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Last modified: 25 May 2012

URL: http://cxc.harvard.edu/iris/v1.1/threads/entry/thread.html

Loading Data into Iris

Iris Threads



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 from your local disk into Iris, import data directly from NED, or transmit data from a SAMP-enabled application.

It is expected that users will need to input SED data in various file formats in order to construct a mult-segment SED of a source. Consequently, the SED Builder tool within Iris is equipped to convert user SED data files in non-native formats into one of the two file formats natively supported by Iris, IVOA-compliant VOTable or FITS. 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 to read SED data into Iris to begin your data analysis session.

Last Update: 25 May 2012 - updated for Iris 1.1


Supported SED Data Types and Formats

SED data Files in any of the following formats may be input to Iris for analysis. However, as Iris natively supports only IVOA-compliant FITS and VOTable format, when a file is loaded in a non-native format, an extra step is required of the user in order to convert the data to a compatible format, using the SED Builder.

  • CSV
  • FITS (standard and non-standard)
  • VOTable (standard and non-standard)
  • IPAC
  • TST

The SED Builder 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 Builder and how to use it to convert your SED data into a compatible format, refer to the Building a SED in Iris section of the Iris How-to Guide.

An Iris input file should contain a table of photometric data, where one or more of the columns lists measured source flux, flux density, or luminosity values, with optional, associated columns listing the errors on the flux values; and, if loading a spectral segment (as opposed to a photometric point(s)), an additional column listing the spectral coordinate values, either wavelength, frequency, or energy.

Note: While the time coordinate associated with 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.)

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-1.1-<plat>-<arch>/Iris &
[snapshot of   Iris GUI]

You can also start the application by opening a folder manager window on Linux or the Finder on Mac, navigating to the Iris 1.1 directory, and double-clicking on the "Iris" executable.

This opens the desktop interface with icons that launch the various tools used by the application, as well as a link to this on-line help documentation.

All of the windows launched by Iris will be confined within this desktop. Each window can be iconified and its icon will stay in the Iris desktop itself, so that it will not take up space in your applications bar.

The Iris desktop takes on the same look and feel as your native desktop, and the behaviour is consistent with your native environment. For example, on Mac OS X, iconified windows appear as miniatures at the bottom-center of the desktop, while on Linux, they could be draggable buttons placed on the bottom-left of the desktop.

The SED Builder desktop can itself be resized, maximized and iconified in your native desktop.

Loading SED Data

You are provided with three options for loading data: browsing for a file on your local disk, entering a URL file location, or searching NED for SED data associated with the entered target name.

Loading SED Data from File

A SED data file stored on your local disk or at a URL address may be uploaded into the Iris main display simply by starting the application and selecting the Load File icon on the Iris desktop.

[Iris GUI snapshot]

After browsing for and selecting your SED data file on disk, or entering the URL address where the file is located, simply select the appropriate file format from the drop-down menu, and then either "Load Spectrum/SED" or "Load Photometry Catalog." The former option is appropriate for a data file consisting of one or more segments of data, and the latter, for a file consisting of a photometric point(s). If a segment is loaded and it is already in one of the formats natively supported by Iris, it will automatically be displayed in the Iris Visualizer; otherwise, you will have to complete an extra step of entering configuration information in order to convert it for upload into the display. Likewise, if a photometry catalog is loaded, you will have to enter several pieces of information in order to 'tell' Iris how to display the points. The "Building an SED in Iris" section of the Iris How-to Guide demonstrates the use of these two loading options.

IVOA-compliant SED files are available from SED services such as the NASA/IPAC Extragalactic Database (NED), which you can upload into the application (recall the option to directly import SEDs into Iris from NED, in particular). 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 following objects: 3C 273, 3C 295, 3C 66A, M31, M87, NGC 1068, and NGC 4151.

The sample files in the "examples" directory are shown below:

% ls <basedir>/iris-1.1-<plat>-<arch>/examples/

Importing SED Data from NED

As an alternative to loading data from file, SED data from NED may be directly imported into Iris via the "Get an SED from the NED Service" option in the Load File window.

[Iris GUI snapshot]

The entered target name will be resolved by NED, and any associated SED data found in the NED photometry archive will be returned by the web service and loaded into the tool. (The "Change Endpoint" input can be used to change the NED service URL which is queried; however, this not usually needed.)

After entering the name of the desired target and selecting "Import NED SED", if the search was successful the SED data for the source will appear automatically in the Iris Visualizer, and an entry for the imported SED will be added to the SED Builder window.

[Iris GUI snapshot]

This example 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 or multiple selected data points may be viewed with the "Metadata" button in the Iris main display, as demonstrated in the "Visualizing SED Data" section of the Iris How-to Guide.

Transmitting Data from a SAMP-enabled Application

In the lower-left corner of the Iris desktop there is an icon that shows the status of the Simple Application Messaging Protocol (SAMP) connection, which the tool uses to communicate with other interoperable applications.

[snapshot of   Iris GUI]

SAMP is a Virtual Observatory protocol that allows desktop applications to communicate with each other. If you use other SAMP-enabled Virtual Observatory applications that manipulate tables of astronomical data, such as Topcat or Aladin, you can transmit tables of data from these external applications to Iris.

To transmit data to Iris from another SAMP-enabled desktop application, simply broadcast the table from the external application. If in the SED Builder window of Iris there are no open SEDs, a new SED will be created.

[Transmitting a table from Topcat to Iris]

Note that the "Broadcast SED" button in the SED Builder window can be used to transmit an SED from Iris to another SAMP-enabled application.


08 Aug 2011 updated for Iris Beta 2.5
25 Sep 2011 updated for Iris 1.0
25 May 2012 updated for Iris 1.1

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Last modified: 25 May 2012
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