head 1.1; access; symbols; locks http:1.1; strict; comment @# @; 1.1 date 2003.02.19.11.46.55; author MarkusDolensky; state Exp; branches; next ; desc @none @ 1.1 log @SED User Requirements @ text @USER REQUIREMENTS FOR THE SED AVO TOOL ************************************** This document is a draft specification of scientific functionality of the SED tool. Developent of the SED tool is focussed on the January demo, but with future development in mind. This document does not cover the technical aspects of developing the SED tool. We expect this will be addressed by P. Fernique (Aladin developer, CDS) and M. Dolensky (ESO). However we assume the conceptual design is that Aladin will provide the ability to select individual sources, or all sources withing a specified region, then output the catalog information on those sources in VOTable format which is input into the SED tool. The purpose of this document is to describe what the tool should do, from the user point of view. Some functionality will be immediately required (Priority 1-Critical), some other will be consider important, but it might be implemented in a later stage, eg for the advanced demo foreseen for August 2003 (Priority 2-Major). Other more general functions are herewith described, but left for future developments (Priority 3-Future). The requirements are grouped in three main areas: 1) SED I/O, descibing what the SED should receive as input, and what capabilities are required for output; 2) basic SED capabilities, to do with the graphical representation of the data 3) Interface/interaction of the SED tool with other systems (Aladin) The SED tool ============ An SED is a low resolution spectrum, compiled by merging photometrical measurements taken at different wavebands, not necessarily by the same instrument/telescope, hence with possible different spectral resolutions, different precisions, and different units, of the same astronomical object. The primary functionality of the SED tool is to graphically display the spectral energy distribution of an astronomical object. Requirements: ============= SED Input/Output ---------------- o SED Input [R1] (Priority 1-Critical) The underlying assumption is that the SED tool will receive as input a list of data points with already homogenised units. Such list shall include error bars on both the X and Y axes. The basic input will hence consist of a table providing wavelength (or frequency), the width of the pass band, the flux density and the associated flux error. [R2] (Priority 2-Major) At a later stage (not for this first demo), the SED tool might be able to deal with inhomogeneous datasets, applying the necessary transformations on the fly, provided that the necessary units and zeropoints will be associated to each data point. o SED Output [R3] (Priority 1-Critical) The user shall have the possibility to export the SED information in some intelligible format (ASCII or FITS) [R4] (Priority 2-Major) The user shall have the possibility to print and/or save as postscript the plotted SED SED basic functionality ----------------------- Plot: [R5] (Priority 1-Critical) The main window of the SED should have a simple plot box with axes appropriate for plotting SEDs Axes: The units of the Y axis are to be chosen among these: Y axis [FLUX]: Fnu Jy | W/m^2/Hz | erg/cm^2/sec/Hz nuFnu Jy.Hz | W/m^2 | erc/cm^2/sec Flambda W/m^2/Angstrom | erg/cm^2/sec/Angstrom lambaFlambda W/m^2 | erg/cm^2/sec More likely, given that the flux dynamic range can be very big across the spectrum, the default units for the Y axis shall be the logarithm (base 10) of the Flux (that is, the log10 of one of the above-mentioned flux representations). The units of the X axis are to be chosen among these: X axis [spectral range]: Wavelength Angstrom | microns Frequency Hz Velocity* km/sec As for the Flux, also the X axis will be likely represented in terms of the log10 of one of the indicated units. [ * Velocity could be implemented at a later stage ] [R6] (Priority 1-Critical) It is considered critical to have at least one representation available for the demo (e.g. log10(NuFnu) vs log10(nu) ) [R7] (Priority 2-Major) It is not considered critical the transformation from one representation to another. This functionality shall be implemented at a later stage. Error bars: [R8] Priority: 1-Critical It shall be possible to turn on/off the error bars, both, but not necessarily simultaneously, in x and y. Zoom: [R9] Priority: 1-Critical It shall be possible to zoom in and out on selected wavelength and flux range Normalisation: [R10] Priority: 2-Major Ability to normalise a SED at any point. May be important for overlaying template spectra, or fitting models Multiple spectra: [R11] Priority: 2-Major Ability to plot SEDs of muliple sources SED Interface/Interaction with other systems (Aladin) ----------------------------------------------------- Source selection: (Aladin requirements are marked with an A followed by a running number) [A1] Priority: 1-Critical Ability to select individual sources (default) [A2] Priority: 2-Major Ability to select multiple sources [A3] Priority: 1-Critical / 2-Major ? Ability to display a set of colour-colour diagrams for all the sources in the user selected region (reusing the SED tool) The scenario is as follows: the user will see a preview image with overlayed the catalogue sources, and will also have a panel with the different colour-colour diagrams, such that (1) by moving the pointer onto the preview image and/or on a colour-colour diagram the closest data-point will be highlighted both on the preview AND in the colour-colour diagrams; (very useful to find the outliers). [A4] Priority: 1-Critical Clicking on the data-point (both on the preview image and/or on the colour-colour diagram), Aladin shall extract the relevant measurements from all catalogues and pass the VOTable to the SED tool. If, at that point, the SED tool has not been activated yet, Aladin should fire it off. [A5] Priority: 3-Future Apertures - show extraction apertures somehow ... ... more to come ... especially to interface to Sextractor and to highlight the actual catalog record of each SED data-point. ... Issues for future development - anticipate overplotting spectra - anticipate interfacing with model fitting "modules(?)" - Mag to Flux conversion (when a non-homegeneous table is provided in input) - Velocity units - ability to show velocity units - Ability to apply redshift/blueshift to SEDs, with K correction - Ability to apply galactic extinction correction Priority: 3-Future Generalisation to spectra (i.e. many wavelength bins) - required for overplot of template spectra - VOTable issues, columns versus rows - individual wavelength bins of spectra don't have UCDs, but SED wavelength bins do have individual UCDs. Existing SED tools (very brief overview of existing SED tools) ============================================================== NED - SED plot NED has adopted effective wavelengths, band widths, and absolute calibrations for the different photometric systems from the papers containing the data, or from the papers originally defining the photometric systems, whenever possible. When this information is not given in these papers, we have assumed the values in this table taken from various papers, but often from Table 9 in "Galaxy Colors in Various Photometric Band Systems" by M. Fukugita, K. Shimasaku, and T. Ichikawa, published in PASP, 107, 945, 1995 @