Correcting correlation functions for redshift-dependent interloper contamination

Abstract

The construction of catalogues of a particular type of galaxy can be complicated by interlopers contaminating the sample. In spectroscopic galaxy surveys this can be due to the misclassification of an emission line; for example in the Hobby-Eberly Telescope Dark Energy Experiment (HETDEX) low redshift [OII] emitters may make up a few percent of the observed Ly$\alpha$ emitter (LAE) sample. The presence of contaminants affects the measured correlation functions and power spectra. Previous attempts to deal with this using the cross-correlation function have assumed sources at a fixed redshift, or not modelled evolution within the adopted redshift bins. However, in spectroscopic surveys like HETDEX, where the contamination fraction is likely to be redshift dependent, the observed clustering of misclassified sources will appear to evolve strongly due to projection effects, even if their true clustering does not. We present a practical method for accounting for the presence of contaminants with redshift-dependent contamination fractions and projected clustering. We show using mock catalogues that our method, unlike existing approaches, yields unbiased clustering measurements from the upcoming HETDEX survey in scenarios with redshift-dependent contamination fractions within the redshift bins used. We show our method returns auto-correlation functions with systematic biases much smaller than the statistical noise for samples with at least as high as 7 per cent contamination. We also present and test a method for fitting for the redshift-dependent interloper fraction using the LAE-[OII] galaxy cross-correlation function, which gives less biased results than assuming a single interloper fraction for the whole sample.

arXiv commentThis is a pre-copy edited, author-produced PDF of an article accepted for publication in Monthly Notices of the Royal Astronomical Society following peer review. The version of record Farrow et al, MNRAS, 2021 is available online at: https://academic.oup.com/mnras/advance-article-abstract/doi/10.1093/mnras/stab1986/6322852

References in corpus (60)

• SciPy 1.0--Fundamental Algorithms for Scientific Computing in Python
• Array Programming with NumPy
• Maps of Dust IR Emission for Use in Estimation of Reddening and CMBR Foregrounds
• Astropy: A Community Python Package for Astronomy
• The Astropy Project: Building an inclusive, open-science project and status of the v2.0 core package
• Measuring Reddening with SDSS Stellar Spectra and Recalibrating SFD
• Efficient Computation of CMB anisotropies in closed FRW models
• Cosmological parameters from CMB and other data: a Monte-Carlo approach
• Correcting for the Effects of Interstellar Extinction
• The Baryon Oscillation Spectroscopic Survey of SDSS-III
• The Dark Energy Camera
• Large-Scale Galaxy Bias
• Cobaya: Code for Bayesian Analysis of hierarchical physical models
• Efficient sampling of fast and slow cosmological parameters
• Renormalized Cosmological Perturbation Theory
• The Dark Energy Survey Data Release 1
• Measuring the cosmological constant with redshift surveys
• Spectral and Photometric Evolution of Young Stellar Populations: the Impact of Gaseous Emission at Various Metallicities
• Photometric Response Functions of the SDSS Imager
• An extensive library of 2500-10500 Ang synthetic spectra
• Gravity and Large-Scale Non-local Bias
• The clustering of massive galaxies at z~0.5 from the first semester of BOSS data
• The clustering of galaxies in the completed SDSS-III Baryon Oscillation Spectroscopic Survey: cosmological implications of the configuration-space clustering wedges
• Methods for Rapidly Processing Angular Masks of Next-Generation Galaxy Surveys
• The bias field of dark matter haloes
• Precision measurement of the local bias of dark matter halos
• The Blue Tip of the Stellar Locus: Measuring Reddening with the SDSS
• Measuring the 3D Clustering of Undetected Galaxies Through Cross Correlation of their Cumulative Flux Fluctuations from Multiple Spectral Lines
• Separate Universe Simulations
• A scheme to deal accurately and efficiently with complex angular masks in galaxy surveys
• Clustering of K-selected Galaxies at 2<z<3.5: Evidence for a Color-Density Relation
• SED fitting with Markov Chain Monte Carlo: Methodology and Application to z=3.1 Lyman Alpha Emitting Galaxies
• The Spitzer-HETDEX Exploratory Large-Area Survey
• On Removing Interloper Contamination from Intensity Mapping Power Spectrum Measurements
• Arguments against using $h^{-1}\mathrm{Mpc}$ units in observational cosmology
• Spectral Line De-confusion in an Intensity Mapping Survey
• The physical origins and dominant emission mechanisms of Lyman-alpha halos: results from the TNG50 simulation in comparison to MUSE observations
• Foreground contamination in Ly-alpha intensity mapping during the epoch of reionization
• Generating Log-normal Mock Catalog of Galaxies in Redshift Space
• Two Ways of Biasing Galaxy Formation
• The HETDEX Pilot Survey. IV. The Evolution of [O II] Emitting Galaxies from z ~ 0.5 to z ~ 0
• Testing one-loop galaxy bias: Power spectrum
• Two-point correlation function of high-redshift objects: an explicit formulation on a light-cone hypersurface
• On the cross-correlation of sub-mm sources and optically-selected galaxies
• Phase-Space Spectral Line De-confusion in Intensity Mapping
• The clustering of typical Ly$\alpha$ emitters from $z\sim 2.5-6$: host halo masses depend on Ly$\alpha$ and UV luminosities
• Interloper bias in future large-scale structure surveys
• Bayesian Redshift Classification of Emission-line Galaxies with Photometric Equivalent Widths
• Cosmological constraints from line intensity mapping with interlopers
• The impact of Lyman-$\alpha$ radiative transfer on large-scale clustering in the Illustris simulation
• Galaxy redshift surveys with sparse sampling
• The Spitzer-HETDEX Exploratory Large Area Survey II: Dark Energy Camera and Spitzer/IRAC Multiwavelength Catalog
• Lyα emitters in a cosmological volume I: the impact of radiative transfer
• The Impact of Line Misidentification on Cosmological Constraints from Euclid and other Spectroscopic Galaxy Surveys
• Unbiased Cosmological Parameter Estimation from Emission Line Surveys with Interlopers
• Lyman-alpha emitters in a cosmological volume II: the impact of the intergalactic medium
• Radiative Transfer Distortions of Lyman-$\alpha$ Emitters: a New Fingers-of-God Damping in the Clustering in Redshift Space
• The Light-cone Effect on the Clustering Statistics in the Cosmological Redshift Space
• Line confusion in spectroscopic surveys and its possible effects: Shifts in Baryon Acoustic Oscillations position
• Angular Correlation Function Estimators Accounting for Contamination from Probabilistic Distance Measurements

Cited by in corpus (19)

• The HETDEX Instrumentation: Hobby-Eberly Telescope Wide Field Upgrade and VIRUS
• HETDEX Public Source Catalog 1: 220K Sources Including Over 50K Lyman Alpha Emitters from an Untargeted Wide-area Spectroscopic Survey
• Surface Brightness Profile of Lyman-$\alpha$ Halos out to 320 kpc in HETDEX
• First HETDEX Spectroscopic Determinations of Ly$\alpha$ and UV Luminosity Functions at $z=2-3$: Bridging a Gap Between Faint AGN and Bright Galaxies
• The HETDEX Survey: Emission Line Exploration and Source Classification
• ZELDA: fitting Lyman-alpha line profiles using deep learning
• Introducing the Texas Euclid Survey for Lyman Alpha (TESLA) Survey: Initial Study Correlating Galaxy Properties to Lyman-Alpha Emission
• Stellar Populations of Lyman-alpha Emitting Galaxies in the HETDEX Survey I: An Analysis of LAEs in the GOODS-N Field
• Using Dark Energy Explorers and Machine Learning to Enhance the Hobby-Eberly Telescope Dark Energy Experiment
• An unbiased method of measuring the ratio of two data sets
• Precise self-calibration of interloper bias in spectroscopic surveys
• Photometric IGM tomography with Subaru/HSC: the large-scale structure of Ly$\alpha$ emitters and IGM transmission in the COSMOS field at $z\sim 5$
• Participatory Science and Machine Learning Applied to Millions of Sources in the Hobby-Eberly Telescope Dark Energy Experiment
• zELDA II: reconstruction of galactic Lyman-alpha spectra attenuated by the intergalactic medium using neural networks
• Removal of interloper contamination to line-intensity maps using correlations with ancillary tracers of the large-scale structure
• A Search for Lensed Lyman-Alpha Emitters within the Early HETDEX Data Set
• Detection of Lyman Continuum from 3.0 < z < 3.5 Galaxies in the HETDEX Survey
• Toward accurate measurement of property-dependent galaxy clustering: II. Tests of the smoothed density-corrected $V_{\max }$ method
• A novel analysis of contamination in Lyman-break galaxy samples at $\mathbf{z}\sim 6-8$: spatial correlation with intermediate-redshift galaxies at $\mathbf{z}\sim 1.3-2$