VERA

Jets%in%Massive%young%stellar%objects:% Ross%Burns%%
D3,%Kagoshima%U.%
The%`Water%spout’%and%the%`Micro<jet’%

RossBurns88@googlemail.com2

Abstract:%In%our%recent%water%maser%VLBI%observaMons%with%VERA%we%found%examples%of%two%interesMng%and%rare%types%of%
jets%associated%with%massive%young%stellar%objects%(MYSOs),%these%are%the%`water%spout’%and%the%`micro<jet’.%In%this%poster%
we%introduce%recent%observaMonal%results%and%brieﬂy%discuss%their%implicaMons%for%theories%of%massive%star%formaMon.%-40

Decl. offset (mas)

5 mas/yr-50-60Dec.
2037

Fig21.2Illustra6ve2descrip6on2of2the2Feature B
S235ABIMIR2MYSO2ouOlow2system2
35
showing2(leD)2HCO+2(1I0)2and2C34S2(5I4)2
from2[1],2and,2(right)2CS2(7I6)2from2[2]2Angular%momentum%1

33

15Dec.

Fig22.2The2maser2spectrum2of2S235ABIMIR2
as2a2func6on2of26me.2

10

Offset (mas)

-30s%

ut%

25

Offset (mas)-20

LSR velocity (km/s)

0-10

Ob se
rvaM
on

S235AB<MIR%is%a%11Mo,%
very%young%MYSO%with%two%
sets%of%bipolar%ounlows%
and%no%cenMmeter%
emission.%The%water%
41
masers%align%with%the%NNE<
39
SSW%ounlow%which%is%
traced%by%HCO+%and%C34S.%

10Water%Spo0R.A.

-1

We%observed%12%epochs%using%dense%
scheduling%with%VERA,%but%used%only% -2
Feature A
5R.A.
10%epochs%for%parallax%ﬁhng.%The%
29
In%disk%accreMon%theories%of%massive%star%formaMon%there%must%be%a%mechanism%of%removing%angular%Dec.
spectrum%%of%S235AB<MIR%looks%like%a%dominant%blue<shiW%maser%(DBSM)%
momentum%from%the%inner%disk%region%in%order%to%allow%accreMon%onto%the%star.%Proposed%ways%of%removing%
27
0-3(Fig%2).%0-2-4-6-8
angular%momentum%include:%Alven%waves,%magneMc%breaking%and%physical%removal%by%a%rotaMng%jet%launched%
2013
2014
2013
2014
VLBI%data%were%reduced%using%Fig23.2Parallac6c2mo6on2in2R.A.2(above)2and2
by%magneMc%ﬁelds%[3].%In%S235AB<MIR,%presented%here,%we%found%evidence%of%jet%rotaMon%in%the%3D%moMons%
R.A. offset (mas)
Year
Year
inverse%phase%referencing%in%AIPS.%
Dec.2(below)2for2masers2associated2with2the2
two2most2persistent2features,2aDer2
The%parallax%was%D%=%1.56%±%0.09%kpc%
of%water%masers,%observed%with%VERA.%We%named%this%type%of%jet%a%`water%spout’%[4].%The%existence%of%jet%
subtrac6ng2linear2proper2mo6ons.22(Fig%3).%
rotaMon%may%provide%the%`missing%link’%in%the%unexplained%momentum%budget%of%accreMng%MYSOs.%We%are%31

proposing%follow%up%observaMons%to%image%the%molecular%gas%in%the%jet%using%millimeter%interferometers.%
The%3D%moMons%of%the%water%masers%modeled%as%a%rotaMng%cylindrical%jet%of%7%AU%radius.%The%best<ﬁt%model%(Fig.%5)%had%80%%agreement%with%the%data.%The%model%
parameters%are%vout%=%45%±2%km/s,%vrot%=%22%±3%km/s,%%i%=%12±2◦%An%arMst’s%impression%of%what%the%`water%spout’%
might%look%like%is%shown%in%Fig%6.%%
ATDA%
LEOD

MFig%4.%(middle)%the%distribuMons%and%3D%moMons%of%water%masers%in%S235AB<MIR%at%full%scale.%
The%doUed%line%illustrates%the%jet%axis.%(leW)%Zoom%of%the%blueshiWed%maser%group,%showing%
the%velocity%gradient.%(right)%A%posiMon<velocity%(p<v)%diagram%perpendicular%to%the%jet%
direcMon.%The%straight%slope%in%the%p<v%diagram%is%suggesMve%of%solid<body%rotaMon.%
Fig26.2Ar6st’s2impression2of2the2`water2spout’2

Fig25.2The2bestIﬁt2model2to2the23D2maser2data2

Micro<je
Obser
t%
vaMon
s= LQ FK HQ NR / LX  6 X  HW DO

1 mas/yr30

2250

Fig27.2Illustra6ve2descrip6on2of2the2diskIouOlow2system2in2S255IR2showing2(leD)2CO2red2and2blue2contours2overlaid2on2
the2382GHz2con6nuum2map2[5].2(right)2The2disk,2traced2by2CH3OH2J=4I32[5],2overlaid2are2VERA’s2water2maser2vectors2-5

Episodic%ejecMon/accreMon%-10

Fig28.2The2maser2spectrum2of2S255IR22
as2a2func6on2of26me.2

80

400

5420

302-201-40 1 mas/yr%
AT
DA

10200

8100

6
40-100

00100

80

60

40

20

R.A. offset (mas)
References:%[1]%Felli%M.,%et%al.,%2004,%A&A,%420,%553%[2]%Wu,%J.%et%al.,%2010,%ApJS,%188,%313%%[3]%Konigl,%A.,%&%Pudritz,%R.%E.%2000,%Protostars%and%Planets%IV,%759%[4]%Burns,%R.%A.%et%al.,%2015,%MNRAS,%453,%3162%[5]%Zinchenko,%I.%et%al.,%2015,%ApJ,%810,%10%[6]%Carah%o%Garah%et%al.,%2015,%A&A,%573,%A82%[7]%Zinnecker,%H.%&%Yorke,%W.,%ARAA,%2007,%45,%481%[8]%K.%L.%J.%Rygl%et%al.,%2010,%A&A%511,%A2%2

1 mas/yr

400

12012300
Decl. offset (mas)LSR velocity (km/s)

Decl. offset (mas)400We%observed%12%epochs%with%VERA,%
but%used%only%8%epochs%for%parallax%
ﬁhng.%The%spectrum%of%S255IR%
shows%many%maser%components%
2009 evolving%over%Mme%(Fig%8).%
201020092010
2011
VLBI%data%were%reduced%using%
Year
Year
inverse%phase%referencing%in%AIPS.%
Fig29.2Parallac6c2mo6on2in2R.A.2(above)22
The%parallax%was%D%=%1.79%±%0.09%kpc% and2Dec.2(below)2for262features2aDer2(Fig%9)%which%is%consistent%with%the% subtrac6on2of2linear2proper2mo6ons.22
VLBA%parallax%(1.59%±%0.07%kpc)%
measured%using%6.7%GHz%methanol%
masers%[8].%Another%proposed%feature%of%disk<theory%massive%star%formaMon%is%that%accreMon%occurs%in%mulMple%
0-510
5intense%bursts.%In%our%recent%observaMons%of%S255IR%(IC2162),%presented%here,%we%see%a%`micro<jet’%–%
R.A. offset (mas)which%is%the%very%youngest%jet%structure.%This%is%signiﬁcant%because%S255IR%already%has%a%large<scale%(older)%ounlow%(Fig%7,%[5])%in%the%same%direcMon%as%the%`micro<jet’%(Fig%10)%–%therefore%the%ejecMons%from%
S255IR%happen%periodically.%The%Mght%correlaMon%between%ejecMon%acMvity%and%accreMon%acMvity%[6]%suggests%that%S255IR%is%also%accreMng%periodically%too%–%in%agreement%with%theory%[7].%%6010-20-40300
200
100
0R.A. offset (mas)-100

Fig210,2the2distribu6ons2and2proper2mo6ons2
of2water2masers2as2seen2by2VERA2

LSR velocity (km/s)-10%Offset (mas)Decl. offset (mas)-5

S255IR%is%a%20%Mo,%and%slightly%more%evolved%
MYSO,%as%inferred%by%
35
134
centemeter%emission%in%
30
the%dense%core.%The%MYSO% 25
132
has%a%clear%disk<ounlow%
20system%(Fig%7).%%
15
S255IR%has%water%masers%
130
10that%align%to%the%ounlow%
574
72
and%has%6.7%GHz%methanol%0masers%near%the%center%of%-5
the%system%[8]%-10-15-15-20-25-20-30

Offset (mas)