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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)

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cosmology with distant supernovae where next
Cosmology with Distant Supernovae: Where Next?

Richard Ellis, Caltech

Zwicky SN Workshop, Carnegie Jan 17 2004

concordance cosmology triumph or sham
“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?


efstathiou et al 2001 joint analysis of cmb 2df data
Efstathiou et al (2001)Joint analysis of CMB + 2dF data

CMB alone

CMB + 2dF

Contrary to popular belief CMB alone does not convincingly indicate spatial flatness if  is unknown

CMB + 2dF confirms spatial flatness and non-zero  independent of any supernova data

WMAP+2dF/SDSS: Same idea, higher precision


Role of SNe:Direct method for verifying cosmic acceleration

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)

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 #)

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


Probing to higher z with HST:

(HDF: Gilliland et al 1999, Riess et al 2001)

SN1997ff: z = 1.7 0.1

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

bias in finding bluer sne at high z
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
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 z

1 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.


Morphology? Type-dependent SN Ia light curves




Hamuy et al AJ 120, 1479 (2000)

hst stis snapshot program sullivan rse
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

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


24 low z SNe (Hamuy, Riess)

Sullivan et al MN 340, 1057 (2003)


SCP Hubble Diagram by Host Galaxy Type

• spheroidal


• late/Irr

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


Light curve “stretch” distributions at high/low z

Low 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.

High z


Rest-frame color excess versus type (Sullivan et al)


E(B-V) = (B-V)obs – (B-V)0,s

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
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
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(Ca II)

Synthetic & observed spectral sequence



R(Si II) blue/red

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
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
CFHT Legacy Survey (2003-2008)

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
The Need for Photometric Pre-Classification

Discovery Reference Difference

CFHTLS SNe Ia from Sep 2003

Nearby search

  • 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
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
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
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
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 SNE

Use Rate from R. Pain, et al. (APJ 577, 120, 2002)


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 daytime window

Expected Numbers of Supernovae

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

  • • 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

Optical ( 36 CCD’s) = 0.34 sq. deg.

4 filters on each 10.5mmpixel CCD

IR (36 HgCdTe’s) = 0.34 sq. deg.

1 filter on each 18mmpixel HgCdTe

SNAP/JDEM – combines SNe Ia and weak lensing as a unique probe of dark energy

It should be called the Zwicky telescope!



SCP (1999): Intrinsic

reddening determined

from multicolor

light curves:

• insufficient precision

for use on individual

SN by SN basis,

• zero point uncertain

Provides case against overall relative reddening of high c.f. low z sample

grey dust
Grey dust?


Grain size (m)

Aguirre Ap J 525, 583 (2000): Grey dust requires larger grains with high metal content and may conflict with far IR background

keck esi spectroscopic program
Keck ESI Spectroscopic Program

Keck II Echellette Spectroscopic Imager:

R  25000 0.3-1m 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

host galaxy types
Host Galaxy Types

Classification of P99 sample of 42 into 3 broad types

spheroidal/ intermediate/ late


• ESI (+LRIS) spectrum

• HST STIS image

• R-I color




Type versus stretch

Stretch versus radius

detection efficiencies
Detection efficiencies

Computed adding fake SN (stars) on real images (galaxies)

Set A

Set B

Set C

Set D

SN/galaxy relative brightness

program so far
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
Determining High Redshift SN Rate

1 SNu = 1 SN per century per 1010 LB (sun)

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

sn rates as a function of redshift sullivan et al 2000
SN rates as a function of redshift (Sullivan et al 2000)

SN II rate

Various SF histories (Madau et al 1999)

SN Ia rate

=0.3 Gyr

SCP (Pain et al 2001)

=3 Gyr


Must seek higher redshift SNe


Origin of SNe Ia in single degenerate C-O WD systems (Nomoto et al 1999)

AGB with C+O core

RG+He core

WD + MS in common envelope

WD + red giant

Wind reduces rate

Short time delay

Significant time delay

sn photo z results ii
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.