ATLASGAL: A Galaxy-wide sample of dense filamentary structures

Abstract

Context. Filamentary structures are ubiquitous in the interstellar medium. Investigating their connection to the large-scale structure of the Galaxy and their role in star formation is leading to a paradigm shift in our understanding of star formation. Aims. We study the properties of filamentary structures from the ATLASGAL survey, which is the largest and most sensitive systematic ground-based survey of the inner Galactic plane at submillimeter wavelengths. Methods. We use the DisPerSE algorithm to identify spatially coherent structures located across the inner-Galaxy (300• < < 60• and |b| < 1.5). As a result we produce a catalogue of ∼1800 structures; these were then independently classified by the five lead authors into one of the following types: marginally resolved, elongated structures, filaments, network of filaments and complexes. This resulted in the identification of 517 filamentary structures. We determine their physical properties and investigate their overall Galactic distribution.Results. We find that almost 70% of the total 870 µm flux associated with these structures resides in filaments and networks of filaments and we estimate that they are likely to be associated with a similar fraction of the mass. Correlating these structures with tracers of massive star formation we also find that a similar fraction of the massive star forming clumps are associated with filaments and networks of filaments, which highlights the importance of these types of structures to star formation in the Galaxy. We have determined distances, masses and physical sizes for 241 of the filamentary structures. We find a median distance of 3.8 kpc, a mean mass of a few 10 3 M , a mean length of ∼6 pc and a mass-to-length ratio of (M/L) ∼200-2000 M pc −1 . We also find that these filamentary structures are tightly correlated with the spiral arms in longitude and velocity, and that their semi-major axis is preferentially aligned parallel to the Galactic mid-plane and therefore with the direction of large-scale Galactic magnetic field. We find many examples where the dense filaments identified in ATLASGAL are associated with larger scale filamentary structures (∼100 pc), and argue that this is likely to be common, and as such these may indicate a connection between large-scale Galactic dynamics and star formation. Conclusions. We have produced a large and Galaxy-wide catalogue of dense filamentary structures that are representative of a particular size and mass range not previously well studied in the literature. Analyses of the properties and distribution of these filaments reveals that they are correlated with the spiral arms and make a significant contribution to star formation in the Galaxy. Massive star formation is ongoing within ∼20% of the filaments and is strongly correlated with the filaments with the largest mass-tolength ratios. The luminosity of the embedded sources has a similar distribution to the Galactic-wide samples of young massive stars and can therefore be considered to be representative.

The Molecular Cloud S242: Physical Environment and Star-formation Activities

“…These filaments are observed at various scales and often contain the starforming clumps and cores along their lengths (e.g. Schneider et al 2012;Ragan et al 2014;Contreras et al 2016;Li et al 2016, and references therein). However, the physical mechanisms concerning to their formation and their link to the star formation processes are not well understood.…”

SEDIGISM: Structure, excitation, and dynamics of the inner Galactic interstellar medium

“…Indeed, ATLASGAL provides high angular resolution at a wavelength sensitive to the cold dust and is unaffected by background contamination and saturation, which complicate the analysis of Hi-GAL data. On the other hand, Hi-GAL is more sensitive to emission from low-density structures, down to values of ∼10 21 cm −2 at 16 K, while ATLASGAL has a 5-σ column density sensitivity of ∼7.5×10 21 cm −2 for a dust temperature of 20 K. Li et al (2016) identified twelve filamentary structure candidates in the SEDIGISM science demonstration field based on the ATLASGAL data, nine of which are single filament candidates (elongated linear structures with typical aspect ratios larger than three), and the other three being networks of filaments (several filaments that seem to be connected to each other). A study of Hi-GAL column density map of the region reveals 88 filament candidates.…”

“…Recently, the ATLASGAL and Hi-GAL surveys were used to identify filament candidates in the Galactic plane through the analysis of their continuum emission at 870 µm (Li et al 2016), and at 70, 160, 250, 350 and 500 µm (Schisano et al 2014;Wang et al 2015), respectively. The two surveys deliver a unique dataset to compile an unbiased catalogue of filament candidates throughout the Galaxy.…”

“…A study of Hi-GAL column density map of the region reveals 88 filament candidates. Details on the two catalogues and on the methods used to identify the structures and extract their dust properties are given by Li et al (2016), Schisano et al (2014) and Schisano et al (in prep.). All twelve structures detected in ATLASGAL are also found in the Hi-GAL sample, hence, in the following discussion, we will focus on this common candidate list.…”

Hub-filament System in IRAS 05480+2545: Young Stellar Cluster and 6.7 GHz Methanol Maser

“…In starforming regions, the filamentary structures often harbor dense massive star-forming clumps and young stellar clusters (e.g. André et al 2010André et al , 2016Schneider et al 2012;Ragan et al 2014;Kainulainen et al 2016;Contreras et al 2016;Li et al 2016, and references therein). However, the role of filaments in the star formation process (including massive stars) is still a matter of debate (e.g.…”