Weak Lensing Study of DM sub halos in Coma Cluster

T. FutamaseAstronomical Institute,

Tohoku University, Sendai, Japan29th Apr. 11 @Hangzhou

Collaborators: N. Okabe (ASIAA, Taiwan), Y. Okura(NAO, Japan)

Relation between Gerhard and Japan(and me)

On the behalf of all Japanese cosmologists I would like to celebrate 70th birthday of Prof. G. Boerner

His first post-doc was at Yukawa Institute, Kyoto University in 1969 where he worked with Profs. K. Sato and H. Bethe on Nuclear matter in Neutron star. In his popular book, Yukawa mentioned a young German physicist at the Institute with photograph. Since then he repeatedly visited and stayed various part of Japan including Kyoto, Tokyo, Sendai, and has collaborated with Prof. K. Sato and Y. Suto group, given many talks and encouraged many young scientists to study cosmologyI first met him at 1982 when I was a post-doc. in relativity group at Garching.Since then his group at MPA has a nice relation with me and many of his students came to Japan as JSPS post-doc. . I attended his 60 th birthday meeting at Shanghai. Until that time I did not know his age because his looking was not changed since I first met him(I mentioned this as “age problem”. At that time another age problem was popular in cosmology ). Today his looking is same as 10 years ago. I am sure he will be the same in next 10 years and more

Weak Lensing Search of substructures in Coma cluster

Is it possible to determine the mass function of substructure in cluster of galaxies by weak lensing using Hyper Suprime Cam?

Observational verification of CDM scenario of structure formation as well as formation dynamics of cluster

Suprime-Cam on Subaru

• Prime Focus Camera• 34’×27’FOV

1: Hyper Suprime Camera for SubaruNew wide field prime focus camera for high –z galaxy surveyMain purpose is to measure the cosmic equation of state(Dark energy) by observing cosmic shear and BAO( Baryon Acoustic Oscillation)

• Wide FOV (~10 times of S-Cam)• High resolution （ 3 times better than

the present at 1 micrometer ）

Project started at 2006 and will finish 2011( 科研費特定領域 )

HSC and SC

S-cam

Substructures in Coma cluster (z=0.0236)

Statistics of sub halos (spatial distribution, mass function) in clusters reflects the history of formation of clusters

Thus if we can observe many sub halos in cluster, we may be able to test CDM scenario of structure formation

One of the most massive relaxed clusters near usHSC is able to observe whole region of Coma in 1 night !!

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Let’s observe!

Is it possible?

As a preliminary study we made weak lensing analysis of small region in coma cluster by S-Cam with old CCD(present S-Cam has new CCD)

Two R-band image data from SMOKA(Subaru Archive Data)

Central region of r<30’ from CD galaxy NGC4874 (exp.time:42min)Outskirts region of r~30-60’ (exp.time: 6min)

Seeing was ~ 0.8”Source galaxies 20-25 AB mag

~23 arcmin^-2 background galaxies

This is just ~10% of the whole area of the cluster

N. Okabe, Y. Okura and TF, ApJ (2010)

Not really perfect data for weak lensing

~400 /h kpc

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Mass Profile of Substructure)()()( 21 bbc

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Effect of LSS

March Observation• 5 half nights observation proposal were accepted in last Dec • Observation were performed in early March and 4 half nights were

perfect condition with seeing ~0.5” and n~70/arcmin^2• Two bands(Rc and V) observation to make a clear separation

between member galaxies and background galaxies

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Archive Data

March Observation

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Preliminary results

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Earth quake with mag. 9 has hit around Sendai area at 11th of March, and we have to stop every scientific activities for a month or so

Background selection: 20-25.7 AB mag, smoothing scale FWHM=3.3 arcmin

FOV of HSC

S/N>4 peaks

If we change smoothing scale to FWHM=2 arcmin, but some of peaks may be LSS origin

FWHM=3.3 arcmin FWHM=2 arcmin

23 peaks~100 peaks

Comparison between galaxies and DM sub halos

Luminosity map of member galaxies by SDSS photo-z selection

Mass function of DM sub halos(very preliminary)

Soon we will do• More detailed analyses separation between member and background 　 using color information

• Accurate determination of mass and mass profile of DM sub halos• Determination of mass and mass profile of main halo• Effect of LSS Use our V-band images and SDSS data as we did before (N. Okabe, Y. Okura and TF, 2010) Use higher-order weak lensing effect Flexion detection using HOLICs technique (Y. Okura.K. Umetsu and TF,2008; Y. Okura and TF, 2010)

Statistical properties of DM sub halos such as number, radial distribution, mass function et al. and relation of distribution between baryon and DM

Mass and Light in A1689 (Subaru)

Mass + Light contours from Shear+Magbias data (Umetsu & Broadhurst 07)

Mass map from Fleixon in a 4’x4’ region (Okura, Umetsu, & Futamase 2007b)

15 arcmin (2Mpc/h)

Using HSC

By observing nearby clusters z<0.05 with various stage of evolution, we will know the detail of cluster formation process

Since gravity is scale-free, we will also have some information of galaxy formation

Statistical properties of DM sub halos will give us not only an observational test of CDM structure formation scenario, but also important information of the nature of DM

We have been observing ~50 clusters (LoCuss) with 0.15<z<0.3 by Subaru for about 5 years, HSC will be able to observe ~50 clusters less than 1 year