2 / 9 / 2013

Hi Michael,

thanks for your email, back to our conversation :)

And thanks for being patient waiting for my jet lag to fade. The lobes do not stay on a plane (they are not 2D), you can regard them as an hourglass centred at the Galactic Centre. Referring to the Nature paper Figures - I see you had the chance to look at - the radio lobes we see are narrow close the Galactic plane and come up (and down) as a cone. Then they come up vertically up to the top where they bend right. What you see is the view from Earth, so, the right bend is away from us by 90 degree. In your figure, if we are along z (on the near side), they bends along X. So, 90 degrees from us. They might have a component along Y, it is hard to say how much, if any, because we see a projection on the plane of the sky. And, if any, it should be away from us. However, most of it is along X.

Always from Figure 1 and 2 of the Nature paper, you can see how the edges of our radio Lobes compare to the Fermi Bubbles. The edges we report there are the real edges, not those of the artistic representation. The edges are the same, except that the radio lobes exceed the Fermi Bubbles at the top. Why they exceed? They are two different type of emissions, radio and gamma, produced by particles (electrons) at different energy. In particular, those emitting in gamma last shorter than the radio emitting one, so that they have had not the time to reach the same elevations but stopped emitting earlier.

And now your major question: Did they look the same on the Winter Solstice of last year? Yes. they did.

From the speed we measure, the outflows take tens of Millions of years to reach the top of the Lobes. So that modifications in 2-3 year times are not appreciable from Earth, If I would repeat the observations today I would see the same image. So, we are talking about structures that take millions of years to form and they look the same in 2-3 year time.

And that is why we could map them with observations spread in 2 and a half years: they looked the same and the beginning and the end of the observations.

Why so long time to collect data? Yes, it is because of the huge area of the sky we observed. It has been a half of the entire sky and with a big radio telescope it takes long time to complete such observations. And the telescope was not dedicated all time to us, it is an observatory and the project was sharing the time with other projects in those two and a half years. Then processing the data and analysing the results takes time. Finally writing the paper and going through the peer review and publication process takes time. The picture came out concurrently with the publication on the journal. These time scales are typical in astronomical research, especially for so large projects. I was the first to be impatient to see the paper published and the result announced!

Hope this can help and answer your questions Michael.