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تسجيل مستخدم جديدIDCS J1426.5+3508: Sunyaev-Zeldovich Measurement of a Massive IR-selected Cluster at z=1.75
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We report 31 GHz CARMA observations of IDCS J1426.5+3508, an infrared-selected galaxy cluster at z = 1.75. A Sunyaev-Zeldovich decrement is detected towards this cluster, indicating a total mass of M200 = (4.3 +/- 1.1) x 10^{14} Msun in agreement with the approximate X-ray mass of ~5 x 10^{14} Msun. IDCS J1426.5+3508 is by far the most distant cluster yet detected via the Sunyaev-Zeldovich effect, and the most massive z >= 1.4 galaxy cluster found to date. Despite the mere ~1% probability of finding it in the 8.82 deg^2 IRAC Distant Cluster Survey, IDCS J1426.5+3508 is not completely unexpected in LCDM once the area of large, existing surveys is considered. IDCS J1426.5+3508 is, however, among the rarest, most extreme clusters ever discovered, and indeed is an evolutionary precursor to the most massive known clusters at all redshifts. We discuss how imminent, highly sensitive Sunyaev-Zeldovich experiments will complement infrared techniques for statistical studies of the formation of the most massive galaxy clusters in the z > 1.5 Universe, including potential precursors to IDCS J1426.5+3508.
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We report the discovery of an IR-selected massive galaxy cluster in the IRAC Distant Cluster Survey (IDCS). We present new data from the Hubble Space Telescope and the W. M. Keck Observatory that spectroscopically confirm IDCS J1426+3508 at z=1.75. M
oreover, the cluster is detected in archival Chandra data as an extended X-ray source, comprising 54 counts after the removal of point sources. We calculate an X-ray luminosity of L{0.5-2 keV} = (5.5 +/- 1.2) X 1e44 ergs/s within r = 60 arcsec (~1 Mpc diameter), which implies M_{200,L_x} = (5.6 +/- 1.6) X 1e14 Msun. IDCS J1426+3508 appears to be an exceptionally massive cluster for its redshift.
The galaxy cluster IDCS J1426.5+3508 at z = 1.75 is the most massive galaxy cluster yet discovered at z > 1.4 and the first cluster at this epoch for which the Sunyaev-ZelDovich effect has been observed. In this paper we report on the discovery with
HST imaging of a giant arc associated with this cluster. The curvature of the arc suggests that the lensing mass is nearly coincident with the brightest cluster galaxy, and the color is consistent with the arc being a star-forming galaxy. We compare the constraint on M200 based upon strong lensing with Sunyaev-ZelDovich results, finding that the two are consistent if the redshift of the arc is z > 3. Finally, we explore the cosmological implications of this system, considering the likelihood of the existence of a strongly lensing galaxy cluster at this epoch in an LCDM universe. While the existence of the cluster itself can potentially be accomodated if one considers the entire volume covered at this redshift by all current high-redshift cluster surveys, the existence of this strongly lensed galaxy greatly exacerbates the long-standing giant arc problem. For standard LCDM structure formation and observed background field galaxy counts this lens system should not exist. Specifically, there should be no giant arcs in the entire sky as bright in F814W as the observed arc for clusters at z geq 1.75, and only sim 0.3 as bright in F160W as the observed arc. If we relax the redshift constraint to consider all clusters at z geq 1.5, the expected number of giant arcs rises to sim15 in F160W, but the number of giant arcs of this brightness in F814W remains zero. These arc statistic results are independent of the mass of IDCS J1426.5+3508. We consider possible explanations for this discrepancy.
We present a weak lensing study of the galaxy cluster IDCS J1426.5+3508 at $z=1.75$, which is the highest redshift strong lensing cluster known and the most distant cluster for which a weak lensing analysis has been undertaken. Using F160W, F814W, an
d F606W observations with the Hubble Space Telescope, we detect tangential shear at $2sigma$ significance. Fitting a Navarro-Frenk-White mass profile to the shear with a theoretical median mass-concentration relation, we derive a mass $M_{200,mathrm{crit}}=2.3^{+2.1}_{-1.4}times10^{14}$ M$_{odot}$. This mass is consistent with previous mass estimates from the Sunyaev-Zeldovich (SZ) effect, X-ray, and strong lensing. The cluster lies on the local SZ-weak lensing mass scaling relation observed at low redshift, indicative of minimal evolution in this relation.
We present resolved thermodynamic profiles out to 500 kpc, about $r_{500}$, of the $z=1.75$ galaxy cluster IDCS J1426.5+3508 with 40 kpc resolution. Thanks to the combination of Sunyaev-Zeldovich and X-ray datasets, IDCS J1426.5+3508 becomes the most
distant cluster with resolved thermodynamic profiles. These are derived assuming a non-parametric pressure profile and a very flexible model for the electron density profile. The shape of the pressure profile is flatter than the universal pressure profile. The IDCS J1426.5+3508 temperature profile is increasing radially out to 500 kpc. To identify the possible future evolution of IDCS J1426.5+3508 , we compared it with its local descendants that numerical simulations show to be $0.65pm0.12$ dex more massive. We found no evolution at 30 kpc, indicating a fine tuning between cooling and heating at small radii. At $30<r<300$ kpc, our observations show that entropy and heat must be deposited with little net gas transfer, while at 500 kpc the gas need to be replaced by a large amount of cold, lower entropy gas, consistent with theoretical expectation of a filamentary gas stream, which brings low entropy gas to 500 kpc and energy at even smaller radii. At $r gtrsim 400$ kpc the polytropic index takes a low value, which indicates the presence of a large amount of non-thermal pressure. Our work also introduces a new definition of the evolutionary rate, which uses unscaled radii, unscaled thermodynamic quantities, and different masses at different redshifts to compare ancestors and descendants. It has the advantage of separating cluster evolution, dependence on mass, pseudo-evolution and returns a number with unique interpretation, unlike other definitions used in literature.
In this paper, we present resolved observations of the Sunyaev-Zeldovich (SZ) effect, obtained with the NIKA2 camera, towards the cluster of galaxies XLSSC102, a relatively low-mass system ($M_{500} sim 2 times 10^{14}$ M$_{odot}$) at $z = 0.97$ dete
cted from the XXL survey. We combine NIKA2 SZ data, XMM-Newton X-ray data, and Megacam optical data to explore, respectively, the spatial distribution of the gas electron pressure, the gas density, and the galaxies themselves. We find significant offsets between the X-ray peak, the SZ peak, the brightest cluster galaxy, and the peak of galaxy density. Additionally, the galaxy distribution and the gas present elongated morphologies. This is interpreted as the sign of a recent major merging event, which induced a local boost of the gas pressure towards the north of XLSSC102 and stripped the gas out of the galaxy group. The NIKA2 data are also combined with XXL data to construct the thermodynamic profiles of XLSSC102, obtaining relatively tight constraints up to about $sim r_{500}$, and revealing properties that are typical of disturbed systems. We also explore the impact of the cluster centre definition and the implication of local pressure substructure on the recovered profiles. Finally, we derive the global properties of XLSSC102 and compare them to those of high-mass-and-low-redshift systems, finding no strong evidence for non-standard evolution. We also use scaling relations to obtain alternative mass estimates from our profiles. The variation between these different mass estimates reflects the difficulty to accurately measure the mass of low-mass clusters at z$sim$1, especially with low signal-to-noise ratio (S/N) data and for a disturbed system. However, it also highlights the strength of resolved SZ observations alone and in combination with survey-like X-ray data.
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