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New Results from the Recent HST Surveys: COSMOS, GOODS, UDF. Plan of the talk:. Density-Morphology relation Discovery of a post-starburst galaxy at z ~7 Photometric redshift estimates Evolution of LF of galaxies to z~2 Narrow-band searches for high-z galaxies with Subaru. AIMS (COSMOS). - PowerPoint PPT Presentation
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New Results from the Recent HST Surveys: COSMOS, GOODS, UDF
Plan of the talk:
Density-Morphology relation
Discovery of a post-starburst galaxy at z ~7
Photometric redshift estimates
Evolution of LF of galaxies to z~2
Narrow-band searches for high-z galaxies with Subaru
AIMS (COSMOS)
• evolution of galaxy morphology, SFR, merging, LF, correlation function as a function of LSS and redshift
• Assembly of galaxies, clusters and dark matter up to 1014 Msun scales
• Reconstruction of dark matter distribution up to z >1
AIMS (UDF)
• Search for galaxies out to re-ionization epoch
• Extend study of star formation rate in galaxies to z ~ 6
• Study rest-frame optical properties of galaxies to high redshifts
• Estimate the luminosity function of galaxies at z ~ 6
AIMS (GOODS)
• Study of the mass assembly rate and star formation in galaxies
• Explore rest-frame morphologies of galaxies and their evolution with redshift
• Provide multi-waveband data to address fundamental questions regarding the formation and evolution of galaxies
COSMOS: Morphology-Density RelationCOSMOS: Morphology-Density Relation
Bahram Mobasher
Capak, Mobasher, Ellis, Scoville, Sheth, Abraham, ApJL 2005
Motivation:
Role of environment in shaping Hubble sequence 0<z<1
Ingredients:
ACS morphologies (+ proxies from photo-z/spectra)
Photometric redshifts (for slices)
Density estimates ( gals. Mpc-2 , lensing ….)
Stellar masses (requires deeper K-band)
Progress/issues:
Auto/visual morphologies & photo-z tested in 3 x 3 inner field
Robustness of 2-D as a tracer of 3-D density is an issue
Morphology-Density Relation: Progress & IssuesMorphology-Density Relation: Progress & Issues
Evolution of the T-Evolution of the T- relation 0 < z < 1 relation 0 < z < 1
Environmental density plays key role in governing morphological mix: - Continued growth in high but delay for lower regions - Slower conversion of spirals to S0s with only Es at z > 1?
Smith et al 2004 (astro-ph/0403455)
fE/S0 fE/S0
Evolution of the T-Evolution of the T- relation ACS clusters relation ACS clusters
Holland et al 2004 (astro-ph/0408165)
Explores the high end in more detail via GTO cluster sample (N=7, E:S0) Illustrates the advantage of combining COSMOS with cluster datasets?
fE/S0
COSMOS
Morphological Catalog (Abraham, Sheth + RSE)Morphological Catalog (Abraham, Sheth + RSE)
Morph-cat (RGA):
-based on earlier MDS, HDF precepts to I(AB)=24
- Asymm, Conc, Gini-C,
- N ~ ?
Reality check (RSE/KS):
- visual catalog I(AB)=22.5 in inner 33 g+I zone
- typed according to precepts used in MDS, HDF, GOODS
- N~700
Extension to full area:
N(tot) ~ ?
COSMOS T=5 Sc(d)m IAB<22.5
COSMOS T=1 E/S0 IAB<22.5
What limit for automated morphologies?What limit for automated morphologies?
Robustness of “classic” parameters (A-C test):
I(AB)=22.5 (COSMOS) is broadly equivalent to I(AB)=24 (HDF)
But how reliable is a projected 2-D density?But how reliable is a projected 2-D density?
Measured in a photo-z slice
True spatial density
/
Fidelity of using will depend on photo-z z, error and <z> itself (Benson VIRGO simulations)
Results
• Density-morphology relation was already in place at z~1
• We see a steady increase in the fraction of elliptical galaxies with decreasing redshift from z=1.2 to present
• The strength of this trend depends on the local density
Merging Photo-z & Morph-cats in the inner regionMerging Photo-z & Morph-cats in the inner region
V-I
Photo-z
Independent demonstration of robustness of photo-z’s
Search for the highest redshift galaxies
B. Mobasher, M. Dickinson,
H. C. Ferguson, M. Giavalisco,
T. Wiklind, R. S. Ellis, M. Fall
N. Grogin, L. Moustakas, N. Panagia
D. Stark, M. Sossy, M. Stiavelli E. Bergeron, S. Casertano, A.
Koekemoer, M. Livio, C. Scaralata
Mobasher et al (2005) submitted
Hubble Ultra-Deep Field
A sub-area of the GOODS-S (CDF-S)
CS Area: 3’ x 3’
mAB (z850LP) = 28.4 mag
(10for extended source over 0.2 arcsec2 aperture)
NICMOS Area: 2.5’ x 2.5’
mAB(F160W) = 25.1 mag.
(10for extended source)
GOODS-South
HUDF is fully
covered By Spitzer
HUDF+GOODS-S
ACS: B435V606 i775 z850LP
NICMOS: J110 H160
ISAAC: Ks
Spitzer: IRAC (3.6-8.0 micron)
MIPS: 24 micron
Radio 1.4 GHz (ATCA, VLA)
X-ray (Chandra)
Ground-based UBVRIJHK images
Photometric Redshifts -10% accurate
High-z selection
Sources with (J – H)AB > 1.3 and no detection in optical-ACS bands were
selected.
Two sources were identified. One close to an X-ray source (likely an
AGN) while the other is not associated with any X-ray (or radio)
source- UDF033238.7-274839
Spectral Energy Distributions
Simultaneously optimizing model parameters consisting of redshift (z),
extinction (E(B-V)), starburst age (tsb) and metallicity (Z)
Population synthesis models:
STARBURST99 (Vazquez & Leitherer 2005)
Bruzual & Charlot 2003
Associated with an X-ray source
Model Parameters
Parameter range:
Redshift 0 < z < 12
Extinction 0 < E(B-V) < 1
Starburst age 0.1 < tsb < 5 Gyrs
Metallicity 0.004, 0.008, 0.02, 0.04
Calzetti extinction law
Salpeter IMF 0.1 < M < 100 Msun
Star formation laws
Continuous SF mode
Instantaneous SF- single SF burst follwed by a decrease for tsb yrs
Exponentially decreasing SFR with e-folding time scale
0,100,200,300,400 Myrs
Best SED Fits
STARBURST99
Instantaneous star formation burst
z=7.2; EB-V =0.05; tsb=600 Myrs Z=0.004
Bruzual & Charlot
Exponentially decreasing SFR with 0
z=7.0; E B-V =0.15; tsb=400 Myrs Z=0.008
Degeneracies
It is possible that different combinations of parameters could
Produce equally acceptable fits.
low metallicity SED and high age or extinction could mimic an SED with
higher metallicity and lower age/extinction
Every single combination of
age (0.1-5 Gyrs)
Metallicity (0.2-2.5 solar)
Extinction (0 < E(B-V) < 1)
Redshift (0 < z < 12)
e-folding SFR (0-500)
is considered
It is possible that the observed SED is caused by:
• Contribution from old stellar population at z ~ 2-4
• heavily obscured starburst at lower redshifts
• Complicated degeneracy between redshift, extinction, metallicity, age
• An old population SED was simulated by fixing the age to 1-2 Gyr and fitting the rest of the parameters- no acceptable fit to the observed SED (at the > 5 level) was found at any redshift.
• To fit the observed SED with a heavily reddened object, one needs E(B-V) > 0.5 and a MUCH reduced likelihood.
Spectroscopic Campaign
Keck vs. Gemini
Gemini vs. VLT
VLT vs. Keck
Keck NIR SpectrumR. S. Ellis & D. Stark
ResultsHigh stellar mass of 8 x 1010 Msun
Galaxy formed the bulk of its stars very rapidly, entering a significant
quiescent phaseFormed today’s of Milky way mass when the Universe was 200-400 Myr
old (z=12-20)Evidence for monolitic formation
of galaxies ?Its SED is different from LBGs
JWST target ?
GOODS
Photometric redshift measurement
Evolution of rest-frame galaxy LF to z ~ 2
Narrow-band survey and nature of LAEs at z = 5.7- their Spitzer
properties
GOODS Phot-z MeasurementMobasher et al 2004, 2005
• six templates used• Luminosity function used as prior• Cosmic opacity from Madau et al.• Extinction allowed as a free parameter,
estimating E(B-V) for each galaxy• Interpolates the spectral types• Easily extended to other bands (ie IRAC,
GALEX etc)
Input: Galaxy magnitudes, magnitude errors, templates, filter response
functions
Output: z(phot), spectral types, redshift probability distribution,
conventional and prior-based redshifts, extinction
COSMOS phot-z’s: UBVRizK bands, E, Sa, Sb, Sc, Im, Starburst templates
Luminosity functions are calculated using* 1/Vmax method* Maximum likelihood method
Traditionally (ideally): each galaxy has one redshift-> one absolute magnitude-> one galaxy added to magnitude bin in LF
Using phot-z's:Phot-z's have relatively large errorsEach galaxy is represented by a redshift distribution
Evolution of rest-frame LFs
T.Dahlen, B.Mobasher,R.Somerville, L.Moustakas, M.Dickinson, H.C. Ferguson, M.Giavalisco ApJ 2005
Combine 1100 arcmin2 optical (UBVRI)- (RAB < 24.5) and 130
arcmin2 near-IR (JHK)-
(KAB < 23.2) surveys
Advantages…
• Deep and wide area near-IR data allow study of rest-frame optical LF to z~2
• Near-IR data allow us to probe deeper in the rest-frame optical LFs in the range z~1-2
• Allows study of rest-frame J-band LF (mass function) to z=1
• Allow measurement of SFR to z~2.2, using rest-frame 2800A measurements- compare to GALEX
LF Results• The shape of the LFs vary significantly
between different spectral types.
• Early-type galaxy show a near gaussian LF
• Starburst LFs have steep faint-end slopes
Dimming of 0.6 mag in M*J
between z=0.1 and 1
Results- evolution of rest-frame LFs
• Evolution of rest-frame U, B & R-band LFs are considered in six equal comoving volumes to z~2
• M* brightens by 2.1 (U), 0.8 (B) and 0.7 (R) mag between z~0.1 and z~2. There is a strong decline in * with redshift in U-band
• Rest-frame J-band LF shows a dimming between z~0.4 and 0.9 mean stellar mass was lower in the past
• There is strong evolution with redshift in the relative contribution from different spec. types to the luminosity density
SFR from rest-frame 2800A Mobasher et al 2005
Structure and Evolution of Starburst Galaxies
Mobasher et al (2004)Aims:How different is the morphology of starburst and normal
galaxies ?How significant is the effect of galaxy interactions on SFR ?Sample selection:Sample of SB galaxies is selected based on their spectral
types (from SED fitting). A Control sample of normal (E,Sp) galaxies was also selected in the same way.
Rest-frame B-band morphologies were determined, using BViz band ACS images and photometric redshifts
Concentration
• Most z<=1 optically selected starbursts have concentration indices which are significantly smaller than most early types
• C>0.3 : 12 % SB, 18% Late, 73% E/Sa
• Komogorov-Smirnov ( K-S) test
- SB vs Early type : 7e-7 (> 99.9%)- SB vs Late-type : 0.53
• Large C & galfit Sersic n=3-4 correlate
AGN fraction : CDF-S X-ray catalog : 2% of SB host AGN vs >25% of Early types
Asymmetry in rest frame B
• 55 % of z<=1 optically selected starbursts have high AB (>0.3) compared to lower fractions in late (20% ) and early (12%).
• K-S test on AB
- SB vs Early type : 1e-10 - SB vs Late-type : 3e-4
AB
Large AB : highly asymmetric distribution of massive SF (no m=2 symmetry)
- Externally triggered : tidal interactions, mergers
Narrow-band search for high-z galaxies
• A survey in NB816 over the GOODS-ACS area
• NB816 < 25
• I – NB816 > 0.7
• Not detected in B and V-bands
• 29 sources identified over the GOODS area
Rest-frame Properties of LAEsMobasher, Taniguchi, Ajiki 2005• 75% of narrow-band selected LAEs have
spect. Confirmation at z =5.7 (Rhoads et al 2003)
• No Spect. Data is yet available for our sample (BIG ASSUMPTION!)
• 18 (>60%) of the LAEs detected by IRAC
Sersic n dist. in rest-frame UV
rest-optical & -IR at z=5.8
• SST IRAC detections of z~6 galaxies=> stellar population & dust fitting possible
Dickinson et al in prep
ch1, 3.6mrest=5300A
ch2, 4.5mrest=6600A
SFR vs. Mass
Nature of LAEs
• Dominated by disk systems• Varied morphological types• SFR ~ 20 – 40 M(sun)/yr (estimated from
Ha line)• How is the LAEs SEDs compared to that of
the LBGs ?• ACS (iz) ISAAC (JHK) IRAC data
available