Alexander S. Szalay

Publications (475) View all

• Source

  Available from: Werner Zeilinger

  Article: SPACE: the spectroscopic all-sky cosmic explorer

  A. Cimatti, M. Robberto, C. Baugh, S. V. W. Beckwith, R. Content, E. Daddi, G. De Lucia, B. Garilli, L. Guzzo, G. Kauffmann, [......], F. Walter, M. Ward, R. White, S. White, E. Wright, R. Wyse, G. Zamorani, A. Zacchei, W. W. Zeilinger, F. Zerbi
  [show abstract] [hide abstract]
  ABSTRACT: We describe the scientific motivations, the mission concept and the instrumentation of SPACE, a class-M mission proposed for concept study at the first call of the ESA Cosmic-Vision 2015–2025 planning cycle. SPACEaims to produce the largest three-dimensional evolutionary map of the Universe over the past 10billion years by taking near-IR spectra and measuring redshifts for more than half a billion galaxies at 0 < z < 2 down to AB~23 over 3πsr of the sky. In addition, SPACEwill also target a smaller sky field, performing a deep spectroscopic survey of millions of galaxies to AB~26 and at 2 < z < 10 +. These goals are unreachable with ground-based observations due to the ≈500 times higher sky background (see e.g. Aldering, LBNL report number LBNL-51157, 2001). To achieve the main science objectives, SPACEwill use a 1.5m diameter Ritchey-Chretien telescope equipped with a set of arrays of Digital Micro-mirror Devices covering a total field of view of 0.4 deg2, and will perform large-multiplexing multi-object spectroscopy (e.g. ≈6000 targets per pointing) at a spectral resolution of R~400 as well as diffraction-limited imaging with continuous coverage from 0.8 to 1.8μm. Owing to the depth, redshift range, volume coverage and quality of its spectra, SPACEwill reveal with unique sensitivity most of the fundamental cosmological signatures, including the power spectrum of density fluctuations and its turnover. SPACEwill also place high accuracy constraints on the dark energy equation of state parameter and its evolution by measuring the baryonic acoustic oscillations imprinted when matter and radiation decoupled, the distance-luminosity relation of cosmological supernovae, the evolution of the cosmic expansion rate, the growth rate of cosmic large-scale structure, and high-z galaxy clusters. The datasets from the SPACEmission will represent a long lasting legacy for the whole astronomical community whose data will be mined for many years to come.
  Experimental Astronomy 04/2012; 23(1):39-66. · 1.82 Impact Factor
• Source

  Available from: ac.uk

  Article: Extreme Data-Intensive Scientific Computing

  A. Szalay
  [show abstract] [hide abstract]
  ABSTRACT: Scientific computing increasingly involves massive data; in astronomy, observations and numerical simulations are on the verge of generating petabytes. This new, data-centric computing requires a new look at computing architectures and strategies. Using Amdahl's law to characterize architectures and workloads, it's possible to use existing commodity parts to build systems that approach an ideal Amdahl machine.
  Computing in Science and Engineering 01/2012; · 1.42 Impact Factor
• Source

  Available from: unam.mx

  Conference Proceeding: I/O streaming evaluation of batch queries for data-intensive computational turbulence

  K. Kanov, E. Perlman, R. Burns, Y. Ahmad, A. Szalay
  [show abstract] [hide abstract]
  ABSTRACT: We describe a method for evaluating computational turbulence queries, including Lagrange Polynomial interpolation, based on partial sums that allows the underlying data to be accessed in any order and in parts. We exploit these properties to stream data from disk in a single pass and concurrently evaluate batch queries. The combination of sequential I/O and data sharing improves performance by an order of magnitude when compared with direct evaluation of each query. The technique also supports distributed evaluation of queries in a database cluster, assembling the partial sums from each node at the query mediator. Interpolation is fundamental to computational turbulence, over 95% of queries use these routines, and the partial sums method al- lows the JHU Turbulence Database Cluster to realize scale and throughput for our scientists' data-intensive workloads.
  High Performance Computing, Networking, Storage and Analysis (SC), 2011 International Conference for; 12/2011
• Source

  Available from: Alexander S. Szalay

  Article: Galaxy Zoo: building the low-mass end of the red sequence with local post-starburst galaxies

  O. Ivy Wong, K. Schawinski, S. Kaviraj, K. L. Masters, R. C. Nichol, C. Lintott, W. C. Keel, D. Darg, S. P. Bamford, D. Andreescu, P. Murray, M. J. Raddick, A. Szalay, D Thomas, J. Vandenberg
  [show abstract] [hide abstract]
  ABSTRACT: We present a study of local post-starburst galaxies (PSGs) using the photometric and spectroscopic observations from the Sloan Digital Sky Survey (SDSS) and the results from the Galaxy Zoo project. We find that the majority of our local PSG population have neither early- nor late- type morphologies but occupy a well-defined space within the colour-stellar mass diagram, most notably, the low-mass end of the "green valley" below the transition mass thought to be the mass division between low-mass star-forming galaxies and high-mass passively-evolving bulge-dominated galaxies. Our analysis suggests that it is likely that a local PSG will quickly transform into "red", low-mass early-type galaxies as the stellar morphologies of the "green" PSGs largely resemble that of the early-type galaxies within the same mass range. We propose that the current population of PSGs represents a population of galaxies which is rapidly transitioning between the star-forming and the passively-evolving phases. Subsequently, these PSGs will contribute towards the build-up of the low-mass end of the "red sequence" once the current population of young stars fade and stars are no longer being formed. These results are consistent with the idea of "downsizing" where the build-up of smaller galaxies occurs at later epochs.
  11/2011;
• Source

  Available from: storageconference.org

  Conference Proceeding: Performance modeling and analysis of flash-based storage devices

  H.H. Huang, Shan Li, A. Szalay, A. Terzis
  [show abstract] [hide abstract]
  ABSTRACT: Flash-based solid-state drives (SSDs) will become key components in future storage systems. An accurate performance model will not only help understand the state-of-the-art of SSDs, but also provide the research tools for exploring the design space of such storage systems. Although over the years many performance models were developed for hard drives, the architectural differences between two device families prevent these models from being effective for SSDs. The hard drive performance models cannot account for several unique characteristics of SSDs, e.g., low latency, slow update, and expensive block-level erase. In this paper, we utilize the black-box modeling approach to analyze and evaluate SSD performance, including latency, bandwidth, and throughput, as it requires minimal a priori information about the storage devices. We construct the black-box models, using both synthetic workloads and real-world traces, on three SSDs, as well as an SSD RAID. We find that, while the black-box approach may produce less desirable performance predictions for hard disks, a black-box SSD model with a comprehensive set of workload characteristics can produce accurate predictions for latency, bandwidth, and throughput with small errors.
  Mass Storage Systems and Technologies (MSST), 2011 IEEE 27th Symposium on; 06/2011