An Atlas of DRAGNs

The Atlas Web Pages

We hope these pages are fairly easy to use. The material consists of five categories: Explanatory material and tables and listings, both accessible from the index on the Atlas Home Page, the Main Pages, accessible from various listings, and the Data Pages and Other images, accessible from the Main Pages and each other. There is also a Search page which allows you to go straight to any of the Main, Data, or Other images pages.

At the bottom of each page is a menu bar containing a series of links. The slightly mysterious pair labelled "<<<<" and ">>>>" or "Prev." and "Next", just take you to the previous or next page in the sequence.

The Frame

If you want to keep the menu bar on-screen all the time, and your Web browser can cope, click the frames link on the home page. This does slow down page transfer times slightly.

The frame links are done as a Java Applet, so for the frame links to work, your browser must have both Java and Javascript (or JScript). Versions 3 and higher of Netscape Navigator and Internet Explorer work fine. Netscape Navigator 2 works fairly well (don't use the "Back" button!).

Explanatory Material

This is divided into two main sections: the Introductory Material is for interested laypeople and undergraduates, and fills in some of the background which professionals will take for granted. The Description of the Atlas gives a complete technical description, primarily aimed at professionals; but for other readers we give links from the more technical terms to the glossary.

While the Atlas is being put together there are also "What's New" and "Status" pages.

Tables and listings

Much of the information in the Atlas is summarised in a set of tables which give a quick overview of the sample properties. For an explanation on table data items, and to find the source of the data quoted, click on the table header. These explanations are hyperlinked to the glossary, for those unfamiliar with the astronomical jargon.

NOTE: The data in these tables is still being compiled, and at present some of this material has not been double-checked. While we are confident that the vast majority has been correctly entered, we are equally certain that a number of typographical errors remain; however, we do list the original sources of all the data quoted.

Radio Data
This table gives useful information from the literature on the DRAGNs, with references.
B1950.0 positions of the optical identification or the radio core (whichever is more accurate).
Optical Data
This table gives useful information from the literature on the optical identifications.
Structural Data
Various structural parameters measured from the Atlas images.
Alphanumeric Listing
A clickable index to the Main Pages, with a subset of the Radio and Optical data.
Icon list
Shows the low-resolution C20 images, all displayed together (in order of increasing radio luminosity). It is also a clickable index to the Main Pages.

The Main Pages

The Main Page for each DRAGN gives a JPEG display of the full-resolution image, a table giving the details of that image, comments on each object (mostly not written yet!), and a table of the basic properties of the DRAGN and its host galaxy or quasar, which is a subset of the data from the Radio and Optical tables. The "supplementary" high-resolution images are mentioned in the comments on the main pages, and can be accessed via the "Other images" link on the navigation bar.

The JPEG images are designed to bring out clearly the main structural features of each DRAGN. This often involves the use of a highly non-linear translation between the original radio intensity and the displayed pseudo-colour (see the note on displaying radio images). As discussed in the description of the Look-up table, we have chosen the transfer function in each case to give the least misleading representation consistent with seeing all the interesting structure in the image. For quantitative work there is no substitute for looking at the original FITS images.

The JPEGs are usually at full scale, i.e. one JPEG pixel per FITS pixel. To speed up transfer time, we have shrunk some of them to keep the file sizes to less than about 10 kbytes. These can be recognised by their thick red borders. Full-scale versions of these can be accessed by clicking on the reduced-scale images.

In many images, the position of the active nucleus is fairly obvious from a central radio core. Where it is not, we have plotted a cross marking the position of the optical identification.

The Main pages can be accessed via the alphanumeric and icon listing page. They can also be paged through by using the "Prev." and "Next" links at the bottom of each page, and from the "Main Page" link at the bottom of each Data Page and Other image page (see below). The internal order is of Right Ascension, which is nearly alphanumeric order except for objects with non-3C names. They can also be accessed individually via the search form on the Home page or on the Search page.

The Other Images

The C20 image for each object, and any supplementary images (including images of cores) are shown on the "Other images" page, along with a table for each image giving details.

These pages can be accessed via the "Other images" link on the Main and Data Pages, and it is also possible to page through them using the "Prev." and "Next" buttons at the bottom of each page. They can be reached directly via the Search page.

The Data Pages

There is a separate Data Page listing all the data for each DRAGN, excluding the derived parameters such as Power and Linear size. As well as reproducing the data in the tables, we give more extensive information on the radio, infrared and optical flux densities, and complete bibliographic references.

The Data Pages can be accessed from the "Data Page" link on each Main Page and Other images page, from each other in sequence, and from the Search page.

Please read the note about data reliability.

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Last modified: 1998 March 12
J. P. Leahy