Hasil untuk "astro-ph.EP"

M. Huq, B. Fraass, P. Dunscombe et al.

M. Niyazi, M. Brada, A. Chalmers et al.

Yunsoo Ha, Juliane Mueller

Bi-fidelity stochastic optimization has gained increasing attention as an efficient approach to reduce computational costs by leveraging a low-fidelity (LF) model to optimize an expensive high-fidelity (HF) objective. In this paper, we propose ASTRO-BFDF, an adaptive sampling trust region method specifically designed for unconstrained bi-fidelity stochastic derivative-free optimization problems. In ASTRO-BFDF, the LF function serves two purposes: (i) to identify better iterates for the HF function when the optimization process indicates a high correlation between them, and (ii) to reduce the variance of the HF function estimates using bi-fidelity Monte Carlo (BFMC). The algorithm dynamically determines sample sizes while adaptively choosing between crude Monte Carlo and BFMC to balance the trade-off between optimization and sampling errors. We prove that the iterates generated by ASTRO-BFDF converge to the first-order stationary point almost surely. Additionally, we demonstrate the effectiveness of the proposed algorithm through numerical experiments on synthetic problems and simulation optimization problems involving discrete event systems.

A. Belikov, W. Vriend, G. Sikkema

From a simple text interface to a graphical user interfaces—Astro-WISE provides the user with a wide range of possibilities to interact with the information system according to the user’s tasks and use cases. We describe a general approach to the interfacing of a scientific information system. We use this approach to create a number of services, which allows the user to browse the data stored in the system, to process the data and to exchange the newly created images and catalogs with the users within the system and wider astronomical community. Reusability of interfaces and services is another important feature of our approach. It reduces the time and resources spent to interface other information systems created from Astro-WISE.

G. Kleijn, K. Kuijken, E. Valentijn et al.

The OmegaCAM wide-field optical imager is the sole instrument on the VLT Survey Telescope at ESO’s Paranal Observatory. The instrument, as well as the telescope, have been designed for surveys with very good, natural seeing-limited image quality over a 1 square degree field. OmegaCAM was commissioned in 2011 and has been observing three ESO Public Surveys in parallel since October 15, 2011. We use the Astro-WISE information system to monitor the calibration of the observatory and to produce the Kilo Degree Survey (KiDS). Here we describe the photometric monitoring procedures in Astro-WISE and give a first impression of OmegaCAM’s photometric behavior as a function of time. The long-term monitoring of the observatory goes hand in hand with the KiDS survey production in Astro-WISE. KiDS is observed under partially non-photometric conditions. Based on the first year of OmegaCAM operations it is expected that a ∼ 1–2 % photometric homogeneity will be achieved for KiDS.

D. Autiero, J. Äystö, A. Badertscher et al.

This document reports on a series of experimental and theoretical studies conducted to assess the astro-particle physics potential of three future large scale particle detectors proposed in Europe as next generation underground observatories. The proposed apparatuses employ three different and, to some extent, complementary detection techniques: GLACIER (liquid argon TPC), LENA (liquid scintillator) and MEMPHYS (water Cherenkov), based on the use of large mass of liquids as active detection media. The results of these studies are presented along with a critical discussion of the performance attainable by the three proposed approaches coupled to existing or planned underground laboratories, in relation to open and outstanding physics issues such as the search for matter instability, the detection of astrophysical neutrinos and geo-neutrinos and to the possible use of these detectors in future high intensity neutrino beams.

B. Fraass, L. Marks, T. Pawlicki

M. Tsao, M. Mehta, T. Whelan et al.

D. McHaffie, Rakesh R. Patel, Jarrod B. Adkison et al.

L. Baresi, Sam Guinea, M. Pistore et al.

T. Tanaka, R. Blandford, K. Doutsu et al.

The Soft Gamma-ray Detector (SGD) on board ASTRO-H (Japanese next high-energy astrophysics mission) is a Compton telescope with narrow fleld-of-view, which utilizes Compton kinematics to enhance its background rejection capabilities. It is realized as a hybrid semiconductor detector system which consists of silicon and CdTe (cadmium telluride) detectors. It can detect photons in a wide energy band (50-600 keV) at a background level 10 times better than that of the Suzaku Hard X-ray Detector, and is complimentary to the Hard X-ray Imager on board ASTRO-H with an energy coverage of 5-80 keV. Excellent energy resolution is the key feature of the SGD, allowing it to achieve good background rejection capability taking advantage of good angular resolution. An additional capability of the SGD, its ability to measure gamma-ray polarization, opens up a new window to study properties of gamma-ray emission processes. Here we describe the instrument design of the SGD, its expected performance, and its development status.

B. Silva, P. Maciel, E. Tavares et al.

C. Pearson, H. Matsuhara, H. Watarai et al.

We present basic observational strategies for ASTRO-F (also known as the Imaging Infra Red Surveyor (IRIS)) to be launched in 2004 by the Japanese Institute of Space and Astronautical Science (ISAS). We examine 2 survey scenarios, a deep ~1sq.deg. survey reaching sensitivities an order of magnitude below than the deepest surveys performed by ISO in the mid-IR, and a shallow \~18sq.deg mid-infrared (7-25um in 6 bands) covering an area greater than the entire area covered by all ISO mid-IR surveys. Using 2 cosmological models the number of galaxies predicted for each survey is calculated. The first model uses an enhancement of the pure luminosity evolution model of Pearson&Rowan-Robinson while the new models incorporate a strongly evolving ULIG component. For the deep survey, between 20,000-30,000 galaxies should be detected in the shortest wavebands and ~5000 in the longest (25um) band. The shallow survey would be expected to detect of the order of 100,000 - 150,000 sources.

S. Stroup, J. Cullen, B. Auge et al.

E. Horwitz, F. Vicini, E. L. Ziaja et al.

K. Yamaoka, M. Ohno, Y. Terada et al.

E. Valentijn, J. McFarland, J. Snigula et al.

The recent explosion of recorded digital data and its processed derivatives threatens to overwhelm researchers when analysing their experimental data or looking up data items in archives and file systems. While current hardware developments allow the acquisition, processing and storage of hundreds of terabytes of data at the cost of a modern sports car, the software systems to handle these data are lagging behind. This problem is very general and is well recognized by various scientific communities; several large projects have been initiated, e.g., DATAGRID/EGEE {http://www.eu-egee.org/} federates compute and storage power over the high-energy physical community, while the international astronomical community is building an Internet geared Virtual Observatory {http://www.euro-vo.org/pub/} (Padovani 2006) connecting archival data. These large projects either focus on a specific distribution aspect or aim to connect many sub-communities and have a relatively long trajectory for setting standards and a common layer. Here, we report first light of a very different solution (Valentijn & Kuijken 2004) to the problem initiated by a smaller astronomical IT community. It provides an abstract scientific information layer which integrates distributed scientific analysis with distributed processing and federated archiving and publishing. By designing new abstractions and mixing in old ones, a Science Information System with fully scalable cornerstones has been achieved, transforming data systems into knowledge systems. This break-through is facilitated by the full end-to-end linking of all dependent data items, which allows full backward chaining from the observer/researcher to the experiment. Key is the notion that information is intrinsic in nature and thus is the data acquired by a scientific experiment. The new abstraction is that software systems guide the user to that intrinsic information by forcing full backward and forward chaining in the data modelling.

J. Kruk, S. Durrance, G. Kriss et al.

B. Partridge, G. Greenstein

H. Kaneda, T. Onaka, T. Nakagawa et al.