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Corsini E.M.,University of Padua | Corsini E.M.,National institute for astrophysics | Mendez-Abreu J.,Instituto Astrofisico Of Canarias | Mendez-Abreu J.,University of La Laguna | And 11 more authors.
Monthly Notices of the Royal Astronomical Society: Letters | Year: 2012

The early-type spiral NGC4698 is known to host a nuclear disc of gas and stars which is rotating perpendicularly with respect to the galaxy main disc. In addition, the bulge and main disc are characterized by a remarkable geometrical decoupling. Indeed, they appear elongated orthogonally to each other. In this work, the complex structure of the galaxy is investigated by a detailed photometric decomposition of optical and near-infrared images. The intrinsic shape of the bulge was constrained from its apparent ellipticity, its twist angle with respect to the major axis of the main disc and the inclination of the main disc. The bulge is actually elongated perpendicular to the main disc and it is equally likely to be triaxial or axisymmetric. The central surface brightness, scalelength, inclination and position angle of the nuclear disc were derived by assuming that it is infinitesimally thin and exponential. Its size, orientation and location do not depend on the observed passband. These findings support a scenario in which the nuclear disc is the end result of the acquisition of external gas by the pre-existing triaxial bulge on the principal plane perpendicular to its shortest axis and perpendicular to the galaxy main disc. The subsequent star formation either occurred homogeneously all over the extension of the nuclear disc or through an inside-out process that ended more than 5 Gyr ago. © 2012 The Authors. Monthly Notices of the Royal Astronomical Society. © 2012 RAS.

Flores-Meza R.,National Autonomous University of Mexico | Cuevas S.,National Autonomous University of Mexico | Diaz J.J.,Instituto Astrofisico Of Canarias | Espejo C.,National Autonomous University of Mexico | And 3 more authors.
Proceedings of SPIE - The International Society for Optical Engineering | Year: 2012

FRIDA will be a common-user near infrared imager and integral field spectrograph covering the wavelength range from 0.9 to 2.5 microns. Primary observing modes driven the instrument design are two: direct imaging and integral field spectroscopy. FRIDA will be installed at the Nasmyth-B platform of the Gran Telescopio Canarias (GTC) behind the GTC Adaptive Optics (GTCAO) system. Instrument will use diffraction-limited optics to avoid degrading the high Strehl ratios derived by the GTCAO system in the near infrared. High-performance astronomical instruments with a high reconfiguration degree as FRIDA, not only depends on optical and mechanical efficient designs but also on the good quality of its electronics and control systems design. In fact, astronomical instruments operating performance on telescope greatly relies on electronics and control system. This paper describes the main design topics for the FRIDA electronics and mechanisms control system, pointing on the development that these areas have reached on the project status. FRIDA Critical Design Review (CDR) was held on September 2011. © 2012 SPIE.

Fusco F.,University of Rome Tor Vergata | Buonanno R.,University of Rome Tor Vergata | Buonanno R.,National institute for astrophysics | Bono G.,University of Rome Tor Vergata | And 4 more authors.
Astronomy and Astrophysics | Year: 2012

On the basis of a new photometric analysis of the Local Group dwarf irregular galaxy NCG 6822 based on observations obtained with the Advanced Camera for Surveys onboard the Hubble Space Telescope, we have obtained a new estimate of the extinction of two fields located in the southeast region of the galaxy. Because of significant differences in the distance estimates to NGC 6822 available in literature, we decided to provide an independent determination of the distance to this galaxy based on an updated and self-consistent theoretical calibration of the tip of the red giant branch brightness. As a result we newly determined the distance to NGC 6822 to be equal to (m-M)0 = 23.54 ± 0.05, and compared our measurement with the most recent determinations of this distance. © 2012 ESO.

Lorenzi V.,Fundacion Galileo Galilei INAF | Pinilla-Alonso N.,University of Tennessee at Knoxville | Licandro J.,Instituto Astrofisico Of Canarias | Licandro J.,University of La Laguna
Astronomy and Astrophysics | Year: 2015

Context. Icy dwarf planets are key for studying the chemical and physical states of ices in the outer solar system. The study of secular and rotational variations gives us hints of the processes that contribute to the evolution of their surface. Aims. The aim of this work is to search for rotational variability on the surface composition of the dwarf planet (136472) Makemake Methods. We observed Makemake in April 2008 with the medium-resolution spectrograph ISIS, at the William Herschel Telescope (La Palma, Spain) and obtained a set of spectra in the 0.28-0.52 μm and 0.70-0.95 μm ranges, covering 82% of its rotational period. For the rotational analysis, we organized the spectra in four different sets corresponding to different rotational phases, and after discarding one with low signal to noise, we analyzed three of them that cover 71% of the surface. For these spectra we computed the spectral slope and compared the observed spectral bands of methane ice with reflectances of pure methane ice to search for shifts of the center of the bands, related to the presence of CH4/N2 solid solution. Results. All the spectra have a red color with spectral slopes between 20%/1000 Å and 32%/1000 Å in accordance with previously reported values. Some variation in the spectral slope is detected, pointing to the possibility of a variation in the surface content or the particle size of the solid organic compound. The absorption bands of methane ice present a shift toward shorter wavelengths, indicating that methane (at least partially) is in solid solution with nitrogen. There is no variation within the errors of the shifts with the wavelength or with the depth of the bands, so there is no evidence of variation in the CH4/N2 mixing ratio with rotation. By comparing with all the available data in the literature, no secular compositional variations between 2005 and 2008 is found. © 2015 ESO.

Mendez-Abreu J.,Instituto Astrofisico Of Canarias | Mendez-Abreu J.,University of La Laguna
Revista Mexicana de Astronomia y Astrofisica: Serie de Conferencias | Year: 2013

We investigate the suitability of GTC/OSIRIS Tunable Filters (TFs) for obtaining emission-line maps of extended objects. We developed a technique to reconstruct an emission-line image from a set of images taken at consecutive central wavelengths. We demonstrate the feasibility of the reconstruction method by generating a flux calibrated Hα image of the well-known spiral galaxy M101. We tested our emission-line fluxes and ratios by using data present in the literature. We found that the differences in both Hα fluxes and N II/Hα line ratios are ∼15% and ∼50%, respectively. These results are fully in agreement with the expected values for our observational setup. The proposed methodology will allow us to use OSIRIS/GTC to perform accurate spectrophotometric studies of extended galaxies in the local Universe. © 2013: Instituto de Astronomía, UNAM - Fourth Science Meeting with the GTC Ed. C. Muñoz-Tuñón & J. M. Rodríguez-Espinosa.

Lorenzi V.,Fundacion Galileo Galilei INAF | Pinilla-Alonso N.,University of Tennessee at Knoxville | Licandro J.,Instituto Astrofisico Of Canarias | Licandro J.,University of La Laguna | And 4 more authors.
Astronomy and Astrophysics | Year: 2016

Context. During the past 30 years the surface of Pluto has been characterized and its variability monitored through continuous near-infrared spectroscopic observations. But in the visible range only a few data are available. Aims. The aim of this work is to define Pluto's relative reflectance in the visible range to characterize the different components of its surface, and to provide ground based observations in support of the New Horizons mission. Methods. We observed Pluto on six nights between May and July 2014 with the imager/spectrograph ACAM at the William Herschel Telescope (La Palma, Spain). The six spectra obtained cover a whole rotation of Pluto (Prot = 6.4 days). For all the spectra, we computed the spectral slope and the depth of the absorption bands of methane ice between 0.62 and 0.90 μm. To search for shifts in the center of the methane bands, which are associated with dilution of CH4 in N2, we compared the bands with reflectances of pure methane ice. Results. All the new spectra show the methane ice absorption bands between 0.62 and 0.90 μm. Computation of the depth of the band at 0.62 μm in the new spectra of Pluto and in the spectra of Makemake and Eris from the literature, allowed us to estimate the Lambert coefficient at this wavelength at temperatures of 30 K and 40 K, which has never been measured before. All the detected bands are blueshifted with respect to the position for pure methane ice, with minimum shifts correlated to the regions where the abundance of methane is higher. This could be indicative of a dilution of CH4:N2 that is more saturated in CH4. The longitudinal and secular variations in the parameters measured in the spectra are in accordance with results previously reported in the literature and with the distribution of the dark and bright materials that show the Pluto's color maps from New Horizons. © ESO, 2016.

Mendez-Abreu J.,Instituto Astrofisico Of Canarias | Mendez-Abreu J.,University of La Laguna | Simonneau E.,CNRS Paris Institute of Astrophysics | Aguerri J.A.L.,Instituto Astrofisico Of Canarias | And 2 more authors.
Astronomy and Astrophysics | Year: 2010

Context. Knowledge of the intrinsic shapes of galaxy components provides crucial information when constraining phenomena driving their formation and evolution. Aims. We analize the structural parameters of a magnitude-limited sample of 148 unbarred S0-Sb galaxies to derive the intrinsic shape of their bulges. Methods. We developed a new method to derive the intrinsic shapes of bulges based on geometrical relationships between the apparent and intrinsic shapes of bulges and disks. Bulges were assumed to be triaxial ellipsoids sharing the same center and polar axis of their surrounding disks. Disks were assumed to be circular, infinitesimally thin, and to lie on the equatorial plane of bulges. The equatorial ellipticity and intrinsic flattening of bulges were obtained from the length of the apparent major and minor semi-axes of the bulge, the twist angle between the apparent major axis of the bulge and the galaxy line of nodes, and the galaxy inclination. Results. We find that the intrinsic shape is well constrained for a subsample of 115 bulges with favorable viewing angles. A large fraction of them are characterized by an elliptical section (B/A < 0.9). This fraction is 33%, 55%, and 43% if using their maximum, mean, or median equatorial ellipticity, respectively. Most are flattened along their polar axis (C < (A + B)/2). Only 18% of the observed bulges have a probability >50% and none has a probability >90% of being elongated along the polar axis. The distribution of triaxiality is strongly bimodal. This bimodality is driven by bulges with Sérsic index n > 2, or equivalently, by the bulges of galaxies with a bulge-to-total ratio B/T > 0.3. Bulges with n ≤ 2 and with B/T ≤ 0.3 follow a similar distribution, which differs from that of bulges with n > 2 and B/T > 0.3. In particular, bulges with n ≤ 2 and B/T ≤ 0.3 exhibit a larger fraction of oblate axisymmetric (or nearly axisymmetric) bulges, a smaller fraction of triaxial bulges, and fewer prolate axisymmetric (or nearly axisymmetric) bulges with respect to bulges with n > 2 and with B/T > 0.3, respectively. No correlation is found between the intrinsic shape and either the luminosity or velocity dispersion of bulges. Conclusions. According to predictions of the numerical simulations of bulge formation, bulges with n ≤ 2, which show a high fraction of oblate axisymmetric (or nearly axisymmetric) shapes and have B/T ≤ 0.3, may be the result of dissipational minor mergers. Both major dissipational and dissipationless mergers seem to be required to explain the variety of shapes found for bulges with n > 2 and B/T > 0.3. © 2010 ESO.

Tapia M.T.,Instituto Astrofisico Of Canarias | Tapia M.T.,National Autonomous University of Mexico | Tapia M.T.,Autonomous University of Baja California | Schuster W.J.,National Autonomous University of Mexico | And 5 more authors.
Monthly Notices of the Royal Astronomical Society | Year: 2010

The three open clusters Be 15, Be 80 and NGC 2192 have been observed using CCD UBV(RI)C photometry at the San Pedro Mártir Observatory, México within the framework of our open-cluster survey. The fundamental parameters of interstellar reddening, distance and age have been derived, and also the metallicity for NGC 2192 (solar metallicity has been assumed for the other two). By shifting the colours of Schmidt-Kaler in the (U - B, B - V) two-colour diagram along the appropriate reddening vector, the interstellar reddenings have been derived as E(B - V) = 0.23 ± 0.03 mag for Be 15, 1.31 ± 0.05 for Be 80, and 0.16 ± 0.03 for NGC 2192. Evidence is shown for a variable interstellar extinction across the cluster Be 80. For NGC 2192, a nicely consistent fit is obtained for both the interstellar reddening and the metallicity ([Fe/H] = -0.31) using simultaneously the F-type and red-clump stars. By fitting isochrones to the observed sequences of these three clusters in various colour-magnitude diagrams of different colour indices (B - V, V - I or V - R), the averages of distance moduli and heliocentric distances [(V - MV)o (mag); d(pc)] are the following: (10.74 ± 0.01; 1202) for Be 15, (10.75 ± 0.01; 1413) for Be 80 and (12.7 ± 0.01; 3467) for NGC 2192, and the averages of the inferred best ages [log(age); age(Gyr)] are (8.6 ± 0.05; 0.4) for Be 80 and (9.15 ± 0.05; 1.4) for NGC 2192; for Be 15 there are two distinct possibilities for the age fit, depending on the membership of three brighter stars (9.35 or 9.95 ± 0.05; 2.2 or 8.9). The need for spectroscopic observations in Be 15 is emphasized to select between alternate reddening and age solutions, and for deeper UBV observations in Be 80 to study in greater detail the variable interstellar, or intracluster, reddening across this cluster. © 2009 RAS.

Rosado M.,National Autonomous University of Mexico | Sulentic J.,Instituto Astrofisico Of Andalucia | Verdes-Montenegro L.,Instituto Astrofisico Of Andalucia | Perez-Garcia A.,Instituto Astrofisico Of Canarias
Revista Mexicana de Astronomia y Astrofisica: Serie de Conferencias | Year: 2013

We present preliminary OSIRIS Hα, [NII] and [SII] images and line-ratios on the large-scale shock (about 40 kpc long) discovered in the most popular compact group of galaxies: the Stephan's Quintet. The images were obtained by the instrument OSIRIS attached to the GTC. In this work we study only the central region of the shock and show that the shocked region is formed of bright clumps embedded in faint, diffuse gas. We confirm that the shocked gas has high (larger than one) [NII]/Hα and [SII]/Hα line-ratios, characteristic of interstellar radiative shocks and we are able of estimating electron densities from the [SII] 6717/6731 line-ratio. © 2013: Instituto de Astronomía, UNAM - Fourth Science Meeting with the GTC Ed. C. Muñoz-Tuñón & J. M. Rodríguez-Espinosa.

Pietrinferni A.,National institute for astrophysics | Cassisi S.,National institute for astrophysics | Salaris M.,Liverpool John Moores University | Hidalgo S.,Instituto Astrofisico Of Canarias
Astronomy and Astrophysics | Year: 2013

We present an extension of the BaSTI (Bag of Stellar Tracks and Isochrones) stellar evolution database to extremely metal-poor (Z = 10-5) and super-metal-rich (Z = 0.05) metallicities, with both scaled-solar and α-enhanced ([α/Fe] = 0.4) heavy element distributions. These new tracks (from the pre-main sequence to the early-asymptotic giant branch phase), horizontal branch models, and isochrones will enable the use of the BaSTI database to study the most metal-poor populations found in Local Group faint dwarf galaxies, and the metal-rich component of the Galactic bulge, for example. An overview of several fundamental predictions of stellar evolution over the full metallicity range of BaSTI is presented, together with comparisons with literature calculations at Z = 10-5 and Z = 0.05. © ESO, 2013.

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