Iron abundance ratios

Figure 7 Observed evolution of the calcium to iron abundance ratio with metallicity (A Hartmann and Gehren (1998) Zhao and Magain (1990) Gratton and Sneden (1991) Edvardsson et al., (1993)).

By comparing the observed chemical abundance ratios to supernova model yields, one can calculate , the ratio of the number of SNe la to SNe II events that fit the observations and the synthesized mass of the elements from the model yields. In a study adopting the same analysis techniques as those performed here, [5] found large values of for a trio of low-a stars of [Fe/H] -2. Employing the abundances derived in this study of stars with comparable metallicities, I find that the metal-poor systems presented here possess a- and iron-peak abundances (and based on Na, Mg, Si and Fe) consistent with those observed in metal-poor stars of the MWG (e.g., [6]). 

Abstract. We present preliminary iron abundances and a element (Ca, Mg) abundance ratios for a sample of 22 Red Giant Branch (RGB) Stars in the Sagittarius galaxy (Sgr), selected near the RGB-Tip. The sample is representative of the Sgr dominant population. The mean iron abundance is [Fe/H]=-0.49. The a element abundance ratios are slightly subsolar, in agreement with the results recently presented by [2]. 

Fig. 1. Upper panel metallicity distribution for the 22 stars analyzed so far. Lower panel a element abundance ratio vs iron abundance for 20 stars of the sample. The [a/Fe] abundance ratio is the average of [Mg/Fe] and [Ca/Fe]. A typical errorbar is also plotted.

A library of stellar spectra or absorption-line strengths, taking into account differences in a-element iron and possibly other element abundance ratios. The spectra may be either observational or synthetic, i.e. theoretically computed. 

Another important deviation from constancy in the abundance ratio of elements supposed to be primary is displayed by the ratios Fe/O and [Tc/a-elements in stars, which increase systematically with [Fe/H] (Figs. 8.5,8.6). This is usually attributed to the existence of a substantial contribution to the production of iron found in the younger, more metal-rich stars (like the Sun) by SN la, which take times of the order of a Gyr to complete their evolution and therefore cannot be treated... 

Regardless of the details concerning self-enrichment and winds, the existence of isolated star formation bursts will also affect the iron-oxygen and iron-a relations, introducing scatter in Fe/O and possibly gaps in the iron abundance distribution function. When the interval between successive bursts exceeds the evolution time for SN la (maybe about 1 Gyr), iron will build up in the ISM resulting in an enhanced Fe/O ratio in the second burst so that one can end up with [Fe/O] > 0 (Gilmore Wyse 1991) see Fig. 8.7. 

The strengths of the spectral lines of the cobaltatom and ion are measurable in composite spectra from stars, where iron is also observable and is usually taken as a standard measure of the abundance of heavy elements within stars. Observations show that the abundance ratio Co/Fe has, through most of galactic history, remained constant, even while each has increased in its proportion to H. A puzzle exists only in the most metal-poor stars, where stunning recent observations reveal a Co/Fe ratio that is almost five times greater than solar when Fe/H is near 1/10 oooth of that in the Sun, and that ratio... 

Refractory elements, i.e. REE, Be, Y, Zr, Hf, Nb, and Ta, are present on the Moon in their solar (C 1) abundance ratios. Only W is considerably depleted relative to the other refractories, indicating the presence on the Moon of metallic iron, which is responsible for the depletion of this rather siderophile element. 

Germanium minerals are extremely rare but the element is widely distribnted in trace amounts. Its abundance ratio is about 7 x 10 % and it is mainly associated with copper, zinc, lead, selenium, arsenic, silver, iron, and so on. There are twenty-one isotopes Ge, Ge, Ge, Ge, Ge are naturally occurring. Germaiuum is common in organisms, but it is not an indispensable trace element. In humans, it is nontoxic, but when it reaches 1000 ppm in animal s food, the growth of animals wifi be inhibited and 50% of them will die. 

A conventional mass spectrometer was used to measure ion abtmdance ratios of the diligand fragments [Fe(6511702)2] which were formed during electron-impact ionization. Sample isotopic enrichment levels were obtained from standard curves that related ion abundance ratios to enrichment levels. Tracer concentration was calculated from the values for total iron content and enrichment level. The relative standard deviation for the ion abundance measurement was less than 2%. Recovery of tracers from spiked fecal samples ranged from 90% to 104%. The method was used to analyze samples collected from a human study. Iron availability from breakfast meals was determined in 6 yo mg women by giving 7 mg of in apple juice on one... 

Abundance ratios and the Iron Mass to Light Ratio (IMLR) are good tests for the evolution of galaxies in clusters since they do not depend on the total cluster gas mass. The IMLR is defined as (Renzini et al. 1993) ... 

Figure 3 Observations of the star BD+75°325 (thick solid line) obtained by the Goddard high-resolution spectrometer on board the Hubble space telescope, showing numerous iron and nickel lines in various ionization stages. These data are compared with model atmosphere spectra. The thin solid line is the best fit model for an iron abundance of 4 x 10- and the dotted line is for solar abundances (4 X 10-5). A solar iron-to-nickel ratio has been assumed in both models. Reproduced with permission from Lanz T, Hubeny I and Heap SR (1997) Astrophysical Journal 485 843.

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