Transcript Spitzer mid-IR image of the DR21 region in the Cygnus-X molecular complex Image Credit: NASA, Spitzer Space Telescope.

Spitzer mid-IR image of
the DR21 region in the
Cygnus-X molecular
complex
Image Credit: NASA, Spitzer Space
Telescope.
To test our best models of methanol
masers
 To observe massive star formation at its
earliest stages

Energy Levels
of E-methanol
(Cragg et al,
2005).
J, K rotational
quantum
numbers, vt
and vCO
vibrational
Energy levels of Amethanol, with
decay paths to
astrophysical
maser population
inversions
illustrated with
arrows. (Cragg et
al, 1992).
6.7GHz transition is the first astrophysical methanol maser to
switch on in massive star-forming regions:
51 – 60 A +
Notation: JK – J’K’ Asgn(p)
Not strongly dependent
on gas temperature,
pumped by radiation
from dust
 Sharp switch on at ~110
K dust temperature, and
after that, not strongly
dependent
 Switch off over 108 cm-3
gas number density due
to thermal quenching
 Amplification along line
of sight for specific
column density 1011-1014
cm-3 s.

Left: MAMBO contour map of DR21
Right: MAMBO contour map with
8μm map overlaid
Image Credit: Motte et al, 2007.
Cygnus-X is a giant
molecular complex in
the Cygnus constellation,
a star forming region
with about 13 times the
mass of the Orion
nebula. DR21 is a cloud
in the north of Cygnus-X
in which we found
masers. We selected
targets identified by
stellar signposts such as
SiO outflows in Motte et
al, 2007.


Multi-Element Radio Linked Interferometer Network
Mark II (Jodrell Bank, pictured), Cambridge,
Defford, Knockin, Darnhall, Pickmere
Image Credit: Jodrell Bank Observatory.
Split peak corresponding
to a single maser
Single peak
corresponding to a
different maser
Calibration:
Bandpass to correct for
differences in sensitivity
across the spectrum.
Singlet and doublet as
yet not located
Amplitude and phase
calibrations for varying
conditions and forming
the image.
Pictured: Spectrum of DR21-N53 centred on 6.668GHz, produced with AIPS.

Two known masers confirmed and one to three
distinct new masers discovered

Null results on other targets: why?

Gas density sufficient in all targets: must be
temperature

Masers were detected in massive cores with strong
SiO outflows from their poles, as measured by
∫TSiOdv.
Brightness temperature (K)
SiO outflows from the poles were
an indicator of stellar activity we
used to select our targets.
Maser
Maser?
No Maser
Velocity (kms-1)
Maser?
Left: spectra of the six strongest
SiO outflows.
Maser?
Two to four of the targets to the
left have methanol masers, and
no others in the sample of 17. N12
and N40 have much lower mass
than the maser candidates.
Maser
Hypothesis: only those protostellar
cores with the strongest SiO
outflows have methanol masers.
Image Credit: Motte et al, 2007.
Improve phase calibration and image
the masers, i.e. are they in disks?
 Map velocity distribution in the masers:
what are the characteristics of the disk?
 Confirm SiO – methanol correlation with
larger samples and greater sensitivity
 Extend to mid-IR sources

Thank you to Dr Lisa Harvey-Smith for her
encouragement, ideas, endless
debugging and giving me the
opportunity to do the project in the first
place!