Francois Ochsenbein

Automated Classification of ROSAT Sources Using Heterogeneous Multiwavelength Source Catalogs

We describe an online system for automated classification of X-ray sources, ClassX, and we present preliminary results of classification of the three major catalogs of ROSAT sources, ROSAT All-Sky Survey (RASS) Bright Source Catalog, RASS Faint Source Catalog, and WGACAT, into six class categories: stars, white dwarfs, X-ray binaries, galaxies, active galactic nuclei, and clusters of galaxies. ClassX is based on a machine-learning technology. It represents a system of classifiers, each classifier consisting of a considerable number of oblique decision trees. These trees are built as the classifier is trained to recognize various classes of objects using a training sample of sources of known object types. Each source is characterized by a preselected set of parameters, or attributes; the same set is then used as the classifier conducts classification of sources of unknown identity. The ClassX pipeline features an automatic search for X-ray source counterparts among heterogeneous data sets in online data archives using Virtual Observatory protocols; it retrieves from those archives all the attributes required by the selected classifier and inputs them to the classifier. The user input to ClassX is typically a file with target coordinates, optionally complemented with target IDs. The output contains the class name, attributes, and class probabilities for all classified targets. We discuss ways to characterize and assess the classifier quality and performance, and we present the respective validation procedures. On the basis of both internal validation and external verification, we conclude that the ClassX classifiers yield reasonable and reliable classifications for ROSAT sources and have the potential to broaden class representation significantly for rare object types.

Introduction to the CFHT Legacy Survey final release (CFHTLS T0007)

The Canada-France-Hawaii Telescope Legacy Survey (CFHTLS) is a high impact scientific program which will see its final official release open to the world in 2012. That release will seal the legacy aspect of the survey which has already produced a large collection of scientific articles with topics ranging from cosmology to the Solar system. The survey core science was focused on dark energy and dark matter: the full realization of the scientific potential of the data set gathered between 2003 and 2009 with the MegaCam wide-field imager mounted at the CFHT prime focus is almost complete with the Supernovae Legacy Survey (SNLS) team preparing its third and last release (SNLS5), and the CFHTLenS team planning the release based around the cosmic shear survey later this year. While the data processing center TERAPIX offered to the CFHTLS scientific community regular releases over the course of the survey in its data acquisition phase (T0001-T0006), the final release took three years to refine in order to produce a pristine data collection photometrically calibrated at better than the percent both internally and externally over the total survey surface of 155 square degrees in all five photometric bands (u*, g’, r’, i’, z’). This final release, called T0007, benefits from the various advances in photometric calibration MegaCam has benefited through the joint effort between SNLS and CFHT to calibrate MegaCam at levels unexplored for an optical wide-field imager. T0007 stacks and catalogs produced by TERAPIX will be made available to the world at CADC while the CDS will offer a full integration of the release in its VO tools from VizieR to Aladin. The photometric redshifts have been produced to be released in phase with the survey. This proceeding is a general introduction to the survey and aims at presenting its final release in broad terms.

Aladin: an Interactive Deep Sky Mapping Facility

Any astronomer, whether preparing observation runs or reducing data, requires access to information concerning the objects under investigation. Ideally the data should be from several wavelengths and should be as quantitative as possible. This leads to the concept of developing simultaneous interactive access to sky surveys, initially at optical wavelengths, and with state-of-the-art information systems for all field objects.

The local contribution to the microwave background radiation

The observed microwave background radiation(MBR)is commonly interpreted as the relic of an early hot universe,and its observed features(spectrum and anisotropy)are explained in terms of properties of the early universe.Here we describe a complementary,even possibly alternative,interpretation of MBR,first proposed in the early 20thcentury,and adapt it to modern observations.For example,the stellar Hipparcos data show that the energy density of starlight from the Milky Way,if suitably thermalized,yields a temperature of～2.81 K.This and other arguments given here strongly suggest that the origin of MBR may lie,at least in a very large part,in re-radiation of thermalized galactic starlight.The strengths and weaknesses of this alternative radical explanation are discussed.

Interoperability of archives in the VO

For the Virtual Observatory to connect archives around the globe, some standardization is needed. It is not necessary to rework the internal structure of each archive to a common standard, but standards for interfaces to archives and for exchange of data are important. We report on standardization work currently going on in the AVO and AstroGRID projects in the following areas: - Exchange formats for tabular data; - Semantic definitions for quantities in tabular data; - Identification of user and authorization to use resources; - Query interfaces to archives; - Catalogues of data resources. Discussion on standards is ongoing among all Virtual Observatory projects.

The VizieR system, a unified interface to astronomical catalogs

We present in this paper some aspects of the VizieR service, as an example of a database connecting to the largest set of astronomical catalogs. We especially emphasize here role of the metadata: how these are acquired from the catalog descriptions, and how they are stored in the system. The specification of relations or links between data are an important part of the metadata, and we use GLU (Generateur de Liens Uniformes=uniform link generator) expressions to describe the links to external databases or services. The basic principles of the GLU system initiated at CDS, as well as some tools based on the GLU protocol, are briefly described. Finally, the on-going developments, especially related to data mining purposes, are presented.

Client/Server Access to the Simbad Database within the Aladin Project

Aladin, the Deep Sky interactive Facility, is a new CDS project which provides interactive access to both sky surveys, (starting with optical ones) and also to catalogue data about the studied field objects (Paillou et al. 1993).

DIVISION XII / COMMISSION 5 / WORKING GROUP FITS DATA FORMAT

The Working Group FITS (WG-FITS) is the international control authority for the Flexible Image Transport System (FITS) data format. The WG-FITS was formed in 1988 by a formal resolution of the IAU XX General Assembly in Baltimore (MD, USA), 1988, to maintain the existing FITS standards and to approve future extensions to FITS.

DIVISION XII / COMMISSON 5 / WORKING GROUP: FITS

The business meeting began with a brief review of the current rules and procedures of the WG, which are documented on the WG web page. Four regional FITS committees have been established by the WG, covering North American, Europe, Japan, and Australian/New Zealand, to provide advice to the WG on pending proposals. While it is recognized that this committee structure might need to be revised to provide representation to other regions, the current system is working well, and there were no motions to make any changes at this time.

COMMISSION 5: DOCUMENTATION AND ASTRONOMICAL DATA

Commission 5 and its working groups have continued to operate at a high level of activity over the last three years. In an era when the volume of astronomical data generated by next-generation instruments continues to increase dramatically, and data centres and data tools become increasingly central to front-line astronomical research, the activities of Commission 5 are becoming even more significant. However, most of the activities of Commission 5 take place through its working groups. That was reflected in the meetings at the IAU GA, where there was only one short Business Meeting of the Commission as a whole, but several vigorous meetings of the working groups.