J/MNRAS/513/2039 Polarimetric study of LDN 1616 background stars (Saha+, 2022)
Magnetic fields and young stellar objects in cometary cloud L1616.
Saha P., Soam A., Baug T., Gopinathan M., Mondal S., Ghosh T.
<Mon. Not. R. Astron. Soc. 513, 2039-2056 (2022)>
=2022MNRAS.513.2039S 2022MNRAS.513.2039S (SIMBAD/NED BibCode)
ADC_Keywords: Milky Way ; Magnetic fields ; Molecular clouds ; YSOs ; Stars, O ;
Stars, B-type ; Interstellar medium ; Polarization ;
Positional data
Keywords: magnetic fields - techniques: polarimetric - proper motions -
stars: distances - stars: pre-main-sequence - ISM: clouds
Abstract:
The Lynds' Dark Nebula (LDN) 1615/1616 and CB 28 (hereafter L1616)
together form a cometary globule located at an angular distance of
about 8° west of the Orion OB1 association, aligned roughly along
the east-west direction, and showing a distinct head-tail structure.
The presence of massive stars in the Orion belt has been considered to
be responsible for the radiation-driven implosion mode of star
formation in L1616. Based on the latest Gaia Early Data Release 3
(EDR3) measurements of the previously known young stellar objects
(YSOs) associated with L1616, we find the distance to this cloud to be
384 ± 5 pc. We present optical polarimetry towards L1616 that maps
the plane-of-sky component of the ambient magnetic field (BPOS)
geometry. Based on the proper motion of the YSOs associated with
L1616, we investigate their plane-of-sky motion relative to the
exciting star ε Ori. Using the Gaia EDR3 measurements of the
distances and proper motions of the YSOs, we find two additional
sources comoving with the known YSOs. One comoving source is HD 33056,
a B9 star, and the other might be a young pre-main-sequence star not
reported in previous studies. The mean direction of BPOS is found to
follow the cloud structure. This could be the effect of dragging of
the magnetic field lines by the impact of the ionizing radiation from
ε Ori. Based on the pressure exerted on L1616, and the ages of
the associated YSOs, we show that it could possibly be the main source
of ionization in L1616, and thus the star formation in it.
Description:
In this paper, we attempt to identify the triggering source based on
the dynamical study of the YSOs using the recent Gaia Early Data
Release 3 (EDR3, Gaia Collaboration 2021A&A...649A...1G 2021A&A...649A...1G, Cat. I/350)
measurements. We perform optical polarization observations of this
region to understand the morphology of BPOS. We also compare our
results with the Planck polarization measurements (Planck
Collaboration 2016A&A...594A...1P 2016A&A...594A...1P) towards this cloud. Based on the
Gaia EDR3 data, we make an attempt to find the possible acceleration
of the associated YSOs with respect to the ionizing source on the
plane-of-sky. Based on the magnetic field geometry of L1616 and the
relative proper motion of the YSOs, we investigate the possible
radiation-driven implosion (RDI) towards this cloud. We additionally
find several sources that share similar distances and proper motions
as the previously known YSOs, (i.e see section Introduction).
For the observational data (i.e see section 2.1) the optical
polarimetric observations have been carried out using the Aries
IMaging POLarimeter (AIMPOL; Rautela et al. 2004BASI...32..159R 2004BASI...32..159R)
mounted as a back-end instrument at the f/13 Cassegrain focus of the
104-cm Sampurnanand Telescope, located at Aryabhatta Research
Institute of Observational Sciences (ARIES), Nainital,
India. Descriptions of the instrument and the methods of the
polarization measurements are provided in detail in Rautela et al.
(2004BASI...32..159R 2004BASI...32..159R). The polarimetric data reduction steps and the
procedures adopted to estimate the polarization fraction (P) and
position angle (θ) of the observed stars are discussed in
several previous studies (e.g. Eswaraiah et al. 2011MNRAS.411.1418E 2011MNRAS.411.1418E;
Soam et al. 2013MNRAS.432.1502S 2013MNRAS.432.1502S; Saha et al. 2021A&A...655A..76S 2021A&A...655A..76S,
Cat. J/A+A/655/A76). The observations have been carried out using the Rc
photometric band.
As explained in the section 3.2 Foreground polarization correction,
the BPOS on the boundaries of dense molecular clouds can be traced
using linear polarization measurements of the background stars. We use
the threshold of P/ΔP => 2 in the analysis of R-band
polarimetric data which extracts 195 stars, which are located
background of the L1616 cloud complex. The distances of the observed
stars are obtained from Bailer-Jones et al. (2021AJ....161..147B 2021AJ....161..147B,
Cat. I/352). We relax our initial selection criteria of d/Δd => 3
and RUWE ≤ 1.4 on these 195 sources as here our primary investigation
is focused only on the polarimetric measurements. Therefore, we use
polarimetric results of these 195 sources to trace the BPOS geometry
around L1616. Results in tablea2.dat presents our foreground-corrected
optical polarimetric data.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
tablea2.dat 38 195 Foreground-corrected optical polarimetric
results of 195 stars located at the background
of LDN 1616
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See also:
I/350 : Gaia EDR3 (Gaia Collaboration, 2020)
J/A+A/655/A76 : L1172/1174 R-band polarimetric results (Saha+, 2021)
I/352 : Distances to 1.47 billion stars in Gaia EDR3
(Bailer-Jones+, 2021)
J/A+A/594/A116 : HI4PI spectra and column density maps (HI4PI team+, 2016)
II/246 : 2MASS All-Sky Catalog of Point Sources (Cutri+ 2003)
II/349 : The Pan-STARRS release 1 (PS1) Survey - DR1 (Chambers+, 2016)
Byte-by-byte Description of file: tablea2.dat
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Bytes Format Units Label Explanations
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1- 3 I3 --- ID Identifier number (Star_ID)
5- 13 F9.6 deg RAdeg Barycentric right ascension of the source (ICRS)
at Ep=2016.0 (RA)
15- 23 F9.6 deg DEdeg Barycentric declination of the source (ICRS) at
Ep=2016.0 (Dec.)
25- 27 F3.1 % P Polarization fraction (P)
29- 31 F3.1 % e_P Uncertainty in the measurement of P (ΔP)
33- 35 I3 deg PA Position angle of the polarization plane
37- 38 I2 deg e_PA Uncertainty in the measurement of PA (ΔPA)
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History:
From electronic version of the journal
(End) Luc Trabelsi [CDS] 16-Dec-2024