Proposal: Technical justification
"Technical justification, including the timeline for the proposed observations. "
Time per cloud?
We requested ~100 hours for NGC 1333 and got 130 total hours. This achieved a mean S/N across the cloud of ~15 for N2H+, ~25 for HCN, and ~180 for HCO+.
Mean properties of ~3700 spectra:
- HCO+: 0.022 K rms offline, 4 K peak brightness
- HCN (weakest line): 0.035 K rms offline, 0.87 K peak brightness
- N2H+ (weakest line): assuming ~0.03 K rms offline, 0.53 K peak brightness
8 MHz or 31 MHz Bands?
- We observed NGC 1333 in 31 MHz bands with ~0.6 km/s resolution. This is getting us 4-5 channels across the line.
- We would like to go to 8 MHz bands to get ~0.15 km/s resolution, but this only provides 24 km/s of velocity coverage.
- How will this affect our ability to characterize outflows?
- HCN with no outlow covers about 16 km/s, which would be 105 of our 159 channels in an 8 MHz band in 3-bit mode
- HCN with big outflow covers about 37 km/s, which would be missed by our 24 km/s coverage across the 8 MHz band in 3-bit mode
- Can we just rely on the HCO+ to study the outflows? We can capture most of the biggest outflows within ~20 km/s.
Which Molecular Tracers?
We can get 3 narrow bands in a single 8 GHz sideband.
- We observed NGC 1333 in:
- HCN (1-0) 88.632 GHz | Tracer of dense gas and infall motion
- HCO+ (1-0) 89.188 GHz | Tracer of dense gas and outflows
- N2H+ (1-0) 93.171 GHz | Tracer of dense, quiescent gas, depletes late
- Possible 3mm tracers:
- C2H (1-0) | 87.4 GHz | Traces early cores(?) Quickly depleted(?)
- HNC (1-0) | 90.663 GHz | Tracer of dense gas, ratio to HCN dependent on temperature
- HC3N (10-9) | 90.979 GHz | Tracer of very dense gas, abundant in warmer, shielded regions
- CS (2-1) | 97.981 GHz | Tracer of dense gas, may deplete towards center of cores, trace outflows
- C18O (1-0) | 109.78 GHz
- 13CO (1-0) | 110.2 GHz
- CN (1-0) | 113.5 GHz | Tracer of dense gas
- CO (1-0) | 115.271 GHz