SZA observations of z\geq 1 galaxy clusters

Galaxy Clusters at : Gas Constraints from the Sunyaev-Zel’dovich Array

Abstract

We present gas constraints from Sunyaev-Zel’dovich (SZ) effect measurements in a sample of eleven X-ray and infrared (IR) selected galaxy clusters at 1, using data from the Sunyaev-Zel’dovich Array (SZA). The cylindrically integrated Compton- parameter, , is calculated by fitting the data to a two-parameter gas pressure profile. Where possible, we also determine the temperature of the hot intra-cluster plasma from Chandra and XMM-Newton data, and constrain the gas mass within the same aperture () as . The SZ effect is detected in the clusters for which the X-ray data indicate gas masses above , including XMMU J2235-2557 at redshift , which to date is one of the most distant clusters detected using the SZ effect. None of the IR-selected targets are detected by the SZA measurements, indicating low gas masses for these objects. For these and the four other undetected clusters, we quote upper limits on and , with the latter derived from scaling relations calibrated with lower redshift clusters. We compare the constraints on and X-ray derived gas mass  to self-similar scaling relations between these observables determined from observations of lower redshift clusters, finding consistency given the measurement error.

Subject headings:
cosmology: observations — cosmic background radiation — galaxies: clusters: general — galaxies: clusters: intracluster medium

1. Introduction

The Sunyaev-Zel’dovich (SZ) effect is a distortion in the spectrum of the cosmic microwave background (CMB) radiation caused by inverse Compton scattering of CMB photons with the ionized gas in galaxy clusters (Sunyaev & Zel’dovich, 1972; Birkinshaw et al., 1991; Carlstrom et al., 2002). The amplitude of the SZ effect is commonly described by the Compton -parameter, which for a thermal population of electrons is given by the integral of the gas pressure along the line of sight through the cluster:

(1)

In this expression, is the Thomson scattering cross section, is the electron mass, is the speed of light, is the gas pressure, and the integration is along the line-of-sight. Integrating over the solid angle yields the integrated Compton parameter , which is proportional to the thermal energy of the cluster (Motl et al., 2005; Bonamente et al., 2008, hereafter B08).

This paper reports observations of clusters made with the Sunyaev-Zel’dovich Array (SZA), and aims to provide constraints on the gas properties of the clusters, and a comparison to existing scaling relations.  In Section 2 we describe the sample of clusters, Section 3 describes the collection and analysis of the SZA data, and Section 4 presents an analysis of cluster X-ray data (where available) from the Chandra and XMM-Newton observatories. The results and discussion, including a comparison of SZ and X-ray cluster gas properties, are given in Section 5. Throughout this document we use the cosmological parameters =73 km s Mpc, and . Unless otherwise stated, all uncertainties correspond to the 16% and 84% percentiles of the probability distribution function (68% confidence interval).

Cluster Detection, (Ref.)45 46 Short Baselines47 48 49
FWHM50 51 B52
(hrs) (arcsec) (mJy) (K) () ()
JKCS 041 1.90 02 26 44 -04 41 37 IR, (1) 30.6 86.6 96.7 0.13 19.9
2XMM J083026.2+524133 0.99 08 30 26 +52 41 33 X-ray, (2) 23.3 81.7 109.3 0.17 24.4
RX J0848+4453 1.27 08 48 35 +44 53 49 IR, (3) 44.5 81.4 111.6 0.11 15.5
RX J0849+4452 1.26 08 49 58 +44 51 55 X-ray, (4) 25.5 82.3 110.7 0.15 21.1
RX J0910+5422 1.11 09 10 44 +54 22 09 X-ray, (5) 19.1 83.6 107.1 0.17 24.3
RX J1252-2927 1.24 12 52 54 -29 27 17 X-ray, (6) 12.2 97.8 166.9 0.28 22.0
Cl J1415.1+3612 1.03 14 15 11 +36 12 03 X-ray, (7,8) 55.353 95.9 118.1 0.12 13.6
ISCS1438.1+3338 1.41 14 38 09 +34 14 19 IR, (9) 17.5 110.9129.1 0.21 18.8
SpARCSJ1638 1.20 16 38 52 +40 38 43 IR, (10) 36.0 78.9 108.1 0.13 19.5
XMMU J2235-2557 1.39 22 35 21 -25 57 42 X-ray, (11) 42.1 103.7150.8 0.14 11.5
XMMXCS J2215.9-1738 1.46 22 15 58 -17 38 03 X-ray, (12) 10.8 107.8130.1 0.25 22.8
Table 1Cluster Sample

2. Sample selection

We obtained SZA observations of an ad hoc sample of eleven clusters with 1 discovered in either X-ray or infrared (IR) imaging surveys — basic information about the clusters are given in Table 1. Surveys in these bands can yield large numbers of high redshift cluster candidates using a variety of methods. These include the red-sequence in the optical (Gladders & Yee, 2000, 2005), its extension into the IR (Stanford et al., 2005; Andreon et al., 2008; Eisenhardt et al., 2008; Muzzin et al., 2009), and imaging surveys and/or serendipitous detection in X-rays (e.g. Stanford et al., 2006; Lamer et al., 2008).

X-ray observations provide direct evidence for the hot plasma which typically constitutes of the cluster total mass; seven clusters in the sample are the most massive X-ray detected systems at redshift above one. Since this is the same plasma which causes the SZ effect, clusters in the sample originally detected in X-rays are expected to have significant SZ signal, provided they are of sufficient gas mass and temperature.

The IR-detected clusters in the sample were selected as optically rich candidates with properties typical of massive clusters: ISCS1438.1+3338 was detected in the Spitzer/IRAC Shallow Survey as an overdensity of galaxies with photometric redshifts between ; member galaxies were confirmed with Keck optical spectroscopy to have . The most massive spectroscopically confirmed cluster from the SpARCS North Survey is SpARCSJ1638, with initial detection via two-filter imaging. JKCS 041 was discovered using a modified red-sequence method applied to J and K band data in the UKIRT Infrared Deep Sky Survey; Chandra follow-up revealed a low luminosity, diffuse source of X-ray emission at the cluster location, with a photometric redshift of 1.9. Also discovered in the IR, member galaxies of RX J0848+4453 exhibit very red J-K colors, with follow up spectrocopy confirming the member redshifts are within of each other. This cluster has also been observed in the X-ray with Chandra;  Santos et al. (2008) present a recent analysis.

The most massive, high redshift cluster candidates in these different surveys provide a starting point for studies of the SZ effect in galaxy clusters at . Constraints on from the SZ effect alone provide useful information on the presence of hot gas, while joint analysis with X-ray data allows comparison with more local samples via scaling relations, to test for evolutionary effects.

3. Sunyaev-Zel’dovich Effect Analysis

3.1. SZA Observations

Figure 1.— CLEANed SZA short (2k) baseline images of the three clusters with significant SZ effect detections: Left to right, XMMU J2235-2557  Cl J1415.1+3612 and 2XMM J083026.2+524133, with the colorscale in Jy/beam. The contours begin at and are spaced at unit intervals of the map rms . The white ellipse represents the half-power point of the elliptical gaussian that approximates the main lobe of the synthesized beam. Radio sources have been removed for display purposes.

The SZA is an interferometric array comprising eight 3.5-meter telescopes, capable of observations in an 8-GHz-wide band centered on 31 GHz or 90 GHz. The instrument was configured to operate at 31 GHz for the observations reported here — see Muchovej et al. (2007) for further details. The field of view of the SZA is given by the primary beam of a single telescope, of FWHM approximately 11′ at the center of the 31 GHz band, with typical system temperatures 40K at this frequency.

Observations of each cluster were performed with different array configurations. All observations of ISCS1438.1+3338 and two thirds of the tracks on Cl J1415.1+3612 were observed from the OVRO valley floor site, using a compact six-telescope plus two outrigger array, denoted ‘V’ array here. JKCS 041 was initially observed for twelve days at the CARMA site. An imaging array configuration (denoted ‘I’) was used, with no outriggers but higher sensitivity to typical cluster angular scales. A further eight days of data were taken in a ‘low dec’ plus outrigger array, or ‘L’ array. This configuration is similar to ‘V’ array, but with the array stretched North-South to prevent excessive shadowing for low declination clusters. Tracks on all other clusters were taken in ‘L’ array.

Pairs of close-packed telescopes form short baselines (typically of order 4-20m or 0.4-2), which are sensitive to the signal from clusters on angular scales of order . The outrigger telescopes form long baselines (50m or 2-10) between themselves and the close-packed antennas; these baselines allow measurement of contaminating radio sources which could otherwise mask the SZ effect. The long baseline dirty map noise is typically mJy, with resolution . Further details of the SZA observations presented here, including on-source integration time and sensitivity, and effective resolution (the synthesized beam) of the short baseline maps, are given in Table 1.

SZA data are processed in a pipeline developed within the SZA collaboration for the reduction and calibration of interferometric data, described in detail in Muchovej et al. (2007). The pipeline produces calibrated visibilities — samples of the Fourier transform of the sky brightness distribution multiplied by the primary beam:

(2)

where is the normalized antenna beam pattern, is the sky intensity distribution, and are the baseline lengths projected onto the sky, and and are direction cosines measured with respect to the axes. Fourier transforming the visibility data gives the sky convolved with the synthesized beam, or the ‘dirty map’.

Figure 1 presents CLEANed images made from only the SZA short-baseline data of the clusters in the sample for which we detect the SZ effect at , i.e., 2XMM J083026.2+524133, Cl J1415.1+3612, and XMMU J2235-2557. Radio sources have been identified and removed using the long and short baseline data. Unresolved radio sources were found within of the cluster center in Cl J1415.1+3612, and XMMU J2235-2557. Resolved emission from two low redshift galaxies was detected: from NGC 5529 4.9 from the Cl J1415.1+3612 position, and from NGC 7314 7.8 from the XMMU J2235-2557 position. No cluster in the sample has more than three detected radio sources within the SZA field of view.

Cluster Obs ID Detector Exposure time # Source photons nH Column Density
(ks) ( cm)
2XMM J083026.2+524133 0092800201 MOS1,PN 60.0, 55.9 249554 4.2
Cl J1415.1+3612 4163 ACIS-I 86.9 139555 1.1
RX J0910+5422 2227, 2452 ACIS-I 161.2 41156 1.9
RX J1252-2927 4198 ACIS-I 161.4 54057 6.1
RX J0849+4452 1708, 927 ACIS-I 186.6 39258 2.8
RX J0848+4453 1708, 927 ACIS-I 186.6 14459 2.8
XMMU J2235-2557 6975, 6976, 7367, 7368, 7404 ACIS-S 195.5 153260 1.5
XMMXCS J2215.9-1738 7919, 8566 ACIS-S 85.9 16161 2.0
0106660601 MOS1,MOS2,PN 81.0, 82.1, 60.0
0106660101 MOS1,MOS2,PN 55.8, 53.1, 42.7
0106660201 MOS1,MOS2,PN 35.7, 37.7, 24.5 68662 2.0
JKCS 041 9368 ACIS-S 78.8 11463 2.3
64
Table 2Chandra and XMM-Newton observations

3.2. Constraints on the integrated SZ effect signal

For each cluster, is constrained by fitting a model to the data; the model map is generated by integrating a gas pressure profile along the line of sight as in Equation 1. The map is multiplied by the primary beam, Fourier transformed, interpolated at the coordinates of the measured visibilities and the evaluated for the model against the data. We use the spherically symmetric Nagai et al. (2007) model which describes the pressure as a function of radius as

(3)

In Equation 3, is the pressure normalization, is the characteristic scale radius, and , and are parameters describing profile slopes at intermediate (, outer () and inner () radii. As in Mroczkowski et al. (2009), the power-law indices of the pressure model are held fixed at (a,b,c)=(0.9,5.0,0.4).

The Monte Carlo Markov chain (MCMC) method described in Bonamente et al. (2004) is used to determine the probability distributions of the free cluster model parameters and ; positions of clusters without a significant decrement are fixed to the values in Table 1, but are otherwise variable. Following Muchovej et al. (2007), an elliptical gaussian is used to model the two resolved galaxies found in the sample (Section 3.1), while unresolved sources are described by one amplitude and two position parameters — the typical rms on unresolved source position is of order 0.3 arcsec. The free parameters of the cluster, resolved and unresolved source models are determined simultaneously with the MCMC method. Accepted (, ) parameter pairs in the MCMC analysis are used to calculate the cylindrically-integrated parameter over the solid angle of the cluster, via Equations 1 and 3.

For clusters with X-ray source photons, we measure out to a radius of as determined from the X-ray data (see Table 3), where is defined as the radius at which the mean cluster density falls to times the critical density at the cluster redshift :

(4)

The choice of allows our parameters to be compared directly to the scaling relations of B08, which were derived with for a large sample of low to intermediate redshift clusters. A fixed angular aperture of radius 30″ is used for clusters with X-ray photons, evaluating rather than (such clusters are not compared to the scaling relations).

The mean () and 68% confidence intervals are calculated from the resultant probability distributions of . If , where is the 14th percentile of the distribution, we quote the mean and 68% confidence interval for each cluster. If , we quote the 95% confidence upper limit on . The results are presented in Table 1, along with the equivalent gas mass constraints calculated from the low redshift  scaling relation of B08, which assumes self-similar evolution as , with and taken from all clusters in their sample. Errors on  include the uncertainty in the low redshift scaling relation parameters as well as the uncertainty in , but do not include errors introduced by geometric effects when performing the cylindrical integral or the intrinsic scatter in at fixed 65.

Note that these mass constraints are entirely independent of the  calculated in the following X-ray analysis, and serve as the only gas mass estimates available for clusters with insufficient X-ray data.

4. X-ray observations and data analysis

Cluster L
(keV) () (arcsec) (arcsec) ()
2XMM J083026.2+52413366 7.6 16 0.83 28.6 0.7 38.8 1.40
Cl J1415.1+361267 0.7
RX J1252-292768
RX J0910+542269
RX J0849+445270
XMMU J2235-255771
XMMXCS J2215.9-173872
Table 3Image and Spectral analysis of the X-ray data

4.1. Chandra and XMM-Newton data analysis

We analyzed Chandra and XMM-Newton observations for each cluster that has archival data.

The Chandra event files were reprocessed in CIAO 4.1 in order to apply the latest calibration available (CALDB 4.1). Periods of high background were excised following the prescription of Markevitch et al. (2003). A peripheral region 60-120″ from the cluster center was used to determine the local background; this region allows the background to be determined from the same chip as the cluster, given the limited angular size of the sources. This choice minimizes the effect of the temporal and spatial variability of the Galactic soft X-ray emission (e.g., Snowden et al., 1997).

For the spectral analysis of each cluster, we extracted individual spectra and matching response files from each observation separately (Table 2).

The cluster 2XMM J083026.2+524133 was detected serendipitously in two pointed XMM-Newton observations (Lamer et al., 2008), and these observations are the only available X-ray data for this cluster. We analyze the longest of the two observations, in which the cluster was detected in two of the three detectors, MOS1 and PN (Table 2). For cluster XMMXCS J2215.9-1738 we analyze both the Chandra data and the three longest observations with XMM-Newton.

The XMM-Newton data were reduced using the SAS 9.0 software and the calibration data available as of July 2009, and according to the method described in Nevalainen et al. (2005). In particular, periods of high background that affected the second half of the observation were excluded. We used a local background as measured in a peripheral region of each detector, similar to the method used for the Chandra data.

For the purpose of mass calculation and comparison to known scaling relations, we elected to only use clusters for which archival data are available, and with at least 300 source photons. This selection leaves us with seven clusters: 2XMM J083026.2+524133, Cl J1415.1+3612, RX J0910+5422, RX J0849+4452, RX J1252-2927, XMMU J2235-2557 and XMMXCS J2215.9-1738.

4.2. Image analysis

Event files for each cluster were merged if more than one observation was available, and images extracted using photons in the 0.7-7 keV band for ACIS-I observations, and in the 0.5-7 keV band for ACIS-S, EPIC-MOS and EPIC-PN observations (see Table 2). The same table also presents the number of source photons, after subtracting the expected number of background photons from the peripheral region.

The gas density is described using an isothermal model which, given the limited number of source photons, provides a good fit to all clusters with X-ray data:

(5)

Model parameters and are constrained using a Markov chain Monte Carlo method described in Bonamente et al. (2004), and are presented in Table 3. We fix throughout. Use of the beta model permits a direct comparison with the scaling relations presented in B08, obtained using the same isothermal model.

4.3. Spectral analysis

The spectra for each cluster were extracted from a circular region about the centroid of the X-ray emission given in Table 1. A radius of 30″ was used for all clusters except 2XMM J083026.2+524133 and Cl J1415.1+3612, for which we use 60″; the background spectrum was extracted from the surrounding 60-120″ region. Given the limited S/N of the spectra, the metal abundances were fixed at a fiducial value of  for all clusters. This approximation has a negligible impact on the results of our analysis.

We performed spectral fits to an optically thin model using the APEC emissivity code (Smith et al., 2001); the redshift, Galactic HI column density and solar abundance are fixed for each cluster (Table 2), leaving just the electron temperature and a normalisation constant. The resulting electron temperatures are presented in Table 3.

4.4. Mass measurement

The gas model parameters determined from the X-ray images and spectral constraints on the gas temperature are used to measure the X-ray gas mass . This is calculated via a spherical integration of out to for each sample in the Markov chain; this choice of radius allows a comparison of and  to the scaling relations of B08. The values of and  of each cluster are shown in Table 3, with the comparison to and previously measured scaling relations in Figure 2.

5. Results and Discussion

The SZA observations presented here demonstrate the efficacy of using the SZ effect as a cluster mass discriminator, independent of redshift. The SZ effect of the high mass clusters in the ad hoc sample of clusters was detected with SZA integration times comparable to those required for similar mass clusters at low redshifts. Specifically, the SZ effect was detected in the three clusters for which  and temperature as determined independently from X-ray data (see Table 3). The most distant cluster detected by the SZA is XMMU J2235-2557 at , which has a total mass within of  (Rosati et al., 2009). Weak lensing observations by Jee et al. (2009) indicate a total mass within 1 Mpc of . Similar masses are found for Cl J1415.1+3612 (Maughan et al. 2006) and 2XMM J083026.2+524133 (Lamer et al. 2008).

The lack of SZ detections for the other clusters strongly indicates they are lower mass systems; in particular, those originally discovered in the infrared have (see Table 1) and their null detection prevents investigation of optical-SZ scalings.

Figure 2.— Comparison of the upper limits and detections to  within , assuming self-similar evolution. The solid lines are the scaling relation measured at by B08, and its uncertainties. In order of X-ray gas mass, the clusters are RX J0849+4452, RX J0910+5422, XMMXCS J2215.9-1738, RX J1252-2927, XMMU J2235-2557, Cl J1415.1+3612, and 2XMM J083026.2+524133.

As a first step in investigating the SZ–mass scaling relationship at high redshift, we plot in Figure 2 the integrated Compton values against the X-ray gas mass determinations, assuming self-similar evolution. The clusters plotted include only those with robust X-ray gas mass constraints (see Table 3). For comparison with low redshift clusters, the solid lines in Figure 2 show the  scaling relationship presented in B08 and its uncertainties. The figure illustrates that there is good agreement between the scaling of the high-z clusters and that found in the low redshift sample. Measurements of more clusters are needed, however, to make a more definitive comparison. Ongoing SZ surveys from instruments such as ACT (Fowler et al., 2007) and SPT (Carlstrom et al., 2009) will provide much larger samples of SZ-selected clusters at high redshift (e.g., Vanderlinde et al., 2010).

Acknowledgments

The operation of the SZA is supported by NSF through grant AST-0604982 and AST-0838187. Partial support is also provided from grant PHY-0114422 at the University of Chicago, and by NSF grants AST-0507545 and AST-05-07161 to Columbia University. CARMA operations are supported by the NSF under a cooperative agreement, and by the CARMA partner universities. SM acknowledges support from an NSF Astronomy and Astrophysics Fellowship; CG, SM, and MS from NSF Graduate Research Fellowships; DPM from NASA Hubble Fellowship grant HF-51259.01.

Footnotes

  1. affiliation: Kavli Institute for Cosmological Physics, University of Chicago, Chicago, IL 60637
  2. affiliation: Department of Astronomy and Astrophysics, University of Chicago, Chicago, IL 60637
  3. affiliation: Department of Physics, University of Alabama, Huntsville, AL 35899
  4. affiliation: Space Sciences - VP62, NASA Marshall Space Flight Center, Huntsville, AL 35812
  5. affiliation: Department of Physics, University of Alabama, Huntsville, AL 35899
  6. affiliation: Kavli Institute for Cosmological Physics, University of Chicago, Chicago, IL 60637
  7. affiliation: Department of Astronomy and Astrophysics, University of Chicago, Chicago, IL 60637
  8. affiliation: Enrico Fermi Institute, University of Chicago, Chicago, IL 60637
  9. affiliation: Department of Physics, University of Chicago, Chicago, IL 60637
  10. affiliation: Kavli Institute for Cosmological Physics, University of Chicago, Chicago, IL 60637
  11. affiliation: Department of Astronomy and Astrophysics, University of Chicago, Chicago, IL 60637
  12. affiliation: Kavli Institute for Cosmological Physics, University of Chicago, Chicago, IL 60637
  13. affiliation: Department of Astronomy and Astrophysics, University of Chicago, Chicago, IL 60637
  14. affiliation: Department of Physics, University of Alabama, Huntsville, AL 35899
  15. affiliation: California Institute of Technology, Owens Valley Radio Observatory, Big Pine, CA 93513
  16. affiliation: Kavli Institute for Cosmological Physics, University of Chicago, Chicago, IL 60637
  17. affiliation: Department of Astronomy and Astrophysics, University of Chicago, Chicago, IL 60637
  18. affiliation: Department of Physics, University of Alabama, Huntsville, AL 35899
  19. affiliation: Space Sciences - VP62, NASA Marshall Space Flight Center, Huntsville, AL 35812
  20. affiliation: Space Sciences - VP62, NASA Marshall Space Flight Center, Huntsville, AL 35812
  21. affiliation: California Institute of Technology, Owens Valley Radio Observatory, Big Pine, CA 93513
  22. affiliation: Kavli Institute for Cosmological Physics, University of Chicago, Chicago, IL 60637
  23. affiliation: Department of Astronomy and Astrophysics, University of Chicago, Chicago, IL 60637
  24. affiliation: Kavli Institute for Cosmological Physics, University of Chicago, Chicago, IL 60637
  25. affiliation: Enrico Fermi Institute, University of Chicago, Chicago, IL 60637
  26. affiliation: Hubble Fellow
  27. affiliation: Columbia Astrophysics Laboratory, Columbia University, New York, NY 10027
  28. affiliation: Department of Physics, Columbia University, New York, NY 10027
  29. affiliation: Alfred P. Sloan Fellow
  30. affiliation: Columbia Astrophysics Laboratory, Columbia University, New York, NY 10027
  31. affiliation: Department of Physics and Astronomy, University of Pennsylvania, Philadelphia, PA 19104
  32. affiliation: Department of Astronomy, Columbia University, New York, NY 10027
  33. affiliation: California Institute of Technology, Owens Valley Radio Observatory, Big Pine, CA 93513
  34. affiliation: Department of Astronomy, Columbia University, New York, NY 10027
  35. affiliation: Kavli Institute for Cosmological Physics, University of Chicago, Chicago, IL 60637
  36. affiliation: Department of Astronomy and Astrophysics, University of Chicago, Chicago, IL 60637
  37. affiliation: Enrico Fermi Institute, University of Chicago, Chicago, IL 60637
  38. affiliation: Kavli Institute for Cosmological Physics, University of Chicago, Chicago, IL 60637
  39. affiliation: Department of Physics, University of Chicago, Chicago, IL 60637
  40. affiliation: California Institute of Technology, Owens Valley Radio Observatory, Big Pine, CA 93513
  41. affiliation: INAF-Osservatorio Astronomica di Brera, via Brera 28, 20121, Milano, Italy
  42. affiliation: HH Wills Physics Laboratory, University of Bristol, Tyndall Ave, Bristol BS8 1TL, UK.
  43. affiliation: University of California, Davis, CA 95618
  44. affiliation: Institute of Geophysics and Planetary Physics, Lawrence Livermore National Laboratory, Livermore, CA 94550
  45. Cluster references: (1) Andreon et al. (2008); (2) Lamer et al. (2008); (3) Stanford et al. (1997); (4) Rosati et al. (1999); (5) Stanford et al. (2002); (6) Rosati et al. (2004); (7) Redshift from Maughan et al. (2006); (8) Perlman et al. (2002); (9) Stanford et al. (2005); (10) Muzzin et al. (2009); (11) Mullis et al. (2005); (12) Stanford et al. (2006).
  46. On source integration time, unflagged data.
  47. Short baselines correspond to (0-2k).
  48. constraints from SZA data. Where there are sufficient X-ray counts to determine (see Table 3), is calculated within this radius; otherwise, an angular aperture of radius 30 arcsec is used. Upper limits are calculated at 95% confidence.
  49.  determined from constraints and scaling relations from Bonamente et al. (2008), and are independent of the X-ray determined gas mass .
  50. Synthesized beam approx. FWHM.
  51. Achieved rms noise in short baseline maps.
  52. Corresponding brightness sensitivity in short baseline maps.
  53. 34.1 hours of ‘V-array’ integration from Muchovej et al. (2007); 21.2 hours from ‘L-array’.
  54. 0.5-7 keV band
  55. 0.7-7 keV band
  56. 0.7-7 keV band
  57. 0.7-7 keV band
  58. 0.7-7 keV band
  59. 0.7-7 keV band
  60. 0.5-7 keV band
  61. 0.5-7 keV band
  62. 0.5-7 keV band
  63. 0.5-7 keV band
  64. footnotetext: Source photons are for a cluster-centric region of radius arcsec, except 2XMM J083026.2+524133 and Cl J1415.1+3612 for which we use arcsec. In comparison with Andreon et al. (2008), who find 223 source photons for JKCS 041 in a 60 arcsec aperture between 0.2-2 keV, we find 230 source photons in our 0.5-7 keV band in a 60 arcsec aperture.
  65. The apparent difference between the SZ-derived gas mass for Cl J1415.1+3612 presented here and that in Muchovej et al. (2007) is due to the different used; their value is reproduced from an earlier analysis of XMM-Newton data by Maughan et al. (2006), compared to our Chandra derivation in Section 4. When the same is used, the gas masses are consistent, as expected.
  66. 0.5-7keV used for spectral analysis
  67. 0.7-7keV used for spectral analysis
  68. 0.7-7keV used for spectral analysis
  69. 0.7-7keV used for spectral analysis
  70. 0.7-7keV used for spectral analysis
  71. 0.5-7keV used for spectral analysis
  72. 0.5-7keV used for spectral analysis

References

  1. Andreon, S., Maughan, B., Trinchieri, G., & Kurk, J. 2009, A&A, 507, 147
  2. Birkinshaw, M., Hughes, J. P., & Arnaud, K. A. 1991, ApJ, 379, 466
  3. Bonamente, M., Joy, M., LaRoque, S. J., Carlstrom, J. E., Nagai, D., & Marrone, D. P. 2008, ApJ, 675, 106
  4. Bonamente, M., Joy, M. K., Carlstrom, J. E., Reese, E. D., & LaRoque, S. J. 2004, ApJ, 614, 56
  5. Carlstrom, J. E., Holder, G. P., & Reese, E. D. 2002, ARA&A, 40, 643
  6. Carlstrom, J. et al. 2009, arXiv 0907.4445
  7. Eisenhardt, P. R. M. et al. 2008, ApJ, 684, 905
  8. Fowler, J. et al. 2007, Appl. Opt., 46, 3444
  9. Gladders, M. D., & Yee, H. K. C. 2000, AJ, 120, 2148
  10. —. 2005, ApJS, 157, 1
  11. Jee, M. J. et al. 2009, ApJ, 704, 672
  12. Lamer, G., Hoeft, M., Kohnert, J., Schwope, A., & Storm, J. 2008, A&A, 487, L33
  13. Markevitch, M. et al. 2003, ApJ, 583, 70
  14. Maughan, B. J., Jones, L. R., Ebeling, H., & Scharf, C. 2006, MNRAS, 365, 509
  15. Motl, P. M., Hallman, E. J., Burns, J. O., & Norman, M. L. 2005, ApJ, 623, L63
  16. Mroczkowski, T. et al. 2009, ApJ, 694, 1034
  17. Muchovej, S. et al. 2007, ApJ, 663, 708
  18. Mullis, C. R., Rosati, P., Lamer, G., Böhringer, H., Schwope, A., Schuecker, P., & Fassbender, R. 2005, ApJ, 623, L85
  19. Muzzin, A. et al. 2009, ApJ, 698, 1934
  20. Nagai, D., Vikhlinin, A., & Kravtsov, A. V. 2007, ApJ, 655, 98
  21. Nevalainen, J., Markevitch, M., & Lumb, D. 2005, ApJ, 629, 172
  22. Perlman, E. S., Horner, D. J., Jones, L. R., Scharf, C. A., Ebeling, H., Wegner, G., & Malkan, M. 2002, ApJS, 140, 265
  23. Rosati, P., Stanford, S. A., Eisenhardt, P. R., Elston, R., Spinrad, H., Stern, D., & Dey, A. 1999, AJ, 118, 76
  24. Rosati, P. et al. 2004, AJ, 127, 230
  25. —. 2009, A&A, 508, 583
  26. Santos, J. S., Rosati, P., Tozzi, P., Böhringer, H., Ettori, S., & Bignamini, A. 2008, A&A, 483, 35
  27. Smith, R. K., Brickhouse, N. S., Liedahl, D. A., & Raymond, J. C. 2001, ApJ, 556, L91
  28. Snowden, S. L. et al. 1997, ApJ, 485, 125
  29. Stanford, S. A. et al. 2005, ApJ, 634, L129
  30. Stanford, S. A., Elston, R., Eisenhardt, P. R., Spinrad, H., Stern, D., & Dey, A. 1997, AJ, 114, 2232
  31. Stanford, S. A., Holden, B., Rosati, P., Eisenhardt, P. R., Stern, D., Squires, G., & Spinrad, H. 2002, AJ, 123, 619
  32. Stanford, S. A. et al. 2006, ApJ, 646, L13
  33. Sunyaev, R. A., & Zel’dovich, Y. B. 1972, Comments Astrophys. Space Phys., 4, 173
  34. Vanderlinde, K. et al. 2010, arXiv, 1003.0003
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