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Morgan A.N.,University of California at Berkeley | Perley D.A.,California Institute of Technology | Cenko S.B.,University of California at Berkeley | Bloom J.S.,University of California at Berkeley | And 17 more authors.
Monthly Notices of the Royal Astronomical Society | Year: 2014

We present broad-band observations and analysis of Swift gamma-ray burst (GRB) 120119A. Our early-time afterglow detections began under 15 s after the burst in the host frame (redshift z = 1.73), and they yield constraints on the burst energetics and local environment. Late-time afterglow observations of the burst show evidence for a moderate column of dust (AV ≈ 1.1mag) similar to, but statistically distinct from, dust seen along Small Magellanic Cloud sightlines. Deep late-time observations reveal a dusty, rapidly star-forming host galaxy. Most notably, our early-time observations exhibit a significant red-to-blue colour change in the first ~200 s after the trigger at levels heretofore unseen in GRB afterglows. This colour change, which is coincident with the final phases of the prompt emission, is a hallmark prediction of the photodestruction of dust in GRB afterglows. We test whether dust-destruction signatures are significantly distinct from other sources of colour change, namely a change in the intrinsic spectral index β. We find that a time-varying power-law spectrum alone cannot adequately describe the observed colour change, and allowing for dust destruction (via a time-varying AV) significantly improves the fit. While not definitively ruling out other possibilities, this event provides the best support yet for the direct detection of dust destruction in the local environment of a GRB. © 2014 The Authors Published by Oxford University Press on behalf of the Royal Astronomical Society. Source


Simpson F.,University of Edinburgh | James J.B.,Dark Cosmology Center | James J.B.,University of California at Berkeley | Heavens A.F.,University of Edinburgh | Heymans C.,University of Edinburgh
Physical Review Letters | Year: 2011

A large fraction of the information collected by cosmological surveys is simply discarded to avoid length scales which are difficult to model theoretically. We introduce a new technique which enables the extraction of useful information from the bispectrum of galaxies well beyond the conventional limits of perturbation theory. Our results strongly suggest that this method increases the range of scales where the relation between the bispectrum and power spectrum in tree-level perturbation theory may be applied, from k max∼0.1 to ∼0.7hMpc -1. This leads to correspondingly large improvements in the determination of galaxy bias. Since the clipped matter power spectrum closely follows the linear power spectrum, there is the potential to use this technique to probe the growth rate of linear perturbations and confront theories of modified gravity with observation. © 2011 American Physical Society. Source


Konig S.,Dark Cosmology Center | Konig S.,University of Cologne | Garcia-Marin M.,University of Cologne | Eckart A.,University of Cologne | And 3 more authors.
Astrophysical Journal | Year: 2012

For the first time, we study the eastern nucleus in greater detail and search for the more extended emission in the molecular gas in different CO line transitions of the famous ultraluminous infrared galaxy (ULIRG) Arp 220. Furthermore, we present a model of the merger in Arp 220 on large scales with the help of the CO data and an optical and near-infrared composite Hubble Space Telescope image of the prototypical ULIRG. Using the Plateau de Bure interferometer (PdBI), we obtained CO(2-1) and (1-0) data at wavelengths of 1 and 3mm in 1994, 1996, 1997, and 2006 at different beam sizes and spatial resolutions. The simulations of the merger in Arp 220 were performed with the Identikit modeling tool. The model parameters that describe the galaxy merger best give a mass ratio of 1:2 and result in a merger of 6 × 10 8yr. The low-resolution CO(1-0) PdBI observations suggest that there are indications for emission 10″ toward the south, as well as to the north and to the west of the two nuclei. © 2012. The American Astronomical Society. All rights reserved.. Source


Penner K.,University of Arizona | Pope A.,National Optical Astronomy Observatory | Chapin E.L.,University of British Columbia | Greve T.R.,Max Planck Institute for Astronomy | And 14 more authors.
Monthly Notices of the Royal Astronomical Society | Year: 2011

We present a study of the cosmic infrared background, which is a measure of the dust-obscured activity in all galaxies in the Universe. We venture to isolate the galaxies responsible for the background at 1 mm; with spectroscopic and photometric redshifts we constrain the redshift distribution of these galaxies. We create a deep 1.16 mm map (σ∼ 0.5 mJy) by combining the AzTEC 1.1 mm and MAMBO 1.2 mm data sets in the Great Observatories Origins Deep Survey North (GOODS-N) region. This combined map contains 41 secure detections, 13 of which are new. By averaging the 1.16 mm flux densities of individually undetected galaxies with 24 μm flux densities >25 μJy, we resolve 31-45 per cent of the 1.16 mm background. Repeating our analysis on the SCUBA 850 μm map, we resolve a higher percentage (40-64 per cent) of the 850 μm background. A majority of the background resolved (attributed to individual galaxies) at both wavelengths comes from galaxies at z > 1.3. If the ratio of the resolved submillimetre to millimetre background is applied to a reasonable scenario for the origins of the unresolved submillimetre background, 60-88 per cent of the total 1.16 mm background comes from galaxies at z > 1.3. © 2010 The Authors. Journal compilation © 2010 RAS. Source


Scrimgeour M.I.,University of Western Australia | Davis T.,University of Queensland | Blake C.,Swinburne University of Technology | James J.B.,Dark Cosmology Center | And 26 more authors.
Monthly Notices of the Royal Astronomical Society | Year: 2012

We have made the largest volume measurement to date of the transition to large-scale homogeneity in the distribution of galaxies. We use the WiggleZ survey, a spectroscopic survey of over 200000 blue galaxies in a cosmic volume of ∼1h -3Gpc 3. A new method of defining the 'homogeneity scale' is presented, which is more robust than methods previously used in the literature, and which can be easily compared between different surveys. Due to the large cosmic depth of WiggleZ (up to z = 1), we are able to make the first measurement of the transition to homogeneity over a range of cosmic epochs. The mean number of galaxies N(< r) in spheres of comoving radius r is proportional to r 3 within 1per cent, or equivalently the fractal dimension of the sample is within 1per cent of D 2 = 3, at radii larger than 71 ± 8h -1Mpc at z ∼ 0.2, 70 ± 5h -1Mpc at z ∼ 0.4, 81 ± 5h -1Mpc at z ∼ 0.6 and 75 ± 4h -1Mpc at z ∼ 0.8. We demonstrate the robustness of our results against selection function effects, using a Λ cold dark matter (ΛCDM) N-body simulation and a suite of inhomogeneous fractal distributions. The results are in excellent agreement with both the ΛCDM N-body simulation and an analytical ΛCDM prediction. We can exclude a fractal distribution with fractal dimension below D 2 = 2.97 on scales from ∼80h -1Mpc up to the largest scales probed by our measurement, ∼300 h -1Mpc, at 99.99per cent confidence. © 2012 The Authors Monthly Notices of the Royal Astronomical Society © 2012 RAS. Source

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