Radio spectral index from NVSS and TGSS

Prabhakar Tiwari

doi:10.1088/1674-4527/19/7/96

Radio spectral index from NVSS and TGSS

Prabhakar Tiwari^*

^*Corresponding author for this work

Research output: Contribution to journal › Article › peer-review

17 Scopus citations

Abstract

I extract the radio spectral index, α, from 541 195 common sources observed in the 150MHz TIFR GMRT Sky Survey (TGSS) and the 1.4GHz NRAO VLA Sky Survey (NVSS). This large common source catalog covers about 80% of the sky. The flux density limits in these surveys are such that the observed galaxies are presumably hosts of active galactic nuclei (AGNs). I confirm the steepening of α with increasing flux density for this large sample and provide a parametric fit between α and flux density. Next, I divide the data into low flux (LF) and high flux (HF) density samples with roughly equal numbers of galaxies. The LF sample contains all galaxies below 100mJy TGSS and 20mJy NVSS flux density and the HF sample is all galaxies above 100mJy TGSS and 20mJy NVSS. I observe an increase in α with source size (TGSS measured), saturating for large sizes to 0.89 + 0.22 and 0.76 + 0.21 for the LF and HF sources, respectively. I discuss the observed results and possible physical mechanisms to explain observed α dependence with source size for LF and HF samples.

Original language	English
Article number	096
Journal	Research in Astronomy and Astrophysics
Volume	19
Issue number	7
DOIs	https://doi.org/10.1088/1674-4527/19/7/96
State	Published - 2019
Externally published	Yes

Keywords

galaxies: Active galactic nuclei
galaxies: high-redshift

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10.1088/1674-4527/19/7/96

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title = "Radio spectral index from NVSS and TGSS",

abstract = "I extract the radio spectral index, α, from 541 195 common sources observed in the 150MHz TIFR GMRT Sky Survey (TGSS) and the 1.4GHz NRAO VLA Sky Survey (NVSS). This large common source catalog covers about 80% of the sky. The flux density limits in these surveys are such that the observed galaxies are presumably hosts of active galactic nuclei (AGNs). I confirm the steepening of α with increasing flux density for this large sample and provide a parametric fit between α and flux density. Next, I divide the data into low flux (LF) and high flux (HF) density samples with roughly equal numbers of galaxies. The LF sample contains all galaxies below 100mJy TGSS and 20mJy NVSS flux density and the HF sample is all galaxies above 100mJy TGSS and 20mJy NVSS. I observe an increase in α with source size (TGSS measured), saturating for large sizes to 0.89 + 0.22 and 0.76 + 0.21 for the LF and HF sources, respectively. I discuss the observed results and possible physical mechanisms to explain observed α dependence with source size for LF and HF samples.",

keywords = "galaxies: Active galactic nuclei, galaxies: high-redshift",

author = "Prabhakar Tiwari",

note = "Publisher Copyright: {\textcopyright} 2019 National Astronomical Observatories, CAS and IOP Publishing Ltd.",

year = "2019",

doi = "10.1088/1674-4527/19/7/96",

language = "英语",

volume = "19",

journal = "Research in Astronomy and Astrophysics",

issn = "1674-4527",

publisher = "IOP Publishing Ltd.",

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AU - Tiwari, Prabhakar

PY - 2019

Y1 - 2019

N2 - I extract the radio spectral index, α, from 541 195 common sources observed in the 150MHz TIFR GMRT Sky Survey (TGSS) and the 1.4GHz NRAO VLA Sky Survey (NVSS). This large common source catalog covers about 80% of the sky. The flux density limits in these surveys are such that the observed galaxies are presumably hosts of active galactic nuclei (AGNs). I confirm the steepening of α with increasing flux density for this large sample and provide a parametric fit between α and flux density. Next, I divide the data into low flux (LF) and high flux (HF) density samples with roughly equal numbers of galaxies. The LF sample contains all galaxies below 100mJy TGSS and 20mJy NVSS flux density and the HF sample is all galaxies above 100mJy TGSS and 20mJy NVSS. I observe an increase in α with source size (TGSS measured), saturating for large sizes to 0.89 + 0.22 and 0.76 + 0.21 for the LF and HF sources, respectively. I discuss the observed results and possible physical mechanisms to explain observed α dependence with source size for LF and HF samples.

AB - I extract the radio spectral index, α, from 541 195 common sources observed in the 150MHz TIFR GMRT Sky Survey (TGSS) and the 1.4GHz NRAO VLA Sky Survey (NVSS). This large common source catalog covers about 80% of the sky. The flux density limits in these surveys are such that the observed galaxies are presumably hosts of active galactic nuclei (AGNs). I confirm the steepening of α with increasing flux density for this large sample and provide a parametric fit between α and flux density. Next, I divide the data into low flux (LF) and high flux (HF) density samples with roughly equal numbers of galaxies. The LF sample contains all galaxies below 100mJy TGSS and 20mJy NVSS flux density and the HF sample is all galaxies above 100mJy TGSS and 20mJy NVSS. I observe an increase in α with source size (TGSS measured), saturating for large sizes to 0.89 + 0.22 and 0.76 + 0.21 for the LF and HF sources, respectively. I discuss the observed results and possible physical mechanisms to explain observed α dependence with source size for LF and HF samples.

KW - galaxies: Active galactic nuclei

KW - galaxies: high-redshift

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U2 - 10.1088/1674-4527/19/7/96

DO - 10.1088/1674-4527/19/7/96

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SN - 1674-4527

VL - 19

JO - Research in Astronomy and Astrophysics

JF - Research in Astronomy and Astrophysics

IS - 7

M1 - 096

ER -

Radio spectral index from NVSS and TGSS

Abstract

Keywords

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