The Galaxy Power Spectrum from TGSS ADR1 and the Effect of Flux Calibration Systematics

Prabhakar Tiwari; Shamik Ghosh; Pankaj Jain

doi:10.3847/1538-4357/ab54c8

The Galaxy Power Spectrum from TGSS ADR1 and the Effect of Flux Calibration Systematics

Prabhakar Tiwari, Shamik Ghosh, Pankaj Jain

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Abstract

We explore the large to moderate scale anisotropy in distant radio sources using the TIFR GMRT Sky Survey (TGSS) ADR1 catalog. We use different measures, i.e., number counts, sky brightness, and flux per source, for this study. In agreement with earlier results, we report a significant excess of clustering signal above the angular scale of roughly 10° (i.e., l 20-30). We find that some survey areas have a systematically low/high flux and argue this may be the cause of the observed signal of excess power at low multipoles. With mocks we demonstrate the effect of such large-scale flux systematics and recover a TGSS-like excess clustering signal by assuming 20% flux uncertainties over ∼10° × 10° sized patches. We argue that that TGSS at this stage, i.e., TGSS ADR1, is not suitable for large-scale clustering measurements. We find that the measure, flux per source, shows evidence of isotropy for all multipoles l > 2 despite the presence of systematics in the data.

Original language	English
Article number	175
Journal	Astrophysical Journal
Volume	887
Issue number	2
DOIs	https://doi.org/10.3847/1538-4357/ab54c8
State	Published - 20 Dec 2019
Externally published	Yes

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title = "The Galaxy Power Spectrum from TGSS ADR1 and the Effect of Flux Calibration Systematics",

abstract = "We explore the large to moderate scale anisotropy in distant radio sources using the TIFR GMRT Sky Survey (TGSS) ADR1 catalog. We use different measures, i.e., number counts, sky brightness, and flux per source, for this study. In agreement with earlier results, we report a significant excess of clustering signal above the angular scale of roughly 10° (i.e., l 20-30). We find that some survey areas have a systematically low/high flux and argue this may be the cause of the observed signal of excess power at low multipoles. With mocks we demonstrate the effect of such large-scale flux systematics and recover a TGSS-like excess clustering signal by assuming 20% flux uncertainties over ∼10° × 10° sized patches. We argue that that TGSS at this stage, i.e., TGSS ADR1, is not suitable for large-scale clustering measurements. We find that the measure, flux per source, shows evidence of isotropy for all multipoles l > 2 despite the presence of systematics in the data.",

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T1 - The Galaxy Power Spectrum from TGSS ADR1 and the Effect of Flux Calibration Systematics

AU - Tiwari, Prabhakar

AU - Ghosh, Shamik

AU - Jain, Pankaj

PY - 2019/12/20

Y1 - 2019/12/20

N2 - We explore the large to moderate scale anisotropy in distant radio sources using the TIFR GMRT Sky Survey (TGSS) ADR1 catalog. We use different measures, i.e., number counts, sky brightness, and flux per source, for this study. In agreement with earlier results, we report a significant excess of clustering signal above the angular scale of roughly 10° (i.e., l 20-30). We find that some survey areas have a systematically low/high flux and argue this may be the cause of the observed signal of excess power at low multipoles. With mocks we demonstrate the effect of such large-scale flux systematics and recover a TGSS-like excess clustering signal by assuming 20% flux uncertainties over ∼10° × 10° sized patches. We argue that that TGSS at this stage, i.e., TGSS ADR1, is not suitable for large-scale clustering measurements. We find that the measure, flux per source, shows evidence of isotropy for all multipoles l > 2 despite the presence of systematics in the data.

AB - We explore the large to moderate scale anisotropy in distant radio sources using the TIFR GMRT Sky Survey (TGSS) ADR1 catalog. We use different measures, i.e., number counts, sky brightness, and flux per source, for this study. In agreement with earlier results, we report a significant excess of clustering signal above the angular scale of roughly 10° (i.e., l 20-30). We find that some survey areas have a systematically low/high flux and argue this may be the cause of the observed signal of excess power at low multipoles. With mocks we demonstrate the effect of such large-scale flux systematics and recover a TGSS-like excess clustering signal by assuming 20% flux uncertainties over ∼10° × 10° sized patches. We argue that that TGSS at this stage, i.e., TGSS ADR1, is not suitable for large-scale clustering measurements. We find that the measure, flux per source, shows evidence of isotropy for all multipoles l > 2 despite the presence of systematics in the data.

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VL - 887

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The Galaxy Power Spectrum from TGSS ADR1 and the Effect of Flux Calibration Systematics

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