J/ApJS/253/48 New rotation measures from the CGPS (Van Eck+, 2021)
Revisiting rotation measures from the Canadian Galactic Plane Survey: the
magnetic field in the disk of the outer galaxy.
Van Eck C.L., Brown J.C., Ordog A., Kothes R., Landecker T.L., Cooper B.,
Rae K.M., Del Rizzo D.A., Gray A.D., Ransom R., Reid R.I., Uyaniker B.
<Astrophys. J. Suppl. Ser., 253, 48 (2021)>
=2021ApJS..253...48V 2021ApJS..253...48V
ADC_Keywords: Magnetic fields; Polarization; Galactic plane; Surveys; Pulsars;
Radio sources
Keywords: Catalogs ; Milky Way magnetic fields ; Polarimetry
Abstract:
Faraday rotation provides a valuable tracer of magnetic fields in the
interstellar medium; catalogs of Faraday rotation measures provide key
observations for studies of the Galactic magnetic field. We present a
new catalog of rotation measures derived from the Canadian Galactic
Plane Survey, covering a large region of the Galactic plane spanning
52°<l<192°, -3°<b<5°, along with northern and southern
latitude extensions around l∼105°. We have derived rotation
measures for 2234 sources (4 of which are known pulsars), 75% of which
have no previous measurements, over an area of approximately 1300deg2.
These new rotation measures increase the measurement density for this
region of the Galactic plane by a factor of 2.
Description:
The details of the Canadian Galactic Plane Survey (CGPS) 1.4GHz
observations and subsequent processing through to the final images are
reported in full detail by Landecker+ (2010A&A...520A..80L 2010A&A...520A..80L).
For our analysis, we have used the data from the Synthesis Telescope
at the Dominion Radio Astrophysical Observatory (DRAO-ST) only.
Observations for the survey began in 1995 and continued in several
phases until 2009.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
cgps_rm.dat 298 2234 The Canadian Galactic Plane Survey (CGPS)
Faraday rotation measures catalog
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Description of file:
Also available on the FTP, the original FITS file: CGPS_RMTable.fits
(see Tables 2 and 3).
See also:
B/psr : ATNF Pulsar Catalogue (Manchester+, 2005)
VI/128 : Log of CGPS exposures (Taylor+, 2003-)
J/A+AS/39/379 : Linear Polarization of radio sources (Tabara+ 1980)
J/ApJS/145/213 : Rotation measures of compact sources in CGPS (Brown+, 2003)
J/ApJ/642/868 : Rotation measures for 223 pulsars (Han+, 2006)
J/ApJ/663/258 : Rotation measures of extragal. sources in SGPS (Brown+, 2007)
J/ApJ/702/1230 : Rotation measure image of the sky (Taylor+, 2009)
J/ApJ/714/1170 : Faraday rotation at high Galactic latitude (Mao+, 2010)
J/ApJ/728/97 : VLA rotation measures in the Galactic plane (Van Eck+, 2011)
J/ApJ/755/21 : Rotation measures of extragalactic radio sources (Mao+, 2012)
J/AJ/153/113 : The CGPS 1420 MHz catalog of compact sources (Taylor+, 2017)
J/AJ/154/156 : High res. survey of Galactic plane at 408 MHz (Tung+, 2017)
J/A+A/614/A100 : Molecular clouds los magnetic field structure (Tahani+, 2018)
J/A+A/613/A58 : Polarized point sources in LOTSS-HETDEX (Van Eck+, 2018)
J/other/Galax/7.43 : Faraday rotation of extended emission (Ordog+, 2019)
J/ApJ/887/L7 : Faraday rotation of radio sources from THOR (Shanahan+, 2019)
Byte-by-byte Description of file: cgps_rm.dat
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Bytes Format Units Label Explanations
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1- 8 F8.4 deg RAdeg Right ascension (J2000) (ra) (1)
10- 17 F8.4 deg DEdeg Declination (J2000) (dec) (1)
19- 25 F7.3 deg GLON Galactic longitude (l) (1)
27- 33 F7.3 deg GLAT Galactic latitude (b) (1)
35- 40 F6.4 deg posErr [0.0025] Position uncertainty (pos_err) (2)
42- 49 F8.2 rad/m2 RM Rotation measure
51- 55 F5.2 rad/m2 e_RM RM uncertainty (rm_err)
57 A1 --- Flag [U] Faraday complex flag (always "U"=unknown)
(complex_flag)
59- 73 A15 --- Method [-EVPA-linear fit] RM determination method
(always "EVPA-linear fit") (rm_method)
75- 78 A4 --- Iono [None] Ionospheric correction method
(always "None") (ionosphere)
80 I1 --- Nc [1] Number of component (always "1") (Ncomp)
82- 88 F7.5 mJy/beam stokesI Stokes I intensity (3)
90- 98 F9.7 GHz refSI [1.4207809] Stokes I reference frequency
(always "1.4207809") (reffreq_I)
100-106 F7.5 mJy/beam PI Polarized intensity (polint) (4)
108-126 A19 --- rBias [1974ApJ...194..249W 1974ApJ...194..249W] Polarization bias
correction method
(always "1974ApJ...194..249W 1974ApJ...194..249W") (pol_bias)
128-131 A4 --- Ftype [Peak] Flux type (always "Peak") (flux_type)
133-137 F5.3 --- PFrac Fractional polarization determined as the
average over the on-source pixels (fracpol)
139-147 F9.7 GHz refPol [1.4207809] Polarization reference frequency
(always "1.4207809") (reffreq_pol)
149-154 F6.4 deg beam_maj Beam major axis (5)
156-163 F8.6 deg beam_min [0.016111] Beam minor axis
(always "0.016111" =58") (5)
165-167 F3.1 deg beam_pa [0] Beam position angle (always "0.0") (5)
169-177 F9.7 GHz refBeam [1.4207809] Beam reference frequency
(always "1.4207809") (reffreq_beam)
179-186 F8.6 GHz minfreq [1.407194] Minimum frequency
(always "1.407194")
188-194 F7.5 GHz maxfreq [1.43463] Maximum frequency (always "1.43463")
196-198 F3.1 MHz ChWidth [7.5] Channel width (always "7.5")
(channelwidth)
200 I1 --- Nch [4] Number of channels (always "4") (Nchan)
202-208 A7 --- Tel [-DRAO-ST] Telescope (always "DRAO-ST")
(telescope)
210-214 I5 d MJD Median observing epoch (epoch) (6)
216-217 I2 d Int [60] Interval of observation
(always "60") (interval) (7)
219-237 A19 --- Cat [2021ApJS..253...48V 2021ApJS..253...48V] Catalog
(always "2021ApJS..253...48V 2021ApJS..253...48V"=This paper)
(catalog)
239-248 A10 --- ID Sequential number or pulsar name (cat_id) (8)
250-260 I11 --- IID Internal identifier
(always "-2147483648") (id)
262-267 A6 --- Class Source classification (type) (9)
269-278 A10 --- --- [Morphology] (flagA_name)
280-282 A3 --- Morph Morphology flag (flagA_value) (10)
284-294 A11 --- --- [Mosaic name] (flagB_name)
296-298 A3 --- Mosaic CGPS mosaic in which the source was found
(flagB_value)
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Note (1): Positions in Galactic and equatorial coordinates. The positions are
defined as the coordinates of the pixel closest to the location of the
Stokes I source, as reported by Taylor+ (2017, J/AJ/153/113) or AEGEAN
(Hancock+ 2012MNRAS.422.1812H 2012MNRAS.422.1812H & 2018PASA...35...11H 2018PASA...35...11H).
Note (2): Since these positions are quantized in units of the pixel size
(0.005°), the uncertainty in position is half the pixel size.
Note (3): Stokes I intensity, determined as the highest Stokes I value of
the on-source pixels.
Note (4): Polarized intensity (PI), determined as the highest
(foreground-subtracted and debiased) polarized intensity of the
on-source pixels.
Note (5): The beam major axis, which depends on decl., determined as
58" cosec δ (the beam minor axis and position angle were
constant for all sources).
Note (6): The observation date, defined as the center of the approximately
two-month period during which each mosaic was observed. This should be
treated as approximate, because some mosaics had a few fields
re-observed at a later time, and also the observation dates were
supplied to us quantized to the nearest month.
Note (7): Interval between the first and last observations used. This value is
approximate; most fields were observed repeatedly over a period of two
months with different baseline configurations to produce the final
images.
Note (8): A source ID number, running from 1 to 2230 for the non-pulsar sources
and giving the pulsar name for each of the four pulsars.
Note (9): The four pulsars are labeled as such; all other sources remain
unclassified.
Note (10): Morphology flags from the manual inspection, defined as follows:
C = Compact (2231 occurrences)
N = Neighbouring source within approximately 1' (2 occurrences)
R = Resolved (in Stokes I and polarization, unless otherwise flagged)
S = Subset (polarized intensity morphology is smaller than the Stokes I
extent)
P = Additional polarized component(s) seen in source or in neighbor
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Acknowledgements:
Cameron Van Eck [utoronto.ca]
History:
From electronic version of the journal
(End) Emmanuelle Perret [CDS] 30-Jun-2021