Core Projects: The Velocity Structure of star-forming Regions

These are the primary science projects conducted by AM team members utilizing AM's developed tools.

Please see our general projects page for an overview.

Outflows and Shells in Perseus

We have analyzed data of the Perseus star forming region collected during 2002-2006 at the FCRAO (Five College Radio Astronomy Observatory) radio telescope as part of the COMPLETE Survey. The Perseus molecular cloud complex (8 square degrees or ~150,000 pixels) was observed in ¹²CO and ¹³CO. Observing these molecules provides one with the structure of the cloud where ¹²CO traces the "surface" and low density gas, while ¹³CO reveals the inner gaseous structures. This spectral data (one spectrum per pixel in the map) can be converted from wavelength to velocity via the Doppler shift, thus the data can be represented in a cube as a series of intensity maps where each map in the series represents the gas emission’s intensity at a particular velocity. When this data is represented in 3D, one is visualizing the kinematics of the molecular gas in the cloud (Borkin et al. 2005).

We have applied this novel technique in the search for outflows. Bipolar outflows of gas originate from young stars forming as gas collapses on them while spinning. This outflow phase is one that all young stars go through during their development, but it is a poorly understood phenomena and difficult to identify with conventional methods. The standard way to find outflows is by looking at individual spectra (an outflow lobe, depending on the telescope’s resolution, is only comprised of a few spectra), an integrated intensity (average emission over all velocity values) map, or individual maps over a range of velocities. These methods prove tedious and inefficient especially for large surveys like COMPLETE. When visualizing Perseus in ¹²CO and ¹³CO as a series of isosurfaces, the outflows are rapidly identified visually as "spikes" due to there extreme velocities observed along the line of sight. With this new outflow identification method, we have extended the known length of many outflows and discovered dozens of new outflows in the Perseus region shortening the feature identification process from months to minutes (Borkin 2006, Borkin et al. 2008 in prep).

Project Lead: Michelle Borkin (IIC)

Contributors: Hector Arce (Yale), Alyssa Goodman (CfA), & Michael Halle (SPL/IIC)

Why do Stars form where they do?

The kinematical state of a given molecular cloud is thought to critically influence the formation of stars within it. In essence, this determines (among other parameters) where stars form in clouds. Our knowledge about the velocity structure is, however, still limited at present, and we therefore study several aspects of cloud kinematics with new methods and samples.

Specifically, we presently

• use innovative techniques (i.e., dendrograms) to characterize cloud properties on a continuous range of scales (i.e., from small peaks to the whole cloud);
• conduct a survey of contraction motions (and deuteration) in Perseus;
• investigate the kinematics (and chemistry) of some Perseus dense cores with unusual chemical characteristics; and we
• survey the kinematics and chemistry of dense gas in the Taurus molecular cloud.

These studies are partially based on existing COMPLETE surveys. Further data is presently acquired using diverse millimeter and sub-millimeter telescopes. This data provides the major testbed for the Slicer development, since it can be fully exploited only when using 3D visualization.

The attached image illustrates part of this research. Some ¹³CO clumps (highlighted in red) in the star-forming L1448 complex in Perseus are (in a relative sense) strongly self-gravitating. These do contain many, but not all of the dense cores (yellow) identified in dust emission (shown as greyscale) and NH₃ observations. Self-gravity thus seems to play a limited role in the evolution of clumps in molecular clouds towards the formation of dense cores. Further analysis actually indicates that a large fraction of the small-scale structure in molecular clouds is actually not confined by own gravity, but by external pressure.

Project Lead: Jens Kauffmann (IIC/CfA)

Contributors: Erik Rosolowsky (Kelowna), Jaime Pineda (CfA), Mario Tafalla (Madrid), Paola Caselli (Leeds), Michelle Borkin (IIC), Alyssa Goodman (CfA), & Michael Halle (SPL/IIC)

On What Scale do Molecular Clouds get Torn Apart?

NEW: Interactive 3D PDF showing dendrogram and CLUMPFIND analysis of the ¹³CO emission of the L1448 region of Perseus.

Rosolowsky et al. (2008) presented a novel technique to identify nested objects in molecular clouds. Its results can be interactively explored using the DendroStar application (try the applet). Further characterization of these objects allows to estimate their mass, size, and internal velocity dispersion. With these parameters in hand it becomes possible to gauge the gravitational stability of an object: will keep its integrity, or will it disperse? This research is ideally suited for AM, since only or 3D tools allow to appropriately explore the wealth of structure in these nested objects.

As observations show, some will disperse, while others supposedly won't. Since the objects are nested, and thus all scales of a molecular cloud can be probed, this essentially allows to assess beyond which scale the cloud will disintegrate. Such a characterization provides star formation theorists with crucial input that is nowhere else available.

This research will soon be published in a major scientific journal. As a part of this effort, we will help introducing interactive 3D PDFs into the world of refereed publishing.

Project Lead: Alyssa Goodman (CfA)

Contributors: Erik Rosolowsky (Kelowna), Michelle Borkin (IIC), Jonathan Foster (CfA), Michael Halle (SPL/IIC), Jens Kauffmann (IIC/CfA) & Jaime Pineda (CfA)