Seminars at FGG

First spectrally complete survey of cometary water emission at near IR wavelengths : C/2014 Q2 Lovejoy with TNG/GIANO spectrograph.

Speaker: Sara Faggi (INAF - OA Arcetri - Italy)

Date and time: 2016-02-03 11:30

Comets are the most pristine bodies of Solar System and water is the most abundant constituent of cometary ice – its production rate is used to quantify cometary activity and the measurements of ortho-para ratio can clarify the nature and meaning of the spin temperature in the cosmic context. Last February 2015, we acquired the first comprehensive high resolution spectral survey of comet C/2014 Q2 Lovejoy in the 0.9-2.5 µm range, by observing with GIANO - the near-IR spectrograph on TNG (the Italian Telescopio Nazionale Galileo in La Palma, Canary Islands, ES). We detected emissions of radical CN, water (H2O), and many undefined emission features. We quantified the water production rate by comparing the calibrated line fluxes with the NASA Goddard full non resonance fluorescence cascade model for H2O. The production rate of ortho and para water provide an estimation of ortho to para ratio consistent with statistical equilibrium (3.0), but the confidence limits are not small enough to enable a critical test of the nuclear spin temperature in this comet. Until now, high-resolution spectroscopy in the infrared (2.7 - 5µm) has been a powerful tool to quantify molecular abundances in cometary comae. Today the expansion to the near-IR region (0.9-2.5 µm) will extend this capability to new band systems. Our observations open a new pathway for cometary science in the near-infrared spectral range (0.9-2.5 µm) and establish the feasibility of astrobiology-related scientific investigations with future high resolution IR spectrographs on 30-m class telescopes, e.g., the HIRES spectrograph on the E-ELT telescope.