Variability Of Methanol And OH Masers Associated With

The Star-Forming Region G339.62-0.12

S t u d e n t : M a v i s S e i d u S u p e r v i s o r s : P r o f . D J v a n d e r Wa l t

D r S h a r m i l a G o e d h a r t

• Introduction

• Observational Methods

1. Single dish

2. Inteferometer

• Results and Discussions

• Summary

• Recommendations

• References

L AY O U T

• Star formation

A. The earliest stages of a star’s life is an intriguing mystery

• Massive star formation contribute greatly to the evolution of most galaxies

1. produce ultraviolet radiation

2. enrich the ISM through their supernova actions

• Formed in dynamic regions such as giant molecular clouds (site for star birth)

I N T R O D U C T I O N

image credit: Shubham Singh (Prince)

• Masers are found to be associated with the early stages of massive stars

deBuizer (2000), Foster and Caswell(1989)

• Masers are known to form in

1.stellar regions; mostly in high-mass star forming regions (Caswell,1998)

• They are used to probe through obscured regions

• The maser spot distribution suggests the structure and conditions of the regions where they are formed.

I N T R O D U C T I O N

Figure 1. Interstellar cloud

• Examples of masers: Methanol and OH masers

• The methanol and OH masers are known to be located in either

1. in the disk

2. or outside the HII region

I N T R O D U C T I O N

Outflows

Disk

Masers

Masers

Figure 2. Proposed location of some masers in star forming regions

I N T R O D U C T I O N• Evidence of variability in specific

star forming regions from observational results. The origin of maser variability have been

• The underlying mechanism of the variability was unclear

• Proposed investigation of variability of OH masers

Figure 3. Variability of the 6.7 GHz methanol masers over 10 years monitoring

Goedhart et al., (2014)

Goedhart et al., (2014)

Goedhart et al., (2014), Maswanganye et al., (2015), Szymczak et al., Araya et al.,

O B S E R VAT I O N A L M E T H O D S

Feeds

Primary reflector

Sub-reflector

Propagation of radio waves from source

Radio source

Declination axis

Euatorial mount

Focus Polarization

• Pointing correction using drift-scan observations

• Virgo A

−40 −30

0

2

4

TA(K

)

North

−40 −30V lsr (km/s)

0

2

4

East

−40 −30

0

2

4

6

8Centre

−40 −30

0

2

4West

−40 −30

0

2

4

South

Pointing observations for 2013d170

1 . S I N G L E D I S H O B S E R VAT I O N

2 . I N T E R F E R O M E T R I C M E T H O D U S I N G K AT- 7

O B S E R VAT I O N A L M E T H O D S

• Maser imaging

• Flux calibration

• Bandpass and gain calibration

• Image model

16 : 39 : 0042 : 0045 : 0048 : 0051 : 00RA (J2000)

30 : 00

−46 : 00 : 00

30 : 00

−45 : 00 : 00

−44 : 30 : 00

Dec

(J2000)

G339.62-0.12

G338.681-00.084

G338.88-00.08

G339.88-1.259

G340.054.0244

G339.925+0.557

G339.282+00.13

0.5

1.0

1.5

2.02.53.0

Fluxdensity(Jy/beam)

R E S U LT S A N D D I S C U S S I O N S

• Other maser fields were found closer to the G339.62-0.12 region

Figure 4. Continuum image of the star-forming region

16:45:5516:4616:46:0516:46:1016:46:1516:46:2016:46:2516:46:3016:46:3546:40 16:45:50 16:45:45 16:45:40 16:45:35 16:45:30 16:45:25 16:45:20

-45:37

-45:36

-45:38

-45:39

-45:40

-45:41

RGB img~1

1’ 14.59’ x 6.377’

N

EPowered by Aladin

denseCoredenseCore

Powered by Aladin

Figure 5. OH maser sources in the field of view

R E S U LT S A N D D I S C U S S I O N S1667 MHz 1665 MHz

R E S U LT S A N D D I S C U S S I O N S

• Each maser spectrum is unique

• Spectra spread over few km/s range (~10 km/s max)

Figure 6. Spectra of the G339.62-0.12 maser sources

0

20

40

60

80

100

120

6.7 GHz methanol

J

I

H

G

F

E

D

CB

A

Upper envelope

Lower envelope

Averaged spectra

0

10

20

30

40

50

60

70

Fluxdensity

(Jy)

1665 MHz OHE

DC

B

A

−40 −38 −36 −34 −32 −30 −28Vlsr (km s−1)

0

5

10

15

A

B

C

1667 MHz OH

• Investigating Variability

T I M E S E R I E S

Figure 7. Time series plots of G339.62-0.12 at the 6.7 GHz maser transition

10

20

-37.27 km s−1

10

20-36.96 km s−1

15

30-36.21 km s−1

25

50

Fluxdensity

(Jy)

-36.04 km s−1

50

75-35.64 km s−1

56400 56600 56800 57000 57200 57400

MJD

0

15-33.71 km s−1

20

40

-33.53 km s−1

20

40-33.49 km s−1

25

50

-33.36 km s−1

60

90

Fluxdensity

(Jy)

-32.96 km s−1

20

40-32.04 km s−1

56400 56600 56800 57000 57200 57400

MJD

15

30-30.5 km s−1

3.0

4.5-36.92 km s−1

9

12

-36.51 km s−1

12

16

Fluxdensity

(Jy)

-36.44 km s−1

4.5

6.0

7.5

-36.24 km s−1

56400 56600 56800 57000 57200

MJD(days)

0.8

1.6 -30.96 km s−1

Figure 8. OH maser time series for peak velocity channels in G339.62-0.12

40

50-37.49 km s−1

12

16 -37.01 km s−1

10

15

Fluxdensity

(Jy)

-36.67 km s−1

10.5

12.0-33.51 km s−1

56400 56600 56800 57000 57200

MJD

4

6 -31.79 km s−1

1667 MHz OH1665 MHz OH

T I M E S E R I E S• Different light curves for the OH maser at 1665 and 1667 MHz transitions

• Time series for each maser, their periodogram and periodicity

−1 0 1 2Phase(rad)

0

20

FluxDensity

(Jy) Period = 206 ± 2 days

6.7 GHz CH3OH

-36.08 km s−1

−1 0 1 2Phase(rad)

−5.0

−2.5

0.0

2.5

5.0 Period = 209 ± 2 days

1665 MHz OH-37.01 km s−1

−1 0 1 2Phase(rad)

−4

−2

0

2

4Period = 214 ± 2 days

1667 MHz OH-36.44 km s−1

20

40

606.7 GHz CH3OH -36.08 km s−1

10

15

20

FluxDensity

(Jy) 1665 MHz OH

-37.01 km s−1

56400 56600 56800 57000 57200MJD

10

151667 MHz OH

-36.44 km s−1

0.0

0.2

0.4

0.6

6.7 CH3OH Period = 206 ± 2 days-36.08 km s−1

fit

0.0

0.2

0.4

Pow

er 1665 MHz OH Period = 209 ± 2 day

-37.01 km s−1

0.005 0.010 0.015 0.020 0.025 0.030 0.035 0.040Frequency (day−1)

0.00

0.25

0.50 1667 MHz OH Period = 214 ± 2 days-36.44 km s−1

P E R I O D I C I T Y

40

60

80

6.7 GHz CH3OH-35.73 km s−1

7.5

10.0

12.5

FluxDensity

(Jy)

1665 MHz OH

-36.53 km s−1

56400 56600 56800 57000 57200MJD

5

6

7

1667 MHz OH

-36.24 km s−1

−1 0 1 2Phase(rad)

−20

0

20

Magnitude

Period = 208 ± 2 days

6.7 GHz CH3OH-35.73 km s−1

−1 0 1 2Phase(rad)

−2

0

2Period = 210 ± 1 day

1665 MHz OH-36.53 km s−1

−1 0 1 2Phase

−1

0

1

Magnitude

Period = 214.96 days

-36.24 km s−1

−1 0 1 2−5

0

5

10

P E R I O D I C I T Y

I N V E S T I G AT I N G P E R I O D I C I T Y

Parfenov & Sobolev (2014) Sing and Deshpande (2012) van Der Walt et al., (2016)

Observer’s position

1.9 AU

Gap RegionDisk

Disk

Disk

Disk

Secondary

Primary

Trailing "shock"

θ

−1 0 1 2Phase(rad)

0

20

FluxDensity

(Jy) Period = 206 ± 2 days

6.7 GHz CH3OH

-36.08 km s−1

• Simple geometric model by Parfenov & Sobolev to investigate the maser periodicity

• The similarity is quite striking

−1 0 1 2Phase(rad)

−4

−2

0

2

4Period = 214 ± 2 days

1667 MHz OH-36.44 km s−1

0.00.51.01.52.02.53.03.54.04.5

0 50 100 150 200

Flu

x

Time (days)

• All the investigated masers are highly variable

• Associated with some sort of periodicity (~ 205 to 215 ± 2 days)

• G339.62-0.12 star forming region is complex

1. The cause of the variability and periodicity is still being investigated

S U M M A RY

• High sensitive maser observations in G339.62-0.12 are needed

1. OH maser spot map

R E C O M M E N D AT I O N S

denseCoreOH/IRDkNeb

339.625339.64583339.66667339.6875339.70833339.72917339.75

-00.16667

-00.1

-00.08333

339.60417 339.58333 339.5625 339.54167

-00.11667

-00.13333

-00.15

SPITZER MIPS1

1’ 13.85’ x 6.151’

N

EPowered by Aladin

A C K N O W L E D G E M E N T

R E F E R E N C E S1. Caswell, J. L., 1998, Positions of hydroxyl masers at 1665

and 1667 MHz, MNRAS, 297, 215-235(1998)

2. Forster, J. R., and Caswell, J. L., 1989, A&A, 213, 339-350(1989)

3. Goedhart, S., Maswanganye, J. P., Gaylard, M. J., van der Walt, D. J., 2014, Periodicity in Class II methanol masers in high-mass star-forming regions, MNRAS 437,1808–1820(2014).

4. Parfenov, S.Y., Sobolev, A.M., 2014, MNRAS, 444,620(2014)

5. van der Walt, D.J., Maswanganye, J. P., Etoka, S., Goedhart, S., van der Heever, S.P., 2016,Periodic Methanol masers in G9.62+0.20E, A&A (2016)