An Active Instance-based Machine Learning method for Stellar Population Studies

We have developed a method for fast and accurate stellar population parameters determination in order to apply it to high resolution galaxy spectra. The method is based on an optimization technique that combines active learning with an instance-based machine learning algorithm. We tested the method with the retrieval of the star-formation history and dust content in "synthetic" galaxies with a wide range of S/N ratios. The "synthetic" galaxies where constructed using two different grids of high resolution theoretical population synthesis models. The results of our controlled experiment shows that our method can estimate with good speed and accuracy the parameters of the stellar populations that make up the galaxy even for very low S/N input. For a spectrum with S/N=5 the typical average deviation between the input and fitted spectrum is less than 10**{-5}. Additional improvements are achieved using prior knowledge.Comment: 14 pages, 25 figures, accepted by Monthly Notice

The case for metadata harvesting

Metadata harvesting is an increasingly popular model of interaction between the mutually autonomous parties of medium, medium-large federations of digital library services. With a harvesting protocol, in particular, resource descriptions locally available at each party can be served to remote applications for the implementation of federated services, such as resource discovery. This article offers a systematic explanation of the success of the model and its standard implementations in the context of current initiatives for national and international federations

Best Practices for Cataloging Streaming Media

Ce document est destiné à aider les catalogueurs québecois, belges… à créer des enregistrements pour les médias en continu selon les instructions de RDA pour MARC21. Il couvre à la fois la diffusion vidéo et audio, y compris ceux qui sont nés numériques, ainsi que ceux qui sont créés à partir d’une ressource existante dans un autre format, vidéo sur DVD ou vidéocassette. Son principal objectif est de « diffusion en continu » sur Internet en temps réel, plutôt que des ressources qui ne le sont pas

Final Recommendations of the Joint MLA/OLAC 33X/34X Task Group

The initial impetus for the formation of the task group came from Jay Weitz\u27s request for input from both our groups as he was working on the OCLC-MARC update 2017, particularly in reference to the 23 additions to the Genre/Form Code and Term Source Codes list (http://www.loc.gov/standards/sourcelist/genre-form.html). This request led to the realization that best practices of both groups varied in regard to MARC 344 and 347. It seemed like a good idea to have both groups discuss these same issues together. The group considered 3 issues: Inconsistent treatment of RDA and non-RDA terms in MARC 344 and 347 Consideration of consistent treatment of MARC 344 and 347 across formats Implementation of the new $2 source codes The deliverables include recommendations for each of the three issues and identification of next steps for activities involving the various best practices

Determination of Orbital Parameters of Interacting Galaxies Using Evolution Strategies

Abstract. In this work we apply Evolution Strategies as a method to find the orbital parameters of a pair of interacting galaxies using a single photometric image. Finding the orbital parameters that best match the image is done by posing it as an optimization problem and solving it using Evolution Strategies. Orbital parameters are estimated using position data from the image only, but in some cases is possible to use velocity data. As working directly with galaxies is unfeasible, we have used single simulations for modeling the system of galaxies, we present experimental results using synthetic data instead of a real image, showing that Evolution Strategies can determine orbital parameters of interacting galaxies very accurately

Determination of Initial Conditions of M81 Triplet Using Evolution Strategies

Abstract. In this work we present Evolution Strategies (ES) as an efficient method to approximate the initial conditions of the main interacting group of three galaxies in M81. The M81 group is one of the nearest groups of galaxies. Its biggest galaxy, M81, sits at the core of the group together with its two companions M82 and NGC3077. The interaction between these three galaxies is very well defined on an image taken in HI. In this first attempt we use nonself-gravitating simulations to approximate the initial conditions; even with that restriction our method reproduces the density distribution of the three galaxies with great precision. Results presented here show that ES is an ideally suited method to work in optimization problems in Astrophysics, where the solution is hard to find by common methods. In particular we argue that ES is a good method to find initial conditions of groups of interacting galaxies, where a large number of parameters need to be determined