The impact of systematic uncertainties in stellar parameters on integrated spectra of stellar populations

In this paper we investigate a hitherto unexplored source of potentially significant error in stellar population synthesis (SPS) models, caused by systematic uncertainties associated with the three fundamental stellar atmospheric parameters; effective temperature T_eff, surface gravity g, and iron abundance [Fe/H]. All SPS models rely on calibrations of T_eff, logg and [Fe/H] scales, which are implicit in stellar models, isochrones and synthetic spectra, and are explicitly adopted for empirical spectral libraries. We assess the effect of a mismatch in scales between isochrones and spectral libraries (the two key components of SPS models) and quantify the effects on 23 commonly used diagnostic line indices. We find that typical systematic offsets of 100K in T_eff, 0.15 dex in [Fe/H] and/or 0.25 dex in logg significantly alter inferred absolute ages of simple stellar populations (SSPs) and that in some circumstances, relative ages also change. Offsets in T_eff, logg and [Fe/H] scales for a scaled-solar SSP produce deviations from the model which can mimic the effects of altering abundance ratios to non-scaled-solar chemical compositions, and could also be spuriously interpreted as evidence for a more complex population, especially when multiple-index or full-SED fitting methods are used. We stress that the behavior we find can potentially affect any SPS models, whether using full integrated spectra or fitting functions to determine line strengths. We present measured offsets in 23 diagnostic line indices and urge caution in the over-interpretation of line-index data for stellar populations.Comment: 14 pages, including 4 figures and 3 tables. Accepted for publication in Ap

Star Clusters in M 31. IV. A Comparative Analysis of Absorption Line Indices in Old M 31 and Milky Way Clusters

We present absorption line indices measured in the integrated spectra of globular clusters both from the Galaxy and from M 31. Our samples include 41 Galactic globular clusters, and more than 300 clusters in M 31. The conversion of instrumental equivalent widths into the Lick system is described, and zero-point uncertainties are provided. Comparison of line indices of old M 31 clusters and Galactic globular clusters suggests an absence of important differences in chemical composition between the two cluster systems. In particular, CN indices in the spectra of M 31 and Galactic clusters are essentially consistent with each other, in disagreement with several previous works. We reanalyze some of the previous data, and conclude that reported CN differences between M 31 and Galactic clusters were mostly due to data calibration uncertainties. Our data support the conclusion that the chemical compositions of Milky Way and M 31 globular clusters are not substantially different, and that there is no need to resort to enhanced nitrogen abundances to account for the optical spectra of M 31 globular clusters.Comment: 72 pages, including 15 figures and 14 tables. Published by the Astronomical Journa

Growth performance, carcase characteristics and meat quality of crossbred bulls and heifers from double-muscled Belgian Blue sires and Brown Swiss, Simmental and Rendena dams

Growth, conformation, carcase and meat quality traits of crossbred calves obtained in the Alps from selected Belgian Blue sires (BB) and Brown Swiss (BS), Simmental (Si) and Rendena (Re) dams were studied, emphasising differences on dairy and dual purpose maternal breed. Six pens with five heifers (3 BB BS, 1 BB Si, 1 BB Re) and six pens with four young bulls (2 BB BS, 1 BB Si, 1 BB Re) were used. In total 53 crossbred calves were tested: 30 from BS dams and 23 from dual purpose (12 from Si and 11 from Re dams). Growth performances were measured, carcases were scored for muscle conformation and fatness, the fifth rib was dissected, and the Longissimus thoracis (LT) was analysed. The maternal breed had significant effects when the calves from dairy cows (BB BS) were compared to those of the dual pur- pose breeds (BB Si and BB Re), as at slaughter the former were 1.2% taller, 6.0% less in vivo muscle score, 5.0% less carcase muscle score, with a 13% greater proportion of bone in the rib, and their LT had 12.5% less drip losses, but 3% greater cooking losses and 25% greater shear force. It was concluded that when using a BB as a sire, the dam breed has influ- ence on the growth performance traits of the derived crossbreds, but the major influence would regard the carcase and meat quality traits. In the Alps, these differences are reflected in different sold prices of the crossbred calves from dairy and dual purpose breeds at local auctions

Selenium Biofortification in Radish Enhances Nutritional Quality via Accumulation of Methyl-Selenocysteine and Promotion of Transcripts and Metabolites Related to Glucosinolates, Phenolics, and Amino Acids

Two selenium (Se) fertilization methods were tested for their effects on levels of anticarcinogenic selenocompounds in radish (Raphanus sativus), as well as other nutraceuticals. First, radish was grown on soil and foliar selenate applied 7d before harvest at 0, 5, 10 and 20 mg Se per plant. Selenium levels were up to 1,200 mg Se/kg DW in leaves and 120 mg Se/kg DW in roots. The thiols cysteine and glutathione were present at 2-3 fold higher levels in roots of Se treated plants, and total glucosinolate levels were 35% higher, due to increases in glucoraphanin. The only seleno-aminoacid detected in Se treated plants was Se-methyl-SeCys (100 mg/kg FW in leaves, 33 mg/kg FW in roots). The levels of phenolic aminoacids increased with selenate treatment, as did root total nitrogen and protein content, while the level of several polyphenols decreased. Second, radish was grown in hydroponics and supplied with 0, 5, 10, 20, or 40 \uf06dM selenate for one week. Selenate treatment led to a 20-30% increase in biomass. Selenium concentration was 242 mg Se/kg DW in leaves and 85 mg Se/kg DW in roots. Cysteine levels decreased with Se in leaves but increased in roots; glutatione levels decreased in both. Total glucosinolate levels in leaves decreased with Se treatment due to repression of genes involved in glucosinolates metabolism. Se-methyl-SeCys concentration ranged from 7-15 mg/kg FW. Aminoacid concentration increased with Se treatment in leaves but decreased in roots. Roots of Se treated plants contained elevated transcript levels of sulfate transporters (Sultr) and ATP sulfurylase, a key enzyme of S/Se assimilation. No effects on polyphenols were observed. In conclusion, Se biofortification of radish roots may be achieved via foliar spray or hydroponic supply. One to ten radishes could fulfill the daily human requirement (70 \uf06dg) after a single foliar spray of 5 mg selenate per plant or one week of 5-10 \uf06dM selenate supply in hydroponics. The radishes metabolized selenate to the anticarcinogenic compound Se-methyl-selenocysteine. Selenate treatment enhanced levels of other nutraceuticals in radish roots, including glucoraphanin. Therefore, Se biofortification can produce plants with superior health benefit

Mass dependent Evolution of Field Early-Type Galaxies Since z=1

We present the Fundamental Plane (FP) of field early-type galaxies at 0.5<z<1.0. Our project is a continuation of our efforts to understand the formation and evolution of early-type galaxies in different environments. The target galaxies were selected from the comprehensive and homogeneous data set of the Gemini/HST Galaxy Cluster Project. The distant field early-type galaxies follow a steeper FP relation compared to the local FP. The change in the slope of the FP can be interpreted as a mass-dependent evolution. Similar results have been found for cluster early-type galaxies in high redshift galaxy clusters at 0.8<z<1. Therefore, the slope change of the FP appears to be independent of the environment of the galaxies.Comment: 2 pages, 1 figure, to appear in the proceedings of the IAU Symposium no. 262, "Stellar Populations - Planning for the Next Decade", eds. G. R. Bruzual and S. Charlo

Evidence for Blue Straggler Stars Rejuvenating the Integrated Spectra of Globular Clusters

Integrated spectroscopy is the method of choice for deriving the ages of unresolved stellar systems. However, hot stellar evolutionary stages, such as hot horizontal branch stars and blue straggler stars (BSSs), can affect the integrated ages measured using Balmer lines. Such hot, "non-canonical" stars may lead to overestimations of the temperature of the main sequence turn-off, and therefore underestimations of the integrated age of a stellar population. Using an optimized Hbeta index in conjunction with HST/WFPC2 color-magnitude diagrams (CMDs), we show that Galactic globular clusters exhibit a large scatter in their apparent "spectroscopic" ages, which does not correspond to that in their CMD-derived ages. We find for the first time that the specific frequency of BSSs, defined within the same aperture as the integrated spectra, shows a clear correspondence with Hbeta in the sense that, at fixed metallicity, higher BSS ratios lead to younger "apparent" spectroscopic ages. Thus, the specific frequency of BSSs in globular clusters sets a fundamental limit on the accuracy for which spectroscopic ages can be determined for globular clusters, and maybe for other stellar systems like galaxies. The observational implications of this result are discussed.Comment: 5 pages, 2 figures, 1 table. Accepted for publication in ApJ

A large stellar evolution database for population synthesis studies. IV. Integrated properties and spectra

This paper is the 4th in a series describing the latest additions to the BaSTI stellar evolution database, which consists of a large set of homogeneous models and tools for population synthesis studies. Here we present a new set of low and high resolution synthetic spectra based on the BaSTI stellar models, covering a large range of simple stellar populations (SSPs) for both scaled solar and alpha-enhanced metal mixtures. This enables a completely consistent study of the photometric and spectroscopic properties of both resolved and unresolved stellar populations, and allows us to make detailed tests on their integrated properties. Our low resolution spectra are suitable for deriving broadband magnitudes and colors in any photometric system. These spectra cover the full wavelength range (9-160000nm) and include all evolutionary stages up to the end of AGB evolution. Our high resolution spectra are suitable for studying the behaviour of line indices and we have tested them against a large sample of Galactic globular clusters. We find that the range of ages, iron abundances [Fe/H], and degree of alpha-enhancement predicted by the models matches observed values very well. We have also tested the global consistency of the BaSTI models by making detailed comparisons between ages and metallicities derived from isochrone fitting to observed CMDs, and from line index strengths, for the Galactic globular cluster 47Tuc and the open cluster M67. For 47Tuc we find reasonable agreement between the 2 methods, within the estimated errors. From the comparison with M67 we find non-negligible effects on derived line indices caused by statistical fluctuations, which are a result of the specific method used to populate an isochrone and assign appropriate spectra to individual stars. (abridged)Comment: 21 pages including 13 figures. Accepted for publication in ApJ. Low and high resolution integrated spectra, magnitudes, and mass-to-light ratios will appear on the BaSTI website by 1st November 2008 - see http://193.204.1.62/index.htm