Browsing by Author "Galaz, Gaspar"

Now showing 1 - 20 of 56
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    A multi-wavelength survey of AGN in the XMM-LSS field I. Quasar selection via the KX technique
    (2009) Nakos, T.; Galaz, Gaspar; Quintana Godoy, Hernán; Nakos, T.; Galaz, Gaspar; Quintana Godoy, Hernán; Nakos, T.; Galaz, Gaspar; Quintana Godoy, Hernán
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    Accurate classification of 17 AGNs detected with Swift/BAT
    (2009) Parisi, P.; Galaz, Gaspar; Minniti, D.; Parisi, P.; Galaz, Gaspar; Minniti, D.; Parisi, P.; Galaz, Gaspar; Minniti, D.; Parisi, P.; Galaz, Gaspar; Minniti, D.
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    Accurate classification of 29 objects detected in the 39 month Palermo Swift/BAT hard X-ray catalogue
    (2012) Parisi, P.; Galaz, Gaspar; Minniti, D.; Parisi, P.; Galaz, Gaspar; Minniti, D.; Parisi, P.; Galaz, Gaspar; Minniti, D.; Parisi, P.; Galaz, Gaspar; Minniti, D.
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    Accurate classification of 75 counterparts of objects detected in the 54-month Palermo Swift/BAT hard X-ray catalogue
    (2014) Parisi, P.; Masetti, N.; Rojas, A. F.; Jiménez Bailón, E.; Chavushyan, V.; Palazzi, E.; Bassani, L.; Bazzano, A.; Bird, A. J.; Galaz, Gaspar; Minniti, D.; Morelli, L.; Ubertini, P.; Parisi, P.; Masetti, N.; Rojas, A. F.; Jiménez Bailón, E.; Chavushyan, V.; Palazzi, E.; Bassani, L.; Bazzano, A.; Bird, A. J.; Galaz, Gaspar; Minniti, D.; Morelli, L.; Ubertini, P.
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    Analysis of bulges from spectra of low surface brightness galaxies
    (2009) Lacerna Zambrano, Iván Andrés; Galaz, Gaspar; Lacerna Zambrano, Iván Andrés; Galaz, Gaspar
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    BUDDI-MaNGA II: the star-formation histories of bulges and discs of S0s
    (OXFORD UNIV PRESS, 2022) Johnston, Evelyn J.; Haussler, Boris; Jegatheesan, Keerthana; Fraser-McKelvie, Amelia; Coccato, Lodovico; Cortesi, Arianna; Jaffe, Yara; Galaz, Gaspar; Mora, Marcelo; Ordenes-Briceno, Yasna
    Many processes have been proposed to explain the quenching of star formation in spiral galaxies and their transformation into S0s. These processes affect the bulge and disc in different ways, and so by isolating the bulge and disc spectra, we can look for these characteristic signatures. In this work, we used BUDDI to cleanly extract the spectra of the bulges and discs of 78 S0 galaxies in the MaNGA Survey. We compared the luminosity and mass weighted stellar populations of the bulges and discs, finding that bulges are generally older and more metal rich than their discs. When considering the mass and environment of each galaxy, we found that the galaxy stellar mass plays a more significant role on the formation of the bulges. Bulges in galaxies with masses >= 10(10) M-circle dot built up the majority of their mass rapidly early in their lifetimes, while those in lower mass galaxies formed over more extended time-scales and more recently. No clear difference was found in the formation or quenching processes of the discs as a function of galaxy environment. We conclude that more massive S0 galaxies formed through an inside-out scenario, where the bulge formed first and evolved passively while the disc underwent a more extended period of star formation. In lower mass S0s, the bulges and discs either formed together from the same material, or through an outside-in scenario. Our results therefore imply multiple formation mechanisms for S0 galaxies, the pathway of which is chiefly determined by a galaxy's current stellar mass.
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    Bulge evolution in face-on spiral and low surface brightness galaxies
    (2006) Galaz, Gaspar; Villalobos, Alvaro; Infante Lira, Leopoldo; Donzelli, Carlos
    It is an observational fact that bulges of spiral galaxies contain a high fraction of old and metal-rich stars. Following this observational fact, we have investigated colors of 21 bulges hosted by a selected sample of high surface brightness spirals and low surface brightness galaxies observed in B and R optical bands and in J and Ks near-IR bands. Using structural parameters derived from these observations we obtain evidence that bulges could be formed by pure disk evolution (secular evolution), in agreement with the suggestion by some authors. The color profiles, especially the near-IR ones show null or almost null color gradients, supporting the hypothesis that the disk stellar populations are similar to those present in the bulge, and/or some bulges can be understood as disks with enhanced stellar density (or pseudobulges). In the optical, half of the galaxies present an inverse color gradient, giving additional evidence in favor of secular evolution for the sample investigated. The comparison of the observed colors with those obtained from spectrophotometric models of galaxy evolution suggests that bulges of the selected sample have solar and subsolar metallicity, and are independent of the current stellar formation rate. Also, we obtain evidence suggesting that galaxies hosting small bulges tend to be systematically metal poor compared to those with larger bulges. These results are being checked more carefully with high S/N spectroscopy.
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    Bulge evolution in spirals and low surface brightness galaxies
    (2005) Galaz, Gaspar; Villalobos, Alvaro; Infante Lira, Leopoldo; Donzelli, Carlos
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    Candidate Tidal Dwarf Galaxies in the Compact Group Cg J1720-67.8
    (2003) Temporin S; Galaz, Gaspar; Temporin S; Galaz, Gaspar
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    (CO)-C-12(3-2) emission in spiral galaxies: Warm molecular gas in action?
    (2008) Galaz, Gaspar; Cortés Contreras, Paulo Cesar.; Galaz, Gaspar; Cortés Contreras, Paulo Cesar.
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    Constraining age and metallicity of bulges embedded in low surface brightness galaxies
    (2005) Galaz, Gaspar; Infante Lira, Leopoldo; Galaz, Gaspar; Infante Lira, Leopoldo
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    DEEP OPTICAL IMAGES of MALIN 1 REVEAL NEW FEATURES
    (2015) Galaz, Gaspar; Milovic Fabregat, Carlos Andrés; Suc, V.; Busta, L.; Lizana, G.; Infante Lira, Leopoldo; Royo, S.; Galaz, Gaspar; Milovic Fabregat, Carlos Andrés; Suc, V.; Busta, L.; Lizana, G.; Infante Lira, Leopoldo; Royo, S.
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    Design for the First Narrowband Filter for the Dark Energy Camera: Optimizing the LAGER Survey for z ∼ 7 Galaxies
    (2019) Zheng, Zhen-Ya; Rhoads, James E.; Wang, Jun-Xian; Malhotra, Sangeeta; Walker, Alistair; Mooney, Thomas; Jiang, Chunyan; Hu, Weida; Hibon, Pascale; Jiang, Linhua; Infante, Leopoldo; Barrientos, L. Felipe; Galaz, Gaspar; Valdes, Francisco; Wester, William; Yang, Huan; Coughlin, Alicia; Harish, Santosh; Kang, Wenyong; Khostovan, Ali Ahmad; Kong, Xu; Perez, Lucia A.; Pharo, John; Wold, Isak; Zheng, XianZhong
    We present the design for the first narrowband filter, NB964, for the Dark Energy Camera (DECam), which is operated on the 4-m Blanco Telescope at the Cerro Tololo Inter-American Observatory. The NB964 filter profile is essentially defined by maximizing the power of searching for Lyman-alpha emitting galaxies (LAEs) in the epoch of reionization, with the consideration of the night sky background in the near-infrared and the DECam quantum efficiency. The NB964 filter was manufactured by Materion in 2015. It has a central wavelength of 964.2 nm and a full width at half maximum (FWHM) of 9.2 nm. An NB964 survey named Lyman Alpha Galaxies in the Epoch of Reionization (LAGER) has been ongoing since December 2015. Here, we report results of lab tests, on-site tests, and observations with the NB964 filter. The excellent performances of this filter ensure that the LAGER project is able to detect LAEs at z similar to 7 with a high efficiency.
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    Exploring the Green Valley with the dark energy survey: studying the evolution of galaxies
    (2023) Gil Toriello, Santiago; Galaz, Gaspar; Pontificia Universidad Católica de Chile. Instituto de Astrofísica
    We investigate the properties of galaxies located at the so-called Green Valley, an intermediate region between the blue-cloud of active star- forming galaxies, and the red-sequence of quenched and "dead" galaxies, visible in a color vs stellar mass diagram for galaxies.We utilize data from multiple releases of the Dark Energy Survey (DES), to characterize galaxies based on their physical properties, and to correlate their location in a stellar mass vs color diagram with their morphologies.We selected a sample of high-quality photometric data from the Year 3 re- lease of the Dark Energy Survey, with redshifts ranging from local z ∼ 0, to intermediate z ∼ 1.5, and cleaned it by applying a set of different quality selection criteria. We obtained a number of measurements for the photometric redshifts of the galaxies, by employing different parametric algorithms, to study each evolution separately as a function of distance. With the use of LePHARE, a template fitting code, we measured a set of physical properties of the galaxies that are helpful to study their evo- lution, and to assess the transitional nature of galaxies inside the Green Valley. These are, mainly, the Absolute Magnitude, the Stellar Mass, the Star Formation Rate and the UV Luminosity.We made use of two catalogues for morphological prediction available for the Year 3 release. These catalogues allowed us to better constrain the relation between the morphological structures of galaxies and their evolutionary stage.Results show that combining SED template fitting algorithms with mor- phological analysis allows to constrain the bi-modality distribution even when working with optical surveys, up to redshifts of z = 1.5.This is a first approach on the use of these methods to pave the way more massive and intensive data treatment surveys, like the future LSST survey to be done with the Vera Rubin Telescope.
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    Extended HCN and HCO+ emission in the starburst galaxy M82
    (2014) Salas, P.; Galaz, Gaspar; Salter, D.; Herrera-Camus, R.; Bolatto, A.; Kepley, A.; Salas, P.; Galaz, Gaspar; Salter, D.; Herrera-Camus, R.; Bolatto, A.; Kepley, A.
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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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    Intrinsic Morphology of Ultra-diffuse Galaxies
    (IOP PUBLISHING LTD, 2020) Rong, Yu; Dong, Xiao Yu; Puzia, Thomas H.; Galaz, Gaspar; Sanchez Janssen, Ruben; Cao, Tianwen; van der Burg, Remco F. J.; Sifon, Cristobal; Pina, Pavel E. Mancera; Marcelo, Mora; D'Ago, Giuseppe; Zhang, Hong Xin; Johnston, Evelyn J.; Eigenthaler, Paul
    With the published data of apparent axis ratios for 1109 ultra-diffuse galaxies (UDGs) located in 17 low-redshift (z similar to 0.020-0.063) galaxy clusters and 84 UDGs in two intermediate-redshift (z similar to 0.308-0.348) clusters, we take advantage of a Markov Chain Monte Carlo approach and assume a triaxial model to investigate the intrinsic morphologies of UDGs. In contrast to the conclusion of Burkert, i.e., the underlying shapes of UDGs are purely prolate (C = B < A), we find that the data favor the oblate-triaxial models (i.e., thick disks with C < B less than or similar to A) over the nearly prolate ones. We also find that the intrinsic morphologies of UDGs are related to their stellar masses/luminosities, environments, and redshifts. First, the more luminous UDGs have puffier morphologies compared with the less luminous counterparts; the UDG morphologic dependence on luminosity is distinct from that of the typical quiescent dwarf ellipticals (dEs) and dwarf spheroidals (dSphs); in this sense, UDGs may not be simply treated as an extension of the dE/dSph class with similar evolutionary histories; they may differ not only in size. Second, the UDGs with smaller clustercentric distances are more puffed up, compared with the counterparts with larger clustercentric distances; in combination with the UDG thickness dependence on luminosity, the puffier morphologies of UDGs with high luminosities or located in the denser environments are very likely to be attributed to tidal interactions with massive galaxies. Third, we find that the intermediate-redshift UDGs are more flattened, compared with the low-redshift counterparts, which plausibly suggests a "disky" origin for the high-redshift, newly born UDGs.
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    Low and high surface brightness galaxies at void walls
    (2012) Ceccarelli, L.; Galaz, Gaspar; Padilla, Nelson; Ceccarelli, L.; Galaz, Gaspar; Padilla, Nelson