The Red MSX Source Survey
The Red MSX Source (RMS) survey was conceived at Leeds to
systematically search the entire Galaxy for massive young stellar
objects (MYSOs). MYSOs are luminous
(L > 104
), embedded infrared sources that
have yet to begin
ionising their surroundings to form an ultra-compact H II region. They
are likely to be already burning hydrogen in their cores, whilst still
accreting at the surface. They drive bipolar molecular outflows and
often have a compact ionised stellar wind and associated maser activity.
Most of their energy comes out in the infrared after reprocessing by
the dense circumstellar dust envelope. This is therefore the most
logical and unbiased way of searching for such objects. Ideally we
would use the far-IR where the spectral energy distribution peaks. The
only existing survey at these wavelengths is that by the IRAS
satellite, but that suffers from confusion in the galactic plane.
Hence, previous searches for MYSOs using IRAS data have been biased
towards bright, isolated examples (e.g. Molinari et al. 1998; Sridharan
et al. 2002). The much higher resolution mid-IR survey of the galactic
plane by the
(Price et al. 2001) provided the opportunity
for a large comprehensive search for MYSOs in the galaxy. Of course the use of mid-IR selection
means that we will not detect earlier phases like the hot molecular
We select sources from the MSX point source
catalogue that have the
same colours as well-known MYSOs. In addition, we use near-IR data from
the 2MASS survey. We do not demand a detection as that would rule out
many of the very embedded or obscured MYSOs that we want to detect, but
use it to eliminate objects too blue in the near-IR to be MYSOs. The colour
selection process (Lumsden et al. 2002) yielded about 2000 candidate MYSOs after further
visual inspection of the MSX images had eliminated a significant number
of sources that did not appear to be point-like despite being listed in
the MSX PSC. Colour-colour diagrams with the colour cuts indicated are
Many other objects have very similar near- and mid-IR colours to the
very red MYSOs we are looking for. These include ultra-compact H II
regions, compact planetary nebulae, low-mass YSOs and evolved stars.
Hence, we are carrying out an extensive multi-wavelength campaign to
identify and eliminate these confusing objects from the sample.
It is this follow-up work that enables the RMS survey to deliver the large
sample of MYSOs that will open up a new era of systematic and
statistical studies of this important phase of massive star formation.
The RMS Database
The RMS survey database can be found here.