The Central Artery of a Star-Forming Region

Abstract

Over the past several years, it has become apparent that what we once thought of as blob-like star-forming molecular “clouds” are in fact laced with prominent filamentary structure (André 2014). A paradigm has emerged where the so-called “dense cores” (Myers 1983) that provide the immediate reservoirs for the formation of stars are thought to form in much higher-aspect ratio “filamentary” structures. Recent work has shown, though, that even though “cores” are still typically thought of as thermal, quiescent and velocity-coherent (Goodman 1998) and only slightly prolate (Myers 1991), at high resolution they appear to contain very significant filamentary sub-structures (Pineda 2011).

One dense core that has been particularly well-studied of late is called “Barnard 5” or “B5,” and it is located at the extreme Eastern edge of the Perseus complex of molecular clouds (Figure 1, showing B5 in context of the COMPLETE Survey...maybe in rotating 3D??). Most recently, Pineda et al. (2015) found that highest resolution (VLA) mapping of dense gas (NH$$_3$$)(Pineda 2011) inside what was previously thought to be a relatively unstructured “velocity-coherent” dense core (Pineda 2010) reveals a small, extremely young, star cluster in the process of forming. The timescale of the cluster formation is very short (perhaps tens of thousands of years, Pineda et al. (2015)) in comparison with what is typically thought to be the lifetime of a dense core (of order hundreds of thousands of years, xxref). There is great debate about the lifetime of larger-scale molecular clouds like the Perseus complex that hosts B5, but typical estimates range from millions (xxref) to tens of millions (xxref) of years.

This Letter shows that the tiny cluster-forming filaments ($$\sim 10^{17}$$ cm) within B5 core ($$\sim 10^{18}$$ appear to lie positioned on top of, and aligned with much, longer filament that snakes its way from North to South through the entire B5 region ($$>10^{19}$$ cm) of Perseus ($$\sim 10^{20}$$ cm). The first evidence for this apparent structural identification came from Herschel Space Telescope imaging of long-wavelength dust continuum emission, but stronger support comes from the new velocity-resolved gas observations presented here (xxI hope!)

References

1. P. André, J. Di Francesco, D. Ward-Thompson, S.-I. Inutsuka, R. E. Pudritz, J. E. Pineda. From Filamentary Networks to Dense Cores in Molecular Clouds: Toward a New Paradigm for Star Formation. Protostars and Planets VI 27-51 (2014). Link

2. A. A. Goodman, J. A. Barranco, D. J. Wilner, M. H. Heyer. Coherence in Dense Cores. II. The Transition to Coherence. 504, 223-246 (1998). Link

3. P. C. Myers, G. A. Fuller, A. A. Goodman, P. J. Benson. Dense cores in dark clouds. VI - Shapes. 376, 561-572 (1991). Link

4. J. E. Pineda, S. S. R. Offner, R. J. Parker, H. G. Arce, A. A. Goodman, P. Caselli, G. A. Fuller, T. L. Bourke, S. A. Corder. The formation of a quadruple star system with wide separation. 518, 213-215 (2015). Link

5. J. E. Pineda, A. A. Goodman, H. G. Arce, P. Caselli, J. B. Foster, P. C. Myers, E. W. Rosolowsky. Direct Observation of a Sharp Transition to Coherence in Dense Cores. 712, L116-L121 (2010). Link

6. P. C. Myers, P. J. Benson. Dense cores in dark clouds. II - NH3 observations and star formation. ApJL 266, 309 IOP Publishing, 1983. Link

7. Jaime E. Pineda, Alyssa A. Goodman, Héctor G. Arce, Paola Caselli, Steven Longmore, Stuartt Corder. EXPANDED VERY LARGE ARRAY OBSERVATIONS OF THE BARNARD 5 STAR-FORMING CORE: EMBEDDED FILAMENTS REVEALED. ApJ 739, L2 IOP Publishing, 2011. Link