Reinaldo Braun

We describe the APERture Tile In Focus (Apertif) system, a phased array feed (PAF) upgrade of the Westerbork Synthesis Radio Telescope that transforms this telescope into a high-sensitivity, wide-field-of-view L -band imaging and transient survey instrument. Using novel PAF technology, up to 40 partially overlapping beams are formed on the sky simu...

We describe the APERture Tile In Focus (Apertif) system, a phased array feed (PAF) upgrade of the Westerbork Synthesis Radio Telescope which has transformed this telescope into a high-sensitivity, wide field-of-view L-band imaging and transient survey instrument. Using novel PAF technology, up to 40 partially overlapping beams can be formed on the...

We report the discovery of a new 21-cm H i absorption system using commissioning data from the Boolardy Engineering Test Array of the Australian Square Kilometre Array Pathfinder (ASKAP). Using the 711.5–1015.5 MHz band of ASKAP we were able to conduct a blind search for the 21-cm line in a continuous redshift range between z = 0.4 and 1.0, which h...

This paper describes the system architecture of a newly constructed radio telescope - the Boolardy Engineering Test Array, which is a prototype of the Australian Square Kilometre Array Pathfinder telescope. Phased array feed technology is used to form multiple simultaneous beams per antenna, providing astronomers with unprecedented survey speed. Th...

While most ram pressure studies have focused on ram pressure stripping in galaxy clusters, we devise a novel approach based on a kinematic measurement of ram pressure perturbations in H i velocity fields for intergalactic material (IGM) densities and relative velocities that are one to two orders of magnitude lower than in galaxies showing ram pres...

We study the spatially resolved Radio Continuum-Star Formation Rate (RC-SFR) relation using state-of-the-art star-formation (SF) tracers in a sample of 17 THINGS galaxies. We use hybrid Sigma_SFR maps (GALEX FUV plus Spitzer 24 mu), RC maps at 22/18 cm from the WSRT SINGS survey, and H-alpha maps to correct for thermal RC emission. We compare azimu...

We consider the most commonly occurring circumstances which apply to galaxies, namely membership in galaxy groups of about 1013 h−1 M⊙ total mass, and estimate the accompanying physical conditions of intergalactic medium (IGM) density and the relative galaxy–IGM space velocity. We then investigate the dynamical consequences of such a typical galaxy...

We have carried out deep, high velocity resolution, interferometric Galactic H i-21 cm absorption spectroscopy towards 32 compact extragalactic radio sources with the Giant Metrewave Radio Telescope (GMRT) and the Westerbork Synthesis Radio Telescope (WSRT). The optical depth spectra for most sources have root-mean-square noise values ≲10−3 per 1 k...

Nuclear stellar cusps are defined as central excess light component in the stellar light profiles of galaxies and are suggested to be stellar relics of intense compact starbursts in the central ~100-500 pc region of gas-rich major mergers. Here we probe the build-up of nuclear cusps during the actual starburst phase for a complete sample of Luminou...

LOFAR, the LOw-Frequency ARray, is a new-generation radio interferometer constructed in the north of the Netherlands and across europe. Utilizing a novel phased-array design, LOFAR covers the largely unexplored low-frequency range from 10-240 MHz and provides a number of unique observing capabilities. Spreading out from a core located near the vill...

Detection of the trace neutral fraction of hydrogen gas that stretches between the nearby Andromeda and Triangulum galaxies has allowed resolved spectral imaging of this elusive intergalactic medium. See Letter p.224

Cassiopeia A was observed using the Low-Band Antennas of the LOw Frequency ARray (LOFAR) with high spectral resolution. This allowed a search for radio recombination lines (RRLs) along the line-of-sight to this source. Five carbon-alpha RRLs were detected in absorption between 40 and 50 MHz with a signal-to-noise ratio of > 5 from two independent L...

We present the results of the most sensitive and comprehensive survey yet undertaken for radio pulsars and fast transients in the Andromeda galaxy (M31) and its satellites, using the Westerbork Synthesis Radio Telescope (WSRT) at a central frequency of 328 MHz. We used the WSRT in a special configuration called 8gr8 (eight-grate) mode, which provid...

Using the Westerbork Synthesis Radio Telescope (WSRT) at 328 MHz, we have performed the deepest search yet undertaken to detect millisecond radio bursts from neutron stars in the Andromeda galaxy (M31). This search has identified a number of tantalizing candidates, whose dispersion measures suggest that they may potentially originate in M31. Here w...

We present the results of the most sensitive and comprehensive survey yet undertaken for radio pulsars and fast transients in the Andromeda galaxy (M31) and its satellites, using the Westerbork Synthesis Radio Telescope (WSRT) at a central frequency of 328 MHz. We used the WSRT in a special configuration called 8gr8 (eight-grate) mode, which provid...

We develop a general framework for quantifying the many different contributions to the noise budget of an image made with an array of dishes or aperture array stations. Each noise contribution to the visibility data is associated with a relevant correlation timescale and frequency bandwidth so that the net impact on a complete observation can be as...

We present an analysis of the dust and gas in Andromeda, using Herschel images sampling the entire far-infrared peak. We fit a modified-blackbody model to ~4000 quasi-independent pixels with spatial resolution of ~140pc and find that a variable dust-emissivity index (beta) is required to fit the data. We find no significant long-wavelength excess a...

Context. We have obtained Herschel images at five wavelengths from 100 to 500 mu m of a similar to 5.5 x 2.5 degree area centred on the local galaxy M31 (Andromeda), our nearest neighbour spiral galaxy, as part of the Herschel guaranteed time project "HELGA". The main goals of HELGA are to study the characteristics of the extended dust emission, fo...

We aim to summarize the current state of knowledge regarding Galactic Faraday rotation in an all-sky map of the Galactic Faraday depth. For this we have assembled the most extensive catalog of Faraday rotation data of compact extragalactic polarized radio sources to date. In the map making procedure we use a recently developed algorithm that recons...

Particle cascades initiated by ultra-high energy (UHE) neutrinos in the lunar regolith will emit an electromagnetic pulse with a time duration of the order of nanoseconds through a process known as the Askaryan effect. It has been shown that in an observing window around 150 MHz there is a maximum chance to detect this radiation with radio telescop...

In this paper, reprocessed data is presented that was originally observed for the HI Parkes All Sky Survey (HIPASS). The data is described in detail in Barnes et al. (2001MNRAS.322..486B). HIPASS provides complete coverage of the region that has been observed for the Westerbork Virgo Filament HI Survey (WVFS), presented in accompanying papers, and...

We report the discovery of a threshold in the HI column density of Galactic gas clouds below which the formation of the cold phase of HI is inhibited. This threshold is at N HI = 2 × 10 20 per cm 2 ; sightlines with lower HI column densities have high spin temperatures (median T s ∼ 1800 K), indicating low fractions of the cold neutral medium (CNM)...

Observations of neutral hydrogen can provide a wealth of information about the distribution and kinematics of galaxies. To detect HI beyond the ionisation edge of galaxy disks, column density sensitivities have to be achieved that probe the regime of Lyman limit systems. Typically HI observations are limited to a brightness sensitivity of NHI~10^19...

We report on the results of observations in the CO(1–0) transition of a complete sample of Southern, intermediate-redshift (z= 0.2–0.5) ultraluminous infrared galaxies (ULIRGs) using the Mopra 22-m telescope. The 11 ULIRGs with LFIR > 1012.5 L⊙ south of δ=−12° were observed with integration times that varied between 5 and 24 h. Four marginal detect...

We report the discovery of a threshold in the HI column density of Galactic gas clouds below which the formation of the cold phase of HI is inhibited. This threshold is at $N_{HI} = 2 \times 10^{20}$ per cm$^{2}$; sightlines with lower HI column densities have high spin temperatures (median $T_s \sim 1800$ K), indicating low fractions of the cold n...

To obtain the highest possible brightness sensitivity in cross-correlations, the WSRT (Westerbork Synthesis Radio Telescope) was configured to simulate a large filled aperture in projection. Twelve of the 14 WSRT 25m telescopes were positioned at regular intervals of 144m. A deep fully-sampled survey of the galaxy filament joining the Local Group t...

Context. Observations of neutral hydrogen can provide a wealth of information about the kinematics of galaxies. To learn more about the large-scale structures and accretion processes, the extended environment of galaxies have to be observed. Numerical simulations predict a cosmic web of extended structures and gaseous filaments. Aims: To observe th...

The extended environment of galaxies contains a wealth of information about the formation and life cycle of galaxies which are regulated by accretion and feedback processes. Observations of neutral hydrogen are routinely used to image the high brightness disks of galaxies and to study their kinematics. Deeper observations will give more insight int...

Observations of neutral hydrogen can provide a wealth of information about the kinematics of galaxies. To learn more about the large scale structures and accretion processes, the extended environment of galaxies have to be observed. Numerical simulations predict a cosmic web of extended structures and gaseous filaments. To observe the direct vicini...

Context. Ultra-high energy (UHE) neutrinos and cosmic rays initiate particle cascades underneath the Moon's surface. These cascades have a negative charge excess and radiate Cherenkov radio emission in a process known as the Askaryan effect. The optimal frequency window for observation of these pulses with radio telescopes on the Earth is around 15...

Numerical simulations predict that galaxies and clusters in the Local Volume are connected by extended diffuse filaments of gas. Although most of this gas is ionised, the peaks of this Cosmic Web should be detectable in HI 21cm emission at column densities that probe those of Lyman Limit systems. In a previous work we have defined a list of HI dete...

Ultra-high energy (UHE) neutrinos and cosmic rays initiate particle cascades underneath the Moon's surface. These cascades have a negative charge excess and radiate Cherenkov radio emission in a process known as the Askaryan effect. The optimal frequency window for observation of these pulses with radio telescopes on the Earth is around 150 MHz. By...

A sample of large northern Spitzer Infrared Nearby Galaxies Survey (SINGS) galaxies was recently observed with the Westerbork Synthesis Radio Telescope (WSRT) at 1300-1760 MHz. In Paper II of this series, we described sensitive observations of the linearly polarized radio continuum emission in this WSRT-SINGS galaxy sample. Here we explore the syst...

Results. The disk of M 31 warps from 25 kpc outwards and becomes more inclined with respect to our line of sight. Newtonian dynamics without a dark matter halo provide a very poor fit to the rotation curve. In the framework of modified Newtonian dynamic (MOND) however the 21-cm rotation curve is well fitted by the gravitational potential traced by...

Aims: We test cosmological models of structure formation using the rotation curve of the nearest spiral galaxy, M 31, determined using a recent deep, full-disk 21-cm imaging survey smoothed to 466 pc resolution. Methods: We fit a tilted ring model to the HI data from 8 to 37 kpc and establish conclusively the presence of a dark halo and its density...

We test cosmological models of structure formation using the rotation curve of the nearest spiral galaxy, M31, determined using a recent deep, full-disk 21-cm imaging survey smoothed to 466 pc resolution. We fit a tilted ring model to the HI data from 8 to 37 kpc. The disk of M31 warps from 25 kpc outwards and becomes more inclined with respect to...

Particle cascades initiated by ultrahigh energy neutrinos in the lunar regolith will emit an electromagnetic pulse with a time duration of the order of nanoseconds through a process known as the Askaryan effect. It has been shown that in an observing window around 150 MHz there is a maximum chance for detecting this radiation with radio telescopes...

Particle cascades initiated by ultrahigh energy neutrinos in the lunar regolith will emit an electromagnetic pulse with a time duration of the order of nanoseconds through a process known as the Askaryan effect. It has been shown that in an observing window around 150 MHz there is a maximum chance for detecting this radiation with radio telescopes...

Particle cascades initiated by ultra-high energy (UHE) neutrinos in the lunar regolith will emit an electromagnetic pulse with a time duration of the order of nano seconds through a process known as the Askaryan effect. It has been shown that in an observing window around 150 MHz there is a maximum chance for detecting this radiation with radio tel...

We show that at wavelengths comparable to the length of the shower produced by an Ultra-High Energy cosmic ray or neutrino, radio signals are an extremely efficient way to detect these particles. First results are presented of an analysis of 20 hours of observation data for NuMoon project using the Westerbork Synthesis Radio Telescope to search for...

Observations of intergalactic neutral hydrogen can provide a wealth of information about structure and galaxy formation, potentially tracing accretion and feedback processes on Mpc scales. Below a column density of NHI ~ 10^19 cm-2, the "edge" or typical observational limit for HI emission from galaxies, simulations predict a cosmic web of extended...

Context. Reports on a transient source about 1.25 ◦ south of the Galactic Centre motivated these follow-up observations with the WSRT and the reinvestigation of archival VLA data. The source GCRT J1745-3009 was detected during a 2002 Galactic Centre monitoring programme with the VLA at 92 cm by five powerful 10-min bursts with a 77-min recurrence w...

We have undertaken a deep, wide-field H I imaging survey of M31, reaching a maximum resolution of about 50 pc and 2 km s −1 across a 95×48 kpc region. The H I mass and brightness sensitivity at 100 pc resolution for a 25 km s −1 wide spectral feature is 1500 M ⊙ and 0.28 K. Our study reveals ubiquitous H I self-opacity features, discernible in the...

Since 2004 we have been carrying out a pulsar survey of the Cygnus region with the Westerbork Synthesis Radio Telescope (WSRT) at a frequency of 328 MHz. The survey pioneered a novel interferometric observing mode, termed 8gr8 (eight-grate), whereby multiple simultaneous digital beams provide high sensitivity over a large field of view. Since the C...

We present an initial look at the far-infrared-radio correlation within the star-forming disks of four nearby, nearly face-on galaxies (NGC 2403, NGC 3031, NGC 5194, and NGC 6946). Using Spitzer MIPS imaging, observed as part of the Spitzer Infrared Nearby Galaxies Survey (SINGS), and Westerbork Synthesis Radio Telescope (WSRT) radio continuum data...

Using data obtained for 12 galaxies as part of the Spitzer Infrared Nearby Galaxies Survey (SINGS) and the Westerbork Synthesis Radio Telescope (WSRT) SINGS radio continuum survey, we study how star formation activity affects the far-infrared-radio correlation within galaxies by testing a phenomenological model that describes the radio image as a s...

Green Bank Telescope 21 cm observations have revealed a faint, yet extensive H I cloud population surrounding the Andromeda galaxy (M31). The newfound objects are likely analogs to the high-velocity H I clouds seen around the Milky Way. At least 20 discrete features are detected within 50 kpc of the M31 disk, with radial velocities that are compara...

The future of cm and m-wave astronomy lies with the Square Kilometre Array (SKA), a telescope under development by a consortium of 17 countries. The SKA will be 50 times more sensitive than any existing radio facility. A majority of the key science for the SKA will be addressed through large-area imaging of the Universe at frequencies from 300MHz t...

We show that at wavelengths comparable to the length of the shower produced by an Ultra-High Energy cosmic ray or neutrino, radio signals are an extremely efficient way to detect these particles. First results are presented of an analysis of 20 hours of observation data for NuMoon project using the Westerbork Synthesis Radio Telescope to search for...

The NuMoon project uses the Westerbork Synthesis Radio Telescope to search for short radio pulses from the Moon. These pulses are created when an ultra high energy cosmic ray or neutrino initiates a particle cascade inside the Moon's regolith. The cascade has a negative charge excess and moves faster than the local speed of light, which causes cohe...

1. Coordenacao de Doencas Transmitidas por Vetores, Servico de Vigilância Sanitaria, Ministerio da Saude, Brasilia, DF. 2. Secr etaria Municipal de Saude de Belem, Belem, PA. 3. Departamento de Parasitologia, Servico de Referencia Nacional em Filariose, Centro de Pesquisas Aggeu Magalhaes, Fundacao Oswal do Cruz, Recife, PE. 4. Instituto de Ciencia...

With sensitive HI observations of a large area around the Andromeda Galaxy (M31) with the Effelsberg telescope and high-resolution observations with the WSRT we could show that M31 is surrounded by a population of high-velocity clouds (HVCs). The observed spatial distribution and HI mass spectrum of the HVCs are in agreement with CDM structure form...

Multiple independent lines of evidence demonstrate that the surface area subtended by atomic hydrogen at column densities near 10^17 cm^-2 exceeds that seen at 10^19 cm^-2 by about a factor of 30. Intervening column densities are rarely encountered because of ionization in the intergalactic radiation field. Although at the limits of current technol...

In this proposal we request time with the interim CABB system to search for molecular gas in high redshift radio galaxies. We will use the 7mm system to search for the CO(2-1) emission line from the most distant known radio galaxy (z=5.2) as well as the Spiderweb radio galaxy (z=2.2) which is extremely well-studied in other wavelength bands. These...

Context.Inadequacies in the knowledge of the primary beam response of current interferometric arrays often form a limitation to the image fidelity, particularly when “mosaicing” over multiple telescope pointings.Aims.We hope to overcome these limitations by constructing a frequency-resolved, full-polarization empirical model for the primary beam of...

We present results on the interstellar medium (ISM) properties of 29 galaxies based on a comparison of Spitzer far-infrared and Westerbork Synthesis Radio Telescope radio continuum imagery. Of these 29 galaxies, 18 are close enough to resolve at �1 kpc scales at 70 µm and 22 cm. We extend the Murphy et al. (2006a,b) approach of smoothing infrared i...

We present results on the ISM properties of 29 galaxies based on a comparison of Spitzer far-infrared and Westerbork Synthesis Radio Telescope radio continuum imagery. Of these 29 galaxies, 18 are close enough to resolve at ≾ to 1 kpc scales at 70 µm and 22 cm. We extend the approach of our earlier work of smoothing infrared images to approximate c...

We noticed an error in the coefficient of equation (3); the correct equation is((taucool)/yr)~5.7×107(nu/GHz)-1/2(B/muG)1/2((UB+Urad)/(10-12 ergs cm-3))-1. (1)This did not impact the results or conclusions made in the rest of the text. All calculations using this equation were in fact correct.

We present robust decompositions of the diffuse and discrete components of ionized hydrogen in a sample of 11 nearby spiral galaxies, spanning a wide range of star formation rate and Hubble type. Traditionally, H II region populations have been interpreted through power-law fits of the Hα luminosity function (H II LF). Here we instead compare the m...

Inadequacies in the knowledge of the primary beam response of current interferometric arrays often form a limitation to the image fidelity. We hope to overcome these limitations by constructing a frequency-resolved, full-polarization empirical model for the primary beam of the Westerbork Synthesis Radio Telescope (WSRT). Holographic observations, s...

The future of cm and m-wave astronomy lies with the Square Kilometre Array (SKA), a telescope under development by a consortium of 17 countries that will be 50 times more sensitive than any existing radio facility. Most of the key science for the SKA will be addressed through large-area imaging of the Universe at frequencies from a few hundred MHz...

We present images of NGC 7331 obtained with GALEX and Spitzer, tracing UV and IR signatures of star formation. NGC 7331's morphology at 8-850 mu m is dominated by a central dust ring. This structure is a vigorous site of star formation (hosting one-third of the present activity) but remains inconspicuous in our GALEX UV imagery. Radial profile anal...

We present an initial look at the far-infrared–radio correlation within the starforming disks of four nearby, nearly face–on galaxies (NGC 2403, NGC3031, NGC5194, and NGC6946). Using Spitzer MIPS imaging and WSRT radio continuum data, we are able to probe variations in the logarithmic 70 μm/22 cm (q70) flux density ratios across each disk at sub–kp...

In the last few years the realization has emerged that the universal baryons are almost equally distributed by mass in three components: (1) galactic concentrations, (2) a warm-hot intergalactic medium (WHIM) and (3) a diffuse intergalactic medium. These three components are predicted by hydrodynamical simulations and are probed by QSO absorption l...

We are currently undertaking a survey to search for new pulsars and the recently found Rotating RAdio Transcients (RRATs) in the Cygnus OB complex. The survey uses the Westerbrok Synthesis Radio Telescope (WSRT) in a unique way called the 8gr8 mode, which gives it the best efficiency of any low-frequency wide-area survey. So far we have found a few...

High-velocity clouds (HVCs) are defined by their high radial velocities which are incompatible with a participation in the normal rotation of our Galaxy. They are observed mainly in the 21 cm line of neutral hydrogen. HVCs can be found all over the sky in the form of large complexes as well as compact, isolated clouds. To substantiate the concept o...

We present an initial look at the far-infrared–radio correlation within the starforming disks of four nearby, nearly face–on galaxies (NGC 2403, NGC3031, NGC5194, and NGC6946). Using Spitzer MIPS imaging and WSRT radio continuum data, we are able to probe variations in the logarithmic 70 μm/22 cm (q70) flux density ratios across each disk at sub–kp...

When high-energy cosmic rays impinge on a dense dielectric medium such as the lunar re-golith, radio waves are produced through the Askaryan effect. At frequencies of the order of 100 MHz this is a very efficient way to detect Ultra-High Energy cosmic rays or neutrinos. The radio signals can be measured using the Westerbork Synthesis Radio Telescop...

With the advent of facilities enabling wide-field monitoring of the dynamic radio sky, new areas of parameter space will be opened up for exploration. Such monitoring will be done primarily at low frequencies, in order to maximise the available field of view. One class of radio sources known to be highly variable at GHz frequencies are the so-calle...

LOFAR, the Low Frequency Array, is a new radio telescope under construction in the Netherlands, designed to operate between 30 and 240 MHz. The Transients Key Project is one of the four Key Science Projects which comprise the core LOFAR science case. The remit of the Transients Key Project is to study variable and transient radio sources detected b...