Loading Data into Iris

Iris Threads

Overview

Synopsis:

In order to visualize and analyze a wide-band SED of an astronomical object, multiple SED segments and/or photometric points from various observatories and file locations must be gathered and coplotted; Iris features multiple entry points for SED data to facilitate this process. You can load data files in FITS or VOTable format from your local disk into Iris, or import data directly from NED on the Unix command-line upon startup of the application.

As SED data can be contained in files in a variety of formats, the Iris SED Importer tool is available for converting data files in unsupported formats for upload into the application (you can also upload SED data from NED into the SED Importer). Independent of how each data set is loaded and from where, Iris can simultaneously plot multiple SED segments together in the main display.

This thread demonstrates the various ways in which to read SED data into Iris to begin your data analysis session.

Last Update: 25 Sep 2011 - updated for Iris 1.0 1

Supported SED Data Types and Formats
Starting Iris
Loading SED Data from File
Importing SED Data from NED
History

Supported SED Data Types and Formats

Iris supports IVOA-compliant SED files in both FITS and VOTable format. An input file should contain a table of photometric data, where one of the columns lists measured source flux, flux density, or luminosity values; another column lists the spectral coordinate values, either wavelength, frequency, or energy; and a third, optional column lists errors on the flux values.

Note: While the time coordinate associated to a photometric or spectroscopic measurement is a fundamental piece of information, the explicit dependence on time is ignored in the context of SED analysis in Iris. (The time t of the observation is always contained in the metadata accompanying every measurement supported by Iris.)

If you have a SED file in an unsupported format which you would like to import into Iris - e.g., CSV or ASCII - you may do so by first converting the file to a supported format via the SED Importer tool. The SED Importer tool accepts as 'non-standard' any binary or text-based file that does not conform to the IVOA SED, Spectrum and Photometry Data Model; these include FITS and VOTable files which do not conform to the IVOA standards. To learn more about the SED Importer and how to use it to convert your SED data for import into Iris, refer to the Converting SED Data to a Supported Format section of the Iris How-to Guide.

Starting Iris

After downloading and installing Iris according to the procedure outlined in the Download & Installation page, the GUI may be started from the Unix command line as follows:

% <basedir>/iris-1.0-<plat>-<arch>/Iris &

You can also start the application by opening a folder manager window on Linux or the Finder on Mac, navigating to the Iris 1.0 directory, and double-clicking on the "Iris" executable.

In Iris 1.0, the SED Importer tool which is bundled with the Iris software package is run separately from the main Iris application, as demonstrated on the Iris Download & Installation page.

Loading SED Data from File

A SED data file stored on your local disk may be uploaded into the Iris main display simply by starting the application and selecting the Read from file option in the File menu.

You can obtain IVOA-compliant SED files by visiting the website of an SED service which produces such files, such as the NASA/IPAC Extragalactic Database (NED), or by converting non-compliant data using the SED Importer tool available in the Iris package. The Iris package includes sample SED files in the "examples" subdirectory of the installation directory, which were downloaded from NED by searching its photometry data archives for SEDs of the relevant objects, e.g., 3C 273, 3C 295, etc.

The sample files in the "examples" directory are:

% ls <basedir>/iris-beta-2.5-<plat>-<arch>/examples/
3c273.xml
3c295.xml
3c66a.xml
m31.xml
m87.xml
ngc1068.xml
ngc4151.xml

To quickly download SED data from NED for a particular source and save to a file, you could issue a 'wget' command right on the command line, including a query on object name which will be used as an identifier in searching NED:

% wget -O 3c273.xml 'http://vo.ned.ipac.caltech.edu/services/accessSED?REQUEST=getData&TARGETNAME=3c273'

Importing SED Data from NED

As an alternative to loading data from file, SED data from NED may be directly imported into Iris while starting the application from the command line, bypassing the extra, intermediate step of downloading the data to file. You can modify the usual Iris startup command by adding a query of the following form, which specifies an object name to use as an identifier in the search of NED.

%  <basedir>/iris-1.0-<plat>-<arch>/Iris "http://vo.ned.ipac.caltech.edu/services/accessSED\?REQUEST=getData\&TARGETNAME=3c066A"

This query returns a collection of photometric data points obtained by various astronomical observatories, all contributed to the NED photometry data archive in association with blazar 3C66A.

The metadata associated with one of the imported photometric data points may be viewed by right-clicking on that point in the Iris display, as shown in the image below.

The metadata for all plotted points may be viewed simultaneously by selecting the "Coplot" menu option, and then right-clicking on the filename in the window that appears.