The massive cluster MACSJ1149.5+2223(z = 0.544) displays five very large lensed images of a well-resolved spiral galaxy at z
spect = 1.491. It is within one of these images that the first example of ...a multiply lensed supernova (SN) has been detected recently as part of the Grism Lens-Amplified Survey from Space. The depth of this data also reveals many H ii regions within the lensed spiral galaxy which we identify between the five counter-images. Here, we expand the capability of our free-form method to incorporate these H ii regions locally, with other reliable lensed galaxies added for a global solution. This improved accuracy allows us to estimate when the Refsdal SN will appear within the other lensed images of the spiral galaxy to an accuracy of ∼7 per cent. We predict this SN will reappear in one of the counter-images (RA = 11:49:36.025, Dec. = +22:23:48.11, J2000) and on 2015 November 1 (with an estimated error of ±25 d) it will be at the same phase as it was when it was originally discovered, offering a unique opportunity to study the early phases of this SN and to examine the consistency of the mass model and the cosmological model that have an impact on the time delay prediction.
Strong size and internal density evolution of early-type galaxies between image and the present has been reported by several authors. Here we analyze samples of nearby and distant galaxies with ...dynamically measured masses in order to confirm the previous, model-dependent results and constrain the uncertainties that may play a role. Velocity dispersion ( capital sigma ) measurements are taken from the literature for 50 morphologically selected image field and cluster early-type galaxies with typical masses image. Sizes are determined with Advanced Camera for Surveys imaging. We compare the distant sample with a large sample of nearby early-type galaxies extracted from the Sloan Digital Sky Survey for which we determine sizes, masses, and densities in a consistent manner, using simulations to quantify systematic differences between the size measurements of nearby and distant galaxies. We find a highly significant difference between the image distributions of the nearby and distant samples, regardless of sample selection effects. The implied evolution in image at fixed mass between image and the present is a factor of image. This is in qualitative agreement with semianalytic models; however, the observed evolution is much faster than the predicted evolution. Our results reinforce and are quantitatively consistent with previous, photometric studies that found size evolution of up to a factor of 5 since image. A combination of structural evolution of individual galaxies through the accretion of companions and the continuous formation of early-type galaxies through increasingly gas-poor mergers is one plausible explanation of the observations.
We examine the latest data on the cluster MACSJ0717.5+3745 from the Hubble Frontier Fields campaign. The critically lensed area is the largest known of any lens and very irregular making it a ...challenge for parametric modelling. Using our free-form method we obtain an accurate solution, identify here many new sets of multiple images, doubling the number of constraints and improving the reconstruction of the dark matter distribution. Our reconstructed mass map shows several distinct central substructures with shallow density profiles, clarifying earlier work and defining well the relation between the dark matter distribution and the luminous and X-ray peaks within the critically lensed region. Using our free-form method, we are able to meaningfully subtract the mass contribution from cluster members to the deflection field to trace the smoothly distributed cluster dark matter distribution. We find four distinct concentrations, three of which are coincident with the luminous matter. The fourth peak has a significant offset from both the closest luminous and X-ray peaks. These findings, together with dynamical data from the motions of galaxies and gas will be important for uncovering the potentially important implications of this extremely massive and intriguing system.
We report on the results of Hubble Space Telescope optical and UV imaging, Spitzer mid-IR photometry, and optical spectroscopy of a sample of 30 low-redshift (z ~ 0.1 to 0.3) galaxies chosen from the ...Sloan Digital Sky Survey and Galaxy Evolution Explorer surveys to be accurate local analogs of the high-redshift Lyman break galaxies. The Lyman break analogs (LBAs) are similar in stellar mass, metallicity, dust extinction, star formation rate (SFR), physical size, and gas velocity dispersion, thus enabling a detailed investigation of many processes that are important in star-forming galaxies at high redshift. The main optical emission-line properties of LBAs, including evidence for outflows, are also similar to those typically found at high redshift. This indicates that the conditions in their interstellar medium are comparable. In the UV, LBAs are characterized by complexes of massive clumps of star formation, while in the optical they most often show evidence for (post-)mergers and interactions. In six cases, we find a single extremely massive (up to several X109 M ) compact (radius ~102 pc) dominant central object (DCO). The DCOs are preferentially found in LBAs with the highest mid-IR luminosities (L 24 Delta *mm = 1010.3-1011.2 L ) and correspondingly high SFRs (15-100 M yr-1). We show that the massive star-forming clumps (including the DCOs) have masses much larger than the nuclear super star clusters seen in normal late-type galaxies. However, the DCOs do have masses, sizes, and densities similar to the excess light/central cusps seen in typical elliptical galaxies with masses similar to the LBA galaxies. We suggest that the DCOs form in the present-day examples of the dissipative mergers at high redshift that are believed to have produced the central cusps in local ellipticals (consistent with the disturbed optical morphologies of the LBAs). More generally, the properties of the LBAs are consistent with the idea that instabilities in a gas-rich disk lead to very massive star-forming clumps that eventually coalesce to form a spheroid. Finally, we comment on the apparent lack of energetically significant active galactic nuclei in the DCOs. We speculate that the DCOs are too young at present to grow a supermassive black hole because they are still in a supernova-dominated outflow phase (age less than 50 Myr).
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 ) × 10 8 M , and was formed at z = 13.2 − 1.6 + 1.9 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 10 deeper than the parallel fields.
We apply detailed observations of the color-magnitude relation (CMR) with the Advanced Camera for Surveys on the Hubble Space Telescope to study galaxy evolution in eight clusters at z 1. The ...early-type red sequence is well defined and elliptical and lenticular galaxies lie on similar CMRs. We analyze CMR parameters-scatter, slope, and zero point-as a function of redshift, galaxy properties and cluster mass. For bright galaxies (MB < -21 mag), the CMR scatter of the elliptical population in cluster cores is smaller than that of the S0 population, although the two become similar at faint magnitudes (MB > - 21 mag). While the bright S0 population consistently shows larger scatter than the ellipticals, the scatter of the latter increases in the peripheral cluster regions. If we interpret these results as due to age differences, bright elliptical galaxies in cluster cores are, on average, older than S0 galaxies and peripheral elliptical galaxies (by about 0.5 Gyr, using a simple, single-burst solar metallicity stellar population model). The CMR zero point, slope, and scatter in the (U - B) z = 0 rest-frame show no significant evolution out to redshift z 1.3 or significant dependence on cluster mass. Two of our clusters display CMR zero points that are redder (by 2 sigma ) than the average (U - B) z = 0 of our sample. We also analyze the fraction of morphological early-type and late-type galaxies on the red sequence. We find that, while in the majority of the clusters most (80% to 90%) of the CMR population is composed of early-type galaxies, in the highest-redshift, low-mass cluster of our sample, the CMR late-type/early-type fractions are similar (50%), with most of the late-type population composed of galaxies classified as S0/a. This trend is not correlated with the cluster's X-ray luminosity, or with its velocity dispersion, and could be a real evolution with redshift.
Hubble Space Telescope images of the galaxy cluster A2261, obtained as part of the Cluster Lensing And Supernova survey with Hubble, show that the brightest galaxy in the cluster, A2261-BCG, has the ...largest core yet detected in any galaxy. The cusp radius of A2261-BCG is 3.2 kpc, twice as big as the next largest core known, and ~3x bigger than those typically seen in the most luminous brightest cluster galaxies. The morphology of the core in A2261-BCG is also unusual, having a completely flat interior surface brightness profile, rather than the typical shallow cusp rising into the center. This implies that the galaxy has a core with constant or even centrally decreasing stellar density. Interpretation of the core as an end product of the "scouring" action of a binary supermassive black hole implies a total black hole mass ~10 super(10) M sub(middot in circle) from the extrapolation of most relationships between core structure and black hole mass. The core falls 1sigma above the cusp radius versus galaxy luminosity relation. Its large size in real terms, and the extremely large black hole mass required to generate it, raises the possibility that the core has been enlarged by additional processes, such as the ejection of the black holes that originally generated the core. The flat central stellar density profile is consistent with this hypothesis. The core is also displaced by 0.7 kpc from the center of the surrounding envelope, consistent with a local dynamical perturbation of the core.
Hubble Frontier Fields (HFF) imaging of the most powerful lensing clusters provides access to the most magnified distant galaxies. The challenge is to construct lens models capable of describing ...these complex massive, merging clusters so that individual lensed systems can be reliably identified and their intrinsic properties accurately derived. We apply the free-form lensing method (WSLAP+) to A2744, providing a model independent map of the cluster mass, magnification, and geometric distance estimates to multiply lensed sources. We solve simultaneously for a smooth cluster component on a pixel grid, together with local deflections by the cluster member galaxies. Combining model prediction with photometric redshift measurements, we correct and complete several systems recently claimed and identify four new systems totaling 65 images of 21 systems spanning a redshift range of 1.4 < z < 9.8. The reconstructed mass shows small enhancements in the directions where significant amounts of hot plasma can be seen in X-ray. We compare photometric redshifts with "geometric redshifts," finding a high level of self-consistency. We find excellent agreement between predicted and observed fluxes with a best-fit slope of 0.999 + or - 0.013 and an rms of ~0.25 mag, demonstrating that our magnification correction of the lensed background galaxies is very reliable. Intriguingly, few multiply lensed galaxies are detected beyond z Asymptotically = to 7.0, despite the high magnification and the limiting redshift of z Asymptotically = to 11.5 permitted by the HFF filters. With the additional HFF clusters, we can better examine the plausibility of any pronounced high-z deficit with potentially important implications for the reionization epoch and the nature of dark matter.
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