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J/ApJS/103/331 mJy radio sources at 1.4 GHz (Lu+ 1996)
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Radio properties and optical identification of two samples of
milliJansky radio sources at 1.4 GHz
Lu N.Y., Hoffman G.L., Salpeter E.E., Houck J.R.
<Astrophys. J. Suppl. Ser. 103, 331 (1996)>
=1996ApJS..103..331L (SIMBAD/NED BibCode)
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ADC_Keywords: Radio lines ; Galaxies, radio ; Morphology ; Photometry
Keywords: galaxies: distances and redshifts - galaxies: photometry -
galaxies: structure - radio continuum: galaxies - surveys
Abstract:
From the 1.4GHz radio survey of Condon, Dickey, & Salpeter
(Cat. <J/AJ/99/1071>) in a region much devoid of rich galaxy clusters
at redshifts z<0.43 we selected a "distant" sample of 57 radio sources
complete to a 1.4GHz flux density of 35mJy and a "nearby" sample of
36 mostly weaker radio sources which are optically brighter than
B~19mag. Our ultimate goals are (1) to study the radio, optical, and
near-IR properties of those high-redshift (z~1), moderate-power radio
sources in the distant sample and to compare them with that of more
powerful radio sources, and (2) to make a comparison of primarily
noncluster radio sources in the nearby sample with a companion survey
of radio sources in a pair of rich superclusters at z~0.1. In this
first paper of a series, we report our new C-array VLA continuum
snapshots at 4.86GHz and optical R-band CCD imaging photometry for
these two samples and tabulate the observational results on individual
sources. Some direct sample statistical properties are also discussed
in the paper and summarized as follows:
(1) The distant sample:
(a) The sample median flux density at 1.4GHz is about 65mJy.
(b) The majority (80%) of the sample sources have a steep spectrum
between 1.4 and 4.86GHz with a spectral index around 0.9.
Nineteen (90%) of the 21 sources that are fully resolved at
4.86 GHz (i.e., angular sizes {theta}>11") have a radio
morphology of Fanaroff-Riley (FR) II type.
(c) Thirty-seven (88%) of the 42 optically imaged sample sources were
optically identified to a limiting R-band magnitude of R~23.5mag.
About 15% of the identified radio sources appear to be point
sources, and the others are extended galaxies with an appearance
similar to nearby elliptical galaxies.
(d) Twenty-eight (76%) of the optically identified sources have
R>20mag, suggesting that these are probably distant (z>0.8),
with a redshift distribution peaking at z~1, where their radio
luminosities are about 10 times the break power between the
FR I and II classes.
(e) We found no strong evidence for the radio and optical axes of the
resolved radio sources (i.e., {theta}>5") to be correlated or
anticorrelated, nor any evidence for strong clustering around
sample radio sources on average.
(2) The nearby sample: except for R<15, the sample is dominated by
elliptical galaxies with 16<R<18.5mag and a spectral index
distribution similar to that of the distant sample. Based on the
radial distribution of optical objects around each radio source, we
found that the average radio source environment becomes richer from
that characteristic of galaxy groups for R<17mag (z<0.2) to that of
galaxy groups to clusters at R>18mag (z>0.3) .
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 83 110 Results from the radio-continuum snapshot
observations at 4.86GHz.
table2.dat 75 102 Radio properties of sample sources at 1.4
and 4.86GHz
table3.dat 100 66 Results from the R-Band CCD imaging photometry
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See also:
J/AJ/99/1071 : 1.4 GHz source survey (Condon+ 1990)
Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
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1- 4 A4 --- Name Source name
5 A1 --- n_Name [n] n for near
6 A1 --- Note [abcd] Note on radio signal (1)
8 I1 h RAh ? Right ascension (1950) (2)
10- 11 I2 min RAm ? Right ascension (1950)
13- 17 F5.2 s RAs ? Right ascension (1950)
18 A1 --- DE- Declination sign
19- 20 I2 deg DEd ? Declination (1950)
22- 23 I2 arcmin DEm ? Declination (1950)
25- 28 F4.1 arcsec DEs ? Declination (1950)
30 A1 --- l_Smax Limit flag on Smax
31- 36 F6.2 mJy Smax Peak flux density
38- 41 F4.2 mJy e_Smax ? rms uncertainty on Smax
43 A1 --- l_S4.86GHz Limit flag on S4.86GHz
44- 49 F6.2 mJy S4.86GHz Integrated flux density at 4.86GHz
51- 54 F4.2 mJy e_S4.86GHz ? rms uncertainty on S4.86GHz
56 A1 --- l_2a Limit flag on 2a
57- 60 F4.1 arcsec 2a ? Estimated major axis
62- 64 F3.1 arcsec e_2a ? rms uncertainty on 2a
66 A1 --- l_2b Limit flag on 2b
67- 70 F4.1 arcsec 2b ? Estimated minor axis
72- 74 F3.1 arcsec e_2b ? rms uncertainty on 2b
76- 78 I3 deg PA ? Position angle (north to east of major axis)
80- 81 I2 deg e_PA ? rms uncertainty on PA
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Note (1): a: Radio signals are weak
b: Radio signals are weak. Only the two largest components are listed,
i.e. the one on the most left and the one in the middle of the
radio contour plot in Fig. 2
c: Radio signals are weak. Two components of R203 are shown
separatedly in Fig. 2 as R203A and R203B. The objects are at the
center of each plot
d: Not detected. Upper limits are 3{sigma}
Note (2): Peak position of the best-fit Gaussian profile to each signal
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Byte-by-byte Description of file: table2.dat
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Bytes Format Units Label Explanations
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1- 4 A4 --- Name Source name
5 A1 --- m_Name [AB] Multiplicity index on Name
6 A1 --- n_Name [a] Note on Name (1)
8- 12 A5 --- Sample Sample (2)
14 I1 h RAh Right ascension (1950) (3)
16- 17 I2 min RAm Right ascension (1950)
19- 23 F5.2 s RAs Right ascension (1950)
24 A1 --- DE- Declination sign
25- 26 I2 deg DEd Declination (1950)
28- 29 I2 arcmin DEm Declination (1950)
31- 34 F4.1 arcsec DEs Declination (1950)
36- 41 F6.2 mJy S1.4GHz Integreted flux density at 1.4GHz
42 A1 --- l_S4.86GHz Limit flag on S4.86GHz
43- 48 F6.2 mJy S4.86GHz ? Integreted flux density at 4.86GHz
50- 54 F5.2 --- SI ? Spectral index between 1.4 and 4.86GHz
56 A1 --- l_theta Limit flag on theta
57- 60 F4.1 arcsec theta ? (maximum) angular size from 4.86GHz
radio map
62- 64 I3 deg PA ? Position angle (north to east) (4)
66- 75 A10 --- Morph Morphology
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Note (1): a: Not observed at 4.86 GHz
Note (2): DS: Distant sample
NS: Nearby sample
a: additional source
Note (3): Position of the adopted center of the source
Note (4): Positon angle of the major axis fro single component sources or of
the axis connecting the two radio lobes for double-lobed sources
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Byte-by-byte Description of file: table3.dat
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Bytes Format Units Label Explanations
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1- 4 A4 --- Name Source name
5 A1 --- m_Name [AB] Multiplicity index on Name
6 A1 --- n_Name [abcdef] Note on Name (1)
8- 15 A8 "DD/MM/YY" Date Observation date
17- 19 F3.1 arcsec FWHM FWHM of the optical seeing
21- 23 I3 --- Nopt ? Number of the detected optical object
with R<23.5mag
25- 28 F4.1 arcsec a Semi-major axis
29 A1 --- --- [x]
30- 33 F4.1 arcsec b Semi-minor axis
36- 38 I3 deg PA ? Position angle (North to East)
40- 44 F5.2 arcsec oRAr ? Positional offset in RA direction, from the
radio position to the position of an
optical identification
46- 50 F5.2 arcsec oDEr ? Positional offset in DE direction, from the
radio position to the position of an
optical identification
52- 57 F6.1 arcsec oRAs ? Offset in RA direction, from a nearby bright
star to the optical identification
59- 63 F5.1 arcsec oDEs ? Offset in DE direction, from a nearby bright
star to the optical identification
65 A1 --- l_Rmags Limit flag on Rmas
66- 69 F4.1 mag Rmags ? R magnitude of the offsetting star
70 A1 --- n_Rmag [B] B: bright
72- 75 A4 --- Type Type (Gal or QSO)
77- 81 F5.2 mag Rmag ? FOCAS-measured isophotal magnitude
83- 86 I4 arcsec+2 Aiso ? Isophotal area
88- 91 F4.1 arcsec 2a ? Major diameter of optical identification
92 A1 --- --- [x]
93- 96 F4.1 arcsec 2b ? Minor diameter of optical identification
98-100 I3 deg PAo ? Position angle of the optical identification
(North to east)
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Note (1): a: The optical counterpart lies slightly outside the error ellipse.
It was accepted, for it is either optically bright with a radius
much larger than its apparent angular distance to the radio source
position or well between the two radio lobes.
b: The integration time for the R-band CCD image is only 300s.
c: R082 is in a very dense galaxy cluster at z=4.407 (Dressler & Gunn
1992, Cat. <J/ApJS/78/1>). The magnitude may be slightly
contaminated.
d: There is an optical object near one of the radio components.
e: This optical identification is slightly outside the error ellipse.
It was accepted because the central position of this weak radio
source is somewhat uncertain.
f: Radio map at 4.86 GHz is not available. The offsets (i.e., cols.
[oRAr] and [oDEr]) for the second probable optical counterpart are
with respect to the optical position of the first one.
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History: Prepared via OCR at CDS.
* 30-Sep-1998: 2 OCR errors detected by H. Andernach and corrected
(heinz@astro.ugto.mx)
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(End) James Marcout, Patricia Bauer [CDS] 30-Apr-1998