The HI/OH/Recombination line survey of the inner Milky Way (THOR): Survey overview and data release 1

Beuther, H. and Bihr, S. and Rugel, M. and Johnston, K. and Wang, Y. and Walter, F. and Brunthaler, A. and Walsh, A.J. and Ott, J. and Stil, J. and Henning, Th. and Schierhuber, T. and Kainulainen, J. and Heyer, M. and Goldsmith, P.F. and Anderson, L.D. and Longmore, S.N. and Klessen, R.S. and Glover, S.C.O. and Urquhart, J.S. and Plume, R. and Ragan, S.E. and Schneider, N. and McClure-Griffiths, N.M. and Menten, K.M. and Smith, R. and Roy, N. and Shanahan, R. and Nguyen-Luong, Q. and Bigiel, F. (2016) The HI/OH/Recombination line survey of the inner Milky Way (THOR): Survey overview and data release 1. Astronomy and Astrophysics, 595 . A32. ISSN 0004-6361. E-ISSN 1432-0746. (doi: (Full text available)

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Context. The past decade has witnessed a large number of Galactic plane surveys at angular resolutions below 20′′. However, no comparable high-resolution survey exists at long radio wavelengths around 21 cm in line and continuum emission. Aims. We remedy this situation by studying the northern Galactic plane at ~20′′ resolution in emission of atomic, molecular, and ionized gas. Methods. Employing the Karl G. Jansky Very Large Array (VLA) in the C-array configuration and a large program, we observe the HI 21 cm line, four OH lines, nineteen Hnα radio recombination lines as well as the continuum emission from 1 to 2 GHz in full polarization over a large part of the first Galactic quadrant. Results. Covering Galactic longitudes from 14.5 to 67.4 deg and latitudes between ± 1.25 deg, we image all of these lines and the continuum at ~20′′ resolution. These data allow us to study the various components of the interstellar medium (ISM): from the atomic phase, traced by the HI line, to the molecular phase, observed by the OH transitions, to the ionized medium, revealed by the cm continuum and the Hnα radio recombination lines. Furthermore, the polarized continuum emission enables magnetic field studies. In this overview paper, we discuss the survey outline and present the first data release as well as early results from the different datasets. We now release the first half of the survey; the second half will follow later after the ongoing data processing has been completed. The data in fits format (continuum images and line data cubes) can be accessed through the project web-page. Conclusions. The HI/OH/Recombination line survey of the Milky Way (THOR) opens a new window to the different parts of the ISM. It enables detailed studies of molecular cloud formation, conversion of atomic to molecular gas, and feedback from Hii regions as well as the magnetic field in the Milky Way. It is highly complementary to other surveys of our Galaxy, and comparing the different datasets will allow us to address many open questions.

Item Type: Article
Uncontrolled keywords: stars: formation / ISM: clouds / ISM: structure / ISM: kinematics and dynamics / ISM: magnetic fields / stars: evolution
Divisions: Faculties > Sciences > School of Physical Sciences
Depositing User: James Urquhart
Date Deposited: 20 Jan 2017 13:54 UTC
Last Modified: 03 Aug 2018 14:14 UTC
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