ﻻ يوجد ملخص باللغة العربية
We present a spectroscopic campaign to follow-up red colour-selected candidate massive galaxies in two high redshift proto-clusters surrounding radio galaxies. We observed a total of 57 galaxies in the field of MRC0943-242 (z=2.93) and 33 in the field of PKS1138-262 (z=2.16) with a mix of optical and near-infrared multi-object spectroscopy. We confirm two red galaxies in the field of PKS1138-262 at the redshift of the radio galaxy. Based on an analysis of their spectral energy distributions, and their derived star formation rates from the H-alpha and 24um flux, one object belongs to the class of dust-obscured star-forming red galaxies, while the other is evolved with little ongoing star formation. This result represents the first red and mainly passively evolving galaxy to be confirmed as companion galaxies in a z>2 proto-cluster. Both red galaxies in PKS1138-262 are massive, of the order of 4-6x10^11 M_Sol. They lie along a Colour-Magnitude relation which implies that they formed the bulk of their stellar population around z=4. In the MRC0943-242 field we find no red galaxies at the redshift of the radio galaxy but we do confirm the effectiveness of our JHK_s selection of galaxies at 2.3<z<3.1, finding that 10 out of 18 (56%) of JHK_s-selected galaxies whose redshifts could be measured fall within this redshift range. We also serendipitously identify an interesting foreground structure of 6 galaxies at z=2.6 in the field of MRC0943-242. This may be a proto-cluster itself, but complicates any interpretation of the red sequence build-up in MRC0943-242 until more redshifts can be measured.
We present images obtained with LABOCA on the APEX telescope of a sample of 22 galaxies selected via their red Herschel SPIRE 250-, 350- and $500textrm{-}mutextrm{m}$ colors. We aim to see if these luminous, rare and distant galaxies are signposting
Clear identifications of Galactic young stellar clusters farther than a few kpc from the Sun are rare, despite the large number of candidate clusters. We aim to improve the selection of candidate clusters rich in massive stars with a multiwavelength
We present optical spectroscopic follow-up of a sample of Distant Red Galaxies (DRGs) with K < 22.5 (Vega), selected by J-K > 2.3, in the Hubble Deep Field South, the MS 1054-03 field, and the Chandra Deep Field South. Spectroscopic redshifts were ob
Spectral absorption features can be used to constrain the stellar initial mass function (IMF) in the integrated light of galaxies. Spectral indices used at low redshift are in the far red, and therefore increasingly hard to detect at higher and highe
Keck spectroscopy of 5 proto-globular cluster candidates in NGC 1275 has been combined with HST WFPC2 photometry to explore the nature and origin of these objects and discriminate between merger and cooling flow scenarios for globular cluster formati