UCL’s interests:photo-z, mass-obs calibration, systematics

Granada, Sep 2010

Ofer Lahav,University College London

Ofer Lahav, Stephanie Jouvel, Ole Host University College London

Problems for LCDM on the ‘small scales’

• The MW satellites – too many in simulations?

• Cluster mass profiles – concentration too low in simulations?

• Hierachical clustering – the wrong order?

• Galaxies in voids- too many in simulations?

• Superclusters – too few in simulatons?

• Are we near a centre of a void?

Photometric and Spectroscopic surveys 2010-

2020

The Dark Energy Survey (DES)• Proposal:

– Perform a 5000 sq. deg. survey of the southern galactic cap;

– 300 million galaxies– Measure dark energy with

LSS, clusters, WL, SN • New Instrument:

– 2.2 FOV, 520 Mega pixel optical CCD camera + corrector

• Time scale:– Instrument Construction

2008-2011• Survey:

– 525 nights during Oct.–Feb. 2011-2016– Area overlap with SPT SZ

survey and VISTA VHS

Use the Blanco4m Telescope at the Cerro TololoInter-American Observatory (CTIO)

From Tom Broadhurst’s talk

Sample selection in Color-Color

• Red – background• Blue – background• Green – cluster

+~background• Pink – foreground

+background

A370

The zoo of photo-z codes

1.5M LRGs (“MegaZ”) photo-z code comparison

SDSS

HpZ+BC

Le PHARE

Zebra

ANNz

HpZ+WWC

Abdalla, Banerji, Lahav & RashkovCf. PHAT (Hildebrandt et al. 2010)

Sensitivity of Cosmology to photo-z methods

• Baryon Fraction

Omega_matter

Thomas, Abdalla & Lahav 2010

Photo-z challenges for CLASH

• Cluster, fg, bg membership with probabilities

• Try hybrid template + training methods • Biases in input photometry due to blending

and lensing • Optimal filters for WL (4-5) and for SL (16)• Spectroscopic training sets • “Self calibration”, “colour tomography”, “SB

prior”

The End

Neutrino mass from MegaZ-LRG700,000 galaxies within 3.3 (Gpc/h)^3

Thomas, Abdalla & Lahav, PRL (2010) 0911.5291

Total mass < 0.28 eV (95% CL)