Observations of High Redshift Galaxies with CCAT Alice Shapley (Princeton University) October 10th, 2005

2 Overview CCAT will provide new windows on star formation for sub-ULIRG star-forming galaxies at high redshift, including information about dust, gas content, HII region physical conditions, and star- formation feedback New results at shorter (optical through mid-IR) wavelengths, CCAT observations will greatly enhance their meaning

3 New results Spitzer 24  m observations provide estimates of L bol for L~ L  galaxies (LIRGS) at z~2-3, but this is indirect M-Z relation, gas fractions in star-forming galaxies at z~2, using optical and near-IR imaging and spectroscopy Physical conditions appear to be different in high redshift HII regions (z~1-2), based on rest-frame optical emission lines

4 Relevant Observations with CCAT submm continuum --> L FIR, L bol, T dust CO lines --> M gas (molecular, assuming conversion factor), gas fractions, Schmidt law [CII] 158  m, [OI] 63  m, [OIII] 88, 52  m --> (HII region and ISM physical conditions, densities, cooling) Different probes of star formation

5 z>2 color-selection Adjust z~3 UGR crit. for z~2 (Adelberger et al. 2004) Spectroscopic follow-up with optimized UV-sensitive setup (Keck I/LRIS-B) (Steidel et al. 2004)

6 z>2 color-selection Adjust z~3 UGR crit. for z~2 (Adelberger et al. 2004) Spectroscopic follow-up with optimized UV-sensitive setup (Keck I/LRIS-B) (Steidel et al. 2004)

7 Redshift Distributions Unsmoothed LBG: z~3 (940) S LBG =1.7/arcmin 2 n LBG =1.4x10 -3 Mpc -3 BX: z=2-2.5 (816)  BX =5.2/arcmin 2 n BX =2.0x10 -3 Mpc -3 BM: z= (118)  BM =3.8/arcmin 2 n BM =1.7x10 -3 Mpc gals at z= (Steidel et al. 2004; Adelberger et al. 2004) BX/BM/LBG with R<=25.5

8 Redshift Distributions Unsmoothed LBG: z~3 (940) S LBG =1.7/arcmin 2 n LBG =1.4x10 -3 Mpc -3 BX: z=2-2.5 (816)  BX =5.2/arcmin 2 n BX =2.0x10 -3 Mpc -3 BM: z= (118)  BM =3.8/arcmin 2 n BM =1.7x10 -3 Mpc gals at z= (Steidel et al. 2004; Adelberger et al. 2004) BX/BM/LBG with R<=25.5 Other surveys & space densities: K20 (z= ): ~10 -4 /Mpc 3 GDDS (z= ):~10 -4 /Mpc 3 SMG (z~2.5): ~10 -5 /Mpc 3 FIRES(z=2-3.5): uncertain

9 Other redshift desert surveys Other surveys with galaxies at z~ K20/BzK (Cimatti et al.) (K<20 selection) (~40) Gemini Deep Deep (Abraham et al.) (K<20.6, photo-z) (34) FIRES (Franx, van Dokkum et al.) (J-K selection) (~10) Radio-selected SMG (Chapman et al.) (73) (+18 OFRG) Now that there are several groups using different selection techniques to find galaxies at z~2, we need to understand how the samples relate to each other.

Dust: Bolometric Luminosities and Extinction

11 Mid-IR Lum. from Spitzer/MIPS (Reddy et al. 2005) Spitzer/MIPS 24  m band probes PAH emission at z= , probe of L 5-8  m Average ratio of L 5-8 to L IR is 28.3 for local star-forming galaxies; use this to convert MIPS to bolometric IR luminosities Optical and near-IR- select gals at z~2 have ~3-5x10 11 L 

12 Mid-IR Lum. Vs. L X (bol) (Reddy et al. 2005) Using z~2 galaxies in the GOODS-N field, it is possible to do X-ray “stacking” analysis, as a function of L 5-8 ( gals per bin) L X probes bolometric SFR (not AGN) Strong linear correlation between L 5-8 and L X Evidence that L 5-8 is a good SFR indicator

13 Mid-IR Lum. Vs. L FIR (bol) (Reddy et al. 2005) Compare L FIR derived from L 5-8 with LFIR measured from SCUBA and other sources For SCUBA/SMG sources, FIR inferred from MIR is low by a factor of ~2-10 (T dust, AGN) We need direct comparisons for fainter galaxies (CCAT)!!

14 L bol vs. Dust Extinction (Reddy et al. 2005) Relationship between L bol and extinction evolves from z~0 to z~3 Galaxies at fixed extinction are ~100X more luminous (or galaxies at fixed luminosity are less dusty) Geometry, evolution of dust distribution Direct L bol at high-z is critical for this analysis CCAT will provide this (T dust, L bol )

Metallicities & Gas Fractions

16 Evolution of Galaxy Metallicities Gas phase oxygen abundance in star-forming galaxies Fundamental metric of galaxy formation process, reflects gas reprocessed by stars, metals returned to the ISM by SNe explosions (HII regions in sf-galaxies, stars in early-type). Departures from closed-box expectations can reveal evidence for outflow/inflow Galaxies display universal correlations between Luminosity (L), Stellar mass (M), and metallicity (Z) 10,000s of galaxies in the local universe with O/H Now the challenge is to obtain these measurements at high redshift (evolution will give clues) Measuring gas fractions is very important to quantify how much material has been processed into stars -- currently very indirect!!!

17 Abundance Indicators: Bright (R 23 ) (Kobulnicky et al. 1999) High-Z branch: R 23 decreases as Z increases Low-Z branch: R 23 decreases as Z decreases Uncertainty in which branch R 23 corresponds to Systematic differences from direct method

18 Local L-Z Relationship (Tremonti et al. 2004) Lots of local emission line measurements (10000’s, 2dF, Sloan) At z=0.5-1, 3 groups (>=200 gals, CFRS, DGSS, CADIS, TKRS) At z>2 there were < 10 measurements (mainly LBGs) DLAs provide metallicity information from abs lines, but hard to relate

19 Local M-Z Relationship (Tremonti et al. 2004) M-Z possibly more fundamental than L-Z relationship closed box model relates gas fraction and metallicity, according to the yield SDSS sample revealed lower effective yield in lower mass galaxies importance of feedback

20 Near-IR spectroscopy of z~2 gals z~2 ideal for measuring several neb lines in JHK evidence of M-Z relation at z~2, gas fractions are necessary part of interpretation (CCAT)

21 [NII]/H  ratios: z~2 metallicities relationship between [NII]/H  and O/H N is mixture of primary and secondary origin age, ionization, N/O effects, integ. spectra, DIG, AGN (Pettini & Pagel 2004) N2=log([NII] 6584/H  ) 12+log(O/H)= xN2  ~0.18, factor of 2.5 in O/H

22 z~2 M-Z Relationship (Erb et al. 2005) New sample of 87 star-forming galaxies at z~2 with both M * and [NII[/H  (gas phase O/H) measurements Divide into 6 bins in M *, which increases as you move down clear increase in [NII]/H  with increasing M * M-Z at z~2!!

23 z~2 M-Z Relationship (Erb et al. 2005) Evol. Comparison with SDSS, where Z is based on [NII]/Ha (for both samples) Clear offset in relations --> at fixed stellar mass, z~2 galaxies significantly less metal rich than local gals Not evolutionary (z~2 probably red&dead by z~0)

24 z~2 M-Z Relationship (Erb et al. 2005) Important: measure change of Z with  (gas fraction) Must estimate M gas, which we do from  H , to  sfr, to  gas (assuming Schmidt law) Very indirect! Low stellar mass objects have much higher 

25 z~2 M-Z Relationship Different models for feedback, using different yields and different outflow rates Data are best fit by model with super-solar yield and outflow rate greater than SFR (for all masses) Rate of change of  with metallicity gives evidence for feedback ;  is very important (measure with CCAT, CO lines) (Erb et al. 2005)

HII Region Physical Conditions

27 z~2 Physical Conditions Well-defined sequence in [OIII]/H  vs. [NII]/H  in local galaxies (SDSS) (star-formation vs. AGN) z~2 star-forming galaxies are offset from this locus (as is DRG) n e, ionization parameter, ionizing spectrum (IMF, star-formation history) Implications for derived O/H (Erb et al. 2005)

28 z~1 Physical Conditions Well-defined sequence in [OIII]/H  vs. [NII]/H  in local galaxies (SDSS) (star-formation vs. AGN) z~1.4 star-forming galaxies are offset from this locus (as is DRG) n e, ionization parameter, ionizing spectrum (IMF, star-formation history) Implications for derived O/H (Shapley et al. 2005)

29 z~2 Physical Conditions Among K<20 galaxies (brightest 10%), [SII] line ratio indicates high electron density Inferred electron density is ~1000/cm 3, This is higher than in local HII regions used to calibrate N2 vs. O/H relationship (Pettini et al. 2005)

30 Beyond [NII]/Ha: All the lines (van Dokkum et al. 2005) H N OHO Deriving Oxygen Abundance from [NII]/H  relied on several assumptions Physical conditions appear different. Observations of full set of lines important for constraining sfr in high redshift objects GNIRS/Gemini

31 Beyond [NII]/Ha: All the lines (van Dokkum et al. 2005) H N OHO FIR [OIII] lines, accessible with CCAT at >200  m for z>1.5 independent probe of HII region physical conditions [CII] 158  m line, probes physical conditions in different phase (compare with CII* 1335)

32 Summary New results about dust, star formation, chemical enrichment, and feedback, using optical, near-IR, and mid-IR imaging and spectroscopy CCAT observations can provide independent measurements of dust, gas, and star-formation rates for these objects, as well as probing physical conditions Both continuum and line emission measurements will be crucial for physical understanding

33 Q : Distribution of M* M star,med =2.0x10 10 M sun Distributions with and without IRAC data very similar (uncertainties smaller with IRAC data) Stellar mass density of z~2 BX/MD galaxies is ~10 8 M sun Mpc -3 16% of z=0 stellar mass density (Cole et al. 2001) caveats: IMF, bursts relate to z~3, evolution (???? Weak constraints) Better constraints for most massive gals (8%) (Steidel et al. 2005) 6/72 have M*>10 11 M  & contain 50% of the mass

34 Direct Abundance Determination Use [OIII] 4363/(5007,4959) to get T e, [SII] to get n e Problem: 4363 weak, even in local low-Z gals; star-forming gals are not very metal-poor--NO HOPE at high redshift (figure from van Zee 2000) Z=1/25 Z sun

35 L-Z relation and evolution (Garnett 2002) Evolution of L-Z provides clues… Correlation over 11 mags in M B and factor of 100 in (O/H) (SF gals) Ellipticals show analogous trend Fainter gals have higher gas fraction (younger, lower  sfr ); or outflows more important

36 Stellar Populations & Masses Near/Mid-IR Imaging Deep J, K imaging with WIRC, Palomar 5-m, to K s ~22.5, J~ fields, ~420 galaxies with z sp > 1.4 Spitzer IRAC data in Q1700 field, 3.6, 4.5, 5.4, 8  m Use for modeling stellar populations, masses Ks (2.15  m) (Barmby et al. 2004, Steidel et al. 2005)

37 Stellar Populations & Masses Near/Mid-IR Imaging Deep J, K imaging with WIRC, Palomar 5-m, to K s ~22.5, J~ fields, ~420 galaxies with z sp > 1.4 Spitzer IRAC data in Q1700 field, 3.6, 4.5, 5.4, 8  m Use for modeling stellar populations, masses IRAC (4.5  m) (Barmby et al. 2004, Steidel et al. 2005)

38 Near-IR spectroscopy of z~2 gals H  spectra of 101 z~2 gals KeckII/NIRSPEC Kinematics: linewidths, M dyn, some spatially- resolved, tilted lines, compare with stellar masses Line ratios: HII region metallicities, physical conditions H  fluxes: SFRs, compare with UV, models Offsets between nebular, UV abs and Ly  em redshifts -> outflows M*=4  M  K=19.3, J-K=2.3 M*=5  10 9 M 

39 Measuring gas masses at z~1-3 In addition to filling in huge gap in O/H vs. z, and testing evolution of L-Z relation…. In simple closed-box chemical evolution models: Z=y ln (1/  )  =M gas /(M star +M gas ), y=yield of heavy elements Using broad-band photometry, fit stellar populations and determine M star Test for the importance of outflows (effective yield)

40 Measuring O/H at z~1 At z~ , [NII]/H  in H- band, [OIII]/H  in J-band At z~1, [NII]/H  in J-band, [OIII]/H  in NIRSPEC1 band DEEP2 gals already have [OII] DEEP2 z-hist from Coil et al. 2004, ~5000 gals, 10% of survey Statistical O/H sample (50-100) at z=1-1.5

41 Different Estimates of Dust (Reddy et al. 2005)  measures dust from UV slope L FIR /L 1600 measures dust from inferred ratio of FIR (based on MIPS) to UV luminosity Local starbursts show correlation between  and FIR/UV MIPS implies correlation works for z~2 galaxies on avg.

42 Does Calzetti Work? Stack 171 z spec = S.F. galaxies (excluding all direct detections, AGN) 10  detection in X-ray  = 42 M sun /yr 5  detection in radio  =50M sun /yr (LIRG) Corresponds to = 8.5 M sun /yr = factor of 4.9, very similar to results at z~3, and to inference from UV colors with CSF+Calzetti K =130 M sun /yr (Reddy et al. 2005) Star-forming BzK gals: =170 M sun /yr (Daddi et al. 2004) Chandra Stack (CDFN 2Ms exposure) (Reddy & Steidel 2004)