The Advance Large Homogeneous Area Medium-Band Redshift Astronomical (ALHAMBRA) survey has observed eight different regions of the sky, including sections of the Cosmic Evolution Survey (COSMOS), DEEP2, European Large-Area Infrared Space Observatory Survey (ELAIS), Great Observatories Origins Deep Survey North (GOODS-N), Sloan Digital Sky Survey (SDSS) and Groth fields using a new photometric system with 20 optical, contiguous ~300{AA} filters plus the JHKs bands. The filter system is designed to optimize the effective photometric redshift depth of the survey, while having enough wavelength resolution for the identification of faint emission lines. The observations, carried out with the Calar Alto 3.5-m telescope using the wide-field optical camera Large Area Imager for Calar Alto (LAICA) and the near-infrared (NIR) instrument Omega-2000, represent a total of ~700h of on-target science images. Here we present multicolour point-spread function (PSF) corrected photometry and photometric redshifts for ~438000 galaxies, detected in synthetic F814W images. The catalogues are complete down to a magnitude I~24.5AB and cover an effective area of 2.79deg^2^. Photometric zero-points were calibrated using stellar transformation equations and refined internally, using a new technique based on the highly robust photometric redshifts measured for emission-line galaxies. We calculate Bayesian photometric redshifts with the Bayesian Photometric Redshift (bpz)2.0 code, obtaining a precision of {delta}z/(1+z_s_)=1 per cent for I<22.5 and {delta}z/(1+z_s_)=1.4 per cent for 22.5<I<24.5. The global n(z) distribution shows a mean redshift <z>=0.56 for I<22.5AB and <z>=0.86 for I<24.5AB. Given its depth and small cosmic variance, ALHAMBRA is a unique data set for galaxy evolution studies.
We present a catalogue of 348 galaxy clusters and groups with 0.2<z<1.2 selected in the 2.78deg^2^ Advanced Large, Homogeneous Area Medium Band Redshift Astronomical (ALHAMBRA) survey. The high precision of our photometric redshifts, close to 1 percent, and the wide spread of the seven ALHAMBRA pointings ensure that this catalogue has better mass sensitivity and is less affected by cosmic variance than comparable samples. The detection has been carried out with the Bayesian Cluster Finder, whose performance has been checked in ALHAMBRA-like light-cone mock catalogues. Great care has been taken to ensure that the observable properties of the mocks photometry accurately correspond to those of real catalogues. From our simulations, we expect to detect galaxy clusters and groups with both 70 percent completeness and purity down to dark matter halo masses of M_h_~3x10^13^M_{sun}_ for z<0.85. Cluster redshifts are expected to be recovered with ~0.6 percent precision for z<1. We also expect to measure cluster masses with sigma_Mh_|M*CL_~0.25-0.35dex precision down to ~3x10^13^M_{sun}_, masses which are 50 percent smaller than those reached by similar work. We have compared these detections with previous optical, spectroscopic and X-rays work, finding an excellent agreement with the rates reported from the simulations. We have also explored the overall properties of these detections such as the presence of a colour-magnitude relation, the evolution of the photometric blue fraction and the clustering of these sources in the different ALHAMBRA fields. Despite the small numbers, we observe tentative evidence that, for a fixed stellar mass, the environment is playing a crucial role at lower redshifts (z<0.5).
Advanced Large Homogeneous Area Medium Band Redshift Astronomical (ALHAMBRA) is photometric survey designed to trace the cosmic evolution and cosmic variance. It covers a large area of ~4deg^2^ in eight fields, where seven fields overlap with other surveys, allowing us to have complementary data in other wavelengths. All observations were carried out in 20 continuous, medium band (30nm width) optical and 3 near-infrared (JHK) bands, providing the precise measurements of photometric redshifts. In addition, morphological classification of galaxies is crucial for any kind of galaxy formation and cosmic evolution studies, providing the information about star formation histories, their environment and interactions, internal perturbations, etc. We present a morphological classification of >40000 galaxies in the ALHAMBRA survey. We associate to every galaxy a probability to be early type using the automated Bayesian code galsvm. Despite of the spatial resolution of the ALHAMBRA images (~1arcsec), for 22051 galaxies, we obtained the contamination by other type of less than 10 percent. Of those, 1640 and 10322 galaxies are classified as early- (down to redshifts ~0.5) and late-type (down to redshifts ~1.0), respectively, with magnitudes F_613W_<=22.0. In addition, for magnitude range 22.0<F_613W_<=23.0, we classified other 10089 late-type galaxies with redshifts <=1.3. We show that the classified objects populate the expected regions in the colour-mass and colour-magnitude planes. The presented data set is especially attractive given the homogeneous multiwavelength coverage available in the ALHAMBRA fields, and is intended to be used in a variety of scientific applications. The low-contamination catalogue (<10 percent) is made publicly available with this paper.
Relative intensity measurements of Al I and Al II spectral lines in the visible and ultraviolet spectral ranges are performed using a capacitively coupled high frequency double hollow electrode discharge. Branching ratios and intensity ratios within multiplets are determined. By using selected lifetimes absolute transition probabilities are calculated.
MultiConfiguration Dirac-Hartree-Fock (MCDHF) and relativistic configuration interaction (RCI) calculations were performed for 28 and 78 states in neutral and singly ionized aluminium, respectively. In AlI the configurations of interest are 3s^2^nl for n=3,4,5 with l=0 to 4, as well as 3s3p^2^ and 3s^2^6l for l=0,1,2. In AlII, in addition to the ground configuration 3s^2^, the studied configurations are 3snl with n=3 to 6 and l=0 to 5, 3p^2^, 3s7s, 3s7p, and 3p3d. Valence and core-valence electron correlation effects are systematically accounted for through large configuration state function (CSF) expansions. Calculated excitation energies are found to be in excellent agreement with experimental data from the National Institute of Standards and Technology (NIST) database. Lifetimes and transition data for radiative electric dipole (E1) transitions are given and compared with results from previous calculations and available measurements for both AlI and AlII. The computed lifetimes of AlI are in very good agreement with the measured lifetimes in high-precision laser spectroscopy experiments. The present calculations provide a substantial amount of updated atomic data, including transition data in the infrared region. This is particularly important since the new generation of telescopes are designed for this region. There is a significant improvement in accuracy, in particular for the more complex system of neutral AlI. The complete tables of transition data are available online.
The purpose of this work is to provide corrections for the lithium abundance, A(Li), and the ^6^Li/^7^Li ratio that can easily be applied to correct 1D LTE lithium abundances in G and F dwarf stars of approximately solar mass and metallicity for three-dimensional (3D) and non-LTE (NLTE) effects. The corrections for A(Li) and ^6^Li/^7^Li are computed using grids of 3D NLTE and 1D LTE synthetic lithium line profiles, generated from 3D hydro-dynamical CO5BOLD and 1D hydrostatic LHD model atmospheres, respectively. For comparative purposes, all calculations are performed for three different line lists representing the LiI 670.8nm spectral region. The 3D NLTE corrections are then approximated by analytical expressions as a function of the stellar parameters (Teff, logg, [Fe/H], vsini, A(Li), ^6^Li/^7^Li). The derived 3D NLTE corrections range between -0.01 and +0.11dex for A(Li), and between -4.9 and -0.4% for the ^6^Li/^7^Li ratio, depending on the adopted stellar parameters. Our findings show a general consistency with recent works on lithium abundance corrections. In the case of the ^6^Li/^7^Li ratio, our corrections are always negative, showing that 1D LTE analysis can significantly overestimate the presence of ^6^Li (up to 4.9 percentage points) in the atmospheres of solar-like dwarf stars. These results emphasize the importance of reliable 3D model atmospheres combined with NLTE line formation for deriving precise isotopic lithium abundances. Although 3D NLTE spectral synthesis implies an extensive computational effort, the results can be made accessible with parametric tools like the ones presented in this work.
A library of high-S/N optical spectra of FGKM stars
Short Name:
J/ApJ/836/77
Date:
21 Oct 2021
Publisher:
CDS
Description:
Classification of stars, by comparing their optical spectra to a few dozen spectral standards, has been a workhorse of observational astronomy for more than a century. Here, we extend this technique by compiling a library of optical spectra of 404 touchstone stars observed with Keck/HIRES by the California Planet Search. The spectra have high resolution (R~60000), high signal-to-noise ratio (S/N~150/pixel), and are registered onto a common wavelength scale. The library stars have properties derived from interferometry, asteroseismology, LTE spectral synthesis, and spectrophotometry. To address a lack of well-characterized late-K dwarfs in the literature, we measure stellar radii and temperatures for 23 nearby K dwarfs, using modeling of the spectral energy distribution and Gaia parallaxes. This library represents a uniform data set spanning the spectral types ~M5-F1 (T_eff_~3000-7000K, R_*_~0.1-16R_{Sun}_). We also present "Empirical SpecMatch" (SpecMatch-Emp), a tool for parameterizing unknown spectra by comparing them against our spectral library. For FGKM stars, SpecMatch-Emp achieves accuracies of 100K in effective temperature (T_eff_), 15% in stellar radius (R_*_), and 0.09dex in metallicity ([Fe/H]). Because the code relies on empirical spectra it performs particularly well for stars ~K4 and later, which are challenging to model with existing spectral synthesizers, reaching accuracies of 70K in T_eff_, 10% in R_*_, and 0.12dex in [Fe/H]. We also validate the performance of SpecMatch-Emp, finding it to be robust at lower spectral resolution and S/N, enabling the characterization of faint late-type stars. Both the library and stellar characterization code are publicly available.
The machine-readable version of the library contains digital spectra of 161 stars of spectral types O through M and luminosity classes I, III, and V. Most stars are of solar metallicity, although two were chosen specifically for low metallicity. The data were obtained with the Intensified Reticon Scanner on the #1 91-cm telescope at Kitt Peak National Observatory. The scans cover the wavelength range 3510-7427 angstroms, with a resolution of approximately 4.5 angstroms, while the typical photometric uncertainty of each resolution element is about 1 percent and broadband variations are < 3 percent.
We have used the very large Jodrell Bank VLA Astrometric Survey/Cosmic Lens All-Sky Survey 8.4-GHz surveys of flat-spectrum radio sources to test the hypothesis that there is a systematic alignment of polarization position angle vectors on cosmological scales of the type claimed by Hutsemekers et al. (2005, Cat. <J/A+A/441/915>). The polarization position angles of 4290 sources with polarized flux density 1mJy have been examined. They do not reveal large-scale alignments either as a whole or when split in half into high-redshift (z>=1.24) and low-redshift subsamples. Nor do the radio sources which lie in the specific areas covered by Hutsemekers et al. (<J/A+A/441/915>) show any significant effect. We have also looked at the position angles of parsec-scale jets derived from very long baseline interferometry observations and again find no evidence for systematic alignments. Finally, we have investigated the correlation between the polarization position angle and those of the parsec-scale jets. As expected, we find that there is a tendency for the polarization angles to be perpendicular to the jet angles. However, the difference in jet and polarization position angles does not show any systematic trend in different parts of the sky.
Torques acting on galaxies lead to physical alignments, but the resulting ellipticity correlations are difficult to predict. As they constitute a major contaminant for cosmic shear studies, it is important to constrain the intrinsic alignment signal observationally. We measured the alignments of satellite galaxies within 90 massive galaxy clusters in the redshift range 0.05<z<0.55 and quantified their impact on the cosmic shear signal. We combined a sample of 38104 galaxies with spectroscopic redshifts with high-quality data from the Canada-France-Hawaii Telescope. We used phase-space information to select 14576 cluster members, 14250 of which have shape measurements and measured three different types of alignment: the radial alignment of satellite galaxies toward the brightest cluster galaxies (BCGs), the common orientations of satellite galaxies and BCGs, and the radial alignments of satellites with each other. Residual systematic effects are much smaller than the statistical uncertainties. We detect no galaxy alignment of any kind out to at least 3r_200_. The signal is consistent with zero for both blue and red galaxies, bright and faint ones, and also for subsamples of clusters based on redshift, dynamical mass, and dynamical state. These conclusions are unchanged if we expand the sample with bright cluster members from the red sequence. We augment our constraints with those from the literature to estimate the importance of the intrinsic alignments of satellites compared to those of central galaxies, for which the alignments are described by the linear alignment model. Comparison of the alignment signals to the expected uncertainties of current surveys such as the Kilo-Degree Survey suggests that the linear alignment model is an adequate treatment of intrinsic alignments, but it is not clear whether this will be the case for larger surveys.
