J/MNRAS/434/2877 Extended radio sources in ATLBS (Thorat+, 2013)
Environments of extended radio sources in the Australia Telescope
Low-Brightness Survey.
Thorat K., Saripalli L., Subrahmanyan R.
<Mon. Not. R. Astron. Soc., 434, 2877-2891 (2013)>
=2013MNRAS.434.2877T 2013MNRAS.434.2877T
ADC_Keywords: Radio sources ; Redshifts ; Photometry
Keywords: methods: data analysis - methods: miscellaneous -
galaxies: evolution - galaxies: photometry - radio continuum: general
Abstract:
We present a study of the environments of extended radio sources in
the Australia Telescope Low-Brightness Survey (ATLBS). The radio
sources were selected from the ATLBS Extended Source Sample, which is
a well defined sample containing the most extended of radio sources in
the ATLBS sky survey regions. The environments were analysed using 4-m
Cerro-Tololo Inter-American Observatory Blanco telescope observations
carried out for ATLBS fields in the Sloan Digital Sky Survey r' band.
We have estimated the properties of the environments using smoothed
density maps derived from galaxy catalogues constructed using these
optical imaging data. The angular distribution of galaxy density
relative to the axes of the radio sources has been quantified by
defining anisotropy parameters that are estimated using a new method
presented here. Examining the anisotropy parameters for a subsample of
extended double radio sources that includes all sources with
pronounced asymmetry in lobe extents, we find good evidence for
environmental anisotropy being the dominant cause for lobe asymmetry
in that higher galaxy density occurs almost always on the side of the
shorter lobe, and this validates the usefulness of the method proposed
and adopted here. The environmental anisotropy parameters have been
used to examine and compare the environments of Fanaroff-Riley Class I
(FRI) and Fanaroff-Riley Class II (FRII) radio sources in two redshift
regimes (z<0.5 and z>0.5). Wide-angle tail sources and head-tail
sources lie in the most overdense environments. The head-tail source
environments (for the HT sources in our sample) display dipolar
anisotropy in that higher galaxy density appears to lie in the
direction of the tails. Excluding the head-tail and wide-angle tail
sources, subsamples of FRI and FRII sources from the ATLBS appear to
lie in similar moderately overdense environments, with no evidence for
redshift evolution in the regimes studied herein.
Description:
The ATLBS covers two adjacent regions in the southern sky, which we
refer to as ATLBS regions A and B. These are centred at RA=00:35:00s,
DE=-67:00:00 and RA=00:59:17, DE=-67:00:00 (J2000 epoch),
respectively. The radio observations were carried out using the
Australia Telescope Compact Array (ATCA). Details of the radio
observations and imaging have been presented in Subrahmanyan et al.
(2010MNRAS.402.2792S 2010MNRAS.402.2792S, Cat J/MNRAS/402/2792) and Thorat et al.
(2013ApJ...762...16T 2013ApJ...762...16T, Cat. J/ApJ/762/16).
Follow-up optical observations were carried out with the 4-m Blanco
Telescope at Cerro-Tololo Inter-American Observatory (CTIO), Chile.
The observations were carried out in Sloan Digital Sky Survey (SDSS)
r', g' and z' bands, using the Mosaic II imager. Each optical image
covers 37x37arcmin2 area in the sky. The Mosaic II imager covers
each image with two rows of eight CCDs, each of them 2048-pixels wide
and 4096-pixels long, giving a scale of 0.27arcsec/pix. In this work
we have used only the r'-band images.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 154 43 The sample along with the parameters ak and the
standard deviations in each of the parameters
table2.dat 57 80 Sources used to fit the magnitude-redshift relation
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See also:
J/MNRAS/402/2792 : Australia Telescope Low-Brightness Survey (ATLBS)
(Subrahmanyan+, 2010)
J/ApJ/762/16 : Australia Tel. Low-brightness Survey (ATLBS) (Thorat+, 2013)
Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
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1- 12 A12 --- ATLBS Source name (JHHMM.m+DDMM)
14- 27 A14 --- Name Extended source name (JHHMMSS+DDMMSS)
28- 29 A2 --- n_Name [** ] **: source from SUMSS (1)
31- 34 F4.2 --- z Redshift
35 A1 --- n_z [*] *: spectroscopically measured redshift
37- 39 A3 --- Type Source type (2)
41- 43 I3 deg PA [-90/360] Position angle
45- 48 F4.2 --- a1 Best value of overdensity parameter a1 (3)
50- 53 F4.2 --- ba1 Lower value of overdensity parameter a1 (3)
55- 58 F4.2 --- Ba1 Upper value of overdensity parameter a1 (3)
60- 63 F4.2 --- e_a1 Normalized standard deviation of a1
65- 69 F5.2 --- a2 Best value of overdensity parameter a2 (3)
71- 75 F5.2 --- ba2 Lower value of overdensity parameter a2 (3)
77- 81 F5.2 --- Ba2 Upper value of overdensity parameter a2 (3)
83- 86 F4.2 --- e_a2 Normalized standard deviation of a2
88- 92 F5.2 --- a3 Best value of Overdensity parameter a3 (3)
94- 98 F5.2 --- ba3 Lower value of overdensity parameter a3 (3)
100-104 F5.2 --- Ba3 Upper value of overdensity parameter a3 (3)
106-109 F4.2 --- e_a3 Normalized standard deviation of a3
111-115 F5.2 --- a4 Best value of Overdensity parameter a4 (3)
117-121 F5.2 --- ba4 Lower value of overdensity parameter a4 (3)
123-126 F4.2 --- Ba4 Upper value of overdensity parameter a4 (3)
128-131 F4.2 --- e_a4 Normalized standard deviation of a4
133-137 F5.2 --- a5 Best value of Overdensity parameter a5 (3)
139-143 F5.2 --- ba5 Lower value of overdensity parameter a5 (3)
145-149 F5.2 --- Ba5 Upper value of overdensity parameter a5 (3)
151-154 F4.2 --- e_a5 Normalized standard deviation of a5
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Note (1): Note as follows:
** = denotes a source designation taken from the Sydney University Molonglo
Sky Survey (SUMSS); Mauch et al. (2003MNRAS.342.1117M 2003MNRAS.342.1117M, Cat. VIII/81)
Note (2): Source type as follows:
I = FR I, Fanaroff-Riley Class I source
II = FR II, Fanaroff-Riley Class II source
HT = head-tail source
WAT = wide-angle tailed source
Note (3): ak gives the best estimate of the value of the parameter itself,
bak and Bak give the values it may have at ±5° from the listed PA,
giving the uncertainty in the parameter due to the uncertainty in PA.
(The angle made by the longer radio lobe with the east-west direction,
measured from north to east is designated as the PA of the source.
For WAT-HT sources, the bisecting direction instead of the direction of
the longer lobe is used to determine the radio axis in this study.)
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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 I1 h RAh Radio source Right ascension (J2000)
3- 4 I2 min RAm Radio source Right ascension (J2000)
6- 10 F5.2 s RAs Radio source Right ascension (J2000)
12 A1 --- DE- Radio source Declination sign (J2000)
13- 14 I2 deg DEd Radio source Declination (J2000)
16- 17 I2 arcmin DEm Radio source Declination (J2000)
19- 22 F4.1 arcsec DEs Radio source Declination (J2000)
24 I1 h RAOh Optical ID Right ascension (J2000)
26- 27 I2 min RAOm Optical ID Right ascension (J2000)
29- 33 F5.2 s RAOs Optical ID Right ascension (J2000)
35 A1 --- DEO- Optical ID Declination sign (J2000)
36- 37 I2 deg DEOd Optical ID Declination (J2000)
39- 40 I2 arcmin DEOm Optical ID Declination (J2000)
42- 45 F4.1 arcsec DEOs Optical ID Declination (J2000)
47- 51 F5.3 --- z Redshift
53- 57 F5.2 mag rmag r magnitude
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History:
From electronic version of the journal
(End) Patricia Vannier [CDS] 14-Sep-2014