Home  About us  Contact
 

Red Objects (red + object)

Distribution by Scientific Domains
Physics and Astronomy100%

Selected Abstracts

The FIRST radio survey: Panchromatic properties of FIRST radio sources identified in the Boötes and Cetus fields

ASTRONOMISCHE NACHRICHTEN, Issue 1 2009
K. El Bouchefry
Abstract In this paper the availability of multi-wavelength optical/infrared information of FIRST (Faint Images of the Radio Sky at 20 cm) radio sources counterparts over ,9.2 deg2 in the Boötes field and ,2.4 deg2 in the Cetus field is exploited to infer the physical properties of the faint radio population. The radio sources optically identified have been divided into resolved galaxies and stellar-like objects finding that the faint radio population is mainly composed of early-type galaxies with very red colour (Bw , R , 4.6). A total number of 57 counterparts of FIRST radio sources have extremely red colour (R , K , 5). Photometric redshift from Hyperz implies that the Extremely Red Objects (EROs) counterparts to FIRST radio sources are mostly located in the range z = 0.7,2, with the bulk of the population at z , 1. Taking advantage of the near infrared imaging with FLAMEX (FLAMINGOS Extragalactic Infrared Survey), the EROs counterparts to FIRST radio sources are separated into passively-evolving and dusty star-forming galaxies using their RJK colours; the relatively blue J , K of these galaxies suggest that most are old elliptical galaxies (18/25) rather than dusty starburst galaxies (7/25). A total of 15 Distant Red Galaxy (DRGs) have been identified as counterparts to FIRST radio sources in the Cetus field and 3 DRGs in the Boötes field with J , K > 2.3 (© 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]

Hard X,ray observations of Extremely Red Objects

ASTRONOMISCHE NACHRICHTEN, Issue 1-2 2003
M. Brusa
Abstract Extremely Red Objects (EROs, R,K>5) constitute a heterogeneous class of extragalactic sources including high redshift elliptical galaxies, dusty star,forming systems and heavily obscured AGNs. Hard X-ray observations provide an unique and powerful tool to uncover obscured nuclear or star,forming activity. We present the results of XMM,Newton observations of the largest sample of EROs available to date (about 450 objects over a contiguous area of 700 arcmin2). Five of the 46 hard X,ray selected sources brighter than 3 × 10,15 cgs in the 2,10 keV band, are associated with EROs. All of the X-ray detected EROs show rather extreme X,ray,to,optical flux ratios, suggesting the presence of highly obscured AGN activity. We also report on the X,ray stacking analysis of spectroscopically identified EROs in the Chandra Deep Field South. [source]

The nature, evolution, clustering and X-ray properties of extremely red galaxies in the Chandra Deep Field South/Great Observatories Origins Deep Survey field

MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, Issue 3 2003
Nathan D. Roche
ABSTRACT We identify a very deep sample of 198 extremely red objects (EROs) in the Chandra Deep Field South, selected on the basis of I775,Ks > 3.92, to a limit Ks, 22 using the public European Southern Observatory (ESO)/Great Observatories Origins Deep Survey (GOODS) survey. The ERO number counts flatten from a slope of ,, 0.59 to 0.16 at K > 19.5, where they remain below the predictions for pure luminosity evolution, and fall below even a non-evolving model. This suggests there is a significant decrease with redshift in the comoving number density of passive/very red galaxies. We investigate the angular correlation function, ,(,), of these EROs and detect positive clustering for Ks= 20.5,22.0 sources. The EROs show stronger clustering than other galaxies at the same magnitudes. The ,(,) amplitudes are best-fitted by models in which the EROs have a comoving correlation radius r0, 12.5 ± 1.2 h,1 Mpc, or r0, 21.4 ± 2.0 h,1 Mpc in a stable clustering model. We find a 40-arcsec diameter overdensity of 10 EROs, centred on the Chandra X-ray source (and ERO) XID:58. On the basis of colours we estimate that about seven, including XID:58, belong to a cluster of EROs at z, 1.5. The 942-ks Chandra survey detected 73 X-ray sources in the area of our ERO sample, 17 of which coincide with EROs. Of these sources, 13 have X-ray properties indicative of obscured active galactic nuclei (AGN), while the faintest four may be starbursts. In addition, we find evidence that Chandra sources and EROs are positively cross-correlated at non-zero (,2,20 arcsec) separations, implying that they tend to trace the same large-scale structures. In conclusion, these findings appear consistent with a scenario where EROs are the z > 1 progenitors of elliptical/S0 galaxies, some forming very early as massive spheroids, which are strongly clustered and may evolve via an AGN phase, others more recently from mergers of disc galaxies. [source]