| 1. |
- Kade, Kiana, 1998
(author)
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An ALMA perspective on high-redshift galaxy evolution
- 2022
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Licentiate thesis (other academic/artistic)abstract
- The processes governing the growth and evolution of high-redshift massive galaxies have long been a subject of intense investigations. Studies of the cosmic star-formation rate density have shown a peak at z ∼ 2 − 3, demonstrating the distinct need to understand the mechanisms by which galaxies acquired the fuel necessary to ignite such intense star formation. Galaxies are expected to transform through a number of phases leading up to and proceeding this peak. Theoretical modelling and simulations have proposed several driving mechanisms to cause these changes, including feedback from active galactic nuclei and merger activity driven by the effect of companion galaxies. However, both of these can be difficult to observe at high-redshift and studies have concluded conflicting results in the past decades. A synergy must exist between the predictions of theoretical simulations and observa- tional realities; with the increased sensitivity and capability of modern telescopes it has become possible to investigate this. Observations probing the effect of these mechanisms in the high-redshift universe have greatly improved in recent years with the advent of telescopes such as the Atacama Large submillimeter/Millimeter Array. Through observations of the environment of massive high-redshift quasars and starburst galaxies, along with detections of companion galaxies, it has become possible to begin to understand the effect these companions could have. Furthermore, signatures of outflow activity and tracers of the impact of active galactic nuclei on their host galaxy have begun to uncover the significance of feedback in high-redshift galaxies. This licentiate thesis summarizes the current understanding of massive high-redshift galaxy evolution and presents two (possibly archetypal) examples of massive high-redshift galaxies. Using deep, high-resolution observations of the far-infrared fine structure [CII] 158μm line, faint companions were found in close proximity to both the quasar BRI0952-0115 (z = 4.432) and the sumbillimeter galaxy AzTEC-3 (z = 5.3). Additionally, both BRI0952 and AzTEC-3 exhibit signatures of outflows. The results presented in Paper I provide additional evidence to the hypothesis that massive high-redshift galaxies evolve in over-dense regions and that outflow activity can have a dramatic effect on the host galaxy. Moreover, they demonstrate the necessity of conducting deeper observations necessary to detect these relatively fainter phenomena that are thought to be a crucial aspect of galaxy evolution.
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| 2. |
- Kade, Kiana, 1998, et al.
(author)
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Exploring the environment, magnetic fields, and feedback effects of massive high-redshift galaxies with [CII]
- 2023
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In: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 673
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Journal article (peer-reviewed)abstract
- Context. Massive galaxies are expected to grow through different transformative evolutionary phases. High-redshift starburst galaxies and quasars are thought to be such phases and thus provide insight into galaxy evolution. Several physical mechanisms are predicted to play an important role in driving these phases; for example, interaction with companion galaxies, active galactic nuclei feedback, and possibly magnetic fields. Aims. Our aim is to characterize the physical properties and the environment of the submillimeter galaxy AzTEC-3 at z=5.3 and the lensed quasar BRI 0952-0115 at z=4.4, and to set a limit on the polarization properties of the two sources. We intend to place these two sources in the broader context of galaxy evolution, specifically star formation and mass growth through cosmic time. Methods. We used full polarization, sub-arcsecond-resolution, ALMA band-7 observations of both BRI 0952-0115 and AzTEC-3. We detect [C II] (2P3/22P1/2) line emission towards both BRI 0952-0115 and AzTEC-3, along with companions in each field. We present an updated gravitational lensing model for BRI 0952-0115 for correction of gravitational magnification. Results. We present infrared luminosities, star-formation rates, and [C II] line to infrared luminosity ratios for each source. The [C II] emission line profile for both BRI 0952-0115 and AzTEC-3 exhibit a broad, complex morphology, indicating the possible presence of outflows. We present evidence of a -gas bridge-between AzTEC-3 and a companion source. Modified blackbody spectral energy distribution fitting is used to analyze the properties of [C II] detected companion sources in the field of both the submillimeter galaxy and the quasar. We investigated the possible role of the detected companions in outflow signatures. Using a simple dynamical mass estimate for the sources, we suggest that both systems are undergoing minor or major mergers. No polarization is detected for the [C II], placing an upper limit below that of theoretical predictions. Conclusions. Our results show that high-velocity wings are detected, indicating possible signs of massive outflows; however, the presence of companion galaxies can affect the final interpretation. Furthermore, the results provide additional evidence in support of the hypothesis that massive galaxies form in overdense regions, growing through minor or major mergers with companion sources. Finally, strong, ordered magnetic fields are unlikely to exist at the kiloparsec scale in the two studied sources.
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| 3. |
- Kade, Kiana, 1998, et al.
(author)
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Probing the interstellar medium of the quasar BRI 0952−0115 An analysis of [C ii], [C ii], CO, OH, and H 2 O
- 2024
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In: Astronomy and Astrophysics. - 0004-6361 .- 1432-0746. ; 684
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Journal article (peer-reviewed)abstract
- Context. The extent of the effect of active galactic nuclei (AGN) on their host galaxies at high-redshift is not apparent. The processes governing the co-eval evolution of the stellar mass and the mass of the central supermassive black hole, along with the effects of the supermassive black hole on the host galaxy, remain unclear. Studying this effect in the distant universe is a difficult process as the mechanisms of tracing AGN activity can often be inaccurately associated with intense star formation and vice versa. Aims. Our aim is to better understand the processes governing the interstellar medium (ISM) of the quasar BRI 0952−0952 at z = 4.432, specifically with regard to the individual heating processes at work and to place the quasar in an evolutionary context. Methods. We analyzed ALMA archival bands 3, 4, and 6 data and combined the results with high-resolution band-7 ALMA observations of the quasar. We detected [C i](2–1), [C ii](2P3/2−2P1/2), CO(5–4), CO(7–6), CO(12–11), OH 2Π1/2(3/2−1/2), and H2O(211−202), and we report a tentative detection of OH+. We updated the lensing model and we used the radiative transfer code MOLPOP-CEP to produce line emission models which we compared with our observations. Results. We used the [C i] line emission to estimate the total molecular gas mass in the quasar. We present results from the radiative transfer code MOLPOP-CEP constraining the properties of the CO emission and suggest different possible scenarios for heating mechanisms within the quasar. We extended our results from MOLPOP-CEP to the additional line species detected in the quasar to place stronger constraints on the ISM properties. Conclusions. Modeling from the CO SLED suggests that there are extreme heating mechanisms operating within the quasar in the form of star formation or AGN activity; however, with the current data, it remains unclear which of the two is the preferred mechanism as both models reasonably reproduce the observed CO line fluxes. The updated lensing model suggests a velocity gradient across the [C ii] line, suggestive of ongoing kinematical processes within the quasar. We find that the H2O emission in BRI 0952 is likely correlated with star-forming regions of the ISM. We used the molecular gas mass from [C i] to calculate a depletion time for the quasar. We conclude that BRI 0952−0952 is a quasar with a significant AGN contribution while also showing signs of extreme starburst activity, indicating that the quasar could be in a transitional phase between a starburst-dominated stage and an AGN-dominated stage.
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