3rd Blog Post: HST Grism

This week has been mainly trying to make our data more accurate. We started off by matching the spectral resolution of KECK (a ground based telescope in Hawaii) and HST. This involved changing the smoothing factor in the data (essentially adding up the flux in adjacent pixels) to make any peaks stand out more and reduce the background noise. However, if this is done to the extreme, then it massively reduces the accuracy and precision. We have taken data from KECK, and altered the smoothing to make it have the same apparent resolution as the Hubble data. This was done on a second galaxy (BR3), to get the same spectral resolution as for Hubble so we can compare the two galaxies directly, as well as seeing what emission lines in BR3 (and CR7 using KECK data) are real, which are from the atmosphere, and which should be seen in CR7, but aren’t due to noise.

Lowering smoothness of BR3 data from KECK, increasing resolution of the spectra.

We also needed to convert the flux to luminosity, since CR7 is much further away than BR3, and so will have generally lower fluxes, despite the galaxies being similarly luminous.

We have also had a visitor to the university this week. Alyssa Drake works with MUSE at the Observatoire de Lyon in France, and gave us a talk on the “a-muse-ing” project she is doing there. She is looking at what caused the reionisation of the universe a few billion years ago by looking at Lyman-α haloes of galaxies from that era.

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