Transcript DESpec: Key Science Goals - DES and needs for spectroscopy per probe - The landscape of spectroscopic surveys - Improving DE FoM with.

DESpec: Key Science Goals
- DES and needs for spectroscopy per probe
- The landscape of spectroscopic surveys
- Improving DE FoM with DESpec+DES
- DE vs. Modified Gravity with DESpec+DES
- Neutrino Mass with DESpec+DES
- Required calculations and challenges ahead
Ofer Lahav
University College London
What will be the next paradigm shift?
• Vacuum energy (cosmological constant)?
• Dynamical scalar field?
– w=p/
– for cosmological constant: w = -1
• Modified Gravity?
• Inhomogeneous Universe?
• What if cosmological constant after all?
• Multiverse?
• The Anthropic Principle?
The Landscape of Surveys
2011-2020
Photometric surveys: DES*, VISTA, Pan-STARRS, HSC,
Skymapper, PAU*, LSST*, …
Spetroscopic surveys: WiggleZ, BOSS, e-BOSS, BigBOSS*,
DESpec*,HETDEX*, Subaru/Sumire*, VISTA/spec*, SKA, …
Space Missions: Euclid vs. WFIRST
(*) Talks at this meeting
The Dark Energy
http://www.darkenergysurvey.org
The Dark Energy Survey
• 4 complementary techniques:
Cluster Counts
Weak Lensing
Large Scale Structure
Supernovae Ia
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8-band survey
5000 deg2 grizY + JHK from VHS
300 million photometric redshifts
Survey 2012-2017 (525 nights)
First Light: October 2011 !
Blanco 4-meter at CTIO
DES Science Committee
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SC chair: O. Lahav
Large Scale Structure: E. Gaztanaga & W. Percival
Weak Lensing: S. Bridle & B. Jain
Clusters: T. McKay & J. Mohr
SN Ia: J. Marriner & B. Nichol
Photo-z: F. Castander & H. Lin
Simulations: G. Evrard & A. Kravtsov
Galaxy Evolution: D. Thomas & R. Wechsler
QSO: P. Martini & R. McMahon
Strong Lensing: L. Buckley-Geer & M. Makler
Milky Way: B. Santiago & B. Yanny
Theory & Combined Probes: W. Hu & J. Weller
The SC reports to the MC, chaired by DES Director J. Frieman
Photo-z – Spec-z -Dark Energy
cross talk
• Approximately, for a photo-z slice:
(w/ w) = 5 (z/ z) = 5 (z/z) Ns-1/2
=> the target accuracy in w
and photo-z scatter z dictate the number of required
spectroscopic redshifts
Ns =105-106
Excess power on Gpc scale:
systematics or new physics?
Thomas, Abdalla & Lahav (2011)
Using MegaZ-LRG (ANNz Photo-z)
Standard rulers
Redshift Distortion as a test
of Modified Gravity
Guzzo et al. 2008
Credit: Chris Blake
DESpec: Spectroscopic follow up
of DES
• Proposed Dark Energy Spectrometer (DESpec)
• 4000–fibre $40M instrument for the 4m Blanco telescope
in Chile (same as DES) – Tom Diehl’s talk
• 10 million galaxy spectra, target list from DES, starting
2017
• Spectral range approx 550 to 1080nm, R=1500
• DES+DESpec can improve DE FoM by several
• DES+DESpec can distinguish DE from ModGrav
• In the UK we submitted SoI to STFC, alongside 4 other
SoI’s on spectroscopic surveys
Possible DESpec survey strategies
• (A) 100% spectroscopic completeness of the DES galaxies
to r=21 mag, with redshift precision of 50 km/sec
• (B) The above plus 50% completeness to r=22.5 mag
evenly distributed over all redshifts bins (using photo-z
information to distribute the target selection in redshift)
• (C) Redshift precision of ~300km/s with 100%
completeness to r=22 mag
Questions presented to DES WGs
• How significant it is to have the spectroscopic follow up for
your probe?
• How would the DE FoM be improved for your probe?
• What other analyses can be done with spectroscopy (eg
redshift distortion, removing of intrinsic alignments for WL,
galaxy properties, etc.)
• What magnitude and colour cuts, survey area and spectral
resolution would be ideal for your science?
• Any other clever ideas for utilizing specroscopy?
DESpec: benefits per probe
• Photo-z/spec TF: better photo-z calibration (Abdalla)
• LSS: RSD and radial BAO (Percival), FoM improved by
several (3-6)
• Clusters: better redshifts and velocity dispersions (Gerke),
FoM up by several
• WL: little improvement for FoM (as projected mass, but
may help with IA)
• WL+LSS: a lot for both DE and for ModGrav (Gaztanaga,
Kirk, Bacon)
• SN Ia: Spectra of host galaxies and for photo-z training,
improving FoM by 2 (Sako)
• Galaxy Evolution: galaxy properties and star-formation
history (Thomas)
• Strong Lensing: improved cluster mass models
LSS improvement with DESpec
Assume for 10 million spectra over 0.2<z<1.7
(sample 1)
FoM (DESpec+DES4+II+Planck) / FoM(DES4+II+Planck) = 3 - 6
Percival & Samushia
DES(WL) + DESpec(LSS)
10 million spectra
with uniform
density over
0.2 < z < 1.7
Note these are
sensitive to
assumed priors
Kirk, Lahav & Bridle, in prep
Deviations from standard GR?
Lensing is sensitive to the sum of potentials,
while velocities respond to the temporal potential
Reyes et al. (Nature, 2010)
Claimed GR is confirmed from
lensing and galaxy velocities
Dark Energy vs Modifed Gravity
DES-like (WL, clusters, SN, BAO)
Assumed DE
Assumed Mod Grav
Shapiro et al. (2010)
Combining imaging & spectroscopy
to constrain modified gravity
Guzik, Jain & Takada 2009
Neutrinos decoupled when they were still
relativistic, hence they wiped out structure
on small scales
k > knr = 0.026 (m /1 eV)1/2 m1/2 h/Mpc
 h2 = M/(94 eV)
Agarwal & Feldman 2010
CDM+
1.9 eV neutrinos
CDM
Neutrino mass from MegaZ-LRG
700,000 galaxies within 3.3 (Gpc/h)^3
0.05 < Total mass < 0.28 eV (95% CL)
Thomas, Abdalla & Lahav, PRL(2010)
Total Neutrino Mass
DES+Planck vs. KATRIN
M< 0.1 eV
M < 0.6 eV
t
Lahav, Kiakotou, Abdalla and Blake (2010) 0910.4714
Very interesting if DESpec+DES+Planck can reach 0.05eV
Calculations needed for
DESpec+DES
• Standard DE FoM with careful attention to k-range,
systematics and to priors, including Planck
• Modified Gravity vs. DE (new metrics needed) and
neutrino mass
• Impact of spectral range and resolution on the probes
• Optimal survey strategy
• Quantify the benefits of same sky (phase correlations) for
DES and DESpec
* Impact of DESpec on future surveys (e.g. LSST and Euclid)
THE END
DES Synergy with VISTA
(8 filters together)
500 sq deg of the DES footprint (Stripe 82
and SPT region) already observed
in J, H, K (median depth 21.0, 20.8, 20.4)
850 sq deg by March 2011
M. Banerji and R. McMahon
DES Area and Depth: Synergy with South Pole
Telescope
• South Pole Telescope (10m,
bolometer array, 150, 250, 270 GHz):
• 2500 sq. deg. Survey (to end of
2011)
• to detect ~1,000 clusters
through Sunyaev-Zel’dovich
effect
• Dark Energy Survey:
measure photometric
redshifts for these clusters
to z ~ 1-1.3
Galactic Dust Map
Dark Energy Science Program
Four Probes of Dark Energy
• Galaxy Clusters
• clusters to z>1
• SZ measurements from SPT
• Sensitive to growth of structure and geometry
• Weak Lensing
• Shape measurements of 300 million galaxies
• Sensitive to growth of structure and geometry
• Large-scale Structure
• 300 million galaxies to z = 1 and beyond
• Sensitive to geometry
• Supernovae
• 15 sq deg time-domain survey
• ~3000 well-sampled SNe Ia to z ~1
• Sensitive to geometry
Plus QSOs, Strong Lensing, Milky Way, Galaxy Evolution
Neutrino mass from
DES:LSS & Planck
Input:
M =0.24 eV
Output:
M =0.24 +- 0.12 eV (95%
CL)
Lahav, Kiakotou, Abdalla & Blake 2010
(0910.4714)