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Husemann B.,Leibniz Institute for Astrophysics Potsdam | Jahnke K.,Max Planck Institute for Astronomy | Sanchez S.F.,Institute Astrofisica Of Andalucia Iaa Csic | Sanchez S.F.,Centro Astronomico Hispano Aleman Of Calar Alto Csic Mpg | And 82 more authors.
Astronomy and Astrophysics | Year: 2013

We present the first public data release (DR1) of the Calar Alto Legacy Integral Field Area (CALIFA) survey. It consists of science-grade optical datacubes for the first 100 of eventually 600 nearby (0.005 < z < 0.03) galaxies, obtained with the integral-field spectrograph PMAS/PPak mounted on the 3.5 m telescope at the Calar Alto observatory. The galaxies in DR1 already cover a wide range of properties in color-magnitude space, morphological type, stellar mass, and gas ionization conditions. This offers the potential to tackle a variety of open questions in galaxy evolution using spatially resolved spectroscopy. Two different spectral setups are available for each galaxy, (i) a low-resolution V500 setup covering the nominal wavelength range 3745-7500 Å with a spectral resolution of 6.0 Å (FWHM), and (ii) a medium-resolution V1200 setup covering the nominal wavelength range 3650-4840 Å with a spectral resolution of 2.3 Å (FWHM). We present the characteristics and data structure of the CALIFA datasets that should be taken into account for scientific exploitation of the data, in particular the effects of vignetting, bad pixels and spatially correlated noise. The data quality test for all 100 galaxies showed that we reach a median limiting continuum sensitivity of 1.0 × 10-18 erg s-1 cm-2 Å-1 arcsec-2 at 5635 Å and 2.2 × 10 -18 erg s-1 cm-2 Å-1 arcsec-2 at 4500 Å for the V500 and V1200 setup respectively, which corresponds to limiting r and g band surface brightnesses of 23.6 mag arcsec-2 and 23.4 mag arcsec-2, or an unresolved emission-line flux detection limit of roughly 1 × 10-17 erg s-1 cm-2 arcsec-2 and 0.6 × 10 -17 erg s-1 cm-2 arcsec-2, respectively. The median spatial resolution is 3-7, and the absolute spectrophotometric calibration is better than 15% (1σ). We also describe the available interfaces and tools that allow easy access to this first publicCALIFA data at http://califa.caha.es/DR1. © 2013 ESO.

Perez I.,University of Granada | Perez I.,Instituto Carlos I Of Fisica Teorica Y Computacion | Aguerri J.A.L.,Institute of Astrophysics of Canarias | Aguerri J.A.L.,University of La Laguna | And 2 more authors.
Astronomy and Astrophysics | Year: 2012

Context. The tumbling pattern of a bar is the main parameter characterising its dynamics. From numerical simulations, its evolution since bar formation is tightly linked to the dark halo in which the bar is formed through dynamical friction and angular momentum exchange. Observational measurements of the bar pattern speed with redshift can restrict models of galaxy formation and bar evolution. Aims. We aim to determine for the first time the bar pattern speed evolution with redshift based on morphological measurements. Methods. We have selected a sample of 44 low-inclination ringed galaxies from the SDSS and COSMOS surveys covering the redshift range 0 < z < 0.8 to investigate the evolution of the bar pattern speed. We derived morphological ratios between the deprojected outer ring radius (R ring) and the bar size (R bar). This quantity is related to the parameter R = R CR/R bar used for classifiying bars in slow and fast rotators, and allows us to investigate possible differences with redshift. Results. We obtain a similar distribution of R at all redshifts. We do not find any systematic effect that could be forcing this result. Conclusions. The results obtained here are compatible with the main bulk of the bar population (∼70%) being fast-rotators and with no evolution of the pattern speed with redshift. We argue that if bars are long-lasting structures, the results presented here imply that there has not been a substantial angular momentum exchange between the bar and halo, as predicted by numerical simulations. In consequence, this might imply that the discs of these high surface-brightness galaxies are maximal. © 2012 ESO.

Mediavilla E.,Institute of Astrophysics of Canarias | Mediavilla E.,University of La Laguna | Mediavilla T.,University of Cádiz | Muoz J.A.,University of Valencia | And 5 more authors.
Astrophysical Journal | Year: 2011

We derive an exact solution (in the form of a series expansion) to compute gravitational lensing magnification maps. It is based on the backward gravitational lens mapping of a partition of the image plane in polygonal cells (inverse polygon mapping, IPM), not including critical points (except perhaps at the cell boundaries). The zeroth-order term of the series expansion leads to the method described by Mediavilla etal. The first-order term is used to study the error induced by the truncation of the series at zeroth order, explaining the high accuracy of the IPM even at this low order of approximation. Interpreting the Inverse Ray Shooting (IRS) method in terms of IPM, we explain the previously reported N -3/4 dependence of the IRS error with the number of collected rays per pixel. Cells intersected by critical curves (critical cells) transform to non-simply connected regions with topological pathologies like auto-overlapping or non-preservation of the boundary under the transformation. To define a non-critical partition, we use a linear approximation of the critical curve to divide each critical cell into two non-critical subcells. The optimal choice of the cell size depends basically on the curvature of the critical curves. For typical applications in which the pixel of the magnification map is a small fraction of the Einstein radius, a one-to-one relationship between the cell and pixel sizes in the absence of lensing guarantees both the consistence of the method and a very high accuracy. This prescription is simple but very conservative. We show that substantially larger cells can be used to obtain magnification maps with huge savings in computation time. © 2011 The American Astronomical Society. All rights reserved.

Iglesias-Paramo J.,Institute Astrofisica Of Andalucia Csic | Iglesias-Paramo J.,Centro Astronomico Hispano Aleman | Vilchez J.M.,Institute Astrofisica Of Andalucia Csic | Galbany L.,University of Lisbon | And 46 more authors.
Astronomy and Astrophysics | Year: 2013

This work investigates the effect of the aperture size on derived galaxy properties for which we have spatially-resolved optical spectra. We focus on some indicators of star formation activity and dust attenuation for spiral galaxies that have been widely used in previous work on galaxy evolution. We investigated 104 spiral galaxies from the CALIFA survey for which 2D spectroscopy with complete spatial coverage is available. From the 3D cubes we derived growth curves of the most conspicuous Balmer emission lines (Hα, Hβ) for circular apertures of different radii centered at the galaxy's nucleus after removing the underlying stellar continuum. We find that the Hα flux (f(Hα)) growth curve follows a well-defined sequence with aperture radius that shows a low dispersion around the median value. From this analysis, we derived aperture corrections for galaxies in different magnitude and redshift intervals. Once stellar absorption is properly accounted for, the f(Hα)/f(Hβ) ratio growth curve shows a smooth decline, pointing toward the absence of differential dust attenuation as a function of radius. Aperture corrections as a function of the radius are provided in the interval [0.3, 2.5]R50. Finally, the Hα equivalent-width (EW(Hα)) growth curve increases with the size of the aperture and shows a very high dispersion for small apertures. This prevents us from using reliable aperture corrections for this quantity. In addition, this result suggests that separating star-forming and quiescent galaxies based on observed EW(Hα) through small apertures will probably result in low EW(Hα) star-forming galaxies begin classified as quiescent. © ESO, 2013.

Perez I.,University of Granada | Perez I.,Instituto Carlos I Of Fisica Teorica Y Computacion | Sanchez-Blazquez P.,Autonomous University of Madrid | Sanchez-Blazquez P.,Institute of Astrophysics of Canarias | And 2 more authors.
Astronomy and Astrophysics | Year: 2011

Aims. We wish to determine the influence of bars on the building of galaxy bulges through analysis of ages and metallicities derived from stellar absorption line-strength indices. Methods. Long-slit spectroscopy was obtained for a sample of 20 early-type barred galaxies. Line-strength indices were measured and used to derive age and metallicity gradients in the bulge region by comparing them with stellar population models. The same analysis was carried out with similar data for unbarred galaxies taken from the literature. Results. The bulges of barred galaxies seem to be more metal rich, at a given velocity dispersion (σ), than the bulges of unbarred galaxies, as measured by a few metallicity sensitive indices. There are indications that the ratio of relative abundance of alpha elements with respect to iron, [E/Fe], derived for the bulges of barred galaxies tend to lie above the values of the unbarred galaxies at a given σ. The metallicity gradients for the majority of the bulges are negative so less metal-rich towards the end of the bulge. The gradient values show a large scatter for galaxies with σ below 150 km s-1. The age distribution is related to the presence of a bulge substructure, such as a nuclear ring or an inner disk. The metallicity of both the bulge and the bar are very well correlated, indicating a close link between the enrichment histories of both components. Conclusions. Bulges of barred early type galaxies might have experienced a different chemical enrichment than do the bulges of unbarred galaxies of the same morphological type, the same central velocity dispersion, and low inclination angles. The hinted stellar populations differences separating the bulges of barred and unbarred galaxies and the strong link between the metallicity of the bulge and the presence of a bar points to scenarios where they both form simultaneously in processes that lead to rapid and massive episodes of star formation, possibly linked to the bar formation. To confirm and generalise the results found here, it would be useful to extend the data set to a larger number of unbarred galaxies and a wider range of morphological types © 2011 ESO.

Perez I.,University of Granada | Perez I.,Instituto Carlos I Of Fisica Teorica Y Computacion | Sanchez-Blazquez P.,Autonomous University of Madrid | Zurita A.,University of Granada | And 3 more authors.
Proceedings of the International Astronomical Union | Year: 2010

We have carried out a detailed analysis of stellar properties of bars and bulges of a sample of early-type galaxies. We have also compared the results of the bulge properties with the bulges of a similar sample of unbarred galaxies, deriving the SSP equivalent stellar parameters in the same way as for our sample. We are currently characterising the nebular gas in the bulges of the sample galaxies. We have found differences in the bulge stellar population properties between barred and unbarred galaxies. The bulges of barred galaxies seem to be more metal rich, at a given velocity dispersion (σ), than the bulges of unbarred galaxies, as measured by some metallicity sensitive indices. There are indications that the ratio of relative abundance of alpha-elements with respect to iron, [E/Fe], derived for the bulges of barred galaxies tend to lie above the values of the unbarred galaxies at a given σ. We also find three different types of bars according to their metallicity and age distribution along the radius: 1) Bars with negative metallicity gradients. They show mean young/intermediate population (<2 Gyr), and have amongst the lowest stellar maximum central velocity dispersion of the sample. 2) Bars with null metallicity gradients. These galaxies that do not show any gradient in their metallicity distribution along the bar and have negative age gradients (i.e younger populations at the bar end). 3) Bars with positive metallicity gradients, i.e. more metal rich at the bar ends. These galaxies are predominantly those with higher velocity dispersion and older mean population. We find no significant correlation between the age and metallicity distribution, and bar/galaxy parameters such as the AGN presence, size or the bar strength. From the kinematics, we find that all the galaxies show a disk-like central component. Regarding the ionised gas properties, we find that the nebular metallicity gradients are shallower than the stellar ones, indicating an efficient mixing of the material currently forming. The nebular central metallicities do not show a correlation with the central σ, and, furthermore, in some cases the nebular metallicities are clearly lower than the stellar ones, indicating an external origin for the gas fueling the current star formation. All these results point to a scenario, at least for early-type galaxies, where bars are long-lived and where the formation of the bulge and the bar are closely linked. Later accretion of gas can then be funneled towards the center forming nuclear discs and rings, producing substructures with low level of star formation, but that would not contain enough stars to produce a change in the SSP-equivalent metallicities and [E/Fe]. © Copyright International Astronomical Union 2011.

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