Extra data M82 research

Welcome. This page is meant as an addition to a poster located at the Leiden University. The poster shows the results of our research project on the subject of star formation in M82's jets. On this page, you can find more information about how the data was acquired, the reduction process and other methods that were used to carry out this research project. Some of the figures contain a link to our data.

Our data was obtained with the Isaac Newton Telescope at the Roque de los Muchachos Observatory on La Palma. The raw data can be found here. We made exposures with the Wide Field Camera using the Stromgren B, Stromgren V, Sloan Gunn r and narrowband Hα filters. The three nights of 18-20 March we had great observing conditions with seeing as low as 1". The full moon however, brightened the night sky and therefore lowered the signal-to-noise ratio of the B-exposures. Due to bad weather, the second duo only observed during the night of the 26th of March with less than perfect conditions. The images shown below were calibrated with Theli version 2.10.5.

Combining these exposures, we created the following coloured image of M82.

Hα emits at a wavelength of λ= 6562.8 Å. However, the Hα filter has a width of 95 Å, which means that the Hα data contains part of the red continuum. Thus the red image must be scaled and subtracted from the Hα image. To find the right scaling, the r and Hα pixel-counts were plotted against each other in order to find the slope with a robust fit. This fit is shown in figure 6.

The red image was then scaled by 0.064 and subtracted from Hα. The result is a pure Hα image as seen in Figure 7.

Since the Hα in this image is very clear, we were able to select 55 regions in M82's jets. The selected regions are also shown in figure 7. We used these regions to calculate the flux in the different sections of the jets in the B and Hα filters. By comparing the fluxes in these filters with each other, we noticed that most of the Hα-emitting regions showed even stronger B radiation. This relation can be seen in figure 8. We then did the same thing for the Signal-to-noise in both filters, as seen in figure 9.

With this information about the fluxes in B and Hα we were confident that the at least some regions have star formation. We constructed the following CMD which is also on the poster. We determined the magnitudes of all the regions with a reference star in our image: “GPM 149.400354+69.688401”, with a known magnitude from the Simbad database. The magnitude convention might not be the best with this method, so we should have selected more reference stars to give a more accurate magnitude.

We don’t think the research ends here. There is more to be known about these jets with possible star formation. As mentioned, a better zeropoint magnitude could be obtained. With further research with our data we could find a star formation rate in solar masses per year per parsec squared for regions within the jets. We could also compare the jet regions in M82 with those in NGC4861, a galaxy we also observed on La Palma.