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J/ApJ/836/199      IRDC G028.23-00.19 NIR polarimetry analysis      (Hoq+, 2017)

Tracing the magnetic field of IRDC G028.23-00.19 using NIR polarimetry. Hoq S., Clemens D.P., Guzman A.E., Cashman L.R. <Astrophys. J., 836, 199-199 (2017)> =2017ApJ...836..199H (SIMBAD/NED BibCode)
ADC_Keywords: Polarization ; Photometry, infrared ; Velocity dispersion ; Magnetic fields ; Molecular clouds Keywords: dust, extinction; ISM: clouds; ISM: individual objects: SNR G028.23-00.19 ; ISM: magnetic fields; stars: formation; techniques: polarimetric Abstract: The importance of the magnetic (B) field in the formation of infrared dark clouds (IRDCs) and massive stars is an ongoing topic of investigation. We studied the plane-of-sky B field for one IRDC, G028.23-00.19, to understand the interaction between the field and the cloud. We used near-IR background starlight polarimetry to probe the B field and performed several observational tests to assess the field importance. The polarimetric data, taken with the Mimir instrument, consisted of H-band and K-band observations, totaling 17160 stellar measurements. We traced the plane-of-sky B-field morphology with respect to the sky-projected cloud elongation. We also found the relationship between the estimated B-field strength and gas volume density, and we computed estimates of the normalized mass-to-magnetic flux ratio. The B-field orientation with respect to the cloud did not show a preferred alignment, but it did exhibit a large-scale pattern. The plane-of-sky B-field strengths ranged from 10 to 165µG, and the B-field strength dependence on density followed a power law with an index consistent with 2/3. The mass-to-magnetic flux ratio also increased as a function of density. The relative orientations and relationship between the B field and density imply that the B field was not dynamically important in the formation of the IRDC. The increase in mass-to-flux ratio as a function of density, though, indicates a dynamically important B field. Therefore, it is unclear whether the B field influenced the formation of G28.23. However, it is likely that the presence of the IRDC changed the local B-field morphology. Description: NIR polarimetric observations in both the H band (1.6um) and K band (2.2um) of G28.23-00.19 were obtained using the Mimir instrument on the 1.8m Perkins Telescope in Flagstaff, AZ. The H-band data were taken from Data Release 2 of the Galactic Plane Infrared Polarization Survey (GPIPS, Clemens+ 2012ApJS..200...19C). Targeted K-band observations were obtained over five nights in 2013 September and 2014 June. In addition to NIR polarimetry, we used NIR and mid-IR (MIR) photometry from the 2MASS (Skrutskie+ 2006, VII/233), UKIRT Infrared Deep Sky Survey (UKIDSS; see II/319), and GLIMPSE (see II/293) catalogs, dust continuum data from the Herschel infrared Galactic Plane Survey (Hi-GAL) (Molinari+ 2010PASP..122..314M) and the APEX Telescope Large Area Survey of the Galaxy (ATLASGAL) (Schuller+ 2009, see J/A+A/549/A45), and molecular line data from the 13CO Galactic Ring Survey (GRS; Jackson+ 2006ApJS..163..145J). File Summary:
FileName Lrecl Records Explanations
ReadMe 80 . This file table1.dat 148 17160 Stellar polarimetric properties of G28.23 field of view table2.dat 127 17160 Stellar photometric properties of G28.23 field of view table3.dat 68 121 Properties of the pixels in the B-field map
See also: II/226 : Stellar polarization catalogs agglomeration (Heiles, 2000) VII/233 : The 2MASS Extended sources (IPAC/UMass, 2003-2006) II/293 : GLIMPSE Source Catalog (I + II + 3D) (IPAC 2008) II/319 : UKIDSS-DR9 LAS, GCS and DXS Surveys (Lawrence+ 2012) J/ApJ/641/389 : Millimetric observations of IRDC cores (Rathborne+, 2006) J/ApJS/186/406 : 350um polarimetry from CSO (Dotson+, 2010) J/ApJ/723/1019 : Galactic SFR and gas surface densities (Heiderman+, 2010) J/ApJ/741/21 : Polarization of stars in Taurus (Chapman+, 2011) J/ApJ/756/60 : A 3mm line survey in 37 IR dark clouds (Sanhueza+, 2012) J/MNRAS/424/2442 : Catalog of bubbles from Milky Way Project (Simpson+, 2012) J/A+A/549/A45 : ATLASGAL Compact Source Catalog: 330<l<21 (Contreras+, 2013) J/ApJ/793/126 : L204 - Cloud 3 polarimetry and photometry (Cashman+, 2014) J/ApJS/213/13 : 1.3mm polarization maps of star-forming cores (Hull+, 2014) J/ApJ/815/130 : High-mass molecular clumps from MALT90 (Guzman+, 2015) : GPIPS data releases Byte-by-byte Description of file: table1.dat
Bytes Format Units Label Explanations
1- 5 I5 --- Seq Polarimetric Catalog Star Number 7- 13 F7.4 deg GLON Galactic Longitude 15- 21 F7.4 deg GLAT Galactic latitude 23- 24 A2 --- fPos Band Match (1) 26- 32 F7.2 % Pk ?=9999 K-band Polarization Percent 34- 40 F7.2 % e_Pk ?=9999 Uncertainty in Pk 42- 47 F6.1 deg GPAk [63/243]?=9999 K-band Galactic Polarization Position Angle 49- 54 F6.1 deg e_GPAk [1/178]?=9999 Uncertainty in GPAk 56- 62 F7.2 % Qk [-83/91]?=9999 K-band Stokes Q parameter 64- 70 F7.2 % e_Qk [0/100]?=9999 Uncertainty in Qk 72- 78 F7.2 % Uk [-96/96]?=9999 K-band Stokes U parameter 80- 86 F7.2 % e_Uk ?=9999 Uncertainty in Uk 88- 94 F7.2 % Ph ?=9999 H-band Polarization Percent 96-102 F7.2 % e_Ph ?=9999 Uncertainty in Ph 104-109 F6.1 deg GPAh [62/243]?=9999 H-band Galactic Polarization Position Angle 111-116 F6.1 deg e_GPAh [0.8/179]?=9999 Uncertainty in GPAh 118-124 F7.2 % Qh [-100/100]?=9999 H-band Stokes Q parameter 126-132 F7.2 % e_Qh ?=9999 Uncertainty in Qh 134-140 F7.2 % Uh [-100/94]?=9999 H-band Stokes U parameter 142-148 F7.2 % e_Uh ?=9999 Uncertainty in Uh
Note (1): Band Match as follows: H = Entry only in H-pol (12554 occurrences), K = Entry only in K-pol (1326 occurrences), HK = Entries in both H and K-pol (3280 occurrences).
Byte-by-byte Description of file: table2.dat
Bytes Format Units Label Explanations
1- 5 I5 --- Seq Polarimetric Catalog Star Number 7- 29 A23 --- AName NIR source cross-match designation (1) 31- 36 F6.3 mag Jmag [6.4/21.6]?=99.99 J-Band magnitude in NIR source catalog 38- 43 F6.3 mag e_Jmag [0.001/0.9]?=99.99 Uncertainty in Jmag 45- 50 F6.3 mag Hmag ?=99.99 H-Band magnitude in NIR source catalog 52- 56 F5.3 mag e_Hmag ?=99.99 Uncertainty in H-Band magnitude 58- 63 F6.3 mag Kmag [4.3/17.4]?=99.99 K-Band magnitude in NIR source catalog 65- 69 F5.3 mag e_Kmag [0.001/0.3]?=99.99 Uncertainty in Kmag 71- 76 F6.3 mag [4.5]mag [6.5/14.6]?=99.99 GLIMPSE IRAC 4.5um magnitude 78- 83 F6.3 mag e_[4.5]mag [0.02/0.4]?=99.99 Uncertainty in [4.5]mag 85- 90 F6.3 mag (H-K) ?=99.99 H-K color index 92- 96 F5.3 mag e_(H-K) ?=99.99 Uncertainty in (H-K) 98-103 F6.3 mag (H-4.5) ?=99.99 H-4.5 color index 105-110 F6.3 mag e_(H-4.5) ?=99.99 Uncertainty in (H-4.5) 112-115 F4.1 mag Av [0/75] Extinction in V-Band 117-119 F3.1 mag e_Av [0/5] Uncertainty in V-Band Extinction 121-125 A5 --- Meth Color excess extinction method ("H-K": 4843 occurrences, or "H-4.5") 127 A1 --- RD Relative Distance classification (2)
Note (1): NIR Designation from either 2MASS (JHHMMSSss+DDMMSSs) or UKIDSS Galactic Plane Survey (UGPS) DR8 Catalogs. The UGPS identifiers are given using the unique "sourceID" for that catalog. Note (2): Relative locations of stars with respect to the cloud along the line of sight. Code as follows: B = Background Star (10597 occurrences); F = Foreground Star (6255 occurrences); U = Unknown (308 occurrences).
Byte-by-byte Description of file: table3.dat
Bytes Format Units Label Explanations
1- 7 F7.4 deg GLON Galactic Longitude of Pixel 9- 15 F7.4 deg GLAT Galactic Latitude of Pixel 17- 20 F4.1 deg PA [8/38]? Position Angle Dispersion 22- 25 F4.1 deg e_PA [1/18]? Uncertainty in PA 27- 30 I4 cm-3 n(H2) [0/1192]? Volume Density, H2 / cm3 32- 34 I3 cm-3 e_n(H2) [0/238]? Uncertainty in n(H2) 36- 39 F4.1 km/s sig(13CO) [1/15]? 13CO gas velocity dispersion 41- 44 F4.1 km/s e_sig(13CO) [0/19]? Uncertainty in sig(13CO) 46- 50 F5.1 10-10T BPOS [13/164]? plane-of-sky B-field strength, in microGauss units 52- 55 F4.1 10-10T e_BPOS [3/43]? Uncertainty in BPOS 57- 60 F4.2 --- Mphip [0.09/7.6]? normalized Mass-to-Flux ratio 62- 65 F4.2 --- e_Mphip [0.03/2]? Uncertainty in Mphip 67- 68 A2 --- Lim Limits (1)
Note (1): Indicates whether the PA dispersion (PA) or density (n) used to calculate BPOS limited the BPOS calculation as follows: PA = indicates the PA dispersion was greater than 25deg, but PA dispersion minus its uncertainty was less than or equal to 25deg. n = indicates that the volume density was less than 50∼H2/cm^3, but the density plus its uncertainty was greater than or equal to 50∼H2/cm^3.
History: From electronic version of the journal
(End) Prepared by [AAS], Emmanuelle Perret [CDS] 06-Oct-2017
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