H I shells in the outer Milky Way

Free access article

Issue		A&A Volume 437, Number 1, July I 2005


Page(s)		101 - 112
Section		Galactic structure, stellar clusters and populations
DOI		http://dx.doi.org/10.1051/0004-6361:20034389

A&A 437, 101-112 (2005)
DOI: 10.1051/0004-6361:20034389

H I shells in the outer Milky Way

S. Ehlerová and J. Palous

Astronomical Institute, Academy of Sciences of the Czech Republic, Bocní II 1401, 141 31 Prague 4, Czech Republic
e-mail: sona@ig.cas.cz

(Received 24 September 2003 / Accepted 7 March 2005)

Abstract
We present results of a method for an automatic search for $\ion{H}{i}$ shells in 3D data cubes and apply it to the Leiden-Dwingeloo $\ion{H}{i}$ survey of the northern Milky Way. In the 2nd Galactic quadrant, where identifications of structures are not substantially influenced by overlapping, we find nearly 300 structures. The Galactic distribution of shells has an exponential profile in the radial direction with a scale length of $\sigma_{{\rm gsh}} = 3$ kpc. In the z direction, one half of the shells are found at distances smaller than 500 pc. We also calculate the energies necessary to create the shells: there are several structures with energies greater than $10E_{{\rm SN}}$ but only one with an energy exceeding $100E_{{\rm SN}}$ . Their size distribution, corrected for distance effects, is approximated by a power-law with an index $\alpha = 2.1$ . Our identifications provide a lower limit to the filling factor of shells in the outer Milky Way: $f_{{\rm 2D}} = 0.4$ and $f_{{\rm 3D}} = 0.05$ .

Key words: ISM: bubbles -- ISM: structure -- Galaxy: structure -- methods: data analysis

SIMBAD Objects in preparation
Tables at the CDS

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