A 3-D perspective to the internal properties of low and high-redshift galaxies

Abstract

In the present work, I study the morpho-kinematics of two moderate galaxy samples at low- and high-redshift. I analyse the internal kinematics of these galaxies aiming to find possible correlations between the kinematic state of the interstellar medium (ISM) and its physical properties, including the study of the star formation activity and possible evolution- ary trends with cosmic time. Through the use of Integral Field Unit (IFU) and Atacama Large Millimeter/submillimeter Array (ALMA) observations, I characterize the ionized and molecular ISM gaseous phases on galaxies at different redshifts. The galaxy dynamics are characterized through the modelling of the two-dimensional morpho-kinematic maps. These are derived by fitting the observed emission lines in each pixel of the datacubes. Photometric models from broad-band galaxy images are implemented to aid the kinematic modelling and overcome parameter degeneracy. At redshift z = 0.8 − 2.2, I present spatially-resolved observations of eleven galaxies detected in the H-alpha emission line (Hα). Combining these observations with data from a previous campaign, I construct a total sample of twenty galaxies. I find that galaxy interactions might be the dominant mechanism controlling the star-formation activity at z ≈ 2.2 but they become gradually less important down to z ≈ 0.8. For two galaxies taken from the above sample, I observe the CO(J = 2 − 1) emission line, resolved at ∼kpc-scales, using ALMA. I just detect the emission coming from one galaxy at these scales. For this system, I observe that the morpho-kinematics traced by the ionized and molecular gas agree. For this galaxy, I derive a dark matter fraction (fDM ≡ MDM/Mdyn) of 0.6 ± 0.1, in agreement with the average fDM value derived from stacked rotation curve analysis of galaxies at similar redshift range. On the other hand, at low-redshift, I use ALMA spatially-resolved observations of molec- ular gas on galaxies up to z ≈ 0.35. I find a correlation between the galactic kinematics and the ionized Carbon to Infra-red luminosity ratio ([Cii]/IR), suggesting that the so-called ‘[Cii] deficit’ is related to the dynamical state of the galaxies. I conclude that the morpho-kinematic state of galaxies is intimately related to the ISM physical properties. This implies that the galaxy dynamics can not be overlooked to obtain a complete characterisation of the evolution of galaxies across cosmic time.