Mathematics – Logic
Scientific paper
May 2009
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2009rmxac..35..298b&link_type=abstract
XII Latin American IAU Regional Meeting (Eds. G. Magris, G. Bruzual, & L. Carigi) Revista Mexicana de Astronomía y Astrofísica (
Mathematics
Logic
Scientific paper
The dynamical and populational properties of the high-redshift (z = 0.7) galaxy cluster LCDCS-S001, are analyzed through imaging and multi object spectroscopy obtained with the GMOS instrument in the Gemini South Observatory. The objects were selected in an i'-band cluster field image, and multi-object spectroscopic observations centered at 7500Å were performed for 40 objects. Spectral features were successfully identified for 20 objects, and used to determine the redshift of the cluster. We found that 12 objects are cluster members and estimate a median redshift of 0.709 for this cluster. The relative velocities of the cluster members were used to estimate the projected cluster mass, which was found to be 3.54×10^14~M_&sun;. Lick and D_n(4000) indices were measured and used to determine the stellar population properties of the galaxies, by means of a spectral synthesis through Bruzual & Charlot evolutive models. We found that the bulk of stellar population for the cluster members has a spectrum compatible with solar metallicity and an age between 3.0 and 7.0 Gyrs; with only one exception, the flux contribution of younger (t ≤ 1.0 Gyrs) stars in the spectra does not exceed 25% at 4200Å. Emission [OII] lines were detected for 4 galaxies, all of which showing a stronger contribution of young stars compared with other cluster galaxies. The equivalent width of the [OII]λ3727 line was compared with Magris, Bruzual, & Binette models for HII regions. We found good correspondence between our values and the theoretical predictions for solar metallicity and with star formation timescales 1.0 < τ < 3.0 Gyrs. In morphological terms we have found that the spheroids map better the structure of the cluster, the disk galaxies populating preferably the peripherical regions, and we have concluded that around 10% of the cluster of galaxies are spheroids with the typical effective radius of 10-15 kpc. The bidimensional distribution of the objects shows an elongated morphology of the cluster. Local overdensities identified in the i' image, one of which being part of the cluster, suggests that the cluster is undergoing a fusion process. This hypothesis is strengthened by the identification of the radio source in the 1.4 GHz at the cluster center, characteristic of radio halos found in cluster which undergo dynamical instabilities.
Barbosa Rembold S.
Pastoriza Miriani Griselda
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