21cm HI studies of the Milky Way and nearby galaxies. (Surveys, emission, absorption, self-absorption, interaction of individual sources with the ISM)
HI is the fundamental tracer of neutral gas in the universe at all times and on all scales. The SKA will provide an unprecedented view of the structure and motion of gas inside and outside of galaxy disks. The SKA will be able to survey HI 21-cm emission from large numbers of spiral and dwarf irregular galaxies (out to z~1), and to map the distribution of the HI in the Milky Way at unprecedented resolution and sensitivity. This encompasses level-1 science for working groups 1, 3 and 4.
Additional notes: WG1 Bologna ; WG1 pre-Groningen ; WG1 post-Groningen .
SKA Designs (requirements matrix)
| Specification | Requirement | China | Europe | India | Ozlens | Ozcyli | USA | Canada |
| A/Tsys | 20000 | 35000 | 10500 | 20000 | 20000 | 20000 | 20000 | 20000 |
| FOV (deg2) | 1 | 0.005 | 1 | 1 | 3.6 | 1 (8) | 1 | 1 (FPA) |
| #beams | 1 | 8 | 1 | 2 | 8 (64) | 1 | 350 | |
| beam separation | 90 | 150 | 40x1 | 1 | ||||
| #subarrays | few | many | many | many | many | many | few? | |
| response time | 100 | <1 | 60 | 60 | 60 | 60 | 100 | |
| Freq range | 1.4 | 0.3-6.0 | 0.15-1.5 | 0.15-10.0 | 0.1-5.0 | 0.10-9.0 | 0.15-34.0 | 0.1-22.0 |
| Corr Bandwith | <<1 | ? | 0.2 | 1.5 | 2.4 | 3.2 | 4.0 | |
| #spectral channels | 4000 | 2x4096 | 2x4096 | 2x4096 | 16384 | |||
| sampling time | 2 | short | ||||||
| max baseline | 50 | 300 | 2000 | 3000 | 10000 | 5000 | ||
| 50% area baseline | <7 | 50 | 100 | 4 | 3 | 35 | ? | |
| Tb sensitivity | 1 | ? | 1 | 1 | 0.7 | 1 | ? | |
| #independent IFs | 2 | 3 | 4 | 4 | 4 | |||
| Max sep. of IFs | <1GHz | 1 | full band | full band | ||||
| Spatial DNR | 1e+04 | 1e+05 | 1e+06 | 1e+06 | 1e+06 | 1e+06 | ||
| Spectral DNR | 1e+03 | |||||||
| Polarization DNR | -40dB | 1e+04 | 1e+04 | |||||
| #spatial pixels | 2e+07 | 1e+08 | 1e+08 | 5e+10 | ||||
| Special | Contin UV 1-1800arcsec | 0.2-2km UV gap | 0.2-1km UV gap |