In the context of the VLA-COSMOS Deep project, additional VLA A array observations at 1.4 GHz were obtained for the central degree of the COSMOS field and combined with the existing data from the VLA-COSMOS Large project. A newly constructed Deep mosaic with a resolution of 2. 5 was used to search for sources down to 4σ with 1σ ≈ 12 μJy beam −1 in the central 50 × 50 . This new catalog is combined with the catalog from the Large project (obtained at 1. 5 × 1. 4 resolution) to construct a new Joint catalog. All sources listed in the new Joint catalog have peak flux densities of 5σ at 1. 5 and/or 2. 5 resolution to account for the fact that a significant fraction of sources at these low flux levels are expected to be slightly resolved at 1. 5 resolution. All properties listed in the Joint catalog, such as peak flux density, integrated flux density, and source size, are determined in the 2. 5 resolution Deep image. In addition, the Joint catalog contains 43 newly identified multi-component sources.

The HI 21 cm transition line is expected to be an important probe into the cosmic dark ages and epoch of reionization. Foreground source removal is one of the principal challenges for the detection of this signal. This paper investigates the extragalactic point source contamination and how accurately bright sources ( 1 Jy) must be removed in order to detect 21 cm emission with upcoming radio telescopes such as the Murchison Widefield Array (MWA). We consider the residual contamination in 21 cm maps and power spectra due to position errors in the sky-model for bright sources, as well as frequency independent calibration errors. We find that a source position accuracy of 0.1 arcsec will suffice for detection of the HI power spectrum. For calibration errors, 0.05 % accuracy in antenna gain amplitude is required in order to detect the cosmic signal. Both sources of subtraction error produce residuals that are localized to small angular scales, k ⊥ 0.05 Mpc −1 , in the two-dimensional power spectrum.

We present an analysis of the radio properties of large samples of Lyman Break Galaxies (LBGs) at z ∼ 3, 4, and 5 from the COSMOS field. The median stacking analysis yields a statistical detection of the z ∼ 3 LBGs (U-band dropouts), with a 1.4 GHz flux density of 0.90 ± 0.21µJy. The stacked emission is unresolved, with a size < 1", or a physical size < 8kpc. The total star formation rate implied by this radio luminosity is 31 ± 7 M ⊙ year −1 , based on the radio-FIR correlation in low redshift star forming galaxies. The star formation rate derived from a similar analysis of the UV luminosities is 17 M ⊙ year −1 , without any correction for UV dust attenuation. The simplest conclusion is that the dust attenuation factor is 1.8 at UV wavelengths. However, this factor is considerably ⋆ Based on observations in the COSMOS Legacy Survey including those taken on the HST, Keck, NRAO-VLA, Subaru, KPNO 4m, CTIO 4m, and CFHT 3.6m.-2smaller than the standard attenuation factor ∼ 5, normally assumed for LBGs. We discuss potential reasons for this discrepancy, including the possibility that the dust attenuation factor at z ≥ 3 is smaller than at lower redshifts. Conversely, the radio luminosity for a given star formation rate may be systematically lower at very high redshift. Two possible causes for a suppressed radio luminosity are: (i) increased inverse Compton cooling of the relativistic electron population due to scattering off the increasing CMB at high redshift, or (ii) cosmic ray diffusion from systematically smaller galaxies. The radio detections of individual sources are consistent with a radio-loud AGN fraction of 0.3%. One source is identified as a very dusty, extreme starburst galaxy (a 'submm galaxy').

The galaxy cluster Abell 3667 is an ideal laboratory to study the plasma processes in the intracluster medium (ICM). High resolution Chandra X-ray observations show a cold front in Abell 3667. At radio wavelengths, Abell 3667 reveals a double radio-relic feature in the outskirts of the cluster. These suggest multiple merger events in this cluster. In this paper, we analyze the substantial archival X-ray observations of Abell 3667 from Chandra X-ray Observatory and compare these with existing radio observations as well as state-of-the-art AMR (Adaptive Mesh Refinement) MHD cosmological simulations using Enzo. We have used two temperature map making techniques, Weighted Voronoi Tessellation and Adaptive Circular Binning, to produce the high resolution and largest field-of-view temperature maps of Abell 3667. These high fidelity temperature maps allow us to study the X-ray shocks in the cluster using a new 2-dimensional shock-finding algorithm. We have also estimated the Mach numbers from the shocks inferred from previous ATCA radio observations. The combined shock statistics from the X-ray and radio data are in agreement with the shock statistics in a simulated MHD cluster. We have also studied the profiles of the thermodynamic properties across the cold front using ∼ 447 ksec from the combined Chandra observations on Abell 3667. Our results show that the stability of the cold front in Abell 3667 can be attributed to the suppression of the thermal conduction across the cold front by a factor of ∼ 100 − 700 compared to the classical Spitzer value.