Transcript Detailed Astrophysical Properties of Lyman Break Galaxies

Observations of High Redshift
Galaxies with CCAT
Alice Shapley (Princeton University)
October 10th, 2005
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 starformation feedback
• New results at shorter (optical through mid-IR)
wavelengths, CCAT observations will greatly
enhance their meaning
2
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
3
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
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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
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setup (Keck I/LRIS-B) (Steidel et al. 2004)
z>2 color-selection
• Adjust z~3 UGR crit. for z~2 (Adelberger et al. 2004)
• Spectroscopic follow-up with optimized UV-sensitive
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setup (Keck I/LRIS-B) (Steidel et al. 2004)
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
Unsmoothed
BM: z=1.5-2.0 (118)
SBM=3.8/arcmin2
nBM=1.7x10-3Mpc-3
750 gals at z=1.4-2.5
BX/BM/LBG with R<=25.5
(Steidel et al. 2004;
7
Adelberger et al. 2004)
Redshift Distributions
Other surveys & space densities:
LBG: z~3 (940)
• K20 (z=1.4-2.5): ~10-4/Mpc3 SLBG=1.7/arcmin2
• GDDS (z=1.6-2.0):~10-4/Mpc3nLBG=1.4x10-3Mpc-3
• SMG (z~2.5): ~10-5 /Mpc3
• FIRES(z=2-3.5): uncertain BX: z=2-2.5 (816)
SBX=5.2/arcmin2
nBX=2.0x10-3 Mpc-3
Unsmoothed
BM: z=1.5-2.0 (118)
SBM=3.8/arcmin2
nBM=1.7x10-3Mpc-3
750 gals at z=1.4-2.5
BX/BM/LBG with R<=25.5
(Steidel et al. 2004;
8
Adelberger et al. 2004)
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.
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Dust: Bolometric Luminosities
and Extinction
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
(Reddy et al. 2005)
• Optical and near-IRselect gals at z~2 have
<LIR>~3-5x1011 L
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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 (1020 gals per bin)
• LX probes bolometric
SFR (not AGN)
• Strong linear
correlation between
L5-8 and LX
(Reddy et al. 2005)
• Evidence that L5-8 is
a good SFR indicator
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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)
(Reddy et al. 2005)
• We need direct
comparisons for
fainter galaxies
(CCAT)!!
13
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)
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Metallicities & Gas Fractions
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
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indirect!!!
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
(Kobulnicky et al. 1999)
• Systematic
differences from
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direct method
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)
(Tremonti et al. 2004)
• DLAs provide
metallicity information
from abs lines, but
hard to relate
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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
(Tremonti et al. 2004)
• 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]/Ha ratios: z~2 metallicities
• relationship
between [NII]/Ha
and O/H
• N is mixture of
primary and
secondary origin
N2=log([NII] 6584/Ha)
12+log(O/H)=8.9+0.57xN2
s~0.18, factor of 2.5 in O/H
• age, ionization,
N/O effects, integ.
spectra, DIG, AGN
(Pettini & Pagel
2004) 21
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*
(Erb et al. 2005)
• M-Z at z~2!!
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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
(Erb et al. 2005)
• Not evolutionary (z~2
probably red&dead by
z~0)
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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)
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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
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very important (measure with CCAT, CO lines)
HII Region 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)
(Erb et al. 2005)
• Implications for derived
O/H
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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)
(Shapley et al. 2005)
• Implications for derived
O/H
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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)29
Beyond [NII]/Ha: All the lines
O
H O
HN
• 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
(van Dokkum et al. 2005)
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Beyond [NII]/Ha: All the lines
O
H O
HN
• 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)
(van Dokkum et al. 2005)
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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*
6/72 have
M*>1011M &
contain 50% of
the mass
(Steidel et al. 2005)
• 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%)
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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)
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L-Z relation and evolution
• Correlation over
11 mags in MB
and factor of 100
in (O/H) (SF gals)
• Ellipticals show
analogous trend
(Garnett 2002)
Evolution of L-Z provides clues…
• Fainter gals
have higher gas
fraction (younger,
lower Ssfr); or
outflows more
important 35
Stellar Populations & Masses
Near/Mid-IR Imaging
Ks (2.15 mm)
(Barmby et al. 2004, Steidel et al. 2005)
• 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
mm
• Use for modeling stellar
populations, masses
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Stellar Populations & Masses
Near/Mid-IR Imaging
IRAC (4.5 mm)
(Barmby et al. 2004, Steidel et al. 2005)
• 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
mm
• Use for modeling stellar
populations, masses
37
Near-IR spectroscopy of z~2 gals
M*=41011 M
K=19.3, J-K=2.3
M*=5109 M
Ha spectra of 101 z~2
gals KeckII/NIRSPEC
• Kinematics: linewidths,
Mdyn, some spatiallyresolved, 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 38
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)
39
Measuring O/H at z~1
• At z~1.3-1.4, [NII]/Ha in Hband, [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 40
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
(Reddy et al. 2005)
• 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)
• 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
Chandra Stack
(CDFN 2Ms exposure)
(Reddy & Steidel
2004)
• 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
42
Msun/yr (Daddi et al. 2004)