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Mon. Not. R. Astron. Soc.
408,
2261–2278 (2010)
doi:10.1111/j.1365-2966.2010.17271.x
A survey of low-luminosity compact sources and its implication for
the evolution of radio-loud active galactic nuclei – I. Radio data
M. Kunert-Bajraszewska,
1
M. P. Gawro´ ski,
1
A. Labiano
2
and A. Siemiginowska
3
n
1
Toru´
n
Centre for Astronomy, N. Copernicus University, Gagarina 11, 87-100 Toru´ , Poland
n
Space Agency (ESA), European Space Astronomy Centre (ESAC), 28691 Villanueva de la Canada, Madrid, Spain
3
Harvard-Smithsonian Center for Astrophysics, 60 Garden St, Cambridge, MA 02138, USA
2
European
Accepted 2010 June 29. Received 2010 June 29; in original form 2010 April 28
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at Uniwersytet Mikolaja Kopernika w Toruniu on July 8, 2016
ABSTRACT
We present a new sample of compact steep spectrum (CSS) sources with radio luminosity
below 10
26
W Hz
−1
at 1.4 GHz; these are called low-luminosity compact (LLC) objects. The
sources have been selected from the Faint Images of the Radio Sky at Twenty-cm (FIRST)
survey and observed with the multi-element radio linked interferometer network (MERLIN)
at the
L
and
C
bands. The main criterion used for selection was the luminosity of the objects,
and approximately one-third of the CSS sources from the new sample have a value of radio
luminosity comparable to Fanaroff–Riley type 1 sources (FR Is). About 80 per cent of the
sources have been resolved and about 30 per cent have weak extended emission and disturbed
structures when compared with the observations of higher-luminosity CSS sources. We have
studied the correlation between radio power and linear size, and the redshift with a larger
sample that also included published samples of compact objects and large-scale FR IIs and FR
Is. In the radio power versus linear size diagram, the LLC objects occupy the space below the
main evolutionary path of radio objects. We suggest that many of these might be short-lived
objects, and their radio emission may be disrupted several times before they become FR IIs.
We conclude that there exists a large population of short-lived LLC objects unexplored so far,
and some of these could be precursors to large-scale FR Is.
Key words:
galaxies: active – galaxies: evolution.
1 I N T RO D U C T I O N
Radio sources are divided into two distinct morphological groups
of objects: Fanaroff–Riley type 1 and type II sources (FR Is and FR
IIs; Fanaroff & Riley 1974). There is a relatively sharp luminosity
boundary between these at low frequency. The nature of the FR
division is still an open issue, as are the details of the evolutionary
process in which younger and smaller GHz-peaked spectrum (GPS)
and compact steep spectrum (CSS) sources become large-scale ra-
dio structures. It is unclear whether FR II objects evolve to become
FR Is, or whether a division has already occurred amongst CSS
sources and some of these then become FR Is and some FR IIs. A
majority of CSS sources known to date have high radio luminosi-
ties and, if unbeamed, have FR II structures. It seems reasonable to
suspect that some of the CSS sources with lower radio luminosity
could be the progenitors of less luminous FR I objects.
The GPS and CSS sources form a well-defined class of compact
radio objects and are considered to be entirely contained within
the host galaxy. During their evolution, the radio jets start to cross
E-mail: magda@astro.uni.torun.pl
C
the interstellar medium (ISM) and try to leave the host galaxy. The
interaction with the ISM can be very strong in GPS/CSS sources
(Labiano et al. 2005; Holt, Tadhunter & Morganti 2006), and this
seems to be a crucial point in the evolution of radio sources. Recently
developed models (Kaiser & Best 2007) show that all sources start
out with a FR II morphology. As the radio source expands, the
interaction with the dense environment of the host galaxy can disrupt
jets and change their morphology to FR Is or hybrid objects (Gopal-
Krishna & Wiita 2000; Gawro´ ski et al. 2006). Some sources with
n
disrupted jets can fade away (Alexander 2000). The detection of
several candidates for dying compact sources supports this view
(Giroletti, Giovannini & Taylor 2005; Kunert-Bajraszewska et al.
2005; Kunert-Bajraszewska, Marecki & Thomasson 2006; Marecki,
Kunert-Bajraszewska & Spencer 2006). Furthermore, the activity
of compact radio sources can be an episodic event (Snellen et al.
1999; Marecki, Spencer & Kunert 2003b; Gugliucci et al. 2005;
Kunert-Bajraszewska, Marecki & Thomasson 2006), as in the case
of large-scale radio objects.
As recently suggested by Czerny et al. (2009), there could be
a connection between the existence of short-lived compact radio
sources and the intermittent activity of the central engine caused by
a radiation pressure instability within an accretion disc. According
2010 The Authors. Journal compilation
C
2010 RAS
2262
M. Kunert-Bajraszewska et al.
we blanked out all the points for which we observed
P <
3σ , to
avoid possible misuse of low signal-to-noise polarization data. The
flux densities of the main components of the target sources were
then measured, by fitting Gaussian models to the components in the
image, using the task
JMFIT
(Table 2). For more extended features,
the flux densities were evaluated by means of
IMSTAT
. The subcom-
ponents are referred to as north (N), south (S), east (E), west (W)
and central (C). When a component is split into more pieces, a
digit (1, 2, etc.) is added (e.g. N1, N2). The positions of the op-
tical counterparts of the target sources are marked with a cross in
the images and are taken from the SDSS (found within a radius of
10 arcsec from the radio source) or from the literature. The feature
in the radio image closest to the cross is indicated as ‘C’ and is
treated as the probable radio core.
Based upon available radio images (our MERLIN
L-band
and
C-band
observations, and others found in the literature), the new
sources have been divided into four categories (Table 1). However,
for most of the sources described here we have an observation only
at one frequency and the classification of these should be treated as a
preliminary one (‘a’ means the most uncertain classification). ‘Sin-
gle’ means the source is a point-like object, unresolved or slightly
resolved. ‘Core-jet’ is a source with a bright central component and
a one- or two-sided emission (jets). ‘Double-lobed’ objects show
at least two types of morphologies. Some of these consist of two
point-like components without a visible radio core in the available
radio images, whereas the others show a central weak component
and a distorted extended structure on both sides of this. Many of
the double objects also show brightness asymmetry. For some of
them (those with probable core detection) we were able to evalu-
ate the flux density ratio,
r
s
, defined to be
>1,
of the oppositely
directed components. The last category, ‘other’, comprises sources
with peculiar morphologies: three objects have distorted radio mor-
phologies, another three have only a single visible lobe, and one
object is resolved into four components with high-resolution imag-
ing. Figs 1–3 show images of the sources with resolved structures,
with the exception of one object (1641+320), which will be de-
scribed in a separate paper.
In this paper, we present the analysis of MERLIN radio observa-
tions of a new sample of low-luminosity CSS sources. We study the
correlation between radio power and linear size, and redshift, mak-
ing use of a larger sample which also includes published samples
of CSS sources by Fanti et al. (2001) and Marecki et al. (2003a).
The combined sample of CSS sources that we have used in our
study is gathered in Table A1 (see Appendix A). The optical data
of the sample of low-luminosity CSS sources will be discussed in
a forthcoming paper (Kunert-Bajraszewska & Labiano 2010; here-
after Paper II).
Throughout the paper, we assume a cosmology with
H
0
=
=
0.73.
71 km s
−1
Mpc
−1
,
M
=
0.27 and
3 N OT E S O N I N D I V I D UA L S O U R C E S
0025+006.
The 1.6-GHz MERLIN map (Fig. 1) shows an asym-
metric morphology: the brightest central component is probably a
radio core and the extended south-eastern emission is a radio jet
(E).
0801+437.
This source is unresolved in the 1.6-GHz MERLIN
observations and only 1.6-GHz European Very Long Baseline Inter-
ferometry Network (EVN) observations show a structure classified
as a possible double object by de Vries et al. (2009).
0810+077.
This source has been classified as a possible
double object (Fig. 1). The weak component (C), whose
C
to the authors, a radio source powered by a short-lived outburst
of the central activity is not able to escape from the host galaxy
unless the active phase lasts longer than
∼10
4
yr. It is then likely
that among the low-luminosity compact (LLC) sources we can find
objects affected during their evolution either by a strong interaction
with the ISM, which changes their morphology and luminosity, or
by the instability of the accretion disc.
In this paper we present the
L-band
and
C-band
observations,
made using the multi-element radio linked interferometer network
(MERLIN), of 44 low-luminosity CSS sources selected from the
Faint Images of the Radio Sky at Twenty-cm (FIRST) survey. This
is a new approach, as the main criterion used for selection was not the
flux density but the luminosity of the objects. The selection criteria
result in approximately one-third of the CSS sources from the new
sample having a value of radio luminosity lower than the luminosity
boundary found for FR sources (Fanaroff & Riley 1974). This means
that they are compact young sources with luminosities comparable
to FR Is. The goal of this project is to study the properties of
LLC objects and the evolution of the compact object population.
Our previous multifrequency observations of CSS sources have
shown that some of the small-scale objects can be strong candidates
for compact faders (Kunert-Bajraszewska et al. 2005, 2006). This
finding supports the idea that there exists a group of short-lived
radio objects that has been largely neglected to date.
2 S E L E C T I O N A N D O B S E RVAT I O N S O F
A NEW SAMPLE
Using the final release of FIRST, combined with the Green Bank
6-cm (GB6) survey at 4.85 GHz, we looked for unresolved, isolated
sources, that is, more compact than the FIRST beam (5.4 arcsec),
and surrounded by an empty field (we adopted 1 arcmin as the radius
of that field). We required that the redshifts of the objects identified
with radio sources were known, and we extracted these from the
National Aeronautics and Space Administration (NASA)/Infrared
Processing and Analysis Center (IPAC) Extragalactic Data base
(NED) and the Sloan Digital Sky Survey (SDSS). Consequently,
we were able to impose the low power criterion. The limit on flux
density was chosen in order to produce a sample of manageable
size, but also to exclude objects with flux densities too low to be
detected in snapshot observations. Eventually, the selection criteria
were as follows:
(i) low-luminosity criterion,
L
1.4GHz
<
10
26
W Hz
−1
(for H
0
=
100 km s
−1
Mpc
−1
, q
0
=
0.5; in this paper we use another cosmol-
ogy);
(ii) flux density criterion, 70 mJy
≤
S
1.4GHz
≤
1 Jy;
4.85 GHz
(iii) spectral index criterion,
α
1.4GHz
>
0.7(S
∝
�½
−α
).
Finally, the new sample consists of 44 sources (Table 1).
The initial survey was undertaken using MERLIN at the
L
band.
Then, some of the sources were also observed with MERLIN at the
C
band. All the
L-band
snapshot observations were made between
2006 December and 2007 May. Additional
C-band
snapshot obser-
vations were made in 2008 and 2009. Each target source, together
with its associated phase reference sources, was observed for
∼60
min, including telescope drive times. The preliminary data reduc-
tion was made using an
AIPS
-based
PIPELINE
procedure developed
at Jodrell Bank Observatory (JBO). The resulting phase-calibrated
images created with
PIPELINE
were further improved using several
cycles of self-calibration and imaging. The final total intensity (I)
and polarization intensity (P) images were produced using the task
IMAGR
. We considered only emission above the 3σ noise level, and
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2010 The Authors. Journal compilation
C
2010 RAS, MNRAS
408,
2261–2278
Survey of low-luminosity compact sources – I
2263
Table 1.
Basic parameters of the 44 target sources. A description of the columns is as follows: (1) source name; (2), (3) source coordinates (J2000) extracted
from the FIRST survey; (4) optical identification (G, galaxy; Q, quasar; q, star-like object; Gp, galaxy pair; Qb, binary quasar); (5) redshift; (6) total flux density
at 1.4 GHz extracted from the FIRST survey; (7) log of the radio luminosity at 1.4 GHz; (8) total flux density at 4.85 GHz extracted from the GB6 survey;
(9) log of the radio luminosity at 4.85 GHz; (10) spectral index between 1.4 and 4.85 GHz, calculated using the flux densities in columns (6) and (8); (11)
largest linear size (LLS) calculated based on the largest angular size measurements in the 1.4-GHz MERLIN image, in most cases as a separation between the
outermost component peaks, otherwise measured in the image contour plot (in the case of single sources, the linear size means the upper limit estimated using
the deconvolved component major axis angular size from the
L-band
MERLIN image); (12) radio morphology based on the available radio images, a simple
classification in agreement with that of Kunert-Bajraszewska & Thomasson (2009), with a more detailed description in Section 2 (S, single means unresolved
or slightly resolved in the available radio image; Cj, core–jet; D, double-lobed; O, other, more complex structures).
Source
name
(1)
0025+006
0754+401
0801+437
0810+077
0821+321
0835+373
0846+017
0850+024
0851+024
0854+210
0907+049
0914+114
0914+504
0921+143
0923+079
0931+033
0942+355
1007+142
1009+053
1037+302
1053+505
1140+058
1154+435
1156+470
1308+451
1321+045
1359+525
1402+415
1407+363
1411+553
1418+053
1506+345
1521+324
1532+303
1542+390
1543+465
1550+444
1558+536
1601+528
1610+407
1624+049
1641+320
1715+499
1717+547
RA
hms
(2)
00:28:33.42
07:57:56.69
08:04:54.91
08:13:23.76
08:25:04.55
08:38:25.00
08:48:56.56
08:53:14.23
08:54:08.45
08:57:20.98
09:09:51.13
09:17:16.38
09:17:34.82
09:24:05.29
09:26:07.99
09:34:30.74
09:45:25.89
10:09:55.51
10:12:04.73
10:40:29.96
10:56:28.21
11:43:11.03
11:57:27.60
11:59:19.99
13:10:57.00
13:24:19.70
14:00:51.62
14:04:16.37
14:09:42.46
14:13:27.21
14:21:04.25
15:08:05.68
15:23:49.35
15:34:09.90
15:43:49.49
15:45:25.46
15:52:35.37
15:59:27.66
16:02:46.39
16:11:48.55
16:26:50.30
16:43:11.35
17:16:46.34
17:18:54.40
Dec.
◦
ID
(4)
G
G
G
Q
G
Q
G
G
G
G
G
G
Q
Q
Q
G
G
Q
G
G
Q
Q
Q
G
G
G
G
G
G
G
G
Gp
G
q
G
G
G
G
G
G
G
Qb
G
G
z
(5)
0.104
0.066
0.123
b
0.112
0.265
0.396
0.349
0.460
0.399
0.032
0.640
c
0.178
b
0.633
0.135
0.442
0.225
0.208
0.213
0.460
c
0.091
0.820
0.497
0.230
0.467
0.391
0.263
0.118
0.361
0.148
0.282
0.455
0.045
0.110
0.001
d
0.553
0.400
0.452
0.179
0.106
0.151
0.040
c
0.586
0.628
0.147
(3)
00:55:11.00
39:59:36.00
43:35:37.20
07:34:05.80
31:59:57.30
37:10:36.90
01:36:47.40
02:14:53.70
02:13:15.80
20:48:53.80
04:44:22.13
11:13:36.90
50:16:38.20
14:10:21.60
07:45:26.60
03:05:45.50
35:21:03.50
14:01:54.30
05:06:13.20
29:57:58.00
50:19:52.20
05:35:15.90
43:18:06.80
46:45:44.80
44:51:46.60
04:19:07.20
52:16:06.60
41:17:48.80
36:04:16.00
55:05:29.30
05:08:44.90
34:23:23.30
32:13:50.10
30:12:04.00
38:56:01.40
46:22:44.70
44:19:06.10
53:30:54.70
52:43:58.70
40:40:20.90
04:48:50.50
31:56:18.00
49:56:44.30
54:41:48.20
S
1.4
Jy
(6)
0.219
0.098
0.352
0.435
0.076
0.383
0.085
0.112
0.118
0.082
0.178
0.742
0.104
0.105
0.158
0.280
0.140
0.995
0.206
0.364
0.079
0.194
0.247
0.081
0.097
0.128
0.170
0.210
0.141
0.126
0.283
0.121
0.168
0.071
0.189
0.459
0.139
0.170
0.557
0.553
0.162
0.113
0.095
0.323
logL
1.4
W Hz
−1
(7)
24.77
24.00
25.13
25.14
25.21
26.32
25.54
25.94
25.82
23.27
26.49
25.81
26.24
24.69
26.05
25.61
25.24
26.11
26.21
24.87
26.40
26.26
25.58
25.82
25.71
25.43
24.78
25.96
24.91
25.49
26.33
23.75
24.71
20.17
26.36
26.41
26.02
25.17
25.19
25.52
23.77
26.20
26.20
25.26
S
4.85
Jy
(8)
0.081
0.030
0.135
0.158
0.030
0.148
0.034
0.034
0.039
0.033
0.049
0.124
0.039
0.031
0.056
0.119
0.042
0.390
0.055
0.107
0.032
0.061
0.106
0.031
0.034
0.046
0.064
0.073
0.045
0.033
0.108
0.044
0.051
0.030
0.049
0.110
0.049
0.058
0.208
0.166
0.056
0.041
0.035
0.110
logL
4.85
W Hz
−1
(9)
24.34
23.49
24.72
24.70
24.81
25.91
25.14
25.42
25.33
22.87
25.93
25.03
25.82
24.17
25.60
25.24
24.71
25.70
25.63
24.33
26.01
25.76
25.21
25.40
25.25
24.98
24.35
25.50
24.41
24.91
25.91
23.31
24.19
19.80
25.77
25.79
25.56
24.71
24.76
25.00
23.31
25.76
25.76
24.80
4.85
α
1.4
h
−1
(10)
0.80
0.95
0.77
0.82
0.75
0.76
0.74
0.96
0.89
0.76
1.04
1.44
0.79
0.98
0.83
0.69
0.97
0.75
1.06
0.98
0.73
0.93
0.68
0.77
0.84
0.82
0.78
0.85
0.92
1.08
0.77
0.81
0.96
0.70
1.09
1.15
0.84
0.86
0.79
0.97
0.85
0.82
0.80
0.87
LLS
kpc
(11)
Type
(12)
Cj
a
S
D
a
D
a
D
S
Cj
D
D
O
D
a
O
D
Cj
O
Cj
D
D
D
a
D
D
Cj
Cj
O
D
a
D
S
S
Cj
a
S
S
O
S
S
D
D
a
O
D
a
D
Cj
a
D
O
e
D
D
3.13
0.25
0.44
2.78
7.69
1.01
6.12
5.98
3.41
1.76
8.32
0.68
4.86
0.73
7.94
1.61
4.41
3.26
8.71
3.63
8.19
16.97
4.55
4.98
3.85
16.90
0.42
1.00
0.07
0.80
1.67
0.15
0.40
0.004
8.08
6.57
6.90
5.08
0.38
2.60
1.94
10.56
2.38
0.18
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at Uniwersytet Mikolaja Kopernika w Toruniu on July 8, 2016
Notes
a
The most uncertain classification.
b
The uncertain redshift probably belongs to a random foreground galaxy.
c
The photometric redshift is taken from the
literature or the SDSS.
d
The spectroscopic redshift is very uncertain because of the poor quality of the spectrum.
e
1641+320 will be described in a separate
paper.
position is correlated with the position of the optical counter-
part, could be a radio core, on opposite sides of which there
is emission from the two radio jets/lobes. The flux density ra-
tio,
r
s
, of the oppositely directed components E and W amounts
to 1.7.
C
0821+321.
This is a double object with two weak radio lobes
without evidence of bright hotspots and a radio core (Fig. 1).
0846+017.
This is probably a core–jet morphology (Fig. 1) with
the brightest components being a radio core (C) and a bent radio jet
(S1, S2).
2010 The Authors. Journal compilation
C
2010 RAS, MNRAS
408,
2261–2278
2264
M. Kunert-Bajraszewska et al.
Table 2.
Flux densities of the principal components of the sources from the 1.6- and 5-GHz MERLIN images.
Source
name
0025+006
0810+077
Components
S
1.6 GHz
mJy
66
41
53
103
175
35
33
36
15
6
44
38
50
53
57
123
21
8
51
32
–
62
–
–
–
–
11
61
26
482
291
150
9
26
16
171
40
6
32
S
5 GHz
mJy
−
–
–
–
–
–
–
–
–
–
–
–
–
–
6
–
–
–
–
–
18
–
1.5
8
7
83
–
18
–
–
–
–
–
–
–
–
–
–
–
Source
name
1140+058
1154+435
Components
S
1.6 GHz
mJy
125
22
36
186
−
−
–
30
32
59
13
38
49
99
a
–
–
–
4
53
119
9
127
90
99
98
–
–
6
21
28
514
69
47
46
33
S
5 GHz
mJy
–
–
32
–
17
9
0.5
4
–
–
–
–
–
14
4
3
8
–
–
–
–
–
–
–
–
11
7
–
–
–
–
13
15
–
–
0821+321
0846+017
0850+024
0851+024
0854+210
0907+049
0914+504
0921+143
0923+079
0931+033
0942+355
1007+142
1009+053
1037+302
1053+505
C
E
C
E
W
E
W
C
S1
S2
E
W
E
W
C
b
C
N
S
N
S
C
N
C
N1
N2
b
C
C
E
W
N
S
E
W
E
E1
W
E
E1
W
1156+470
1308+451
1321+045
1506+345
1542+390
1543+465
1550+444
1558+536
1610+407
1624+049
1715+499
C
W
C
N
N1
N2
C
W
C
W
C
E
W
C
N1
N2
S
C
E
W
C
N
N1
S
N
N1
N2
b
C
N
S
C
E
W
E
W
Downloaded from
http://mnras.oxfordjournals.org/
at Uniwersytet Mikolaja Kopernika w Toruniu on July 8, 2016
Notes.
a
The whole source.
b
The sum of the visible components.
0850+024.
This is a compact double object (Fig. 1). The position
of the optical counterpart probably indicates the position of the
slightly resolved radio core.
0851+024.
This is a compact double object with a symmetric
morphology (Fig. 1).
0854+210.
This is a weak radio galaxy with diffuse morphology
(Fig. 2) also detected in infrared (Drake et al. 2003). The peak of
emission in the 1.6-GHz MERLIN image is a radio core, also visible
in the 5-GHz MERLIN image (C).
0907+049.
This is a double object with the brightest central
component (C) probably containing a radio core, on opposite sides
of which there is emission from the two radio jets/lobes (Fig. 1).
However, the polarization is not detected in the southern compo-
nent, which could be an artefact. The polarized flux density of
components C and N amount to 3 and 6 mJy, respectively.
0914+114.
Both the 1.6-GHz and 5-GHz MERLIN images show
a single component. This source has been resolved, using very
long baseline interferometry at 2.3 GHz, into a complex structure
consisting of four well-separated components (Xiang et al. 2005).
0914+504.
This is a quasar with a double morphology and asym-
metric polarization. The luminosity of the polarized southern com-
ponent is lower than the northern component, which could contain
a radio core (Fig. 1). The polarized flux density of component S
amounts to 4 mJy.
0921+143.
The 1.6-GHz MERLIN observation shows a single
component, which is resolved in the 5-GHz MERLIN image into a
probable core–jet morphology (Fig. 2).
0923+079.
The 1.6-GHz morphology and the position of the
optical counterpart suggest there is only a single lobe visible in
this source (Fig. 3). This interpretation is in agreement with the 5-
GHz MERLIN image. The weak point emission is probably a radio
core and the lobe indicated as ‘N’ in the 1.6-GHz image breaks
into weak and probably fading components in the 5-GHz MERLIN
image.
C
2010 The Authors. Journal compilation
C
2010 RAS, MNRAS
408,
2261–2278
Survey of low-luminosity compact sources – I
0025+006
00 55 13.0
1658.000 MHz
2265
0810+077
07 34 08.0
1658.000 MHz
12.5
C
07.5
E
07.0
DECLINATION (J2000)
12.0
C
W
DECLINATION (J2000)
11.5
06.5
E
11.0
06.0
10.5
05.5
10.0
05.0
09.5
04.5
Downloaded from
http://mnras.oxfordjournals.org/
at Uniwersytet Mikolaja Kopernika w Toruniu on July 8, 2016
09.0
00 28 33.55
33.45
33.40
33.35
RIGHT ASCENSION (J2000)
peak flux density=29.01 mJy/beam, beam size=550x140 mas
first contour level=1.00 mJy/beam
Pol line 1 arcsec=5 mJy/beam
0821+321
1658.000 MHz
33.50
33.30
04.0
08 13 23.90
23.80
23.75
23.70
23.65
RIGHT ASCENSION (J2000)
peak flux density=115.02 mJy/beam, beam size=271x191 mas
first contour level=1.70 mJy/beam
Pol line 1 arcsec=5 mJy/beam
0846+017
1658.000 MHz
23.85
31 59 59.0
01 36 49.5
58.5
49.0
C
58.0
DECLINATION (J2000)
48.5
DECLINATION (J2000)
E
57.5
57.0
48.0
47.5
S2
47.0
46.5
56.5
W
S1
56.0
46.0
55.5
45.5
55.0
08 25 04.70
02 14 56.0
04.65
04.60
04.55
04.50
04.45
RIGHT ASCENSION (J2000)
peak flux density=5.74 mJy/beam, beam size=193x158 mas
first contour level=0.63 mJy/beam
Pol line 1 arcsec=5 mJy/beam
0850+024
1658.000 MHz
04.40
08 48 56.70
56.60
56.55
56.50
RIGHT ASCENSION (J2000)
peak flux density=26.58 mJy/beam, beam size=273x193 mas
first contour level=0.66 mJy/beam
Pol line 1 arcsec=5 mJy/beam
0851+024
1658.000 MHz
56.65
56.45
02 13 18.0
55.5
17.5
55.0
DECLINATION (J2000)
E
W
W
DECLINATION (J2000)
17.0
54.5
16.5
E
54.0
16.0
53.5
15.5
53.0
15.0
52.5
14.5
52.0
08 53 14.35
14.25
14.20
14.15
14.10
RIGHT ASCENSION (J2000)
peak flux density=37.74 mJy/beam, beam size=272x181 mas
first contour level=0.70 mJy/beam
Pol line 1 arcsec=5 mJy/beam
14.30
14.0
08 54 08.55
08.50
08.45
08.40
08.35
RIGHT ASCENSION (J2000)
peak flux density=31.28 mJy/beam, beam size=291x169 mas
first contour level=0.68 mJy/beam
Pol line 1 arcsec=5 mJy/beam
Figure 1.
MERLIN
L-band
images. Contours increase by a factor of 2, the first contour level corresponds to
≈3σ
and vectors represent the polarized flux
density. A cross indicates the position of an optical object found using the most actual version of the SDSS Data Release 7 (DR7).
C
2010 The Authors. Journal compilation
C
2010 RAS, MNRAS
408,
2261–2278

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