Fitting infrared ice spectra with genetic modelling algorithms. Presenting the ENIIGMA fitting tool

Abstract

Context. A variety of laboratory ice spectra simulating different chemical environments, ice morphology as well as thermal and energetic processing are demanded to provide an accurate interpretation of the infrared spectra of protostars. To answer which combination of laboratory data best fit the observations, an automated statistically-based computational approach becomes necessary. Aims. To introduce a new approach, based on evolutionary algorithms, to search for molecules in ice mantles via spectral decomposition of infrared observational data with laboratory ice spectra. Methods. A publicly available and open-source fitting tool, called ENIIGMA (dEcompositioN of Infrared Ice features using Genetic Modelling Algorithms), is introduced. The tool has dedicated Python functions to carry out continuum determination of the protostellar spectra, silicate extraction, spectral decomposition and statistical analysis to calculate confidence intervals and quantify degeneracy. As an assessment of the code, several tests were conducted with known ice samples and constructed mixtures. A complete analysis of the Elias 29 spectrum was performed as well. Results. The ENIIGMA fitting tool can identify the correct ice samples and their fractions in all checks with known samples tested in this paper. Concerning the Elias 29 spectrum, the broad spectral range between 2.5-20 $\mu$m was successfully decomposed after continuum determination and silicate extraction. This analysis allowed the identification of different molecules in the ice mantle, including a tentative detection of CH${}_3$CH${}_2$OH. Conclusions. The ENIIGMA is a toolbox for spectroscopy analysis of infrared spectra that is well-timed with the launch of the James Webb Space Telescope. Additionally, it allows for exploring the different chemical environments and irradiation fields in order to correctly interpret astronomical observations.

arXiv comment23 pages, 19 figures, 3 tables. Accepted for publication in A&A

References in corpus (55)

• SciPy 1.0--Fundamental Algorithms for Scientific Computing in Python
• Array Programming with NumPy
• Observations of the Icy Universe
• The Spitzer ice legacy: Ice evolution from cores to protostars
• The absence of crystalline silicates in the diffuse interstellar medium
• The evolution of amorphous hydrocarbons in the ISM: dust modelling from a new vantage point
• The c2d Spitzer Spectroscopic Survey of Ices Around Low-Mass Young Stellar Objects: I. H2O and the 5-8 um Bands
• Consistent dust and gas models for protoplanetary disks. I. Disk shape, dust settling, opacities, and PAHs
• The global dust modelling framework THEMIS (The Heterogeneous dust Evolution Model for Interstellar Solids)
• The c2d Spitzer spectroscopic survey of ices around low-mass young stellar objects II: CO2
• The Composition and Distribution of Dust Along the Line of Sight Towards the Galactic Center
• A 3-5 micron VLT spectroscopic survey of embedded young low mass stars I: Structure of the CO ice
• The c2d Spitzer spectroscopy survey of ices around low-mass young stellar objects, III: CH4
• Mapping ices in protostellar environments on 1000 AU scales: Methanol-rich ice in the envelope of Serpens SMM 4
• Atom addition reactions in interstellar ice analogues
• The c2d Spitzer Spectroscopic Survey of Ices Around Low-Mass Young Stellar Objects. IV. NH3 and CH3OH
• Observational $5-20\mu$m Interstellar Extinction Curves Toward Star-Forming Regions Derived from Spitzer IRS Spectra
• Ices in the edge-on disk CRBR 2422.8-3423: Spitzer spectroscopy and Monte Carlo radiative transfer modeling
• Ice and Dust in the Quiescent Medium of Isolated Dense Cores
• New Three Micron Spectra of Young Stellar Objects with H_2O Ice Bands
• Gaia-DR2 confirms VLBA parallaxes in Ophiuchus, Serpens and Aquila
• Desorption of CO and O2 interstellar ice analogs
• A non-energetic mechanism for glycine formation in the interstellar medium
• Origin of the 6.85 micron band near young stellar objects: The ammonium ion (NH4+) revisited
• Spitzer IRS Observations of Class I/II Objects in Taurus: Composition and Thermal History of the Circumstellar Ices
• Variations on a theme - the evolution of hydrocarbon solids: I. Compositional and spectral modelling - the eRCN and DG models
• Radiolysis of ammonia-containing ices by energetic, heavy and highly charged ions inside dense astrophysical environments
• Consistent dust and gas models for protoplanetary disks III. Models for selected objects from the FP7 DIANA project
• Spitzer Observations of CO2 Ice Towards Field Stars in the Taurus Molecular Cloud
• Infrared spectra of complex organic molecules in astronomically relevant ice matrices. I. Acetaldehyde, ethanol, and dimethyl ether
• The Environment and Nature of the Class I Protostar Elias 29: Molecular Gas Observations and the Location of Ices
• The 9.7 and 18 um silicate absorption profiles towards diffuse and molecular cloud lines-of-sight
• ALMA observations of the kinematics and chemistry of disc formation
• Physical and chemical fingerprint of protostellar disc formation
• Infrared Spectroscopic Survey of the Quiescent Medium of Nearby Clouds: I. Ice Formation and Grain Growth in Lupus
• Infrared spectroscopy of HCOOH in interstellar ice analogues
• The Composition of Interstellar Grains Toward Zeta Ophiuchi: Constraining the Elemental Budget Near the Diffuse-Dense Cloud Transition
• A survey of H${}_2$O, CO${}_2$ and CO ice features towards background stars and low mass YSOs using AKARI
• Radiation thermo-chemical models of protoplanetary discs. III. Impact of inner rims on Spectral Energy Distributions
• VLT-ISAAC 3-5 micron spectroscopy of embedded young low-mass stars. III. Intermediate-mass sources in Vela
• Cold gas as an ice diagnostic toward low mass protostars
• The Nature of Carbon Dioxide Bearing Ices in Quiescent Molecular Clouds
• Sulfur-Bearing Species Tracing the Disk/Envelope System in the Class I Protostellar Source Elias 29
• Properties of protostars in the Elephant Trunk globule IC 1396A
• Linking ice and gas in the Serpens low-mass star-forming region
• Fitting infrared ice spectra with genetic modelling algorithms. Presenting the ENIIGMA fitting tool
• Low temperature optical properties of interstellar and circumstellar icy silicate grain analogues in the mid-infrared spectral region
• Two dimensional ice mapping of molecular cores
• Computational modeling of the class I low-mass protostar Elias 29 applying optical constants of ices processed by high energy cosmic ray analogs
• The use of genetic algorithm to model protoplanetary discs
• Linking ice and gas in the Lambda Orionis Barnard 35A cloud
• Analyzing the Low State of EF Eridani with Hubble Space Telescope Ultraviolet Spectra
• Quantifying the Carbon Abundances in the Secondary Stars of SS Cygni, RU Pegasi, and GK Persei
• Fitting of dust spectra with genetic algorithms - I. Perspectives & Limitations
• The role of external FUV irradiation in the survival of astrophysical ices in Elias 29

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• CORINOS I: JWST/MIRI Spectroscopy and Imaging of a Class 0 protostar IRAS 15398-3359
• LIDA - The Leiden Ice Database for Astrochemistry
• Laboratory and Computational Studies of Interstellar Ices
• Hunt for complex cyanides in protostellar ices with JWST: Tentative detection of CH${}_3$CN and C${}_2$H${}_5$CN
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