Public Seminar of MPhil Candidate:- Kinematics of an Infant Disk Galaxy in the Early Universe- the case of the Einstein Ring SPT0418–47
Galaxy formation at the early Universe is believed to be much more chaotic than the present epoch, with frequent mergers, strong supernova and AGN feedback and widespread gas inflow and outflow occurring in star-forming galaxies. Our knowledge of galaxy evolution between 0<z≲ 2 has improved rapidly in the last twenty years. Cosmological simulations encompassing the interplay between baryons and dark matter have reproduced galaxy populations with kinematics consistent with the huge observed samples of galaxies up to z∼2, the Cosmic Noon, when about half the mass of present day galaxies were assembled.
One main discovery of these studies is most star-forming galaxies remain rotating disks even up to z∼2, when the Universe was just ∼3 Gyr old. However, random motions also become increasingly important with increasing redshift. While simulations point to even stronger turbulence in star-forming galaxies at z>2, a special candidate at z=4.2 has emerged recently which lies seemingly well outside the trend, with the inferred rotation support comparable to present-day disk galaxies.
This object of interest, SPT0418–47, is an Einstein Ring with the source galaxy being magnified ∼30 times, making a resolved kinematic analysis possible. The speaker took advantage of the latest ALMA OHλ119 μm absorption data, together with the high-resolution ALMA [CII]λ158 μm emission data and their respective overlapping dust continuum emissions, to critically examine the rotation support of the source galaxy by careful modelling of the lens, source intensity and kinematics.
講者：Chun Hei YEUNG(香港大學)