New High-Resolution Sunyaev-Zel'dovich Observations with GBT+MUSTANG

0.21 MB·English

by  Tony Mroczkowski

Mem.S.A.It.Vol.,1
(cid:13)c SAIt 2008 Memoriedella
New High-Resolution Sunyaev-Zel’dovich
Observations with GBT+MUSTANG
T. Mroczkowski1,2,M. J. Devlin1,S. R. Dicker1,P. M. Korngut1,B. S. Mason3,E.
1
1 D. Reese1,C. Sarazin4,J. Sievers5,M. Sun4,andA. Young1
0
2
1 UniversityofPennsylvania,209S.33rdSt.,Philadelphia,PA19104.
n
e-mail:[email protected]
a
J 2 NASAEinsteinPostdoctoralFellow.
3 NationalRadioAstronomyObservatory,520EdgemontRd.,CharlottesvilleVA22903.
5
4 DepartmentofAstronomy,UniversityofVirginia,P.O.Box400325,Charlottesville,VA
2
22901.

5 The Canadian Institute of Theoretical Astrophysics, 60 St. George Street, Toronto,
]
O OntarioM5S3H8.
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Presented15November2010/Submitted23January2011
.
h
p Abstract.Wepresentrecenthighangularresolution(9′′)Sunyaev-Zel’dovicheffect(SZE)
- observationswithMUSTANG,a90-GHzbolometricreceiverontheGreenBankTelescope.
o
MUSTANGhasnow imaged several massiveclustersof galaxiesinsomeof thehighest-
r
t resolution SZE imaging to date, revealing complex pressure substructure within the hot
s intra-cluster gas in merging clusters. We focus on three merging, intermediate redshift
a
clusters here: MACS J0744.8+3927, MACS J0717.5+3745, RX J1347.5-1145. In one of
[
these merging clusters, MACS J0744.8+3927, the MUSTANG observation has revealed

1 shocked gas that was previously undetected in X-ray observations. Our preliminary re-
v sultsforMACSJ0717.5+3745demonstratethecomplementaritytheseobservationsprovide
5 whencombinedwithX-rayobservationsofthethermalemissionandradioobservationsof
0 the non-thermal emission. And finally, by revisiting RX J1347.5-1145, we note an inter-
9 estingcorrelationbetweenitsradioemissionandtheSZEdata.Whileobservationsofthe
4 thermalSZEprobethelineofsightintegralofthermalelectronpressurethroughacluster,
. theseredshiftindependentobservationsholdgreatpotentialforaidingtheinterpretationof
1
non-thermalastrophysicsinhigh-zclusters.
0
1
1
: 1. Introduction 1991;Carlstrometal.1996).SZEsurveyslike
v
thosewiththeAtacamaCosmologyTelescope
i
X The Sunyaev-Zel’dovich effect (SZE), due to (Kosowsky 2003), the South Pole Telescope
r inverse Compton scattering of photons from (Ruhletal. 2004), and Planck (Rossetetal.
a
the Cosmic Microwave Background (CMB) 2010) are now discoveringnew clusters. With
off electrons in the intra-cluster medium notable exceptions(e.g. Komatsuetal. 2001),
(ICM)(Zel’dovich&Sunyaev1969),haslong these and other SZE instruments have reso-
been sought as a probe of cluster as- lutions ∼1–7′, and therefore do not typically
trophysics and cosmology (e.g. Birkinshaw probeclustersonscales.1Mpc.
2 T.Mroczkowski:NewMUSTANGHigh-resolutionSunyaev-Zel’dovichObservations
Recently, the MUltiplexed SQUID/TES
ArrayatNinetyGHz(MUSTANG),areceiver
on the 100-m Green Bank Telescope (GBT),
has observed the SZE from clusters at 9′′
resolution (Masonetal. 2010; Korngutetal.
2010).Atthisresolution,thethermalSZEpro-
videsaprobeofsubclusterscales,complemen-
tary to X-ray studies. In these proceedings,
wediscusstheseMUSTANGobservationsand
share the preliminary results from a new ob-
servationtakeninthe2010Ctrimester.Wedis-
cuss the instrument in § 2, present recent re-
sults in § 3, and discuss future directions for
MUSTANGin§4.
Fig.1.MACSJ0744.8+3927: ChandraX-rayim-
2. GBT+MUSTANG
agewithMUSTANGSZE4and5-σcontoursover-
MUSTANG is a cryogenic, re-imaging focal laid.X-rayanalysisguidedbythisSZEfeatureun-
plane camera with an 8 × 8 array of transi- veilsasignificant dropinX-raysurfacebrightness
and a rise in temperature, indicating shock-heated
tion edge sensor (TES) bolometers cooled to
gaswithMachnumberM=1.2±0.2.
≈ 0.3K.TheMUSTANGreceiverwasbuiltat
UPennandat90GHzisthehighestfrequency
instrumentontheGBT.Usingcapacitivemesh
filters todefinethe bandpass,MUSTANG has 0.15–1′scales,butdonotrecovertheextended
≈ 19 GHz bandwidthforcontinuumimaging. SZE flux used to determine scaling relations
The array has a 0.63fλ pixel spacing which (e.g.Bonamenteetal.2008).Theobservations
yields a well-sampled 42′′ instantaneousfield wepresenthereillustrateMUSTANG’sutility
ofviewwith∼9′′resolution.Formoredetails, inrevealingshock-heatedanddisturbedICM.
see Dickeretal. (2009) and the MUSTANG
website.1
3.1.MACSJ0744.8+3927(z= 0.69)
MACS J0744.8+3927 was discovered in the
3. Results
ROSAT All-Sky Survey (RASS) and is part
Due to common mode subtraction of the at- of the MAssive Cluster Survey (MACS
mosphere, spatial scales larger than ∼1.5– Ebelingetal. 2001, 2007), a sample of some
2× the 42′′ instantaneous field of view are of the most massive clusters at z > 0.3. As
severelyattenuatedfromMUSTANGobserva- reportedin Korngutetal. (2010), MUSTANG
tions. The resulting high-pass filtered obser- observations of this cluster revealed a feature
vations of the thermal SZE provide a mea- inthelineofsightpressure,offsetfromX-ray
sureoflineofsightintegratedpressure.2They surfacebrightnesspeak(seeFig.1).Infact,the
arewell-situatedtocomplementotherSZEin- inside edge of the SZE feature aligns with an
strumentsbymeasuringclustersubstructureon X-raysurfacebrightnessdiscontinuity.
Using the MUSTANG observations as a
1 http://www.gb.nrao.edu/mustang/
guide,Korngutetal.(2010)analysedtheavail-
2 Other manifestations of the SZE include: the
able90ksecofChandradata.Weinterpretthe
kinematic SZE, proportional to the line of sight
X-raysurfacebrightnesspeakastheintactcore
propermotionoftheICM,thepolarizedSZE,pro-
of the main cluster, and the MUSTANG se-
portional to the transverse motion of the ICM,
andthenon-thermal SZE,proportionaltorelativis- lected featureas shock-heatedgas.Thegasto
tic electrons in the ICM. See e.g. Carlstrometal. the westofboththe MUSTANG selectedfea-
(2002). ture and the second X-ray surface brightness
T.Mroczkowski:NewMUSTANGHigh-resolutionSunyaev-Zel’dovichObservations 3
Fig.2. MACS J0717.5+3745 preliminary data:
Fig.3. RX J1347.5-1145: MUSTANG S/N map
Maetal.(2009)temperaturemapwithMUSTANG
withVLA1.4GHzcontoursfromGittietal.(2007)
S/N (black)andGMRT600MHz(white)contours
overlaid. The SZEdecrement at >3-σcorresponds
from vanWeerenetal. (2009) overlaid. The peak
totheradioemissionatfoundat>9-σ.Bothareen-
SZEdetectioniscospatialwiththehottest(∼24keV,
hancedtothesoutheast, outsidethecoolcore.The
inwhite) regionidentifiedinthetemperaturemap,
centralpointsourceintheMUSTANGmapwasde-
andisborderedbytheradiorelictothenorth.
tectedat∼40-σ,andisfullysaturatedinthismap.
3.3.RXJ1347.5-1145(z= 0.45)
discontinuity is likely the pre-shock medium.
We derivea bestfitMachnumberM = 1.2± RXJ1347.5-1145,anothermemberofMACS,
0.2 (Korngutetal. 2010), implying this is a is the most X-ray luminous cluster known.
fairly weak shock, marginally consistent with While its X-ray emission is dominated by
beingtransonic. its relaxed cool core, there is substantial ev-
idence pointing to a high impact parameter
merger. High resolution SZE measurements
3.2.MACSJ0717.5+3745(z= 0.55)
with Nobeyama (Komatsuetal. 2001) indi-
MACS J0717.5+3745, also found in MACS, cated(at∼3-σ)thepresenceofa pressureen-
exhibits many signposts of on-going merger hancement to the southeast. The Nobeyama
activity.Opticalobservationsshowthiscluster result was soon confirmed by X-ray observa-
to have the largest known Einstein radius and tions(Allenetal.2002).MUSTANGlaterim-
a complicated mass distribution (Zitrinetal. proved upon the significance of the SZE re-
2010). Radio observations with the VLA and sult to many sigma in its first cluster obser-
GMRT have revealed what is likely a relic vation (Masonetal. 2010). Interestingly, ra-
(Bonafedeetal.2009;vanWeerenetal.2009) dioemissionfromRXJ1347.5-1145,predomi-
due to electrons re-accelerated to relativistic nantlyduetothemini-haloassociatedwiththe
energiesbyashock.X-rayobservationsreveal relaxed cool core, shows a similar southeast
a complexICM morphologyandregionswith enhancement (Gittietal. 2007). In Fig. 3, we
temperatures as high as ∼ 24 keV (Maetal. showthattheSZEdecrementisco-spatialwith
2009), indicatinga sharp pressure discontinu- theradioemission.
ity to the southof the radio relic.The prelim-
inaryMUSTANGdatahelpcompletethispic-
4. Conclusions&FutureWork
ture:the peakin the MUSTANG maps agrees
wellwiththepositionofthehotgasseeninthe MUSTANG has been pioneering in the
X-ray(seeFig.2). study of cluster astrophysics and substruc-
4 T.Mroczkowski:NewMUSTANGHigh-resolutionSunyaev-Zel’dovichObservations
ture through the SZE. The clusters targeted Dicker, S. R., Mason, B. S., Korngut, P. M.,
in MUSTANG observations to date, however, etal.2009,ApJ,705,226
havebeenchoseninanadhocfashion.Toad- Ebeling, H., Barrett, E., Donovan, D., et al.
dress this, we are moving to image a cluster 2007,ApJ,661,L33
sample down to a uniform depth, confirming Ebeling,H.,Edge,A.C.,&Henry,J.P.2001,
or rejecting the presence of cluster substruc- ApJ,553,668
turethatwouldaffectSZE scalingrelationsat Gitti, M., Ferrari, C., Domainko, W., Feretti,
thelevelofafewpercent. L.,&Schindler,S.2007,A&A,470,L25
We are also working to improveour anal- Komatsu, E., Matsuo, H., Kitayama, T., et al.
ysis tools. Notably, we will soon be able to 2001,PASJ,53,57
remove point source contaminationfrom, and Korngut, P. M., Dicker, S. R., Reese, E. D.,
fit cluster models to, the time ordered data. etal.2010,ArXive-prints
This will provide a method by which to fit Kosowsky,A.2003,NewAstronomyReview,
MUSTANG data jointly with X-ray data and 47,939
thatfromotherSZEinstruments. Ma, C., Ebeling,H., & Barrett, E. 2009,ApJ,
693,L56
Most tantalizing of all, we have pro-
Mason, B. S., Dicker, S. R., Korngut, P. M.,
posed a successor instrument to MUSTANG,
etal.2010,ApJ,716,739
MUSTANG2, which is designed to have a
larger instantaneous field of view (4.5′) and Rosset, C., Tristram, M., Ponthieu, N., et al.
& 30× higher sensitivity than MUSTANG. 2010,A&A,520,A13+
Ruhl, J., Ade, P. A. R., Carlstrom, J. E., et al.
Observations that currently take hours with
2004,5498,11
MUSTANG could be performed in a matter
of minutes, imaging the SZE at ∼ 9′′ reso- van Weeren, R. J., Ro¨ttgering, H. J. A.,
lution and recovering SZE flux out to ∼ 9′ Bru¨ggen,M.,&Cohen,A.2009,A&A,505,
991
scales. This upgrade is crucial as the GBT
Zel’dovich, Y. B. & Sunyaev, R. A. 1969,
isheavilysubscribed,andMUSTANG’shigh-
Ap&SS,4,301
frequency observations demand the best ob-
Zitrin, A., Broadhurst, T., Barkana, R.,
servingconditionsGreenBank,WestVirginia,
Rephaeli,Y., & Benitez, N. 2010,ArXive-
has to offer. This upgrade will also ensure
prints
GBT+MUSTANG2willremaincompetitiveas
ALMA comes online, as MUSTANG2 will
provide an order magnitude better mapping
Acknowledgements. We thank M. Gitti, C. Ma,
speedforcontinuumemissionat90GHzthan
and R. J. van Weeren for sharing data used for
the50-elementALMA.
comparisonwiththeMUSTANGobservationspre-
sented.Weappreciatethelatenightassistancefrom
the GBT operators, namely Greg Monk, Donna
Stricklin, Barry Sharp and Dave Rose. Support
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