Late night dinners are
Nesecesary when day
Hours go away
So far I have been writing a cleaner version of the bias sub/flatfielding code so that it runs with no issues when applied to the test data set. So far things are running but the counts I am getting were initially puzzling but after some inspection makes some sense. The raw frames on average have a lower pixel count value than the bias frames, so for the bias subtracted science frames I was getting a decent amount of negative values. After considering this however I did some analysis on the subtracted overscans and was getting some strange results from my tests. I have included a plot below. The central value is 120 not zero which is concerning. I will do some further investigation into this.
Looks like there could be something wrong with the scaling of the master bias, and a separate issue with flatfielding. I might have blindly used some old code so hopefully that is a quick fix. Otherwise I still have some digging to do.
The Nakajima et al 1995 paper has been interesting thus far. It’s cool that this work came out of the Palomar observatory at Caltech, which was discussed in our Giant Telescopes reading. An initial question I have is as to why the difficulty of detecting energy from gravitational contraction makes it hard to find brown dwarfs? What is the energy from this process a diagnostic of that helps us find BDs?
The team sets out to look for stars with a luminosity less than 10^-4 solar luminosities which correspond to an age of 10^9 years. BDs can be detected with analysis of proper motions in relation to a companion star. That is how the BD being discussed in this work, G1229b, was discovered. This arises the question for me: why is it that a star’s kinematics lead it to be classified as a ‘young disk star?’
After a meeting with Kim interpreting the right plot is a little easier. Simply put it is a spectrum plotted in frequency space. The higher the frequency the bluer we get. The solid curve is the BD being discussed in the paper and the other two are low mass M-dwarf field objects. As we can see there is a systematic shift in luminosity space as we move to the less massive objects. We can also see the spectrum fall off quite a bit as we move to higher energy wavebands. It is also below some threshold that the field stars are above. Further indicating it’s low mass not adequate enough for hydrogen burning. If we wanted we could put the panels of the left plot on top of their corresponding locations in frequency space as those panels are different images of the BD in different wavelengths. It seems like the group never takes real measurements of the mass or luminosity, but infer from models. As a supplementary presentation I will also discuss this paper that has cited Nakajima+1995: https://ui.adsabs.harvard.edu/abs/2009AJ….137….1F/abstract
In terms of plans for data reduction the coming week I hope to iron out the issues that was discussed in the OOC meeting and apply it broadly to the whole data set. Ideally it will run top to bottom in every data directory no problem, realistically this probably will not be the case. I expect my week in data reduction will be a lot of debugging and polishing the pipeline for more seamless use. Besides that I’ve only started to wrap my head around differential photometry and the procedure that it requires. Conceptually it makes sense and is maybe easier/more dependable than the calibration photometry that we did in 337? I guess that would be a product of the kind of information we’d like to tease out of our data. Regardless, I can foresee what the future looks like photometry wise. Things are sorting now though, which is definitely progress. I’m confused because the bias sub/flat routines work fine for the actual data but are behaving strange for this test sample. Hopefully the problems will be solved by tomorrow.
Owen H. ASTRO-341 Research Blog 