J/ApJ/833/176 The magnetic field of L1544. I. NIR data (Clemens+, 2016)
The magnetic field of L1544.
I. Near-infrared polarimetry and the non-uniform envelope.
Clemens D.P., Tassis K., Goldsmith P.F.
<Astrophys. J., 833, 176-176 (2016)>
=2016ApJ...833..176C 2016ApJ...833..176C (SIMBAD/NED BibCode)
ADC_Keywords: Molecular clouds ; Polarization ; Photometry, infrared ;
Stars, normal
Keywords: Galaxy: disk; ISM: individual objects: L1544;
ISM: magnetic fields; magnetic fields; polarization;
techniques: polarimetric
Abstract:
The magnetic field (B-field) of the starless dark cloud L1544 has been
studied using near-infrared (NIR) background starlight polarimetry
(BSP) and archival data in order to characterize the properties of the
plane-of-sky B-field. NIR linear polarization measurements of over
1700 stars were obtained in the H band and 201 of these were also
measured in the K band. The NIR BSP properties are correlated with
reddening, as traced using the Rayleigh-Jeans color excess (H-M)
method, and with thermal dust emission from the L1544 cloud and
envelope seen in Herschel maps. The NIR polarization position angles
change at the location of the cloud and exhibit their lowest
dispersion there, offering strong evidence that NIR polarization
traces the plane-of-sky B-field of L1544. In this paper, the
uniformity of the plane-of-sky B-field in the envelope region of L1544
is quantitatively assessed. This allows evaluation of the approach of
assuming uniform field geometry when measuring relative mass-to-flux
ratios in the cloud envelope and core based on averaging of the radio
Zeeman observations in the envelope, as done by Crutcher et al.
(2009ApJ...692..844C 2009ApJ...692..844C). In L1544, the NIR BSP shows the envelope
B-field to be significantly non-uniform and likely not suitable for
averaging Zeeman properties without treating intrinsic variations.
Deeper analyses of the NIR BSP and related data sets, including
estimates of the B-field strength and testing how it varies with
position and gas density, are the subjects of later papers in this
series.
Description:
NIR imaging polarimetric observations of L1544 were conducted on the
UT nights of 2013 January 20, 2015 October 27 and 31, 2015 November 1
and 2, and 2016 January 27 and 31 using the Mimir instrument on the
1.83m Perkins Telescope, located outside Flagstaff, Arizona.
Six pointing centers ("fields") were selected toward a Center
direction (RAJ200=05:04:16.6, DEJ2000=+25:10:48), the four equatorial
NSEW directions offset by 6 arcmin from the Center, and one field to
the NW offset mostly diagonally by about 10.9 arcmin.
In addition, the AllWISE (Cutri+ 2013, II/328) catalog entries for the
field shown in Figure 1 were fetched, resulting in 3616 stars with a
detection in at least the WISE W1 (3.6um) band or W2 (4.5um) band.
These were positionally matched to the H-band catalog, yielding 1262
matches. The properties of the 450 H-band stars without WISE star
matches and the WISE stars without H-band star matches were similar in
being fainter than the subset of stars with H-to-WISE matches. The
combined data set of 1712 stars is listed in Table 1.
Objects:
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RA (ICRS) DE Designation(s)
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05 04 18 +25 11.1 L1544 = LDN 1544
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File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 234 1712 Stellar polarimetry and photometry in
the L1544 field
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See also:
I/340 : UCAC5 Catalogue (Zacharias+ 2017)
II/328 : AllWISE Data Release (Cutri+ 2013)
II/246 : 2MASS All-Sky Catalog of Point Sources (Cutri+ 2003)
J/A+A/555/A109 : 14N/15N isotopic ratio in L1544 (Bizzocchi+, 2013)
J/ApJS/182/143 : SCUPOL Legacy polarimetry of SCUBA (Matthews+, 2009)
Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
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1- 4 I04 --- Seq Star sequential number (1)
6- 13 F8.5 deg RAdeg Right Ascension in decimal degrees (J2000)
15- 22 F8.5 deg DEdeg Declination in decimal degrees (J2000)
24- 29 F6.3 mag mHmag [7.7/19] Mimir H band magnitude
31- 35 F5.3 mag e_mHmag [0/0.4] Uncertainty in mHmag
37- 42 F6.3 % Polp(H) [0/99.9] Debiased linear polarization, H band
44- 49 F6.3 % e_Polp(H) [0.03/99] Uncertainty in Polp(H)
51- 55 F5.1 deg PA(H) [0/180] Equatorial polarization position
angle (in deg E from N), H band
57- 61 F5.1 deg e_PA(H) [0.7/180] Uncertainty in PA(H)
63- 69 F7.3 % Q(H) [-100/92] Stokes Q in H band
71- 76 F6.3 % e_Q(H) [0.03/100] Uncertainty in Q(H)
78- 84 F7.3 % U(H) [-80/78] Stokes U in H band
86- 91 F6.3 % e_U(H) [0.03/100] Uncertainty in U(H)
93- 98 F6.3 mag mKmag [9.9/20] Mimir K band magnitude (2)
100-105 F6.3 mag e_mKmag [0/0.3]?=99.999 Uncertainty in mKmag
107-112 F6.3 % Polp(K) [0/88] Debiased linear polarization,
K band (2)
114-120 F7.3 % e_Polp(K) [0.1/100] Uncertainty in Polp(K) (2)
122-126 F5.1 deg PA(K) [0/180] Equatorial polarization position
angle (in deg E from N), K band (2)
128-132 F5.1 deg e_PA(K) [2/180] Uncertainty in PA(K) (2)
134-140 F7.3 % Q(K) [-49/100] Stokes Q in K band (2)
142-148 F7.3 % e_Q(K) [0.2/100] Uncertainty in Q(K) (2)
150-156 F7.3 % U(K) [-62/38] Stokes U in K band (2)
158-164 F7.3 % e_U(K) [0.1/100] Uncertainty in U(K) (2)
166-171 F6.3 mag Jmag [8.5/18.9]?=20 2MASS J magnitude
173-178 F6.3 mag e_Jmag [0.01/0.3]?=99.999 Uncertainty in Jmag
180-185 F6.3 mag Hmag [7.7/16.6]?=20 2MASS H magnitude
187-192 F6.3 mag e_Hmag [0.02/0.3]?=99.999 Uncertainty in Hmag
194-199 F6.3 mag Ksmag [7.5/16.8]?=20 2MASS Ks magnitude
201-206 F6.3 mag e_Ksmag [0.01/0.4]?=99.999 Uncertainty in Ksmag
208-213 F6.3 mag W1mag [7.3/17.5]?=20 AllWISE W1 band (3.6um) magnitude
215-220 F6.3 mag e_W1mag [0.02/0.3]?=99.999 Uncertainty in W1mag
222-227 F6.3 mag W2mag [7.4/17.3]?=20 AllWISE W2 band (4.5um) magnitude
229-234 F6.3 mag e_W2mag [0.01/1]?=99.999 Uncertainty in W2mag
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Note (1): Star 0606 is a foreground star
Note (2): Values of 20.000 in the Mimir K band mag column signify the absence
of a matching star. For those stars, the corresponding Polp entry was set
to zero, the uncertainty was set to 100.00, the polPA was set to zero,
with the uncertainty set to 180.00.
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History:
From electronic version of the journal
(End) Prepared by [AAS], Emmanuelle Perret [CDS] 26-Apr-2017