Ethyl Chloride

Rose, SamuelF.

doi:10.1016/s0140-6736(00)54849-1

Cited by 3 publications

(5 citation statements)

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“…The observations covered a spectral range of ∼3400 to ∼7300 Å. This covers the Rose (1984) indices and 25 Lick indices from Hδ A to the TiO indices (for Lick index definitions used, see Trager et al 1998 and Worthey & Ottaviani 1997). The main aim of the P02 study was the measurement of Lick indices in metal‐rich bulge GCs.…”

Section: Data and Modelsmentioning

confidence: 99%

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A robust method for the analysis of integrated spectra from globular clusters using Lick indices

Proctor

Forbes

Beasley

2004

Monthly Notices of the Royal Astronomical Society

112

142

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We define a method for the analysis of the integrated spectra of extragalactic globular clusters that provides more reliable measures of the age, metallicity and α‐element abundance ratio than have so far been achieved. The method involves the simultaneous fitting of up to 25 Lick indices in a χ2 fitting technique that maximizes the use of the available data. Here we compare three sets of single stellar population (SSP) models of Lick indices to the high signal‐to‐noise, integrated spectra of 20 Galactic globular clusters. The ages, [Fe/H] and α‐element abundance ratios derived from the SSP models are compared with the results of resolved stellar population studies from the literature. We find good consistency with the published values, with an agreement of better than 0.1 dex in all three derived parameters. The technique allows the identification of abundance ratio anomalies, such as the known nitrogen overabundance in Galactic globular clusters, and the presence of anomalous horizontal branch morphologies. It also minimizes the impact on the derived parameters of imperfect calibration to the Lick system, and reduction errors in general. The method defined in this paper is therefore robust with respect to many of the difficulties that plague the application of SSP models in general. Consequently, it is well suited to the study of extragalactic globular cluster systems.

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Section: Data and Modelsmentioning

confidence: 99%

“…We have measured the CaII index (Rose 1984) from the P02 spectra. This index is known to be sensitive to the presence of hot stars (Rose 1985) such as those occupying the blue horizontal branch (BHB).…”

Section: Rose Indices and Horizontal Branch Starsmentioning

confidence: 99%

A robust method for the analysis of integrated spectra from globular clusters using Lick indices

Proctor

Forbes

Beasley

2004

Monthly Notices of the Royal Astronomical Society

112

142

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“…Two suitable examples are the equivalent width of the H absorption line and the ratio of the central intensity of the combined CaII H and H lines to the central intensity of the CaII line, referred to as the \CaII H + H /CaII K index" (Rose 1985). These features both hardly depend on metallicity (Rose 1984(Rose , 1985. The { 6 { CaII H + H /CaII K index, which is constant in F, G, and K stars, drops signicantly in A and B stars as the CaII lines weaken and the H-Balmer lines strengthen.…”

Section: Predictions From Population Synthesis Modelsmentioning

confidence: 99%

“…However, there is also strong evidence for the evolution of galaxies in clusters. Butcher & Oemler (1978, 1984 pointed out that the fraction of blue galaxies in the cores of rich clusters increases with redshift, from about 2% at z 0 to nearly 20% at z 0:4 | the \Butcher-Oemler" eect (see also Dressler & Gunn 1983Couch & Sharples 1987;Lavery & Henry 1988). These blue galaxies are generally interpreted as star-forming galaxies which h a v e disappeared today, either because they merged or because they were only temporarily blued by i n teraction-induced starbursts (Dressler & Gunn 1983, Lavery & Henry 1988Evrard 1991).…”

Section: Introductionmentioning

confidence: 99%

Evolution of galaxies in clusters

Charlot¹,

Silk²

1994

ApJ

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We use new models of stellar population synthesis to estimate the fraction of stars formed during the last major bursts of star formation in E/S0 galaxies in low-redshift clusters (z < 0:4) from the spectral signatures of intermediate-age stars. We nd that the mass fraction of stars formed in late bursts in early-type galaxies in clusters must have decreased smoothly with redshift, from about 8% at z 1 to less than 1% at z 0. This result, which w e i n terpret as a constraint on stellar mass added in mergers, is nearly independent of the assumed ages and morphological types of the progenitor galaxies prior to the last major bursts of star formation. We then compute the implied color and 4000 A break evolution for progenitors of E/S0 galaxies in clusters at redshifts 0 < z < 1. We i n v estigate a conservative model in which all present-day E/S0 galaxies are assumed to initially be elliptical galaxies and to then undergo bursts of star formation at the rate estimated from the signatures of intermediate-age stars at low redshifts. This model reproduces well the observed spread of colors and 4000 A breaks of galaxies in high-redshift clusters, but underestimates the fraction of galaxies in the blue tail of the distribution. Such a discrepancy may b e i n terpreted as an increasing fraction of spiral galaxies in clusters at high redshift, as suggested independently by recent HST observations of intermediate-redshift clusters. The current data do not seem to require morphological evolution of cluster galaxies out to z 0:4, but suggest that either morphological or strong luminosity e v olution might have played a major role at z > 0:7. Our results provide spectrophotometric corroboration to high redshift of a common, but poorly justied, interpretation of the Butcher-Oemler eect.

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“…Of course, significant progress has also been made in understanding the chemical enrichment histories of elliptical galaxies and bulges from analysis of low-resolution, integrated-light (IL) spectra using line indexes, such as the Lick system (Burstein et al 1984, Faber et al 1985, Worthey et al 1994, Worthey & Ottaviani 1997, Trager et al 1998). These indexes provide estimates of age and composite "metallicity" ("Z") based on lines from multiple elements such as Fe, Mg, and Ca (see Rose 1984, Worthey et al 1994, and Worthey & Ottaviani 1997. GCs are ideal targets for these index systems as they are nearly ideal, single-age stellar populations.…”

Section: Introductionmentioning

confidence: 99%

Detailed Chemical Abundances of Extragalactic Globular Clusters

Bernstein

McWilliam

Globular Clusters - Guides to Galaxies

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We outline a method to measure the detailed chemical composition of extragalactic (unresolved) globular clusters (GCs) from echelle spectra of their integrated light. Our goal is to use this method to measure abundance patterns of GCs in distant spiral and elliptical galaxies to constrain their formation histories. To develop this technique we have obtained a "training set" of integratedlight spectra of resolved GCs in the Milky Way and LMC by scanning across the clusters during exposures. Our training set also include spectra of individual stars in those GCs from which abundances can be obtained in the normal way to provide a check on our integrated-light results. We present here the preliminary integrated-light analysis of one GC in our training set, NGC 104 (47 Tuc), and outline some of the techniques utilized and problems encountered in that analysis.

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Ethyl Chloride

Cited by 3 publications

References 0 publications

A robust method for the analysis of integrated spectra from globular clusters using Lick indices

A robust method for the analysis of integrated spectra from globular clusters using Lick indices

Evolution of galaxies in clusters

Detailed Chemical Abundances of Extragalactic Globular Clusters

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