Browsing by Author "Lira, Paulina"

Now showing 1 - 14 of 14
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    Alert Classification for the ALeRCE Broker System: The Anomaly Detector
    (IOP Publishing Ltd, 2023) Pérez-Carrasco, Manuel; Cabrera-Vives, Guillermo; Hernández-García, Lorena; Forster, F.; Sanchez-Saez, Paula; Muñoz Arancibia, Alejandra M.; Arredondo, Javier; Astorga, Nicolas; Bauer, Franz Erik; Bayo, Amelia; Catelan, Marcio; Dastidar, Raya; Estevez, P. A.; Lira, Paulina; Pignata, Giuliano
    Astronomical broker systems, such as Automatic Learning for the Rapid Classification of Events (ALeRCE), are currently analyzing hundreds of thousands of alerts per night, opening up an opportunity to automatically detect anomalous unknown sources. In this work, we present the ALeRCE anomaly detector, composed of three outlier detection algorithms that aim to find transient, periodic, and stochastic anomalous sources within the Zwicky Transient Facility data stream. Our experimental framework consists of cross-validating six anomaly detection algorithms for each of these three classes using the ALeRCE light-curve features. Following the ALeRCE taxonomy, we consider four transient subclasses, five stochastic subclasses, and six periodic subclasses. We evaluate each algorithm by considering each subclass as the anomaly class. For transient and periodic sources the best performance is obtained by a modified version of the deep support vector data description neural network, while for stochastic sources the best results are obtained by calculating the reconstruction error of an autoencoder neural network. Including a visual inspection step for the 10 most promising candidates for each of the 15 ALeRCE subclasses, we detect 31 bogus candidates (i.e., those with photometry or processing issues) and seven potential astrophysical outliers that require follow-up observations for further analysis.
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    Clustering of Intermediate-Luminosity X-Ray-Selected Active Galactic Nuclei at z ~ 3.
    (2008) Francke Henríquez, Harold Johanns Phillippe; Treister, Ezequiel; Gawiser, Eric.; Lira, Paulina; Virani, Shanil; Cardamone, Carie; Urry, C. M.; van Dokkum, Pieter; Quadri, R.
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    Heavily Obscured AGN in Star-Forming Galaxies at z ≃ 2
    (2009) Treister, Ezequiel; Cardamone, Carolin N.; Schawinski, Kevin; Urry, C. Meg; Gawiser, Eric; Virani, Shanil; Lira, Paulina; Kartaltepe, Jeyhan; Damen, Maaike; Taylor, E.N.; Le Floc'H e; Justham, Stephen; Koekemoer, Anton M.
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    Lyα emission-line galaxies at z=3.1 in the extended Chandra Deep Field-South
    (2007) Gronwall, Caryl; Ciardullo, Robin; Hickey, Thomas; Gawiser, Eric; Feldmeier, John J.; van Dokkum, Pieter G.; Urry, C. Megan; Herrera, David; Lehmer, Bret D.; Infante, Leopoldo; Orsi, Alvaro; Marchesini, Danilo; Blanc, Guillermo A.; Francke, Harold; Lira, Paulina; Treister, Ezequiel
    We describe the results of an extremely deep, 0.28 deg(2) survey for z = 3.1 Ly alpha emission-line galaxies in the Extended Chandra Deep Field-South. By using a narrowband 5000 angstrom filter and complementary broadband photometry from the MUSYC survey, we identify a statistically complete sample of 162 galaxies with monochromatic fluxes brighter than 1.5 x10(-17) ergs cm(-2) s(-1) and observer's frame equivalent widths greater than 80 angstrom. We show that the equivalent width distribution of these objects follows an exponential with a rest-frame scale length of w(0) = 76(-8)(+11) angstrom In addition, we show that in the emission line, the luminosity function of Ly alpha galaxies has a faint-end power-law slope of -1.49(-0.34)(+0.45) a bright-end cutoff of log L-* = 42.64(-0.15)(,)(+0.26) and a space density above our detection thresholds of (1.46 +/- 0.12); 10(-3) h(70)(3) galaxies Mpc(-3). Finally, by comparing the emission-line and continuum properties of the Ly alpha emitters, we show that the star formation rates derived from Ly alpha are similar to 3 times lower than those inferred from the rest-frame UV continuum. We use this offset to deduce the existence of a small amount of internal extinction within the host galaxies. This extinction, coupled with the lack of extremely high equivalent width emitters, argues that these galaxies are not primordial Population III objects, although they are young and relatively chemically unevolved.
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    Lyα emitting Galaxies at z = 2.1 : Stellar Masses, Dust, and Star Formation Histories from Spectral Energy Distribution Fitting.
    (2011) Guaita, Lucía; Padilla, Nelson; Treister, Ezequiel; Acquaviva, Viviana; Gawiser, Eric; Bond, Nicholas A.; Ciardullo, Robin; Kurczynski, Peter; Gronwall, Caryl; Lira, Paulina; Schawinski, Kevin
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    Lyα-emitting galaxies at z=3.1
    (2007) Gawiser, Eric; Francke, Harold; Lai, Kamson; Schawinski, Kevin; Gronwall, Caryl; Ciardullo, Robin; Quadri, Ryan; Orsi, Alvaro; Barrientos, Felipe; Blanc, Guillermo A.; Fazio, Giovanni; Feldmeier, John J.; Huang, Jia-Sheng; Infante, Leopoldo; Lira, Paulina; Padilla, Nelson; Taylor, Edward N.; Treister, Ezequiel; Urry, C. Megan; Van Dokkum, Pieter G.; Virani, Shanil N.
    We studied the clustering properties and multiwavelength spectral energy distributions of a complete sample of 162 Ly alpha- emitting (LAE) galaxies at z similar or equal to 3: 1 discovered in deep narrowband MUSYC imaging of the Extended Chandra Deep Field-South. LAEs were selected to have observed frame equivalent widths >80 angstrom and emission line fluxes >1.5 x 10(-17) ergs cm(-2) s(-1). Only 1% of our LAE sample appears to host AGNs. The LAEs exhibit a moderate spatial correlation length of r(0) = 3.6(-1.0)(+0.8) Mpc, corresponding to a bias factor b = 1.7(-0.4)(+0.3), which implies median dark matter halo masses of log(10)M(med) = 10.9(-0.9)(+0.5) M-circle dot. Comparing the number density of LAEs, 1.5 +/- 0.3 x 10(-3) Mpc(-3), with the number density of these halos finds a mean halo occupation similar to 1%-10%. The evolution of galaxy bias with redshift implies that most z 3: 1 LAEs evolve into present-day galaxies with L < 2.5L*, whereas other z > 3 galaxy populations typically evolve into more massive galaxies. Halo merger trees show that z 0 descendants occupy halos with a wide range of masses, with a median descendant mass close to that of L*. Only 30% of LAEs have sufficient stellar mass (>similar to 3 x 10(9) M-circle dot) to yield detections in deep Spitzer IRAC imaging. A two-population SED fit to the stacked UBVRIzJK+[3.6, 4.5, 5.6, 8.0] mu m fluxes of the IRAC-undetected objects finds that the typical LAE has low stellar mass (1.0(-0.4)(+0.6) 10(9) M-circle dot), moderate star formation rate (2 +/- 1 M-circle dot yr(-1)), a young component age of 20(-10)(+30) Myr, and little dust (A(V) < 0: 2). The bestfit model has 20% of the mass in the young stellar component, but models without evolved stars are also allowed.
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    Mid-Infrared Properties and Color Selection for X-Ray-Detected Active Galactic Nuclei in the MUSYC Extended Chandra Deep Field-South.
    (2008) Cardamone, Carolin N.; Treister, Ezequiel; Urry, C. Meg; Damen, Maaike; van Dokkum, Pieter; Labbé, Ivo; Virani, Shanil N.; Lira, Paulina; Gawiser, Eric
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    Optical Spectroscopy of X-Ray Sources in the Extended Chandra Deep Field South
    (2009) Treister, Ezequiel; Virani, Shanil; Gawiser, Eric.; Urry, C. Megan; Lira, Paulina; Francke Henríquez, Harold Johanns Phillippe; Blanc, Guillermo; Cardamone, Carolin N.; Damen, Maaike; Taylor, Edward N.; Schawinski, Kevin
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    The dust covering factor in active galactic nuclei
    (2016) Stalevski, Marko; Ricci, Claudio; Ueda, Yoshihiro; Lira, Paulina; Fritz, Jacopo; Baes, Maarten
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    The Hunt for Red Quasars: Luminous Obscured Black Hole Growth Unveiled in the Stripe 82 X-Ray Survey
    (2017) LaMassa, Stephanie M.; Lira, Paulina; Treister, Ezequiel; Glikman, Eilat; Brusa, Marcella; Rigby, Jane R.; Ananna, Tonima; Stern, Daniel.; Urry, C. Megan; Salvato, M.; Alexandroff, Rachael
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    The Multiwavelength Survey by Yale-Chile (MUSYC)
    (2008) Blanc, Guillermo A.; Lira, Paulina; Barrientos, L. Felipe; Aguirre, Paula; Francke, Harold; Taylor, Edward N.; Quadri, Ryan; Marchesini, Danilo; Infante, Leopoldo; Gawiser, Eric; Hall, Patrick B.; Willis, Jon P.; Herrera, David; Maza, Jose
    We present K-band imaging of two similar to 30' x 30' fields covered by the Multiwavelength Survey by Yale-Chile (MUSYC) Wide NIR Survey. The SDSS 1030+05 and Cast 1255 fields were imaged with the Infrared Side Port Imager (ISPI) on the 4 m Blanco telescope at the Cerro Tololo Inter-American Observatory (CTIO) to a 5 sigma point-source limiting depth of K similar to 20 (Vega). Combining these data with the MUSYC optical UBVRIz imaging, we created multiband K-selected source catalogs for both fields. These catalogs, together with the MUSYC K-band catalog of the Extended Chandra Deep Field South (ECDF-S) field, were used to select K 20 BzK galaxies over an area of 0.71 deg(2). This is the largest area ever surveyed for BzK galaxies. We present number counts, redshift distributions, and stellar masses for our sample of 3261 BzK galaxies (2502 star-forming [sBzK] and 759 passively evolving [pBzK]), as well as reddening and star formation rate estimates for the star-forming BzK systems. We also present two-point angular correlation functions and spatial correlation lengths for both sBzK and pBzK galaxies and show that previous estimates of the correlation function of these galaxies were affected by cosmic variance due to the small areas surveyed. We have measured correlation lengths r(0) of 8.89 +/- 2.03 and 10.82 +/- 1.72 Mpc for sBzK and pBzK galaxies, respectively. This is the first reported measurement of the spatial correlation function of passive BzK galaxies. In the Lambda CDM scenario of galaxy formation, these correlation lengths at z similar to 2 translate into minimum masses of similar to 4 x 10(12) and similar to 9 x 10(12) M-circle dot for the dark matter halos hosting sBzK and pBzK galaxies, respectively. The clustering properties of the galaxies in our sample are consistent with their being the descendants of bright Lyman break galaxies at z similar to 3, and the progenitors of present-day > 1L* galaxies.
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    The Multiwavelength Survey by Yale-Chile (MUSYC): Wide K-Band Imaging, Photometric Catalogs, Clustering, and Physical Properties of Galaxies at z ~ 2
    (2008) Blanc, Guillermo A.; Lira, Paulina; Barrientos, L. Felipe; Aguirre, Paula; Francke, Harold; Taylor, Edward N.; Quadri, Ryan; Marchesini, Danilo; Infante, Leopoldo; Gawiser, Eric; Hall, Patrick B.; Willis, Jon P.; Herrera, David; Maza, José; MUSYC Collaboration
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    The Physical Nature of Lyα-emitting Galaxies at z = 3.1
    (2006) Gawiser, Eric.; Blanc, Guillermo; Francke Henríquez, Harold Johanns Phillippe; Infante Lira, Leopoldo; Lira, Paulina; Treister, Ezequiel; van Dokkum, Pieter G.; Gronwall, Caryl; Ciardullo, R.; Castander, Francisco J.; Feldmeier, John J.; Franx, Marijn
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    The QUEST–La Silla AGN Variability Survey
    (2015) Cartier, Régis; Lira, Paulina; Coppi, Paolo; Sánchez, Paula; Arévalo, Patricia; Bauer, Franz Erik; Rabinowitz, David; Zinn, Robert; Muñoz, Ricardo R.; Meza, Nicolás