Perseus viewed using 3D Slicer

We have created several "scenes" that load pre-created data into Slicer for easy viewing. Please choose from one of our Perseus datasets below, or go back to our pages on how to use Slicer.

All scenes are based on ¹³CO (J=1-0) data from the COMPLETE survey of star forming regions (Ridge et al. 2006). They reveal the velocity structure of the Perseus molecular cloud complex. The L1448 cloud in Perseus is presented in detail.

Iso-Intensity Surfaces for L1448

This representation is the 3D equivalent of contour plots. The surfaces are drawn levels of 0.7, 1.6, and 2.5 K. The plot highlights the hierarchical, nested structure of the emission. Note how physically separate structures, which are projected onto each other in 2D representations (the "A" perspective; see below), are easily disentangled in velocity space.

The following steps are necessary to view L1448.

1. Download and unpack the scene files (6 MB). These contain all Slicer settings as well as the data for the iso-intensity surfaces.

2. Run 3D Slicer in the directory into which the scene files were unpacked, just as described in the Slicer installation instructions.

Slicer will open three windows. The view window (opens on the righthand side of the screen) will show the actual 3D rendering of the data. The menu window (on the lefthand side) contains the controls for most Slicer functions. The message window is not of interest to most users. See our documentation of Slicer interfaces for details.

3. Select "Open Scene..." in the "File" submenue of the menu window. Select and load "L1448_IsoIntens.xml" using the "Browse" functionality.

Slicer will then read in the information on iso-intensity surfaces in L1448. The scene eventually opens in the viewer window. It shows the cloud oriented just as seen projected on the sky (north up, east to the left). The velocity increases towards the back of the scene.

4. Control the view by dragging the mouse in the viewer window while holding mouse buttons.
5. Use the view selector in the menu window (invisible unless mouse points onto the 3D Slicer logo) to control the view window.

The viewing angle can be changed by dragging the mouse in the viewer window while holding the left mouse button. Zooming and sideways movements are possible when holding the right and the middle button, respectively, while dragging. The view selector in the menu window can be used for finer control of the view window. The initial view can be restored by choosing the "A" perspective. All perspectives except "A" and "P" correspond to position-velocity diagrams.

The perspective names (e.g., "A", "L", "S") presently refer to medical terms. Later Slicer versions will have a view selector not only taylored to needs in medicine.

CLUMPFIND Results for L1448

Please follow the instructions for L1448 iso-intensity plots to view the CLUMPFIND scene files (8 MB). Read the "L1448_CLUMPFIND.xml" scene file.

CLUMPFIND is one of the most commonly used astronomical algorithms used to break maps of molecular clouds up into smaller entities. The CLUMPFIND results can then be used to, e.g., infer the characteristic diameter of structures in molecular clouds. The algorithm does, however, not preserve the hierarchical structure of clouds. Instead it decomposes a cloud into non-overlapping fragments. These objects are visualized in this scene. Color is used to better separate neighboring clumps. While CLUMPFIND is a useful approach for many purposes, comparison with the L1448 iso-intensity plots - which are constructed for exactly the same region - reveals that for larger clouds CLUMPFIND by definition fails to capture the hierarchical structure of clouds.

The CLUMPFIND algorithm was introduced by Williams, Blitz & Stark (1995). It can be downloaded freely from the homepage of Jonathan Williams. The CO data were processed by the COMPLETE survey of star forming regions.

Iso-Intensity Surfaces for the Perseus Complex

Please follow the instructions for L1448 iso-intensity plots to view the Perseus cloud scene files (19 MB). Read the "Perseus_IsoIntens.xml" scene file.

This scene shows all of Perseus in exactly the same fashion as the L1448 iso-intensity plots, but for a resolution lower by a factor 2 along all axes. The surfaces are drawn for antenna temperatures of 0.7, 1.6, and 2.5 K, just like before for L1448. The latter cloud is actually seen in this scene as part of the south-western tip of the cloud (i.e., "lower right corner" when viewed from the "A" perspective). Note how structures seemingly simple in projection onto the sky (i.e., viewed from the "A" perspective) are actually characterized by a very complex velocity field.