J/ApJS/283/54 VLA polarimetry of radio sources behind Perseus (Hajizadeh+, 2026)
A comprehensive catalog of radio sources and rotation measures in the Perseus
molecular cloud from Very Large Array observations.
Hajizadeh H., Stil J., Plume R., Tahani M., Jagannathan P.
<Astrophys. J. Suppl. Ser., 283, 54 (2026)>
=2026ApJS..283...54H 2026ApJS..283...54H
ADC_Keywords: Polarization; Radio sources; Molecular clouds; Interstellar medium
Keywords: Interstellar magnetic fields ; Interferometry ; Molecular clouds ;
Interstellar medium ; Starlight polarization ; Very Large Array
Abstract:
We present a comprehensive radio polarization study of the Perseus
molecular cloud using wideband L-band observations from the Karl G.
Jansky Very Large Array. Our survey covers ∼13.8deg2 with a mean
Stokes I sensitivity of ∼80µJy/beam, enabling the detection of
1410 compact radio sources. From this population, we construct a
catalog of source properties, including positions, integrated flux
densities, and spectral indices measured across nine spectral windows.
The majority of sources exhibit negative spectral indices, consistent
with nonthermal synchrotron emission. Using the rotation measure
(RM)-based RM Synthesis and RM CLEAN techniques, we detect
205 polarized background sources above an 8σ threshold. This
corresponds to a sampling density of ∼14.8deg-2, representing more
than an order of magnitude increase compared to previous NVSS-based
measurements. The resulting RMs exhibit coherent large-scale
variations across the surveyed region, with additional small-scale
structure superimposed. The enhanced sensitivity, frequency coverage,
and sampling density of our observations enable a substantially
improved mapping of the line-of-sight magnetic field component toward
the Perseus molecular cloud compared to previous surveys.
Description:
The observations for this study were conducted using the Karl G.
Jansky Very Large Array (VLA). The mosaic fields were arranged in a
hexagonal grid pattern consisting of 55 pointings designed to provide
uniform sensitivity across the Perseus molecular cloud. Each field
overlaps slightly with its neighbors to ensure continuous sky coverage
over an approximately circular area with a diameter of about 2.2deg2,
with an integration time of ∼2 minutes per field.
Two separate VLA observing programs covered the Perseus molecular
cloud: program 19B-053, obtained in 2019, and program 24A-376,
approved as follow-up observations in 2024.
In this paper, we focus on the 19B dataset; analysis of the 24A
follow-up observations will be presented in a forthcoming publication.
The spectrometer was set up to cover the whole L band (930-2070MHz) in
full polarization mode. The data were split into 18 spectral windows
(SPWs), each with a bandwidth of 64MHz.
Objects:
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RA (ICRS) DE Designation(s)
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03 35 00 +31 13 00 Perseus molecular cloud = NAME Perseus Cloud
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File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 358 753 *The RM catalog of true Faraday rotation detections
toward the Perseus cloud
(updated version by the author)
table2.dat 76 205 VLA L-band rotation measure catalog toward the
Perseus molecular cloud
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Note on table1.dat : Source positions and flux densities were derived
using PyBDSF on Stokes I images independently for each spectral
window. Integrated and peak flux densities are reported together with
the local RMS noise measured by PyBDSF in the vicinity of each source.
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See also:
VIII/65 : 1.4GHz NRAO VLA Sky Survey (NVSS) (Condon+ 1998)
VI/128 : Log of CGPS exposures (Taylor+, 2003-)
J/ApJ/638/293 : 1.1mm sources in the Perseus Molecular Cloud (Enoch+, 2006)
J/ApJ/702/1230 : Rotation measure image of the sky (Taylor+, 2009)
J/ApJ/728/97 : VLA rotation measures in the Galactic plane (Van Eck+, 2011)
J/ApJ/818/73 : Study of protostars in the Perseus cloud (Tobin+, 2016)
J/ApJ/818/116 : Gould's Belt VLA survey. V. Perseus region (Pech+, 2016)
J/A+A/597/A98 : Faraday tomography of foreground toward IC342 (Van Eck+, 2017)
J/A+A/614/A100 : Molecular clouds los magnetic field structure (Tahani+, 2018)
Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 5 A5 --- --- [VCPMC]
7- 22 A16 --- VCPMC Unique identifier for each source
(JHHMMSS.s+DDMMSS) (Source_ID) (G1)
24- 31 F8.5 deg RAdeg [50/54.8] Right Ascension of the source
(J2000) (RA)
33- 40 F8.5 deg DEdeg [28.7/32.3] Declination of the source (J2000)
(DEC)
42- 48 F7.5 deg e_RAdeg [0/0.005] Uncertainty in RA (E_RA)
50- 56 F7.5 deg e_DEdeg [0/0.005] Uncertainty in DEC (E_DEC)
58- 62 F5.2 --- alpha [-2.9/2.6]? Spectral index fitted across
SPWs 1-9 (alpha)
64- 68 F5.2 --- e_alpha [0.02/3.3]? Uncertainty in alpha (E_alpha)
70- 75 F6.2 mJy StotSPW1 [0.57/459]? Total integrated flux density in
SPW1 (TotalSSPW1)
77- 81 F5.2 mJy e_StotSPW1 [0.29/29]? Uncertainty in total integrated
flux density in SPW1 (ETotalS_SPW1)
83- 88 F6.2 mJy SpkSPW1 [0.8/401]? Peak flux density in SPW1 mJy/beam
(PeakSSPW1)
90- 94 F5.2 mJy e_SpkSPW1 [0.2/15]? Uncertainty in peak flux density in
SPW1 mJy/beam (EPeakS_SPW1)
96-100 F5.2 mJy rmsSPW1 [0.2/14.4]? Local RMS noise level in SPW1
mJy/beam (rms_SPW1)
102-107 F6.2 mJy StotSPW2 [0.76/443]? Total integrated flux density in
SPW2 (TotalSSPW2)
109-113 F5.2 mJy e_StotSPW2 [0.3/26]? Uncertainty in total integrated
flux density in SPW2 (ETotalS_SPW2)
115-120 F6.2 mJy SpkSPW2 [0.96/387]? Peak flux density in SPW2
mJy/beam (PeakSSPW2)
122-126 F5.2 mJy e_SpkSPW2 [0.2/12]? Uncertainty in peak flux density
in SPW2 mJy/beam (EPeakS_SPW2)
128-132 F5.2 mJy rmsSPW2 [0.2/12]? Local RMS noise level in SPW2
mJy/beam (rms_SPW2)
134-139 F6.2 mJy StotSPW3 [0.69/421]? Total integrated flux density in
SPW3 (TotalSSPW3)
141-145 F5.2 mJy e_StotSPW3 [0.3/29.2]? Uncertainty in total integrated
flux density in SPW3 (ETotalS_SPW3)
147-152 F6.2 mJy SpkSPW3 [0.8/371]? Peak flux density in SPW3 mJy/beam
(PeakSSPW3)
154-158 F5.2 mJy e_SpkSPW3 [0.2/15]? Uncertainty in peak flux density
in SPW3 mJy/beam (EPeakS_SPW3)
160-164 F5.2 mJy rmsSPW3 [0.2/15]? Local RMS noise level in SPW3
mJy/beam (rms_SPW3)
166-171 F6.2 mJy StotSPW4 [0.3/481]? Total integrated flux density in
SPW4 (TotalSSPW4)
173-177 F5.2 mJy e_StotSPW4 [0.19/49]? Uncertainty in total integrated
flux density in SPW4 (ETotalS_SPW4)
179-184 F6.2 mJy SpkSPW4 [0.6/400]? Peak flux density in SPW4 mJy/beam
(PeakSSPW4)
186-190 F5.2 mJy e_SpkSPW4 [0.17/19.4]? Uncertainty in peak flux density
in SPW4 mJy/beam (EPeakS_SPW4)
192-196 F5.2 mJy rmsSPW4 [0.19/19]? Local RMS noise level in SPW4
mJy/beam (rms_SPW4)
198-203 F6.2 mJy StotSPW5 [0.79/579]? Total integrated flux density in
SPW5 (TotalSSPW5)
205-209 F5.2 mJy e_StotSPW5 [0.27/41]? Uncertainty in total integrated
flux density in SPW5 (ETotalS_SPW5)
211-216 F6.2 mJy SpkSPW5 [0.6/466]? Peak flux density in SPW5 mJy/beam
(PeakSSPW5)
218-222 F5.2 mJy e_SpkSPW5 [0.17/21]? Uncertainty in peak flux density
in SPW5 mJy/beam (EPeakS_SPW5)
224-228 F5.2 mJy rmsSPW5 [0.17/19.5]? Local RMS noise level in SPW5
mJy/beam (rms_SPW5)
230-235 F6.2 mJy StotSPW6 [0.4/608]? Total integrated flux density in
SPW6 (TotalSSPW6)
237-241 F5.2 mJy e_StotSPW6 [0.2/37.1]? Uncertainty in total integrated
flux density in SPW6 (ETotalS_SPW6)
243-248 F6.2 mJy SpkSPW6 [0.5/533]? Peak flux density in SPW6
mJy/beam (PeakSSPW6)
250-254 F5.2 mJy e_SpkSPW6 [0.15/19.5]? Uncertainty in peak flux
density in SPW6 mJy/beam (EPeakS_SPW6)
256-260 F5.2 mJy rmsSPW6 [0.15/19.1]? Local RMS noise level in SPW6
mJy/beam (rms_SPW6)
262-267 F6.2 mJy StotSPW7 [0.3/662]? Total integrated flux density in
SPW7 (TotalSSPW7)
269-273 F5.2 mJy e_StotSPW7 [0.18/43.1]? Uncertainty in total integrated
flux density in SPW7 (ETotalS_SPW7)
275-280 F6.2 mJy SpkSPW7 [0.59/585]? Peak flux density in SPW7
mJy/beam (PeakSSPW7)
282-286 F5.2 mJy e_SpkSPW7 [0.15/23]? Uncertainty in peak flux density
in SPW7 mJy/beam (EPeakS_SPW7)
288-292 F5.2 mJy rmsSPW7 [0.15/22.3]? Local RMS noise level in SPW7
mJy/beam (rms_SPW7)
294-299 F6.2 mJy StotSPW8 [0.88/542]? Total integrated flux density in
SPW8 (TotalSSPW8)
301-305 F5.2 mJy e_StotSPW8 [0.28/43.1]? Uncertainty in total integrated
flux density in SPW8 (ETotalS_SPW8)
307-312 F6.2 mJy SpkSPW8 [0.7/500]? Peak flux density in SPW8
mJy/beam (PeakSSPW8)
314-318 F5.2 mJy e_SpkSPW8 [0.17/23.5]? Uncertainty in peak flux density
in SPW8 mJy/beam (EPeakS_SPW8)
320-324 F5.2 mJy rmsSPW8 [0.16/23.2]? Local RMS noise level in SPW8
mJy/beam (rms_SPW8)
326-333 F8.3 mJy StotSPW9 [0.5/1017.3]? Total integrated flux density in
SPW9 (TotalSSPW9)
335-339 F5.2 mJy e_StotSPW9 [0.27/67.1]? Uncertainty in total integrated
flux density in SPW9 (ETotalS_SPW9)
341-347 F7.3 mJy SpkSPW9 [0.67/785.7]? Peak flux density in SPW9
mJy/beam (PeakSSPW9)
348-353 F6.3 mJy e_SpkSPW9 [0.18/32.3]? Uncertainty in peak flux density
in SPW9 mJy/beam (EPeakS_SPW9)
354-358 F5.2 mJy rmsSPW9 [0.18/31]? Local RMS noise level in SPW9
mJy/beam (rms_SPW9)
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Byte-by-byte Description of file: table2.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 5 A5 --- --- [VCPMC]
7- 22 A16 --- VCPMC Unique identifier for each source
(JHHMMSS.s+DDMMSS) (Source_ID) (G1)
24- 31 F8.5 deg RAdeg [49.8/55] Right Ascension of the source (J2000)
33- 40 F8.5 deg DEdeg [28.7/32.2] Declination of the source (J2000)
42- 47 F6.2 rad/m2 RM [-41.5/92.1] Rotation Measure (1)
49- 52 F4.2 rad/m2 e_RM [0.03/4.6] Uncertainty in RM (dRM)
54- 58 F5.2 % fPol [0.17/50] Fractional Polarization of source
(fracPol)
60- 65 F6.2 mJy/beam Stot [0.4/272] Total flux density in reference
frequency (S_reffreq)
67- 72 F6.2 uJy/beam RMS [17.6/645.3] Local RMS noise level for the
polarized source (rms)
74 I1 --- F1 [0/2]? Flag indicating the location of the
source relative to diffuse Galactic polarized
emission (2)
76 I1 --- F2 [0/1] Flag indicating Faraday complexity of
the source based on the Faraday dispersion
function (0=single peak; or 1=multiple peaks)
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Note (1): Rotation measures were derived using RM synthesis and RM CLEAN.
Note (2): Flag as follows:
0 = outside diffuse emission,
1 = inside diffuse emission,
2 = inside diffuse emission with polarized intensity greater than
twice the maximum value within the diffuse mask.
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Global notes:
Note (G1): The prefix VCPMC stands for VLA Catalogue of the
Perseus Molecular Cloud.
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Acknowledgements:
Haleh Hajizadeh [haleh.hajizadeh at ucalgary.ca]
History:
From electronic version of the journal
* Table1 updated by the author (notably, VCPMC names have been corrected;
truncated at JHHMMSS.s+DDMMS in the original table)
License: CC-BY-4.0
(End) Prepared by [AAS], Emmanuelle Perret [CDS] 27-Aug-2026