We investigate the specific angular momentum (sAM) j((star)((star) proportional to M-star(alpha) with an index alpha varying from alpha = 0.3 to alpha = 0.5, from log M-star/M-circle dot = 8 to log... Show moreWe investigate the specific angular momentum (sAM) j((star)((star) proportional to M-star(alpha) with an index alpha varying from alpha = 0.3 to alpha = 0.5, from log M-star/M-circle dot = 8 to log M-star/M-circle dot = 10.5. The UDF sample supports a redshift evolution (j) over tilde (star proportional to) (1 + z)(a), with a = 0.27(-0.56)(+0.42) which is consistent with the (1 + z)(-0.5) expectation from a universe in expansion. The scatter of the sAM sequence is a strong function of the dynamical state with logj vertical bar(M star) proportional to 0.65(-0.08)(+0.06) x log(V-max/sigma), where sigma is the velocity dispersion at 2R(e). In TNG50, SFGs also form a (j) over tilde (star) - M-star (V/sigma) plane, but it correlates more with galaxy size than with morphological parameters. Our results suggest that SFGs might experience a dynamical transformation, and lose their sAM, before their morphological transformation to becoming passive via either merging or secular evolution. Show less
The formation and evolution of galaxies is fundamentally driven by the formation of new stars out of cold gas. Observations of young stars in distant galaxies in the early universe, such as we can... Show moreThe formation and evolution of galaxies is fundamentally driven by the formation of new stars out of cold gas. Observations of young stars in distant galaxies in the early universe, such as we can see in the Hubble Ultra Deep Field, have unveiled how the cosmic star formation rate density evolves. Yet, while the effect of star formation—the young stars—has been mapped in ever-increasing detail, the cause—the cold molecular gas that fuels star formation—has been elusive. This thesis presents an observational study of the cold interstellar medium of distant galaxies in the early universe, using the most sensitive submillimeter telescope to date, the Atacama Large Millimeter Array, together with new integral-field spectrographs, such as the Multi Unit Spectroscopic Explorer on the Very Large Telescope. It unveils the physical properties of star-forming galaxies and their molecular gas reservoirs, and describes the evolution of the cosmic molecular gas density—the fuel for star formation. Show less
We present the first measurements of the Lyman-continuum photon production efficiency xi(ion.0) at z similar to 4-5 for galaxies fainter than 0.2 L* (-19 mag). xi(ion.0) quantifies the production... Show moreWe present the first measurements of the Lyman-continuum photon production efficiency xi(ion.0) at z similar to 4-5 for galaxies fainter than 0.2 L* (-19 mag). xi(ion.0) quantifies the production rate of ionizing photons with respect to the UV luminosity density assuming a fiducial escape fraction of zero. Extending previous measurements of xi(ion.0) to the faint population is important, as ultra-faint galaxies are expected to contribute the bulk of the ionizing emissivity. We probe xi(ion.0) to such faint magnitudes by taking advantage of 200-h depth Spitzer/IRAC observations from the GREATS program and approximate to 300 3 < z < 6 galaxies with spectroscopic redshifts from the MUSE GTO Deep + Wide programs. Stacked IRAC [3.6] [4.5] colors are derived and used to infer the H alpha rest-frame equivalent widths, which range from 403 angstrom to 2818 angstrom. The derived xi(ion.0) is log(10)(xi(ion.0)/Hz erg(-1)) = 25.36 0.08 over-20.5 < Muv <-17.5, similar to those derived for brighter galaxy samples at the same redshift and therefore suggesting that 6011 shows no strong dependence on M-UV. The xi(ion.0) values found in our sample imply that the Lyman-continuum escape fraction for M-UV approximate to-19 star-forming galaxies cannot exceed approximate to 8-20% in the reionization era. Show less
Deep optical spectroscopic surveys of galaxies provide a unique opportunity to investigate rest-frame ultra-violet (UV) emission line properties of galaxies at z similar to 2-4.5. Here we combine... Show moreDeep optical spectroscopic surveys of galaxies provide a unique opportunity to investigate rest-frame ultra-violet (UV) emission line properties of galaxies at z similar to 2-4.5. Here we combine VLT /MUSE Guaranteed Time Observations of the Hubble Deep Field South, Ultra Deep Field, COSMOS, and several quasar fields with other publicly available data from VLT /VIMOS and VLT /FORS2 to construct a catalogue of He II lambda 1640 emitters at z greater than or similar to 2. The deepest areas of our MUSE pointings reach a 3 sigma line flux limit of 3.1 x 10(19) erg s(-1) cm(-2). After discarding broad-line active galactic nuclei, we find 13 He II lambda 1640 detections from MUSE with a median M-UV = -20.1 and 21 tentative He II lambda 1640 detections from other public surveys. Excluding Ly alpha, all except two galaxies in our sample show at least one other rest-UV emission line, with C III] lambda 1907, lambda 1909 being the most prominent. We use multi-wavelength data available in the Hubble legacy fields to derive basic galaxy properties of our sample through spectral energy distribution fitting techniques. Taking advantage of the high-quality spectra obtained by MUSE (similar to 10-30 h of exposure time per pointing), we use photo-ionisation models to study the rest-UV emission line diagnostics of the He II lambda 1640 emitters. Line ratios of our sample can be reproduced by moderately sub-solar photo-ionisation models, however, we find that including effects of binary stars lead to degeneracies in most free parameters. Even after considering extra ionising photons produced by extreme sub-solar metallicity binary stellar models, photo-ionisation models are unable to reproduce rest-frame He II lambda 1640 equivalent widths (similar to 0.2-10 angstrom), thus additional mechanisms are necessary in models to match the observed He II lambda 1640 properties. Show less
