillimetre-luminous phase SMGs typically lie on the main sequence of star formation z = 2 MS z (kpc) 50 Lessons for SMG formation 0 –50 • many sub-mm observations confuse multiple sources into one z = 3.0 NH (g cm–2) –100 • galaxy is surrounded by smaller (but still luminous) companions1018 z = 2.6 z = 2.8 100 1017 z (kpc) 50 0 –50 1016 –100 z = 2.5 –100 –50 250 kpc 0 50 y (kpc) 100 z = 2.2 –100 –50 0 50 100 z = 2.0 –100 –50 50 x (kpc) 0 50 FWHM of SCUBA C.M. Casey et al. / Physics Reports 541 (2014) 45–161 100 x (kpc) sub-mm phase not initiated by subhaloes. majorSome merger (last finished ~1 Gyr of the brightest SMGs arise from numerous galaxiesearlier) within the e 2 | Surface•density projection maps of the 250 kpc region around entral submillimetre galaxy for redshifts z < 2–3. The submillimetre ion region probed in surveys typically encompasses a central galaxy in a ve halo that • is undergoing a protracted bombardment phase by numerous } beam in a rich environment (bottom right panel). The colour coding denotes the gas column density (NH), with the colour bar on the right. star formation is powered by large gas reservoir: solves problem with SMG number counts • inflow gasdustfrom web e from ,1 kpc to 8 kpc, compare well withof recent maps cosmic can come from older stars with ages tage . 0.1 Gyr. Using standard conversions25, the estimated SFR from the integrated infrared SED rved using the Atacama Large Millimetre Array24. he stellar masses, gas fractions•and lifetimes are in agreement (3–1,100 mm) can exceed ,3,000M[ yr21 (Extended Data Fig. 6), and re-accretion of gas expelled via outflows some previous lower-resolution cosmological efforts10, although hence infrared-based SFR derivations of dusty galaxies at high z may predicted SFR and luminosity from this model are substantially over-estimate the true SFR by a factor of ,2. Indeed, the contribution satellitetime galaxies(~1 to the Gyr) global SFR, along with the contribution of old r. The SFR•ofstar the group of galaxies remains in the regionhigh peaks for at of formation long 21 00M[ yr . Importantly, up to half of the total infrared luminosity stars to the infrared luminosity may relieve some tensions between the inferred SFRs from submillimetre galaxies and massive galaxies modelled in cosmological hydrodynamic simulations10. 8 R. Feldmann, SnowPAC, March 2016 50 50 50 50 50 C.M. Casey et al. / Physics Reports 541 (2014) 45–161 Casey al. Physics Reports 541 (2014) C.M. CaseyC.M. et al.Casey /C.M. Physics 541/(2014) 45–161 et Reports al. /et Physics Reports 541 (2014) 45–16145–161 C.M. Casey et al. / Physics Reports 541 (2014) 45–161 Fig. 2. A schematic diagram of the evolution of a galaxyFig. undergoing a major merger of gas-rich during itsdisks lifetime. Image credits: (a) NOAO/AURA/N 2. A schematic diagram of the evolution of a galaxy undergoing adisks major merger of gas-rich during its lifetime. Image credits: (a) NOAO/AURA/NSF; (b) REU program/NOAO/AURA/NSF; (c) NASA/STScI/ACS Science Team; (d) Optical (left): NASA/STScI/R. P. van der Marel & J. Gerssen; X-ray (right): (b) REU program/NOAO/AURA/NSF; (c) NASA/STScI/ACS Science Team; (d) Optical (left): NASA/STScI/R. P. van der Marel & J. Gerssen; X-ray (righ NASA/CXC/MPE/S. Komossa et al.; (e) Left: J. Bahcall/M. Disney/NASA; Right: Gemini Observatory/NSF/University of Hawaii Institute for Astronomy; (f) J. Bahcall/M. Disney/NASA; (g)Right: F. Schweizer (CIW/DTM);Observatory/NSF/University (h) NOAO/AURA/NSF. NASA/CXC/MPE/S. Komossa et al.; (e) Left: J. Bahcall/M. Disney/NASA; Gemini of Hawaii Institute for Astronomy; Source: This figure is reproduced from Hopkins et al. (2008) with permission from the authors and AAS. J. Bahcall/M. Disney/NASA; (g) F. Schweizer (CIW/DTM); (h) NOAO/AURA/NSF. Source: This figure is reproduced from Hopkins et al. (2008) with permission from the authors and AAS. 21 Summary • The young Universe hosts galaxies with very different properties than today’s Universe • Origin and evolution of quiescent / star-bursting galaxy population at this epoch is not (fully) understood • Quiescent galaxies: • Often assumed to be the result of energy injection from supermassive black holes • may become quiescent as a result of a slow down of their cosmic accretion of gas • Star-bursting galaxies: • traditionally associated with major mergers between galaxies, but • may be driven by gas accretion from cosmological distances & recycling Properties of galaxies are tightly linked to the growth history of their halos R. Feldmann, SnowPAC, March 2016 22