# Presentation: 431501

## Cross-Correlation of 2MASS with WMAP3: Implications for ISW 

- Anaïs Rassat (University College London)
*Kate Land (Imperial College London)*
* **Ofer Lahav (University College London)*

## Integrated Sachs-Wolfe Effect

## 2MASS Galaxy Survey

- Publicly available *eXtended Source Catalogue *(XSC)
- J, H, K bands (Near Infrared)
- ~1,650,000 Galaxies with magnitudes corrected for Galactic extinction.
**Analysis includes 69% sky & 1,250,000 Galaxies**
- Compare with *Cabr**é et al. 2006* (SDSS DR4):  ~16% (z ~ 1)
- 		*Scranton et al. 2003* (SDSS – LRGs) : ~ 8% (z ~ 0.45)
- 		*Fosalba and Gaztañaga 2003 *(APM): ~10% (z ~ 0.15)

## Slide 4

## 2MASS ⊗ WMAP3

- Auto-Correlation
- Cross-Correlation
- AoE statistic

## Auto-Correlation Function: ACF

| EXACT IN LINEAR THEORY |
| --- |

## Constant linear bias b from  Cgg(l)

- Constant linear bias b from  Cgg(l)

- 12 < K20 < 14

## Best fit

***Best fit***

## 2MASS ⊗ WMAP3

- Auto-Correlation		√
- Cross-Correlation
- AoE statistic

## 3rd Year WMAP Foreground reduced maps of Q,V and W bands

- Q band (41 GHz)

- V band (61 GHz)

- W band (94 GHz)

***Images from***
***WMAP Science Team***

## Method:

- Follow Afshordi et al. 2004 (WMAP1 ⊗ 2MASS)
- Perform Cross-Correlation in Harmonic Space:
- Cut Kp2 mask on WMAP3, Cut out 31% of 2MASS sky

- ALL of 2MASS with ILC map

| CORRELATION? |
| --- |

## Colourful Correlation

## 2MASS 4 Magnitude Bins with ILC map

| POSITIVE CORRELATION TREND FOR LOW MULTIPOLES? |
| --- |

## WMAP3 / 2MASS

-  ⊗
- Q, V, W, ILC WMAP3 maps
- Achromatic
- Trend
- 1σ from 500 simulations of CMB with 2MASS

## Changes between WMAP1 & WMAP3

- ■ WMAP3
- □ WMAP1
- Why is there a difference?

## TheoryExact in linear theory:Small angle approximation:

## Predicted Cross-Correlation: Exact & Small Angle Approximation:

- l ~ 11

**Shells with**
** ****z ~ 0.067 (>2.10****5****gal)**
**z ~ 0.084 (>4.10****5**** gal)**
**∆****χ****2**** = ****χ****2** ISW - **χ****2**NULL= 2

- ☼

|  |
| --- |

| OPEN COSMOLOGIES |
| --- |

**Or  f ~ 1.7  (~1.6)**

## Model Dependent Statistic

- Assume there is Dark Energy in a Ωk=0 Universe
- CgT [DATA] = h* CgT[ISW_fiducial]
- Without prior on σ8:	h ~ 1.7  or  2σ detection
- (Null detection corresponds to h < 0)
- With prior on σ8:		h ~ 1.6
- Etc.. Full Parameter Space needs to be investigated

## Slide 23

| ALTERNATIVE FIDUCIAL MODELS |
| --- |

| h ~ 1.7   
2σ Detection |
| --- |

## 2MASS ⊗ WMAP3

- Auto-Correlation         √
- Cross-Correlation		√
- AoE statistic

- Axis of Evil

- ☼

**l****=2**

**l****=3**

**l****=4**

**l****=5**

- WMAP3

- 2MASS

## Summary: 2MASS ⊗ WMAP3

- WMAP3 ⊗ 2MASS : within 1σ [NULL] (Model Independent)
- ISW (fiducial) : within 1σ [NULL]
- CgTDATA ~ 1.7 CgTFIDUCIAL  (Model Dependent 2σ Detection)
- AoE(WMAP) ≠ AoE(2MASS)
***Thanks to Filipe Abdalla, Niayesh Afshordi, Sarah Bridle, Carlo Contaldi, for comments, advice and assistance.***

## CCL

- Find 2MASS b = 1.4
- Cross-correlate 2MASS with WMAP3:
- Slight change from 2MASS with WMAP1
- Visible positive achromatic cross-correlation, suggestive of ISW effect, but also consistent with Null Hypothesis.
- Data fits ISW effect “too well”
- Marginalization over parameter space makes cross-correlation even less significant.
- Axis of Evil: other statistical test
- No significant correlation between AOE of WMAP and