Cluster Populations in Abell 2125 and 2218

Rakos, K. D.; Schombert, James M.

doi:10.1086/432504

Cited by 7 publications

(7 citation statements)

References 61 publications

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“…Their mean color locus are shown in Figure 1 as a dotted line (only for vz − yz and bz − yz as SDSS spectra do not cover the uz filter). There is a small shift due to slight different definitions of the filter bandpasses (also seen on other comparison data, Rakos & Schombert 2005b), but the slopes and dispersions are identical.…”

Section: Colors and Photometric Morphologysupporting

confidence: 63%

“…These diagrams show a clear deficiency of low luminosity red galaxies between M V = −19 to −17. Our studies of the Butcher-Oemler effect in clusters, using the same narrow band filter set (Rakos & Schombert 2005b), finds that only 5 to 10% of a galaxy's mass needs to be involved in star formation to produce spiral-like colors as seen in the De Lucia et al diagrams. Given that z = 0.7 corresponds to 6 Gyrs ago (Benchmark cosmology), then this would produce a current generation of low luminosity cluster ellipticals with approximately 10% of their stellar mass in a 6 Gyr population plus the remaining 90% of their stellar mass in a 12 Gyr population.…”

Section: Age and Metallicity Determinationmentioning

confidence: 76%

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Age and Metallicities of Cluster Galaxies: A1185 and Coma

Rakos

Schombert

Odell

2007

ApJ

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We present age and metallicities determinations based on narrow band continuum colors for the galaxies in the rich clusters A1185 and Coma. Using a new technique to extract luminosity-weighted age and [Fe/H] values for non-star-forming galaxies, we find that both clusters have two separate populations based on these parameters. One population is old ($\tau >$ 11 Gyrs) with a distinct mass-metallicity relation. The second population is slightly younger ($\tau \approx$ 9 Gyrs) with lower metallicities and lower stellar masses. We find detectable correlations between age and galaxy mass in both populations such that older galaxies are more massive and have higher mean metallicities, confirming previous work with line indices for the same type of galaxies in other clusters (Kelson et al 2006, Thomas et al 2005). Our results imply shorter durations for higher mass galaxies, in contradiction to the predictions of classic galactic wind models. Since we also find a clear mass-metallicity relation for these galaxies, then we conclude that star formation was more efficient for higher mass galaxies, a scenario described under the inverse wind models (Matteucci 1994). With respect to cluster environmental effects, we find there is a significant correlation between galaxy mean age and distance from the cluster center, such that older galaxies inhabit the core. This relationship would nominally support hierarchical scenarios of galaxy formation (younger age in lower density regions); however, environmental effects probably have larger signature in the sample and present-day galaxies are remnants from an epoch of quenching of initial star formation, which would result in the same age gradients.Comment: 27 pages, 8 figures, accepted to ApJ, AAS LaTe

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Section: Colors and Photometric Morphologysupporting

confidence: 63%

Section: Age and Metallicity Determinationmentioning

confidence: 76%

Age and Metallicities of Cluster Galaxies: A1185 and Coma

Rakos

Schombert

Odell

2007

ApJ

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“…Observations of ellipticals over a range of environments (cluster to field, Bower et al 1992) and to high redshift (Yabe et al 2014) demonstrates the universality of the CMR. In addition, the CMR has been investigated from the far-UV (Jeong et al 2009) to the far-IR (Clemens et al 2011), plus extended from giant to dwarf ellipticals (Rakos & Schombert 2005). In order to follow the evolution of the CMR with redshift, one must define the present-day CMR to a high degree of accuracy and in bandpasses that will be observed at high redshift (i.e., the blue and UV).…”

Section: Color-magnitude Diagramsmentioning

confidence: 99%

Colors of Ellipticals From Galex to Spitzer

Schombert

2016

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Multi-color photometry is presented for a large sample of local ellipticals selected by morphology and isolation. The sample uses data from GALEX, SDSS, 2MASS and Spitzer to cover the filters N U V , ugri, JHK and 3.6µm. Various two-color diagrams, using the half-light aperture defined in the 2MASS J filter, are very coherent from color to color, meaning that galaxies defined to be red in one color are always red in other colors. Comparison to globular cluster colors demonstrates that ellipticals are not composed of a single age, single metallicity (e.g., [Fe/H]) stellar population, but require a multi-metallicity model using a chemical enrichment scenario. Such a model is sufficient to explain two-color diagrams and the color-magnitude relations for all colors using only metallicity as a variable on a solely 12 Gyrs stellar population with no evidence of stars younger than 10 Gyrs. The [Fe/H] values that match galaxy colors range from −0.5 to +0.4, much higher (and older) than population characteristics deduced from Lick/IDS line-strength system studies, indicating an inconsistency between galaxy colors and line indices values for reasons unknown. The N U V colors have unusual behavior signaling the rise and fall of the UV upturn with elliptical luminosity. Models with BHB tracks can reproduce this behavior indicating the UV upturn is strictly a metallicity effect.

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“…Although galaxy luminosity‐weighted metallicity is correlated with galaxy mass, it is uncorrelated with luminosity‐weighted age for the three populations. Rakos, Schombert & Odell (2008) have used narrow‐band colours combined with principal component analysis (Rakos & Schombert 2005) to estimate the luminosity‐weighted stellar metallicities and ages for galaxies in a sample of nearby galaxy clusters. They have found cluster early‐type galaxies to be divided into two distinct populations, an old galaxy population dominated by primordial stellar populations and a second younger galaxy population, well separated by a gap in age of about 2 Gyr from the oldest galaxies, in agreement with our findings.…”

Section: Stellar Population Properties Of Abell 1367 Galaxiesmentioning

confidence: 99%

The galaxy population of Abell 1367: the stellar mass-metallicity relation★

Mouhcine

Kriwattanawong

James

2011

Monthly Notices of the Royal Astronomical Society

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Using wide baseline broad‐band photometry, we analyse the stellar population properties of a sample of 72 galaxies, spanning a wide range of stellar masses and morphological types, in the nearby spiral‐rich and dynamically young galaxy cluster Abell 1367. The sample galaxies are distributed from the cluster centre out to approximately half the cluster Abell radius. The optical/near‐infrared colours are compared with simple stellar population synthesis models from which the luminosity‐weighted stellar population ages and metallicities are determined. The locus of the colours of elliptical galaxies traces a sequence of varying metallicity at a narrow range of luminosity‐weighted stellar ages. Lenticular galaxies in the red sequence, however, exhibit a substantial spread of luminosity‐weighted stellar metallicities and ages. For red‐sequence lenticular galaxies and blue cloud galaxies, low‐mass galaxies tend to be on average dominated by stellar populations of younger luminosity‐weighted ages. Sample galaxies exhibit a strong correlation between integrated stellar mass and luminosity‐weighted stellar metallicity. Galaxies with signs of morphological disturbance and ongoing star formation activity, tend to be underabundant with respect to passive galaxies in the red sequence of comparable stellar masses. We argue that this could be due to tidally driven gas flows towards the star‐forming regions, carrying less enriched gas and diluting the pre‐existing gas to produce younger stellar populations with lower metallicities than would be obtained prior to the interaction. Finally, we find no statistically significant evidence for changes in the luminosity‐weighted ages and metallicities for either red‐sequence or blue‐cloud galaxies, at fixed stellar mass, with location within the cluster.

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Cluster Populations in Abell 2125 and 2218

Cited by 7 publications

References 61 publications

Age and Metallicities of Cluster Galaxies: A1185 and Coma

Age and Metallicities of Cluster Galaxies: A1185 and Coma

Colors of Ellipticals From Galex to Spitzer

The galaxy population of Abell 1367: the stellar mass-metallicity relation★

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