J. Cabrera-Caño

The ALHAMBRA Survey: A Large Area Multimedium-Band Optical and Near-Infrared Photometric Survey

Here we describe the first results of the Advanced Large Homogeneous Area Medium-Band Redshift Astronomical (ALHAMBRA) survey, which provides cosmic tomography of the evolution of the contents of the universe over most of cosmic history. Our novel approach employs 20 contiguous, equal-width, medium-band filters covering from 3500 A to 9700 A, plus the standard JHKs near-infrared (NIR) bands, to observe a total area of 4 deg2 on the sky. The optical photometric system has been designed to maximize the number of objects with accurate classification by spectral energy distribution type and redshift, and to be sensitive to relatively faint emission features in the spectrum. The observations are being carried out with the Calar Alto 3.5 m telescope using the wide-field cameras in the optical, Large Area Imager for Calar Alto, and in the NIR, Omega-2000. The first data confirm that we are reaching the expected magnitude limits (for a total of 100 ks integration time per pointing) of AB ≤ 25 mag (for an unresolved object, signal-to-noise ratio = 5) in the optical filters from the blue to 8300 A, and from AB = 24.7 to 23.4 for the redder ones. The limit in the NIR, for a total of 15 ks exposure time per pointing, is (in the Vega system) Ks ≈ 20 mag, H≈ 21 mag, J≈ 22 mag. Some preliminary results are presented here to illustrate the capabilities of the ongoing survey. We expect to obtain accurate redshift values, Δz/(1 + z) ≤ 0.03 for about five ×105 galaxies with I ≤ 25 (60% completeness level), and z med = 0.74. This accuracy, together with the homogeneity of the selection function, will allow for the study of the redshift evolution of the large-scale structure, the galaxy population and its evolution with redshift, the identification of clusters of galaxies, and many other studies, without the need for any further follow-up. It will also provide targets for detailed studies with 10 m class telescopes. Given its area, spectral coverage, and its depth, apart from those main goals, the ALHAMBRA survey will also produce valuable data for galactic studies.

Optimal filter systems for photometric redshift estimation

In the coming years, several cosmological surveys will rely on imaging data to estimate the redshift of galaxies, using traditional filter systems with 4-5 optical broad bands; narrower filters improve the spectral resolution, but strongly reduce the total system throughput. We explore how photometric redshift performance depends on the number of filters nf , characterizing the survey depth by the fraction of galaxies with unambiguous redshift estimates. For a combination of total exposure time and telescope imaging area of 270 hr m2, 4-5 filter systems perform significantly worse, both in completeness depth and precision, than systems with nf 8 filters. Our results suggest that for low nf the color-redshift degeneracies overwhelm the improvements in photometric depth, and that even at higher nf the effective photometric redshift depth decreases much more slowly with filter width than naively expected from the reduction in the signal-to-noise ratio. Adding near-IR observations improves the performance of low-nf systems, but still the system which maximizes the photometric redshift completeness is formed by nine filters with logarithmically increasing bandwidth (constant resolution) and half-band overlap, reaching ~0.7 mag deeper, with 10% better redshift precision, than 4-5 filter systems. A system with 20 constant-width, nonoverlapping filters reaches only ~0.1 mag shallower than 4-5 filter systems, but has a precision almost three times better, ?z = 0.014(1 + z) versus ?z = 0.042(1 + z). We briefly discuss a practical implementation of such a photometric system: the ALHAMBRA Survey.

The ALHAMBRA Survey: Bayesian photometric redshifts with 23 bands for 3 deg2

The ALHAMBRA (Advance Large Homogeneous Area Medium Band Re dshift Astronomical) survey has observed 8 different regions of the sky, incl uding sections of the COSMOS, DEEP2, ELAIS, GOODS-N, SDSS and Groth fields using a new photometric system with 20 contiguous �300 ˚ A filters covering the optical range, combining them with deep JHKs imaging. The observations, carried out with the Calar Alto 3.5m telescope using the wide field (0.25 deg 2 FOV) optical camera LAICA and the NIR instrument Omega-2000, correspond to �700hrs of on-target science images. The photometric system was specifically designed to maximize the effective depth of the survey in terms of accurate spectral-type and photometric redshift estimation along with the capability of identi fication of relatively faint emission lines. Here we present multicolor photometry and photometric redshifts for �438,000 galaxies, detected in synthetic F814W images, complete down to a magnitude I�24.5AB, carefully taking into account realistic noise estimates, and correct ing by PSF and aperture effects with the ColorPro software. The photometric zeropoints have been calibrated using stellar transformation equations and refined internally, using a new tech nique based on the highly robust photometric redshifts measured for emission line galaxies. We calculate photometric redshifts with the BPZ2.0 code, which includes new empirically calibrated galaxy templates and priors. —

NEAR-INFRARED GALAXY COUNTS AND EVOLUTION FROM THE WIDE-FIELD ALHAMBRA SURVEY*

The ALHAMBRA survey aims to cover 4 deg2 using a system of 20 contiguous, equal width, medium-band filters spanning the range 3500 A-9700 A plus the standard JHKs filters. Here we analyze deep near-IR number counts of one of our fields (ALH08) for which we have a relatively large area (0.5 deg2) and faint photometry (J = 22.4, H = 21.3, and K = 20.0 at the 50% of recovery efficiency for point-like sources). We find that the logarithmic gradient of the galaxy counts undergoes a distinct change to a flatter slope in each band: from 0.44 at [17.0, 18.5] to 0.34 at [19.5, 22.0] for the J band; for the H band 0.46 at [15.5, 18.0] to 0.36 at [19.0, 21.0], and in Ks the change is from 0.53 in the range [15.0, 17.0] to 0.33 in the interval [18.0, 20.0]. These observations together with faint optical counts are used to constrain models that include density and luminosity evolution of the local type-dependent luminosity functions. Our models imply a decline in the space density of evolved early-type galaxies with increasing redshift, such that only 30%-50% of the bulk of the present day red ellipticals was already in place at z ~ 1.

Corrugations and star formation activity - The Carina-Sagittarius arm

The vertical structure of the Carina-Sagittarius spiral arm is analyzed in relation to the two-dimensional density distribution of young star-gas supercomplexes in the Galactic plane. The Z profile is obtained as a cut of our three-dimensional topography of the Galactic disk in the solar neighborhood (Alfaro, Cabrera-Cano, & Delgado 1991) along the spiral arm segment contained in it. Spectral analysis of this vertical profile leads to a set of significant frequencies, which can best be interpreted in terms of a nonlinear oscillatory process with a characteristic wavelength of 2.4 kpc

The 2011 October Draconids outburst – II. Meteoroid chemical abundances from fireball spectroscopy

We acknowledge support from the Spanish Ministry of Science and Innovation (projects AYA2009-13227, AYA2009-14000-C03-01 and AYA2011-26522), Junta de Andalucia (project P09-FQM-4555) and CSIC (grant # 201050I043).

The ALHAMBRA survey : evolution of galaxy clustering since z ~ 1.

PA-M was supported by an ERC StG Grant (DEGAS-259586). PN acknowledges the support of the Royal Society through the award of a University Research Fellowship and the European Research Council, through receipt of a Starting Grant (DEGAS-259586). This work was supported by the Science and Technology Facilities Council (grant number ST/F001166/1), by the Generalitat Valenciana (project of excellence Prometeo 2009/064), by the Junta de Andalucia (Excellence Project P08-TIC-3531) and by the SpanishMinistry for Science and Innovation (grantsAYA2010-22111-C03-01 and CSD2007-00060).

The alhambra photometric system

This paper presents the characterization of the optical range of the ALHAMBRA photometric system, a 20 contiguous, equal-width, medium-band CCD system with wavelength coverage from 3500 A to 9700 A. The photometric description of the system is done by presenting the full response curve as a product of the filters, CCD, and atmospheric transmission curves, and using some first- and second-order moments of this response function. We also introduce the set of standard stars that defines the system, formed by 31 classic spectrophotometric standard stars which have been used in the calibration of other known photometric systems, and 288 stars, flux calibrated homogeneously, from the Next Generation Spectral Library (NGSL). Based on the NGSL, we determine the transformation equations between Sloan Digital Sky Survey ugriz photometry and the ALHAMBRA photometric system, in order to establish some relations between both systems. Finally, we develop and discuss a strategy to calculate the photometric zero points of the different pointings in the ALHAMBRA project.

Hierarchical Star Formation: Stars and Stellar Clusters in the Gould Belt

We perform a study of the spatial and kinematical distribution of young open clusters in the solar neighborhood, discerning between bound clusters and transient stellar condensations within our sample. Then, we discriminate between Gould Belt (GB) and local Galactic disk (LGD) members, using a previous estimate of the structural parameters of both systems obtained from a sample of O-B6 Hipparcos stars. Using this classified sample we analyze the spatial structure and the kinematic behavior of the cluster system in the GB. The two star formation regions that dominate and give the GB its characteristic inclined shape show a striking difference in their content of star clusters: while Ori OB1 is richly populated by open clusters, not a single one can be found within the boundaries of Sco OB2. This is mirrored in the velocity space, translating again into an abundance of clusters in the region of the kinematic space populated by the members of Ori OB1, and a marginal number of them associated to Sco OB2. In the light of these results we study the nature of the GB with respect to the optical segment of the Orion Arm, and we propose that the different content of star clusters, the different heights over the Galactic plane and the different residual velocities of Ori OB1 and Sco OB2 can be explained in terms of their relative position to the density maximum of the Local Arm in the solar neighborhood. Although morphologically intriguing, the GB appears to be the result of our local and biased view of a larger star cluster complex in the Local Arm, that could be explained by the internal dynamics of the Galactic disk.

Topography of the Galactic disk : Z structure and large-scale star formation

A sample of young open clusters (age less than 10 7 yr) with cataloged distances, treated with the Kriging techniques have been used to delineate a three-dimensional morphological description of the Galactic disk defined by the young stellar population. The basic idea entails considering the values of the positional variable Z for the cluster sample as prospectings of the displacement of the Galactic disk in respect to the Galactic equator in the (X, Y) plane. The Kriging technique is described with special emphasis on its application to the automatic cartography problem.