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: http://www.adass.org/adass/proceedings/adass99/P1-16/
Дата изменения: Fri Oct 13 00:57:25 2000 Дата индексирования: Tue Oct 2 06:15:48 2012 Кодировка: Поисковые слова: arp 220 |
As the CNOC2 Field Galaxy Redshift Survey neared completion in 1998, we had a problem. This deep pencil-beam redshift survey of galaxies in four ``patches'' distributed across the northern sky offered a sizable dataset including spectra for several thousand objects, UBVRI images for many more, plus measured properties such as positions, magnitudes, redshifts, and spectral indices (Yee et al. 2000). We were eager to do science involving several of these types of data; for example, using galaxy positions to identify galaxy groups and comparing the properties of these objects to those of the global sample. However, we needed a tool which would integrate the various data involved in the survey, including:
The Victoria Explorer for Redshift Databases on the Internet (VERDI) is a general database program for redshift surveys which allows anyone with a Web browser to access galaxy images and spectra. VERDI runs under Unix and is otherwise entirely based on available free software. The input Web forms communicate with the database through CGI scripts written in Perl. These scripts access the database either directly or through self-generated Gawk scripts for running fast queries. VERDI uses IRAF directly from the Unix shell for image manipulation and Java to power the interactive spectral display. All data are stored in flat ASCII files or FITS images.
The heart of VERDI is Notebook Mode, so called because it displays a page summarizing the key information for a single object. One accesses Notebook Mode one of three ways: by entering the serial number of the desired object in the Notebook Mode entry page, by clicking the image of an object in Patch View Mode, or by clicking an object link in the output of Query Mode. Each notebook page features four main elements (see Figure 1):
The CNOC2 survey regions include four patches on the sky, each of which consists of about twenty contiguous fields that correspond to the field of view of the CFHT MOS used to carry out the survey. After the user selects a patch and a field, Patch View Mode displays a clickable image for that field. By pointing the mouse to a target, the observer is informed of the redshift, magnitude, and serial number for the object. Clicking on a cataloged object then brings up the corresponding Notebook Mode page. Generation of the image maps used in Patch View Mode is done automatically through a script. Patch View Mode is particularly useful for quickly scanning images and retrieving relevant information for objects of interest.
Query Mode is a basic database querying system, allowing the user to retrieve data for a set of objects which match the criteria that he or she specified. Samples can be selected based on magnitude, redshift, position, serial number, or any other quantity in the database. Each field can be qualified with a lower bound, and upper bound, or a range, and the criteria on different fields can be combined through AND or OR logic.
The data for objects which match the selection criteria are displayed in tabular form, with hyperlinks that allow access to the corresponding Notebook Mode pages to provide more detailed information. Despite the lack of a true database server (queries are executed by spawning a Gawk script to parse the database), complex queries can be formed and searches can be completed quickly.
VERDI is free, fast, and adaptable, and has enormously simplified the task of accessing the CNOC2 database. We wrote VERDI with the intention of sharing it, and are pleased that the DEEP survey team at UCSC has adapted it to meet their needs. Enquiries from other interested parties are welcomed.
Ralf Moros generously allowed us to bundle his XYMeter Java applet into VERDI for displaying spectra. Development of VERDI was supported by the Canadian Network for Observational Cosmology (CNOC) project through a grant from NSERC.
Yee, H. K. C., Morris, S. L., Lin, H., Carlberg, R. G., Hall, P. B., Sawicki, M., Patton, D. R., Wirth, G. D., Ellingson, E., & Shepherd, C. W. 2000, ApJS, in preparation