3.16 Tesis magíster

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Characterization of the dwarf galaxy population in the Centaurus A environment
(2020) Ribbeck Valenzuela, Karen X.; Puzia, Thomas H.; Pontificia Universidad Católica de Chile. Instituto de Astrofísica
We report photometric properties of the dwarf galaxy population in the Centaurus A group, along with 51 new dwarf candidates based on the optical u’g’r’i’z’ imaging of 22 deg^2 centered on the nearby giant elliptical galaxy NGC 5128 as part of The Survey of Centaurus A’s Baryonic Structures (SCABS) program. Morphological analysis of the new candidates shows surface brightness profiles are well represented by a single component Sérsic models with an average Sérsic index of = 0.85 ± 0.05. The candidates present luminosities of -12 ≤ Mv ≤ -7 mag, corresponding to stellar masses of 7.5 ≥ log M/M☉ ≥ 4.5, which extend the size-luminosity relation toward fainter luminosities and smaller sizes for known dwarf galaxies outside the Local Group (LG), and are consistent with properties of nearby dwarf spheroidal galaxies. I will discuss the stellar population properties of the newly discovered galaxy sample and compare their properties to other dwarf galaxy samples in the nearby Universe.
Characterizing the Fe K-a line variability in a large sample of AGN
(2020) Andonie Bahamondes, Carolina Paz; Bauer, Franz Erik; Pontificia Universidad Católica de Chile. Instituto de Astrofísica
Varios Nucleos Activos de Galaxias (AGN) han mostrado variabilidad en su emisión en rayos X, en particular en el continuo entre 2-10 keV y en la línea de emisión de Hierro en 6.4 keV (Fe K-a). La línea Fe K-a es una característica obicua en el espectro de los AGN y es producida por procesos de reflección entre el continuo y la materia neutra que rodea el Agujero Negro Supermasivo (SMBH) que se encuentra en el centro del AGN. Varios estudios han constreñido la ubicación y el tamaño de las nubes reflectantes en algunos AGN estudiando la reacción de la línea a variaciones del continuo. En estre trabajo, constreñimos la relación entre la línea Fe K-a y el continuo para 19 fuentes, usando datos de los observatorios Chandra y XMM-Newton. Encontramos diferentes comportamientos, los cuales se pueden clasificar en 3 casos. Primero, en algunos AGN el flujo de la línea está dominado por nubes reflectantes ubicadas cerca de la corona de rayos X, como en el disco de acreción o la región de líneas anchas, por lo que la línea reacciona rápido frente a variaciones del continuum en las escalas de tiempo de las observaciones. Para estas fuentes, proporcionamos un límite superior para la región reflectiva. Segundo, en otros casos, la línea Fe K-a reacciona levemente frente a las variaciones del continuo, por lo que los flujos no están correlados, sugiriendo que las nubes reflectantes están localizadas mucho más lejos de la corona, como en el toro polvoriento. El último y tercer caso, son AGN que muestran variabilidad en el continuo y en la línea, pero los flujos no están correlacionados, indicando un escenario más complejo. Encontramos una leve correlación entre la relación Fe K-a-continuo y la masa del SMBH, indicando que a mayores masas las nubes reflectantes estarían ubicadas más cerca de la corona de rayos X. Para complementar los resultados espectrales, analizamos las imágenes de las observaciones de Chandra para ver si la emisión Fe K-a es extendida espacialmente. Encontramos que 14/15 fuentes analizadas son consistentes con una fuente puntual, para las cuales pudimos entregar un límite superior de la región reflectante emitiendo fotones Fe K-a, equivalente a la resolución espacial de Chandra (1.21 hasta 1419 pc).
Exploring the intersection of Lyman-U Emitters & Lyman Break Galaxies behind the strongly lensed clusters : Abell370, Abell2744 and MACS0416
(2021) Prieto Lyon, Gonzalo; Bauer, Franz Erik; Guaita, Lucía; Pontificia Universidad Católica de Chile. Instituto de Astrofísica
In this thesis, we present a study of star-forming galaxies between redshifts 2.9-6.7 split among four categories: Pure LAEs (73 galaxies) without UV detection; Pure LBGs (1015 galaxies) without Lyman-a detection; LAE-LBGs (193 galaxies), with both Lyman break and Lyman-a detected; and Other SFGs without any of these signatures (459 galaxies). We use Multi-Unit Spectroscopic Explorer (MUSE) and legacy Hubble Space Telescope (HST) data of the three Hubble Frontier Fields lensing clusters A370, A2744 and MACS0416, reaching magnitudes as faint as M1500 ≈ −13. We study the continuum and emission-line parameters of our sample, with the goal of finding and understanding any intrinsic differences between the aforementioned regimes of SFGs. We report a great diversity of high-redshift galaxies in the Lyman-a - M1500 plane, with a lack of massive galaxies above the SFR(Lya)=SFR(UV) line at M1500 < −18, with most pure LAEs near this line and log(Llya)<42.0. We measure the UV slope of pure LBGs and LAE-LBGs, with median values of ß=-1.75 and ß=-2.44 respectively, meaning that LAEs overall are near the dust-free domain while pure LBGs tend to be redder, and hence presumably more dust-obscured and/or older, the former being one of the probable reasons for their lack of Lyman-a; SFGs without LB or Lya show redder median slopes of ß=-1.59. LAE-LBGs tend to have a stronger sSFR than pure LBGs and other SFGs by a factor of 2 at every studied redshift. We find slight differences between the two LAE populations, with LAE-LBGs showing broader Lyman-a profiles, but further radiative transfer simulations are needed to clarify the contribution of HI velocity and column density.
Host galaxies of local hard X-ray selected AGN
(2022) Doll Carriel, Goran; Bauer, Franz Erik; Pontificia Universidad Católica de Chile. Instituto de Astrofísica
We investigate the evolutionary state of galaxies hosting active galactic nuclei (AGN) for a sample of 138 hard X-ray selected AGN from the BAT AGN Spectroscopic Survey (BASS) catalog and which have high-resolution (R ∼ 5000), VLT/X-SHOOTER 0.3–1 µm spectroscopy. We perform a stellar population synthesis analysis via pPXF fitting of the stellar continuum, as well as fit specific emission and absorption features (e.g., Lick indices, line ratios), to estimate AGN/star formation contributions, dust obscuration, stellar age, metallicity and star formation histories. Additionally, we perform morphological classification on our sample to study possible correlations to said evolutionary state. We compare our results to AGN X-ray properties and infrared (IR) derived SFRs to estimate the potential for AGN feedback. Using several cuts and selection criteria, we construct a comparison sample from SDSS DR7 data in the MPA-JHU catalog to place our AGN sample in the context with overall galaxy evolution. The X-SHOOTER spectra primarily probe the central regions of the AGN hosts, which tend to be dominated by old (> 10 Gyr) stellar populations. However, we find our sample primarily composed of main-sequence spirals (46%), followed by green valley spirals (14%) and green valley ellipticals (14%), with almost no galaxies present in the red sequence according to our definition. Our spectral modeling suggests that most elliptical and blue spiral hosts of AGN experienced strong episodes of star formation at intermediate ages (∼ 1–6 Gyr), which strongly correlate with their apparent morphological features (tails, remnant features). In contrast, most red spirals seem to follow a completely secular evolution. Comparison of IR and optically derived SFRs for 57 AGN in the sample implies copious obscured star formation; this appears to push otherwise optically passive elliptical hosts into the green valley or main sequence. As for the effect of AGN feedback, we only find very mild correlations between the AGN and the host bulge properties, thereby implying weak links between the current AGN event and their intermediate-age populations.
Merger tree comparison : impact on the semi-analytic model GALFORM
(2020) Gómez, Jonathan; Padilla, Nelson; Pontificia Universidad Católica de Chile. Instituto de Astrofísica
Many previous studies using semi-analytic models have focused predominantly on improving the phenomenological prescriptions of the baryonic physics governing galaxy formation as the vast uncertainties in these processes are critical in understanding the observable Universe. On the other hand, studies dedicated to "the dark universe" imply that technical issues concerning dark matter (DM) halo merger trees can also impose other uncertainties when modeling the observable universe. We examine the effect of using four different merger tree building algorithms, SUBFIND, HBT, ROCKSTAR and VELOCIraptor, on galaxy properties using the semi-analytic model of galaxy formation and evolution GALFORM with fixed model parameters, run on the EAGLE simulation in its dark matter only version. The construction of each Halo Finder causes some to be able to find some haloes that other finders do not and vice versa affecting the total number of haloes that are found. The differences in definitions or limits to distinguish the satellite and central haloes present in the Halo Finders, produce haloes which are found in two different halo catalogs with different central/satellite classification which impacts the way in which the galaxies that reside in these haloes evolve as, by construction in GALFORM, central galaxies retain their hot gas whereas satellite galaxies do not. The results of GALFORM show that the number of central and type 1 satellite galaxies (those that are hosted by a dark matter satellite subhalo) depend directly on the halo finder and its definition for central and satellite subhalo, which results in the ROCKSTAR run having a slight excess of galaxies. In contrast the number of type 2 satellite galaxies, i.e. galaxies that are not hosted by a resolved dark matter subhalo also called orphan galaxies, depends strongly on the tree builder. The number of type 2 satellite galaxies (orphans) resulting from the VELOCIraptor run is up to ∼ 2x higher than HBT, ROCKSTAR and SUBFIND, in agreement with the excess of merged dark matter satellite subhalo progenitors of VELOCIraptor; but these are only a small fraction of the galaxy population. When matching individual GALFORM galaxies in the four finders we find that the hot gas mass MHot Gas, cold gas mass MCold Gas and instantaneous star formation rates are significantly affected by the satellite and central subhalo type. When we have a central subhalo that has a satellite subhalo as its counterpart, the satellite galaxy has MHot Gas= 0 by definition and, consequently, lower MCold Gas and instantaneous SFR for MStellar< 108h −1M than the central that it is matched to, independently of the halo finder algorithm. However, when comparing matched centrals and matched satellites, their average properties agree between the outputs from the different finders. Even though the scatter can be quite high, we find that the distributions of different baryon properties do not vary significantly between the different runs, even including orphan galaxies. Overall, the run with the strongest differences in the stellar mass function is that with HBT which contains ∼ 30% less galaxies, while in the other runs the match is excellent. Another discrepancy is that GALFORM run on VELOCIraptor is accompanied by higher star formation rate density and smaller sizes. However, in all cases the amplitude of these differences is small and insufficient to make an impact on any comparison to observational properties. The reason behind the small impact of the choice of finder lies in the homogenising effect of GALFORM in the merger trees, which ensures a small uncertainty on the model results coming from the dark matter halo finding procedure.Many previous studies using semi-analytic models have focused predominantly on improving the phenomenological prescriptions of the baryonic physics governing galaxy formation as the vast uncertainties in these processes are critical in understanding the observable Universe. On the other hand, studies dedicated to "the dark universe" imply that technical issues concerning dark matter (DM) halo merger trees can also impose other uncertainties when modeling the observable universe. We examine the effect of using four different merger tree building algorithms, SUBFIND, HBT, ROCKSTAR and VELOCIraptor, on galaxy properties using the semi-analytic model of galaxy formation and evolution GALFORM with fixed model parameters, run on the EAGLE simulation in its dark matter only version. The construction of each Halo Finder causes some to be able to find some haloes that other finders do not and vice versa affecting the total number of haloes that are found. The differences in definitions or limits to distinguish the satellite and central haloes present in the Halo Finders, produce haloes which are found in two different halo catalogs with different central/satellite classification which impacts the way in which the galaxies that reside in these haloes evolve as, by construction in GALFORM, central galaxies retain their hot gas whereas satellite galaxies do not. The results of GALFORM show that the number of central and type 1 satellite galaxies (those that are hosted by a dark matter satellite subhalo) depend directly on the halo finder and its definition for central and satellite subhalo, which results in the ROCKSTAR run having a slight excess of galaxies. In contrast the number of type 2 satellite galaxies, i.e. galaxies that are not hosted by a resolved dark matter subhalo also called orphan galaxies, depends strongly on the tree builder. The number of type 2 satellite galaxies (orphans) resulting from the VELOCIraptor run is up to ∼ 2x higher than HBT, ROCKSTAR and SUBFIND, in agreement with the excess of merged dark matter satellite subhalo progenitors of VELOCIraptor; but these are only a small fraction of the galaxy population. When matching individual GALFORM galaxies in the four finders we find that the hot gas mass MHot Gas, cold gas mass MCold Gas and instantaneous star formation rates are significantly affected by the satellite and central subhalo type. When we have a central subhalo that has a satellite subhalo as its counterpart, the satellite galaxy has MHot Gas= 0 by definition and, consequently, lower MCold Gas and instantaneous SFR for MStellar< 108h −1M than the central that it is matched to, independently of the halo finder algorithm. However, when comparing matched centrals and matched satellites, their average properties agree between the outputs from the different finders. Even though the scatter can be quite high, we find that the distributions of different baryon properties do not vary significantly between the different runs, even including orphan galaxies. Overall, the run with the strongest differences in the stellar mass function is that with HBT which contains ∼ 30% less galaxies, while in the other runs the match is excellent. Another discrepancy is that GALFORM run on VELOCIraptor is accompanied by higher star formation rate density and smaller sizes. However, in all cases the amplitude of these differences is small and insufficient to make an impact on any comparison to observational properties. The reason behind the small impact of the choice of finder lies in the homogenising effect of GALFORM in the merger trees, which ensures a small uncertainty on the model results coming from the dark matter halo finding procedure.
Molecular outflows in local (U)LIRGs
(2022) Peñaloza Garrido, Fernando Felipe; Treister, Ezequiel; Pontificia Universidad Católica de Chile. Instituto de Astrofísica
Luminous infrared galaxies (LIRGs) and ultra luminous infrared galaxies (ULIRGs), defined for having L_IR > 10^11 L_⊙ and L_IR > 10^12 L_⊙ respectively, were observed in large numbers in the 1980s by the Infrared Astronomical Satellite (IRAS). Most of them are believed to form after a major merger of two similarly massive spiral galaxies and represent a key evolutionary stage, where events such as triggering of star formation and active galactic nucleus (AGN) occur, thereby deciding the fate of the galaxy. The study of (U)LIRGs and the processes taking place in them could lead to fundamental answers for understanding galaxy evolution. This thesis studies the CO(2–1) emission from a subset of the Great Observatories All-Sky LIRG Survey (GOALS), conformed by 18 local (U)LIRGs (mean z = 0.026) observed with the Atacama Compact Array (ACA), at the Atacama Large Millimeter/submillimeter Array (ALMA). The main goal was to search for high-velocity components that could indicate the presence of molecular outflows and determine their incidence in the host galaxies. This was done by modeling the data as rotating disk galaxies to separate the emission into systemic and non-systemic components and estimate their dynamical parameters (for example, escape velocities and galactic masses). Outflows with > 1% the total molecular mass were detected in 12 of the 18 sources at relatively low velocities, with only small fractions of the emission being able to escape the galactic potential. For the galaxies with stellar masses available in the literature, it was observed that they present higher star formation rates (SFRs) than those in the main sequence, although with lowering SFR for increasing M_star. Detailed analysis of mass outflow rates and AGN contributions to the bolometric luminosity support a scenario where feedback is produced mainly by stellar activity, as expected for starburst galaxies, finding that these outflows have little or no participation in the trend seen in the SFRs–M_star diagram.
The complex gaseous and stellar environments of the nearby dual active galactic nucleus Mrk 739 as unveiled by optical VLT/MUSE observations
(2021) Tubín Arenas, Dusán Mile; Treister, Ezequiel; Pontificia Universidad Católica de Chile. Instituto de Astrofísica
Dual active galactic nuclei (Dual AGN) represent a critical stage in a major galaxy merger (M/m <3), where both supermassive black holes (SMBHs) are rapidly accreting. Studying these systems can yield valuable insights into the physical processes that affect galaxy evolution, both in terms of nuclear activity and galactic collisions. In this context, we present integral field spectroscopic (IFS) observations of the nearby (z∼0.03) dual AGN Mrk 739, whose projected nuclear separation is∼3.4 kpc, obtained with the Multi Unit Spectroscopic Explorer (MUSE) at the Very Large Telescope (VLT). We find that the galaxy has an extended AGN-ionized emission-line region extending up to ∼20 kpc away from the nuclei, while star-forming regions are more centrally concentrated within 2-3 kpc. We model the kinematics of the ionized gas surrounding the eastern nucleus using a circular disk profile, resulting in a peak velocity of 237+26−28km s−1at a distance of ∼1.2 kpc. The enclosed dynamical mass within 1.2 kpc is log M(M) = 10.20±0.06, ∼1,000 times larger than the estimated supermassive black hole (SMBH) mass of Mrk739E. The morphology and dynamics of the dual AGN Mrk 739 are consistent with an early stage of the collision, where the foreground galaxy (Mrk 739W) is a young star-forming galaxy in an ongoing first passage with its background companion (Mrk739E). Since Mrk 739W’s AGN does not show evidence of being actively accreting as its companion, we claim that the gas of the northern spiral arms of Mrk 739W are cross-ionized by the nuclear activity of Mrk 739E. The subsequent MUSE Narrow Field Mode (NFM) analysis reveals an unprecedented spatial resolution for Mrk 739E, where star-forming clumps, traced by Hα emission, form a ring-like structure inside a rotating disk. These star-forming clouds are surrounding an active SMBH at the center of an elliptical galaxy undergoing a merger process with a young spiral galaxy. Kinematically, we note that the disk is rotating with a velocity of Vmed,rot= 280.5±32.7 km s−1,∼50 km s−1larger than the velocity derived from the WFM analysis. The flux distribution of the NFM data reveal Hα clouds that also belong to Mrk 739W. Based on our schematic representation of the merger process, this emission would be part of the north side of the Mrk 739W’sbar and the beginning of the leading arm that gives origin to the large-scale spiraling crest.

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