Emission Line Predictions for Mock Galaxy Catalogues: a New Differentiable and Empirical Mapping from DESI

Abstract

We present a simple, differentiable method for predicting emission line strengths from rest-frame optical continua using an empirically-determined mapping. Extensive work has been done to develop mock galaxy catalogues that include robust predictions for galaxy photometry, but reliably predicting the strengths of emission lines has remained challenging. Our new mapping is a simple neural network implemented using the JAX Python automatic differentiation library. It is trained on Dark Energy Spectroscopic Instrument Early Release data to predict the equivalent widths (EWs) of the eight brightest optical emission lines (including H$\alpha$, H$\beta$, [O II], and [O III]) from a galaxy's rest-frame optical continuum. The predicted EW distributions are consistent with the observed ones when noise is accounted for, and we find Spearman's rank correlation coefficient ${\rho }_s>0.87$ between predictions and observations for most lines. Using a non-linear dimensionality reduction technique (UMAP), we show that this is true for galaxies across the full range of observed spectral energy distributions. In addition, we find that adding measurement uncertainties to the predicted line strengths is essential for reproducing the distribution of observed line-ratios in the BPT diagram. Our trained network can easily be incorporated into a differentiable stellar population synthesis pipeline without hindering differentiability or scalability with GPUs. A synthetic catalogue generated with such a pipeline can be used to characterise and account for biases in the spectroscopic training sets used for training and calibration of photo-$z$'s, improving the modelling of systematic incompleteness for the Rubin Observatory LSST and other surveys.

arXiv comment17 pages, 8 figures, 1 table. Published in MNRAS

References in corpus (63)

• XGBoost: A Scalable Tree Boosting System
• SciPy 1.0--Fundamental Algorithms for Scientific Computing in Python
• Array Programming with NumPy
• Stellar population synthesis at the resolution of 2003
• The Sloan Digital Sky Survey: Technical Summary
• The Wide-field Infrared Survey Explorer (WISE): Mission Description and Initial On-orbit Performance
• The Seventh Data Release of the Sloan Digital Sky Survey
• The Astropy Project: Sustaining and Growing a Community-oriented Open-source Project and the Latest Major Release (v5.0) of the Core Package
• The Host Galaxies of AGN
• The Origin of the Mass--Metallicity Relation: Insights from 53,000 Star-Forming Galaxies in the SDSS
• LSST: from Science Drivers to Reference Design and Anticipated Data Products
• Theoretical Modeling of Starburst Galaxies
• The Host Galaxies and Classification of Active Galactic Nuclei
• The James Webb Space Telescope
• Overview of the DESI Legacy Imaging Surveys
• Normalizing Flows: An Introduction and Review of Current Methods
• UniverseMachine: The Correlation between Galaxy Growth and Dark Matter Halo Assembly from z=0-10
• The propagation of uncertainties in stellar population synthesis modeling III: model calibration, comparison, and evaluation
• The Dark Energy Camera
• zCOSMOS: A Large VLT/VIMOS redshift survey covering 0 < z < 3 in the COSMOS field
• Modeling the Panchromatic Spectral Energy Distributions of Galaxies
• The Connection between Galaxies and their Dark Matter Halos
• Initial Performance of the NEOWISE Reactivation Mission
• The DEEP2 Galaxy Redshift Survey: Design, Observations, Data Reduction, and Redshifts
• Stellar Population Inference with Prospector
• Dust Attenuation Curves in the Local Universe: Demographics and New Laws for Star-forming Galaxies and High-redshift Analogs
• The Mass-Metallicity Relation with the Direct Method on Stacked Spectra of SDSS Galaxies
• PRIMUS: Constraints on Star Formation Quenching and Galaxy Merging, and the Evolution of the Stellar Mass Function From z=0-1
• Alternative diagnostic diagrams and the "forgotten" population of weak line galaxies in the SDSS
• Overview of the Instrumentation for the Dark Energy Spectroscopic Instrument
• Nebular Continuum and Line Emission in Stellar Population Synthesis Models
• SDSS IV MaNGA - Spatially resolved diagnostic diagrams: A proof that many galaxies are LIERs
• Spectral and Photometric Evolution of Young Stellar Populations: the Impact of Gaseous Emission at Various Metallicities
• The Quijote simulations
• The Main Sequence of star-forming galaxies across cosmic times
• The nature of LINER galaxies: Ubiquitous hot old stars and rare accreting black holes
• The impact of nebular emission on the ages of z~6 galaxies
• DESI Bright Galaxy Survey: Final Target Selection, Design, and Validation
• An Atlas of Galaxy Spectral Energy Distributions from the Ultraviolet to the Mid-Infrared
• The Spectroscopic Data Processing Pipeline for the Dark Energy Spectroscopic Instrument
• Very Strong Emission-Line Galaxies in the WISP Survey and Implications for High-Redshift Galaxies
• Bayesian Neural Networks: An Introduction and Survey
• Spectral Classification of Galaxies: An Orthogonal Approach
• The Robotic Multi-Object Focal Plane System of the Dark Energy Spectroscopic Instrument (DESI)
• AGN Emission Line Diagnostics and the Mass-Metallicity Relation up to Redshift z~2: the Impact of Selection Effects and Evolution
• Photometric Redshifts for Next-Generation Surveys
• Spectroscopic Needs for Imaging Dark Energy Experiments: Photometric Redshift Training and Calibration
• The DESI Survey Validation: Results from Visual Inspection of the Quasar Survey Spectra
• The Importance of Nebular Continuum and Line Emission in Observations of Young Massive Star Clusters
• Dimensionality Reduction of SDSS Spectra with Variational Autoencoders
• SPECULATOR: Emulating stellar population synthesis for fast and accurate galaxy spectra and photometry
• A rise in the ionizing photons in star-forming galaxies over the past 5 billion years
• Self-consistent predictions for LIER-like emission lines from post-AGB stars
• The impact of spectroscopic incompleteness in direct calibration of redshift distributions for weak lensing surveys
• The flux ratio of the [N II]$\lambda \lambda$ 6548, 6583 Å lines in sample of Active Galactic Nuclei Type 2
• Forward modeling of galaxy populations for cosmological redshift distribution inference
• Diffstar: A Fully Parametric Physical Model for Galaxy Assembly History
• Hierarchical Bayesian inference of photometric redshifts with stellar population synthesis models
• The PAU Survey: Measurement of Narrow-band galaxy properties with Approximate Bayesian Computation
• Messenger Monte-Carlo MAPPINGS V (M^3) -- A self-consistent three-dimensional photoionization code
• CLASS Survey Description: Coronal Line Needles in the SDSS Haystack
• Quantifying correlations between galaxy emission lines and stellar continua
• Correlations between Nebular Emission and the Continuum Spectral Shape in SDSS Galaxies

Cited by in corpus (4)

• Impact of stellar population synthesis choices on forward modelling-based redshift distribution estimates
• pop-cosmos: Scaleable inference of galaxy properties and redshifts with a data-driven population model
• pop-cosmos: Insights from generative modeling of a deep, infrared-selected galaxy population
• Modeling spatially-resolved galactic H$\alpha$ emission for galaxy clustering