We present deep Hubble Space Telescope Wide Field Camera 3 (HST/WFC3) slitless spectroscopic observations of the distant cluster Cl J1449+0856. These cover a single pointing with 18 orbits of G141 spectroscopy and F140W imaging, allowing us to derive secure redshifts down to M 140 ~ 25.5 AB and 3sigma line fluxes of ~5 × 10-18 erg s-1 cm-2. In particular, we were able to spectroscopically confirm 12 early-type galaxies (ETGs) in the field up to z ~ 3, 6 of which are in the cluster core, which represents the first direct spectroscopic confirmation of quiescent galaxies in a z = 2 cluster environment. With 140 redshifts in a ~6 arcmin2 field, we can trace the spatial and redshift galaxy distribution in the cluster core and background field. We find two strong peaks at z = 2.00 and z = 2.07, where only one was seen in our previously published ground-based data. Due to the spectroscopic confirmation of the cluster ETGs, we can now reevaluate the redshift of Cl J1449+0856 at z = 2.00, rather than z = 2.07, with the background overdensity being revealed to be sparse and "sheet"-like. This presents an interesting case of chance alignment of two close yet unrelated structures, each one preferentially selected by different observing strategies. With 6 quiescent or early-type spectroscopic members and 20 star-forming ones, Cl J1449+0856 is now reliably confirmed to be at z = 2.00. The identified members can now allow for a detailed study of galaxy properties in the densest environment at z = 2.

WFC3 GRISM Confirmation of the Distant Cluster Cl J1449+0856 at langzrang = 2.00: Quiescent and Star-forming Galaxy Populations

CIMATTI, ANDREA;
2013

Abstract

We present deep Hubble Space Telescope Wide Field Camera 3 (HST/WFC3) slitless spectroscopic observations of the distant cluster Cl J1449+0856. These cover a single pointing with 18 orbits of G141 spectroscopy and F140W imaging, allowing us to derive secure redshifts down to M 140 ~ 25.5 AB and 3sigma line fluxes of ~5 × 10-18 erg s-1 cm-2. In particular, we were able to spectroscopically confirm 12 early-type galaxies (ETGs) in the field up to z ~ 3, 6 of which are in the cluster core, which represents the first direct spectroscopic confirmation of quiescent galaxies in a z = 2 cluster environment. With 140 redshifts in a ~6 arcmin2 field, we can trace the spatial and redshift galaxy distribution in the cluster core and background field. We find two strong peaks at z = 2.00 and z = 2.07, where only one was seen in our previously published ground-based data. Due to the spectroscopic confirmation of the cluster ETGs, we can now reevaluate the redshift of Cl J1449+0856 at z = 2.00, rather than z = 2.07, with the background overdensity being revealed to be sparse and "sheet"-like. This presents an interesting case of chance alignment of two close yet unrelated structures, each one preferentially selected by different observing strategies. With 6 quiescent or early-type spectroscopic members and 20 star-forming ones, Cl J1449+0856 is now reliably confirmed to be at z = 2.00. The identified members can now allow for a detailed study of galaxy properties in the densest environment at z = 2.
2013
Gobat R.; Strazzullo V.; Daddi E.; Onodera M.; Carollo M.; Renzini A.; Finoguenov A.; Cimatti A.; Scarlata C.; Arimoto N.
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/11585/392168
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