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Astronomical masers: polarization properties of 22-GHz water and 6.7-GHz
methanol masersGabriele Surcis
69th International Symposium on Molecular SpectroscopyG. Surcis, Monday, June 16st, 2014
Collaborators: W.H.T. Vlemmings (Chalmers Uni, Sweden), H.J. van Langevelde (JIVE, Leiden Uni, The Netherlands), B. Hutawarakorn Kramer (MPIfR, Germany), J.M. Torrelles (CSIC, Spain), C. Goddi (JIVE, The Netherlands), S. Curiel (UNA, México), J. Cantó (UNAM, México), S.-W. Kim (KASSI, Rep. of Korea), J.-S. Kim (NAOJ, Japan), L. Moscadelli (INAF, Italy), L.H. Quiroga-Nuñez (Leiden Uni, The Netherlands)
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Outline
High-mass star formation
CH3OH maser results
measurements of the g-factor of CH3OH maser
Conclusions & Follow-ups
Maser Theorypolarization properties
H2O maser results
69th International Symposium on Molecular SpectroscopyG. Surcis, Monday, June 16st, 2014
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low & intermediate initial magnetic field intensities
(µ=20-120)
strong initial magnetic field intensities
(µ=5)
fast & collimated outflows
slow & poorly collimatedoutflows
MHD simulationsSeifried et al. 2012, MNRAS, 422, 347
After the formation of a Keplerian disk (µ=10.4)
High-mass star formation (HMSF)
69th International Symposium on Molecular SpectroscopyG. Surcis, Monday, June 16st, 2014
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H2O
CH3OH
OH
108 < nH2 < 1010
107 < nH2 < 109
nH2 < 108
Density(cm-3)
Frequency(GHz)
22
6.7
1.6/1.7
protostar
Masers are bright and have narrow spectral lines
High-mass star formation (HMSF)-masers
69th International Symposium on Molecular SpectroscopyG. Surcis, Monday, June 16st, 2014
non-paramagnetic
non-paramagnetic
paramagnetic
Pl
(%)PV
(%)
<20 <1
<12 <1
<100 <100
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Maser Theory
Microwave Amplification by Stimulated Emission of Radiation
non-equilibrium state of a gas
efficient pump mechanism
69th International Symposium on Molecular SpectroscopyG. Surcis, Monday, June 16st, 2014
Population inversion
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Unsaturated masers
Saturated masers
Intrinsic thermal linewidth (ΔVi)
ΔVi
Emerging brightness temperature (TbΔΩ)
TbΔΩ
Velocity
I/I0
Stimulated emission rate << Decay ratemaser grows exponentially
Stimulated emission rate >> Decay ratemaser grows linearly
Maser Theory
69th International Symposium on Molecular SpectroscopyG. Surcis, Monday, June 16st, 2014
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Full radiative transfer method (FRTM)
Zeeman splitting << spectral line breadth (H2O and CH3OH)
gΘ >> R ; gΘ >> Γ ; gΘ >> Γν
Landé g-factor
eB/mec
Rate of stimulated emission Decay
rate
Cross-relaxation between
the magnetic substates
Maser Theory
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Only for unsaturated masers.
Full radiative transfer method (FRTM)
U(ω) =0 Q(ω)=I┴-I||
TbΔΩ ΔVi+ Pl
θ
FRTM code
I POLI
observed spectra
Surcis, G. et al. 2011, A&A, 527, 48
Vlemmings, W.H.T. et al. 2006, A&A, 448, 597
Maser Theory
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θ
B
maser (l.o.s.)
ΦB lin. pol. vector
ΦB = 0°
ΦB = 90°Goldreich, P et al. 1973, ApJ, 179, 111
Maser Theory
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∆𝑉 𝑍=(104𝑔𝜇𝑁𝑀 𝐽 ) ∙𝐵¿∨¿ ¿
= magnetic quantum number for the rotational transition
= nuclear magneton
𝑀 𝐽
𝜇𝑁=𝑒ℏ2𝑚𝑛𝑐
𝜶𝒁
Maser Theory
ZEEMAN SPLITTING
ν0ν0-ΔνZ ν0+Δν
Z
σ + σ -π
69th International Symposium on Molecular SpectroscopyG. Surcis, Monday, June 16st, 2014
g = Landé g-factor
Zeeman-splitting coefficient
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TbΔΩ ΔViFRTM code + +
Zeeman splitting & Magnetic field strength
B||= B · cos θ
CH3OH maser
unkown g-factor
ΔVz
B||=
B||= B · cos θ
Surcis, G. et al. 2011, A&A, 527, 48
Vlemmings, W.H.T. et al. 2011, A&A, 529, 95
Maser Theory
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CH3OH masers: measurements of the g-factor
CH3OH g-factor is uncertain by at least an order of magnitudeJen 1951, Phys Rev, 81, 197 «preliminary study» for E-type CH3OH
Extrapolation indicates that for A+ CH3OH (maser transition) g-factor = 0.141
Resulting in α6.7GHz = 0.005 km s-1 G-1
51-60 A+
100mG fields results in 0.5 m/s effect, barely detectable (10 Hz at 6.7 GHz)equivalent to 0.0013 cm-1 at 30 T
New measurements are necessary
but could also be 0.01 cm-1
69th International Symposium on Molecular SpectroscopyG. Surcis, Monday, June 16st, 2014
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CH3OH masers: measurements of the g-factor
FT IR spectrometer
Magnet facility(Bmax=30 Tesla)
CH3OH supply
He cooled bolometer
vacuum FIR beam
Dr. Hans Engelkamp (HFML)
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CH3OH masers: measurements of the g-factor
Wave numbers [cm-
1]
Inte
nsi
ty
November 2013
0.6 THz 1.8 THz
Resolution = 0.03 cm-1 ≈ 0.001 THz
NO
SPLITTIN
G
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CH3OH masers: measurements of the g-factor
Experimentally
Theoretically
We are not in the linear regime
New design of the experiment. Maybe by building and using a lab CH3OH maser, which will be inserted into a different magnet facility.
From literature the Zeeman-splitting for B>2.6 Tesla isnot linear, the quadratic term is not negligible.
First theoretical values of the Landé g-factors for the CH3OH molecule have been just calculated by using the BELGI program (Lankhaar et al., in preparation).
2.6 T0
ΔVz
0
The value of the Zeeman-splitting coefficient αZ of the maser transition is a little bit smaller than expected (Vlemmings et al., in preparation).
Dr. Hans Engelkamp
Prof. Dr. Gerrit Groenenboom, Prof. Dr. Ir. Ad van der Avoird, Boy Lankhaar (MSc student)
Theoretical Chemistry group, Institute for Molecules and Materials
High Field Magnet Laboratory
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CH3OH MASER RESULTS
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CH3OH maser results
Surcis, G. et al. 2009, 2011, 2012, 2013
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CH3OH maser results: first statistical results
Magnetic field oriented along the large scale molecular outflows
Probability that the angles are drawn from random distribution
Surcis, G. et al. 2013, A&A, 556, 73
10%69th International Symposium on Molecular SpectroscopyG. Surcis, Monday, June 16st, 2014
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unsaturated masers
Surcis, G. et al. 2013, A&A, 556, 73
Pl > 4.5%
UNSATURATED
SATURATED
69th International Symposium on Molecular SpectroscopyG. Surcis, Monday, June 16st, 2014
CH3OH maser results: first statistical results
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H2O MASER RESULTS
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H2O maser results: W75N(B)
Surcis, G. et al. 2011, A&A, 527, A48
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Surcis, G.et al. 2014, A&A, 565L, 8
H2O maser results: W75N(B)
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𝜱𝑩 ,𝟐𝟎𝟎𝟓❑ =+𝟕𝟎°±𝟗° 𝜱𝑩 ,𝟐𝟎𝟏𝟐
❑ =+𝟒𝟗°±𝟏𝟓°VLA1A
H2O maser results: W75N(B)
69th International Symposium on Molecular SpectroscopyG. Surcis, Monday, June 16st, 2014
Surcis, G.et al. 2014, A&A, 565L, 8
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CONCLUSIONS
From CH3OH masers we found that the probability that magnetic fields arealigned with the large-scale outflows in massive YSO is significant The laboratory measurement of the Landé g-factor for the CH3OH molecule isextremely challenging Theoretical calculations are «easier», first values just determined
Consistency between magnetic field morphology from small to large scale
For the first time, we are able to observe in «real time» the collimation processof an early outflow in a very YSO and to measure the rotation of the magnetic field
69th International Symposium on Molecular SpectroscopyG. Surcis, Monday, June 16st, 2014
FOLLOW-UPSImproving the CH3OH masers statistics by observing more YSOs (28 sources = 10 published + 13 already observed + 5 scheduled) to have a probability <1%Monitoring project of the H2O masers in W75N(B) over 6 years (4 epochs spaced by 2 years) with the EVN in full polarization mode (1st epoch tomorrow)
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THANK YOU
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EXTRA SLIDES
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More MHD simulations
High-mass star formation (HMSF)
Prevent fragmentation
Reduce angular momentum
Influence the accretion rates
Determine size of HII regions (strong B = smaller)
µ>10 Keplerian disks are easily formed
µ<10 Keplerian disks are formed only if a turbulent velocity fieldis introduced in the simulations
Banerjee & Pudritz 2007; Peters et al. 2011; Hennebelle et al. 2011; Seifried et al. 2011, 2012b
Seifried et al. 2011, MNRAS, 417, 1054 Seifried et al. 2012b, MNRAS, 423, L40
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SCALED-UP VERSION OF LOW-MASS PROTOSTARS
Kelvin-Helmholtz timescale << dynamical time
Start to burn their nuclear fuels during the accretion
The flow of gas from a surrounding disk faces an obstacle in the form of theradiative pressure that such massive stars will produce as they are still formingIn order to avoid the halting of the infall it is necessary the formation of anearly outflow which is driven by the MF coupled to the protostellar disk. Banerjee & Pudritz 2007, ApJ, 660, 479
EXTRA SLIDES
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EXSTRA SLIDES
Surcis, G. et al. 2013, A&A, 556, 73
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EXTRA SLIDES
Foreground Faraday Rotation
Ф[°] = 4.22 x 106 D[kpc] ne[cm-3] B||[mG] ν-2[GHz]
where ne≈ 0.012 cm-3 B||≈2x 10-3 mG D=1.3 kpc
W75N
Фwater[°] ≈ 0.3° Фmeth[°] ≈ 3.0°
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EXTRA SLIDES
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IRAS20126+4104
D = 1.64 ± 0.5 kpc
= CH3OH maser
B0.5 with a mass 7 M ̴� sun
= H2O maser
Surcis, G. et al. 2014, A&A, 563, 30
EXTRA SLIDES
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We need at least a total of 28 sources to have a probability <1%
9 (+1) sources already published
13 already observed with the EVN
5 still to be observed with EVN
Magnetic field orientation
Outflows orientation
17 sources already published by several authors.
11 sources have been proposed to be observed with ALMA (13CO, C18O, SiO)
EXTRA SLIDES
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