Browsing by Author "Barrientos, Luis Felipe"

Now showing 1 - 20 of 66
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    A bright, spatially extended lensed galaxy at z = 1.7 behind the cluster RCS2 032727-132623
    (2010) Wuyts, E.; Barrientos, Luis Felipe; Carrasco Venegas, Mauricio Efraín.
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    A HIGHLY ELONGATED PROMINENT LENS AT z=0.87 : FIRST STRONG-LENSING ANALYSIS OF EL GORDO
    (2013) Zitrin, Adi; Menanteau, Felipe; Hughes, John P.; Coe, Dan; Barrientos, Luis Felipe; Infante Lira, Leopoldo; Mandelbaum, Rachel
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    A Measurement of Weak Lensing by Large-Scale Structure in Red-Sequence Cluster Survey Fields
    (2002) Hoekstra, H.; Barrientos, Luis Felipe; Infante Lira, Leopoldo
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    A multi-wavelength mass analysis of RCS2 J232727.6-020437, A similar to 3 x 10(15) M-circle dot galaxy cluster AT z=0.7
    (2015) Sharon, K.; Gladders, M. D.; Marrone, D. P.; Hoekstra, H.; Rasia, E.; Barrientos, Luis Felipe
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    A VLT/MUSE galaxy survey towards QSO Q1410 : looking for a WHIM traced by BLAs in inter-cluster filaments
    (2018) Pessa Gutiérrez, Ismael Alejandro; Tejos, Nicolás; Barrientos, Luis Felipe; Pontificia Universidad Católica de Chile. Instituto de Astrofísica
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    ALMA Resolves the Molecular Gas in a Young Low-metallicity Starburst Galaxy at z.=1.7
    (2017) González López, Jorge; Barrientos, Luis Felipe; Gladders, M. D.; Wuyts, Eva; Rigby, Jane; Sharon, Keren; Aravena, Manuel; Bayliss, Matthew B.; Ibar, Eduardo
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    Clustering of galaxies around quasars at z ∼4
    (2020) Garcia Vergara, Cristina Javiera; Hennawi, J. F.; Barrientos, Luis Felipe; Arrigoni Battaia, F.
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    Cosmological constraints from the Red-Sequence Cluster Survey
    (2007) Gladders, Michael; Barrientos, Luis Felipe; Infante Lira, Leopoldo
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    Depthwise convolutional neural network for multiband automatic quasars classification in ATLAS
    (2023) San Martín Jiménez, Astrid Elizabeth; Pichara Baksai, Karim Elías; Barrientos, Luis Felipe; Rojas Henríquez, Felipe Ignacio; Moya Sierralta, Cristóbal Andrés
    In recent years, the astronomical scientific community has made significant efforts to automate quasars' detection. Automatic classification of these objects is challenging since they are very distant and appear as point sources, outnumbered by other sources. Thus, performing automatic morphological classification is not straightforward; colour dimension seems better as a key concept. Previous work using machine learning tools has proposed classifiers that use features such as magnitude and colour, working only for quasar representation, which requires high-quality observational data that is not always available. Those features are computationally costly in extensive image surveys like VST ATLAS (Shanks et al. 2015). With the continuous developments in deep-learning architectures, we find a powerful tool to perform automatic classification from images, where capturing information from different bands takes relevance in this kind of approach. In this work, we developed a new quasar selection method that we hope to apply to the complete ATLAS survey in subsequent papers, where the completeness and efficiency of depthwise architecture will be compared to more standard methods such as selection on the colour-colour diagrams and machine-learning feature-based methods. This automatic quasar classification tool uses images in u, g, i, z bands available in ATLAS, heading towards new survey requirements facing the big data era. We propose a deep-learning architecture based on depthwise convolutional units that work directly with ATLAS images, reduced by the VST pipeline. Our model reaches an accuracy of 96.53 per cent with a quasar classification f1-score of 96.49 per cent, a very competitive benchmark compared to previous unscalable approaches....
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    Discovery of Local Analogs to JWST's Little Red Dots
    (2024) Lin, Ruqiu; Zheng, Zhen-Ya; Jiang, Chunyan; Yuan, Fang-Ting; Ho, Luis C.; Wang, Junxian; Jiang, Linhua; Rhoads, James E.; Malhotra, Sangeeta; Barrientos, Luis Felipe; Wold, Isak; Infante Lira, Leopoldo; Zhu, Shuairu; Ji, Xiang; Fu, Xiaodan
    Recently, the James Webb Space Telescope (JWST) has revealed a new class of high redshift (high- z , z > 4) compact galaxies which are red in the rest-frame optical and blue in the rest-frame UV as V-shaped spectral energy distributions (SEDs), referred to as “Little Red Dots” (LRDs). It is very likely that LRDs host obscured broad-line active galactic nuclei (AGNs). In the meanwhile, Green pea galaxies (GPs), which are compact dwarf galaxies at low redshift, share various similar properties with high redshift star-forming galaxies. Here we aim to find the connection between the LRDs and GPs hosting broad-line AGNs (BLGPs). With a sample of 19 BLGPs obtained from our previous work, we further identify 7 GPs with V-shaped rest-frame UV-to-optical SEDs that are likely local analogs to LRDs. These V-shaped BLGPs exhibit faint UV absolute magnitudes and sub-Eddington rates similar to those of LRDs. Three of them occupy a similar region as LRDs in the BPT diagram, suggesting they have similar ionization conditions and gas-phase metallicities to LRDs. These similarities suggest that V-shaped BLGPs can be taken as local analogs of high-redshift LRDs. In addition, most (16/19) BLGPs, including 6 V-shaped BLGPs, host over-massive black holes above the local M BH- M∗ relation, making it the first sample of galaxies hosting over-massive black holes at z < 0.4. These findings will help us learn more about the formation and co-evolution of early galaxies and black holes.
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    Dissecting a 30 kpc galactic outflow at z 1.7
    (2023) Shaban, Ahmed; Bordoloi, Rongmon; Chisholm, John; Rigby, Jane R.; Sharma, Soniya; Sharon, Keren; Tejos, Nicolas; Bayliss, Matthew B.; Barrientos, Luis Felipe; López, Sebastian; Ledoux, Cédric; Gladders, Michael G.; Florian, Michael K.
    We present the spatially resolved measurements of a cool galactic outflow in the gravitationally lensed galaxy RCS0327 at z ≈ 1.703 using VLT/MUSE IFU observations. We probe the cool outflowing gas, traced by blueshifted Mg II and Fe II absorption lines, in 15 distinct regions of the same galaxy in its image-plane. Different physical regions, 5 to 7 kpc apart within the galaxy, drive the outflows at different velocities (Vout ~ -161 to -240 km s-1), and mass outflow rates ($\dot{M}_{out} \sim$ 183 to 527 M⊙ yr-1). The outflow velocities from different regions of the same galaxy vary by 80 km s-1, which is comparable to the variation seen in a large sample of star-burst galaxies in the local Universe. Using multiply lensed images of RCS0327, we probe the same star-forming region at different spatial scales (0.5 kpc2 -- 25 kpc2), we find that outflow velocities vary between ~ -120 to -242 km s-1, and the mass outflow rates vary between ~ 37 to 254 M⊙ yr-1. The outflow momentum flux in this galaxy is ≥ 100% of the momentum flux provided by star-formation in individual regions, and outflow energy flux is ≈ 10% of the total energy flux provided by star-formation. These estimates suggest that the outflow in RCS0327 is energy driven. This work shows the importance of small scale variations of outflow properties due to the variations of local stellar properties of the host galaxy in the context of galaxy evolution....
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    Dynamical analysis of strong-lensing galaxy groups at intermediate redshift
    (2013) Muñoz Soria, Roberto; Garrido Goicovic, Felipe Andrés; Padilla, Nelson; Barrientos, Luis Felipe
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    Enhanced pixelated modeling of group and cluster scale lenses: Getting ready for Vera Rubin
    (2025) Urcelay Solís de Ovando, Felipe José; Barrientos, Luis Felipe; Jullo, Eric; Pontificia Universidad Católica de Chile. Instituto de Astrofísica
    Upcoming wide-field surveys like LSST and Euclid will uncover thousands of strong gravitational lenses, enabling statistical studies of lens properties, tracing mass distributions from galaxies to clusters, and probing cosmology. While automated modeling exists for galaxy-scale lenses, group- and cluster-scale systems remain challenging due to their complexity.We present a fast, automated method for modeling group and cluster strong lenses, optimized for LSST-like data. The approach combines a large-scale halo with subhalos defined by scaling relations and uses a third-order Taylor expansion for subhalo deflections to improve computational efficiency. The method is memory-light and scales independently of cluster richness.We validate the pipeline on 200 LSST-like simulated lenses (100 clusters, 100 groups), recovering unbiased halo parameters and accurate total masses. Performance improves when selecting lenses with bright arcs or radial features. Application to real SGAS systems yields results consistent with previous models.We discuss possible applications of this method, such as constraining the halo mass function, inner slope of clusters, and subhalo properties. We also outline the necessary extensions for modeling Euclid lenses, which require increased source complexity due to the higher resolution.
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    Evolution of the Galaxy Cluster Red Sequence from Redshift 0.2 to 1.5
    (2022) Gutiérrez Hernández, Lorena; Barrientos, Luis Felipe; Pontificia Universidad Católica de Chile. Instituto de Astrofísica
    In this thesis, we present a study of the population of early-type galaxies in 115 clusters at 0.2 < z < 1.5, imaged with the F200LP/UVIS and F110W/IR filters of the Wide Field Camera 3 on the Hubble Space Telescope. We aim to investigate the evolution of the red sequence parameters (zero-point, slope, and intrinsic scatter) in the color-magnitude plane to constrain its members’ history and epoch of star formation. To accomplish this, we carefully selected the galaxies belonging to the red sequence, dismissing all contamination from the background and late-type galaxies into the clusters. Then, we used a robust linear fitting method to obtain the red sequence parameters in the rest frame. Finally, we compared the evolution of the zero-point with that of the color in stellar population synthesis models with different metallicity, formation red-shift, and e-folding time. We find that, as the redshift increases, the zero-point moves towards blue, the slope becomes steeper, and the observed scatter increases. On the other hand, the mean color of the clusters evolves slowly and is highly similar in systems at the same redshift, located in random directions in the universe. Therefore, the change of the zero-point is in agreement with the passive evolution of early galaxies in the present cosmological scenario. At the same time, we attribute the slope evolution to archaeological downsizing in conjunction with the progressive build-up of the red sequence. Finally, we constrain the epoch and period of stellar population formation to a strip diagonally crossing the τ - zf plane.
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    First Results from the Lyman Alpha Galaxies in the Epoch of Reionization (LAGER) Survey: Cosmological Reionization at z similar to 7
    (2017) Zheng, Z. Y.; Wang, J. X.; Rhoads, J.; Infante Lira, Leopoldo; Malhotra, S.; Hu, W. D.; Walker, A. R.; Jiang, L. H.; Jiang C. Y.; Hibon, P.; Gonzalez, A.; Kong, X. U.; Zheng, X. Z.; Galaz, Gaspar; Barrientos, L. F.; Zheng, Z. Y.; Wang, J. X.; Rhoads, J.; Infante Lira, Leopoldo; Malhotra, S.; Hu, W. D.; Walker, A. R.; Jiang, L. H.; Jiang C. Y.; Hibon, P.; Gonzalez, A.; Kong, X. U.; Zheng, X. Z.; Galaz, Gaspar; Barrientos, Luis Felipe; Zheng, Z. Y.; Wang, J. X.; Rhoads, J.; Infante Lira, Leopoldo; Malhotra, S.; Hu, W. D.; Walker, A. R.; Jiang, L. H.; Jiang C. Y.; Hibon, P.; Gonzalez, A.; Kong, X. U.; Zheng, X. Z.; Galaz, Gaspar; Barrientos, Luis Felipe
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    Galaxy clusters in the line of sight to background quasars - II. Environmental effects on the sizes of baryonic halo sizes
    (2009) Padilla, Nelson; Lacerna Zambrano, Iván Andrés; Barrientos, Luis Felipe; Andrews Mancilla, Heather Elaynne.
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    GALAXY CLUSTERS IN THE LINE OF SIGHT TO BACKGROUND QUASARS. III. MULTI-OBJECT SPECTROSCOPY
    (2013) Andrews Mancilla, Heather Elaynne.; Barrientos, Luis Felipe; Padilla, Nelson; Lacerna Zambrano, Iván Andrés