J/MNRAS/315/839 Compact variable radio sources at 151MHz. I. (Minns+, 2000)
Compact radio sources variable at 151MHz - I. Catalogue of sources.
Minns A.R., Riley J.M.
<Mon. Not. R. Astron. Soc. 315, 839 (2000)>
=2000MNRAS.315..839M 2000MNRAS.315..839M
ADC_Keywords: Galaxy catalogs ; Radio sources
Keywords: catalogues - galaxies: active - quasars: general -
radio continuum: galaxies
Abstract:
The Cambridge Low-Frequency Synthesis Telescope has been used to
produce a representative sample of low-frequency variable sources.
20 fields, each covering an area of approximately
9°x9°cosecDE, have been observed at 151MHz at between 2 and 10
epochs over the period from 1984 to 1996. At each epoch, maps were
made with rms noise levels of typically 10-15mJy/beam. From a total
of ∼6000 sources detected on these maps, 207 are found for which the
flux density variations between at least two epochs appear significant
at greater than the 3σ level. A numerical model is used to
assess the true significance of the variability, given the analysis
method adopted. This shows that for about half of the sources which
appear to vary by >3σ the variability is genuine. For the other
half it is caused by random statistical fluctuations; most of the
spurious variables vary by ≤3.5σ between a single pair of
epochs. A catalogue of the variable sources is presented, which
includes an estimate of the probability that a given source is a
genuine variable. Fractional flux density variations of between 5 and
100% (typically 15-25%) have been detected on a range of time-scales
from 1 to 12 years.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 31 21 List of variability fields
table7.dat 112 207 Catalogue of potential low-frequency variability
(PLFV) sources
table9.dat 102 28 LFV optical identification references
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See also:
VIII/18 : 6C Survey of radio sources I. (Baldwin+ 1985)
VIII/21 : 6C Survey of radio sources II. (Hales+ 1988)
VIII/22 : 6C Survey of Radio Sources III. (Hales+ 1990)
VIII/23 : 6C Survey of radio sources IV. (Hales+ 1991)
VIII/24 : 6C Survey of Radio Sources V. (Hales+ 1993)
VIII/25 : 6C Survey of radio sources VI. (Hales+ 1993)
J/MNRAS/276/614 : Radio-optical 151MHz survey of the N. Ecl. Cap (Lacy+ 1995)
J/MNRAS/298/637 : 7C: 151MHz survey of 3 regions (Pooley+, 1998)
J/MNRAS/294/607 : 7C(G) 151MHz survey of the Galactic plane (Vessey+ 1998)
Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
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1- 8 A8 --- Field Field
10- 11 I2 h RAh Right ascension (B1950)
13- 14 I2 min RAm Right ascension (B1950)
16- 19 F4.1 s RAs Right ascension (B1950)
21 A1 --- DE- Declination sign (B1950)
22- 23 I2 deg DEd Declination (B1950)
25- 26 I2 arcmin DEm Declination (B1950)
28- 31 F4.1 arcsec DEs Declination (B1950)
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Byte-by-byte Description of file: table7.dat
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Bytes Format Units Label Explanations
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1- 9 A9 --- IAU IAU name (based on B1950 position)
11- 16 A6 --- Field CLFST field (see table 1),
17 A1 ---- n_Field [*] * indicates multiple fields (see Sect. 4)
19- 20 I2 h RAh Best available radio right ascension (B1950)
22- 23 I2 min RAm Best available radio right ascension (B1950)
25- 29 F5.2 s RAs Best available radio right ascension (B1950)
31 A1 --- DE- Best available radio declination sign (B1950)
32- 33 I2 deg DEd Best available radio declination (B1950)
35- 36 I2 arcmin DEm Best available radio declination (B1950)
38- 41 F4.1 arcsec DEs Best available radio declination (B1950)
43 A1 --- rp LFV position references (1)
44- 45 I2 --- r_ID ? LFV optical ID references in table9.dat
46 A1 --- u_rp [?] Uncertainty flag on rp
47- 48 A2 --- ID Optical identification code (2)
50- 54 F5.3 --- z ? Redshift (if available)
56- 61 F6.1 % DS/S ? Maximum observed percentage variability of
151MHz beam-fitted flux density between
two epochs
63- 66 F4.1 --- sigmaf Significance of variability
68- 69 I2 --- Npair Number of pairs of epochs between which
3.sigmaf variability has been detected;
70 A1 --- u_Npair [?*] ?: all cases of 3sigmaf variability have
common epoch
*: 3.sigmaf variability for at least two
independent pairs of epochs
72 A1 --- l_Pgen Limit flag on Pgen
73- 76 F4.2 --- Pgen Probability that variability is genuine
(see Section 3)
78- 83 F6.3 Jy S151m Minimum value of observed range of 151MHz
beam-fitted flux density (Jy/beam)
85- 90 F6.3 Jy S151M Maximum value of observed range of 151MHz
beam-fitted flux density (Jy/beam)
92- 96 F5.2 --- SILF ? Low-frequency spectral index (4)
97 A1 --- n_SILF [* ] *: between 151 and 365MHz
unmarked: between 151 and 408MHz
99-103 F5.2 --- SIHF ? High-frequency spectral index (4)
104 A1 --- n_SIHF [?* ] ?: between 1.4GHz and 15GHz
*: between 1.4GHz and 4.85GHz
unmarked: between 4.85GHz and 15GHz
106-112 A7 --- SClass Spectral class (4) (3)
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Note (1): LFV position references as follows:
C = CLFST (this paper)
F = FIRST (White et al., 1997ApJ...475..479W 1997ApJ...475..479W, Cat. VIII/59)
J = MERLIN Calibrator (Patnaik et al., 1992MNRAS.254..655P 1992MNRAS.254..655P,
Cat. VIII/60)
L = VLA: LFV1 Sample (Riley & Warner, 1994MNRAS.269..166R 1994MNRAS.269..166R)
M = VLA: LFV2 Sample (Minns; Paper II, in prep.)
N = NVSS (Condon et al., 1996, See Cat. VIII/65)
Q = New Optical Catalog of QSOs (Hewitt & Burbidge, 1989, A New
Optical Catalog of Quasi-Stellar Objects., via NED)
R = Ryle Telescope (Minns; Paper IV, in prep.)
T = Texas Survey (Douglas et al. 1996AJ....111.1945D 1996AJ....111.1945D)
a = Argue et al., 1984A&A...130..191A 1984A&A...130..191A
b = Benn et al., 1988MNRAS.230....1B 1988MNRAS.230....1B
c = Fey et al., 1994AJ....107..385F 1994AJ....107..385F
d = Johnston et al., 1995, Cat. J/AJ/110/880
e = Lacy, Rawlings & Warner, 1992MNRAS.256..404L 1992MNRAS.256..404L
f = Laing, 1981MNRAS.194..301L 1981MNRAS.194..301L
g = Morabito et al., 1983AJ.....88.1138M 1983AJ.....88.1138M
h = Owen & Keel, 1995AJ....109..486O 1995AJ....109..486O
i = Pearson, Readhead & Perley, 1985AJ.....90..738P 1985AJ.....90..738P
j = Vigotti et al., 1989, Cat. J/AJ/98/419
Note (2): Optical identification as follows:
U = No identification
Q = QSO
G = Galaxy
Q? = Star-like object
G? = Possibly extended object
? = Very faint detection
Note (3): Spectral class as follows:
F = SILF<0.5
S = SILF>0.5
C+ = SIHF-SILF←0.5
C- = SIHF-SILF>0.5
(U) = SIHF>1.0
(I) = SIHF<0.5 (for FC- spectra only)
* = SIHF and/or SILF could not be determined - spectral class
estimated using flux densities from frequencies other than
those listed for SILF and SIHL
x = only two flux densities available which are well separated in
frequency - in this case, F or S is assigned using the one
available spectral index.
Note (4): The flux densities used to produce the spectral indices and
spectral classifications are from the following sources:
152 MHz = from 3-year 7C data where possible
(Minns 1998, PhD thesis, MRAO, Cambridge;
Pooley et al., 1998, Cat. J/MNRAS/298/637),
otherwise from best available CLFST data
(Minns 1998, PhD thesis, MRAO, Cambridge) (Epoch 1994-5).
NOTE: More recent 7C data were used than those published by
McGilchrist et al. (1990MNRAS.246..123M 1990MNRAS.246..123M) and
Lacy et al. (1995, Cat. J/MNRAS/276/614);
details will be given in a forthcoming paper.
366 MHz = from Texas Survey (Douglas et al., 1996AJ....111.1945D 1996AJ....111.1945D,
Cat. VIII/42, Epoch 1974-83).
409 MHz = from B3 (Epoch 1977) where possible (Ficarra, Grueff &
Tomassetti, 1985A&AS...59..255F 1985A&AS...59..255F, Cat. VIII/37), otherwise
from B2 (Colla et al., 1970A&AS....1..281C 1970A&AS....1..281C, 1972A&AS....7....1C 1972A&AS....7....1C,
1973A&AS...11..291C 1973A&AS...11..291C, Cat. VIII/36, Epoch ∼1968).
1.4 GHz = from NVSS where possible (Condon et al., 1996, in The NRAO
VLA sky survey, in NCSA Astrono my Digital Image Library,
p. 1, See Cat. VIII/65, (Epoch 1993-6),
otherwise from the Green Bank 1.4-GHz Survey
(White & Becker, 1992ApJS...79..331W 1992ApJS...79..331W) (Epoch 1983).
4.85 GHz = from GB6 (Gregory et al., 1996ApJS..103..427G 1996ApJS..103..427G, Epoch 1986-7)
16 GHz = from Ryle Telescope observations
(Paper IV; Minns, in prep., Epoch 1992-7).
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Byte-by-byte Description of file: table9.dat
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Bytes Format Units Label Explanations
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1- 2 I2 --- Ref Reference number
4- 22 A19 --- Bibcode Bibcode
24- 48 A25 --- Aut Author's name
50-102 A53 --- Com Comments
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History:
From MNRAS electronic version
(End) James Marcout, Patricia Bauer [CDS] 03-Oct-2000