Managing Research Data: Gravitational Waves

The project which led to this report was funded by JISC in 2010–2011 as part of its ‘Managing Research Data’ programme, to examine the way in which Big Science data is managed, and produce any recommendations which may be appropriate. Big science data is different: it comes in large volumes, and it is shared and exploited in ways which may differ from other disciplines. This project has explored these differences using as a case-study Gravitational Wave data generated by the LSC, and has produced recommendations intended to be useful variously to JISC, the funding council (STFC) and the LSC community. In Sect. 1 we define what we mean by ‘big science’, describe the overall data culture there, laying stress on how it necessarily or contingently differs from other disciplines. In Sect. 2 we discuss the benefits of a formal data-preservation strategy, and the cases for open data and for well-preserved data that follow from that. This leads to our recommendations that, in essence, funders should adopt rather light-touch prescriptions regarding data preservation planning: normal data management practice, in the areas under study, corresponds to notably good practice in most other areas, so that the only change we suggest is to make this planning more formal, which makes it more easily auditable, and more amenable to constructive criticism. In Sect. 3 we briefly discuss the LIGO data management plan, and pull together whatever information is available on the estimation of digital preservation costs. The report is informed, throughout, by the OAIS reference model for an open archive. Some of the report’s findings and conclusions were summarised in [1]. See the document history on page 37

Baade's red sheet resolved into stars with HST in the Blue Compact Dwarf Galaxy VII Zw 403

HST WFPC2 observations of the nearby Blue Compact Dwarf Galaxy VII~Zw~403 (= UGC 6456) resolve single stars down to M$_I$$\approx$-2.5, deep enough to identify red giants. This population has a more uniform spatial distribution than the young main-sequence stars and supergiants, forming the structure known as "Baade's red sheet". We conclude that VII~Zw~403 is not a primeval galaxy.Comment: submitted to: ApJ Letter

Utilization of photon orbital angular momentum in the low-frequency radio domain

We show numerically that vector antenna arrays can generate radio beams which exhibit spin and orbital angular momentum characteristics similar to those of helical Laguerre-Gauss laser beams in paraxial optics. For low frequencies (< 1 GHz), digital techniques can be used to coherently measure the instantaneous, local field vectors and to manipulate them in software. This opens up for new types of experiments that go beyond those currently possible to perform in optics, for information-rich radio physics applications such as radio astronomy, and for novel wireless communication concepts.Comment: 4 pages, 5 figures. Changed title, identical to the paper published in PR

The LOFAR ling baseline snapshot calibrator survey

Aims:\ud An efficient means of locating calibrator sources for international LOw Frequency ARray (LOFAR) is developed and used to determine the average density of usable calibrator sources on the sky for subarcsecond observations at 140 MHz.\ud \ud Methods\ud We used the multi-beaming capability of LOFAR to conduct a fast and computationally inexpensive survey with the full international LOFAR array. Sources were preselected on the basis of 325 MHz arcminute-scale flux density using existing catalogues. By observing 30 different sources in each of the 12 sets of pointings per hour, we were able to inspect 630 sources in two hours to determine if they possess a sufficiently bright compact component to be usable as LOFAR delay calibrators.\ud \ud Results:\ud More than 40% of the observed sources are detected on multiple baselines between international stations and 86 are classified as satisfactory calibrators. We show that a flat low-frequency spectrum (from 74 to 325 MHz) is the best predictor of compactness at 140 MHz. We extrapolate from our sample to show that the sky density of calibrators that are sufficiently bright to calibrate dispersive and non-dispersive delays for the international LOFAR using existing methods is 1.0 per square degree.\ud \ud Conclusions:\ud The observed density of satisfactory delay calibrator sources means that observations with international LOFAR should be possible at virtually any point in the sky provided that a fast and efficient search, using the methodology described here, is conducted prior to the observation to identify the best calibrator

A Kinematic Link between Boxy Bulges, Stellar Bars, and Nuclear Activity in NGC 3079 & NGC 4388

We present direct kinematic evidence for bar streaming motions in two active galaxies with boxy stellar bulges. The Hawaii Imaging Fabry-Perot Interferometer was used on the Canada-France-Hawaii 3.6-m telescope and the University of Hawaii 2.2-m telescope to derive the two-dimensional velocity field of the line-emitting gas in the disks of the Sc galaxy NGC 3079 and the Sb galaxy NGC 4388. In contrast to previous work based on long-slit data, the detection of the bar potential from the Fabry-Perot data does not rely on the existence of inner Lindblad resonances or strong bar-induced shocks. Simple kinematic models which approximate the intrinsic gas orbits as nonintersecting, inclined elliptical annuli that conserve angular momentum characterize the observed velocity fields. Box-shaped bulges in both NGC 3079 and NGC 4388 are confirmed using new near-infrared images to reduce dust obscuration. Morphological analysis of starlight in these galaxies is combined with the gas kinematics derived from the Fabry-Perot spectra to test evolutionary models of stellar bars that involve transitory boxy bulges, and to quantify the importance of such bars in fueling active nuclei. Our data support the evolutionary bar models, but fail to prove convincingly that the stellar bars in NGC 3079 and NGC 4388 directly trigger or sustain the nuclear activity. (abridged)Comment: 31 pages, 18 figures, Latex, requires aaspp4.sty. Accepted for the Astronomical Journal (November issue

Constraining the magnetic field geometry of the millisecond pulsar PSRJ0030+0451 from joint radio, thermal X-ray, and γ-ray emission

Context. With the advent of multi-wavelength electromagnetic observations of neutron stars - spanning many decades in photon energies - from radio wavelengths up to X-rays and γ-rays, it has become possible to significantly constrain the geometry and the location of the associated emission regions. Aims. In this work, we use results from the modelling of thermal X-ray observations of PSR J0030+0451 from the Neutron Star Interior Composition Explorer (NICER) mission and phase-aligned radio and γ-ray pulse profiles to constrain the geometry of an off-centred dipole that is able to reproduce the light curves in these respective bands simultaneously. Methods. To this aim, we deduced a configuration with a simple dipole off-centred from the location of the centre of the thermal X-ray hot spots. We show that the geometry is compatible with independent constraints from radio and -ray pulsations only, leading to a fixed magnetic obliquity of α ≈ 75° and a line-of-sight inclination angle of ζ ≈ 54°. Results. We demonstrate that an off-centred dipole cannot be rejected by accounting for the thermal X-ray pulse profiles. Moreover, the crescent shape of one spot is interpreted as the consequence of a small-scale surface dipole on top of the large-scale off-centred dipole

The Recent Evolution of the Dwarf Starburst Galaxy NGC 625 from Hubble Space Telescope Imaging

New HST/WFPC2 imaging of the dwarf starburst galaxy NGC 625 is presented. These data, 80% complete to V and I magnitudes of 26.0 and 25.3, respectively, allow us to study the recent star formation history of NGC 625. We derive a tip of the red giant branch (TRGB) distance modulus of 27.95+/-0.07, corresponding to a distance of 3.89+/-0.22 Mpc, and a location on the far side of the Sculptor Group. NGC 625 has a well-defined radial stellar population gradient, evidenced by a central concentration of young MS stars and an RGB/AGB ratio that increases with galactocentric distance. The prominent AGB is very red, and RGB stars are detected far from the central star forming regions. Using H Alpha and H Beta narrow band imaging and previous optical spectroscopy we identify substantial and varying internal extinction (A_V = 0.0 to 0.6 mag) associated with the central active star formation regions. To better understand the effects of internal extinction on the analysis of young stellar populations, synthetic models are presented which, for the first time, examine and account for this effect. Using the luminous blue helium burning stars, we construct a simple model of the recent (< 100 Myr) star formation in which an elevated but declining star formation rate has been present over this entire period. This is at odds with the presence of spectroscopic W-R features in the major star formation region which imply a short duration (<= 5 Myr) for the recent starburst. This suggests that starbursts displaying W-R features are not necessarily all of a short duration. Finally, we speculate on the possible causes of the present burst of star formation in this apparently isolated galaxy, and compare it to other nearby, well-studied dwarf starburst systems.Comment: 56 pages, including 15 figures (2 in color). Scheduled to appear in AJ, December, 2003. Full-resolution version may be obtained at http://www.astro.umn.edu/~Cannon/n625.p

Jordan-Schwinger map, 3D harmonic oscillator constants of motion, and classical and quantum parameters characterizing electromagnetic wave polarization

In this work we introduce a generalization of the Jauch and Rohrlich quantum Stokes operators when the arrival direction from the source is unknown {\it a priori}. We define the generalized Stokes operators as the Jordan-Schwinger map of a triplet of harmonic oscillators with the Gell-Mann and Ne'eman SU(3) symmetry group matrices. We show that the elements of the Jordan-Schwinger map are the constants of motion of the three-dimensional isotropic harmonic oscillator. Also, we show that generalized Stokes Operators together with the Gell-Mann and Ne'eman matrices may be used to expand the polarization density matrix. By taking the expectation value of the Stokes operators in a three-mode coherent state of the electromagnetic field, we obtain the corresponding generalized classical Stokes parameters. Finally, by means of the constants of motion of the classical three-dimensional isotropic harmonic oscillator we describe the geometric properties of the polarization ellips

First results of electric field and density observations by Cluster EFW based on initial months of operation

International audienceHighlights are presented from studies of the electric field data from various regions along the Cluster orbit. They all point towards a very high coherence for phenomena recorded on four spacecraft that are separated by a few hundred kilometers for structures over the whole range of apparent frequencies from 1 mHz to 9 kHz. This presents completely new opportunities to study spatial-temporal plasma phenomena from the magnetosphere out to the solar wind. A new probe environment was constructed for the CLUSTER electric field experiment that now produces data of unprecedented quality. Determination of plasma flow in the solar wind is an example of the capability of the instrument