Update: Effects of Blending on Cluster Fields

Shenming Fu, Binyang Liu,

Ian Dell’Antonio

(Brown University)

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Cluster Field Simulation

• Background Field
• 304 postage stamps of isolated galaxies from HDF, UDF, GOODS, CANDELS at F606W
• Power law flux distribution 22<mag<28
• 2,463 UDF galaxies build statistics of mag vs r₅₀
• Simulate and lens 55,000 (~LSST) galaxies at z=1.5 with a c=4.0, 2*10¹⁵ M_sun NFW halo at z=0.3
• 12’x12’ ~ 3.4 Mpc at z=0.3

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Thank Daniel and more!

Cluster Field Simulation

• Foreground Cluster
• CLASH survey at z~0.3 with F606W
• 63 postage stamps of isolated galaxies
• 2,949 cluster galaxies at 0.2<z<0.451 to build statistics of mag, r₅₀ and distance to cluster center for sampling
• Simulate 1,000 galaxies obeying NFW with c=2 and truncate at r₂₀₀ ~ 2.4 Mpc ~ 8.7 arcmin

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0.065”/pix

Input correlations

Simulation

Cluster Field Simulation

What is the change of shear field after adding a foreground cluster image?

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Background field

Foreground cluster field

LSST PSF, Y10 Noise

6.7’ 1.8 Mpc z=0.3

DM Stack: HSM

• 80 PSF stars 19.25<mag<20 in 6.7’x6.7’
• DM v13 + obs_file
• Measure the ellipticity of the same background galaxy before and after adding the cluster image
• Find the average of 30 backgrounds (+90 degree rotation on each galaxy) and 30 clusters
• |shapeHSM_e1,2|<1.5
• Vary parameters

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DM Stack: HSM

Effects of blending on background galaxies

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DM Stack: HSM

Effects of blending on background galaxies: fractions

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DM Stack: HSM

Null tests

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DM Stack: HSM

Null tests: fractions

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DM Stack: HSM

How good is the detection of unlensed background galaxies before adding the cluster: effects of PSF, pixelation, noise and DM

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THELI: KSB

Similar behavior

Thank Jacqueline, Adrian, Anja, Doug and more!

THELI: KSB

Null tests

THELI: KSB

Fractions

THELI: KSB

Null tests: fractions

Two-galaxy model

Galfit; Sérsic profile; one galaxy is fixed at the center and stretched, the other is uniformly distributed in a bin-size square

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Two-galaxy model

Blending effects due to shear, size, and mag etc.

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DM: HSM

Reduce background galaxy size to half (real size in catalog) and increase number to 60000. (standard, cluster galaxy 500, c=4, gradient=0; top left to bottom right). Same trend as earlier.

Summary

• On average cluster-background galaxy blending gives 1% level error
• The effect is related to shear, number density (including concentration)

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Future

• Interim paper tracking
• DC2: more realistic mass distribution and galaxy distribution
• Multi-band: SCARLET deblender (Mengxin is working on that)
• Effects of blending on photo-z

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Thank you

• Thanks for listening
• Thank everyone for your help on this project
• Any questions/comments/suggestions?

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Cluster Database

687 low-z clusters selected with X-ray luminosity: collecting & reprocessing CFHT, DECam, Mosaic, Subaru/HSC, etc.; look for new targets for observation.

About 140 clusters have Lx>10⁴⁴ , dec<20, and R extinction < 0.5; many have partial data--it will take ~50 nights to complete them all in ugriz (4.5 hours/cluster). We should try! (survey proposals due end of september; letter of intent August 15)