A5041118443- Stellar, planetary, and galactic studies
- Astronomy and Astrophysical Research
- Galaxies: Formation, Evolution, Phenomena
- Astrophysics and Star Formation Studies
- Astronomical Observations and Instrumentation
- Gamma-ray bursts and supernovae
- Adaptive optics and wavefront sensing
- Astro and Planetary Science
- Historical Studies on Spain
- SAS software applications and methods
- Historical Astronomy and Related Studies
- Historical Art and Architecture Studies
- Astrophysics and Cosmic Phenomena
- Historical and Architectural Studies
- Calibration and Measurement Techniques
- Astronomical and nuclear sciences
Instituto de Astrofísica de Canarias
2008-2015
Universidad de La Laguna
2010-2015
Institute of Applied Astronomy
2000-2013
California Institute of Technology
2004-2005
St Petersburg University
1997-2005
University of Pittsburgh
2001-2004
Israel Cancer Association USA
1999
We use deep HST/ACS observations to calculate the star formation history (SFH) of Cetus dwarf spheroidal (dSph) galaxy. Our photometry reaches below oldest main-sequence turnoffs, which allows us estimate age and duration main episode in Cetus. This is well approximated by a single that peaked roughly 12 ± 0.5 Gyr ago lasted no longer than about 1.9 (FWHM). solution also suggests essentially stars formed during past 8 Gyr. makes Cetus' SFH comparable Milky Way dSphs. Given current isolation...
We discuss how knowledge of the whole evolutionary history dwarf galaxies, including details on early star formation events, can provide insight origin different galaxy types. suggest that these types may be imprinted by conditions rather than being only result a recent morphological transformation driven environmental effects. present precise histories sample Local Group derived from colour-magnitude diagrams reaching oldest main-sequence turnoffs. argue galaxies assigned to two basic...
We present a detailed study of the star formation history (SFH) Tucana dwarf spheroidal galaxy. High quality, deep HST/ACS data, allowed us to obtain deepest color-magnitude diagram date, reaching old main sequence turnoff (F814 ~ 29) with good photometric accuracy. Our analysis, based on three different SFH codes, shows that is an and metal-poor stellar system, which experienced strong initial burst at very early epoch (~ 13 Gyr ago) lasted maximum 1 (sigma value). are not able...
(abridged) We present the first study of variable star populations in isolated dwarf spheroidal galaxies (dSph) Cetus and Tucana. Based on Hubble Space Telescope images obtained with Advanced Camera for Surveys F475W F814W bands, we identified 180 371 variables Tucana, respectively. The vast majority are RR Lyrae stars. In also found three anomalous Cepheids, four candidate binaries one long-period (LPV), while six Cepheids seven LPV candidates were Of stars, 147 as fundamental mode (RRab)...
(Abridged) We present the results of a new search for variable stars in Local Group (LG) isolated dwarf galaxy IC1613, based on 24 orbits F475W and F814W photometry from ACS camera onboard HST. detected 259 candidate variables this field, which only 13 (all them bright Cepheids) were previously known. Out confirmed variables, we found 90 RR Lyrae stars, 49 classical Cepheids (including 36 discoveries), 38 eclipsing binary could determine period. The include 61 fundamental (RRab)...
We present the results of a new search for variable stars in Local Group dwarf galaxy Leo A, based on deep photometry from Advanced Camera Surveys onboard Hubble Space Telescope. detected 166 bona fide variables our field, which about 60 percent are discoveries, and 33 candidate variables. Of confirmed variables, we found 156 Cepheids, but only 10 RR Lyrae despite nearly 100 completeness at magnitude horizontal branch. The include 7 fundamental 3 first-overtone pulsators, with mean periods...
We determine and examine the star formation rates of 50 well-known, local blue compact dwarf (BCD) galaxies based on their 1.4 GHz 60 μm luminosities. find that in cases for which both radio far-infrared luminosities are available, resulting agree extremely well with one another. BCD our sample span nearly 5 orders magnitude, from approximately a few times 10-3 to several 101 M⊙ yr-1, median SFR about 0.3 yr-1. discuss trends metallicity (primarily oxygen abundance) rate explore connections...
We present photometry of the brightest stars in six nearby spiral and irregular galaxies with corrected radial velocities from 340 to 460 km s-1. Three them are resolved into for first time. Based on luminosity blue we estimate following distances galaxies: 5.0 Mpc NGC 784, 9.2 2683, 8.9 2903, 4.1 5204, 6.8 5474, 8.7 5585.
We report the results of near-IR imaging in J and H, I Zw 36 (≈Z⊙/14) with Hubble Space Telescope. Whereas pre-COSTAR Faint Object Camera (FOC) previously resolved hot massive stars near-UV, NICMOS data furnish a census cool, intermediate- low-mass stars. There clearly was star formation prior to activity which earned it its blue compact dwarf/Wolf-Rayet galaxy classification. The detection luminous, asymptotic giant branch requires that formed vigorously several hundred megayears ago....
By using images from the HST/WFPC2/ACS archive, we have analyzed spatial distribution of AGB and RGB stars along galactocentric radius nearby spiral galaxies M 81, NGC 300 55. Examining color–magnitude diagrams stellar luminosity functions, gauge contents surroundings three galaxies. The red giant population (RGB) identified at large radii yields a distance Mpc for 55, 300, mean metallicity -0.65, -1.25, -0.87 respectively. We find that there are two number density gradients radius, which...
We present a study of the radial distribution RR Lyrae variables, which range photometric and pulsational properties, in dwarf spheroidal galaxy Tucana. find that fainter stars, having shorter period, are more centrally concentrated than luminous, longer period variables. Through comparison with predictions theoretical models stellar evolution pulsation, we interpret stars as metal-rich subsample. In addition, show they must be older about 10 Gyr. Therefore, metallicity gradient have...
We investigate the variable star content of isolated, Local Group, dwarf spheroidal galaxy (dSph) Cetus. Multi-epoch, wide-field images collected with VLT/VIMOS camera allowed us to detect 638 stars (630 RR Lyrae and 8 Anomalous Cepheids), 475 which are new detections. present a full catalogue periods, amplitudes, mean magnitudes. Motivated by recent discovery that pulsational properties in Tucana dSph revealed presence metallicity gradient within oldest (>10 Gyr old) stellar populations, we...
In this paper, we present the initial characterization of extragalactic 24 μm sources in Spitzer First Look Survey by examining their counterparts at 8 and R bands. The color-color diagram 24/8 versus 24/0.7 is populated with 18,734 brighter than 3 σ flux limit 110 μJy. data cover a total area 3.7 deg2. colors these span almost 4 orders magnitudes, while are distributed over least 2 magnitude. addition to identifying ∼30% sample infrared-quiescent, mostly low-redshift galaxies, also found...
We present deep and accurate optical photometry of the Local Group starburst galaxy IC 10. The is based on two sets images collected with Advanced Camera for Surveys Wide Field Planetary 2 board Hubble Space Telescope. provide new estimates tip red giant branch (TRGB) magnitude, = 21.90 ± 0.03, reddening, E(B − V) 0.78 0.06, using field stars in Small Magellanic Cloud (SMC) as a reference. Adopting SMC globulars, ω Cen 47 Tuc, references we estimate distance modulus to 10: independent...
We present the results of a detailed optical and near-IR study nearby star-forming dwarf galaxy NGC4214. discuss stellar content, drawing particular attention to intermediate-age and/or old field stars, which are used as distance indicator. On images obtained with Hubble Space Telescope WFPC2 NICMOS instruments in equivalents V, R, I, J H bands, is well resolved into stars. achieve limiting magnitudes F814W ~27 WF chips F110W ~25 NIC2. The near-infrared color-magnitude diagrams confirm...
We report HST/STIS spectroscopy and Gemini/GMOS-N imaging of the Damped Lyα (DLA) system toward HS 1543+5921 caused by host star-forming galaxy (SFG) SBS 1543+593. The Gemini image shows new morphological details this well-resolved DLA galaxy. In combination with previous optical spectra, UV spectra enable us to compare, for first time, ionized neutral gas-phase α-element abundances derived from emission- absorption-line spectroscopy, in a bona fide we determine using emission-line...
We present results of CCD imaging in B, V five late-type galaxies with radial velocities 350 km/s the Canes Venatici cloud. Based on photometry their brightest blue stars we derived following distances to galaxies: 9.7 Mpc for NGC 4144, 4.5 4244, 4.2 4395, 2.9 4449, and 8.2 UGC 8331.
We investigate the stellar content of starburst dwarf galaxy IC10 using accurate and deep optical data collected with Advanced Camera for Surveys Wide Field Planetary 2 onboard Hubble Space Telescope. The comparison between theory observations indicates a clear change in age distribution when moving from center toward external regions. Moreover, empirical calibrators evolutionary predictions suggest presence spread heavy element abundance order one-half dex. old intermediate-age core...
The results of DAOPHOT photometry several hundred stars in five irregular galaxies are presented using V and I CCD frames, obtained with the Nordic Optical Telescope under a 0.6 arcsec seeing. Based on brightest blue red we estimate following distances to galaxies: 3.2 Mpc for UGCA 105, 2.6 86, 1.8 92, 1.7 NGC 1569, Cas 1. problem membership IC 342/Maffei complex is briefly discussed.
We present deep Hubble Space Telescope (HST) single-star photometry of Leo A in B, V, and I. Our new field view is offset from the centrally located observed by Tolstoy et al. order to expose halo population this galaxy. report detection metal-poor red horizontal branch stars, which demonstrate that not a young In fact, as least old Galactic Globular Clusters exhibit branches are considered have minimum age about 9 Gyr. discuss distance perform an extensive comparison data with stellar...
We report new imaging and spectroscopic observations of the damped Lyα absorber (DLA) galaxy SBS 1543+593, a nearby dwarf whose stellar disk is intersected by sight line to bright background QSO HS 1543+5921. Hubble Space Telescope with WFPC2 in F450W F702W bands are used measure DLA galaxy's properties compile catalog its (candidate) H II regions. Ground-based long-slit spectroscopy brightest region yields estimates star formation rate (SFR) chemical abundances interstellar medium. find...
We find that NGC 6789 is the most nearby example of a blue compact dwarf galaxy known to date. With help Wide Field Planetary Camera 2 aboard Hubble Space Telescope, we resolve into over 15,000 point sources in V and I bands. The young stars are found exclusively near center galaxy. red giant population identified at large galactocentric radii yields distance about 3.6 Mpc, stellar metallicity [Fe/H] -2, minimum age 1 Gyr. Despite its isolated location Local Void, low metallicity, active...
We present the first resolved-star photometry of VV124 (UGC4879) and find that this is most isolated dwarf galaxy in periphery Local Group. Based on imaging spectroscopic follow up observations with 6m BTA telescope, we resolve into 1560 stars down to limiting magnitude levels V~25.6 I~23.9. The young blue stellar populations emission gas are found near core, but noticeably displaced from center as traced by dominant evolved red stars. mean radial velocity derived spectra two Blue Supergiant...
We present the results of stellar photometry polar ring galaxies NGC 2685 and 4650A, using archival data obtained with Hubble Space Telescope's Wide Field Planetary Camera 2. Polar rings these were resolved into ∼800 ∼430 objects in B, V, IC bands, a considerable part which are blue supergiants located young complexes. The features CM diagrams best represented by isochrones metallicity Z = 0.008. process star formation both was continuous, age youngest detected stars is about 9 Myr for 6.5 4650A.
We present the first results from HST/ACS Grism Parallel Survey, a large program obtaining deep, slitless ACS grism spectroscopy of high-latitude HST parallel fields. report on 11 high Galactic latitude fields here, each with integration times >12 ks. identify 601 compact emission line galaxies at z < 1.6, reaching lines to flux limit > 5 E-18 ergs/cm^2/s (3 sigma). determine redshifts by cross correlation target spectra template spectra, followed visual inspection. measure star...