Y. Omori

Superluminous supernovae at redshifts of 2.05 and 3.90

A rare class of ‘superluminous’ supernovae that are about ten or more times more luminous at their peaks than other types of luminous supernova has recently been found at low to intermediate redshifts. A small subset of these events have luminosities that evolve slowly and result in radiated energies of up to about 1051 ergs. Therefore, they are probably examples of ‘pair-instability’ or ‘pulsational pair-instability’ supernovae with estimated progenitor masses of 100 to 250 times that of the Sun. These events are exceedingly rare at low redshift, but are expected to be more common at high redshift because the mass distribution of the earliest stars was probably skewed to high values. Here we report the detection of two superluminous supernovae, at redshifts of 2.05 and 3.90, that have slowly evolving light curves. We estimate the rate of events at redshifts of 2 and 4 to be approximately ten times higher than the rate at low redshift. The extreme luminosities of superluminous supernovae extend the redshift limit for supernova detection using present technology, previously 2.36 (ref. 8), and provide a way of investigating the deaths of the first generation of stars to form after the Big Bang.

Cross-correlation of gravitational lensing from DES Science Verification data with SPT and Planck lensing

We measure the cross-correlation between weak lensing of galaxy images and of the cosmic microwave background (CMB). The effects of gravitational lensing on different sources will be correlated if the lensing is caused by the same mass fluctuations. We use galaxy shape measurements from 139 deg(2) of the Dark Energy Survey (DES) Science Verification data and overlapping CMB lensing from the South Pole Telescope (SPT) and Planck. The DES source galaxies have a median redshift of z(med) similar to 0.7, while the CMB lensing kernel is broad and peaks at z similar to 2. The resulting cross-correlation is maximally sensitive to mass fluctuations at z similar to 0.44. Assuming the Planck 2015 best-fitting cosmology, the amplitude of the DESxSPT cross-power is found to be A(SPT) = 0.88 +/- 0.30 and that from DESxPlanck to be A(Planck) = 0.86 +/- 0.39, where A = 1 corresponds to the theoretical prediction. These are consistent with the expected signal and correspond to significances of 2.9 sigma and 2.2 sigma, respectively. We demonstrate that our results are robust to a number of important systematic effects including the shear measurement method, estimator choice, photo-z uncertainty and CMB lensing systematics. We calculate a value of A = 1.08 +/- 0.36 for DESxSPT when we correct the observations with a simple intrinsic alignment model. With three measurements of this cross-correlation now existing in the literature, there is not yet reliable evidence for any deviation from the expected LCDM level of cross-correlation. We provide forecasts for the expected signal-to-noise ratio of the combination of the five-year DES survey and SPT-3G.

A comparison of cosmological parameters determined from CMB Temperature Power Spectra from the South Pole Telescope and the Planck Satellite

U.S. Department of Energy [DE-AC02-06CH11357]; Canadian Institute for Advanced Research; U.S. Department of Energy, Office of Science, Office of High Energy Physics; National Science Foundation [PLR-1248097]; Kavli Foundation; NSF Physics Frontier Center [PHY-1125897]; Australian Research Council Future Fellowship [FT150100074]; Fermi Research Alliance, LLC [DE-AC02-07CH11359]; National Sciences and Engineering Research Council of Canada; Gordon and Betty Moore Foundation grant [GBMF 947]; Canada Research Chairs program

A submillimetre-bright z ∼ 3 overdensity behind a z ∼ 1 supercluster revealed by SCUBA-2 and Herschel

We present a wide-field (30 ′ diameter) 850µm SCUBA-2 map of the spectacular threecomponent merging supercluster, RCS 231953+00, at z = 0.9. The brightest submillimetre galaxy (SMG) in the field ( S850 ≈ 12 mJy) is within 30 ′′ of one of the cluster cores (RCS 2319‐C), and is likely to be a more distant, lensed galaxy. Interestingly, the wider field around RCS 2319-C reveals a local overdensity of SMGs, e xceeding the average source density by a factor of 4.5, with a < 1% chance of being found in a random field. Utilizing Herschel-SPIRE observations, we find three of these SMGs have similar submillimetre colours. We fit their observed 250‐850 µm spectral energy distributions to estimate their redshift, yielding 2.5 < z < 3.5, and calculate prodigious star formation rates (SFRs) ranging from 500−2500M⊙ yr −1 . We speculate that these galaxies are either lensed SMGs, or signpost a physical structure at z ≈ 3: a ‘protocluster’ inhabited by young galaxies in a rapid phase of growth, destined to form the core of a massive galaxy cluster by z = 0.

A Comparison of Maps and Power Spectra Determined from South Pole Telescope and Planck Data

We study the consistency of 150 GHz data from the South Pole Telescope (SPT) and 143 GHz data from the Planck satellite over the patch of sky covered by the SPT-SZ survey. We first visually compare the maps and find that the residuals appear consistent with noise after accounting for differences in angular resolution and filtering. We then calculate (1) the cross-spectrum between two independent halves of SPT data, (2) the cross-spectrum between two independent halves of Planck data, and (3) the cross-spectrum between SPT and Planck data. We find that the three cross-spectra are well fit (PTE = 0.30) by the null hypothesis in which both experiments have measured the same sky map up to a single free calibration parameter—i.e., we find no evidence for systematic errors in either data set. As a by-product, we improve the precision of the SPT calibration by nearly an order of magnitude, from 2.6% to 0.3% in power. Finally, we compare all three cross-spectra to the full-sky Planck power spectrum and find marginal evidence for differences between the power spectra from the SPT-SZ footprint and the full sky. We model these differences as a power law in spherical harmonic multipole number. The best-fit value of this tilt is consistent among the three cross-spectra in the SPT-SZ footprint, implying that the source of this tilt is a sample variance fluctuation in the SPT-SZ region relative to the full sky. The consistency of cosmological parameters derived from these data sets is discussed in a companion paper.

Constraints on Cosmological Parameters from the Angular Power Spectrum of a Combined 2500 deg

We report constraints on cosmological parameters from the angular power spectrum of a cosmic microwave background (CMB) gravitational lensing potential map created using temperature data from 2500 deg2 of South Pole Telescope (SPT) data supplemented with data from Planck in the same sky region, with the statistical power in the combined map primarily from the SPT data. We fit the lensing power spectrum to a model including cold dark matter and a cosmological constant (ΛCDM), and to models with single-parameter extensions to ΛCDM. We find constraints that are comparable to and consistent with those found using the full-sky Planck CMB lensing data, e.g., σ_8 Ω^(0.25)_m = 0.598 ± 0.024 from the lensing data alone with weak priors placed on other parameters. Combining with primary CMB data, we explore single-parameter extensions to ΛCDM. We find Ω_k = -0.012^(+0.021)_(-0.023) or M_ν < 0.70 eV at 95% confidence, in good agreement with results including the lensing potential as measured by Planck. We include two parameters that scale the effect of lensing on the CMB: A_L, which scales the lensing power spectrum in both the lens reconstruction power and in the smearing of the acoustic peaks, and A^(oo), which scales only the amplitude of the lensing reconstruction power spectrum. We find A^(oo) x A_L = 1.01 ± 0.08 for the lensing map made from combined SPT and Planck data, indicating that the amount of lensing is in excellent agreement with expectations from the observed CMB angular power spectrum when not including the information from smearing of the acoustic peaks.

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We present the discovery of three super-luminous supernovae (SLSNe) at z = 2 - 4 as part of our survey to detect ultraviolet-luminous supernova at z > 2. SLSNe are ≥10 times more luminous than normal supernova types, reaching peak luminosities of ≳10^(44) erg s^(−1). A small subset of SLSNe (type SLSN-R) exhibit a slow evolution, and thus enormous integrated energies (≳10^(51) erg), consistent with the radiative decay of several solar masses of 56 Ni. SLSN-R are believed to be the deaths of very massive stars, ∼140 - 260 M_⊙, that are theorized to result in pair-instability supernovae. Two of the high redshift SLSNe presented here are consistent with the behavior of SLSN-R out to the extent in which their light curves are sampled, with the third event being consistent with the more rapid fade of the type II-L SLSN SN 2008es at z = 0.205. SLSNe are extremely rare locally but are expected to have been more common in the early Universe and as members of the first generation of stars to form after the Big Bang, the Population III stars. The high intrinsic luminosity of SLSNe and their detectability using our image-stacking technique out to z ∼ 6 provide the first viable route to detect and study the deaths of massive Population III stars which are expected to form in pristine gas at redshifts as low as z ∼ 2.