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Rotation curves and galactic dynamics

Rotation curves of galaxies remain one of the most reliable ways to study the matter content of galaxies and derive the dark matter mass and distribution. The field has a long history starting from the Seventies with pioneering work on nearby galaxies using the 21-cm line of neutral hydrogen (HI). Extended HI rotation curves have provided the first definitive evidence for the existence of dark matter in galaxies.

Today we can derive the kinematics of local disc galaxies with great precision and extend this study at high redshift using both IFUs, such as KMOS and MUSE and interferometers as ALMA. However, high-z galaxies are distant and faint and thus our data suffer for low signal to noise and low angular resolution.

Therefore the methods to derive robust kinematics from these galaxies have to overcome these difficulties. Enrico Di Teodoro and I have designed a software to achieve these goals: 3D-Barolo. This software creates an artificial 3D realisation of a tilted ring model and fits it to an observed data cube. 3D-Barolo has been used with a myriad of different datacubes including the HI emission line with the VLA, the GMRT, and the WSRT; CO/[CI]/[CII] with ALMA at high-z, CO with ALMA and VLA at z=0, Halpha/[OII]/[OIII] with KMOS and MUSE, simulated galaxies produced with Gadget (Apostle project) and RAMSES. 

It is reliable, quick and easy to use! 


a) A comparison between high-res (Very Large Array, VLA) and low-res (Effelsberg) HI line-of-sight velocity and velocity dispersion fields of the nearby galaxy NGC 3198. b) The performance of our software 3DBarolo applied to the Effelsberg data (red triangles) in recovering the true rotation curve (blue points obtained from the high resolution VLA data) and the intrinsic velocity dispersion of NGC 3198, compared to the values one obtains using 2D maps (green diamonds).

Data (black) and 3D-Barolo models (red) of the same galaxy observed at very different angular resolutions with the VLA interferometer (left) and with the Effelsberg single dish (right). When hoovering you see the various channel maps (HI emission at different radial velocities) of the datacubes overlaid with the tilted-ring best fit model produced by 3D-Barolo.

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