Tracing High Redshift Starformation in the Current and Next Generation of Radio Surveys

The current deepest radio surveys detect hundreds of sources per square degree below 0.1mJy. There is a growing consensus that a large fraction of these sources are dominated by star formation although the exact proportion has been debated in the literature. However, the low luminosity of these galaxies at most other wavelengths makes determining the nature of individual sources difficult. If future, deeper surveys performed with the next generation of radio instrumentation are to reap high scientific reward we need to develop reliable methods of distinguishing between radio emission powered by active galactic nuclei (AGN) and that powered by star formation. In particular, we believe that such discriminations should be based on purely radio, or relative to radio, diagnostics. These diagnostics include radio morphology, radio spectral index, polarisation, variability, radio luminosity and flux density ratios with non-radio wavelengths e.g. with different parts of the infrared (IR) regime. We discuss the advantages and limitations of these various diagnostics methods with current and future surveys. However, weeding AGN out of deep radio surveys can already provide several insights into the star formation at high redshift. As well as reproducing the well known rise with redshift in the comoving star formation rate density, we also see evidence for the continued dominance of LIRGs and ULIRGs to the total star forming budget across redshifts 1-3. Additionally, while we see that the IR-radio relation for star forming galaxies does hold to high redshifts (z>1) there is a mild deviation depending on the IR waveband used and the range of IR SEDs found. We will discuss the possible reasons behind this change in properties.Comment: 6 pages, 6 figures. Panoramic Radio Astronomy: Wide-field 1-2 GHz research on galaxy evolution - PRA2009 Groningen, the Netherlands June 02-05, 200

Revealing the physics and evolution of galaxies and galaxy clusters with SKA continuum surveys

In this chapter we provide an overview of the science enabled by radio continuum surveys in the SKA era, focusing on galaxy/galaxy cluster physics and evolution studies, and other relevant continuum science in the > 2020 scientific framework. We outline a number of reference radio-continuum surveys for SKA1 that can address such topics, and comprehensively discuss the most critical science requirements that we have identified. We highlight what should be achieved by SKA1, to guarantee a major leap forwards with respect to the pre-SKA era, considering the science advances expected in the coming years with existing and upcoming telescopes (JVLA, LOFAR, eMERLIN, and the three SKA precursors: MWA, ASKAP and MeerKAT). In this exercise we take in due account also the other waveband facilities coming online at the same time (e.g. Euclid, LSST, etc.), which tackle overlapping scientific goals, but in a different manner. In this respect particular attention has been payed to ensure that the proposed reference surveys are able to exploit the existing synergies with such facilities, so as to generate strong involvement from all astronomical communities, and leave a lasting legacy value. It is clear that a certain degree of freedom is allowed to some of the observational parameters. We believe it is very important to best fine-tune such parameters taking into proper account existing commensalities with SKA1 surveys addressing other science areas (HI galaxy science, magnetism, cosmology)

Optical and near-IR spectroscopy of candidate red galaxies in two z~2.5 proto-clusters

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.Comment: 17 pages, 14 figures, accepted for publication in Astronomy and Astrophysic

Impact of Prospective Screening for Multiple Endocrine Neoplasia Type 2

Prospective annual screening for hereditary medullary thyroid carcinoma (MTC) in the J-kindred, currently a 117-member family with multiple endocrine neoplasia type 2A, began in 1969. During the initial screening, 12 patients were found to have MTC. Subsequent screening has detected C-cell abnormalities (C-cell hyperplasia or microscopic MTC) in 22 of 23 addilional family members thyroidectomized for abnormal calcium- or pentagastrin-provocative calcitonin (CT) test results. Seven of the initial 12 patients thyroidectomized in 1970 to 1971 and 19 of 23 individuals thyroidectomized since 1971 remain disease-free by all criteria; three patients thyroidectomized since 1971 have had clearly abnormal serum CT measurements on one or more provocative tests. The significance of these abnormal test results is unclear because normal values were obtained when the samples were measured in another CT radioimmunoassay. Urine catecholamine abnormalities have been detected in 19 family members since 1969, resulting in ten bilateral and eight unilateral adrenalectomies. Four of the patients with initial unilateral adrenalectomy required reoperation for a pheochromocytoma in the contralateral gland nine to 13 years later. Hyperparathyroidism has not been observed in any of the family members with early C-cell disease. We conclude that prospective screening for hereditary MTC predicts histologic C-cell abnormalities in affected individuals, and follow-up of these patients provides support for the conclusion that early thyroidectomy is curative in most patients

Identifying the first generation of radio powerful AGN in the Universe with the SKA

One of the most challenging and exciting subjects in modern astrophysics is that of galaxy formation at the epoch of reionisation. The SKA, with its revolutionary capabilities in terms of frequency range, resolution and sensitivity, will allow to explore the first Gyr of structure formation in the Universe, in particular, with the detection and study of the earliest manifestations of the AGN phenomenon. The tens of QSOs that are currently known out to the highest redshifts (z 7), many of them exhibiting powerful radio emission, imply that super-massive black holes can be grown on a very short timescale and support the existence of very high redshift (z &gt; 7) radio loud sources - sources that have so far escaped detection. Not only would such detections be paramount to the understanding of the earliest stages of galaxy evolution, they are necessary for the direct study of neutral hydrogen in the Epoch of Reionisation, through observations of the HI 21cm forest against such background sources. In order to understand how SKA and SKA1 observations can be optimised to reveal these earliest AGN, we have examined the effect of a hot CMB on the emission of powerful and young radio galaxies. By looking at the SKA1 capabilities, in particular in terms of wavelength coverage and resolution, we determine how the effects of "CMB-muting" of a radio loud source can be observationally minimised and how to identify the best highest-redshift radio candidates. Considering different predictions for the space density of radio loud AGN at such redshifts, we identify the survey characteristics necessary to optimize the detection and identification of the very first generation of radio loud AGN in the Universe

The SKA Mid-frequency All-sky continuum survey: Discovering the unexpected and transforming radio-astronomy

SKA is an instrument, not an experiment (Phil Diamond, Stellenbosch, 17 Feb 2014) We show that, in addition to specific science goals, there is a strong case for conducting an all-sky (i.e. the visible 3p steradians) SKA continuum survey which does not fit neatly into conventional science cases. History shows that the greatest scientific impact of most major telescopes (e.g., HST, VLA) lies beyond the original goals used to justify the telescope. The design of the telescope therefore needs to maximise the ultimate scientific productivity, in addition to achieving the specific science goals. In this chapter, we show that an all-sky continuum survey is likely to achieve transformational science in two specific respects

Characterizing the radio continuum emission from intense starburst galaxies

© 2016 The Authors Published by Oxford University Press on behalf of the Royal Astronomical Society.The intrinsic thermal (free-free) and non-thermal (synchrotron) emission components that comprise the radio continuum of galaxies represent unique, dust-free measures of star formation rates (SFR). Such high SFR galaxies will dominate the deepest current and future radio surveys. We disentangle the thermal and non-thermal emission components of the radio continuum of six ultraluminous infrared galaxies (LFIR &gt; 1012.5 L?) at redshifts of 0.2 = z = 0.5 and 22 IR selected galaxies. Radio data over a wide frequency range (0.8 &lt; ? &lt;10 GHz) are fitted with a star-forming galaxy model comprising of thermal and non-thermal components. The luminosities of both radio continuum components are strongly correlated to the 60 µm luminosity across many orders of magnitude (consistent with the far-IR to radio correlation). We demonstrate that the spectral index of the radio continuum spectral energy distribution is a useful proxy for the thermal fraction. We also find that there is an increase in mean and scatter of the thermal fraction with FIR to radio luminosity ratio which could be influenced by different time-scales of the thermal and non-thermal emission mechanisms