The dust content of galaxy clusters
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The dust content of galaxy clusters. Carlos M. Gutiérrez. Instituto de Astrofísica de Canarias Tenerife, Spain. Quy Nhon, August 2013. The dust content of galaxy clusters. Outline. Dust in astrophysics ( galaxies , intergalactic media and clusters )

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The dust content of galaxy clusters

Carlos M. Gutiérrez

Instituto de Astrofísica de Canarias

Tenerife, Spain

Quy Nhon, August 2013

The dust content of galaxy clusters


  • Dust in astrophysics (galaxies, intergalactic media and clusters)

  • Galaxyclusters

  • Previoussearches of dust in clusters (direct and indirectsearches)

  • Ourwork (methods and ingredients)

  • Results: maps of dust

  • Conclusions and futurework

The dust content of galaxy clusters

Dust in astrophysics

  • One of thecomponents (theothersbeing gas and stars) of galaxies.

  • Clearlydetected in theMilkyWay and in manyotherexternalgalaxies (basically of spiral and irregular types).

  • Veryinhomogeneusspatialdistribution.

  • Relativemodestcontribution in mass, butdustgrainsplayanimportant role in theintergalactic media and in thestarformationthatoccurswithin a galaxy.

  • Dustgrain can absorb and reddenbackgroundsources, so anaccurateknowledge of theamount and distribution of dustis crucial.

The dust content of galaxy clusters

Dust in theMilkyWay


The dust content of galaxy clusters

Clusters of galaxies: basic facts

  • Clusters of galaxies are the largest bound systems in the Universe. They contain 200-1000 galaxies.

  • First clusters formed at z~2 (i. e. age ~10 Gyr)

  • Dispersion of velocities between galaxy members indicate (Zwicky 30s’) large amount of dark matter.

  • Most of the barionic mass is in very hot gas in the intracluster media.

Detected in optical surveys

(e. g. DSS, SDSS, etc)



Detected in X-rays

The dust content of galaxy clusters

But, what about dust in clusters?

Galaxy members can contain significant amount of dust, but

the center of clusters is a hostile environment for intracluster dust grains to survive. In fact, dust grains are easily sputtered and destroyed in t~107-8 years (depending on size of the grains, density and temperature)

So, if dust in the intracluster media exists, it must have been injected at (nearly) present epochs.

The dust content of galaxy clusters

Possiblemechanismstoinjectdust in theintracluster media

  • Directaccretionfromtheintercluster media.

  • Galaxiesfallingintoclusters show gas and duststrippedfrom

  • them and injectedintotheintracluster media.

  • Expelledfromthegalaxymembers:

  • -byprocessseslike SN or AGN jets

  • -duringgalaxy-galaxymergers a significantamount of gas

  • (and dust) may be removed bycollisionalprocesses.

The dust content of galaxy clusters


Method 1: Indirect detection

-Comparison of counts (or reddening) of galaxies, quasars, and/or clusters behind clusters of galaxies with those on the field.

-Pioneeringworks: Zwicky (1962); Karanchetsev & Lipovetskii (1969); Bogart & Wagoner (1973); Boyle et al. (1988); Romani & Maoz (1992)

-Modern works (mostly SDSS based): Nollenberg et al. (2003); Chelouche et al. (2007); Muller et al. (2008); Bovy et al. (2008); McGee & Balogh (2010).

Av~0.2-0.5 mag

Av<~0.01 mag

-first studies affected by systematics

-NO detection of dust effects, Av~<0.01 mag

The dust content of galaxy clusters

  • Wise et al. (1993): IRAS maps of 56 clusters at 60 and 100 mm.Statisticaldetection : 138 mJy (60 mm) and 253 mJy (100 mm).

  • Stickel et al. (2002): ISO/ISOPHOT observations of 6 Abellclusters at 120 and 180 mm.Detection of emission (~2.8 Jy) from COMA.

  • Montier & Giard (2005); Giard et al. (2008). Statisticaldetection of theemission in the IR of a largesample of clusters.

  • Kitayama et al. (2009): SPITZER/MIP observations of COMA no detection (upperlimit of 7x10-2MJy/sr at 160 mm)

Detection of dust in some clusters, but still too much uncertainty to extract firm statistical conclusions.

The dust content of galaxy clusters

Our work (Gutiérrez & López-Corredoira in prep.)

Goal: To detect (or constrain) the amount of dust in the intracluster media, and its possible dependence with richness and/or redshift.


  • Large catalogue of clusters of galaxies:

  • Wen et al. (2012). SDSS based 132,684 clusters in the

  • range 0.05 < z<0.84.

  • Backgroundgalaxies:

  • SDSS/DR9 catalog of galaxieswithreliablephotometry

  • and redshifts (~3x107objects)

  • Extinctionmaps:

  • Schlegel et al. (1998) basedon IRAS and COBE data.

The dust content of galaxy clusters

Method 1: Reddening of background galaxies


Most of the redshifts for galaxies and clusters are photometric, and then have a relatively large uncertainty So, in most of the cases we do not know for sure wether a galaxy projected near a cluster is in the foreground or in the background of such cluster.

We do not map the entire cluster, but only the position where each background galaxy is projected.


The possible reddening comes from the intracluster media

(i.e. NOT from the cluster galaxies)

The dust content of galaxy clusters

Method 1: Comparison of properties of objects behind clusters with those in the field.

The dust content of galaxy clusters

Color maps of galaxies in the background of clusters as a function of clustercentric distance

Radius=6 Mpc




No evidence of dependence with clustercentric distance at the level ~0.01 mag

The dust content of galaxy clusters

Method 2

Stacking method (see Montier & Giard 2005).

1. Select those clusters above a given galactic latitude (in order to avoid regions with very heavy extinction from our own galaxy).

2. Build an extinction map (size 15 x15 Mpc2) centered on each cluster.

3. Average all those maps

Advantages and disadvantages

Each cluster is entirely mapped, but in the case of detection we do not know if that comes from galaxies of the cluster or from the intracluster media.

The dust content of galaxy clusters

Extinction maps (Schlegel et al. 1998) and catalog of galaxy clusters (Wen et al. 2012)

Uncovered by SDSS

North hemisphere

South hemisphere

At |b|>50 degrees, there are 63,598 clusters

The dust content of galaxy clusters

Section of extinctionmaps and clusters

The dust content of galaxy clusters

Maps of dust



FWHM~3.6 Mpc

Extension~18 Mpc


30 Mpc

The dust content of galaxy clusters

Maps of dust

Av~0.001 mag in the central pixel (0.6 Mpc x 0.6 Mpc)

Fromthemap of mean clusterextinction and assumingfordustgrains similar propertiestothose of theintergalactic media, we can obtainthemass and thesurfacedistribution of dust in clusters

External ring (12-15 Mpc)

to subtract the mean Galactic extinction

Region (radius~10 Mpc)to estimate the mean cluster extinction

The dust content of galaxy clusters

Dust surface density

Mean mass of dust

Mdust/Mʘ ~ 5 x 108

The dust content of galaxy clusters

Maps of dust for clusters of different redshifts and richness

Statistical clear detection of extinction in the 3x3 bins



Dust increases with richness (4s)

The dust content of galaxy clusters

The amount of dust correlates with richness of the cluster

Important remark

We have not separated yet the contribution from member galaxies from those coming from the intracluster media.

In otherwords, wehavedetectedclearlythepresence of dust in clusters, butwe do notknowyetwhichpart comes fromtheirmembers and whichfromtheintracluster media.

The dust content of galaxy clusters


  • Analysis of themost complete catalog of clusters of galaxies.

  • Twomethodstoestimatethedust in clusters:

  • -method 1: upperlimit at Av~0.01 mags

  • -method 2: cleardetection of extinctionAv=10-3 mags in the center of the

  • cluster.

  • -bothresults are compatible.

  • Theextinctiondetectedcorrespondsto a mean mass per cluster Mdust~5 x 108Mʘ

  • Theamount of extinction, and thenmass of dust, correlateswithrichness.

  • Stillunclearwhichfraction of dustisassociatedtogalaxies and totheintracluster media respectively.

  • Analysis combined with X-ray data (gas vs. dust).

  • Comparison of radial profiles of galaxies and dust.

  • 3. Dependence with redshift and of richness.

Future work

  • Separation of the contribution from galaxies and from intracluster media.

  • Use of Planck/Herschel maps for IR emission.