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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

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)