gabriele surcis 69 th international symposium on molecular spectroscopyg. surcis, monday, june 16...

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)

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


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)


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


non-paramagnetic

non-paramagnetic

paramagnetic

Pl

(%)PV

(%)

<20 <1

<12 <1

<100 <100

Maser Theory

Microwave Amplification by Stimulated Emission of Radiation

non-equilibrium state of a gas

efficient pump mechanism


Population inversion

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


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


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


θ

B

maser (l.o.s.)

ΦB lin. pol. vector

ΦB = 0°

ΦB = 90°Goldreich, P et al. 1973, ApJ, 179, 111

Maser Theory


∆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


g = Landé g-factor

Zeeman-splitting coefficient

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


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



FT IR spectrometer

Magnet facility(Bmax=30 Tesla)

CH3OH supply

He cooled bolometer

vacuum FIR beam

Dr. Hans Engelkamp (HFML)



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



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


CH3OH MASER RESULTS


CH3OH maser results

Surcis, G. et al. 2009, 2011, 2012, 2013


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

unsaturated masers

Surcis, G. et al. 2013, A&A, 556, 73

Pl > 4.5%

UNSATURATED

SATURATED


CH3OH maser results: first statistical results

H2O MASER RESULTS


H2O maser results: W75N(B)

Surcis, G. et al. 2011, A&A, 527, A48


Surcis, G.et al. 2014, A&A, 565L, 8



𝜱𝑩 ,𝟐𝟎𝟎𝟓❑ =+𝟕𝟎°±𝟗° 𝜱𝑩 ,𝟐𝟎𝟏𝟐

❑ =+𝟒𝟗°±𝟏𝟓°VLA1A



Surcis, G.et al. 2014, A&A, 565L, 8

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


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)

THANK YOU


EXTRA SLIDES


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


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


EXSTRA SLIDES

Surcis, G. et al. 2013, A&A, 556, 73


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°


EXTRA SLIDES


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


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


gabriele surcis 69 th international symposium on molecular spectroscopyg. surcis, monday, june 16...

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