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WFC3 EBL Collaborators: Tim Dolch, Ranga-Ram Chary, Asantha Cooray, Anton Koekemoer, Swara Ravindranath Near-Infrared Extragalactic Background Fluctuations Henry Ferguson (STScI)

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Near-Infrared Extragalactic Background Fluctuations. Henry Ferguson (STScI). WFC3 EBL Collaborators: Tim Dolch, Ranga-Ram Chary, Asantha Cooray, Anton Koekemoer, Swara Ravindranath. WFC3 H-band masked. Background. We have resolved 30-100% of the EBL We do not know how much is due to: - PowerPoint PPT Presentation

TRANSCRIPT

Page 1: WFC3 EBL Collaborators:

• WFC3 EBL Collaborators:– Tim Dolch, Ranga-Ram Chary, Asantha Cooray,

Anton Koekemoer, Swara Ravindranath

Near-Infrared Extragalactic Background Fluctuations

Henry Ferguson (STScI)

Page 2: WFC3 EBL Collaborators:

WFC3 H-band masked

Page 3: WFC3 EBL Collaborators:

Background• We have resolved 30-100% of the EBL• We do not know how much is due to:

– The wings of galaxies– The faint end of the LF post reionization– Sources at the epoch of reionization

•The night sky is bright compared to galaxies!

Galaxies

Adapted from Leinert 1998 Bock+ 06

Page 4: WFC3 EBL Collaborators:

Fluctuations in the Near-IR from HST• Thompson et al HST NICMOS:

– Detected sources emit 7 nW m2 sr-1 compared to DC-level estimate of 70 nW m2 sr-1 from Matsumoto+ 2005

– Sources of the remaining fluctuations are probably at z<8 (even for the longer-wavelength IRAC data).

Page 5: WFC3 EBL Collaborators:

IRAC 3.6μm

Page 6: WFC3 EBL Collaborators:

NICMOS H band

Page 7: WFC3 EBL Collaborators:

WFC3 H-band

Page 8: WFC3 EBL Collaborators:

WFC3 H-band masked

Page 9: WFC3 EBL Collaborators:

NICMOS masking from Thompson et al. 2007 (NICMOS )

Page 10: WFC3 EBL Collaborators:

Data Preparation

• Iteratively remove detector blemishes– Combined dithered images with some masking– Transfer combined image back to original image

geometries and subtract– Smooth and detect blemishes or persistence– Mask and recombine for the final image

• Create pure noise images in original detector coordinates

– Gaussian statistics okay for these images; match sky background

– Predicted RMS matches measured RMS to within a few percent

– Combine these just as for the real images

• Mask the detected sources– Ideally -- subtract the galaxy wings (work in progress)

Page 11: WFC3 EBL Collaborators:

Analysis Procedure• Create a shuffled version of the

image– Unmasked pixels are randomly

shuffled, removing correlations

• For both the shuffled and unshuffled version:

– Convolve the masked images with kernels of various sizes

– Compute the histogram of pixel intensities P(D)

• Subtract the shuffled P(D) from the unshuffled P(D).

– Excess is amplified when kernel matches the characteristic size of the sources

Page 12: WFC3 EBL Collaborators:

Simulated dataα=0.1,r=0.12” α=0.1,r=0.36”

α=0.5,r=0.12” α=0.5,r=0.36”

Page 13: WFC3 EBL Collaborators:

Validation

• Tests on simulated UDF data

• Pure Gaussians: – Recover power-law slope to about

σα=0.1– Recover size to about 10%

• (for an idealized model with Gaussians all the same size)

• Mixture of galaxy profiles:– power-law biased low by -0.1 ± 0.1– Characteristic size biased high by

1.2 ± 0.2

Page 14: WFC3 EBL Collaborators:

Preliminary results

• Simple power-law model:– N(M)~10αm

– Normalization fixed to match total counts 27<m<28

– Constant size modeled with Gaussians

• Best fit– F105W: α = 0.7, r = 0.24’’– F125W: α = 0.65, r = 0.24’’– F160W: α = 0.65, r = 0.24’’

• Steep slope is intriguing

Page 15: WFC3 EBL Collaborators:

Pure noise simulation

Page 16: WFC3 EBL Collaborators:

Pure noise + simulated galaxiesN(M)~100.5m ; radius 0.24”

Page 17: WFC3 EBL Collaborators:

WFC3 H-band masked

Page 18: WFC3 EBL Collaborators:

Near-IR Galaxy counts

• Faint-end slope is:– Much flatter than α=0.6– Similar in all three bands

• Less than 5% of the galaxies at H>26.5 are identified as Lyman-break galaxies at z>6.5

Page 19: WFC3 EBL Collaborators:

Correlations between bands

Simulated data – identical colors for all galaxies

Correlation after convolution with 4-pixel (0.24”) Gaussian

Page 20: WFC3 EBL Collaborators:

Correlation between J and H bands

Page 21: WFC3 EBL Collaborators:

Correlation between Y and H bands

Page 22: WFC3 EBL Collaborators:

Future Efforts

• Galaxy subtraction• More sophisticated models

– Galaxy size magnitude relation with scatter– Galaxy redshift and SED distributions

• Better calibration of hot pixels and persistence

• More data

Page 23: WFC3 EBL Collaborators:

Hubble Multi-Cycle Treasury Program

• WFC3 IR observations of 5 well-studied reference fields at high galactic latitude:– The GOODS fields

• Encompass the deepest fields from HST, Spitzer, Chandra, the VLA, and soon Herschel

– Carefully selected portions of • The Extended Groth Strip• the COSMOS field• The UKIRT Ultradeep Survey Field

• Optimized for studies of galaxy evolution at z~2-10• Optimized for supernova cosmology

Theories crumble, but good observations never fade.— Harlow Shapley

Page 24: WFC3 EBL Collaborators:

90 Co-investigators

Page 25: WFC3 EBL Collaborators:

Observing strategy

• Wide fields:– ~750 sq. arcmin (44-45 tiles)– 2/3 orbits J (F125W)– 4/3 orbits H (F160W)

• GOODS Deep:– ~130 sq. arcmin– 11 orbit depth 3+4+4 – F105W+F125W+F160W– At least 12 orbits new ACS F814W

• UV (GOODS-N):– ~70 sq. arcmin– Lyman-escape fractions at z~2.5– 2.6:1 ratio in F275W:F336W

Page 26: WFC3 EBL Collaborators:

Potential for EBL measurements• HST Multicycle treasury program will cover 830 square arcminutes

at 1.2 and 1.6 microns to 27-28 magnitude

• Fluctuation measurements on larger scales will be possible

Reionization Simulation from Trac and Cen 2007

• The large angle (θ ~ 1/30 °) peak (green curve) is a linear-theory prediction of clustering of reionization sources.

• Small scale power is sensitive to the slope and normalization of the luminosity function and the sizes of the sources.

• large area surveys with WFC3 can (barely) reach large angle peak

Large θ Small θ

Page 27: WFC3 EBL Collaborators:

Summary

• A new technique for analyzing the small-scale structure in the EBL:– Fit difference of P(D) and shuffled P(D) after

convolving with a kernel– Constrains both the number-counts slope and the

power-law index 1-2 mag fainter than detection limit.

• Preliminary analysis suggests fluctuations well in excess of extrapolation of observed counts– In Y, J and H bands.– Unlikely to be reionization sources

• Possible systematic effects remain– Wings of galaxies; persistence