The Extended Methanol The Extended Methanol Maser Emission in W51Maser Emission in W51

Chris Phillips

ATNF CSIRO

Chris.Phillips@csiro.au

Huib van Langevelde JIVE

Jim Caswell ATNF

Methanol MasersMethanol Masers

Methanol has rich microwave spectrum Many masing transitions

Strongest emission at 6.7 GHzOnly seen towards regions of massive star formationMany sources have linear structure with velocity gradients – Discs?May be a good tracer of massive protostars

W51W51

One of most luminous regions of massive star formation in the galaxy

Distance of 7 kpc (1” == 0.03pc)

Many distinct components Strongest “d” and “e” in 1 arcminute

region

ATCA ObservationsATCA Observations

Observed 6.7-GHz methanol maser emission towards ~20 northern methanol maser sources ATCA only connected element

interferometer which can observe 6.7 GHz

ATCA Observations

FWHM of Effelsberg at 6.7 GHz

EVN ObservationsEVN ObservationsObserved Feb 2002 4 stations only: Effelsberg, Torun,

Jodrell Bank and Onsala

Two fields of viewPhase referenced with a 3-6-6 minute duty cycleCorrelated at JIVE with a single pass and a 2 second integration timeDual polarisation with 1024 spectral points per pol

EVN Observations

• EVN• ATCA

60” / 2pc

•Greyscale

Methanol MasersVLA 3.6 GHz continuum

Mehringer etal 1994, ApJSS, 91 713

Gaume etal, 1993 ApJ 417 645Argon etal, 2000, ApJSS, 129, 159Imai etal, 2002, PASJ, 54, 741

MethanolOHWater

•••

3.6 cm VLA continuum (0.2”)

W51 Main

W51 IRS 2

MethanolOHWaterNH3 (1,1)

•••-

W51 Main

e1

e3

e2

e4 Zhang etal, 1997 ApJ 488, 241

M = 90 M

MethanolOHWaterNH3 (1,1)

•••-

W51 Main: e2

2”0.06 pc

MethanolOHWaterSiONH3 (1,1)

••••-

W51 d/IRS 2

Eisner etal, 2002, ApJ, 569, 334

+

+ NH3(9,8) maser

Spectral Type B0.5Size <300 AUEM = 5.9x109

= 2.1

ConclusionsConclusions

We have made phased referenced, wide field spectral line observations of the 6.7 GHz methanol maser emission in W51

The methanol traces a number of previously unreported regions of star formation

The linear maser emission in W51-main probably traces edge of HII rather than disc

The methanol in W51-d2 is associated with a very compact, very young HII region

AcknowledgmentsAcknowledgments

Ralph Gaume

David Mehringer

Alice Argon

Josh Eisner

Qizhou Zhang

Hiroshi Imai

Paolo Persi

Antonio Chrysostom

With many thanks to:

Overlays made using the package formally known as aips++