J/MNRAS/307/293 Quasars from 7C survey (Riley+, 1999)
Quasars from the 7C survey. I. Sample selection and radio maps.
Riley J.M., Rawlings S., McMahon R.G., Blundell K.M., Miller P., Lacy M.,
Waldram E.M.
<Mon. Not. R. Astron. Soc. 307, 293 (1999)>
=1999MNRAS.307..293R 1999MNRAS.307..293R
ADC_Keywords: QSOs ; Radio sources ; Surveys
Keywords: galaxies: active - quasars: general - radio continuum: galaxies
Abstract:
We describe the selection of candidate radio-loud quasars obtained by
cross-matching radio source positions from the low-frequency (151-MHz)
7C survey with optical positions from five pairs of EO POSS-1 plates
scanned with the Cambridge Automatic Plate-measuring Machine (APM).
The sky region studied is centred at RA=10h28m, DE=+41° and covers
∼0.057sr. We present VLA observations of the quasar candidates, and
tabulate various properties derived from the radio maps. We discuss
the selection criteria of the resulting '7CQ' sample of radio-loud
quasars. The 70 confirmed quasars, and some fraction of the 36
unconfirmed candidates, constitute a filtered sample with the
following selection criteria: 151-MHz flux density S151>100mJy;
POSS-I E-plate magnitude E∼R<20; POSS-I colour (O-E)<1.8; the
effective area of the survey drops significantly below S151∼200mJy.
We argue that the colour criterion excludes few if any quasars, but
note, on the basis of recent work by Willott et al.
(1998MNRAS.300..625W 1998MNRAS.300..625W), that the E magnitude limit probably excludes
more than 50 per cent of the radio-loud quasars.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 103 209 A summary of the radio and optical properties
of the candidate 7CQ quasars in the main sample
table2.dat 103 28 A summary of the radio and optical properties of
the subsidiary sample of candidate 7CQ quasars.
notes.dat 80 127 Individual notes
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See also:
J/A+AS/110/419 : 7C: survey of radio sources (Visser+, 1995)
J/MNRAS/246/110 : 7C survey of radio sources at 151 MHz (McGilchrist+ 1990)
J/MNRAS/276/614 : Radio-optical 151MHz survey of the N. Ecl. Cap (Lacy+ 1995)
J/MNRAS/282/779 : 7C: 151-MHz survey of region 9-16h 20-35deg (Waldram+ 1996)
J/MNRAS/294/607 : 7C(G) 151MHz survey of the Galactic plane (Vessey+ 1998)
J/MNRAS/298/637 : 7C: 151MHz survey of 3 regions (Pooley+, 1998)
Byte-by-byte Description of file: table1.dat table2.dat
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Bytes Format Units Label Explanations
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1 A1 --- Note [NRST*] Note (1)
3- 4 I2 h RAh Radio source right ascension (B1950) (2)
6- 7 I2 min RAm Radio source right ascension (B1950)
9- 13 F5.2 s RAs Radio source right ascension (B1950)
15 A1 --- DE- Radio source declination sign (B1950)
16- 17 I2 deg DEd Radio source declination (B1950)
19- 20 I2 arcmin DEm Radio source declination (B1950)
22- 25 F4.1 arcsec DEs Radio source declination (B1950)
27- 30 F4.1 arcsec Sep Separation of the 7C radio source position and
the APM optical position
32- 36 F5.2 mag Omag ? POSS-1 O magnitude of the quasar candidate
38- 41 F4.2 mag O-E ? POSS-1 O-E colour index of the quasar candidate
43- 47 F5.2 s dRA ? Difference between the radio position and
that of the quasar candidate (in the sense
radio minus optical)
49- 53 F5.1 arcsec dDE ? Difference between the radio position and
that of the quasar candidate (in the sense
radio minus optical)
55- 58 I4 mJy S.15 ? Flux density at 151 MHz, from
the 7C catalogue
60- 65 F6.1 mJy S1.5 ? Flux density either at 1.49GHz from our own
VLA observations (or 1.40GHz, see n_S1.5)
66 A1 --- n_S1.5 [)] ): S1.5 contains 1.40GHz flux density
from the NVSS survey
67 A1 --- f_S1.5 [mc] Not in NVSS, or confusion (3)
69- 73 F5.2 mJy SI ? Spectral index between 151MHz and 1.49GHz
(or 1.4 if n_SI=")")GHz
74 A1 --- n_SI [)] ): SI contains spectral index between
151MHz and 1.4GHz
75 A1 --- f_SI [c] Source confusion (3)
77- 81 F5.1 mJy Score ? Flux density of the core at 1.49GHz (4)
83- 84 A2 --- l_theta [≤ ] Limit flag on theta
85- 88 F4.1 arcsec theta ? Angular size of the source θ
89 A1 --- n_theta [?)c] Note on theta (5)
90- 91 A2 --- f_theta [7C ] 7C if theta from the 7C catalogue
92- 98 A7 --- Type Optical type (6)
100-102 A3 --- Rfl Flags associated with the radio data (7)
103 A1 --- Rem [*] * indicated a note in notes.dat file
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Note (1): Notes as follows:
N = new, the source was not in the first version of the optical catalogue
R = repeat entry because the optical object occurs in two POSS-I fields
S = there is more than one optically unresolved object in the field of
the source
* = this proposed identification failed the original selection criterion
on r (see column Sep)
T = there is more than one radio source in the field.
Note (2): The positions were measured from the radio core if present (i.e., if
there is an entry in column Score); where there is no core, the position is
midway between the radio hotspots, or the centroid of the radio emission; if
the source has not been observed at high resolution with the VLA, the
position is taken from the NVSS catalogue (Condon et al., 1998,
Cat J/AJ/115/1693) or (in a few cases marked 7C in column theta) the 7C
catalogue (McGilchrist et al., 1990, Cat. J/MNRAS/246/110).
Note (3): Note as follows:
m = in a few cases, there is no corresponding source in the NVSS survey
and/or no source was detected in higher resolution VLA observations
to a typical surface brightness upper limit of -1mJy per beam on
low-resolution (4"FWHM) maps made either from our own observations
or from the FIRST Survey data of Becker, White & Helfand
(1995ApJ...450..559B 1995ApJ...450..559B).
c = no value has been calculated because the value of SI is severely
overestimated because of source confusion.
Note (4): For well-resolved sources this is the height of the peak (in
mJy/beam) at the core position. For less well-resolved sources in
which it is impossible to distinguish the core from the surroundings
it is the total flux density given in column "S1.5".
Note (5): the symbol mean the following:
? = uncertainty which is discussed in the notes on that source.
If the entries in columns S1.5 and Score are the same, the size
was measured by fitting a Gaussian with the AIPS task IMFIT.
Otherwise the size was measured from the map.
) = largest angular size given in the NVSS catalogue
(or the 7C catalogue, if f_theta="7C")
c = the 7C catalogue entry is a confusion of two or more sources
Note (6): Types as follows:
Q = spectroscopically confirmed quasar (see Paper II)
QC = good ID which is optically unresolved but which has not not yet
been spectroscopically confirmed as a quasar or galaxy
S = proposed ID is a star
M = proposed ID rejected on positional grounds
G = confirmed galaxy
BL = confirmed BL Lac object
? = stellar on both the O and E plates, but ID not yet certain due to
lack of follow-up with the VLA and optical spectroscopy
EC1 = the object is non-stellar on the E plate
EC2 = the object is or confused on the E plate
OC0 = the object is noise-like on the O plate
OC1 = the object is nonstellar on the O plate
OC2 = the object is confused on the O plate
Note that some of the spectroscopically confirmed quasars are not
classified by the APM analysis as stellar on both POSS-1 plates.
(c) = the optical object is very likely to be an ID - the criterion being
that the NVSS and APM positions differ by <2" for unresolved
radio sources, and <6" for resolved sources.
Note (7): Note as follows:
Y = a map is presented in Fig. 3
y = map is presented in Fig. 3 and additional notes are to be found in
notes.dat file
N = a map was made but is not shown in Fig. 3 (typically because the
source is unresolved),
n = map was made but is not shown in Fig. 3 and additional notes in
notes.dat file
C = the only map available is from the NVSS low-resolution VLA survey
of Condon et al. (1998AJ....115.1693C 1998AJ....115.1693C)
++ = excluded from our high-resolution VLA follow-up because SI≤100mJy,
r = excluded because of the red optical colour of the proposed ID
(see Section 5),
l = excluded because of large 7C angular size
j = excluded randomly.
Other letters refer to additional sources of high-resolution radio maps
D = Law-Green et al. (1995MNRAS.274..939L 1995MNRAS.274..939L)
F = FIRST survey archive (Becker et al., 1995ApJ...450..559B 1995ApJ...450..559B)
M = Machalski & Condon (1986AJ.....91..998M 1986AJ.....91..998M)
L = Riley & Warner (1994MNRAS.269..166R 1994MNRAS.269..166R)
P = Patnaik et al. (1992, Cat. J/MNRAS/254/655)
V = Vigotti et al. (1989, Cat. J/AJ/98/419)
One entry in the 7C catalogue (at position 10:24:04.2, +48:43:30) is an alias
of a bright radio source, and its candidate identification a star.
S = Owen & Puschell (1984AJ.....89..932O 1984AJ.....89..932O) and
Reid et al. (1995A&AS..110..213R 1995A&AS..110..213R).
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Byte-by-byte Description of file: notes.dat
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Bytes Format Units Label Explanations
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1- 8 A8 --- Name Name (HHMM+DDm)
10 A1 --- --- [(]
11 I1 --- Table [1/2] Number of the table
12 A1 --- --- [)]
14- 80 A67 --- Note Text of the note
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History: Prepared via OCR at CDS.
(End) James Marcout, Patricia Bauer [CDS] 06-Dec-1999