Observations of High Redshift Galaxies with CCAT

Alice Shapley (Princeton University)

October 10th, 2005

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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

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New results • Spitzer 24 m observations provide estimates of Lbol for L~1011-1012 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

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Relevant Observations with CCAT • submm continuum --> LFIR, Lbol, Tdust

• CO lines --> Mgas (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

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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)

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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)

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Redshift Distributions

Unsmoothed

LBG: z~3 (940) SLBG=1.7/arcmin2

nLBG=1.4x10-3Mpc-3

BX: z=2-2.5 (816) BX=5.2/arcmin2

nBX=2.0x10-3 Mpc-

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BM: z=1.5-2.0 (118) BM=3.8/arcmin2

nBM=1.7x10-3Mpc-3

750 gals at z=1.4-2.5

(Steidel et al. 2004; Adelberger et al. 2004)BX/BM/LBG with R<=25.5

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Redshift Distributions

Unsmoothed

LBG: z~3 (940) SLBG=1.7/arcmin2

nLBG=1.4x10-3Mpc-3

BX: z=2-2.5 (816) BX=5.2/arcmin2

nBX=2.0x10-3 Mpc-

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BM: z=1.5-2.0 (118) BM=3.8/arcmin2

nBM=1.7x10-3Mpc-3

750 gals at z=1.4-2.5

(Steidel et al. 2004; Adelberger et al. 2004)BX/BM/LBG with R<=25.5

Other surveys & space densities:• K20 (z=1.4-2.5): ~10-4/Mpc3

• GDDS (z=1.6-2.0):~10-4/Mpc3 • SMG (z~2.5): ~10-5 /Mpc3

• FIRES(z=2-3.5): uncertain

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Other redshift desert surveys

Other surveys with galaxies at z~1.4-2.5

• 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

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Mid-IR Lum. from Spitzer/MIPS

(Reddy et al. 2005)

• Spitzer/MIPS 24 m band probes PAH emission at z=1.5-2.6, probe of L5-8m

• Average ratio of L5-8

to LIR 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 <LIR>~3-5x1011 L

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Mid-IR Lum. Vs. LX(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 L5-8 (10-20 gals per bin)

• LX probes bolometric SFR (not AGN)

• Strong linear correlation between L5-

8 and LX

• Evidence that L5-8 is a good SFR indicator

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Mid-IR Lum. Vs. LFIR(bol)

(Reddy et al. 2005)

• Compare LFIR derived from L5-8 with LFIR measured from SCUBA and other sources

• For SCUBA/SMG sources, FIR inferred from MIR is low by a factor of ~2-10 (Tdust, AGN)

• We need direct comparisons for fainter galaxies (CCAT)!!

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Lbol vs. Dust Extinction

(Reddy et al. 2005)

• Relationship between Lbol 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 Lbol at high-z is critical for this analysis

• CCAT will provide this (Tdust, Lbol)

Metallicities & Gas Fractions

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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!!!

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Abundance Indicators: Bright (R23)

(Kobulnicky et al. 1999)

• High-Z branch: R23 decreases as Z increases

• Low-Z branch: R23 decreases as Z decreases

• Uncertainty in which branch R23 corresponds to

• Systematic differences from direct method

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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

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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

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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)

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[NII]/H ratios: z~2 metallicities

• relationship between [NII]/Hand 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)=8.9+0.57xN2

~0.18, factor of 2.5 in O/H

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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!!

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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)

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z~2 M-Z Relationship

(Erb et al. 2005)

• Important: measure change of Z with (gas fraction)

• Must estimate Mgas, which we do from H, to sfr, to gas (assuming Schmidt law)

• Very indirect!

• Low stellar mass objects have much higher

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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

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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)

• ne, ionization parameter, ionizing spectrum (IMF, star-formation history)

• Implications for derived O/H(Erb et al. 2005)

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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)

• ne, ionization parameter, ionizing spectrum (IMF, star-formation history)

• Implications for derived O/H(Shapley et al. 2005)

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z~2 Physical Conditions

• Among K<20 galaxies (brightest 10%), [SII] line ratio indicates high electron density

• Inferred electron density is ~1000/cm3,

• This is higher than in local HII regions used to calibrate N2 vs. O/H relationship

(Pettini et al. 2005)

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Beyond [NII]/Ha: All the lines

(van Dokkum et al. 2005)

H NOHO• 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

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Beyond [NII]/Ha: All the lines

(van Dokkum et al. 2005)

H NOHO• 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)

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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

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Q1700+64: Distribution of M*• Mstar,med=2.0x1010 Msun

• Distributions with and without IRAC data very similar (uncertainties smaller with IRAC data)• Stellar mass density of z~2 BX/MD galaxies is ~108MsunMpc-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*>1011M &

contain 50% of the mass

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Direct Abundance Determination

• Use [OIII] 4363/(5007,4959) to get Te, [SII] to get ne

• 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 Zsun

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L-Z relation and evolution

(Garnett 2002)

Evolution of L-Z provides clues…

• Correlation over 11 mags in MB 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

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Stellar Populations & Masses Near/Mid-IR Imaging

• Deep J, K imaging with WIRC, Palomar 5-m, to Ks~22.5, J~23.8

• 4 fields, ~420 galaxies with zsp> 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)

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Stellar Populations & Masses Near/Mid-IR Imaging

• Deep J, K imaging with WIRC, Palomar 5-m, to Ks~22.5, J~23.8

• 4 fields, ~420 galaxies with zsp> 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)

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Near-IR spectroscopy of z~2 gals H spectra of 101 z~2 gals KeckII/NIRSPEC• Kinematics: linewidths, Mdyn, 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*=41011 M

K=19.3, J-K=2.3 M*=5109 M

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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/)• =Mgas/(Mstar+Mgas), y=yield of heavy elements

• Using broad-band photometry, fit stellar populations and determine Mstar

• Test for the importance of outflows (effective yield)

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Measuring O/H at z~1

• At z~1.3-1.4, [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

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Different Estimates of Dust

(Reddy et al. 2005)

• measures dust from UV slope

• LFIR/L1600 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.

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Does Calzetti Work?• Stack 171 zspec=1.4-2.5 S.F. galaxies (excluding all direct detections, AGN)

• 10 detection in X-ray <SFR(Xray)> = 42 Msun/yr

• 5 detection in radio <SFR(Radio)>=50Msun/yr (LIRG)

• Corresponds to <SFR(1500)> = 8.5 Msun/yr

• <A(1500)>= factor of 4.9, very similar to results at z~3, and to inference from UV colors with CSF+Calzetti

• K<20 z=1.4-2.5 BX/BM: <SFR(Xray)>=130 Msun/yr (Reddy et al. 2005) Star-forming BzK gals: <SFR(Xray)>=170 Msun/yr (Daddi et al. 2004)

Chandra Stack (CDFN 2Ms exposure)

(Reddy & Steidel 2004)