The Proper Motions of Water Masers at
22 GHz in W49N star-forming region
measured with KaVA
Asanok K., Tomoya, H., Kramer B.H.,
K., Sugiyama, Tie Liu, Kee-Tae Kim
EAVN meeting 201926 September 2019 @Ibaraki University, JapanOUTLINE OF TALK

1) Introduction and the objective of the study2) Methodology
3) Result and discussion4) Conclusion & Future works

What is W49 A?
Aquila constellation

Star-forming region W49 A[De Pree+1997]
W49 N: Welch ring (3.6 cm)

W49 A• Complex and luminous• Strong signal inwater maser

Supernovaremnant

Cometary shape:W49 S (3.6 cm)(Saral+2015; Spitzer IRAC band)

11.1 kpc [Zhang+2013]

W49 SW (3.6 cm)

W49

The possible causes & Literature reviews
1) Water maser emission from star-forming regions is known to show a strong
time variation and the most variations are ’outbursts’ by changing dramatic flux
for a few tens of days until to a few months.
2) The outburst mechanism is still puzzling!
3) The recent strong outburst of the W49N H2O maser was observed in 2003 withVERA (Honma+ 2004) and found to be located on the arc-like structure in thecentral maser concentration, implying its connection to shock phenomena
powered by the YSOs.
4) The burst events will be occured again ~2017, therefore, the good chance to reobserve by using the Effelsberg telescope (Kramer, B.H.) and KaVA (this work).

The objective of the study• To study the physical properties of water masers such as
the position offset, the radial and transverse velocities toward
W49N star-forming region• To study the proper motion of water masers by using KaVA data
• To study the flux variability by comparing the positions of watermasers with previous work (i.e. Effelsberg telescope =>Kramer, B.H.
in preparation)• To understand the environment of W49N region; morphology,flare

Methodology

Resolution at 22 GHz à 0.001-0.005 arcsec

https://www.nao.ac.jp/en/news/science/2012/20121003-vera.html

https://www.kasi.re.kr/eng/pageView/89

Total time requested: 40 hrs;
Number of hour each: 5 hrs ; Min/Max Separation: 1-3(calibrators)/20-40 days(target sources)
Epoch 1 (58.5D): Feb. 27-28, 2017 (1&2 session)
Epoch 2 (102.5D): Aprl. 12-13, 2017 (1&2 session)
Epoch 3 (130.5D): May 10-11, 2017 (1&2 session)

Results (1: spectra)
14000

Vlsr [-250:+250] km/s

KaVA, Effelsberg

25000

2017-03-10 (Effelsberg)
2017-02-27 (KaVA)
2017-02-28 (KaVA)

2017-04-08.dat (Effelsberg)
2017-04-12 (KaVA)
2017-04-13 (KaVA)

Epoch 112000

Epoch 2Flux Density (Jy)

10000
8000
6000
4000015000

10000

5000

2000

-200

-1000VLSR (km s-1)

1000200-200

25000

-100

2017-05-16.dat (Effelsberg)
2017-05-10 (KaVA)
2017-05-11 (KaVA)

100200Effelsberg:
Ep1 Mar. 10, 2017
Ep2 Aprl 8, 2017
Ep3 May 16, 2017

15000

10000

500000VLSR (km s-1)

Epoch 320000

Flux Density (Jy)

Flux Density (Jy)20000

-200-1000100-1

VLSR (km s )200

Results (2: distribution)

2Epoch II (103.5D): 320 features

5000-50

blueshift-2-200
210-1
RA offset [arcsec]

-2

250
00-50

-100-1-150-200-2-100-150(0.523,-0.155) mas @0.899 km/s

VLSR (km s-1)

1001001

Epoch III (130.5D): 277 features

-250
250
2200

10-1
RA offset [arcsec]-2150-2501001(1.948,-0.384) mas @0.674 km/s

50
00-50

VLSR (km s-1)

(0.687,-0.326) mas @0.847 km/s

Strongest flux

-1

DEC offset [arcsec]

150

VLSR (km s-1)

1redshift200

DEC offset [arcsec]

DEC offset [arcsec]

2200
150

250

Epoch I (58.5D): 870 features

250-100-1-150-200-2-250
2

10-1
RA offset [arcsec]-2-300Gone! disappear
Found in other channels(0.433,0.087) @1.314 km/s-300

Results (3.1: Comparison with Effelsberg observation)
350

6000

2017-05-16.dat (Effelsberg)
2017-05-10 and 11 (KaVA)
2017-04-08.dat (Effelsberg)
2017-04-12 and 13 (KaVA)
2017-03-10 (Effelsberg)
2017-02-27 8 (KaVA)

250

Peak Flux (Jy)5000

Flux Density (Jy)index 23300

>2.5 times

4000

200
150

Step 3analyze the flux
variability with ep1

10050

3000

1.5-2 times

050

60

70

80
Dates

90

2000
1000
0-100

Step 1-95-90-85
VLSR (km s-1)

Span and check in eachvelocity set-80-75

Step 2Check position

100110Results (3.2: Flux variability )Compare with the single dish spectra which obtained from Effelsberg telescope
99 features of water masers are counted as follow the Effelsberg telescope detection.
Flare ~ flux >=10 times of flux_ep1
Only 37 features are classified as the flux variability in this observation.
Flux Increasing (9 features)
100
An example
1600index 80
2
1400
50

800
600
400
200
050

60

70

80

90

100

110

120

130

1

Flare @ ~ -20 km/s

00-50

Flare @ ~ +65 km/s

VLSR (km s-1)

1000

DEC offset [mas]Peak Flux (Jy)

1200

-100-1

140Dates-150-2

Honma+2004 found ~30 km/s …burst!
210-1
RA offset [mas]-2-200Results (3.2 cont. : Flux variability )Flux Decreasing (28 features)Type A (linear)Type B (random: decrease+increase)
200

250
22200

1500-1500-50-1-100

100

150
00

arc-likestructure-1-50-150-2-200
2

10-1
RA offset [mas]-2-250VLSR (km s-1)

100

DEC offset [mas]1VLSR (km s )DEC offset [mas]150-100-2
2

10-1
RA offset [mas]-2-150Results (4: proper motion )-83.65-1638.3

Linear fitting => proper motion/year(ref. the strongest spot and the same VLSR)-1638.35-83.7-1638.4-83.75

Dec offset (mas)RA offset (mas)-1638.45-1638.5-1638.55-1638.6-83.8-83.85-1638.65-83.9-1638.75’W49N-features1.dat’ u 1:2:3f(x) = 0.00420x + -1638.85886
5060

70

80

90

100
Day

110

120

130

140
-83.95250’W49N-features1.dat’ u 1:4:5f(x) = 0.00260x + -84.04328
50

60

70

80

90

100

110

120

130

140

200
150

DEC offset [mas]Proper motions of water maser emission were measured
and analysed by Zhang+2013 (BeSSeL survey).

70 km s-1 at 11.1 kpc

2000

Day

1000

1005000-50-1000

VLSR (km s-1)

-1638.7-100-150-2000-200-250
2000

1000
0-1000RA offset [mas]-2000Conclusion and Future works
Ø The KaVA spectra have the flux density in the same trend withEffelsberg telescope.
Ø Found many new spots which have flux variability in eachepochØ The strongest flux for our results are found ~10,000 Jy and atthe centre.
Ø The proper motion of water masers are agreed well whencompared to previous work.
Ø The maser feature at the region (0.657, 0.226) arcsec is foundto be “flare” event and located inside the arc-like structure but
different position&velocity.
Future work: Need to do the velocity modelling >> outflow, shell expansion etc.

ขอบคุณคะ   
Thank you for your attention

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