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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 Presentation
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Richard Ellis, Caltech
Cosmology with Distant Supernovae: Where Next?
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)
All 3 ingredients comparable in magnitude but only one component physically understood!
0: why this value and why acceleration now?
2dF
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
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
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
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
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
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.
Future HST surveys (GOODS, COSMOS..) will only modestly increase z > 1 sample (20-30 events)
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)
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.
Reddening? E(B-V) estimates for low & high z SNe in improved HST sample
Knop et al SCP 2003
Hamuy et al AJ 120, 1479 (2000)
Morphology? Type-dependent SN Ia light curves
Type
B-V
m15(B)
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)
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
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.
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
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)
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)
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
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?
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)
UV Trends in Nearby SNe Ia (STIS, Nugent)
Can we explore these trends at high z and correlate with Hubble diagram?
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
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.
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.
SN Photo-Z: Results
Based on 3 epochs of photometry with only R & I data.
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
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?
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).
Results: III - Dispersion in UV properties
z 0 STIS
z 0.5 Keck
Correlating metallicity/UV opacity with light curves is a major goal
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
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
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
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
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!
Conclusions not significantly affected by stretch corrections
Distant SNeIa have similar spectra to local counterparts at same epoch
More SNeIIp…
The current situation – all literature data
Tonry et al (2003)
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
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
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
Simulated Results from SNAP
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
No dependence on projected radial distance
Type versus stretch Stretch versus radius
Detection efficiencies
Computed adding fake SN (stars) on real images (galaxies)
SN/galaxy relative brightness
Set A Set B
Set C Set D
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.
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)
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
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
Why is a non-zero cosmological constant worrying?Why is a non-zero cosmological constant worrying?
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.