UCI率いる天文学チームが、塵に覆われた銀河の金属の証拠を発見(UCI-led astronomy team finds evidence of galactic metal shrouded in dust)


赤外線の放射が、光学波長での観測では見えない秘密を解き明かす Infrared emissions reveal secrets invisible with optical wavelength observations

2022-06-01 カリフォルニア大学校アーバイン校(UCI)



超大質量赤外線銀河の低い気相メタリック度は、塵によるオブスキュアの結果である Low gas-phase metallicities of ultraluminous infrared galaxies are a result of dust obscuration

Nima Chartab,Asantha Cooray,Jingzhe Ma,Hooshang Nayyeri,Preston Zilliot,Jonathan Lopez,Dario Fadda,Rodrigo Herrera-Camus,Matthew Malkan,Dimitra Rigopoulou,Kartik Sheth & Julie Wardlow
Nature Astronomy  Published:26 May 2022


Optical spectroscopic measurements show that gas in dusty, starbursting galaxies known as ultraluminous infrared galaxies (ULIRGs) in the local Universe has a significantly lower metal content than that of gas in star-forming galaxies with similar masses. This low metal content has resulted in the claim that ULIRGs are primarily fuelled by metal-poor gas falling into those galaxy merger systems from large distances. Here we report a new set of gas-phase metal abundance measurements taken in local ULIRGs using emission lines at far-infrared wavelengths tracing oxygen and nitrogen. These new data show that ULIRGs lie on the fundamental metallicity relation determined by the stellar mass, metal abundance and star formation rate as the key observational parameters. Instead of metal-poor gas accretion, the new data suggest that the underabundance of metals derived from optical emission lines is probably due to heavy dust obscuration associated with the starburst. As dust-obscured, infrared-bright galaxies dominate the star formation rate density of the Universe during the peak epoch of star formation, we caution the use of rest-frame optical measurements alone to study the metal abundances of galaxies at redshifts of 2–3.