Astronomy and Astrophysics – Astronomy
Scientific paper
Jun 2006
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2006rmxac..26..201v&link_type=abstract
XI IAU Regional Latin American Meeting of Astronomy (Eds. L. Infante & M. Rubio) Revista Mexicana de Astronomía y Astrofísica (S
Astronomy and Astrophysics
Astronomy
Scientific paper
We investigate 6 clusters of galaxies at intermediate redshift ( 0.18 < z < 0.3), in particular the star formation activity of galaxies. Our Calar Alto MOSCA spectra cover large fields of view reaching out to 2-4 virial radii. This outer region is often called the infall region since here newly arriving galaxies from the surrounding field encounter the special environment of clusters for the first time. We selected 3 fields containing 2 clusters each from the X-ray Dark Cluster Survey (XDC, Gilbank et al. 2004 MNRAS, 348, 551, G04) Each 40'×40' field was observed with 7-8 slit-masks yielding 553 low-resolution galaxy spectra (R ˜ 500). The results for the first field (R285), were already published by Gerken et al. (2004, A&A, 421, 59). We select [OII]λ3717 and Hα equivalent widths as indicators of star formation activity.
In the analysis, we ``averaged'' 4 clusters: VMF73 (z=0.254) and VMF74 (z=0.18) in XDCS field R285 and VMF131 (z=0.295) and VMF132 (z=0.246) in field R265 and we found an increase of the star forming activity towards larger cluster-centric distances as well as towards shallower projected galaxy densities. Galaxies in the third field R220 exhibit a complex redshift structure which makes membership determination difficulty and were excluded of the overall analysis. However, we clearly identified the cluster VMF194 (z=0.211) and confirm another cluster at z=0.261 detected by G04. In addition, a group of galaxies with similar coordinates to VMF194 at z=0.243 is significant. We also detected a population of red star-forming galaxies, belonging to the red-sequence of the clusters and even redder. Those galaxies show a moderate star-forming activity and do not show any other spectral peculiarities. We do not detect any post-starburst galaxy nor AGN in our cluster sample.
Verdugo Miguel
Ziegler Bodo L.
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