arXiv subjects

K. Kellermann

Publications and source records attributed to K. Kellermann.

3 recordsLinked to original sources

arXiv2018

The Radio Synchrotron Background: Conference Summary and Report

We summarize the radio synchrotron background workshop that took place July 19-21, 2017 at the University of Richmond. This first scientific meeting dedicated to the topic was convened because current measurements of the diffuse radio monopole reveal a surface brightness that is several times higher than can be straightforwardly explained by known Galactic and extragalactic sources and processes, rendering it by far the least well understood photon background at present. It was the conclusion of a majority of the participants that the radio monopole level is at or near that reported by the ARCADE 2 experiment and inferred from several absolutely calibrated zero level lower frequency radio measurements, and unanimously agreed that the production of this level of surface brightness, if confirmed, represents a major outstanding question in astrophysics. The workshop reached a consensus on the next priorities for investigations of the radio synchrotron background.

astro-ph.HE↗

arXiv2009

VLA survey of the CDFS: the nature of faint radio sources

We present the multiwavelength properties of 266 cataloged radio sources identified with 20 and 6 cm VLA deep observations of the CDFS at a flux density limit of 42 μJy at the field centre at 1.4 GHz. These new observations probe the faint end of both the star formation and radio galaxy/AGN population. X-ray data, including upper limits, turn out to be a key factor in establishing the nature of faint radio sources. We find that, while the well-known flattening of the radio number counts below 1 mJy is mostly due to star forming galaxies, these sources and AGN make up an approximately equal fraction of the sub--millijansky sky, contrary to some previous results. We have also uncovered a population of distant AGN systematically missing from many previous studies of sub-millijansky radio source identifications. The AGN include radio galaxies, mostly of the low-power, Fanaroff-Riley I type, and a significant radio-quiet component, which amounts to approximately one fifth of the total sample. We also find that radio detected, X-ray AGN are not more heavily obscured than the X-ray detected AGN. This argues against the use of radio surveys as an efficient way to search for the missing population of strongly absorbed AGN.

astro-ph.CO↗

arXiv2003

The manifold spectra and morphologies of EROs

Deep VLT optical spectroscopy, HST+ACS (GOODS) imaging and VLA observations are used to unveil the nature of a complete sample of 47 EROs with R-Ks>5 and Ks<20. The spectroscopic redshift completeness is 62%. Morphological classification was derived for each ERO through visual inspection and surface brightness profile fitting. Three main ERO morphological types are found: E/S0 galaxies (30-37%), spiral-like (24-46%) and irregular systems (17-39%). The only ERO detected in the radio is likely to host an obscured AGN. The average radio luminosity of the star-forming EROs undetected in the radio implies star formation rates of the order of 33 Msun yr^-1. The colors, redshifts and masses of the E/S0 galaxy subsample imply a minimum formation redshift z_f \sim 2. With this z_f there is enough time to have old and massive stellar spheroids already assembled at z \sim 1. We verify that the R-Ks vs. J-Ks color diagram is efficient in segregating old and dusty-star-forming EROs.

astro-ph↗