Studying galaxies’ ISM and environments at high redshifts is an essential component to study galaxy evolution. With this in mind, this thesis is divided into two main projects, the first of which involves studying the ISM of a “normal”, main-sequence galaxy at z = 5.25.
High-redshift observations are often biased towards massive and bright galaxies that are not necessarily representative of the full population. In order to accurately study galaxy evolution and mass assembly at these redshifts, observations of “normal” main sequence galaxies are required. Here we present Atacama Large Millimeter/Submillimeter Array (ALMA) 0.3 arcsec resolution observations of the [C II] emission line at 158 μm of HZ7, a main sequence galaxy at z = 5.25. Comparing to archival rest-frame UV observations taken by the Hubble Space Telescope (HST), we find strong evidence of the existence of extended [C II] emission, which we estimate to be twice the size of the rest-frame UV emission, yielding one of the first high-redshift objects where a clear signature of a [C II] “Halo” has been detected to date. For a matched SÅLersic profile with n = 1, we measured a [C II] effective radius of 0.50 °æ 0.04 arcsec (3.07 °æ 0.25 kpc) and an average restframe UV effective radius of 0.2 °æ 0.04 arcsec (1.48 °æ 0.16 kpc). The [C II] morphology and kinematics of the system suggest a merging event resulting in a non-rotating disc system. This event could be responsible for the extended [CII] emission. Alternatively, some potential obscured emission could also explain the [C II] to UV size ratio. These results contribute to the growing consensus with respect to the existence of extended [C II] emission around galaxies.
The second project focuses identifying Lyman-alpha emitters around a high-redshift quasar. High-redshift quasars are thought to live in the most dense regions of space which should be made evident by an overdensity of galaxies around them. However, campaigns to identify these overdensities through the search of Lyman Break Galaxies (LBGs), with broad photometric bands, and Lyman α emitters (LAEs), with narrow photometric bands, have had mixed results. These may be explained by either the small field of view of some of the experiments, the broad redshift ranges targeted by LBG searches, and by the inherent large uncertainty of quasar redshifts estimated from UV emission lines, which makes it difficult to place the Ly-α emission line within a narrowband filter. Here we present a three square degree search (∼ 1000 pMpc) for LAEs around the z = 6.9 quasar VIK J2348–3054 using the Dark Energy CAMera (DECam), housed on the 4m Blanco telescope, finding 38. The systemic redshift of VIK J2348–3054 is known from ALMA [CII] observations and place the Ly-α emission line of companions within the NB964 narrowband of DECam. This is the largest field of view LAE search around a z > 6 quasar conducted to date. We find that this field is ∼ 10 times more overdense when compared to the Chandra Deep-Field South, observed previously with the same instrumental setup. This is strong evidence that J2348 resides
in an overdensity of LAEs over several Mpc. Surprisingly, we find a lack of LAEs within 5 pMpc of the quasar and take this to be evidence of the quasar suppressing star formation in its immediate vicinity. This result highlights the importance of performing
these kinds of overdensity searches over large areas to properly assess the density of those regions of the Universe.
(Text above corresponds to PhD thesis abstract)
Type of project: PhD thesis
Status: Finished. Graduated 2024.
Researchers: Trystan Lambert, Roberto Assef, Manuel Aravena
Funding source: ANID-Max Plank, Basal CATA2