20x increase from z = 0 to 2!

Transcription

1 black hole accretion (AGN) & star formation (SF) 20x increase from z = 0 to 2! due to more gas (initial supply or accretion) or higher efficiency gas è stars, AGN starbursts merging? ALMA survey of ISM evolution at high z

2 1.5 < z < 2.5! 1000! M * /M! = 5x10 10! SFR [M! yr -1 ]! 100! 10! ssfr [Gyr -1 ]! 1! 10! ! stellar mass (M! )! ! redshift! Rodighiero 11, Sargent etal 12 need to measure gas contents

3 need : robust and fast measure of ISM CO ok, but... CO/H2 conversion factor excitation dependence (often measure high J CO) slow even w/ ALMA (hours per gal.) alternative, measure dust IR continuum + dust / gas ratio ALMA cycle 0, 2 & 3 projects (110, 180 and 360 galaxies w/i COSMOS field)

4 emitted SED -- increasing M dust L=10 12 L M dust = 10 8 è 6x10 9 M Scoville, 2011 Canary Is. winter school lectures peak shifts to longer λ for increased τ (or dust mass) flux on long λ tail scales linearly with M dust

5 R-J tail is optically thin, è F RJ = κ ν T dust ν 2 M dust / (4πd 2 ) T dust = K in Gal. SF global T dust doesn t vary much calibrate : L ν / M ISM = < κ ν T d M ISM / M dust > local galaxies Milky Way (Planck) SMGs

6 local galaxies normal SF gal. and ULIRGS w/ total Herschel SPIRE 500 μm fluxes & CO 1-0 z = 2-3 SMGs with CO (1-0) EVLA + SCUBA 850 μm

7 6.7x10 19 erg/s/hz/m w/ less than factor 2 dispersion Planck: Milky Way è 6.2x10 19 erg/s/hz/m β =

8 for ALMA Bands 3-7 predict : 3 σ in ~2 min for M ISM = 1x x faster than CO!

9 ALMA Cycle 2 observations galaxies w/ Sheth, Aussel, Vanden Bout, Capak, Bongiorno, Casey, Laigle, Ilbert, McCracken, Koda, Alvarez-Marquez, Murchikova, Koda, Pope, Toft, Ivison, Sanders, Manohar, Lee, Chu, 50, 60, 35 gal.

10 detection rates (2 min) -- 3 redshift ranges : flux mass

11 ISM masses vs ssfr = SFR / M * M mol (10 10 M )

12 ISM masses vs ssfr = SFR / M * M mol (10 10 M ) very similar masses at z = 2 to 1 perhaps a little higher at z ~ 5 mass up ot 4x10 11 M!!!

13 gas mass fraction : M mol / (M mol + M stellar )

14 ISM mass fraction : M ISM / (M ISM + M stellar )

15 individual galaxies : gas masses

16 ISM masses increase above the main sequence!! è increase in SFRs above the MS due to larger ISM masses analytic fit : SFR = 30 ±12 " M mol % $ ' # M sun & 1.1±0.1 " $ # 1+ z 3 % ' & 0.8±0.3 M sun yr 1

17 stacks of galaxies è a single linear SF law

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19 gas depletion times

20 very different than previous work from CO log ( Σ star form (M sun yr -1 kpc -2 ) ) y=1.17*x-3.48 y=1.17*x (0.12) SFGs α=1 merger α=3.2 SFG igure 1. Comparison of molecular gas masses and total IR bolometric luminositie Daddi etal 2010 typical uncertainty log (Σ mol gas (M sun pc -2 ) ) Genzel etal 2010 both used different CO conversion factors for SB and MS

21 our work è single, linear SF law at z = 1 to 6 and on MS and above MS SFR = 30 " M mol % $ ' # M sun & 1.1±0.1 " $ # 1+ z 3 % ' & 0.8±0.3 M sun yr 1 τ ISM stars = M ISM SFR 2 yrs ( 2 5x faster than z = 0) 6x108 huge accretion rates replace entire ISM w/i 3-7x10 8 yrs why is SF more rapid at z > 1?? Note do not fit for T d -- Lum.- vs mass-weigthed

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23 MS vs above the MS (starbursts?) è most of higher SFR due to increased gas

24 specific SFR (ssfr) relative to main sequence stack obs for each z in cells of M * and SFR

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27 z = 2.2 images :

28 ISM masses increase above the main sequence!! è increase in SFRs above the MS due to larger ISM masses analytic fits : gas frac = M mol M mol + M stellar = 0.30 " M stellar % $ ' # M sun & 0.02±0.02 " $ # 1+ z 3 % ' & 0.44 " ssfr % $ ' # ssfr MS & 0.32 SFR = 30 ±12 " M mol % $ ' # M sun & 1.1±0.1 " $ # 1+ z 3 % ' & 0.8±0.3 M sun yr 1