Comparing direct and IR fine-structure metallicity measurements

Lead Research Organisation: University of Cambridge
Department Name: Physics


Understanding the processes regulating the heavy element content ('metallicity') of galaxies is one of the most important problems in astrophysics. Many studies in recent years have had great success in developing our understanding of metallicity, both in the local Universe and at high redshift. These studies have resulted in a great advance in our knowledge of the physics underlying galaxy evolution.

It is, however, critical to note that essentially all of these findings were conducted using optical light, and are therefore likely to be strongly biased. Optical lines are poor probes of highly dusty regions: optical metallicity tracers can therefore fail to probe the very regions which are driving galaxy evolution.

We are contacting a matched study, comparing metallicity relations derived both in the optical and the infra-red for a sample of dusty galaxies. These galaxies have existing Herschel far-IR spectroscopy (and far-IR-derived metallicities), which are minimally affected by dust.

This observing trip is undertaken in order to conduct a program of optical spectroscopy to derive 'direct' optical metallicities for this sample, to enable a comparison between metallicities derived using traditional optical methods, and IR line methods.


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Bothwell M (2016) Molecular gas as the driver of fundamental galactic relations in Monthly Notices of the Royal Astronomical Society

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Pallottini A (2015) Mapping metals at high redshift with far-infrared lines in Monthly Notices of the Royal Astronomical Society

Description The observations were successful, with clear detection of the key metallicity diagnostics of the target galaxies. These data have been used to investigate metallicity scaling relations.
Exploitation Route Additional observations on a larger sample of galaxies.
Sectors Other