J/MNRAS/474/5008 Radio spectral index 147-1400MHz (de Gasperin+, 2018)
A radio spectral index map and catalogue at 147-1400 MHz covering 80 per cent
of the sky.
de Gasperin F., Intema H.T., Frail D.A.
<Mon. Not. R. Astron. Soc., 474, 5008-5022 (2018)>
=2018MNRAS.474.5008D 2018MNRAS.474.5008D (SIMBAD/NED BibCode)
ADC_Keywords: Radio sources ; Radio continuum
Keywords: catalogues - surveys - pulsars: general - galaxies: active -
radio continuum: general
Abstract:
The radio spectral index is a powerful probe for classifying cosmic
radio sources and understanding the origin of the radio emission.
Combining data at 147MHz and 1.4GHz from the TIFR GMRT Sky Survey
(TGSS) and the NRAO VLA Sky Survey (NVSS), we produced a large-area
radio spectral index map of ∼80 per cent of the sky (Dec. >-40deg), as
well as a radio spectral index catalogue containing 1396515 sources,
of which 503647 are not upper or lower limits. Almost every TGSS
source has a detected counterpart, while this is true only for
36 per cent of NVSS sources. We released both the map and the
catalogue to the astronomical community. The catalogue is analysed to
discover systematic behaviours in the cosmic radio population. We find
a differential spectral behaviour between faint and bright sources as
well as between compact and extended sources. These trends are
explained in terms of radio galaxy evolution. We also confirm earlier
reports of an excess of steep-spectrum sources along the galactic
plane. This corresponds to 86 compact and steep-spectrum source in
excess compared to expectations. The properties of this excess are
consistent with normal non-recycled pulsars, which may have been
missed by pulsation searches due to larger than average scattering
along the line of sight.
Description:
The catalogue contains the flux densities of 1396515 sources from NVSS
(1400MHz; Condon et al., 1998AJ....115.1693C 1998AJ....115.1693C, Cat. VIII/65) and TGSS
(147MHz; Intema et al., 2017A&A...598A..78I 2017A&A...598A..78I, Cat. J/A+A/598/A78), the
sources are matched between the two surveys and the radio spectral
index is extracted. When no counterpart is found, the catalogue lists
the value for the upper/lower limit on the spectral index. More
information available at
http://tgssadr.strw.leidenuniv.nl/doku.php?id=spidx
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
spidxcat.dat 155 1396515 *Spectral index catalogue
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Note on spidxcat.dat: some explanations are valid only for specific entry types
as saved in the Scode column.
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See also:
VIII/65 : 1.4GHz NRAO VLA Sky Survey (NVSS) (Condon+ 1998)
J/A+A/598/A78 : The GMRT 150MHz all-sky radio survey (Intema+, 2017)
Byte-by-byte Description of file: spidxcat.dat
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Bytes Format Units Label Explanations
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1- 13 F13.9 deg RAdeg Right Ascension (J2000) (weighted average
of NVSS and TGSS detections for Scode=SMCI)
15- 27 F13.9 deg DEdeg Declination (J2000) (weighted average
29- 35 F7.2 Jy FtotNVSS ?=0 NVSS 1.4GHz total flux (sum of
detections fluxes for Scode=I,
set to 0 for Scode=U)
37- 41 F5.3 Jy e_FtotNVSS ?=0 rms uncertainty on FtotNVSS (quadratic
mean of detection errors for Scode=I,
set to 0 for Scode=U)
43- 49 F7.2 Jy/beam FpeakNVSS ?=0 NVSS 1.4GHz peak flux (maximum of
detections peak fluxes for Scode=I,
set to 0 for Scode=U)
51- 55 F5.3 Jy/beam e_FpeakNVSS ?=0 rms uncertainty on FpeakNVSS (error
relative to the maximum of detections peak
fluxes for Scode=I, set to 0 for Scode=U)
57- 64 F8.6 Jy/beam rmsNVSS NVSS local rms noise
66- 72 F7.2 Jy FtotTGSS ?=0 TGSS 147MHz total flux (sum of
detections fluxes for Scode=I,
set to 0 for Scode=L)
74- 79 F6.3 Jy e_FtotTGSS ?=0 rms uncertainty on FtotTGSS (quadratic
mean of detections error for Scode=I,
set to 0 for Scode=L)
81- 87 F7.2 Jy/beam FpeakTGSS ?=0 TGSS 147MHz peak flux (maximum of
detections peak fluxes for Scode=I,
set to 0 for Scode=L)
89- 93 F5.3 Jy/beam e_FpeakTGSS ?=0 rms uncertainty on FpeakTGSS (error
relative to the maximum of detections peak
fluxes for Scode=I, set to 0 for Scode=L)
95-102 F8.6 Jy/beam rmsTGSS Local rms noise
104-112 F9.6 --- SpIndex Spectral index between 147MHz and 1.4GHz
114-121 F8.6 --- e_SpIndex Spectral index error (set to 0 for Scode=LU)
123-130 F8.2 --- s2n Peak flux over Island rms
132 A1 --- Scode [SMCILU] Source code (1)
134 I1 --- Nmatch Number of matched sources in the same island
136-137 I2 --- NunmaNVSS Number of NVSS unmatched sources in the
same island
139 I1 --- NunmaTGSS Number of TGSS unmatched sources in the
same island
141-147 I7 --- IslId [30/1855370] Island identification number
149-155 I7 --- SourceId [0/1396514] Unique source identification
number
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Note (1): Source codes as follows:
S = single: a matched (detection in both NVSS and TGSS) source with no other
detections in the same island = these sources are simple, usually
point-like or slightly extended in both surveys
M = multiple: a matched source with other matched sources (but no unmatched
sources) in the same island = these sources are most of the time
double-lobe radio galaxies or collections of nearby point sources
C = complex: a matched source with unmatched detections in one of the two
surveys in the same island = these sources might be part of a more complex
object, e.g. a lobe of a radio galaxy where the other lobe is too faint
to be detected in one of the surveys
L = upper limit: a detection in NVSS with no TGSS detection in the same
island = multiple NVSS detections in the island create multiple entries
in the catalogue
U = lower limit: a detection in TGSS with no NVSS detection in the same
island = multiple TGSS detections in the island create multiple entries
in the catalogue;
I = island: if an island is not only made by matched sources (S, M) or
unmatched source of the same survey (L, U), the global values of that
island are saved as a separate entry = these sources have naturally a
poor positional constrain, complex sources (C) are always also part of
an island source (I).
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Acknowledgements:
Francesco de Gasperin, fdg(at)hs.uni-hamburg.de
(End) Patricia Vannier [CDS] 15-Feb-2021