Investigating the origin of species and activity in cometary comae
Proposer(s): Cyrielle Opitom, Alessandra Migliorini, Monica Lazzarin, FIorangela La Forgia, Yuna Kwon,
Description: Comets are among the most pristine relics of the protoplanetary disc, where planets formed and evolved. When a comet approaches the Sun, the ices contained in its nucleus sublimate to form an atmosphere of gas and dust around the nucleus called the coma. By observing the composition of the coma, we can probe cometary ices retaining precious clues about the conditions prevailing in the early stages of our solar system.
One outstanding issue is to link the radicals observed at optical wavelengths in the coma to the abundances of ices in the nucleus. It has been shown in recent years that key steps toward answering that question can be made using IFUs to produce simultaneous maps of the spatial distribution of different radicals in the coma (Opitom et al., 2019). IFUs mounted on large telescopes have also proven very efficient to detect faint levels of activity around solar system objects (Opitom et al., 2020). Even if cometary activity has been studied for decades, we still lack a consistent picture of the activity of small bodies across the solar system, especially far from the Sun. The drivers of cometary activity at large distances from the Sun remain poorly understood and we haven’t yet been able to confirm the existence of ice in main-belt comets. A key issue with current IFUs is the field of view covered. The coma of comets can spread over arcminutes, and the limited FoV on MUSE and likely the future BlueMUSE means we are unable to sample the whole coma.
A wide FoV IFU mounted on a 10m-class telescope would allow us to significant extend the study for species parentage in comets and the search for activity around small bodies across the solar system (such as main belt comets), providing key clues to link optical observation of comets to nucleus ice abundances and constraints to models of the solar system formation and evolution.
With the current wavelength coverage, we will cover emissions from the following radicals: CN, N2+, CO+, C2, NH2, and [OI]. N2+ and CO+ are particularly interesting as they can provide indication on the relative abundance of N2 and CO in comets, which is a very sensitive indicator of their formation temperatures but has been measured in very few objects so far. Extending the wavelength coverage to 300 nm would cover the very bright OH (0-0) emission band around 310 nm, which has been identified as one of the most powerful probes of water outgassing in the solar system (Snodgrass et al., 2017). The 300-400nm range will not be covered by any of the future giant telescopes.
Transverse interests: This is related to other solar system science cases
Target properties
Target type: Comets: extended targets, needing non-sidereal tracking, ToO-type
Target density: /
Magnitude range: mag(V) in the range 0-21
Max Nobject in a 5 years survey: Difficult to estimate as the number of new objects varies
Requirements
Instruments: IFS
Field of view: FOV of at least 9acrmin2
Wavelength range: 370 - 800nm essential, ideal is 300 - 930 nm
Spectral resolution: 3000
Typical exposure time: 1h total (4x10min + overheads)
WST’s transformative nature :
Main competitor(s): MUSE, BlueMUSE
Limits of competitor(s): Limited FoV for extended objects
Unique elements of WST for this science case: IFU with large FoV