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

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observations of high redshift galaxies with ccat

Observations of High Redshift Galaxies with CCAT

Alice Shapley (Princeton University)

October 10th, 2005

overview
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
new results
New results
  • Spitzer 24 mm 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
relevant observations with ccat
Relevant Observations with CCAT
  • submm continuum --> LFIR, Lbol, Tdust
  • CO lines --> Mgas (molecular, assuming conversion factor), gas fractions, Schmidt law
  • [CII] 158 mm, [OI] 63 mm, [OIII] 88, 52 mm --> (HII region and ISM physical conditions, densities, cooling)
  • Different probes of star formation
z 2 color selection
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)
z 2 color selection1
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)
redshift distributions
Redshift Distributions

LBG: z~3 (940) SLBG=1.7/arcmin2 nLBG=1.4x10-3Mpc-3

BX: z=2-2.5 (816) SBX=5.2/arcmin2 nBX=2.0x10-3 Mpc-3

BM: z=1.5-2.0 (118) SBM=3.8/arcmin2 nBM=1.7x10-3Mpc-3

750 gals at z=1.4-2.5

(Steidel et al. 2004; Adelberger et al. 2004)

Unsmoothed

BX/BM/LBG with R<=25.5

redshift distributions1

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
Redshift Distributions

LBG: z~3 (940) SLBG=1.7/arcmin2 nLBG=1.4x10-3Mpc-3

BX: z=2-2.5 (816) SBX=5.2/arcmin2 nBX=2.0x10-3 Mpc-3

BM: z=1.5-2.0 (118) SBM=3.8/arcmin2 nBM=1.7x10-3Mpc-3

750 gals at z=1.4-2.5

(Steidel et al. 2004; Adelberger et al. 2004)

Unsmoothed

BX/BM/LBG with R<=25.5

other redshift desert surveys
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.
mid ir lum from spitzer mips
Mid-IR Lum. from Spitzer/MIPS
  • Spitzer/MIPS 24 mm band probes PAH emission at z=1.5-2.6, probe of L5-8mm
  • 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

(Reddy et al. 2005)

mid ir lum vs l x bol
Mid-IR Lum. Vs. LX(bol)
  • 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

(Reddy et al. 2005)

mid ir lum vs l fir bol
Mid-IR Lum. Vs. LFIR(bol)
  • 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)!!

(Reddy et al. 2005)

l bol vs dust extinction
Lbol vs. Dust Extinction
  • 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)

(Reddy et al. 2005)

evolution of galaxy metallicities
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!!!
abundance indicators bright r 23
Abundance Indicators: Bright (R23)
  • 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

(Kobulnicky et al. 1999)

local l z relationship
Local L-Z Relationship
  • 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

(Tremonti et al. 2004)

local m z relationship
Local M-Z Relationship
  • 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

(Tremonti et al. 2004)

near ir spectroscopy of z 2 gals
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)
nii h a ratios z 2 metallicities
[NII]/Ha ratios: z~2 metallicities
  • relationship between [NII]/Ha 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/Ha)

12+log(O/H)=8.9+0.57xN2

s~0.18, factor of 2.5 in O/H

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

(Erb et al. 2005)

z 2 m z relationship1
z~2 M-Z Relationship
  • 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)

(Erb et al. 2005)

z 2 m z relationship2
z~2 M-Z Relationship
  • Important: measure change of Z with m (gas fraction)
  • Must estimate Mgas, which we do from SHa, to Ssfr, to Sgas (assuming Schmidt law)
  • Very indirect!
  • Low stellar mass objects have much higher m

(Erb et al. 2005)

z 2 m z relationship3
z~2 M-Z Relationship

(Erb et al. 2005)

  • 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 m with metallicity gives evidence for feedback ; m is very important (measure with CCAT, CO lines)
z 2 physical conditions
z~2 Physical Conditions
  • Well-defined sequence in [OIII]/Hb vs. [NII]/Ha 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)

z 1 physical conditions
z~1 Physical Conditions
  • Well-defined sequence in [OIII]/Hb vs. [NII]/Ha 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)

z 2 physical conditions1
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)
beyond nii ha all the lines
Beyond [NII]/Ha: All the lines
  • Deriving Oxygen Abundance from [NII]/Ha relied on several assumptions
  • Physical conditions appear different. Observations of full set of lines important for constraining sfr in high redshift objects
  • GNIRS/Gemini

O

H

O

H N

(van Dokkum et al. 2005)

beyond nii ha all the lines1
Beyond [NII]/Ha: All the lines
  • FIR [OIII] lines, accessible with CCAT at l>200 mm for z>1.5
  • independent probe of HII region physical conditions
  • [CII] 158 mm line, probes physical conditions in different phase (compare with CII* 1335)

O

H

O

H N

(van Dokkum et al. 2005)

summary
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
q1700 64 distribution of m
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%)

6/72 have M*>1011M &contain 50% of the mass

(Steidel et al. 2005)

direct abundance determination
Direct Abundance Determination

Z=1/25 Zsun

  • 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)
l z relation and evolution
L-Z relation and evolution
  • 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 Ssfr); or outflows more important

(Garnett 2002)

Evolution of L-Z provides clues…

stellar populations masses
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 mm)

(Barmby et al. 2004, Steidel et al. 2005)

stellar populations masses1
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 mm)

(Barmby et al. 2004, Steidel et al. 2005)

near ir spectroscopy of z 2 gals1
Near-IR spectroscopy of z~2 gals
  • Ha 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
  • Ha fluxes: SFRs, compare with UV, models
  • Offsets between nebular, UV abs and Lya em redshifts -> outflows

M*=41011 M

K=19.3, J-K=2.3

M*=5109 M

measuring gas masses at z 1 3
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)
  • m=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)
measuring o h at z 1
Measuring O/H at z~1
  • At z~1.3-1.4, [NII]/Ha in H-band, [OIII]/Hb in J-band
  • At z~1, [NII]/Ha in J-band, [OIII]/Hb 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
different estimates of dust
Different Estimates of Dust
  • b 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 b and FIR/UV
  • MIPS implies correlation works for z~2 galaxies on avg.

(Reddy et al. 2005)

does calzetti work
Does Calzetti Work?
  • Stack 171 zspec=1.4-2.5 S.F. galaxies (excluding all direct detections, AGN)
  • 10s detection in X-ray <SFR(Xray)> = 42 Msun/yr
  • 5s 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)

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