J/MNRAS/360/1305 Polarization of extragalactic sources (Roy+, 2005)
Extragalactic sources towards the central region of the Galaxy.
Roy S., Rao A.P., Subrahmanyan R.
<Mon. Not. R. Astron. Soc., 360, 1305-1324 (2005)>
=2005MNRAS.360.1305R 2005MNRAS.360.1305R
ADC_Keywords: Radio sources ; Polarization
Keywords: techniques: polarimetric - H II regions - Galaxy: centre -
radio continuum: ISM
Abstract:
We have observed a sample of 64 small-diameter sources towards the
central -6<l<6, -2<b<2 of the Galaxy with the aim of studying the
Faraday rotation measure near the Galactic Centre region. All the
sources were observed at 6- and 3.6-cm wavelengths using the ATCA and
the VLA. 59 of these sources are inferred to be extragalactic. The
observations presented here constitute the first systematic study of
the radio polarization properties of the background sources towards
this direction and increase the number of known extragalactic radio
sources in this part of the sky by almost an order of magnitude. Based
on the morphology, spectral indices and lack of polarized emission, we
identify four Galactic HII regions in the sample.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 35 8 Journal of observations
table2.dat 110 46 Measured parameters of the polarized sources
from the ATCA data
table3.dat 120 45 Measured parameters of the polarized sources
from VLA data
table4.dat 110 11 Measured parameters of the unpolarized sources
from the ATCA data
table5.dat 111 7 Measured parameters of the unpolarized sources
from VLA data
table6.dat 178 67 Measured RM towards the background sources
towards the GC region
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See also:
VII/6 : Polarization of Extragalactic Radio Sources (Eichendorf+ 1980)
J/A+AS/39/379 : Linear Polarization of radio sources (Tabara+ 1980)
J/A+AS/135/571 : Extragalactic radio sources polarization (Zukowski+, 1999)
Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
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1- 10 A10 "YYYY-MM-DD" ObsDate Observation date
12- 15 A4 --- Tel Telescope
17- 19 A3 --- Conf Configuration of the telescope
21- 22 I2 h Obs.Time Observation time
24- 27 F4.2 GHz Freq1 Frequency of observation
29- 32 F4.2 GHz Freq2 Frequency of observation
34- 35 I2 --- Nobs Number of sources observed
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Byte-by-byte Description of file: table[2345].dat
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Bytes Format Units Label Explanations
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1- 13 A13 --- [RRS2005] Source name using Galactic coordinates
14- 15 A2 --- Comp [NSECW EX R ] Component (1)
17- 18 I2 h RAh Right ascension (J2000)
20- 21 I2 min RAm Right ascension (J2000)
23- 27 F5.2 s RAs Right ascension (J2000)
29 A1 --- DE- Declination sign (J2000)
30- 31 I2 deg DEd Declination (J2000)
33- 34 I2 arcmin DEm Declination (J2000)
36- 39 F4.1 arcsec DEs Declination (J2000)
41 A1 --- l_Smaj [~] Limit flag on deconvolved size
42- 45 F4.1 deg Smaj ? Major axis of the deconvolved size
47- 50 F4.1 deg Smin ? Minor axis of the deconvolved size
52- 54 I3 deg PA ? Position angle of the deconvolved size
55 A1 --- n_PA [*] *: size of the object measured from
the 8.5-GHz map.
57- 61 F5.1 mJy Speak Peak flux density at 4.8GHz
63- 67 F5.1 mJy Stot Total flux density at 4.8GHz
68 A1 --- n_Stot [ab] Note on Stot (2)
69- 73 F5.1 mJy SVLA ? Total flux density of the component at
4.8GHz as measured by the VLA GPS survey
75- 78 F4.1 % Pol ? Percentage polarization
79 A1 --- l_SI(8.5-4.8) Limit flag on SI(8.5-4.8)
80- 84 F5.2 --- SI(8.5-4.8) ? Spectral index between 8.5 and 4.8GHz
85 A1 --- n_SI(8.5-4.8) [s] Note on SI(8.5-4.8) (3)
87- 91 F5.2 --- SI(4.8-1.4) ? Spectral index between 4.8 and 1.4GHz
92- 94 A3 --- n_SI(4.8-1.4) [i!NL* GM GC] Note on SI(4.8-1.4) (3)
96-100 F5.2 --- SI(1.4-0.3) ? Spectral index between 1.4 and 0.3GHz
101 A1 --- f_SI(1.4-0.3) [*] * = Spectral index from 0.3 to 4.8GHz
in SI(4.8-1.4)
102-104 A3 --- n_SI(1.4-0.3) [i GM GC GM1] Note on SI(1.4-0.3) (3)
106-111 A6 --- Class Source classification (4)
113-120 A8 --- Name Other name
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Note (1): Component designations are C=central,
N=northern, S=southern, E=eastern, W=western,
EX=highly extended, R=ring type
Note (2): Flag on total flux density as follows:
a = Flux density of the component near the bottom of its map (Fig. 6)
b = Flux density of the component near the top of its map (Fig. 6)
Note (3): Notes on spectral indices as follows:
! = 1.4-GHz GPS flux density differs from NVSS by more than 20%
i = spectral index measured from integrated flux densities of components.
N = 1.4-GHz flux density taken from NVSS
L = flux density taken from Lazio et al. (1999)
GC = P-band flux density taken from LaRosa et al. (2000)
GM = P-band flux density taken from Roy & Rao (2002)
GM1 = P-band flux density taken from S. Bhatnagar (priv. comm.)
** = 1.4-GHz flux density unknown
s = few sources are extended over several synthesized beamwidths and
for these sources we have convolved the 8.5-GHz images to the
resolution at 4.8GHz and then made spectral index images. The
spectral indices of the individual components are measured from
these images.
Note (4): Classification as follows:
G = Galactic source
C+E = flat spectrum core with extended emission
FR-I = FR I morphological type
FR-II = FR II morphological type
EG-D = extragalactic source; double source
EG-SR = extragalactic source; slightly resolved
EG-T = extragalactic source; triple
EG-U = extragalactic source; unresolved source
EG-M = extragalactic source; multiple sources in the field
G-H II = Galactic source; H II region
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Byte-by-byte Description of file: table6.dat
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Bytes Format Units Label Explanations
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1- 13 A13 --- [RRS2005] Source name using Galactic coordinates
17- 18 I2 h RAh Right ascension (J2000)
20- 21 I2 min RAm Right ascension (J2000)
23- 28 F6.3 s RAs Right ascension (J2000)
30 A1 --- DE- Declination sign (J2000)
31- 32 I2 deg DEd Declination (J2000)
34- 35 I2 arcmin DEm Declination (J2000)
37- 42 F6.3 arcsec DEs Declination (J2000)
43- 47 I5 rad/m2 RM Rotation measure
49- 52 F4.1 rad/m2 e_RM rms uncertainty on RM
54- 56 F3.1 --- D ? Depolarization fraction between
4.8 and 8.5GHz (1)
58- 61 F4.1 % e_D ? Percentage error in D
63- 67 F5.1 --- theta Direction of the magnetic field
68- 71 F4.1 --- e_theta rms uncertainty on theta
73- 77 F5.2 --- chi2 Reduced Chi2 value
79- 82 I4 MHz Freq1 Observed frequency
84- 88 F5.1 deg PA1 [-90/90] Measured polarisation angle at Freq1
90- 92 F3.1 deg e_PA1 rms uncertainty in deg PA1
94- 97 I4 MHz Freq2 Observed frequency
99-103 F5.1 deg PA2 [-90/90] Measured polarisation angle at Freq2
105-107 F3.1 deg e_PA2 rms uncertainty in deg PA2
109-112 I4 MHz Freq3 Observed frequency
114-118 F5.1 deg PA3 [-90/90] Measured polarisation angle at Freq3
120-122 F3.1 deg e_PA3 rms uncertainty in deg PA3
124-127 I4 MHz Freq4 Observed frequency
129-133 F5.1 deg PA4 [-90/94] Measured polarisation angle at Freq4
135-137 F3.1 deg e_PA4 rms uncertainty in deg PA4
139-142 I4 MHz Freq5 ? Observed frequency
144-148 F5.1 deg PA5 [-90/90]? Measured polarisation angle at Freq5
150-152 F3.1 deg e_PA5 ? rms uncertainty in deg PA5
154-157 I4 MHz Freq6 ? Observed frequency
159-163 F5.1 deg PA6 [-95/90]? Measured polarisation angle at Freq6
165-167 F3.1 deg e_PA6 ? rms uncertainty in deg PA6
171-178 A8 --- Name Other name
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Note (1): The depolarization fraction is defined as the ratio of polarization
fraction of a source component between lower and higher frequency.
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History:
From electronic version of the journal
(End) Patricia Vannier [CDS] 13-Mar-2006