The ATLASGAL survey: distribution of cold dust in the Galactic plane. Combination with Planck data

Abstract : Sensitive ground-based submillimeter surveys, such as ATLASGAL, provide a global view on the distribution of cold dense gas in the Galactic plane. Here we use the 353 GHz maps from the Planck/HFI instrument to complement the ground-based APEX/LABOCA observations with information on larger angular scales. The resulting maps reveal the distribution of cold dust in the inner Galaxy with a larger spatial dynamic range. We find examples of elongated structures extending over angular scales of 0.5 degree. Corresponding to >30 pc structures in projection at a distance of 3 kpc, these dust lanes are very extended and show large aspect ratios. Furthermore, we assess the fraction of dense gas ($f_{\rm DG}$), and estimate 2-5% (above A$_{\rm{v}}>$7 mag) on average in the Galactic plane. PDFs of the column density reveal the typically observed log-normal distribution for low- and exhibit an excess at high column densities. As a reference for extragalactic studies, we show the line-of-sight integrated N-PDF of the inner Galaxy, and derive a contribution of this excess to the total column density of $\sim2.2$%, above $N_{\rm H_2} = 2.92\times10^{22}$ cm$^{-2}$. Taking the total flux density, we provide an independent estimate of the mass of molecular gas in the inner Galaxy of $\sim1\times10^9\,M_{\odot}$, which is consistent with previous estimates using CO emission. From the mass and $f_{\rm DG}$ we estimate a Galactic SFR of $\dot M = 1.3\,M_{\odot}$ yr$^{-1}$. While the distribution of diffuse gas is homogenous in the inner Galaxy, the CMZ stands out with a higher dense gas fraction. The low star formation efficiency of the Milky Way is well explained by the low $f_{\rm DG}$ in the Galactic ISM, while the high $f_{\rm DG}$ towards the CMZ, despite its low star formation activity, suggests that, in that particular region of our Galaxy, high-density gas is not the bottleneck for star formation.
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Contributor : Marie-Paule Pomies <>
Submitted on : Monday, December 7, 2015 - 11:53:46 AM
Last modification on : Friday, April 5, 2019 - 8:23:59 PM

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T., Csengeri, A., Weiss, F., Wyrowski, K. M., Menten, J. S., Urquhart, et al.. The ATLASGAL survey: distribution of cold dust in the Galactic plane. Combination with Planck data. Astronomy and Astrophysics - A&A, EDP Sciences, 2016, 585, pp. id.A104. ⟨10.1051/0004-6361/201526639⟩. ⟨hal-01238902⟩



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