In a previous paper (Paper I, Franzen et al., 2011MNRAS.415.2699F), the observational, mapping and source-extraction techniques used for the Tenth Cambridge (10C) Survey of Radio Sources were described. Here, the first results from the survey, carried out using the Arcminute Microkelvin Imager Large Array (LA) at an observing frequency of 15.7GHz, are presented. The survey fields cover an area of ~27deg^2^ to a flux-density completeness of 1mJy. Results for some deeper areas, covering ~12deg^2^, wholly contained within the total areas and complete to 0.5mJy, are also presented. The completeness for both areas is estimated to be at least 93 per cent. The 10C survey is the deepest radio survey of any significant extent (>~0.2deg^2^) above 1.4GHz.
The 7C survey of radio sources is being made with the Cambridge Low-Frequency Synthesis Telescope at 151MHz, with an angular resolution of 70x70cosec{delta}.arcsec^2^. We present the results from one part of of this survey covering 0.144sr in two areas of sky centred at RA=10h28min, DE=41{deg} and RA=06h28min, DE=45{deg} and reaching a limiting flux density of 50mJy. A list of the positions, flux densities and angular sizes of 4723 sources is presented; the position errors are in the range 1-3arcsec for sources with flux densities greater than 500mJy, and the flux density errors are typically 18mJy. About 10 per cent of the sources have apparent angular sizes greater than 60arcsec. The derived source counts are as accurate as those presently available at 405 and 1400MHz and show similar behaviour; in particular the convergence slopes are the same. The median spectral index between 151 and 408MHz remains constant at ~0.9 between 10 and 0.5Jy at 151MHz.
The 6th Cambridge Survey of radio sources covers most of the sky north of Dec>30{deg} with an angular resolution of 4.2x4.2cosec{delta} arcmin^2^ and a limiting flux density of 120mJy at 151MHz. This paper, the first of a series, describes the telescope and the methods used to produce the survey maps and source list, and presents maps of a circular area of radius 10{deg} centered on the North Celestial Pole and a list of 1761 sources north of {delta}>+80{deg}.
The 6th Cambridge survey of radio sources covers most of the sky north of +30{deg} with an angular resolution of 4.2x4.2cosec{delta}arcmin^2^ and reaches a limiting flux density of 190mJy at 151MHz in the present zone. In this paper the methods used to produce the survey maps from a non-tracking telescope operating at declinations other than the north celestial pole are described: this forms the basis for all future papers in the series. Maps of a high galactic latitude region are presented 30{deg}<{delta}<51{deg}, 08h30m<{alpha}<17h30m, together with a list of 8278 sources in the 2030deg^2^ covered. A source count over the range 200mJy<S(151)<100Jy is derived.
The 6th Cambridge Survey of radio sources covers most of the sky north of 30{deg} with an angular resolution of 4.2x4.2cosec{delta} arcmin^2^ and a limiting flux density of 160mJy at 151MHz, with completeness achieved at 600mJy. This paper presents 8749 sources in the 1950deg^2^ region 48{deg}<{delta}<68{deg}, 05h25m<{alpha}<18h17m.
The 6th Cambridge Survey of radio sources covers most of the sky north of 30{deg} with an angular resolution of 4.2x4.2cosec{delta} arcmin^2^ and a limiting flux density of 160mJy at 151MHz, with completeness achieved at 600mJy. This zone covers the declinations 67{deg}--82{deg} region 48{deg}<{delta}<68{deg}, 05h25m<{alpha}<18h17m.
The 6th Cambridge Survey of radio sources covers most of the sky north of 30{deg} with an angular resolution of 4.2x4.2cosec{delta} arcmin^2^ and a limiting flux density of 160mJy at 151MHz, with completeness achieved at 600mJy. This paper presents, in the declination ranges 48{deg}<{delta}<68{dec} the zones Va (01h34<{alpha}<06h14) and Vb (17h16<{alpha}<20h24)
With the advent of the Legacy Survey of Space and Time, time-domain astronomy will be faced with an unprecedented volume and rate of data. Real-time processing of variables and transients detected by such large-scale surveys is critical to identifying the more unusual events and allocating scarce follow-up resources efficiently. We develop an algorithm to identify these novel events within a given population of variable sources. We determine the distributions of magnitude changes (dm) over time intervals (dt) for a given passband f, p_f_^(dm|dt)^, and use these distributions to compute the likelihood of a test source being consistent with the population or being an outlier. We demonstrate our algorithm by applying it to the DECam multiband time-series data of more than 2000 variable stars identified by Saha+ (2019, J/ApJ/874/30) in the Galactic Bulge that are largely dominated by long-period variables and pulsating stars. Our algorithm discovers 18 outlier sources in the sample, including a microlensing event, a dwarf nova, and two chromospherically active RS CVn stars, as well as sources in the blue horizontal branch region of the color-magnitude diagram without any known counterparts. We compare the performance of our algorithm for novelty detection with the multivariate Kernel Density Estimator and Isolation Forest on the simulated PLAsTiCC data set. We find that our algorithm yields comparable results despite its simplicity. Our method provides an efficient way for flagging the most unusual events in a real-time alert-broker system.
We present the CIDAUCMYale (Centro de Investigaciones de Astronomia, Universidad Complutense de Madrid, and Yale University) Survey (CUYS) for H{alpha}+[NII] 6549, 6584{AA} emission-line galaxies (ELGs) using objective-prism spectra. The most important properties of a catalogue with 427 entries and significant subsets are analysed. The complete sample contains 183 statistically confirmed ELGs in a sky area of 151deg^2^ and redshift up to 0.14. We determine the parameters of the H{alpha} luminosity function using the H{alpha}+[NII] flux directly measured on the ELG spectra in this sample, and the star formation rate density derived is in agreement with values reported in the literature.
