| Description |
LIRGs and ULIRGs are found to deviate strongly from the mass-metallicityrelation. More specifically, at a given stellar mass, the metallicity of LIRGs and ULIRGs, as inferred from optical spectroscopy, is much lower than the value expected from the mass-metallicity relation observed in normal star-forming galaxies. This metallicity anomaly of LIRGs and ULIRGs has been ascribed, by many models, to the inflow of metal poor gas, from the galaxy outskirts, induced by the tidal forces associated with these merging systems. However, an alternative possible scenario is that in these dusty systems optical spectra only probe the outer, metal poor regions, while the bulk of the gas is actually metal rich, but it is heavily absorbed by dust. We propose a definitive test of the scenarios discussed above byobtaining an independent, extinction-free measurement of the gas metallicity in a sample of LIRGs-ULIRGs, by exploiting newly developedfar-IR metallicity diagnostics. In particular, we have recently shownthat by measuring the relative intensities of the fine structure linesOIII52um, OIII88um, NIII57um and NII122um, it is possible to constrain the gas metallicity with high accuracy and in a wavelength range nearly unaffected by dust extinction. If these far-IR diagnostics confirm the low metallicities observed in the optical spectra, this would support models envisaging inflow of metal poor gas in interacting systems. If, instead, the far-IR diagnostics measure much higher metallicities, this would favor the scenario where the bulk of the gas is metal rich, but heavily absorbed, and it has been elusive to optical observations. |
| Keywords |
Herschel Space Observatory data, ESA Herschel mission dataset, far-infrared astronomy observations, submillimeter astronomy data, infrared space telescope observations, PACS photometer data, PACS spectrometer data, SPIRE photometer data, SPIRE Fourier transform spectrometer data, HIFI heterodyne spectroscopy data, far-infrared spectroscopy dataset, submillimeter spectral line observations, cold universe observations dataset, star formation infrared data, molecular cloud far-infrared observations, interstellar medium spectroscopy data, protoplanetary disk infrared observations, galaxy evolution far-infrared data, dust emission submillimeter observations, cosmic infrared background measurements, extragalactic infrared survey data, calibrated level 2 data products, FITS files astronomy, spectral cubes far-infrared, flux-calibrated maps, continuum photometry data, spectral energy distribution measurements, ESA Herschel Science Archive data |
