1,061 research outputs found
Ks-band (2.14 micron) imaging of southern massive star formation regions traced by methanol masers
We present deep, wide-field, Ks-band (2.14 micron) images towards 87 southern
massive star formation regions traced by methanol maser emission. Using
point-spread function fitting, we generate 2.14 micron point source catalogues
towards each of the regions. For the regions between 10 degrees and 350 degrees
galactic longitude and galactic latitude +/- 1 degree, we match the 2.14 micron
sources with the GLIMPSE point source catalogue to generate a combined 2.14 to
8.0 micron point source catalogue. We provide this data for the astronomical
community to utilise in studies of the stellar content of embedded clusters.Comment: Accepted PASA. Full version including figures available from
http://www.cfa.harvard.edu/~slongmor/snl_iris2_withfigs.pd
Physical characterisation of southern massive star-forming regions using Parkes NH observations
We have undertaken a Parkes ammonia spectral line study, in the lowest two
inversion transitions, of southern massive star formation regions, including
young massive candidate protostars, with the aim of characterising the earliest
stages of massive star formation. 138 sources from the submillimetre continuum
emission studies of Hill et al., were found to have robust (1,1) detections,
including two sources with two velocity components, and 102 in the (2,2)
transition.
We determine the ammonia line properties of the sources: linewidth, flux
density, kinetic temperature, NH column density and opacity, and revisit
our SED modelling procedure to derive the mass for 52 of the sources. By
combining the continuum emission information with ammonia observations we
substantially constrain the physical properties of the high-mass clumps. There
is clear complementarity between ammonia and continuum observations for
derivations of physical parameters.
The MM-only class, identified in the continuum studies of Hill et al.,
display smaller sizes, mass and velocity dispersion and/or turbulence than
star-forming clumps, suggesting a quiescent prestellar stage and/or the
formation of less massive stars.Comment: 20 pages, 9 Figures, 1 appendix (to appear in full online only, a
sample appendix in the paper); 7 tables. Accepted by MNRA
The molecular environment of massive star forming cores associated with Class II methanol maser emission
Methanol maser emission has proven to be an excellent signpost of regions
undergoing massive star formation (MSF). To investigate their role as an
evolutionary tracer, we have recently completed a large observing program with
the ATCA to derive the dynamical and physical properties of molecular/ionised
gas towards a sample of MSF regions traced by 6.7 GHz methanol maser emission.
We find that the molecular gas in many of these regions breaks up into multiple
sub-clumps which we separate into groups based on their association
with/without methanol maser and cm continuum emission. The temperature and
dynamic state of the molecular gas is markedly different between the groups.
Based on these differences, we attempt to assess the evolutionary state of the
cores in the groups and thus investigate the role of class II methanol masers
as a tracer of MSF.Comment: 5 pages, 1 figure, IAU Symposium 242 Conference Proceeding
Tracing the Conversion of Gas into Stars in Young Massive Cluster Progenitors
Whilst young massive clusters (YMCs; 10 M, age
100 Myr) have been identified in significant numbers, their
progenitor gas clouds have eluded detection. Recently, four extreme molecular
clouds residing within 200 pc of the Galactic centre have been identified as
having the properties thought necessary to form YMCs. Here we utilise far-IR
continuum data from the Herschel Infrared Galactic Plane Survey (HiGAL) and
millimetre spectral line data from the Millimetre Astronomy Legacy Team 90 GHz
Survey (MALT90) to determine their global physical and kinematic structure. We
derive their masses, dust temperatures and radii and use virial analysis to
conclude that they are all likely gravitationally bound -- confirming that they
are likely YMC progenitors. We then compare the density profiles of these
clouds to those of the gas and stellar components of the Sagittarius B2 Main
and North proto-clusters and the stellar distribution of the Arches YMC. We
find that even in these clouds -- the most massive and dense quiescent clouds
in the Galaxy -- the gas is not compact enough to form an Arches-like ( =
2x10 M, R = 0.4 pc) stellar distribution. Further
dynamical processes would be required to condense the resultant population,
indicating that the mass becomes more centrally concentrated as the
(proto)-cluster evolves. These results suggest that YMC formation may proceed
hierarchically rather than through monolithic collapse.Comment: 12 pages, 8 figures, 1 table. Accepted by MNRA
Embedded Stellar Populations towards Young Massive Star Formation Regions I. G305.2+0.2
We present deep, wide-field J, H and Ks images taken with IRIS2 on the Anglo
Australian Telescope, towards the massive star formation region G305.2+0.2.
Combined with 3.6, 4.5, 5.8 and 8.0 micron data from the GLIMPSE survey on the
Spitzer Space Telescope, we investigate the properties of the embedded stellar
populations. After removing contamination from foreground stars we separate the
sources based on their IR colour. Strong extended emission in the GLIMPSE
images hampers investigation of the most embedded sources towards the known
sites of massive star formation. However, we find a sizeable population of IR
excess sources in the surrounding region free from these completeness effects.
Investigation reveals the recent star formation activity in the region is more
widespread than previously known.
Stellar density plots show the embedded cluster in the region, G305.24+0.204,
is offset from the dust emission. We discuss the effect of this cluster on the
surrounding area and argue it may have played a role in triggering sites of
star formation within the region. Finally, we investigate the distribution of
IR excess sources towards the cluster, in particular their apparent lack
towards the centre compared with its immediate environs.Comment: 16 pages, 16 figures (significantly size reduced), 2 tables, accepted
MNRA
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