William Balmer
The Bleeding Edges of Direct Imaging with JWST

Thanks so much for inviting us early career folks to come and give talks.
I'm William Balmer.
I'm a fourth year PhD student at Johns Hopkins.
My advisor is Laurent Pueyo and I'm excited to talk to you today about sort of the bleeding wedge we call it. But but more broadly, Coronography on JWST.
There we go.
So just to very briefly motivate in the broadest terms possible, I'll state without proof that understanding life and and our own solar system in the broadest context means understanding giant planets.
How they form, how they evolve dynamically and you know how they change in in frequency as functions of various terms.
And this will clue us into, you know, how usual or unusual our own solar system is.
So giant planets can form theoretically and you know, sort of two broad camps.
Bottom up from, you know, the accretion of planetesimals, or top down from the direct collapse of the gas in the part of planetary disk. And in theory these should result in observably different kinds of planets, although that hasn't necessarily panned out too within our observational tolerances in direct.
Imaging, yet. So in general, we believe that for instance, core accretion should result in planets that are metal enriched compared to their stars.
But something like disk instability would result in.
Relatively stellar abundances.
So this is maybe a a more planet like tautology planet and a more brown dwarf like planet.
Motivating using jet OST.
We want to go into the mid infrared because it gives us access to both generally colder planets, meaning we can probe those frequencies of planets as a function of mass, but also new molecules that we didn't have access to on the ground because of either tolerant absorption or.
Just wavelength grass, right?
So relative to the typical direct imaging in you know 8 to 10m class telescopes on the ground, we get a really huge boost in wavefront stability.
We lose in the actual telescope diameter and we lose in Lambda bit, so it wasn't clear before launch whether we we would be able to actually image the majority of directly image planets that have been imaged from the ground with JOST.
On the telescope, we have a variety of instruments.
We have these band limited chronographs with nercam and then we have a four quadrant phase mask with Miri and I'll be talking a lot about the bar mask chronographs which have been very underutilized. But we've done a lot of work with GTO.
Time to try and sort of prove to people that there is a really great trade space with these instruments.
So just to start here was the the first few months of observations. This is the ERS results from Aaron Carter at all and this is showing the classic like you know direct imaging poster child planet hundreds of AU.
Many times the mass of Jupiter we get a nice clear detection. With this round mask, and with this four quadrant phase mask.
But if you notice within this contrast curve that we we published these nercam band limited chronographs aren't hard edged.
So they still have throughput at separations interior to their inner working angle, which means that with enough integration time and with a stable enough telescope.
And that's really the key we should be able to image planets that are interior to the inner working angle of the chronograph.
So this sort of motivated some work that Kyle, France and then I led in early of this past year, this plan AFL up was discovered from the ground.
And we thought, you know, when it was published, we wouldn't be able to catch it with CDC. It's at a point where it has a 7% chronographic throughput with the nircam round mask.
But it turns out that the telescope is stable enough that you can take a picture of the system with this instrument.
And get a nice clear detection here and extend the wavelength grasp of your observations.
Get a whole new set of information about the carbon dioxide content in in the planet's atmosphere.
So this motivates, you know, if if we wanted to go back and re observe AFL up with more filters, how might we get better throughput?
We try to use this this bar mask which has this preferential position angle, but in principle better throughput, so the trade off is you lose in raw contrast by letting more stellar light leak through.
But you trust the stability of the the telescope to allow you to remove all that Starlight and post processing anyways, and you get better throughput on the planet.
So we took a look at a couple of classic directly image systems.
This is 51 area and this is not showing up.
There we go.
This is the closest planet yet imaged, with JWST at 280 milliac seconds.
This was super exciting to see.
It's one of the coldest planet that we knew pre Jadavisti and here is the classic HR8799.
Here's the three outer planets, and if you squint, you can see the inner one.
But I did you a favor and subtracted out the.
Model of the outer three, so you could really clearly see our detection of the innermost planet.
But it turns out that you can actually use a classical deconvolution algorithm too.
So if you do an iterative deconvolution, you get these collections of four pixels, and then you can re smooth those and see all four planets in the same figure.
So yeah, this is our contrast curve.
I won't spend too much time about it.
The Black Line is better than the dotted line. That's great.
It means that a planet like like 51 area or or 8799 E which you wouldn't be able to detect that you know 5 Sigma with the round mask you can detect with this mode at greater than 5 Sigma.
But really, what's exciting about this is that access to the three to five Micron range.
And so this is very similar to what people are doing with transiting planets, looking at the CO2 feature at 4.3 microns.
But we have access to that same filter, that same feature with these filters.
So I'm showing on the X axis here.
A C O2 color and then ACO color and the sort of field brown dwarfs follow a stellar and and sub stellar metallicity sequence, whereas the 8799 planets are statistically significantly enhanced in CO2 and in there for metallicity, potentially indicating that they formed V.
Some core accretion framework, which is a pretty fun result.
So I'll just leave up my takeaways and thanks for your time.
Let me call a. Meanwhile the next speaker.
Clarissa, can you come up and yes, please stay there. And any questions to.
William.
I guess you have already considered how many other exoplanets can you.
Yeah, that's a great. That's a sneaky proposal we submit.
But yes.
You then want to give it away, you know.