B. X. Santiago
A5103985885- Stellar, planetary, and galactic studies
- Astronomy and Astrophysical Research
- Galaxies: Formation, Evolution, Phenomena
- Astrophysics and Star Formation Studies
- Gamma-ray bursts and supernovae
- Astronomical Observations and Instrumentation
- Astro and Planetary Science
- Scientific Research and Discoveries
- History and Developments in Astronomy
- Adaptive optics and wavefront sensing
- CCD and CMOS Imaging Sensors
- Atmospheric Ozone and Climate
- Radio Astronomy Observations and Technology
- Impact of Light on Environment and Health
- Historical Studies and Socio-cultural Analysis
- Satellite Image Processing and Photogrammetry
- Astrophysical Phenomena and Observations
- Psychoanalysis and Psychopathology Research
- Pulsars and Gravitational Waves Research
- French Literature and Critical Theory
- Cosmology and Gravitation Theories
- Linguistics and Discourse Analysis
- French Literature and Criticism
- Space Satellite Systems and Control
- Historical and Scientific Studies
Laboratório Interinstitucional de e-Astronomia
2011-2023
Universidade Federal do Rio Grande do Sul
2011-2023
National Center for Supercomputing Applications
2016-2021
University of Illinois Urbana-Champaign
2016
Fermi National Accelerator Laboratory
2016
University of Lisbon
2009-2011
Institute of Astronomy
1996-1999
University of Cambridge
1996-1998
California Institute of Technology
1992
National Observatory
1990
The morphological properties of galaxies between $21 {\rm~mag} < I 25 {\rm~mag}$ in the {\em Hubble Deep Field} are investigated using a quantitative classification system based on measurements central concentration and asymmetry galaxian light. class distribution objects is strongly skewed towards highly asymmetric objects, relative to distributions from both HST Medium Survey} at $I 22 an artificially redshifted sample local galaxies. steeply rising number count-magnitude relation for...
Using the example of tidal stream Milky Way globular cluster Palomar 5 (Pal 5), we demonstrate how observational data on streams can be efficiently reduced in dimensionality and modeled a Bayesian framework. Our approach combines detection overdensities by Difference-of-Gaussians process with fast streakline models, continuous likelihood function built from these inference MCMC. By generating $\approx10^7$ model streams, show that geometry Pal debris yields powerful constraints solar...
view Abstract Citations (334) References (30) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS The Morphologies of Distant Galaxies. II. Classifications from the Hubble Space Telescope Medium Deep Survey Abraham, Roberto G. ; van den Bergh, Sidney Glazebrook, Karl Ellis, Richard S. Santiago, Basilio X. Surma, Peter Griffiths, E. morphological properties high-redshift galaxies are investigated using a sample 507 objects (I < 22.0 mag) (HST) Survey. Independent...
We present a catalog of morphological and color data for galaxies with 21 <I_814_ < 25 mag in the Hubble Deep Field (Williams et al. 1996). Galaxies have been inspected (when possible) independently visually classified on MDS DDO systems. Measurements central concentration asymmetry are also included catalog. The fraction interacting merging objects is seen to be significantly higher than it among nearby galaxies. Barred spirals essentially absent from deep sample. early-type similar...
We present results from a study of the photometric redshift performance Dark Energy Survey (DES), using early data Science Verification period observations in late 2012 and 2013 that provided science-quality images for almost 200 sq. deg. at nominal depth survey. assess (photo-z) about 15 000 galaxies with spectroscopic redshifts available other surveys. These are used, different configurations, as calibration sample, photo-z's obtained studied most existing photo-z codes. A weighting method...
We report the discovery of 13 confirmed two-image quasar lenses from a systematic search for gravitationally lensed quasars in SDSS-III Baryon Oscillation Spectroscopic Survey (BOSS). adopted methodology similar to that used SDSS Quasar Lens Search (SQLS). In addition lenses, we 11 pairs with small angular separations ( ≲ 2 arcsec) our spectroscopy, which are either projected pairs, physical binaries, or possibly lens systems whose galaxies have not yet been detected. The newly discovered...
We present the discovery and preliminary characterization of a gravitationally lensed quasar with source redshift $z_{s}=2.74$ image separation $2.9"$ by foreground $z_{l}=0.40$ elliptical galaxy. Since images quasars are superposition multiple point sources lensing galaxy, we have developed morphology independent multi-wavelength approach to photometric selection candidates based on Gaussian Mixture Models (GMM) supervised machine learning. Using this technique $gi$ multicolour observations...
We use the open clusters (OCs) with known parameters available in WEBDA database and recently published papers to derive properties related disk structure such as thin-disk scale height, displacement of Sun above Galactic plane, length OC age-distribution function. The sample totals 654 OCs, consisting basically Trumpler types I III whose spatial distribution traces out local geometry Galaxy. find that population OCs ages younger than 200 Myr distributes following an exponential-decay...
We measure the weak lensing masses and galaxy distributions of four massive clusters observed during Science Verification phase Dark Energy Survey (DES). This pathfinder study is meant to (1) validate Camera (DECam) imager for task measuring shapes, (2) utilize DECam's large field view map out their environments over 90 arcmin. conduct a series rigorous tests on astrometry, photometry, image quality, point spread function (PSF) modelling, shear measurement accuracy single flaws in data also...
We address the problem of separating stars from galaxies in future large photometric surveys. focus our analysis on simulations Dark Energy Survey (DES). In first part paper, we derive science requirements star/galaxy separation, for measurement cosmological parameters with gravitational weak lensing and large-scale structure probes. These are dictated by need to control both statistical systematic errors parameters, point spread function calibration. formulate terms completeness purity...
We present DES13S2cmm, the first spectroscopically-confirmed superluminous supernova (SLSN) from Dark Energy Survey (DES). briefly discuss data and search algorithm used to find this event in year of DES operations, outline spectroscopic obtained European Southern Observatory (ESO) Very Large Telescope confirm its redshift (z = 0.663 +/- 0.001 based on host-galaxy emission lines) likely spectral type (type I). Using redshift, we M_U_peak -21.05 +0.10 -0.09 for peak, rest-frame U-band...
We report on the discovery of a new Milky Way companion stellar system located at (RA, Dec) = (22h10m43.15s, +14:56:58.8). The was made using eighth data release SDSS after applying an automated method to search for overdensities in Baryon Oscillation Spectroscopic Survey footprint. Follow-up observations were performed CFHT-MegaCam, which reveal that this is comprised old population, distance 31.9+1.0-1.6 kpc, with half-light radius r_h 7.24+1.94-1.29 pc and concentration parameter c 1.55....
We measure the projected number density profiles of galaxies and splashback feature in clusters selected by Sunyaev--Zeldovich (SZ) effect from Advanced Atacama Cosmology Telescope (AdvACT) survey using observed Dark Energy Survey (DES). The radius for complete galaxy sample is consistent with theoretical measurements CDM-only simulations, located at $2.4^{+0.3}_{-0.4}$ Mpc $h^{-1}$. split based on color find significant differences profile shapes. Red those green valley show a...
We study the clustering of galaxies in real and redshift space using Optical Redshift Survey (ORS). estimate two point correlation function space, $\xi(s)$, for several subsamples ORS, spanning nearly a factor 30 volume detect significant variations $\xi(s)$ among covering small volumes. For volumes \gtsima $(75 h^{-1} {\rm Mpc})^{3}$ ORS present very similar patterns. Powerlaw fits to give best-fit values range $1.5 \leq \gamma_{s} 1.7 $ $6.5 s_{0} 8.8 h^{-1}$ Mpc samples extending...
We have analyzed new and previously published radial velocity (RV) observations of MARVELS-1, known to an ostensibly substellar companion in a ∼6 day orbit. find significant (∼100 m s−1) residuals the best-fit model for companion, these are naïvely consistent with interior giant planet P = 1.965 days nearly perfect 3:1 period commensurability (|Pb/Pc − 3| < 10−4). performed several tests reality such including dynamical analysis, search photometric variability, hunt contaminating stellar...
Planet searches using the radial velocity technique show a paucity of companions to solar-type stars within ~5 AU in mass range ~10 - 80 M$_{\text{Jup}}$. This deficit, known as brown dwarf desert, currently has no conclusive explanation. New substellar this region help asses reality desert and provide insight formation evolution these objects. Here we present 10 new two low-mass stellar companion candidates around from Multi-object APO Radial-Velocity Exoplanet Large-Area Survey (MARVELS)...
We report the characterization of first 62 Mapping Nearby Galaxies at Apache Point Observatory active galactic nuclei (AGNs) hosts and definition a control sample non-active galaxies. This was selected in order to match AGN terms stellar mass, redshift, visual morphology inclination. The masses are range |$9.4<\mbox{log}\left(\mathrm{{M}/M}_{\odot }\right)<11.5$|, most objects have redshifts ≤0.08. is mostly comprised low-luminosity AGN, with only 17 'strong AGN' |$L(\rm {[O\, \small...
We report the discovery of a stellar overdensity 8° north centre Small Magellanic Cloud (SMC; Northern Over-Density; SMCNOD), using data from first 2 yr Dark Energy Survey (DES) and year MAGellanic SatelLITEs (MagLiteS). The SMCNOD is indistinguishable in age, metallicity distance nearby SMC stars, being primarily composed intermediate-age stars (6 Gyr, Z=0.001), with small fraction young (1 Z=0.01). has an elongated shape ellipticity 0.6 size ∼ 6° × 2°. It absolute magnitude MV ≅ −7.7, rh =...
We perform a search for galaxy-galaxy strong lens systems using convolutional neural network (CNN) applied to imaging data from the first public release of DECam Local Volume Exploration Survey (DELVE), which contains $\sim 520$ million astronomical sources covering 4,000$ $\mathrm{deg}^2$ southern sky $5\sigma$ point-source depth $g=24.3$, $r=23.9$, $i=23.3$, and $z=22.8$ mag. Following methodology similar searches data, we apply color magnitude cuts select catalog 11$ extended sources....
Aims.We analyzed HST/WFPC2 colour–magnitude diagrams (CMDs) of 15 populous Large Magellanic Cloud (LMC) stellar clusters with ages between ~0.3 Gyr and ~3 Gyr. These (V, ) CMDs are photometrically homogeneous typically reach . Accurate self-consistent physical parameters (age, metallicity, distance modulus reddening) were extracted for each cluster by comparing the observed synthetic ones.
The Dark Energy Camera has captured a large set of images as part Science Verification (SV) for the Survey. SV footprint covers lar ge portion outer Large Magellanic Cloud (LMC), providing photometry 1.5 magnitudes fainter than main sequence turn-off oldest LMC stel population. We derive geometrical and structural parameters various stellar populations in disk. For distribution all stars, we find an inclination $i=-38.14^{\circ}\pm0.08^{\circ}$ (near side North) position angle line nodes...
In the last few decades, many efforts have been made to understand effect of spiral arms on gas and stellar dynamics in Milky Way disc. One fundamental parameters structure is its angular velocity, or pattern speed Ωp, which determines location resonances disc spirals' radial extent. The most direct method for estimating relies backward integration techniques, trying locate birthplace open clusters. Here, we propose a new based interaction between stars Using sample around 500 clusters from...
The distribution of core radii rich clusters in the Large Magellanic Cloud (LMC) systematically increases both upper limit and spread with increasing cluster age. Cluster-to-cluster variations stellar initial mass function (IMF) have been suggested as an explanation. We discuss implications observed degree segregation our sample for shape function. Our results are based on Hubble Space Telescope/WFPC2 observations six star LMC, selected to include three pairs similar age, metallicity...