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تسجيل مستخدم جديدDiscovery of a Possible Splashback Feature in the Intracluster Light of MACS J1149.5+2223
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We present an analysis of the intracluster light in the Frontier Field Cluster MACS J1149.5+2223 (z=0.544), which combines new and archival Hubble WFC3/IR imaging to provide continuous radial coverage out to 2.8 Mpc from the brightest cluster galaxy. Employing careful treatment of potential systematic biases and using data at the largest radii to determine the background sky level, we reconstruct the surface brightness profile out to a radius of 2 Mpc. This radius is the largest to which the intracluster light (ICL) has been measured for an individual cluster. Within this radius, we measure a total luminosity of 1.5e13 Lsun for the brightest cluster galaxy plus ICL light. From the profile and its logarithmic slope, we identify the transition from the brightest cluster galaxy to ICL at r~70 kpc. Remarkably, we also detect an inflection in the profile centered in the 1.2-1.7 Mpc (0.37-0.52 r200m) radial bin, a signature of an infall caustic in the stellar distribution. Based upon the shape and strength of the feature, we interpret it as potentially being at the splashback radius, although the radius is smaller than theoretical predictions. If this is the splashback radius, then it is the first such detection in the ICL and the first detection of the splashback radius for an individual cluster. Similar analyses should be possible with the other Frontier Field clusters, and eventually with clusters from the Euclid and Roman missions.
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Radio halos and relics are Mpc-scale diffuse radio sources in galaxy clusters, with a steep spectral index $alpha>1$ ($Spropto u^{-alpha}$). It has been proposed that they arise from particle acceleration induced by turbulence and weak shocks, injec
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We search for high-redshift dropout galaxies behind the Hubble Frontier Fields (HFF) galaxy cluster MACS J1149.5+2223, a powerful cosmic lens that has revealed a number of unique objects in its field. Using the deep images from the Hubble and Spitzer
space telescopes, we find 11 galaxies at z>7 in the MACS J1149.5+2223 cluster field, and 11 in its parallel field. The high-redshift nature of the bright z~9.6 galaxy MACS1149-JD, previously reported by Zheng et al., is further supported by non-detection in the extremely deep optical images from the HFF campaign. With the new photometry, the best photometric redshift solution for MACS1149-JD reduces slightly to z=9.44 +/- 0.12. The young galaxy has an estimated stellar mass of (7 +/- 2)X10E8 Msun, and was formed at z=13.2 +1.9-1.6 when the universe was ~300 Myr old. Data available for the first four HFF clusters have already enabled us to find faint galaxies to an intrinsic magnitude of M(UV) ~ -15.5, approximately a factor of ten deeper than the parallel fields.
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ndidate. If time delays are pinned down, the remaining uncertainty arises from the mass distribution in the lens. In MACS J1149, the mass in the relevant lens plane region can be constrained by (i) many multiple images, (ii) the mass of the galaxy splitting S1-S4 (which, we show, is correlated with $H_0$), (iii) magnification of SX (also correlated with $H_0$), and (iv) prior assumptions on the mass distribution. Our goal is not to estimate $H_0$, but to understand its error budget, i.e., estimate uncertainties associated with each of these constraints. Using multiple image positions alone, yields very large uncertainty, despite the fact that the position of SX is recovered to within $!le!0.036$ (rms $!le!0.36$) by GRALE lens inversion. Fixing the mass of the galaxy that splits S1-S4 reduces $1sigma$ uncertainties to $sim 23%$, while fixing the magnification of SX yields $1sigma$ uncertainties of $32%$. We conclude that smaller uncertainties, of order few percent, are a consequence of imposing prior assumptions on the shapes of the galaxy and cluster mass distributions, which may or may not apply in a highly non-equilibrium environment of a merging cluster. We propose that if a measurement of $H_0$ is to be considered reliable, it must be supported by a wide range of lens inversion methods.
We analyse the Kormendy relations (KRs) of the two Frontier Fields clusters, Abell S1063, at z = 0.348, and MACS J1149.5+2223, at z = 0.542, exploiting very deep Hubble Space Telescope photometry and VLT/MUSE integral field spectroscopy. With this no
vel dataset, we are able to investigate how the KR parameters depend on the cluster galaxy sample selection and how this affects studies of galaxy evolution based on the KR. We define and compare four different galaxy samples according to: (a) Sersic indices: early-type (ETG), (b) visual inspection: ellipticals, (c) colours: red, (d) spectral properties: passive. The classification is performed for a complete sample of galaxies with m$_{textit{F814W}} le$ 22.5 ABmag (M$_{*}$ $gtrsim 10^{10.0}$ M$_{odot}$). To derive robust galaxy structural parameters, we use two methods: (1) an iterative estimate of structural parameters using images of increasing size, in order to deal with closely separated galaxies and (2) different background estimations, to deal with the Intracluster light contamination. The comparison between the KRs obtained from the different samples suggests that the sample selection could affect the estimate of the best-fitting KR parameters. The KR built with ETGs is fully consistent with the one obtained for ellipticals and passive. On the other hand, the KR slope built on the red sample is only marginally consistent with those obtained with the other samples. We also release the photometric catalogue with structural parameters for the galaxies included in the present analysis.
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