MALT90 Parameters
Summary Table
| Number of dense cores observed | 2,000 |
| Number of Pre-stellar cores | 700 |
| Number of Protostellar cores | 500 |
| Number of HII Region cores | 600 |
| Number of PDR cores | 200 |
| Angular Resolution | 38 arcsec |
| Spectral Resolution | 0.11 km/s |
| Lines mapped simultaneously | 16 |
| Size of each map | 3 arcmin x 3 arcmin |
| Sensitivity (TA x rms at 0.11 km/s) | 0.2 K |
| Total Survey size | 1.2+ TBytes |
| Time for one map | 1.18 hours |
| Total time for survey | 2800 hours |
| Survey Region | +20° > l > +3° and -3° > l > -60° |
| Complete to cores with M > 200 Msun | 7 kpc |
| Dates of data collection | Austral winter 2010-2013 |
Lines observed
| IF | Line | Frequency (MHz) | Tracer |
|---|
| 1 | N2H+(1-0) | 93,173.480 | Density, chemically robust |
| 2 | 13CS (2-1) | 92,494.303 | Column density |
| 3 | H41α | 92,034.475 | Ionized gas |
| 4 | CH3CN 5(1)-4(1) | 91,985.316 | Hot core |
| 5 | HC3N (10-9) | 91,199.796 | Hot core |
| 6 | 13C34 S(2-1) | 90,926.036 | Column density |
| 7 | HNC (1-0) | 90,663.572 | Density; cold chemistry |
| 8 | HC13CCN (10-9) | 90,593.059 | Hot core |
| 9 | HCO+ (1-0) | 89,188.526 | Density |
| 10 | HCN (1-0) | 88,631.847 | Density |
| 11 | HNCO (41,3 - 31,2) | 88,239.027 | Hot core |
| 12 | HNCO (40,4-30,3) | 87,925.238 | Hot core |
| 13 | C2H (1-0) | 87,316.925 | Photodissociation tracer |
| 14 | HN13C (1-0) | 87,090.85 | Column density |
| 15 | SiO (2-1) | 86,847.010 | Shock/outflow tracer |
| 16 | H13CO+ (1-0) | 86,754.330 | Column density |
Classification Scheme
Although ATLASGAL is an excellent finding chart for dense cores, it contains a heterogeneous mix of warm and cold cores spanning a wide range of masses. In order to adequately sample high-mass star-forming dense cores in both the cold pre-stellar phase and the warm protostellar and HII region phases, it is necessary to classify the evolutionary state of the star-formation activity taking place within the cores. Fortunately, the Spitzer infrared surveys GLIMPSE and MIPSGAL allows one to separate the cores into the various evolutionary states. We use these surveys to categorize the cores into four groups.
Pre-stellar
Since these are cold and very dense, pre-stellar cores will be infrared dark in the GLIMPSE 3.6 to 8.0 µm and MIPSGAL 24 µm images.
GLIMPSE 3.6, 4.5 and 8.0 µm image |
GLIMPSE 3.6, 8.0 µm/MIPSGAL 24 µm |
Protostellar
Accretion onto a protostar is signalled by warm dust. Thus, an embedded 24 µm point source in MIPSGAL with no GLIMPSE emission indicates an embedded, accreting protostar. An additional sign is the presence of extended 4.5 µm emission, the characteristic "green fuzzy".
GLIMPSE 3.6, 4.5 and 8.0 µm image |
GLIMPSE 3.6, 8.0 µm/MIPSGAL 24 µm |
HII Region
When the HII region forms, the surrounding gas and dust are heated and the infrared emission associated with the core will be bright in both GLIMPSE and MIPSGAL images. The morphologies of HII regions range from compact, to extended, with some displaying bubble-like morphologies.
GLIMPSE 3.6, 4.5 and 8.0 µm image |
GLIMPSE 3.6, 8.0 µm/MIPSGAL 24 µm |
Photodissociation Region (PDR)
The UV radiation from a recently formed high-mass star will produce a photodissociation region (PDR) at the molecular/ionised gas interface. The PDR will be extended and emit strongly in the GLIMPSE 8 um images. Moreover, extended 24 um emission indicative of hot dust will also be present. PDRs will have extended morphologies.
GLIMPSE 3.6, 4.5 and 8.0 µm image |
GLIMPSE 3.6, 8.0 µm/MIPSGAL 24 µm |
