1. Millimeter Spectroscopy Joanna Brown

2. Why millimeter wavelengths? >1000 interstellar & circumstellar molecular lines Useful for objects at all different distances –Emission from active star-forming galaxies –Observe protostars and protoplanetary disks –Atmospheres of local planets and their moons –Synchrotron emission from our Sun Radio astronomy so interferometers make probing small spatial scales possible

3. Millimeter transparency Atmospheric absorption from water (plus CO 2 and O 2 )

5. Dust continuum Continuum emission comes from dust in disk Provides a measure of dust mass Helps constrain grain chemistry for processes such as the formation of H 2

6. CO CO is one of the commonest molecules observed at millimeter wavelengths Abundances are higher than for most other molecules, traces gas mass CO(1-0) is at 115 GHZ and CO(2-1) is at 230 GHZ With an interferometer can spatially resolve and look at velocity structure

7. CO(1-0) and continuum emission AB Aur: continuum emission with CO contours and velocity structure

8. Other molecules 13 CO, C 18 O - more likely to be optically thin than 12 CO HCO + - ionization fraction which has important effects for chemistry (ion- molecule vs neutral-neutral reactions), traces most dominant ion H 3 +, ionization due to cosmic rays and stellar X-rays

9. Nitrogen chemistry Kessler thesis 2003 CN/HCN ratio probes UV field HNC - formation of HCN by ion- molecule pathways Very sensitive to temperature and UV field

10. Combining with other wavelengths Millimeter traces outer, cool regions of the disk Combined with near- and far-IR can look at all regions of the disk to fully understand protoplanetary disks and their chemistry