Probing The Processes Driving Distant And Local Star-formation Through Dust And Molecules

Studies on galaxy evolution have been revolutionized during the last decade thanks to the state-of-the-art telescopes and instruments.Herschel Space Telescope,ALMA and NOEMA interferometers can observe the dust emission that traces star formation missed by optical to near-infrared telescopes.Their high sensitivity pushes further their detections to the most distant galaxies or the faintest local galaxies,of which the formation and evolution challenge current theories and models.And the integral field unit technique combines the spatial information with the properties extracted from spectra which allows a thorough study of galaxy kinematics.In this thesis,I focus on the large-scale(?kpc)star formation of galaxies.Taking advantage of the data from Herschel,ALMA,NOEMA,and the SAMI IFU survey,my thesis tries to put more constraints on the following questions:(1)How did the first galaxies form stars out of gas with little metal?(2)How did the massive galaxies in the early Universe rapidly build up their masses and finally stop forming stars?and(3)what is the role played by the environments they reside in?(4)How does star formation feedback affect the galaxy kinematics?A large portion of the work done in this thesis is based on the GOODS-ALMA survey,the largest cosmological survey with the large ALMA interferometer at 1.1 mm.I studied the six optically dark galaxies with redshifts greater than z=3 uncovered by this survey.We present evidence that four out of the six optically dark galaxies belong to the same overdensity of galaxies at z?3.5.One of them,AGS24(M=1011.32-0.19 +0.02 M?),is the most massive galaxy without an active galactic nucleus at z>3 in the GOODS-ALMA field.It also falls in the very center of the galaxy surface density peak,suggesting that the surrounding overdensity is a proto-cluster in the process of virialization and that AGS24 is the candidate progenitor of the future brightest cluster galaxy.My work on the energy sources of the turbulent motions shows that on sub-kpc scales,local star-forming galaxies from the SAMI survey display a flat distribution of ionized gas velocity dispersion as a function of star formation rate surface density.However,the velocity dispersion floor is higher than predicted by feedback-driven models.This suggests that additional sources to star formation feedback drive random motions of the interstellar medium in star-forming galaxies.I also studied the molecular gas content in IZw18,one of the most metal poor galaxies in the local Universe based on the observation of NOEMA.I obtain an upper limit of CO J=2-1 emission,which is used as a tracer of molecular gas,to be ten times lower than previous studies despite its vigorous star formation activities.Such low CO content relative to its infrared luminosity,star formation rate and[C?]luminosity,indicates a drastic change in the structure of the ISM at around a few percentages of Solar metallicity.Especially,the high[C?]luminosity relative to CO implies a larger molecular reservoir than the CO emitter in IZw18.Finally I present my work on the spatially resolved dust emission of extremely metal-poor galaxies observed by Herschel.These galaxies show higher dust temper-atures and lower emissivity indices compared to those of spiral galaxies.And about half of the emission at 100 ?m comes from warm(50 K)dust,in contrast to the cold(?20 K)dust component.The far-infrared colours are all related to the surface densities of young stars,but not to the stellar mass surface densities.This suggests that their dust emission(70?350 ?m)is primarily heated by radiation from young stars.