J/ApJ/905/157 Optical and NIR polarimetry in Taurus (Vaillancourt+, 2020)
Probing interstellar grain growth through polarimetry in the Taurus cloud
complex.
Vaillancourt J.E., Andersson B.-G., Clemens D.P., Piirola V., Hoang T.,
Becklin E.E., Caputo M.
<Astrophys. J., 905, 157 (2020)>
=2020ApJ...905..157V 2020ApJ...905..157V
ADC_Keywords: Molecular clouds; Polarization; Interstellar medium; Extinction;
Spectral types; Optical; Infrared sources
Keywords: Starlight polarization ; Interstellar dust ; Polarimetry ;
Spectropolarimetry ; Interstellar dust extinction ;
Interstellar clouds ; Interstellar medium
Abstract:
The optical and near-infrared (OIR) polarization of starlight is
typically understood to arise from the dichroic extinction of that
light by dust grains whose axes are aligned with respect to a local
magnetic field. The size distribution of the aligned-grain population
can be constrained by measurements of the wavelength dependence of the
polarization. The leading physical model for producing the alignment
is that of radiative alignment torques (RATs), which predicts that the
most efficiently aligned grains are those with sizes larger than the
wavelengths of light composing the local radiation field. Therefore,
for a given grain-size distribution, the wavelength at which the
polarization reaches a maximum (λmax) should correlate with
the characteristic reddening along the line of sight between the dust
grains and the illumination source. A correlation between
λmax and reddening has been previously established for
extinctions up to AV∼4mag. We extend the study of this relationship
to a larger sample of stars in the Taurus cloud complex, including
extinctions AV>10mag. We confirm the earlier results for AV∼4mag
but find that the λmax versus AV relationship bifurcates
above AV∼4mag, with part of the sample continuing the previously
observed relationship. The remaining sample exhibits a steeper rise in
λmax versus AV. We propose that the data exhibiting the
steep rise represent lines of sight of high-density "clumps," where
grain coagulation has taken place. We present RAT-based modeling
supporting these hypotheses. These results indicate that multiband OIR
polarimetry is a powerful tool for tracing grain growth in molecular
clouds, independent of uncertainties in the dust temperature and
emissivity.
Description:
We used the TurPol instrument on the 2.5m Nordic Optical Telescope
(NOT) at Roque de los Muchachos Observatory on La Palma, during the
nights of 2007 November 3-6, to perform broadband multicolor
polarimetry of stars background to the Taurus molecular cloud.
See Section 2.2.
We performed spectropolarimetric observations of high-extinction lines
of sight using the red channel (0.4-1.1um) of the Kast
spectropolarimeter on the 3m Shane telescope of Lick Observatory
during the nights of 2009 November 15-17 (UT). See Section 2.3.
Imaging polarimetric observations in the near-infrared H band (1.63um)
took place on the nights of 2011 September 18 and 19 and again on 2012
January 11 using the Mimir instrument on the 1.83m Perkins telescope,
located outside Flagstaff, Arizona. See Section 2.4.
File Summary:
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FileName Lrecl Records Explanations
--------------------------------------------------------------------------------
ReadMe 80 . This file
table1.dat 56 62 NOT/TurPol sources
table2.dat 103 25 Stellar target sample for optical spectropolarimetry
table3.dat 77 310 Photo-polarimetry results from the low-extinction
sample
table4.dat 86 371 Spectropolarimetry and H-band results for the
high-extinction sample
table9.dat 88 84 Standard high-polarization stars for Kast
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See also:
III/92 : A Library of Stellar Spectra (Jacoby+ 1984)
V/73 : Emission-Line Stars of the Orion Population (Herbig+ 1988)
I/259 : The Tycho-2 Catalogue (Hog+ 2000)
III/231 : The Tycho-2 Spectral Type Catalog (Wright+, 2003)
I/297 : NOMAD Catalog (Zacharias+ 2005)
II/349 : The Pan-STARRS release 1 (PS1) Survey - DR1 (Chambers+, 2016)
II/336 : AAVSO Photometric All Sky Survey (APASS) DR9 (Henden+, 2016)
I/347 : Distances to 1.33 billion stars in Gaia DR2 (Bailer-Jones+, 2018)
I/345 : Gaia DR2 (Gaia Collaboration, 2018)
V/154 : Sloan Digital Sky Surveys (SDSS), Release 16 (DR16) (Ahumada+, 2020)
J/AJ/130/873 : Properties of BQS objects in the SDSS DR3 area (Jester+, 2005)
J/ApJ/665/369 : Photopolarimetry of Southern Coalsack stars (Andersson+, 2007)
J/A+A/492/277 : Analysis of Collinder 69 stars with VOSA (Bayo+, 2008)
J/ApJS/176/457 : Taurus dark cloud background star catalog (Shenoy+, 2008)
J/A+A/502/845 : Dust coagulation in molecular clouds (Ormel+, 2009)
J/ApJS/186/259 : Taurus Spitzer survey: new candidate members (Rebull+, 2010)
J/ApJS/196/4 : New young star candidates in Taurus-Auriga (Rebull+, 2011)
J/ApJ/741/21 : Polarization of stars in Taurus (Chapman+, 2011)
J/ApJ/786/97 : Photospheric properties of T Tauri stars (Herczeg+, 2014)
J/ApJ/849/157 : Polarimetry obs. toward IC5146 background stars (Wang+, 2017)
J/A+A/630/A137 : Structure and kinematics of the Taurus region (Galli+, 2019)
J/MNRAS/510/6085 : Magnetic field of Taurus/B211 (Li+, 2022)
Byte-by-byte Description of file: table1.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 8 A8 --- Name Star name
10- 11 I2 h RAh [4] Hour of right ascension (J2000)
13- 14 I2 min RAm [2/53] Minute of right ascension (J2000)
16- 19 F4.1 s RAs Second of right ascension (J2000)
21 A1 --- DE- [+] Sign of declination (J2000)
22- 23 I2 deg DEd [22/29] Degree of declination (J2000)
25- 26 I2 arcmin DEm Arcminute of declination (J2000)
28- 31 F4.1 arcsec DEs Arcsecond of declination (J2000)
33- 36 F4.1 mag Vmag [6.3/11.4] V magnitude from SIMBAD
38- 41 F4.2 --- Ratio [1.6/6.7] Total-to-selective extinction ratio
(RV)
43- 46 F4.2 --- e_Ratio [0.25/5.33] Ratio uncertainty (σRV)
48- 51 F4.2 mag Av [0.58/2.82] Visual extinction
53- 56 F4.2 mag e_Av [0.06/0.17] Av uncertainty
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Byte-by-byte Description of file: table2.dat
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Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 8 A8 --- Name Star name ("SWIWNNN" ; "NNN"=recno in
Shenoy+ 2008, J/ApJS/176/457)
10- 25 A16 --- OName Other name(s)
27- 28 I2 h RAh [4] Hour of right ascension (J2000)
30- 31 I2 min RAm [9/44] Minute of right ascension (J2000)
33- 36 F4.1 s RAs Second of right ascension (J2000)
38 A1 --- DE- [+] Sign of declination (J2000)
39- 40 I2 deg DEd [22/30] Degree of declination (J2000)
42- 43 I2 arcmin DEm Arcminute of declination (J2000)
45- 48 F4.1 arcsec DEs Arcsecond of declination (J2000)
50- 53 F4.1 mag Vmag [10.9/17.1] V-band brightnesses from the NOMAD
compilation
55- 57 A3 --- SpT Spectral type estimated from this work (1)
59- 62 F4.2 mag Av [1.3/9.1]? Visural extinction from
Shenoy+ (2008, J/ApJS/176/457)
64- 66 F3.1 mag e_Av [0.5/0.9]? Av uncertainty
68- 71 F4.1 mag Ratio1 [2.3/12.2]? Extinction ratio
(RV=1.1*E(V-K)/E(B-V)) (2)
73- 75 F3.1 mag e_Ratio1 [0.1/2]? Ratio1 uncertainty
77- 80 F4.1 mag Ratio2 [2.1/11]? Extinction ratio, RV (3)
82- 84 F3.1 mag e_Ratio2 [0.1/3.1]? Ratio2 uncertainty
86- 89 A4 --- Ref Source of visual photometry (4)
91- 94 I4 pc Dist [131/3355] Distance from Gaia DR2
96- 98 I3 pc e_Dist [1/710] Lower uncertainty on Dist
100-103 I4 pc E_Dist [1/1015] Upper uncertainty on Dist
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Note (1): Spectral classes estimated from this work (see Section 2.3).
Uncertainties on all classes are one to two subclasses.
Note (2): RV=1.1*E(V-K)/E(B-V) based on the spectral classes given in
Column "SpT" and photometry from AAVSO (Henden+ 2016, II/336), SDSS,
and 2MASS.
Note (3): RV based on the spectral classes given in column "SpT" and fits of
E(λ-V)/E(B-V) using data from AAVSO (Henden+ 2016, II/336),
SDSS, 2MASS, and WISE.
Note (4): Source of visual photometry in order of preference as follows:
A = AAVSO (Henden+ 2016, II/336);
S = SDSS (Sloan Digital Sky Survey);
P = Pan-STARRS (Chambers+, 2016, II/349).
For SWIW051, while AAVSO data exist, the resulting fits are poor.
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Byte-by-byte Description of file: table3.dat
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Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 8 A8 --- Name Star name
10- 14 F5.3 um lambda [0.36/0.83] Wavelength of bin center (1)
16- 21 F6.3 % q [-3.21/2.8] q Stokes parameter q=Q/I
23- 31 E9.3 % e_q [0.01/0.15] Uncertainty in q
33- 38 F6.3 % u [-2.33/5.6] u Stokes parameter u=U/I
40- 48 E9.3 % e_u [0.01/0.15] Uncertainty in u
50- 53 F4.2 % p [0/6.25] Polarization amplitude,
corrected for positive bias
55- 62 E8.2 % e_p [0.01/0.15] Uncertainty in p
64- 68 F5.1 deg PA [0.2/179.4]? Polarization Angle (θ);
east of north (G1)
70- 77 E8.2 deg e_PA [0.09/9.42]? Uncertainty in PA
(σθ) (G1)
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Note (1): Wavelength centers for broad-band filters U, B, V, R, and I are
assigned as 0.36, 0.44, 0.55, 0.69, 0.83 micron
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Byte-by-byte Description of file: table4.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 8 A8 --- Name Star name
10- 14 F5.3 um lambda [0.48/1.63] Wavelength of bin center (1)
16- 21 F6.3 % q [-5.62/7.23] q Stokes parameter q=Q/I
23- 31 E9.3 % e_q [0.069/6.4] Uncertainty in q
33- 38 F6.3 % u [-5.12/7.9] u Stokes parameter u=U/I
40- 48 E9.3 % e_u [0.069/7.4] Uncertainty in u
50- 53 F4.2 % p [0/7.85] Polarization amplitude,
corrected for positive bias
55- 62 E8.2 % e_p [0.069/6.4] Uncertainty in p
64- 68 F5.1 deg PA [0/175.2]? Polarization Angle (θ);
east of north (G1)
70- 77 E8.2 deg e_PA [0.3/21.2]? Uncertainty in PA
(σθ) (G1)
79- 86 E8.2 --- chi2 [0/86] Reduced chi-squared of polarization
fit (2)
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Note (1): Data at wavelengths 0.550, 0.650, and 0.800 micron are
binned centered at those wavelengths with full-widths of
0.100, 0.100, and 0.150 micron, respectively; we refer to
these as the V-, R-, and I-like broadband filters. Data at
1.630 micron are H-band data. All other wavelength points
are binned with widths of 0.050 micron.
Note (2): chi2 values are not reported for H-band data.
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Byte-by-byte Description of file: table9.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 8 A8 --- Name Star name
9 A1 --- --- [(]
10- 11 A2 --- n_Name Star name (1)
12 A1 --- --- [)]
14- 18 F5.3 um lambda [0.485/0.985] Wavelength of bin center (2)
20- 25 F6.3 % q [-2.94/2.71] q Stokes parameter q=Q/I
27- 35 E9.3 % e_q [0.079/0.72] Uncertainty in q
37- 41 F5.3 % u [2.75/5.81] u Stokes parameter u=U/I
43- 51 E9.3 % e_u [0.079/0.72] Uncertainty in u
53- 56 F4.2 % p [2.86/6.36] Polarization amplitude,
corrected for positive bias
58- 65 E8.2 % e_p [0.079/0.71] Uncertainty in p
67- 70 F4.1 deg PA [32/65.5] Polarization Angle (θ);
east of north
72- 79 E8.2 deg e_PA [0.38/3.8] Uncertainty in PA (σθ)
81- 88 E8.2 --- chi2 [0.033/12] Reduced chi-squared of polarization fit
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Note (1): Data for HD204827 is given for three separate nights of
observations: n2, n3, and n4
Note (2): Data at wavelengths 0.550, 0.650, and 0.800 micron are binned centered
at those wavelengths with full-widths of 0.100, 0.100, and 0.150
micron, respectively; we refer to these as the V, R, and I
broadband filters. All other wavelength points are binned
with widths of 0.050 micron.
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Global notes:
Note (G1): All angles are measured east of north. No values are reported for
θ and σθ for cases in which the corrected
polarization is set to zero.
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History:
From electronic version of the journal
(End) Prepared by [AAS], Emmanuelle Perret [CDS] 28-Jul-2022