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tokens: with data from observations taken from Pfuhl et al. ( 2015 ). Figure 7. The integrated Br γ luminosity as a function of time. The solid blue line results from our simulations while the points are the observed data taken from Pfuhl et al. ( 2015 ) with a 1σ error bar. As the cloud travels towards the SMBH, its volume decreases due to tides and hence its recombination rate and total emission increase. During pericentre passage, gas that passes through pericentre has its density greatly increased due to the vertical collapse. While the recombination rate for a fully ionized gas greatly increases during pericentre passage, the fact that the cloud is UV starved and that its total ionization rate is regulated by the background UV flux limit the increase in the Br γ emission to a mere doubling. This translates to roughly a doubling of the emission that is now limited by the UV flux. After pericentre passage, the emission decreases as the surface area of the cloud decreases due to the evolution of the cloud under tides. Our simulations also allow us to create mock PV diagrams that can be compared with observations. We create mock data cubes in the same manner as in Schartmann et al. ( 2015 ) using pixels of size 12.5 mas and 70 km s −1 . Fig. 8 shows the PV diagram for several different epochs before, during and after pericentre passage. There is good agreement between the observations before pericentre passage and our simulations. Figure 8. PV diagrams of the G2 cloud. The left-hand column is the observational data taken from Plewa et al. ( 2017 ) while the right-hand column are mock observations created from the simulations. The plots represent the epochs 2012.2, 2013.4, 2014.4, 2015.3 and 2016.4. 8 DISCUSSION We have presented a detailed model combining analytical arguments along with numerical simulations that successfully reproduce the observed Br γ emission. By utilizing the reduced diffusion of the moving mesh scheme along with high resolution and actively cooling the gas, we were able to simulate previously unnoticed physical phenomena. The tidal force combined with the efficient cooling collapses the vertical axis of the cloud during pericentre passage. Although the collapse produces a significant amount of ionizing radiation, due to the thinness of the cloud, most of the ionizing photons escape and only a small fraction of them end up ionizing neutral gas. The Br γ emission is regulated by the external UV flux from nearby massive stars. We find that the emission is UV starved, most of the gas is neutral during pericentre passage. This is true even for our enhanced ionizing background, which is 3.6 times larger than the Martins et al. ( 2006 ) rate. Motivated by the observed duration of simultaneous blueshifted and redshifted Br γ emission at pericentre passage, we chose to start our orbital plane simulation with a cloud that has an aspect ratio of 4, which is consistent with the observations due to viewing angles. If the elongated cloud is