Thomas Cross
A large-scale approach to modelling Biosignatures: First Steps
by Thomas Cross , Marco Pignatari, David M. Benoit and Brad K. Gibson
E.A. Milne Centre for Astrophysics, University of Hull
For this poster I will be presenting the approaches taken to produce synthetic spectra for molecules believed to be biosignatures. In astrochemistry, biosignatures describe a group of molecules which could be produced by life and therefore act as an indication of it. Naturally, by being able to identify these molecules it will be possible to screen exoplanets for the possibility of harbouring life.
Recently, Seager, Bains and Petkowski (2016) produced a catalogue of possible biosignatures, which totalled above 14,000 molecules. There are groups such as the ExoMol group which model these molecules at extremely high precision. However, due to the large number of molecules, a high precision method would take an unreasonable amount of time and therefore a faster means of producing spectra is required. The work shown within is designed to be quick and produce data for the full rovibronic spectrum rather than selected bands. I will show that anharmonic corrections are needed to be able to simulate qualitatively correct ro-vibrational transitions. In my method, this is done by implementing TOSH, transition optimised shifted hermites, which was first detailed by Lin, Gilbert and Gill (2007). Finally I will be presenting my latest results using this analytical anharmonic approach.
The Plain-text Document
SLIDE 1: Title Card
On the left hand side there is the following text.
Authors: Thomas Cross, David Benoit, Brad Gibson and Marco Pignatari
Email: T.Cross-2019@hull.ac.uk
Institution: University of Hull
Quick access links are also provided for each slide.
This slide includes an abstract on the right hand side which has the following key points:
Poster presents work towards modelling biosignatures, using our own code: Prometheus.
The modeling has only been done for diatomics (molecules made up of two atoms).
Prometheus makes use of a theory called Transition-Optimised Shifted Hermite.
Results show Prometheus’ results are a better approximation than the basic harmonic method, when compared to results from HITRAN.
HITRAN is an acronym for a high-resolution transmission molecular absorption database.
This slide has a section below the abstract named: “FOCUS MOLECULES”. This section contains two bullet points, one for CO and one for O2 In the bottom right corner there is a figure of the Orion Nebula, labelled figure 1.
SLIDE 2: Introduction and Methodology
This slide has a two column format. This slide discusses both the introduction and methodology. THe introduction sections are denoted by a light blue heading.
It has 2 sections, with the headings: “INTRODUCTION PT.1: BIOSIGNATURES”, and “INTRODUCTION PT.2: PROMETHEUS/ANALYTICAL ANHARMONIC APPROACH”.
For the method, the headings are a light purple colour. It has four sections with the headings; “METHOD PT.1: POTENTIAL ENERGY CURVE”, “METHOD PT.2: ROTATIONAL CONSTANTS”, “METHOD PT.3: SPECTRA” and “METHOD PT.4: COMPARISONS”.
Method Pt 2. Contains the equation for calculating the value for the rotational constant.
Method 4. Contains 2 bullets points describing the data sets the Prometheus results will be compared to; HITRAN2016 and HARMONIC.
SLIDE 3: Results and Conclusions
Figure 2. This is the top figure on the left hand side of the page. It shows the comparison of the spectra produced for CO. On the topside we have the spectrum produced by Prometheus, denoted by the colour red, and the harmonic method, coloured dark cyan. On the bottom is the spectrum produced by the HITRAN2016 data release, which is coloured black.
In figure 2. Prometheus and HITRAN2016 appear in good agreement with each other, both having similar shapes and being located in the same region. The harmonic method however is displaced to the right. The text on the right simply discusses these results and evaluates the accuracy of the Prometheus spectrum when compared to the other spectrums
Below this we have the same layout for O2 but with the format horizontally flipped, with figure 3., being located on the right hand side. The discussion is on the left hand side of this figure.
Figure 3. Highlights the issues with the harmonic method as the spectrum originating quite the distance away from the Prometheus and HITRAN2016 data. However Pormetheus has some difficulty modeling all of the structures shown by the HITRAN2016 data.
SLIDE 4: Conclusions and References
This slide has a two column format. Contains 4 segments.
The first is titled “ADDITIONAL O2 DISCUSSION”, which discusses figure 3. in further detail.
The second is titled ‘KEY TAKEAWAYS” and discusses the conclusion the poster has shown. This is mainly that the Prometheus method is a better approximate spectra, however there are still caveats to this method. The section ends with three bullets which detail the next steps.
The next segment is titled “ACKNOWLEDGEMENTS” and references the help from the E.A. Milne Centre and the STFC.
The final segment, titled “REFERENCES”, contains the references used within the poster.