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Creators/Authors contains: "Kraan-Korteweg, R. C."

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  1. ABSTRACT

    We present six deep Near-InfraRed (JHKs) photometric catalogues of galaxies identified in six cluster candidates (VC02, VC04, VC05, VC08, VC10, and VC11) within the Vela Supercluster (VSCL) as part of our efforts to learn more about this large supercluster, which extends across the zone of avoidance (ℓ = 272.°5 ± 20°, b = ±10°, at cz ∼ 18 000 km s−1). The observations were conducted with the InfraRed Survey Facility (IRSF), a 1.4-m telescope situated at the South African Astronomical Observatory (SAAO) in Sutherland. The images in each cluster cover $\sim 80{{\ \rm per\ cent}}$ of their respective Abell radii. We identified a total number of 1715 galaxies distributed over the six cluster candidates, of which only $\sim 15{{\ \rm per\ cent}}$ were previously known. We study the structures and richnesses of the six clusters out to the cluster-centric completeness radius of rc < 1.5 Mpc and magnitude completeness limit of $K_s^o\lt 15{_{.}^{\rm m}}5$, using their iso-density contour maps and radial density profiles. The analysis shows VC04 to be the richest of the six. It is a massive cluster comparable to the Coma and Norma clusters, although its velocity dispersion, σv = 455  km s−1, seems rather low for a rich cluster. VC02 and VC05 are found to be relatively rich clusters while VC08 is rather poor. Also, VC05 has the highest central number density among the six. VC11 is an intermediate cluster that contains two major subclusters while VC10 has a filament-like structure and is likely not to be a cluster after all.

     
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  2. MeerKAT’s large number (64) of 13.5 m diameter antennas, spanning 8 km with a densely packed 1 km core, create a powerful instrument for wide-area surveys, with high sensitivity over a wide range of angular scales. The MeerKAT Galaxy Cluster Legacy Survey (MGCLS) is a programme of long-track MeerKAT L -band (900−1670 MHz) observations of 115 galaxy clusters, observed for ∼6−10 h each in full polarisation. The first legacy product data release (DR1), made available with this paper, includes the MeerKAT visibilities, basic image cubes at ∼8″ resolution, and enhanced spectral and polarisation image cubes at ∼8″ and 15″ resolutions. Typical sensitivities for the full-resolution MGCLS image products range from ∼3−5 μJy beam −1 . The basic cubes are full-field and span 2° × 2°. The enhanced products consist of the inner 1.2° × 1.2° field of view, corrected for the primary beam. The survey is fully sensitive to structures up to ∼10′ scales, and the wide bandwidth allows spectral and Faraday rotation mapping. Relatively narrow frequency channels (209 kHz) are also used to provide H  I mapping in windows of 0 <  z  < 0.09 and 0.19 <  z  < 0.48. In this paper, we provide an overview of the survey and the DR1 products, including caveats for usage. We present some initial results from the survey, both for their intrinsic scientific value and to highlight the capabilities for further exploration with these data. These include a primary-beam-corrected compact source catalogue of ∼626 000 sources for the full survey and an optical and infrared cross-matched catalogue for compact sources in the primary-beam-corrected areas of Abell 209 and Abell S295. We examine dust unbiased star-formation rates as a function of cluster-centric radius in Abell 209, extending out to 3.5 R 200 . We find no dependence of the star-formation rate on distance from the cluster centre, and we observe a small excess of the radio-to-100 μm flux ratio towards the centre of Abell 209 that may reflect a ram pressure enhancement in the denser environment. We detect diffuse cluster radio emission in 62 of the surveyed systems and present a catalogue of the 99 diffuse cluster emission structures, of which 56 are new. These include mini-halos, halos, relics, and other diffuse structures for which no suitable characterisation currently exists. We highlight some of the radio galaxies that challenge current paradigms, such as trident-shaped structures, jets that remain well collimated far beyond their bending radius, and filamentary features linked to radio galaxies that likely illuminate magnetic flux tubes in the intracluster medium. We also present early results from the H  I analysis of four clusters, which show a wide variety of H  I mass distributions that reflect both sensitivity and intrinsic cluster effects, and the serendipitous discovery of a group in the foreground of Abell 3365. 
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