Extragalactic Magnetism with SOFIA (SALSA Legacy Program). V. First Results on the Magnetic Field Orientation of Galaxies

Medientyp: E-Artikel
Titel: Extragalactic Magnetism with SOFIA (SALSA Legacy Program). V. First Results on the Magnetic Field Orientation of Galaxies
Beteiligte: Borlaff, Alejandro S.; Lopez-Rodriguez, Enrique; Beck, Rainer; Clark, Susan E.; Ntormousi, Evangelia; Tassis, Konstantinos; Martin-Alvarez, Sergio; Tahani, Mehrnoosh; Dale, Daniel A.; del Moral-Castro, Ignacio; Roman-Duval, Julia; Marcum, Pamela M.; Beckman, John E.; Subramanian, Kandaswamy; Eftekharzadeh, Sarah; Proudfit, Leslie
Erschienen: American Astronomical Society, 2023
Erschienen in: The Astrophysical Journal
Sprache: Nicht zu entscheiden
DOI: 10.3847/1538-4357/acd934
ISSN: 0004-637X; 1538-4357
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Beschreibung: <jats:title>Abstract</jats:title> <jats:p>We present the analysis of the magnetic field (<jats:italic>B</jats:italic>-field) structure of galaxies measured with far-infrared (FIR) and radio (3 and 6 cm) polarimetric observations. We use the first data release of the Survey of extragALactic magnetiSm with SOFIA of 14 nearby (<jats:inline-formula> <jats:tex-math> <?CDATA $\lt 20$?> </jats:tex-math> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mo><</mml:mo> <mml:mn>20</mml:mn> </mml:math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjacd934ieqn1.gif" xlink:type="simple" /> </jats:inline-formula> Mpc) galaxies with resolved (<jats:inline-formula> <jats:tex-math> <?CDATA $5^{\prime\prime} \mbox{--}18^{\prime\prime} ;$?> </jats:tex-math> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mn>5</mml:mn> <mml:mo accent="false">″</mml:mo> <mml:mo>–</mml:mo> <mml:mn>18</mml:mn> <mml:mo accent="false">″</mml:mo> <mml:mo>;</mml:mo> </mml:math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjacd934ieqn2.gif" xlink:type="simple" /> </jats:inline-formula> 90 pc–1 kpc) imaging polarimetric observations using SOFIA/HAWC+ from 53 to 214 <jats:italic>μ</jats:italic>m. We compute the magnetic pitch-angle (<jats:inline-formula> <jats:tex-math> <?CDATA ${{\rm{\Psi }}}_{B}$?> </jats:tex-math> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:msub> <mml:mrow> <mml:mi mathvariant="normal">Ψ</mml:mi> </mml:mrow> <mml:mrow> <mml:mi>B</mml:mi> </mml:mrow> </mml:msub> </mml:math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjacd934ieqn3.gif" xlink:type="simple" /> </jats:inline-formula>) profiles as a function of the galactocentric radius. We introduce a new magnetic alignment parameter (<jats:italic>ζ</jats:italic>) to estimate the disordered-to-ordered ratio of spiral <jats:italic>B</jats:italic>-fields. We find FIR and radio wavelengths to not generally trace the same <jats:italic>B</jats:italic>-field morphology in galaxies. The <jats:inline-formula> <jats:tex-math> <?CDATA ${{\rm{\Psi }}}_{B}$?> </jats:tex-math> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:msub> <mml:mrow> <mml:mi mathvariant="normal">Ψ</mml:mi> </mml:mrow> <mml:mrow> <mml:mi>B</mml:mi> </mml:mrow> </mml:msub> </mml:math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjacd934ieqn4.gif" xlink:type="simple" /> </jats:inline-formula> profiles tend to be more ordered across all galactocentric radii in radio (<jats:inline-formula> <jats:tex-math> <?CDATA ${\zeta }_{6\mathrm{cm}}\,=\,0.93\pm 0.03$?> </jats:tex-math> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:msub> <mml:mrow> <mml:mi>ζ</mml:mi> </mml:mrow> <mml:mrow> <mml:mn>6</mml:mn> <mml:mi>cm</mml:mi> </mml:mrow> </mml:msub> <mml:mspace width="0.25em" /> <mml:mo>=</mml:mo> <mml:mspace width="0.25em" /> <mml:mn>0.93</mml:mn> <mml:mo>±</mml:mo> <mml:mn>0.03</mml:mn> </mml:math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjacd934ieqn5.gif" xlink:type="simple" /> </jats:inline-formula>) than in FIR (<jats:inline-formula> <jats:tex-math> <?CDATA ${\zeta }_{154\mu {\rm{m}}}=0.84\pm 0.14$?> </jats:tex-math> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:msub> <mml:mrow> <mml:mi>ζ</mml:mi> </mml:mrow> <mml:mrow> <mml:mn>154</mml:mn> <mml:mi>μ</mml:mi> <mml:mi mathvariant="normal">m</mml:mi> </mml:mrow> </mml:msub> <mml:mo>=</mml:mo> <mml:mn>0.84</mml:mn> <mml:mo>±</mml:mo> <mml:mn>0.14</mml:mn> </mml:math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjacd934ieqn6.gif" xlink:type="simple" /> </jats:inline-formula>). For spiral galaxies, FIR <jats:italic>B</jats:italic>-fields are 2%–75% more turbulent than the radio <jats:italic>B</jats:italic>-fields. For starburst galaxies, we find that FIR polarization is a better tracer of the <jats:italic>B</jats:italic>-fields along the galactic outflows than radio polarization. Our results suggest that the <jats:italic>B</jats:italic>-fields associated with dense, dusty, turbulent star-forming regions (those traced at FIR) are less ordered than warmer, less dense regions (those traced at radio) of the interstellar medium. The FIR <jats:italic>B</jats:italic>-fields seem to be more sensitive to the activity of the star-forming regions and molecular clouds within a vertical height of a few hundred parsecs in the disk of spiral galaxies than the radio <jats:italic>B</jats:italic>-fields.</jats:p>
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