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ALMA science with spectroscopic data

ALMA science with spectroscopic data. What will ALMA see?. ALMA will detect spectral line coming from molecular species from relatively cold (10-300 K), dense (>10 4 cm -3 ) gas; atomic transitions and ionised elements from high z galaxies, which are shifted to (sub)mm wavelengths;.

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ALMA science with spectroscopic data

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  1. ALMA science with spectroscopic data

  2. What will ALMA see? ALMA will detect spectral line coming from • molecular species from relatively cold (10-300 K), dense (>104cm-3) gas; • atomic transitions and ionised elements from high z galaxies, which are shifted to (sub)mm wavelengths; Faculty meeting 13 April 2007

  3. The power of spectral data The spectrum of a source is its fingerprint • Velocity structure and kinematics (ALMA will have a spectral resolution down to 0.01 km s-1) • Molecular abundances  evolutionary stages (and age?); they reflect the physics prevailing in the region; • Excitation studies  physical parameters of the gas (Tk and n(H2)) Faculty meeting 13 April 2007

  4. Excitation analysis • good tracers of temperature are • symmetric rotors (e.g. NH3, CH3CN), because radiative transitions between certain levels are forbidden, and can happen only through collisions; • molecules with low dipole moments (e.g. CO), because they are thermalised at low densities their level populations depend only on the kinetic temperature Faculty meeting 13 April 2007

  5. Excitation analysis • linear rotors with high dipole moments are good tracers of the density (e.g. CS, HCN and HCO+), because different transitions thermalised at different densities. • slightly asymmetric rotors (e.g. H2CO, CH3OH) CAN trace T and n Faculty meeting 13 April 2007

  6. SMA@220GHz IRAS 17233-3606 13CO CH3CN SiO HNCO Faculty meeting 13 April 2007

  7. Maiolino et al. 2006 For extragalactic studies: CII • Observations of at least one CO line per band; • isotopologues of CO; • HCN; • CI; • CII 158 m, 2<z<6; • and other atomic lines; Faculty meeting 13 April 2007

  8. The galactic case: star formation • High angular resolution (down to 0.01” ~1 AU at 150 pc, 30 AU at 3 kpc) • High spectral resolution (down to 0.01 km/s => kinematics and dynamics) • Multitude of lines => chemistry and excitation ALMA will • study outflow evolution; • study the parameters of outflows; • detect circumstellar disk in high-mass (proto)stars; • study the interaction of disks and outflows; • derive the mass of the central (proto)star from studies of kinematics Isella et al. 2007 Faculty meeting 13 April 2007

  9. The extragalactic case ALMA will: • confirm/determine spectroscopical redshifts; • study CO excitation (n>103cm-3) Tk CO column density and mass,  H2 mass. Problems: low J low density, high opacity. • HCN excitation  denser (n>105cm-3) gas than CO; • CI low opacity. We can derive T of the gas, CI column density and mass. CO and CI emissions are closely associated. • C+, which is the main coolant in the Milky Way, and which will probably be the only detection at high redshift Faculty meeting 13 April 2007

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