J/ApJ/806/94 Optical polarimetric catalog of stars in the SMC (Gomes+, 2015)
A new optical polarization catalog for the Small Magellanic Cloud:
the magnetic field structure.
Gomes A.L., Magalhaes A.M., Pereyra A., Rodrigues C.V.
<Astrophys. J., 806, 94 (2015)>
=2015ApJ...806...94G 2015ApJ...806...94G (SIMBAD/NED BibCode)
ADC_Keywords: Magellanic Clouds ; Polarization ; Photometry, UBV
Keywords: galaxies: ISM; Magellanic Clouds; magnetic fields;
techniques: polarimetric
Abstract:
We present a new optical polarimetric catalog for the Small Magellanic
Cloud (SMC). It contains a total of 7207 stars, located in the
northeast (NE) and Wing sections of the SMC and part of the Magellanic
Bridge. This new catalog is a significant improvement compared to
previous polarimetric catalogs for the SMC. We used it to study the
sky-projected interstellar magnetic field structure of the SMC. Three
trends were observed for the ordered magnetic field direction at
position angles (PAs) of (65°±10°), (115°±10°),
and (150°±10°). Our results suggest the existence of an
ordered magnetic field aligned with the Magellanic Bridge direction
and SMC's Bar in the NE region, which have PAs roughly at 115.4°
and 45°, respectively. However, the overall magnetic field
structure is fairly complex. The trends at 115° and 150° may
be correlated with the SMC's bimodal structure, observed in Cepheids'
distances and HI velocities. We derived a value of
Bsky=(0.497±0.079)µG for the ordered sky-projected magnetic
field, and δB=(1.465±0.069)µG for the turbulent magnetic
field. This estimate of Bsky is significantly larger (by a factor of
∼10) than the line of sight field derived from Faraday rotation
observations, suggesting that most of the ordered field component is
on the plane of the sky. A turbulent magnetic field stronger than the
ordered field agrees with observed estimates for other irregular and
spiral galaxies. For the SMC the Bsky/δB ratio is closer to
what is observed for our Galaxy than other irregular dwarf galaxies.
Description:
The observational data were taken at Cerro Tololo Inter-American
Observatory (CTIO) over the course of five nights in 1992 November
13-17, applying the optical polarization technique and using the 1.5m
telescope.
File Summary:
--------------------------------------------------------------------------------
FileName Lrecl Records Explanations
--------------------------------------------------------------------------------
ReadMe 80 . This file
table7.dat 87 7207 Polarimetric catalog (observed polarization)
table8.dat 87 6486 Polarimetric catalog (intrinsic polarization)
--------------------------------------------------------------------------------
See also:
II/236 : UBVR CCD survey of the Magellanic clouds (Massey+, 2002)
II/226 : Stellar polarization catalogs agglomeration (Heiles, 2000)
J/MNRAS/442/1663 : Velocities of red giants in the SMC (Dobbie+, 2014)
J/ApJ/698/2031 : Polarimetry of HAeBe stars (Rodrigues+, 2009)
J/ApJ/688/1029 : Magnetic field in the SMC (Mao+, 2008)
J/A+AS/91/171 : Blue stars between Magellanic Clouds (Demers+ 1991)
J/A+AS/30/261 : UBV and Radial Velocities of SMC Supergiants (Ardeberg+, 1977)
Byte-by-byte Description of file: table7.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 4 I4 --- Seq Identification of field object
9 I1 h RAh Hour of Right Ascension (J2000)
11- 12 I2 min RAm Minute of Right Ascension (J2000)
14- 18 F5.2 s RAs Second of Right Ascension (J2000)
23 A1 --- DE- Sign of the Declination (J2000)
24- 25 I2 deg DEd Degree of Declination (J2000)
27- 28 I2 arcmin DEm Arcminute of Declination (J2000)
30- 34 F5.2 arcsec DEs Arcsecond of Declination (J2000)
39- 44 F6.4 % Pobs [0.027/5.2] Observed polarization
49- 54 F6.4 % e_Pobs [0.001/1.6] Error in Pobs
59- 64 F6.2 deg PAint Position angle of observed polarization
69- 76 F8.5 mag Vmag [9.6/20.7] The V band magnitude
81- 87 F7.5 mag e_Vmag [0.0004/0.3] Error in Vmag
--------------------------------------------------------------------------------
Byte-by-byte Description of file: table8.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 4 I4 --- Seq Identification of field object
9 I1 h RAh Hour of Right Ascension (J2000)
11- 12 I2 min RAm Minute of Right Ascension (J2000)
14- 18 F5.2 s RAs Second of Right Ascension (J2000)
23 A1 --- DE- Sign of the Declination (J2000)
24- 25 I2 deg DEd Degree of Declination (J2000)
27- 28 I2 arcmin DEm Arcminute of Declination (J2000)
30- 34 F5.2 arcsec DEs Arcsecond of Declination (J2000)
39- 44 F6.4 % Pint [0.05/5.5] Intrinsic polarization
49- 54 F6.4 % e_Pint [0.01/1.6] Error in Pint
59- 64 F6.2 deg PAint Position angle of intrinsic polarization
69- 76 F8.5 mag Vmag [14.2/20.7] The V band magnitude
81- 87 F7.5 mag e_Vmag [0.001/0.3] Error in Vmag
--------------------------------------------------------------------------------
History:
From electronic version of the journal
(End) Prepared by [AAS], Emmanuelle Perret [CDS] 12-Oct-2015