Interloper bias in future large-scale structure surveys

Anthony R. Pullen, Christopher M. Hirata, Olivier Doré, Alvise Raccanelli

    Research output: Contribution to journalArticle

    Abstract

    Next-generation spectroscopic surveys will map the large-scale structure of the observable universe, using emission line galaxies as tracers. While each survey will map the sky with a specific emission line, interloping emission lines can masquerade as the survey's intended emission line at different redshifts. Interloping lines from galaxies that are not removed can contaminate the power spectrum measurement, mixing correlations from various redshifts and diluting the true signal. We assess the potential for power spectrum contamination, finding that an interloper fraction worse than 0.2% could bias power spectrum measurements for future surveys by more than 10% of statistical errors, while also biasing power spectrum inferences. We also construct a formalism for predicting cosmological parameter measurement bias, demonstrating that a 0.15%-0.3% interloper fraction could bias the growth rate by more than 10% of the error, which can affect constraints on gravity from upcoming surveys. We use the COSMOS Mock Catalog (CMC), with the emission lines rescaled to better reproduce recent data, to predict potential interloper fractions for the Prime Focus Spectrograph (PFS) and the Wide-Field InfraRed Survey Telescope (WFIRST). We find that secondary line identification, or confirming galaxy redshifts by finding correlated emission lines, can remove interlopers for PFS. For WFIRST, we use the CMC to predict that the 0.2% target can be reached for the WFIRST Hα survey, but sensitive optical and near-infrared photometry will be required. For the WFIRST [O iii] survey, the predicted interloper fractions reach several percent and their effects will have to be estimated and removed statistically (e.g., with deep training samples). These results are optimistic as the CMC does not capture the full set of correlations of galaxy properties in the real Universe, and they do not include blending effects. Mitigating interloper contamination will be crucial to the next generation of emission line surveys.

    Original languageEnglish (US)
    JournalPublication of the Astronomical Society of Japan
    Volume68
    Issue number1
    DOIs
    StatePublished - Oct 27 2014

    Fingerprint

    power spectra
    telescopes
    galaxies
    catalogs
    spectrographs
    contamination
    universe
    infrared photometry
    inference
    tracers
    sky
    near infrared
    education
    tracer
    gravity
    gravitation
    formalism
    COSMOS
    effect

    Keywords

    • galaxies: distances and redshift
    • gravitation
    • large-scale structure of universe
    • line: identification
    • surveys

    ASJC Scopus subject areas

    • Astronomy and Astrophysics
    • Space and Planetary Science

    Cite this

    Interloper bias in future large-scale structure surveys. / Pullen, Anthony R.; Hirata, Christopher M.; Doré, Olivier; Raccanelli, Alvise.

    In: Publication of the Astronomical Society of Japan, Vol. 68, No. 1, 27.10.2014.

    Research output: Contribution to journalArticle

    Pullen, Anthony R. ; Hirata, Christopher M. ; Doré, Olivier ; Raccanelli, Alvise. / Interloper bias in future large-scale structure surveys. In: Publication of the Astronomical Society of Japan. 2014 ; Vol. 68, No. 1.
    @article{503545081d5245268dc26e03733a2371,
    title = "Interloper bias in future large-scale structure surveys",
    abstract = "Next-generation spectroscopic surveys will map the large-scale structure of the observable universe, using emission line galaxies as tracers. While each survey will map the sky with a specific emission line, interloping emission lines can masquerade as the survey's intended emission line at different redshifts. Interloping lines from galaxies that are not removed can contaminate the power spectrum measurement, mixing correlations from various redshifts and diluting the true signal. We assess the potential for power spectrum contamination, finding that an interloper fraction worse than 0.2{\%} could bias power spectrum measurements for future surveys by more than 10{\%} of statistical errors, while also biasing power spectrum inferences. We also construct a formalism for predicting cosmological parameter measurement bias, demonstrating that a 0.15{\%}-0.3{\%} interloper fraction could bias the growth rate by more than 10{\%} of the error, which can affect constraints on gravity from upcoming surveys. We use the COSMOS Mock Catalog (CMC), with the emission lines rescaled to better reproduce recent data, to predict potential interloper fractions for the Prime Focus Spectrograph (PFS) and the Wide-Field InfraRed Survey Telescope (WFIRST). We find that secondary line identification, or confirming galaxy redshifts by finding correlated emission lines, can remove interlopers for PFS. For WFIRST, we use the CMC to predict that the 0.2{\%} target can be reached for the WFIRST Hα survey, but sensitive optical and near-infrared photometry will be required. For the WFIRST [O iii] survey, the predicted interloper fractions reach several percent and their effects will have to be estimated and removed statistically (e.g., with deep training samples). These results are optimistic as the CMC does not capture the full set of correlations of galaxy properties in the real Universe, and they do not include blending effects. Mitigating interloper contamination will be crucial to the next generation of emission line surveys.",
    keywords = "galaxies: distances and redshift, gravitation, large-scale structure of universe, line: identification, surveys",
    author = "Pullen, {Anthony R.} and Hirata, {Christopher M.} and Olivier Dor{\'e} and Alvise Raccanelli",
    year = "2014",
    month = "10",
    day = "27",
    doi = "10.1093/pasj/psv118",
    language = "English (US)",
    volume = "68",
    journal = "Publication of the Astronomical Society of Japan",
    issn = "0004-6264",
    publisher = "Astronomical Society of Japan",
    number = "1",

    }

    TY - JOUR

    T1 - Interloper bias in future large-scale structure surveys

    AU - Pullen, Anthony R.

    AU - Hirata, Christopher M.

    AU - Doré, Olivier

    AU - Raccanelli, Alvise

    PY - 2014/10/27

    Y1 - 2014/10/27

    N2 - Next-generation spectroscopic surveys will map the large-scale structure of the observable universe, using emission line galaxies as tracers. While each survey will map the sky with a specific emission line, interloping emission lines can masquerade as the survey's intended emission line at different redshifts. Interloping lines from galaxies that are not removed can contaminate the power spectrum measurement, mixing correlations from various redshifts and diluting the true signal. We assess the potential for power spectrum contamination, finding that an interloper fraction worse than 0.2% could bias power spectrum measurements for future surveys by more than 10% of statistical errors, while also biasing power spectrum inferences. We also construct a formalism for predicting cosmological parameter measurement bias, demonstrating that a 0.15%-0.3% interloper fraction could bias the growth rate by more than 10% of the error, which can affect constraints on gravity from upcoming surveys. We use the COSMOS Mock Catalog (CMC), with the emission lines rescaled to better reproduce recent data, to predict potential interloper fractions for the Prime Focus Spectrograph (PFS) and the Wide-Field InfraRed Survey Telescope (WFIRST). We find that secondary line identification, or confirming galaxy redshifts by finding correlated emission lines, can remove interlopers for PFS. For WFIRST, we use the CMC to predict that the 0.2% target can be reached for the WFIRST Hα survey, but sensitive optical and near-infrared photometry will be required. For the WFIRST [O iii] survey, the predicted interloper fractions reach several percent and their effects will have to be estimated and removed statistically (e.g., with deep training samples). These results are optimistic as the CMC does not capture the full set of correlations of galaxy properties in the real Universe, and they do not include blending effects. Mitigating interloper contamination will be crucial to the next generation of emission line surveys.

    AB - Next-generation spectroscopic surveys will map the large-scale structure of the observable universe, using emission line galaxies as tracers. While each survey will map the sky with a specific emission line, interloping emission lines can masquerade as the survey's intended emission line at different redshifts. Interloping lines from galaxies that are not removed can contaminate the power spectrum measurement, mixing correlations from various redshifts and diluting the true signal. We assess the potential for power spectrum contamination, finding that an interloper fraction worse than 0.2% could bias power spectrum measurements for future surveys by more than 10% of statistical errors, while also biasing power spectrum inferences. We also construct a formalism for predicting cosmological parameter measurement bias, demonstrating that a 0.15%-0.3% interloper fraction could bias the growth rate by more than 10% of the error, which can affect constraints on gravity from upcoming surveys. We use the COSMOS Mock Catalog (CMC), with the emission lines rescaled to better reproduce recent data, to predict potential interloper fractions for the Prime Focus Spectrograph (PFS) and the Wide-Field InfraRed Survey Telescope (WFIRST). We find that secondary line identification, or confirming galaxy redshifts by finding correlated emission lines, can remove interlopers for PFS. For WFIRST, we use the CMC to predict that the 0.2% target can be reached for the WFIRST Hα survey, but sensitive optical and near-infrared photometry will be required. For the WFIRST [O iii] survey, the predicted interloper fractions reach several percent and their effects will have to be estimated and removed statistically (e.g., with deep training samples). These results are optimistic as the CMC does not capture the full set of correlations of galaxy properties in the real Universe, and they do not include blending effects. Mitigating interloper contamination will be crucial to the next generation of emission line surveys.

    KW - galaxies: distances and redshift

    KW - gravitation

    KW - large-scale structure of universe

    KW - line: identification

    KW - surveys

    UR - http://www.scopus.com/inward/record.url?scp=84962833061&partnerID=8YFLogxK

    UR - http://www.scopus.com/inward/citedby.url?scp=84962833061&partnerID=8YFLogxK

    U2 - 10.1093/pasj/psv118

    DO - 10.1093/pasj/psv118

    M3 - Article

    VL - 68

    JO - Publication of the Astronomical Society of Japan

    JF - Publication of the Astronomical Society of Japan

    SN - 0004-6264

    IS - 1

    ER -