# Investigating the structure and fragmentation of a highly filamentary IRDC

Henshaw, JD and Caselli, P and Fontani, F and Jimenez-Serra, I and Tan, JC and Longmore, SN and Pineda, JE and Parker, RJ and Barnes, AT (2016) Investigating the structure and fragmentation of a highly filamentary IRDC. Monthly Notices of the Royal Astronomical Society. ISSN 0035-8711

 Text 1607.07452v1.pdf - Accepted Version Download (5MB)

## Abstract

We present 3.7 arcsec (~0.05 pc) resolution 3.2 mm dust continuum observations from the IRAM PdBI, with the aim of studying the structure and fragmentation of the filamentary Infrared Dark Cloud G035.39-00.33. The continuum emission is segmented into a series of 13 quasi-regularly spaced (~0.18pc) cores, following the major axis of the IRDC. We compare the spatial distribution of the cores with that predicted by theoretical work describing the fragmentation of hydrodynamic fluid cylinders, finding a significant (factor of ~8) discrepancy between the two. Our observations are consistent with the picture emerging from kinematic studies of molecular clouds suggesting that the cores are harboured within a complex network of independent sub-filaments. This result emphasises the importance of considering the underlying physical structure, and potentially, dynamically important magnetic fields, in any fragmentation analysis. The identified cores exhibit a range in (peak) beam-averaged column density ($3.6{\rm x}10^{23}{\rm cm}^{-2}<N_{H,c}<8.0{\rm x}10^{23}{\rm cm}^{-2}$), mass ($8.1M_{\odot}<M_{c}<26.1M_{\odot}$), and number density ($6.1{\rm x}10^{5}{\rm cm}^{-3}<n_{H, c, eq}<14.7{\rm x}10^{5}{\rm cm}^{-3}$). Two of these cores, dark in the mid-infrared, centrally-concentrated, monolithic (with no traceable substructure at our PdBI resolution), and with estimated masses of the order ~20-25$M_{\odot}$, are good candidates for the progenitors of intermediate-to-high-mass stars. Virial parameters span a range $0.2<\alpha_{\rm vir}<1.3$. Without additional support, possibly from dynamically important magnetic fields with strengths of the order 230$\mu$G<B<670$\mu$G, the cores are susceptible to gravitational collapse. These results may imply a multi-layered fragmentation process, which incorporates the formation of sub-filaments, embedded cores, and the possibility of further fragmentation.

Item Type: Article This is a pre-copyedited, author-produced PDF of an article accepted for publication in Monthly Notices of the Royal Astronomical Society following peer review. The version of record J. D. Henshaw, P. Caselli, F. Fontani, I. Jiménez-Serra, J. C. Tan, S. N. Longmore, J. E. Pineda, R. J. Parker, and A. T. Barnes. Investigating the structure and fragmentation of a highly filamentary IRDC, Monthly Notices of the Royal Astronomical Society, © 2016 The Authors Published by Oxford University Press on behalf of the Royal Astronomical Society is available online at: http://dx.doi.org/10.1093/mnras/stw1794 astro-ph.GA; astro-ph.GA Q Science > QB Astronomy Astrophysics Research Institute Oxford University Press Author 01 Aug 2016 08:40 01 Aug 2016 08:40 10.1093/mnras/stw1794 http://researchonline.ljmu.ac.uk/id/eprint/3957

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