82 research outputs found
Metodología para el análisis de la evolución de los parámetros estructurales de las galaxias en función del desplazamiento al rojo
No full textEl avance de la tecnología utilizada en los telescopios de nueva generación como el James Webb Space
Telescope (JWST) ha permitido observar galaxias a una distancia nunca antes observada, abriendo la
puerta a nuevas teorías sobre la evolución de sus propiedades y morfología visual. Uno de los efectos
que intenta explicar el comportamiento de la morfología visual a grandes distancias, (desplazamiento
al rojo z > 3), es el efecto Chromatic Surface Brightness Modulation (CMOD) (Papaderos et al. 2023).
Este efecto ha sido la base teórica de este trabajo enmarcado en el objetivo principal de crear un modelo
evolutivo de los parámetros estructurales de las galaxias, como el índice de Sérsic o el radio efectivo, con
el desplazamiento al rojo. Para ello, en este trabajo se ha creado una metodología eficiente, escalable
y automática desde cero, capaz de analizar grandes cantidades de datos relativos a la evolución con el
desplazamiento al rojo de los parámetros estructurales de galaxias con diferentes morfologías visuales.
Este trabajo ha sido el primer estudio práctico que se ha llevado a cabo sobre este efecto y con el que
se han conseguido analizar unas 45000 imágenes, obteniendo unos resultados preliminares a partir de
los cuales se pretende construir una mayor muestra estadística de galaxias para poder crear un modelo
evolutivo. Además de la metodología de análisis numérico de los parámetros estructurales, se ha creado un
sistema automático de visualización de los resultados obtenidos con el objetivo de facilitar la comprensión
de los mismos así como la posibilidad de relacionarlos de una manera visual.The advance of the technology used in the new telescopes generation such as the James Webb Space
Telescope (JWST) has made it possible to observe galaxies at a distance never observed before, opening
the door to new theories about the evolution of their properties and visual morphology. One of the effects
that attempts to explain the behavior of visual morphology at large distances, (redshift z > 3), is the
Chromatic Surface Brightness Modulation (CMOD) effect (Papaderos et al. 2023). This effect has been
the theoretical basis of this work framed in the main objective of creating an evolutionary model of galaxy
structural parameters such as the Sérsic index or the effective radius with redshift. For this purpose, an
efficient, scalable and automatic methodology has been created from scratch, capable of analyzing large
amounts of data related to the redshift evolution of the galaxy structural parameters with different visual
morphologies. This work has been the first practical study that has been carried out on this effect. We
have managed to analyze about 45000 images obtaining preliminary results from which we intend to
build a larger statistical sample of galaxies in order to create the evolutionary model. In addition to the
methodology of numerical analysis of the structural parameters, an automatic system for visualization of
our results has been created in order to facilitate the understanding as well as the possibility of relating all
the concepts visually.Departamento de Física Teórica, Atómica y ÓpticaGrado en Físic
Photometric and spectroscopic tracers of the inside-out growth of massive galaxies
No full textThe most massive (Mstellar > 1011M_) galaxies of the Universe experience a dramatic evolution in their observational properties (size, morphology, kinematics, star formation rates) across cosmic time. This metamorphosis, which implies an accelerated evolution of this galaxy population in comparison with lower mass galaxies, is not well understood.
This thesis explores the structural properties and spectroscopic evolution of massive galaxies in the nearby Universe (z < 0:5) by conducting two different but complementary studies: one employing surface photometry using deep photometric data from the Hubble Space Telescope (HST), and another one exploiting spectral synthesis using state-of-the-art integral field spectroscopy (IFS) from MUSE.
The first study makes use of HST CANDELS data to analyze a sample of 17 nearby (z 1011M_) galaxies, with the aim to disentangle the structural components of these systems and study possible faint non-axissymmetric features. The excellent HST spatial resolution for intermediate redshift objects justifies a detailed structural analysis that combines two parametric components for the disk and bulge, instead of a purely automatic application of one single Sérsic model. Therefore careful single Sérsic fits and bulge-disk decompositions are performed to model the galaxy surface brightness profiles. The model color profiles are compared with the observed ones, and multi-component global effective radii are derived in order to obtain more accurate measurements of the size of galaxies and their position on the mass-size relation. It was found that the Sérsic index does not offer a good proxy for the visual morphology of our sample of massive galaxies. The derived multi-component effective radii offer a better description of the size of the sample galaxies than those inferred from single Sérsic models with GALFIT. The galaxies in our sample lie on the scatter of the local masssize relation, indicating that these massive objects have not experienced a significant growth in size since z ~ 0.5. Interestingly, the few outliers in the local mass-size relation are late-type galaxies, suggesting that spheroids must have reached the local mass-size relation earlier. For most of our sample, both single and multi-component Sérsic models retrieved with GALFIT show considerable systematic deviations from the observed surface brightness profiles in the galaxy peripheries that consequently propagate into significant uncertainties in the Sérsic fit parameters. In several cases they also indicate that colors inferred from Sersic fits show strong discrepancies from the observed colors.
The second study explores the build-up process of massive galaxies by examining IFS MUSE data. We conduct a direct comparison between the spatially resolved stellar populations of the largest galaxy known in the Universe – IC1101 – and four other nearby early-type massive galaxies (ETGs), which represent the predominant morphological massive class in the nearby Universe. The IFS data were spatially-binned using Voronoi tesselation and modeled with our in-house spectral fitting pipeline Porto3D, enabling us to study the galaxy stellar populations, and focusing on the stellar age and metallicity radial profiles and their corresponding gradients. It was found a diversity in the radial distribution of equivalent width (EW) of H α) supporting a subdivision of ETGs into two groups: type i and type ii ETGs. The ones classified as type ii ETGs show an outwardly increasing EW(H α) whereas type i show a nearly constant EW(Hα) with values being consistent with gas photoionization by post-AGB stellar populations. All but one of the analyzed galaxies show LINER-specific spectroscopic properties out to several kpc from their nucleus. Old stellar ages (above 9 Gyr) and negative radial gradients are found for all galaxies, supporting an inside-out formation scenario. Stellar metallicities are over-solar for all galaxies with only a single exception. The main difference in the comparison of IC1101 with the rest of the sample lies on its positive stellar metallicity gradient. This result is atypical for ETGs in the low-redshift Universe and may be an indication of different evolutionary mechanisms for this galaxy. We tentatively propose plausible scenarios to explain the metal-enriched periphery of IC1101, being (i) a contribution of metal-rich intra-cluster stellar
light, and (ii) a self-enrichment by “wet” mergers of accreted satellites that fed star formation.
We also conjecture that this might partly be an artifact created by the astonishing large velocity dispersion determined in the outskirts of IC1101
Pairwise Dwarf Galaxy Formation and Galaxy Downsizing: Some Clues from Extremely Metal-Poor Blue Compact Dwarf Galaxies
No full textPhotometric and spectroscopic tracers of the inside-out growth of massive galaxies
No full textThe most massive (Mstellar > 1011M_) galaxies of the Universe experience a dramatic evolution in their observational properties (size, morphology, kinematics, star formation rates) across cosmic time. This metamorphosis, which implies an accelerated evolution of this galaxy population in comparison with lower mass galaxies, is not well understood.
This thesis explores the structural properties and spectroscopic evolution of massive galaxies in the nearby Universe (z < 0:5) by conducting two different but complementary studies: one employing surface photometry using deep photometric data from the Hubble Space Telescope (HST), and another one exploiting spectral synthesis using state-of-the-art integral field spectroscopy (IFS) from MUSE.
The first study makes use of HST CANDELS data to analyze a sample of 17 nearby (z 1011M_) galaxies, with the aim to disentangle the structural components of these systems and study possible faint non-axissymmetric features. The excellent HST spatial resolution for intermediate redshift objects justifies a detailed structural analysis that combines two parametric components for the disk and bulge, instead of a purely automatic application of one single Sérsic model. Therefore careful single Sérsic fits and bulge-disk decompositions are performed to model the galaxy surface brightness profiles. The model color profiles are compared with the observed ones, and multi-component global effective radii are derived in order to obtain more accurate measurements of the size of galaxies and their position on the mass-size relation. It was found that the Sérsic index does not offer a good proxy for the visual morphology of our sample of massive galaxies. The derived multi-component effective radii offer a better description of the size of the sample galaxies than those inferred from single Sérsic models with GALFIT. The galaxies in our sample lie on the scatter of the local masssize relation, indicating that these massive objects have not experienced a significant growth in size since z ~ 0.5. Interestingly, the few outliers in the local mass-size relation are late-type galaxies, suggesting that spheroids must have reached the local mass-size relation earlier. For most of our sample, both single and multi-component Sérsic models retrieved with GALFIT show considerable systematic deviations from the observed surface brightness profiles in the galaxy peripheries that consequently propagate into significant uncertainties in the Sérsic fit parameters. In several cases they also indicate that colors inferred from Sersic fits show strong discrepancies from the observed colors.
The second study explores the build-up process of massive galaxies by examining IFS MUSE data. We conduct a direct comparison between the spatially resolved stellar populations of the largest galaxy known in the Universe – IC1101 – and four other nearby early-type massive galaxies (ETGs), which represent the predominant morphological massive class in the nearby Universe. The IFS data were spatially-binned using Voronoi tesselation and modeled with our in-house spectral fitting pipeline Porto3D, enabling us to study the galaxy stellar populations, and focusing on the stellar age and metallicity radial profiles and their corresponding gradients. It was found a diversity in the radial distribution of equivalent width (EW) of H α) supporting a subdivision of ETGs into two groups: type i and type ii ETGs. The ones classified as type ii ETGs show an outwardly increasing EW(H α) whereas type i show a nearly constant EW(Hα) with values being consistent with gas photoionization by post-AGB stellar populations. All but one of the analyzed galaxies show LINER-specific spectroscopic properties out to several kpc from their nucleus. Old stellar ages (above 9 Gyr) and negative radial gradients are found for all galaxies, supporting an inside-out formation scenario. Stellar metallicities are over-solar for all galaxies with only a single exception. The main difference in the comparison of IC1101 with the rest of the sample lies on its positive stellar metallicity gradient. This result is atypical for ETGs in the low-redshift Universe and may be an indication of different evolutionary mechanisms for this galaxy. We tentatively propose plausible scenarios to explain the metal-enriched periphery of IC1101, being (i) a contribution of metal-rich intra-cluster stellar
light, and (ii) a self-enrichment by “wet” mergers of accreted satellites that fed star formation.
We also conjecture that this might partly be an artifact created by the astonishing large velocity dispersion determined in the outskirts of IC1101
Exploring the genesis of spiral galaxies
No full textContext. A tantalizing enigma in extragalactic astronomy concerns the chronology and driving mechanisms of the build-up of late-type galaxies (LTGs). The standard scenario envisages two formation routes, with classical bulges (CBs) assembling first in a quick and violent quasi-monolithic episode followed by gradual disk assembly, and pseudo-bulges (PBs) progressively forming over gigayear-long timescales through gentle gas inflow from the disk and in situ star formation. The expectation from this antagonistic rationale is the segregation of present-day LTG bulges into two evolutionary distinct groups, which is in sharp contrast with recent observations.
Aims. The present study aims for a thorough investigation of the star formation history (SFH) of LTGs with its ultimate goal being to outline a coherent framework for the formation and evolution of spiral galaxies and their main stellar components.
Methods. Using population spectral synthesis models, we analyse the spatially resolved SFH of bulges and disks of 135 LTGs from the CALIFA survey, covering the relevant range in LTG mass. Complementarily, characteristic physical properties of bulges and disks, such as mean colours, mass- and light-weighted stellar age and metallicity, and EW(Hα), were contrasted with predictions from evolutionary synthesis models, by adopting exponentially declining SFHs with e-folding times τ between 0.1 and 20 Gyr.
Results. Analysis of the SFH of roughly half a million spaxels consistently reveals that the main physical and evolutionary properties of both bulges and disks are continuously distributed across present-day total stellar mass ℳ⋆, T. The τ in spiral galaxies with log(ℳ⋆, T) > 10 increases from the centre to the periphery, suggesting that these systems grow in an inside-out fashion. Quite importantly, the radial gradient of τ in an individual galaxy increases with increasing ℳ⋆, T, which is consistent with a high bulge-to-disk age contrast in high-mass spirals, while lower-mass LTGs display roughly the same τ throughout their entire radial extent, with intermediate mass galaxies in between. Predictions obtained through evolutionary synthesis are overall consistent with observed properties. Finally, bulges and disks of higher mass galaxies exhibit shorter formation timescales as compared to their lower mass counterparts.
Conclusions. Collectively, the obtained results evince a coherent and unified picture for the formation and evolution of LTGs, in which PBs and CBs denote extremities of a continuous mass sequence. Our findings are consistent with the framework where bulges are assembled jointly with their parent disks by gradual inside-out growth, at a pace that is regulated by the depth of the galactic potential. This postulate is further supported by the fact that the revealed correlations are entirely devoid of a bimodality, as it would be expected if CBs and PBs were to emerge from two distinct formation routes
Dust in cluster dwarf elliptical galaxies
No full textBased on single cross-scan data of the Herschel Virgo Cluster Survey, we report the first detections of dust in cluster early-type dwarf galaxies: VCC 209, VCC 781 and VCC 951. All three galaxies have dust masses M-d approximate to 10(5) - 10(6) M-circle dot and average dust temperatures approximate to 16-20 K. Since these three early-type dwarfs reside in densely crowded regions close to the center of the Virgo cluster, and several HI-detected dwarfs in the outskirts of Virgo were not detected by Herschel (implying a dust content < 10(4) M-circle dot), this might imply that dust in dwarfs is more closely related to the molecular gas, which is more centrally peaked in a galaxy's potential well and therefore, not easily removed by any stripping mechanism. We conclude that the removal of interstellar dust from these early-type dwarfs appears to be less efficient than the removal of the HI gas
Studying the Interstellar Medium of H II/BCD Galaxies Using IFU Spectroscopy
No full textWe review the results from our studies, and previous published work, on the spatially resolved physical properties of a sample of H ii/BCD galaxies, as obtained mainly from integral-field unit spectroscopy with Gemini/GMOS and VLT/VIMOS. We confirm that, within observational uncertainties, our sample galaxies show nearly spatially constant chemical abundances similar to other low-mass starburst galaxies. They also show He ii λ4686 emission with the properties being suggestive of a mix of excitation sources and with Wolf-Rayet stars being excluded as the primary ones. Finally, in this contribution, we include a list of all H ii/BCD galaxies studied thus far with integral-field unit spectroscopy
The continuous rise of bulges out of galactic disks
No full textContext. A key subject in extragalactic astronomy concerns the chronology and driving mechanisms of bulge formation in late-type galaxies (LTGs). The standard scenario distinguishes between classical bulges and pseudo-bulges (CBs and PBs, respectively), the first thought to form monolithically prior to disks and the second gradually out of disks. These two bulge formation routes obviously yield antipodal predictions on the bulge age and bulge-to-disk age contrast, both expected to be high (low) in CBs (PBs).
Aims. Our main goal is to explore whether bulges in present-day LTGs segregate into two evolutionary distinct classes, as expected from the standard scenario. Other questions motivating this study center on evolutionary relations between LTG bulges and their hosting disks, and the occurrence of accretion-powered nuclear activity as a function of bulge stellar mass ℳ⋆ and stellar surface density Σ⋆.
Methods. In this study, we have combined three techniques – surface photometry, spectral modeling of integral field spectroscopy data and suppression of stellar populations younger than an adjustable age cutoff with the code REMOVEYOUNG (ℛ𝒴) – toward a systematic analysis of the physical and evolutionary properties (e.g., ℳ⋆, Σ⋆ and mass-weighted stellar age 〈t⋆〉ℳ and metallicity 〈Z⋆〉ℳ, respectively) of a representative sample of 135 nearby (≤ 130 Mpc) LTGs from the CALIFA survey that cover a range between 108.9 M⊙ and 1011.5 M⊙ in total stellar mass ℳ⋆,T. In particular, the analysis here revolves around ⟨δμ9G⟩, a new distance- and formally extinction-independent measure of the contribution by stellar populations of age ≥ 9 Gyr to the mean r-band surface brightness of the bulge. We argue that ⟨δμ9G⟩ offers a handy semi-empirical tracer of the physical and evolutionary properties of LTG bulges and a promising means for their characterization.
Results. The essential insight from this study is that LTG bulges form over 3 dex in ℳ⋆ and more than 1 dex in Σ⋆ a tight continuous sequence of increasing ⟨δμ9G⟩ with increasing ℳ⋆, Σ⋆, 〈t⋆〉ℳ and 〈Z⋆〉ℳ. Along this continuum of physical and evolutionary properties, our sample spans a range of ~ 4 mag in ⟨δμ9G⟩: high-⟨δμ9G⟩ bulges are the oldest, densest and most massive ones (〈t⋆〉ℳ ~ 11.7 Gyr, Σ⋆ > 109 M⊙ kpc−2, ℳ⋆ ≥ 1010 M⊙), whereas the opposite is the case for low-⟨δμ9G⟩ bulges (〈t⋆〉ℳ ~ 7 Gyr) that generally reside in low-mass LTGs. Furthermore, we find that the bulge-to-disk age and metallicity contrast, as well as the bulge-to-disk mass ratio, show a positive trend with ℳ⋆,T, raising from, respectively, ~ 0 Gyr, ~ 0 dex and 0.25 to ~ 3 Gyr, ~ 0.3 dex and 0.67 across the mass range covered by our sample. Whereas gas excitation in lower-mass (≲ 109.7 M⊙) bulges is invariably dominated by star formation (SF), LINER- and Seyfert-specific emission-line ratios were exclusively documented in high-mass (≳ 1010 M⊙), high-Σ⋆ (≳ 109 M⊙ kpc−2) bulges. This is in agreement with previous work and consistent with the notion that the Eddington ratio or the black hole-to-bulge mass ratio scale with ℳ⋆. The coexistence of Seyfert and SF activity in ~20% of higher-ℳ⋆, high-Σ⋆ bulges being spectroscopically classified as Composites suggests that the onset of AGN-driven feedback does not necessarily lead to an abrupt termination of SF in LTG nuclei.
Conclusions. The continuity both in the properties of LTG bulges themselves and in their age and metallicity contrast to their parent diskssuggests that these components evolve alongside in a concurrent process that leads to a continuum of physical and evolutionary characteristics. Our results are consistent with a picture where bulge growth in LTGs is driven by a superposition of quick-early and slow-secular processes, the relative importance of which increases with ℳ⋆,T. These processes, which presumably combine in situ SF in the bulge and inward migration of material from the disk, are expected to lead to a non-homologous radial growth of Σ⋆ and a trend for an increasing Sérsic index with increasing galaxy mass.</jats:p
Bulgeless disks, dark galaxies, inverted color gradients, and other expected phenomena at higher z. The chromatic surface brightness modulation (CMOD) effect
No full textSince the k correction depends on the spectral energy distribution (SED) of a
galaxy, any high-z galaxy with a spatially non-homogeneous SED will experience
a spatially varying relative dimming or brightening in addition to the pure
distance effect. The morphology of galaxies will therefore change with z. For
instance, an early spiral galaxy observed in the V band would show a prominent
bulge at z=0, whereas, if at z=1, the V filter probes the rest-frame near-UV
where the bulge is faint and the disk relatively brighter, thus the galaxy may
appear as bulgeless. For galaxies with strong nebular emission, an additional
effect is that the shifting of strong nebular features in or out of filters
will result in a non-monotonous color evolution with z. Hence, unlike the
effects of distance, cosmological surface brightness dimming, and gravitational
lensing, which are all achromatic, the fact that most galaxies have a spatially
varying SED leads to a chromatic surface brightness modulation (CMOD) with z.
While the CMOD effects are in principle easy to grasp, they affect the
characterization of galaxies in a complex fashion. Properties such as the
bulge-to-disk ratio, Sersic exponent, effective radius, radial color gradients,
and stellar mass determinations from SED fitting will depend on z, the filters
employed, and the rest-frame 2D SED patterns in a galaxy, and will bias results
inferred on galaxy evolution across cosmic time (e.g., the evolution of the
mass-size, bulge-SMBH, and Tully-Fisher relation), if these effects are not
properly taken into account. In this article we quantify the CMOD effects for
idealized galaxies built from spectral synthesis models and from galaxies with
observed integral field spectroscopy, and we show that they are significant and
should be taken into account in studies of resolved galaxy properties and their
evolution with z. (abridged)Comment: 41 pages, 32 figures, accepted for publication in A&
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