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arXiv:1105.4572v2 [astro-ph.CO] 16 Jun 2011 Accepted for publication in ApJ Preprint typeset using L A T E X style emulateapj v. 03/07/07 A VERY DEEP CHANDRA OBSERVATION OF ABELL 2052: BUBBLES, SHOCKS, AND SLOSHING E. L. Blanton 1,2 , S. W. Randall 2 , T. E. Clarke 3 C. L. Sarazin 4 , B. R. McNamara 5,2,6 , E. M. Douglass 1 , and M. McDonald 7 Accepted for publication in ApJ ABSTRACT We present first results from a very deep (650 ksec) Chandra X-ray observation of Abell 2052, as well as archival VLA radio observations. The data reveal detailed structure in the inner parts of the cluster, including bubbles evacuated by the AGN’s radio lobes, compressed bubble rims, filaments, and loops. Two concentric shocks are seen, and a temperature rise is measured for the innermost one. On larger scales, we report the first detection of an excess surface brightness spiral feature. The spiral has cooler temperatures, lower entropies, and higher abundances than its surroundings, and is likely the result of sloshing gas initiated by a previous cluster-cluster or sub-cluster merger. Initial evidence for previously unseen bubbles at larger radii related to earlier outbursts from the AGN is presented. Subject headings: galaxies: clusters: general — cooling flows — intergalactic medium — radio contin- uum: galaxies — X-rays: galaxies: clusters — galaxies: clusters: individual(A2052) 1. INTRODUCTION With its sub-arcsec resolution, the Chandra X-ray Ob- servatory has revealed a wealth of substructure in the X-ray-emitting intracluster medium (ICM) in clusters of galaxies. “Cavities” or “bubbles” are commonly seen in the X-ray gas in cluster centers related to outbursts by the active galactic nucleus (AGN). In addition, surface brightness edges associated with shocks and cold fronts have been observed, as well as spiral features likely re- lated to “sloshing” of the intracluster medium in cluster centers. The central bubbles are frequently seen in cooling flow (or “cool core”) clusters and are often filled with radio emission associated with the AGN. There was some ev- idence for these features in a very few cases even be- fore Chandra observations (e.g. ROSAT observations of Perseus [B¨ ohringer et al. 1993], Abell 4059 [Huang & Sarazin 1998], and Abell 2052 [Rizza et al. 2000]). Clus- ters with cool cores have radio bubbles much more of- ten than non-cool core clusters (e.g. Mittal et al. 2009), and some of the most spectacular individual cases ob- served by Chandra are the Perseus cluster (Fabian et al. 2003, 2006), M87/Virgo (Forman et al. 2005, 2007), Hydra A (McNamara et al. 2000, Wise et al. 2007), MS0735.6+7421 (McNamara et al. 2005), and Abell 2052 (Blanton et al. 2001, 2003, 2009, 2010). The classic “cooling flow problem” is that sufficient 1 Institute for Astrophysical Research and Astronomy Depart- ment, Boston University, 725 Commonwealth Avenue, Boston, MA 02215; [email protected], [email protected] 2 Harvard Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138; [email protected]; ELB as Visiting Scientist 3 Naval Research Laboratory, 4555 Overlook Avenue SW, Wash- ington D. C. 20375; [email protected] 4 Department of Astronomy, University of Virginia, P. O. Box 400325, Charlottesville, VA 22904-4325; [email protected] 5 Department of Physics and Astronomy, University of Waterloo, Waterloo, ON N2L 2G1, Canada; [email protected] 6 Perimeter Institute for Theoretical Physics, 31 Caroline St., N. Waterloo, Ontario, Canada, N2L 2Y5 7 Astronomy Department, University of Maryland, College Park, MD 20742; [email protected] quantities of cool gas (as evidenced by star formation rates, for example) were not found to match the gas cool- ing rates estimated from earlier X-ray observatories. The X-ray cooling rates have lowered based on Chandra and XMM-Newton observations, and the majority of the gas is seen to cool to only some fraction (typically one-third to one-half) of the cluster average temperature (Peterson et al. 2003). A heating mechanism is required to stop the gas from cooling to even lower temperatures. The most likely candidate for heating of the central cluster gas is feedback from central AGN that are fed by the cooling gas (see McNamara & Nulsen 2007 for a review). This heating comes in the form of bubbles in- flated by the AGN, described above, that then rise buoy- antly to larger radii in cluster atmospheres distributing the heat. The details of this heating, however, are still not completely understood. In addition, there is at least some component of shock heating in many cluster cen- ters, especially early on in the AGN’s lifetime. Shocks have been detected in fewer cases than radio bubbles, and observations include those of Perseus (Fabian et al. 2003, 2006; Graham et al. 2008), M87/Virgo (Forman et al. 2005), Hydra A (Nulsen et al. 2005a), Hercules A (Nulsen et al. 2005b), MS0735.6+7421 (McNamara et al. 2005), and the group NGC 5813 (Randall et al. 2011). Typically, the shocks are weak with Mach numbers rang- ing from approximately 1.2 to 1.7 (McNamara & Nulsen 2007). In even fewer cases are temperature rises detected associated with the shocks. Heating of the ICM may also result from gas “slosh- ing” in the cluster’s central potential well (Ascasibar & Markevitch 2006; ZuHone et al. 2010). Cold fronts, re- gions where the surface brightness changes sharply but the pressure does not, can result from these sloshing mo- tions driven initially by cluster or sub-cluster mergers. The sloshing can produce a spiral distribution of cool cluster gas reaching into the cluster center (e.g. Clarke et al. 2004, Lagan´aet al. 2010), and is alsoseen in galaxy groups (Randall et al. 2009a). Here, we present a very deep Chandra observation of the cool core cluster Abell 2052. The only other cool core

Abell 2052

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11Accepted for publication in ApJPreprint typeset using LATEX style emulateapj v. 03/07/07

A VERY DEEP CHANDRA OBSERVATION OF ABELL 2052: BUBBLES, SHOCKS, AND SLOSHING

E. L. Blanton1,2, S. W. Randall2, T. E. Clarke3 C. L. Sarazin4, B. R. McNamara5,2,6, E. M. Douglass1, and M.McDonald7

Accepted for publication in ApJ

ABSTRACT

We present first results from a very deep (∼ 650 ksec) Chandra X-ray observation of Abell 2052, aswell as archival VLA radio observations. The data reveal detailed structure in the inner parts of thecluster, including bubbles evacuated by the AGN’s radio lobes, compressed bubble rims, filaments,and loops. Two concentric shocks are seen, and a temperature rise is measured for the innermost one.On larger scales, we report the first detection of an excess surface brightness spiral feature. The spiralhas cooler temperatures, lower entropies, and higher abundances than its surroundings, and is likelythe result of sloshing gas initiated by a previous cluster-cluster or sub-cluster merger. Initial evidencefor previously unseen bubbles at larger radii related to earlier outbursts from the AGN is presented.

Subject headings: galaxies: clusters: general — cooling flows — intergalactic medium — radio contin-uum: galaxies — X-rays: galaxies: clusters — galaxies: clusters: individual(A2052)

1. INTRODUCTION

With its sub-arcsec resolution, the Chandra X-ray Ob-servatory has revealed a wealth of substructure in theX-ray-emitting intracluster medium (ICM) in clusters ofgalaxies. “Cavities” or “bubbles” are commonly seen inthe X-ray gas in cluster centers related to outbursts bythe active galactic nucleus (AGN). In addition, surfacebrightness edges associated with shocks and cold frontshave been observed, as well as spiral features likely re-lated to “sloshing” of the intracluster medium in clustercenters.The central bubbles are frequently seen in cooling flow

(or “cool core”) clusters and are often filled with radioemission associated with the AGN. There was some ev-idence for these features in a very few cases even be-fore Chandra observations (e.g. ROSAT observations ofPerseus [Bohringer et al. 1993], Abell 4059 [Huang &Sarazin 1998], and Abell 2052 [Rizza et al. 2000]). Clus-ters with cool cores have radio bubbles much more of-ten than non-cool core clusters (e.g. Mittal et al. 2009),and some of the most spectacular individual cases ob-served by Chandra are the Perseus cluster (Fabian etal. 2003, 2006), M87/Virgo (Forman et al. 2005, 2007),Hydra A (McNamara et al. 2000, Wise et al. 2007),MS0735.6+7421 (McNamara et al. 2005), and Abell 2052(Blanton et al. 2001, 2003, 2009, 2010).The classic “cooling flow problem” is that sufficient

1 Institute for Astrophysical Research and Astronomy Depart-ment, Boston University, 725 Commonwealth Avenue, Boston, MA02215; [email protected], [email protected]

2 Harvard Smithsonian Center for Astrophysics, 60 GardenStreet, Cambridge, MA 02138; [email protected];ELB as Visiting Scientist

3 Naval Research Laboratory, 4555 Overlook Avenue SW, Wash-ington D. C. 20375; [email protected]

4 Department of Astronomy, University of Virginia, P. O. Box400325, Charlottesville, VA 22904-4325; [email protected]

5 Department of Physics and Astronomy, University of Waterloo,Waterloo, ON N2L 2G1, Canada; [email protected]

6 Perimeter Institute for Theoretical Physics, 31 Caroline St., N.Waterloo, Ontario, Canada, N2L 2Y5

7 Astronomy Department, University of Maryland, College Park,MD 20742; [email protected]

quantities of cool gas (as evidenced by star formationrates, for example) were not found to match the gas cool-ing rates estimated from earlier X-ray observatories. TheX-ray cooling rates have lowered based on Chandra andXMM-Newton observations, and the majority of the gasis seen to cool to only some fraction (typically one-thirdto one-half) of the cluster average temperature (Petersonet al. 2003). A heating mechanism is required to stop thegas from cooling to even lower temperatures.The most likely candidate for heating of the central

cluster gas is feedback from central AGN that are fedby the cooling gas (see McNamara & Nulsen 2007 for areview). This heating comes in the form of bubbles in-flated by the AGN, described above, that then rise buoy-antly to larger radii in cluster atmospheres distributingthe heat. The details of this heating, however, are stillnot completely understood. In addition, there is at leastsome component of shock heating in many cluster cen-ters, especially early on in the AGN’s lifetime. Shockshave been detected in fewer cases than radio bubbles,and observations include those of Perseus (Fabian et al.2003, 2006; Graham et al. 2008), M87/Virgo (Formanet al. 2005), Hydra A (Nulsen et al. 2005a), Hercules A(Nulsen et al. 2005b), MS0735.6+7421 (McNamara et al.2005), and the group NGC 5813 (Randall et al. 2011).Typically, the shocks are weak with Mach numbers rang-ing from approximately 1.2 to 1.7 (McNamara & Nulsen2007). In even fewer cases are temperature rises detectedassociated with the shocks.Heating of the ICM may also result from gas “slosh-

ing” in the cluster’s central potential well (Ascasibar &Markevitch 2006; ZuHone et al. 2010). Cold fronts, re-gions where the surface brightness changes sharply butthe pressure does not, can result from these sloshing mo-tions driven initially by cluster or sub-cluster mergers.The sloshing can produce a spiral distribution of coolcluster gas reaching into the cluster center (e.g. Clarkeet al. 2004, Lagana et al. 2010), and is also seen in galaxygroups (Randall et al. 2009a).Here, we present a very deep Chandra observation of

the cool core cluster Abell 2052. The only other cool core

Page 2: Abell 2052

2 Blanton et al.

clusters observed to similar or greater depth with Chan-dra are Perseus (Fabian et al. 2006) and M87/Virgo (Mil-lion et al. 2010, Werner et al. 2010). Abell 2052 is a mod-erately rich cluster at a redshift of z = 0.03549 (Oegerle& Hill 2001). Its central radio source, 3C 317, is hostedby the central cD galaxy, UGC 09799. Abell 2052 waspreviously observed in the X-ray with Einstein (White,Jones, & Forman 1997), ROSAT (Peres et al. 1998, Rizzaet al. 2000), ASCA (White 2000), Chandra (Blanton etal. 2001, 2003, 2009, 2010), Suzaku (Tamura et al. 2008),and XMM-Newton (de Plaa et al. 2010). In addition, wepresent archival radio observations from the Very LargeArray (VLA).We assume H = 70 km s−1 Mpc−1, ΩM = 0.3, and

ΩΛ = 0.7 (1′′ = 0.7059 kpc at z = 0.03549) throughout.Errors are given at the 1σ level unless otherwise stated.

2. CHANDRA OBSERVATIONS AND DATA REDUCTION

Abell 2052 was observed with Chandra for a total of662 ksec in Cycles 1, 6, and 10 from 2000 – 2009. A sum-mary of the observations is given in Table 1. All obser-vations were performed with the ACIS-S as the primaryinstrument. The ACIS-S was chosen for its greater re-sponse at low energies than the ACIS-I, yielding a highercount rate for this relatively cool, kT ≈ 3 keV cluster.The nominal roll angles used for the observations variedfrom 99 to 265 providing coverage at large radii at arange of azimuthal angles around the cluster. The eventswere telemetered in Very Faint mode for all but the Cy-cle 1 observation, where the events were telemetered inFaint mode. The data were processed in the standardmanner, using CIAO 4.2 and CALDB 4.2.2. After clean-ing, and filtering for background flares (using the 2.5 –7.0 keV range for the BI chips and the 0.3 – 12.0 keVrange for the FI chips), the total exposure remaining forthe eleven data sets was 657 ksec. Background correc-tions were made using the blank-sky background fields,including the new “period E” background files for themore recent data. For each target events file, a corre-sponding background events file was created, normaliz-ing by the ratio of counts in the 10 – 12 keV energy rangefor the source and background files to set the scaling.

3. RADIO DATA

We have used the NRAO data achive to extract ob-servations of 3C 317 at 4.8 and 1.4 GHz. A summaryof the data sets is presented in Table 2. The archivalradio data were calibrated and reduced with the NRAOAstronomical Image Processing System (AIPS). Imageswere produced through the standard Fourier transformdeconvolution method for each frequency and configura-tion. Several loops of imaging and self-calibration wereundertaken for each data set to reduce the effects of phaseand amplitude errors in the data. The final radio imageat 4.8 GHz was obtained through combining the threeVLA configurations and two observing frequencies. Wehave also produced a combined configuration image at1.4 GHz but do not show it as the structure is remark-ably similar to the 4.8 GHz image.We have made a spectral index map between 1.4 GHz

and 4.8 GHz to compare the spectral features more di-rectly with the X-ray structure. This map was createdfrom the combined configuration data at each frequency.The uv-coverage of both data sets was matched and both

frequencies were imaged with a 4.3′′ circular beam. Wehave blanked all pixels in the spectral index map thatwere lower than the 5σ level on either of the input maps.

4. IMAGES

Merged X-ray images of the source were created. Theimages were corrected using merged background imagesand exposure maps. An image showing the combineddata from all CCD chips used in the analysis (ACIS S1,S2, S3, I2, and I3) in the 0.3−10.0 keV band is shown inFig. 1. This figure illustrates the different roll angles thatwere used when the observations were performed. Theextended cluster emission is visible, as well as numerouspoint sources which appear more extended while increas-ingly off-axis due to the larger PSF in these regions. Theimage has been smoothed with a 3′′ Gaussian.An unsmoothed image in the 0.3−2.0 keV band of the

central region of the cluster is shown in Fig. 2. The imagereveals exquisite detail related to the interaction of theAGN with the ICM. Point sources, including the centralAGN, are visible. Cavities or bubbles to the N and S ofthe AGN are seen, as well as outer cavities to the NWand SE. The inner cavities are bounded by bright, dense,rims, and the NW cavity is surrounded by a very narrow,filamentary loop. A filament extends into the N bubble.A shock is seen exterior to the bubbles and rims, and aprobable second shock is visible to the NE.A three-color image of the central 6.′56×6.′56 region of

A2052 is displayed in Fig. 3. The image has been slightlysmoothed, using a 1.′′5 Gaussian, and the scaling for eachof the three colors is logarithmic. Red represents the soft(0.3 − 1.0 keV) band, green is medium (1.0 − 3.0 keV),and blue represents the hard band (3.0− 10.0 keV). Thebright rims surrounding the inner bubbles appear cool.The first shock exterior to the bubble rims is slightlyelliptical with the major axis in the north-south direction(Blanton et al. 2009). It is visible as a discontinuity inthe surface brightness, and the bluish color is consistentwith a temperature rise in this region. Outside of theinner shock, a second surface brightness discontinuity isseen as greenish emission in this figure. The discontinuityis sharper to the NE and more extended to the SW. Thisfeature may represent a shock or a cold front. Thesefeatures will be explored in further detail in §6.A composite X-ray/optical/radio image is shown in

Fig. 4. The 0.3−2.0 keV Chandra image is shown in red,radio emission at 4.8 GHz from the VLA is displayed asblue, and optical r-band emission from the Sloan Digi-tal Sky Survey (SDSS; Abazajian et al. 2009) is shownas green. The AGN is visible in the X-ray, radio, andoptical, and the radio lobes fill the cavities in the X-rayemission. This includes the inner cavities as well as anouter cavity bounded by a narrow loop to the NW andthe outer cavity to the S/SE. In addition, the radio emis-sion is breaking through the northern bubble rim to thenorth. The X-ray filament extending from the northernbubble rim towards the AGN was found to be associatedwith Hα emission in Blanton et al. (2001). In Fig. 5,we show SDSS r-band contours superposed on a Chan-dra image in the 0.3 − 10.0 keV range that has beensmoothed with a 1.′′5 radius Gaussian. The central cDgalaxy is oriented in the NE-SW direction in the optical.The inner bubbles seen in the X-ray emission are withinthe cD galaxy.

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Very Deep Chandra Observation of A2052 3

4.1. Residual Images

In order to better reveal features in the X-ray image,we created residual images using two different techniques.In the first, we used the method of unsharp-masking, andin the second, we subtracted a 2D beta model from theX-ray image. We find that unsharp-masking is usefulfor highlighting the structure in the inner parts of thecluster, while the model subtraction is better at revealinglarger-scale features.

4.1.1. Unsharp-masking

We created an unsharp-masked image in the 0.3− 10.0keV energy range. Sources were detected in the imageusing the wavelet detection tool “wavdetect” in CIAO(Freeman et al. 2002). Several wavelet scales were used,at 1, 2, 4, 8, and 16 pixels, where 1 pixel = 0.′′492.Sources detected using this method were visually exam-ined and several were rejected as being clumpy X-ray gasemission rather than point sources. A source-free imagewas created by replacing the source pixel values withthe average value found in an annulus surrounding eachsource. We retained the sources in our unsharp-maskedimage while making corrections with a source-free image.Smoothed images, both with and without sources, werecreated by smoothing with a 0.′′98 radius Gaussian. An-other copy of the source-free image was smoothed witha 9.′′8 Gaussian. A summed image was made by combin-ing the source-free images smoothed at the two differentscales. A difference image was made by subtracting the9.′′8 Gaussian-smoothed source-free image from the 0.′′98Gaussian-smoothed image that contained sources. Fi-nally, the unsharp-masked image was created by divid-ing the difference image by the summed image. In thisway, we retain the sources in the image, smoothed at ascale of 0.′′98. This method is similar to that in Fabianet al. (2006), although sources are excluded throughoutin their unsharp-masked images.The unsharp-masked image is displayed in Figure 6

with VLA 4.8 GHz radio contours superposed. The bub-bles in the X-ray emission are more easily seen in thisimage, as are the bright bubble rims, the shock exteriorto the bubble rims, and the second shock or cold frontfeature to the NE. The radio emission fills the inner bub-bles and the southern lobe turns to fill the outer southernbubble. The radio lobe to the north appears to be es-caping through a gap in the northern bubble rim, and anarrow filament is seen in the radio in this region. Theradio emission also extends beyond the bubble rims tothe NW to fill a small bubble bounded by a narrow X-ray filament. To the east, an extension in the radio fillsa small depression in the X-ray on the scale of approxi-mately 10′′.

4.1.2. Beta-model subtraction

A 2D beta model was used to fit the surface brightnessin both 0.3− 2.0 keV and 0.3− 10.0 keV images using acircular region with radius 5.′66. The images were source-free, with the surface brightness at the position of sourcesapproximated from the surface brightness in an annulusaround each source, as above. Corrections were made forexposure, using a merged exposure map. Similar resultswere obtained for the fits to the images in both energybands. Errors were computed using Cash statistics. For

the 0.3−2.0 keV image, the center of the large scale emis-sion was found to be only 1.′′2 away from the position ofthe AGN. The emission was found to be slightly ellip-tical, with an ellipticity value of 0.18 ± 0.00081 (whereellipticity values range from 0 to 1, with 0 indicating cir-cular emission). The position angle for the semi-majoraxis of the ellipse is 38.2± 0.1 measured north towardseast. The core radius using this model is 25.1 ± 0.060′′

and the beta index is β = 0.46± 0.00021.The residual image after 2D beta model subtraction in

the 0.3 − 2.0 keV band in shown in Fig. 7. The imagehas been smoothed with a 7.′′38 radius Gaussian. Thesmoothing washes out the details in the very center of theimage, but the bright bubble rims are clearly visible. Aspiral feature is seen, starting in the SW and extending tothe NE. Similar spiral structures have been seen in otherclusters, with A2029 being a particularly clear example(Clarke et al. 2004).

5. X-RAY SPECTRAL MAPS

Spectral maps were created to examine the distribu-tion of temperature, as well as entropy, pressure, andabundance using the technique described in Randall etal. (2008, 2009b). The temperature maps were created byextracting spectra for the separate Chandra observationsand fitting them simultaneously in the 0.6−7.0 keV rangewith a single temperature APEC model, with NH set tothe Galactic value of 2.71× 1020 cm−2 (Dickey & Lock-man 1990) and the abundance allowed to vary. Back-ground spectra were extracted from the blank sky back-ground observations that were reprojected to match eachdata set. Data from both the frontside- and backside-illuminated (FI and BI) chips were used, with separateresponse files and normalizations determined for eachObsID’s data set, with the FI and BI normalizationsallowed to vary independently for each ObsID. Spectrawere extracted with a minimum of either 2000 or 10000background-subtracted counts, corresponding to a mini-mum SNR of approximately 45 or 100, respectively, de-pending on our analysis goals. The radius of the circu-lar extraction region was allowed to grow to the size re-quired to extract the minimum counts. Spectral maps ofthe central region of A2052 were previously presented inBlanton et al. (2003, 2009). Here, with the much deeperChandra data, we are able to examine a much larger re-gion of the cluster with high precision. We have chosen toinclude spectral maps created as described above ratherthan Voronoi-Tesselation maps, even though some of themap pixels are not independent (some regions used inspectral fitting overlap), especially in the outer regionsof the maps. We find that spectral structures are easierto see on the maps we present, and they are confirmedby extracting spectral profiles in §6 and §7.In Fig. 8, we display a high-resolution (0.′′492 pixels)

temperature map of the central region of A2052, wherethe minimum number of net counts was 2000. Super-posed on the temperature map are X-ray surface bright-ness contours derived from the 1.′′5 Gaussian-smoothed0.3−10.0 keV image. The coolest parts of the cluster arefound in the brightest parts of the X-ray rims surround-ing the bubbles, including the bright rim to the W andNW, the E-W bar that passes through the cluster centerand AGN, and the N filament that extends into the Nbubble. An overlay of Hα contours from McDonald et

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4 Blanton et al.

al. (2010) onto the high-resolution temperature map isshown in Fig. 9. For comparison, the Hα contours aresuperposed onto the 0.3− 10.0 keV, 1.′′5 radius Gaussiansmoothed, Chandra image in Fig. 10. The correspon-dence between the Hα emission and both the surfacebrightness and temperature structure is excellent. Hαemission, representing gas with T ≈ 104 K, is detectedin the brightest and coolest structures in the cluster cen-ter, including the E-W bar and the filament that extendsinto the N bubble. While correspondence between Hαand X-ray surface brightness was shown in Blanton et al.(2001), with the deeper Chandra and new Hα data pre-sented here, we see more detail in the association, includ-ing the filament extending into the N bubble not reachingthe AGN (whereas it appeared to reach the AGN in Hαin the Baum et al. (1988) data shown in Blanton etal. (2001)). The association between the Hα and X-rayindicates that at least some gas is cooling from the tem-perature associated with the X-ray gas in these regions(T ≈ 107 K) to T ≈ 104 K. McDonald et al. (2010) andMcDonald et al. (2011) suggested that this gas representsgas that was previously cooler and then ionized to pro-duce the Hα emission. Given the low UV-to-Hα ratioin this system, they conclude that the ionization sourcewould likely be shocks related to the AGN rather thannearby, luminous, stars, as in some other cluster centers.Additionally, significant clumpy substructure in the

temperature distribution is seen in the gas throughoutthe central cluster region. This substructure will be fur-ther investigated in an upcoming paper. Errors rangefrom approximately 2% in the very central, brightest re-gions, to approximately 12% in the outer areas of themap.In Fig. 11, we show a projected or “pseudo” pressure

map of the central region of A2052. The map was de-rived using the APEC normalization and temperaturefrom the spectral fits that resulted in the temperaturemap in Fig. 8. The APEC normalization is proportionalto n2V , where n is density and V is the volume projectedalong the line of sight. We define the projected pressureas kT (A)1/2, where A is the APEC normalization scaledby area to account for extraction regions that may go offthe edge of the chips. Superposed on the pressure mapare X-ray surface brightness contours in the 0.3 − 10.0keV band. The most obvious feature in the map is theclear ring of high pressure that is coincident with the in-ner discontinuity seen in surface brightness and the jumpin density (Blanton et al. 2009) visible in Figs. 2 and 3.The bubbles, including the inner bubbles to the N and Sof the AGN as well as the outer, small NW bubble andthe outer SE bubble, are visible as lower-pressure regionsin this projected pressure map since they are largely de-void of X-ray-emitting gas.A lower-resolution temperature map covering a larger

region of the center is shown in Fig. 12. Here, the mini-mum number of background-subtracted counts is 10000,and the pixel size is 8′′. The errors in temperature rangefrom 1% in the inner regions to 5% in the outskirts ofthe frame. Superposed are the residual surface bright-ness contours in the 0.3− 2.0 keV band after beta-modelsubtraction (see Fig. 7). The spiral excess traces out aregion of temperature lower than its surroundings. Inaddition, this low temperature feature continues inward

along the direction of the spiral toward the cluster center,beyond the extent of the inner spiral contours.A higher-resolution temperature map showing the

same f.o.v. as in Fig. 12 is displayed in Fig. 13. The spec-tra were extracted with a minimum of 2000 background-subtracted counts, and the pixel size is 4′′. The maprepresents more than 80000 spectral fits. Here, the er-rors range from 2% in the inner regions to approximately14% in the outskirts. Two views of a pseudo-pressuremap derived from the fits that were used to make thetemperature map in Fig. 13 are shown is Figs. 14 and 15.The pressure jump corresponding to the innermost shockis clearly seen, as well as evidence for pressure structuretracing the second inner shock (seen in the outer X-raycontour). There is no evidence of structure in the pres-sure map related to the spiral structure.A pseudo-entropy map is displayed in Fig. 16 with ex-

cess surface brightness contours after subtracting a betamodel superposed. The map was derived using the spec-tral fits that resulted in the temperature map in Fig.13. We define pseudo-entropy as kT (A)−1/3, with A de-fined as above. In general, the entropy decreases towardthe cluster center. There appears to be correspondencebetween structure in the entropy map and the spiral fea-ture.A projected abundance map is shown in Fig. 17, cor-

responding to the temperature map in Fig. 12 with 8′′

pixels and a minimum of 10000 background-subtractedcounts per pixel. Errors range from 5% in the highestsurface brightness regions, to 23% in the outer regions ofthe map (with the majority of the errors at the 10−15%level across the map). To the SW, a region of high abun-dance is coincident with the high surface-brightness spi-ral. This is consistent with higher metallicity gas sloshingaway from the cluster center, creating the spiral. A high-metallicity region was found at a similar position to theSW using XMM-Newton data (de Plaa et a. 2010).

6. INNER SHOCK FEATURES

In Blanton et al. (2009), we identified two inner sur-face brightness jumps that were likely associated withshocks. These jumps are visible in Figs. 3, 6, and 15.The first inner jump extends around the cluster centerin a slightly elliptical shape in the N-S direction at aradius of approximately 40′′. The second jump is ellip-tical in the NE to SW direction, and is sharper and ata smaller radius from the AGN in the NE direction. Tothe NE, the second jump is at a radius of approximately65′′.Similar to Blanton et al. (2009), we have fitted a pro-

jected spherical density model to the surface brightnessin a NE wedge with PA −2 to 98 measured east fromnorth. The projected model characterizes the density us-ing power laws and discontinuous jumps. We use threepower laws, and identify two density jumps. See Randallet al. (2008) for further description of this technique.Our results are generally consistent with, and a refine-

ment of, those presented in Blanton et al. (2009). Thedensity jumps are at radii of 44.2± 0.1 arcsec (31.2± 0.1kpc) and 66.3+0.3

−0.06 arcsec (46.8+0.02−0.04 kpc), respectively,

from the AGN. The magnitudes of the jumps are fac-tors of 1.25+0.016

−0.015 and 1.29+0.010−0.012, for the first and second

jumps, respectively. The slopes of the three power-lawcomponents, going from the inner to outer regions, are

Page 5: Abell 2052

Very Deep Chandra Observation of A2052 5

−0.53+0.029−0.024, −1.25+0.030

−0.037, and −1.06+0.0067−0.0084.

The jumps in density correspond to Mach numbers of1.17+0.011

−0.010 and 1.20+0.0072−0.0079, respectively, for the first and

second jumps. The temperature is then expected to risea similar amount inside both shocks (a factor of 1.16 forthe first shock and 1.19 for the second shock).We have calculated a deprojected temperature profile

for the NE region, shown in Fig. 18. Dashed lines indi-cate the locations of the two shocks. As with all of ourspectral fits, spectra were extracted separately for eachdata set and fitted simultaneously in XSPEC v12.6. Thefits were performed in the 0.6 − 7.0 keV range. A sin-gle APEC model plus Galactic absorption was fitted tothe outermost annulus spectra with abundance allowedto vary. The contribution of emission from this shell tothe next annulus in was calculated using geometric pro-jection, assuming spherically symmetric shells, and theAPEC normalization scaled appropriately to account forthe projection of this outer component. The parametersfor the contribution from the outer annulus were frozen,and an additional APEC model was added for the an-nulus of interest. This procedure was continued inward,where the spectral model for each annulus included con-tributions from all external annuli. See Blanton et al.(2003) for further description.In addition, in Fig. 18, we present density and pres-

sure profiles for the NE region. The density and pres-sure were determined from the deprojected spectral fits,since the normalization of the free APEC component foreach annulus is proportional to the square of density atthat annulus. Note that the radius range extends to ap-proximately 300′′ (212 kpc) where the overdensity (thedensity relative to the critical density) is ≈ 12500. Forcomparison, an overdensity of 500 (r500) is at r ≈ 800kpc (≈ 1100′′).A clear rise in temperature is seen inside the innermost

shock, in addition to the jumps in density and pressurein this region. In Blanton et al. (2009), while the tem-peratures inside and outside this shock were consistentwith the rise expected given the Mach number, the best-fitting temperatures were approximately flat across theshock. Here, with the much deeper data set, the rise isclearly detected. Just outside the shock, the temperatureis kT = 2.81+0.11

−0.15 keV, while inside the shock it reaches

kT = 3.14+0.11−0.11 keV, a factor of 1.12+0.10

−0.08 higher, with asignificance or 2.1σ. Such temperature rises associatedwith weak shocks are extremely difficult to measure incluster centers, with very deep, high resolution observa-tions required.For the second shock, the situation is less obvious. The

best-fitting temperatures are appproximately flat acrossthe shock: kT = 3.35+0.20

−0.16 keV outside the shock and

kT = 3.27+0.14−0.15 keV inside the shock. Therefore, even

within the errors, this is inconsistent with the expectedtemperature jump of 1.19, with the highest rise permit-ted giving a factor of 1.07. However, as noted above,temperature rises associated with weak shocks are verydifficult to detect, and due to projection effects, mea-sured rises are expected to be lower than might be ex-pected based on shock strengths alone (e.g. Randall et al.2011). In addition, the gas may cool due to adiabatic ex-pansion (McNamara & Nulsen 2007). Also, we note thatthe temperature drops precipitously in the next annulus

inward from the annulus just inside the shock bound-ary. This may indicate that the temperature of the gasjust inside the shock boundary was also previously muchlower before being shocked, and then the rise in tempera-ture in this region may be higher than we have estimatedabove.In addition, we fitted a projected density model to the

surface brightness profile in a wedge to the SW with PA250 to 340 from N out to a radius of 100′′ to charac-terize the inner shocks in this direction. We find similarresults to the SW as we did to the NE for the first innershock. We find a density jump of a factor of 1.26± 0.025at a radius of 48± 0.4 arcsec (34± 0.3 kpc). However, ascan be seen in the surface brightness distribution in theimages (i.e. Fig. 3), the second inner shock edge seemsless sharp and extends to larger radii in the SW than inthe NE. We do not find a density jump corresponding tothe second inner shock to the SW, only a change in slopeat a radius of 107 arcsec (75.5 kpc).

7. SPIRAL FEATURE

The spiral feature visible in Fig. 7 is similar to thatseen in simulations of gas sloshing in cluster centers (As-casibar & Markevitch 2006). The sloshing sets up coldfronts and the distinctive spiral morphology. We there-fore would expect the excesses seen in Fig. 7 to be visibleas excesses in surface brightness profiles containing theseregions. Temperature profiles should show cooler gas co-incident with the surface brightness enhancements. Inaddition, the simulations predict that the bright, slosh-ing, spiral region will contain gas of lower entropy ascluster central gas is displaced to larger radii. As shownin §5, the spiral excess is coincident with regions of lowtemperature and entropy in projected maps.We have extracted surface brightness profiles from

wedges in three directions: SW, NE, and NW. The SWcorresponds to the bright, inner part of the spiral, whilethe NE includes the outer region of the spiral, and theNW is largely free from any spiral excess emission andserves as a comparison region. The sectors used for theprofiles are shown superposed on the 0.3− 2.0 keV resid-ual image in Fig. 19. The surface brightness profiles forthe three regions are shown in Fig. 20. Error bars aresmaller than the symbols. Relative to the NW, non-spiral region, the SW shows excess emission from ap-proximately 60′′− 195′′ (42 – 138 kpc), corresponding tothe inner part of the sprial. To the NE, excess emissionis seen beyond approximately 110′′ (78 kpc). Note thatthe enhancement in the NW in the ≈ 10 − 20′′ (7 – 14kpc) region shows that the bubble rims are brightest inthis region, which also corresponds to cooler gas seen inHα (Figs. 9, 10).We have extracted spectra in the three wedges and

determined projected temperature profiles. The spectrawere extracted separately for each of the observationsas well as for the corresponding background files. Thespectra for each region were fitted simultaneously usingan APEC thermal plasma model. Absorption was fixedat the Galactic value and elemental abundances were al-lowed to vary. Projected temperature profiles comparingthe SW and NW (non-spiral) regions and the NE andNW regions are shown in Figs. 21 and 22, respectively.In both cases, significant drops in temperature are seenin the regions corresponding to the surface-brightness ex-

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6 Blanton et al.

cesses associated with the spiral described above. Inaddition, the high surface brightness ≈ 10′′ − 20′′ (7 –14 kpc) region in the NW has cooler temperatures thanthose radii regions to the SW and NE. This is likely due,at least in part, to the larger contribution to the emis-sion measure from the bright, compressed, cool, bubblerims to the NW at these radii as compared to the sameradii to the SW and NE, where the bubble rims are notas bright.In order to examine the bright region of the spiral to

the SW in more detail, we have fitted a projected den-sity model to the surface brightness profile, as describedabove for the NE sector shock fits. To focus on the coldfront / spiral edge, we fit only regions with r > 70′′. Wefind a density jump of a factor of 1.12+0.022

−0.011 at a radiusof 154± 1.5 arcsec (109± 1 kpc) from the cluster center.We extracted spectra in larger bins to the SW, and

performed a spectral deprojection as described above forthe NE. Profiles of temperature, density, and pressureare shown in Fig. 23. Dashed lines, going from smallerto larger annuli, indicate the positions of the first innershock, the second inner shock / edge, and the exterioredge of the cold front / SW spiral. Since the deprojec-tion introduces some scatter, particularly in the regionbetween the inner shocks, we have also plotted the pro-jected temperature profile as well as the pressure profileusing the projected temperatures (shown as open cir-cles). A temperature rise is seen associated with the firstinner shock, but not the second inner shock. A cleardensity fall off is seen at the outer edge of the SW spi-ral. The temperatures within the sprial region are coolerthan those outside of it.Projected abundance profiles to the SW and NE are

shown in Fig. 24. The dashed line marks the outer edgeof the spiral to the SW (at r = 154′′, as determinedabove). The abundance is higher in the bright, SW, spi-ral region, than in the corresponding radial region to theNE. Profiles of entropy for the SW and NE regions are

shown in Fig. 25. The entropy is defined as S = kT/n2/3e ,

and projected temperature values were used. As in Fig.24, the outer edge of the SW spiral region is markedwith a dashed line. There is clearly a cross-over in theentropy profiles for the SW and NE regions near this ra-dius. From r ≈ 70− 150′′, low entropy values are foundcoincident with the SW spiral excess. In the NE, the spi-ral excess is at larger radii, and this is seen in the entropyprofile, where the values are low in the NE with radiigreater than approximately 190′′. This is striking con-firmation of the predictions from sloshing models, wherecentral, low entropy, cluster gas is displaced to largerradii (i.e. Ascasibar & Markevitch 2006).The sum of the evidence, including the surface bright-

ness profiles, and temperature, abundance, and entropydistributions, points to the spiral being a cold front /sloshing feature resulting from an off-axis merger earlierin the cluster’s history.

8. X-RAY CAVITIES

Clear cavities (or “bubbles”) in the X-ray emission areseen in the Chandra images to the N and S of the AGN.In addition, there is a small bubble bounded by a narrowX-ray filament to the NW and a bubble separated fromthe S bubble to the SE. A very small depression is also

seen to the E. These features are all filled with 4.8 GHzradio emission as seen in Fig. 6. As described in §3,we created a radio spectral index map using the 1.4 and4.8 GHz VLA data. The map is shown in Fig. 26 withcontours of 1.′′5 Gaussian-smoothed X-ray emission in the0.3− 10.0 keV band superposed.The spectral index is flattest at the position of the

radio and X-ray core, and steepens into the radio lobes.The regions we have identified as outer bubbles, to theNW and SE, are associated with regions with distinctlysteeper spectral indices. This is consistent with thesebubbles resulting from an earlier stage in the currentoutburst, or from a separate, earlier AGN outburst, sincethe high-energy electrons age faster than the lower energyelectrons, resulting in steepening of the spectrum overtime. The radio emission “leaking” out of the N bubblethrough the bubble rim directly N of the AGN has aspectral index consistent with that filling the N lobe,making it likely that this emission is part of the currentAGN outburst.Obvious additional bubbles are not seen outside of

this central region in the images, including the unsharp-masked images. Also, lower frequency radio emission at330 MHz (Zhao et al. 1993) has a similar extent as the1.4 and 4.8 GHz emission. To search for more bubblesat larger radii, we have made a pressure-difference map.The map was created by fitting a 2D beta model to apressure map with 8′′ bins, and a minimum of 10000background-subtracted counts for each region used for aspectral fit. This corresponds to the temperature mapshown in Fig. 12. The center was fixed to the positionfound in the 2D beta model fit to the surface brightness,described in 4.1.2. The values for the ellipticity and po-sition angle of the ellipse, 0.17 and 119 from W, respec-tively, were similar to those found for the surface bright-ness fit. The pressure-difference map is shown in Fig. 27,with 4.8 GHz radio contours superposed. Regions of lowpressure are evident to the N and S of the AGN, alongthe current axis of the radio source. For both the N andS apparently low-pressure regions on the map, we haveextracted spectra within circular apertures covering theregions, as well as comparison regions in surrounding cir-cular annuli. We have calculated “projected” pressures,defined as kT (A)1/2, where A is the APEC normaliza-tion, for the apparent bubbles (low pressure regions) andthe comparison annuli. For the N bubble, we find a sig-nificance in the lower projected pressure of 2.3σ com-pared to the comparison annulus, and for the S bubble,the significance is 2.2σ. These regions of lower pressuremay represent outer bubbles from an earlier outburst (ormultiple earlier outbursts) of the AGN. Future higher dy-namic range radio data may give further evidence thatthese features are related to AGN activity.Approximating both of these possible bubbles as

spheres with radii of 34 kpc, located 75 kpc from the clus-ter center, we calculate their energy input into the ICMas E = 4PV (Churazov et al. 2002). This assumes thatthe bubbles are filled with relativistic plasma (γ = 4/3).Using the average pressure at the cluster radius of 75 kpcof P ≈ 6 × 10−11 dyn cm−2, we find that each bubblecan add 1× 1060 erg to the ICM.

9. DISCUSSION AND CONCLUSIONS

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Very Deep Chandra Observation of A2052 7

We have presented first results from a very deep Chan-dra observation of Abell 2052. Detailed structure is seenin the inner part of the cluster, including bubbles, brightshells, and filaments. Radio emission at 4.8 GHz is seento fill bubbles to the N and S of the AGN, as well asouter bubbles to the NW and SE, and a small bubble tothe E. Hα emission is coincident with the brightest andcoolest regions in the cluster center, including the E-Wbar and the filament in the N bubble, indicating that atleast some gas is cooling to T ≈ 104 K.An inner shock is clearly seen surrounding the cluster

center, as well as a second feature exterior to the firstthat is also most likely a shock. Both edges in surfacebrightness can be described as arising from shocks withMach numbers ≈ 1.2. For the inner shock, evidence foran associated temperature rise is seen in a three-colorimage. Also, a temperature profile reveals a significantincrease inside this region, consistent with that expectedgiven the shock strength. Such temperature rises associ-ated with weak shocks driven by AGN in the centers ofcool core clusters have only rarely been measured, giventhe narrow widths of the shocks, the small magnitudesof the temperature rises, and the cooling related to adia-batic expansion and the projection of cluster gas at largerradii.A spiral feature is seen, and is well-described as re-

sulting from gas sloshing related to a cluster-cluster orsub-cluster merger earlier in the lifetime of A2052. Thereis also evidence of dynamical activity in the cluster fromoptical spectroscopy: the central cD has a fairly large pe-culiar velocity (290 ± 90 km s−1) relative to the clustermean (Oergerle & Hill 2001). The X-ray spiral is bright-est to the SW, and continues around the cluster centerto the E and NE. The SW portion of the excess emis-sion was shown in Lagana et al. (2010) using a shorterChandra exposure, and in de Plaa et al. (2010) usinga deep XMM-Newton observation. The spiral structurewas not seen, however, before this very deep Chandra ob-servation. Lagana et al. presented several residual Chan-dra images of cool core clusters, and noted that A2052was an exception in not exhibiting a spiral feature in theavailable data, and de Plaa et al. described the SW ex-cess as a cold front. Here, in addition to exhibiting anexcess in surface brightness on a 2D model-subtractedChandra image, the brightness distribution is confirmedusing surface brightness profiles in different sectors acrossthe image. The spiral is also shown to contain gas cooler

than its surroundings in both temperature maps and sec-tor profiles. Regions of low entropy are found coincidentwith the spiral surface-brightness excess. Finally, theabundance is higher in the spiral region than its sur-roundings. This is consistent with central, low-entropy,high-metallicity gas sloshing out to larger radii. There-fore, sloshing can play a part in redistributing the met-als within a cluster (Simionescu et al. 2010, de Plaa etal. 2010). Outbursts from the AGN also play a role inmetal redistribution (Kirkpatrick et al. 2009). Detailedmeasurements of the spectral properties of similar diffusespiral excesses have only rarely been measured. WhileLagana et al. (2010), for example, presented evidenceof excess surface-brightness spirals in several systems, inmany cases temperature declines were not detected as-sociated with the spiral features, and if they were, theywere most often only measured for the bright, inner spiralregions.While the radio emission shows clear correspondence

with deficits in the X-ray emission, and the extended ra-dio structure is likely related to typical radio lobes fromthe AGN, there may be some component of radio mini-halo emission. A correlation has been found betweenthe presence of sloshing features in clusters and mini-halos (ZuHone, Markevitch, & Brunetti 2011), and thesemini-halos may result from reacceleration of relativisticelectrons by turbulence associated with sloshing (Maz-zotta & Giacintucci 2008). With our current radio data,however, we do not see obvious correspondence betweenthe radio emission and the spiral sloshing feature.There is evidence for outer bubbles related to one or

more earlier outbursts from the AGN. While not seenin the surface brightness images, deficits are evident ina pressure-residual map after subtracting off a model ofthe average pressure distribution. The deficits are seen tothe N and S of the cluster center, in line with the currentaxis of the radio lobes. Each of these bubbles could injectup to 1× 1060 erg into the intracluster medium.

Support for this work was provided by the NationalAeronautics and Space Administration, through ChandraAward Number GO9-0147X. Basic research in radio as-tronomy at the Naval Research Laboratory is supportedby 6.1 Base funding. SWR was supported in part by theChandra X-ray Center through NASA contract NAS8-03060. We thank Frazer Owen for useful discussions.

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TABLE 1Chandra X-ray Observations

Obs ID Date Roll Angle Data Mode Exp(deg) (ksec)

890 2000-09-03 265.1 FAINT 37.235807 2006-03-24 98.9 VFAINT 128.6310477 2009-06-05 221.2 VFAINT 62.0310478 2009-05-25 208.2 VFAINT 120.6710479 2009-06-09 217.1 VFAINT 65.7610480 2009-04-09 112.2 VFAINT 20.1510879 2009-04-05 112.2 VFAINT 82.2110914 2009-05-29 208.2 VFAINT 39.3610915 2009-06-03 221.2 VFAINT 15.1610916 2009-06-11 217.1 VFAINT 35.4710917 2009-06-08 217.1 VFAINT 55.99

TABLE 2VLA Radio Observations

Obs. Code Date VLA Configuration Frequency Bandwidth Duration(MHz) (MHz) (hours)

AS355 1988-11-30 A 4835.1/4885.1 50/50 3.0AS355 1989-03-30 B 4835.1/4885.1 50/50 2.4AS355 1989-06-26 C 4835.1/4885.1 50/50 2.6AS355 1988-11-30 A 1464.9/1514.9 50/50 3.0AS355 1989-03-30 A 1464.9/1514.9 50/50 2.1

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10 Blanton et al.

30.0 15:17:00.0 30.0 16:00.0 15:30.0

20:00.0

15:00.0

10:00.0

05:00.0

7:00:00.0

55:00.0

6:50:00.0

45:00.0

Right ascension

Dec

linat

ion

Fig. 1.— Chandra ACIS image of A2052 in the 0.3−10.0 keV band showing all CCD chips used in the analysis (the S4 chip was excluded)and illustrating the different roll angles used in the observations.

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Fig. 2.— Unsmoothed Chandra image in the 0.3 − 2.0 keV band of the central region of A2052. The image reveals detailed structurerelated to the interaction of the AGN with the ICM, with important features labeled.

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12 Blanton et al.

Fig. 3.— Three-color Chandra image of A2052. Red is 0.3 − 1.0 keV, green is 1.0 − 3.0 keV, and blue is 3.0 − 10.0 keV. Cavities arevisible to the north and south of the AGN, surrounded by bright rims. Exterior to the bright rims, a slightly N-S elliptical shock is seenwith hard (blue) emission.

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Fig. 4.— Composite Chandra X-ray (red), VLA 4.8 GHz (blue), and SDSS r-band (green) 6.′6× 5.′8 image of Abell 2052.

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14 Blanton et al.

Fig. 5.— Chandra image in the 0.3 − 10.0 keV band, smoothed with a 1.′′5 radius Gaussian, with contours of optical r-band emissionfrom the SDSS superposed.

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Fig. 6.— Unsharp-masked Chandra 0.3− 10.0 keV image of A2052 with 4.8 GHz radio contours superposed. Radio emission fills X-raycavities to the N and S, as well as outer cavities to the NW, S-SE, and E. The cavities are surrounded by X-ray bright rims. A filamentextends into the N cavity, and a narrow filament surrounds the NW hole. Ripple-like features are seen surrounding the cluster center,corresponding to weak shocks.

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16 Blanton et al.

Fig. 7.— Residual image in the 0.3− 2 keV band of the central 5.′66 (240 kpc) radius region of A2052 resulting from the subtraction ofa 2D beta model. The image has been smoothed with a 7.′′38 Gaussian. In addition to the bubble rims seen in the center of the image, onlarger scales, a spiral is visible extending from the SW to the NE. The linear feature in the SW is a chip-edge artifact.

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Fig. 8.— High-resolution temperature map of the central region of A2052 with X-ray surface brightness contours in the 0.3 − 10.0keV range superposed. The scale bar is kT in units of keV. The rims surrounding the X-ray cavities are cool, and the coolest regions, inprojection, are coincident with the brightest regions of the rims.

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Fig. 9.— Hα contours from McDonald et al. (2010) superposed onto the central portion of the high-resolution temperature map fromFig. 8. The coolest regions seen in the X-ray are coincident with emission in Hα, representing gas with T ≈ 104 K. The scale bar is kT inunits of keV.

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Fig. 10.— Chandra image in the 0.3 − 10.0 keV band, smoothed with a 1.′′5 radius Gaussian, and superposed with contours of Hαemission (McDonald et al. 2010). The X-ray brightest regions in the cluster center show excellent correspondence with the Hα emission.

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Fig. 11.— Pseudo-pressure map of the central region of A2052 with X-ray surface brightness contours in the 0.3 − 10.0 keV rangesuperposed. A region of high pressure is seen surrounding the cluster center, outside of the bubble rims, and coincident with the innershock feature.

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Fig. 12.— Temperature map using a minimum of 10000 background-subtracted counts for each spectral fit. Contours of residual surfacebrightness showing the spiral feature are superposed. The spiral traces out a region of cooler temperatures. The scale bar is kT in units ofkeV. Errors range from 1% in the inner regions to 5% in the outskirts of the map. Holes to the far S and SW are excluded point sourceregions.

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Fig. 13.— Temperature map with the same f.o.v. as Fig. 12, but at higher resolution and using a minimum of 2000 background-subtractedcounts for each spectral fit. The map contains results from more than 80000 spectral fits. The scale bar is kT in units of keV. Errors rangefrom 2% in the cluster center to 14% in the outer parts of the frame.

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Fig. 14.— Pseudo-pressure map using the spectral fits that resulted in the temperature map in Fig. 13. As in Fig. 11, the slightly N-Selliptical region corresponding to the inner shock is seen. There is no evidence for a region of pressure that corresponds with the spiralfeature seen in Fig. 7.

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24 Blanton et al.

Fig. 15.— Zoomed-in view of the pseudo-pressure map shown in Fig. 14 with X-ray surface brightness contours superposed. The firstinner jump in surface brightness traces out a jump in pressure, and the second inner surface brightness jump traces out a region of enhancedpressure.

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Fig. 16.— Pseudo-entropy map with excess surface brightness contours (after 2D beta model subtraction) superposed. There is an overalldecrease in entropy towards the cluster center and the sprial feature is conicident with low entropy structure in the map.

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Fig. 17.— Projected abundance map with contours of the spiral excess superposed. A region of high metallicity is coincident with theSW portion of the spiral. Abundances shown are relative to solar. The region of apparent high abundance in the NW bubble rim is atleast partly the result of fitting a one-temperature model to the projected multi-temperature gas in this area. Errors range from 5% in theinner regions to 23% in the outskirts of the frame, with the majority of the errors at the 10− 15% level across the map.

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Very Deep Chandra Observation of A2052 27

kT

(ke

V)

1

2

3

4 NEn

e (

cm

−3)

0.01

Radius (arcsec)

10 100

P (

x 1

0−

11 d

yn

cm

−2)

10

Fig. 18.— Deprojected temperature profile, and profiles of density and pressure for the NE sector. Positions of the inner shocks aremarked with dashed lines. A clear rise in temperature and pressure is seen inside the innermost shock.

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Fig. 19.— Residual image in the 0.3− 2 keV band of the central 5.′66 (240 kpc) radius region of A2052 resulting from the subtraction ofa 2D beta model and smoothed with a 7.′′38 Gaussian. Superposed on the image are the SW, NE, and NW sectors from which the surfacebrightness and temperature profiles shown in Figs. 18, 20, 21, 22, and 23 were extracted.

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Radius (arcsec)10 100

Surf

ace B

rightn

ess (

ct/s/a

rcm

in2)

0.1

1

NW

NE

SW

Fig. 20.— Surface brightness profiles in the 0.3− 10 keV band corresponding to the sectors shown in Fig. 19. Clear excesses are seen inthe regions of surface brightness enhancement associated with the spiral feature in Figs. 7 and 19. For the SW, the excess extends from≈ 60′′ − 195′′, while for the NE, the excess is seen at radii beyond ≈ 110′′.

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30 Blanton et al.

Radius (arcsec)0 50 100 150 200 250 300

kT

(keV

)

1

1.5

2

2.5

3

3.5

4

4.5

NW

SW

Fig. 21.— Projected temperature profiles for the SW and NW sectors shown in Fig. 19. The SW sector corresponds with the bright,inner, spiral region, while the NW sector is the non-spiral, comparison region. The SW spiral excess corresponds with regions of coolertemperature in the radial range ≈ 60′′ − 140′′. The profiles converge beyond ≈ 140′′.

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Radius (arcsec)0 50 100 150 200 250 300

kT

(keV

)

1

1.5

2

2.5

3

3.5

4

4.5

NW

NE

Fig. 22.— Projected temperature profiles for the NE and NW sectors shown in Fig. 19. The NE sector corresponds with the outer spiralregion, while the NW sector is the non-spiral, comparison region. Cooler temperatures are seen associated with the NE spiral excess (radii> 160′′).

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32 Blanton et al.

kT

(ke

V)

1

2

3

4 SWn

e (

cm

−3)

0.01

Radius (arcsec)

10 100

P (

x 1

0−

11 d

yn

cm

−2)

10

Fig. 23.— Profiles of temperature, density, and pressure in the SW sector. Filled circles indicate results from deprojected fits. The opencircles show the projected temperature profile and the pressure profile derived using the density and the projected temperatures. Dashedlines show the positions of the first inner shock, the second inner shock / edge, and the cold front / SW spiral edge, going from smaller tolarger radii.

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Radius (arcsec)0 50 100 150 200 250

Ab

un

da

nce

(x s

ola

r)

0.4

0.6

0.8

1

1.2

1.4

NE

SW

Fig. 24.— Projected abundance profiles for the SW and NE regions. The dashed line indicates the outer edge of the SW spiral / coldfront. The abundances are higher inside the SW spiral region (from ≈ 70′′ −120′′) compared to the corresponding radial region to the NE.

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34 Blanton et al.

Radius (arcsec)0 50 100 150 200 250

Entr

opy (

keV

cm

2)

50

100

150

200

250

SW

NE

Fig. 25.— Entropy profiles for the SW and NE regions with entropy defined as S = kT/n2/3e , and using projected temperatures. The

dashed line indicates the outer edge of the SW spiral. The spiral surface-brigthness excess is very well traced by the entropy structure.The spiral excess to the SW (r ≈ 70− 150′′) corresponds with a region of lower entropy. At larger radii r > 190′′, the spiral excess in theNE also is shown to have lower entropy values as compared to the non-spiral region in the SW at these large radii.

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Very Deep Chandra Observation of A2052 35

Fig. 26.— Radio spectral index map created using the 1.4 and 4.8 GHz data. Contours of 0.3 − 10.0 keV X-ray surface brightness aresuperposed. The outer bubbles to the NW and SE are filled with radio emission with steeper spectral index, consistent with these regionsbeing inflated by an earlier outburst of the AGN.

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36 Blanton et al.

-8E-05 -6E-05 -4E-05 -2E-05 0 2E-05 4E-05 6E-05

15:17:00.0 50.0 40.0 16:30.0

06:00.0

05:00.0

04:00.0

03:00.0

02:00.0

01:00.0

7:00:00.0

59:00.0

58:00.0

57:00.0

6:56:00.0

Right ascension

Dec

linat

ion

Fig. 27.— Pressure residual map created by subtracting off a 2D beta model fitted to a pseudo-pressure map with 4.8 GHz radio contourssuperposed. The inner shock is seen as a pressure enhancement exterior to the radio lobes. In addition, large deficits in pressure are seento the N and S of the cluster center. These may represent “ghost cavities” related to an earlier AGN outburst.