cosmology with distant supernovae: where next?
DESCRIPTION
Cosmology with Distant Supernovae: Where Next?. Richard Ellis, Caltech. Zwicky SN Workshop, Carnegie Jan 17 2004. “Concordance Cosmology”: triumph or sham?. Concordance is worrying: DM 0.27 0.04 B 0.044 0.004 0.73 0.04 (Bennett et al 2003) - PowerPoint PPT PresentationTRANSCRIPT
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Richard Ellis, Caltech
Cosmology with Distant Supernovae: Where Next?
Zwicky SN Workshop, Carnegie Jan 17 2004
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“Concordance Cosmology”: triumph or sham?
Concordance is worrying:
• DM 0.27 0.04
• B 0.044 0.004
• 0.73 0.04
(Bennett et al 2003)
All 3 ingredients comparable in magnitude but only one component physically understood!
0: why this value and why acceleration now?
2dF
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CMB alone
Efstathiou et al (2001)Joint analysis of CMB + 2dF data
Contrary to popular belief CMB alone does not convincingly indicate spatial flatness if is unknown
CMB + 2dF
CMB + 2dF confirms spatial flatness and non-zero independent of any supernova data
WMAP+2dF/SDSS: Same idea, higher precision
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Remarkable conclusions demand remarkable evidence
Where next in cosmological applications?
• More of the same (Tonry et al 2003)
• Better data (HST z<1, Knop et al 2003)
• Higher redshift data (GOODS; Subaru)
• Check systematics
• Independent methods (e.g. SN II, Hamuy et al)
Role of SNe: Direct method for verifying cosmic acceleration
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More of the same: HiZ team
Tonry et al (2003)
• 23 new IfA/HiZ SNe
• but only 9 confirmed as Ia
• 0.34 <z < 1.09
• 15 with z > 0.7 (doubling #)
empty
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Better z < 1 HST data: SCP team
Knop et al Ap J 598, 102 (2003)
11 new HST SNe 0.36<z<0.86 higher quality multi-color data enabling E(B-V) measures
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GOODS SN Ia 2002fw z=1.3 (Riess et al 2003)
ACS grism 15ksec
(-- SN Ia 1981b)
Color discrimination of SNIa/II
based on the UV deficit of Ia’s
Probing to higher z with HST:(HDF: Gilliland et al 1999, Riess et al 2001)
SN1997ff: z = 1.7 0.1
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Bias in finding bluer SNe at high z?
Possible systematics in GOODs program locating SNe Ia via ACS 850LP measuring restframe B-band (and UV) with NICMOS F110W filter.
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Future HST surveys (GOODS, COSMOS..) will only modestly increase z > 1 sample (20-30 events)
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Investigating Systematic Effects
• Differential extinction – greater amounts of dust
in high z host galaxies: mimics > 0
• SN properties may depend on enviroment
e.g. galaxy type or mix (Hamuy et al 1996, 2000)
• Evolutionary differences e.g. progenitor composition
(Höfflich et al 1999)
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Evolution? Residuals from best fit to SN Hubble diagram (SCP 1999)
Low z
High z1 mag
Constant scatter (allowing for obs. errors) with z provides a (weak) case against evolution which would otherwise have to be well-orchestrated with cosmic time.
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Reddening? E(B-V) estimates for low & high z SNe in improved HST sample
Knop et al SCP 2003
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Hamuy et al AJ 120, 1479 (2000)
Morphology? Type-dependent SN Ia light curves
Type
B-V
m15(B)
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HST STIS Snapshot Program (Sullivan + RSE)
Cycle 8+10 STIS 50CCD (unfiltered) snapshot imaging (retrospective)
• host galaxy morphology
• precise SN location
• slit arrangement for diagnostic Keck spectroscopy
Sullivan et al MN 340, 1057 (2003)
STIS imaging: 59 targets
5 not observed/failed 2 no host visible 52 classified hosts (P99 42 + new)
Keck ESI: 16 targets
E(B-V) for 6
plus
24 low z SNe (Hamuy, Riess)
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SCP Hubble Diagram by Host Galaxy Type
Type N dispersion (flat) P(>0)
Spheroidal 13 (15) 0.167 0.60 (0.59) 97.9
Spiral 23 (28) 0.197 0.58 (0.58) 98.6
Late/Irr 23 (26) 0.265 0.75 (0.74) 99.9
Small offset of high z spheroidals (<0.01) from adopted SCP fit
• spheroidal
• spiral
• late/Irr
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Light curve “stretch” distributions at high/low z
Low z
High z
Unfortunately, the similar range in light curve “stretch” at low and high z means we cannot readily test for all possible systematic effects e.g. decline rate versus type as studied locally by Hamuy.
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Rest-frame color excess versus type (Sullivan et al)
E(B-V) = (B-V)obs – (B-V)0,s
Type
Little extinction in high z SNe and sensible type-dependent trends
MB (rest) = MB(spheroidal) + 0.07 from Hubble diagram
AV from 6 ESI spectra: 0.06-1.0 mag
Lack of Irregulars in the SN-selected sample c.f. HST-based z surveys
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Progenitor studies
• Spectroscopic evolution of selected high z SNe
c.f. improved local templates (SN Factory)
• Metallicity of progenitor?
detailed UV spectra near maximum
light (Nugent et al 1999)
• Nature of Ia progenitor: rate at as a function of z in field (Pain et al) and in clusters (Gal-Yam)
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Spectral Evolution of Distant SNe Ia
Q: What is the best diagnostic spectroscopic correlation that should be tested for a modest high z sample (z=0.5)
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Nugent et al (1995): Spectral Sequence of SNe Ia
R(Si II) blue/red
MB
R(Ca II)Synthetic & observed spectral sequence
L
Synthetic sequence reproduces trend via 7400 < Teff < 11000
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R(Si II) versus v10(Si II) (Hatano et al 2000)
Do SNeIa form a one parameter sequence: can we verify a sequence at high z?
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UV Opacity as Probe of SNIa Metallicity (Nugent et al 1999)
Strong UV dependence expected from deflagration models when metallicity is varied in outermost C+O layers (Lenz et al 2000)
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UV Trends in Nearby SNe Ia (STIS, Nugent)
Can we explore these trends at high z and correlate with Hubble diagram?
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CFHT Legacy Survey (2003-2008)
Megaprime
Deep Synoptic Survey
Four 1 1 deg fields in ugriz 5 nights/lunation 5 months per accessible field 2000 SNe 0.3 < z < 1
Caltech’s role
Spectral follow-up of 0.4<z<0.6 SNe Ia
Tests on 0.2<z<0.4 SNeII
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The Need for Photometric Pre-Classification
Nearby search Discovery Reference Difference CFHTLS SNe Ia from Sep 2003
• Hi-z SN spectra are much harder to take due to both their faintness & their separation from their host galaxy is comparable to the seeing. • Avoid wasting Keck time taking spectra of objects too close/wrong sub-type.
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Photometric redshifts/typing for distant SNe
New code SNphot-z pre-classes type, z & epoch prior to taking spectra: only practical for the CFHTLS multi-filter rolling search
• Templates from Gilliland, Nugent & Phillips (1999) updated from Nugent et al. (2002).
• Calculate color evolution as a function of epoch, z, type, extinction, stretch (Ia’s) in ugriz for all targets.
Spectral templates created by homogenizing IUE and HST observations + some modeling to fill in the gaps.
SN Ia template weekly for the first 7 weeks.
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SN Photo-Z: Results
Based on 3 epochs of photometry with only R & I data.
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CFHT Legacy Survey: Progress
• 17 SNIa 0.25<z<0.55 to correlate spectral dispersion with Hubble diagram residuals (in progress)
• 3 SNII 0.1<z<0.4 to explore feasibility of EPM/Hamuy methods
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Results: I - Extending Environmental Range
Ref Disc Sub
Unlike previous searches the CFHTLS SN search is finding SNe with very low % increases near the cores of bright galaxies, sampling a much broader range of environments. How do they differ?
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Results: II - Correlating Spectral Features
The large choice of CFHTLS SNe enables us to target for comparisons at same redshifts & epochs.
• Two SNe Ia near peak brightness both with z= 0.45. • Significant difference in Ca II H&K P-Cygni feature (split in 2003fh, smooth in 2003fg) • Significant UV flux differences. • Minor velocity shifts of the intermediate mass material (SiII and SII).
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Results: III - Dispersion in UV properties
z 0 STIS
z 0.5 Keck
Correlating metallicity/UV opacity with light curves is a major goal
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Can Cosmic Acceleration be deduced from SN II?
Hamuy & Pinto (2002) propose a new “empirical” correlation (0.2 mag, 9% in distance) between the expansion velocity at the plateau phase and bolometric luminosity for Type IIs.
If vindicated with more data, the Hubble diagram of SNII will provide a completely independent check of the cosmic acceleration using Keck
QUEST will locate nearby SNIIs on plateau phase; expansion velocities will come from override time on 200-inch to test this proposition
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Expected Numbers of Supernovae
Type Ia SNEUse Rate from R. Pain, et al. (APJ 577, 120, 2002)
Type II SNE• Typically 2 mags fainter than Ia’s
(Hamuy & Pinto APJ 566, L63, 2002)
• About twice as numerous per unit volume as Ia’s(Capellaro, et al., AA 351, 459, 1999)
Estimate numbers of SNe’s for 1000 square degrees, 15 day time window
Up to Z Peak m No/1000 sq deg
Peak m No/1000 sq deg
0.05 17.5 2 19.5 6
0.10 19.0 12 21.0 24
0.20 20.5 100 22.5 200
0.30 21.5 300 23.5 600
0.40 22.0 650 24.0 1300
Type Ia SNe’s Type II SNe’s
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Keck example: SN2001kf z=0.21 SNIIp (V=23.0)
Measuring the Fe II expansion is feasible at z 0.3 in 2-3 hours
10-20 SNeIIp free from systematics would confirm 0 at 3
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Conclusions
• Distant SN programs are entering new, more detailed phases utilising HST and high s/n spectroscopy to provide
increased astrophysical data for each event
global constraints on evolution & progenitor details. (exciting outcome whether acceleration supported or not)
• First enhanced datasets tend to support the SCP conclusions (SN in field spheroidals confirm 0.7 )
• CFHTLS will extend these SN Ia studies via spectral sequences based on metallicities/environment
• Palomar/QUEST2 will verify the utility of SNe II as cosmic probes: Keck may verify the acceleration!
• SNAP/JDEM represents the logical endpoint of the program
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SNAP/JDEM – combines SNe Ia and weak lensing as a unique probe of dark energy
http://snap.lbl.gov
Optical ( 36 CCD’s) = 0.34 sq. deg.
4 filters on each 10.5 m pixel CCD
IR (36 HgCdTe’s) = 0.34 sq. deg.
1 filter on each 18 m pixel HgCdTe
It should be called the Zwicky telescope!
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Conclusions not significantly affected by stretch corrections
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Distant SNeIa have similar spectra to local counterparts at same epoch
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More SNeIIp…
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The current situation – all literature data
Tonry et al (2003)
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SCP (1999): Intrinsic
reddening determined
from multicolor
light curves:
• insufficient precision
for use on individual
SN by SN basis,
• zero point uncertain
Reddening?
Provides case against overall relative reddening of high c.f. low z sample
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Grey dust?
Aguirre Ap J 525, 583 (2000): Grey dust requires larger grains with high metal content and may conflict with far IR background
Grain size (m)
E(B-R)/B
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Keck ESI Spectroscopic Program
Keck II Echellette Spectroscopic Imager:
R 25000 0.3-1m long slit
• emission line properties of host galaxy
(correlation with HST morphology)
• reddening estimate from H/H
• variance in above from longslit data
in good seeing
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Simulated Results from SNAP
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Host Galaxy Types
Classification of P99 sample of 42 into 3 broad types
spheroidal/ intermediate/ late
from:
• ESI (+LRIS) spectrum
• HST STIS image
• R-I color
z
R-I
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No dependence on projected radial distance
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Type versus stretch Stretch versus radius
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Detection efficiencies
Computed adding fake SN (stars) on real images (galaxies)
SN/galaxy relative brightness
Set A Set B
Set C Set D
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Program so far…
17 Type Ia’s at 0.25 < z < 0.55 with an average exposure time 4-5 * longer than what is normally taken during a high-z search program for a given supernova.
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Determining High Redshift SN Rate
To estimate rate we require:
• SN detection efficiency, i.e.control time t (z,L, )
• Volume and stellar luminosity probed at search limit
• Large number of SNe
Pain, Sullivan, RSE et al (2002) - old SCP search data
• 38 SNe from SCP: 0.25<z<0.85 from 12 deg2
<z> 0.55 rate is 0.58 0.09 (0.09) SNu
1.53 0.25 ( 0.32) 10-4 h3 Mpc-3 yr-1
1 SNu = 1 SN per century per 1010 LB (sun)
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SN rates as a function of redshift (Sullivan et al 2000)
SN Ia rate
SN II rate
z
SCP (Pain et al 2001)
=0.3 Gyr
=3 Gyr
Various SF histories (Madau et al 1999)
Must seek higher redshift SNe
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Origin of SNe Ia in single degenerate C-O WD systems (Nomoto et al 1999)
WD + red giant
Wind reduces rate
Short time delay
WD + MS in common envelope
AGB with C+O core
RG+He core
Significant time delay
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Why is a non-zero cosmological constant worrying?Why is a non-zero cosmological constant worrying?
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SN Photo-Z: Results - II
Best fit z = 0.96+/-0.07: Observed z = 0.979
Success rate is ~95% to 0.1 in z - helpful in separating Ia & II targets.