J/MNRAS/381/341 MRCR-SUMSS Ultra-steep-spectrum (USS) sample (Broderick+, 2007)
A new search for distant radio galaxies in the Southern hemisphere.
I. Sample definition and radio properties.
Broderick J.W., Bryant J.J., Hunstead R.W., Sadler E.M., Murphy T.
<Mon. Not. R. Astron. Soc., 381, 341-366 (2007)>
=2007MNRAS.381..341B 2007MNRAS.381..341B
ADC_Keywords: Surveys ; Galaxies, radio ; Polarization
Keywords: polarization - surveys galaxies: active - radio continuum: galaxies -
radio continuum: general
Abstract:
This paper introduces a new program to find high-redshift radio
galaxies in the Southern hemisphere through ultra-steep spectrum (USS)
selection. We define a sample of 234 USS radio sources with spectral
indices α843408≤-1.0 (Sν∝νalpha) and flux
densities S408≥200mJy in a region of 0.35sr, chosen by
cross-correlating the revised 408MHz Molonglo Reference Catalogue, the
843MHz Sydney University Molonglo Sky Survey and the 1400MHz NRAO VLA
Sky Survey in the overlap region -40°<DE←30°. We present
Australia Telescope Compact Array (ATCA) high-resolution 1384 and
2368MHz radio data for each source, which we use to analyse the
morphological, spectral index and polarization properties of our
sample. We find that 85 per cent of the sources have observed-frame
spectral energy distributions that are straight over the frequency
range 408-2368MHz, and that, on average, sources with smaller angular
sizes have slightly steeper spectral indices and lower fractional
linear polarization. Fractional polarization is anticorrelated with
flux density at both 1400 and 2368MHz. We also use the ATCA data to
determine observed-frame Faraday rotation measures for half of the
sample.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table3.dat 185 239 The MRCR-SUMSS USS sample
table4.dat 200 241 ATCA properties of individual radio components
table5.dat 75 32 Sources in the MRCR-SUMSS sample with likely
optical identifications in SuperCOSMOS
notes.dat 80 53 Individual notes
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See also:
VIII/65 : 1.4GHz NRAO VLA Sky Survey (NVSS) (Condon+ 1998)
J/A+AS/93/399 : Optical ident. of USS radio sources (Wieringa+ 1992)
J/A+AS/108/79 : Ultra-steep spectrum radio sources (Roettgering+, 1994)
J/A+AS/143/303 : Ultra steep spectrum radio sources catalog (De Breuck+ 2000)
J/AJ/123/637 : Ultra-steep-spectrum radio sources (De Breuck +, 2002)
J/MNRAS/355/20 : K magnitudes of 74MHz USS radio sources (Jarvis+, 2004)
J/A+A/436/457 : Ultra-steep spectrum radio sources (Gopal-Krishna+, 2005)
Byte-by-byte Description of file: table3.dat
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Bytes Format Units Label Explanations
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1- 4 A4 --- --- [NVSS]
6- 19 A14 --- NVSS NVSS designation (JHHMMSS+DDMMSS)
20 A1 --- f_NVSS Flag when associated data (G1)
21 A1 --- n_NVSS [abc] Note on NVSS (2)
23- 24 I2 h RAh NVSS Right ascension (J2000)
26- 27 I2 min RAm NVSS Right ascension (J2000)
29- 33 F5.2 s RAs NVSS Right ascension (J2000)
35 A1 --- DE- NVSS Declination sign (J2000)
36- 37 I2 deg DEd NVSS Declination (J2000)
39- 40 I2 arcmin DEm NVSS Declination (J2000)
42- 45 F4.1 arcsec DEs NVSS Declination (J2000)
47- 50 I4 mJy S408 Integrated flux density at 408MHz
52- 54 I3 mJy e_S408 rms uncertainty on 408MHz
56- 61 F6.1 mJy S843 Integrated flux density at 843MHz
63- 66 F4.1 mJy e_S843 rms uncertainty on 843MHz
68- 73 F6.1 mJy S1384 Integrated flux density at 1384MHz
75- 78 F4.1 mJy e_S1384 rms uncertainty on 1384MHz
80- 85 F6.1 mJy S1400 Integrated flux density at 1400MHz
87- 90 F4.1 mJy e_S1400 rms uncertainty on 1400MHz
92- 96 F5.1 mJy S2368 Integrated flux density at 2368MHz
98-101 F4.1 mJy e_S2368 rms uncertainty on 2368MHz
103-107 F5.2 --- alpha1 Two-point observed-frame spectral index
between 843 and 408MHz
109-112 F4.2 --- e_alpha1 rms uncertainty on alpha1
114-118 F5.2 --- alpha2 Two-point observed-frame spectral index
between 1400 and 843MHz
120-123 F4.2 --- e_alpha2 rms uncertainty on alpha2
125-129 F5.2 --- alpha3 Two-point observed-frame spectral index
between 2368 and 1384MHz
131-134 F4.2 --- e_alpha3 rms uncertainty on alpha3
136-140 F5.2 --- alpha ?=- Five-point fit spectral index (3)
142-145 F4.2 --- e_alpha ?=- rms uncertainty on alpha
146 A1 --- n_alpha [sf] (f)latten or (s)teepen spectrum (4)
148-151 F4.1 % pNVSS ?=- NVSS fractional linear polarization (5)
153-155 F3.1 % e_pNVSS ?=- rms uncertainty on pNVSS
157 A1 --- l_LAS Limit flag on LAS
158-161 F4.1 arcsec LAS Largest angular size at 2368MHz (6)
162 A1 --- --- [,]
163-166 F4.1 arcsec LAS2 ? Second value of LAS
168-172 F5.1 deg PA [-90/90]?=- Deconvolved position angle of the
radio structure at 2368MHz, measured from
the north to the east (7)
173 A1 --- --- [,]
174-178 F5.1 deg PA2 [-90/90]?=- Second value of Position angle
180-182 A3 --- MType Radio morphology at 2368MHz (8)
183 A1 --- --- [,]
184-185 A2 --- MType2 Second radio morphology at 2368MHz (8)
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Note (2): Note as follows:
a = NVSS J00475-6354409, NVSS J014813-384340 and NVSS J144245-373827
each contain a faint confusing source that is resolved by the
ATCA at 1384MHz (1384MHz flux densities 9.7, 4.1 and 6.9mJy,
respectively). The flux densities of these sources are included
in the total 1384MHz flux density.
b = NVSS J010619-325713 (narrow-angle tail morphology),
NVSS J014353-331041 (wide-angle tail morphology) and
NVSS J020827-342635 + NVSS J020828-342520 (complex morphology)
are low-redshift FR I-type radio sources.
See the notes on individual sources in notes.dat files.
c = NVSS J015745-310557 and NVSS J215547-344614 are both resolved
into two independent sources with the ATCA. The LAS, PA and
morphology classification are given for the north source first.
In NVSS J015745-310557, the 1384MHz flux densities for the north
and south doubles are 79.6±2.5 and 47.9±1.6mJy,
respectively, while the 2368MHz flux densities are 35.6±1.9
and 20.7±1.1mJy, respectively.
In NVSS J215547-344614, the 1384MHz flux densities for the
wide-angle tail and head-tail sources are 41.0±1.4 and
38.6±1.3mJy, respectively, while the 2368MHz flux densities
are 20.7±1.4 and 23.8±1.3mJy, respectively.
See the notes on individual sources in notes.dat file.
Note (3): The observed-frame spectral index based on a linear fit to all
five flux density data points.
Note (4): For those sources that have curved spectra that flatten (f) or
steepen (s) at high frequency, we use a quadratic fit to all five flux
density data points to derive the observed-frame spectral index at
1400MHz.
Note (5): Determined from the integrated polarized flux densities in
version 4.1 of the NVSS catalogue. We ignore those cases where the
polarized flux density has a negative estimated value (see Condon et
al. 1998, Cat. VIII/65)
Note (6): For single-component resolved sources, this is the deconvolved
major axis of the elliptical Gaussian used to fit the source.
* For unresolved sources, we have used the distribution of
deconvolved sizes to estimate a LAS upper limit of 2 arcsec.
* For multicomponent sources, the LAS is the angular separation of
the most widely separated components.
Note (7): For multicomponent sources, this is the orientation of the most
widely separated components used to calculate the LAS.
Note (8): Radio morphology as follows:
S = single component
D = double
T = triple
HT = head-tail
NAT = narrow-angle tail
WAT = wide-angle tail
C = complex
Di = incipient doubles in which the components are not fully resolved
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Byte-by-byte Description of file: table4.dat
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Bytes Format Units Label Explanations
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1- 4 A4 --- --- [NVSS]
6- 19 A14 --- NVSS NVSS designation (JHHMMSS+DDMMSS)
20- 24 A5 --- m_NVSS Multiplicity index on NVSS
(HT, ND, SD or WAT) (2)
25 A1 --- f_NVSS Flag when associated data (G1)
26 A1 --- n_NVSS [ab] Note on NVSS (2)
28- 32 F5.1 mJy S1384c ? 1384MHz integrated flux density of
central component (3)
34- 39 F6.1 mJy S1384 ? Total 1384MHz integrated flux density (4)
41- 45 F5.1 mJy S1384n ? 1384MHz integrated flux density of
north lobe (3)
46- 48 A3 --- n_S1384n [(EW) ] Note on S1384n (4)
50- 54 F5.1 mJy S1384s ? 1384MHz integrated flux density of
south lobe (3)
55- 57 A3 --- n_S1384s [(EW) ] Note on S1384s (4)
59- 63 F5.1 mJy S2368c ? 2368MHz integrated flux density of
central component (3)
64- 66 A3 --- n_S2368c [(EW) ] Note on S2368c (4)
68- 72 F5.1 mJy S2368 ? Total 2368MHz integrated flux density (4)
74- 78 F5.1 mJy S2368n ? 2368MHz integrated flux density of
north lobe (3)
79- 81 A3 --- n_S2368n [(EW) ] Note on S2368n (4)
83- 87 F5.1 mJy S2368s ? 2368MHz integrated flux density of
south lobe (3)
88- 90 A3 --- n_S2368s [(EW) ] Note on S2368s (4)
92- 96 F5.2 --- alpha1 ? Two-point spectral index between 2368MHz
and 1384MHz for central component (5)
98-102 F5.2 --- alpha2 ? Two-point spectral index between
2368MHz and 1384MHz for north lobe (5)
104-108 F5.2 --- alpha3 ? Two-point spectral index between
2368MHz and 1384MHz for south lobe (5)
110 A1 --- l_p1384c Limit flag on p1384c
111-114 F4.1 % p1384c ? 1384MHz fractional linear polarization
for the central component (6)
116-118 F3.1 % e_p1384c ? rms uncertainty on p1384c
120 A1 --- l_p1384n Limit flag on p1384n
121-124 F4.1 % p1384n ? 1384MHz fractional linear polarization
for the north lobe component (6)
126-128 F3.1 % e_p1384n ? rms uncertainty on p1384n
130 A1 --- l_p1384s Limit flag on p1384s
131-134 F4.1 % p1384s ? 1384MHz fractional linear polarization
for the south lobe component (6)
136-138 F3.1 % e_p1384s ? rms uncertainty on p1384s
140 A1 --- l_p2368c Limit flag on p2368c
141-144 F4.1 % p2368c ? 2368MHz fractional linear polarization
for the central component (6)
146-148 F3.1 % e_p2368c ? rms uncertainty on p2368c
150 A1 --- l_p2368n Limit flag on p2368n
151-154 F4.1 % p2368n ? 2368MHz fractional linear polarization
for the north lobe component (6)
155-157 A3 --- n_p2368n [(E) ] (E) when data for eastern component
159-162 F4.1 % e_p2368n ? rms uncertainty on p2368n
164 A1 --- l_p2368s Limit flag on p2368s
165-168 F4.1 % p2368s ? 2368MHz fractional linear polarization
for the south lobe component (6)
169-171 A3 --- n_p2368s [(W) ] (W) when data for weastern component
173-175 F3.1 % e_p2368s ? rms uncertainty on p2368s
177-180 I4 rad/m2 RMC ? Observed-frame Faraday rotation measure
for the central components (7)
182 I1 rad/m2 e_RMC ? rms uncertainty on RMC
184-187 I4 rad/m2 RMN ? Observed-frame Faraday rotation measure
for the north lobe components (7)
189 I1 rad/m2 e_RMN ? rms uncertainty on RMN
191-194 I4 rad/m2 RMS ? Observed-frame Faraday rotation measure
for the south lobe components (7)
196 I1 rad/m2 e_RMS ? rms uncertainty on RMS
198-200 I3 rad/m2 RM ? Galactic rotation measure (8)
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Note (2): Note as follows:
a = NVSS J010619-325713 (narrow-angle tail morphology),
NVSS J014353-331041 (wide-angle tail morphology) and
NVSS J020827-342635 + NVSS J020828-342520 (complex morphology)
are low-redshift FR I-type radio sources. See the notes on
individual sources in notes.dat file.
b = NVSS J015745-310557 and NVSS J215547-344614 are both resolved
into two independent sources with the ATCA.
* For NVSS J015745-310557:
ND = northern double SD = southern double
* For J215547-344614:
WAT = northern wide-angle tail source,
HT = southern head-tail source
See the notes on individual sources in notes.dat file.
Note (3): 1384MHz and 2368MHz integrated flux densities of the radio
components in each ATCA image: central component (C), north lobe (N)
and south lobe (S). The central component is the only entry for
sources with a single-component morphology at either 1384 or 2368MHz,
or, for triple sources, the core.
Note (4): Often there are more components present at 2368MHz than at
1384MHz because of the increase in angular resolution. We give the
combined flux density of the lobes in incipient doubles at either 1384
or 2368MHz (in S1384MHz and S2368MHz columns). For those sources where
the lobes are close to east- west, we also label the eastern lobe (E)
and the western lobe (W).
Note (5): The two-point spectral index α23681384 for the central
component, north lobe and south lobe, assuming that each component is
not blended at 1384MHz.
Note (6): 1384 and 2368MHz fractional linear polarization for the central,
north lobe and south lobe components, measured at the position of peak
intensity. A 3σ upper limit is given for source components with
undetected polarization.
Note (7): The observed-frame Faraday rotation measure (RM), not corrected
for the Galactic Faraday screen, for the central, north lobe and south
lobe components.
Note (8): Galactic RM determined from the all-sky RM map of
Johnston-Hollitt, Hollitt & Ekers (2004, in Uyaniker B., Reich W.,
Wielebinski R., eds, The Magnetized Interstellar Medium. Copernicus
GmbH, Katlenburg-Lindau, p. 13)
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Byte-by-byte Description of file: table5.dat
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Bytes Format Units Label Explanations
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1- 4 A4 --- --- [NVSS]
6- 19 A14 --- NVSS NVSS designation (JHHMMSS+DDMMSS)
20- 39 A20 --- NVSS2 Second NVSS name when combined data
41- 42 I2 h RAh Host galaxy Right ascension (J2000) (1)
44- 45 I2 min RAm Host galaxy Right ascension (J2000) (1)
47- 51 F5.2 s RAs Host galaxy Right ascension (J2000) (1)
53 A1 --- DE- Host galaxy Declination sign (J2000) (1)
54- 55 I2 deg DEd Host galaxy Declination (J2000) (1)
57- 58 I2 arcmin DEm Host galaxy Declination (J2000) (1)
60- 63 F4.1 arcsec DEs Host galaxy Declination (J2000) (1)
65 A1 --- l_Bjmag Limit flag on Bjmag
66- 69 F4.1 mag Bjmag BJ magnitude
71 A1 --- l_Rmag Limit flag on Rmag
72- 75 F4.1 mag Rmag R magnitude
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Note (1): Host galaxy coordinates are the SuperCOSMOS fitted positions in
the UKR images, except for those cases where the counterpart is
detected in the UKJ image only.
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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- 4 A4 --- --- [NVSS]
6- 19 A14 --- NVSS NVSS designation (JHHMMSS+DDMMSS)
21- 80 A60 --- Note Text of the note
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Global notes:
Note (G1): In five cases, the measurement are for two sources, as follows:
A = NVSS J023601-314204 + NVSS J023605-314235
B = NVSS J023641-324615 + NVSS J023645-324543
C = NVSS J024012-305742 + NVSS J024016-305710
D = NVSS J020827-342635 + NVSS J020828-342520
E = NVSS J211107-314058 + NVSS J211108-313958
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History:
From electronic version of the journal
(End) Patricia Vannier [CDS] 29-Sep-2008