Proper Motions in the Andromeda Subgroup

This article presents results of VLBI observations of regions of H2O maser activity in the Local Group galaxies M33 and IC10. Since all position measurements were made relative to extragalactic background sources, the proper motions of the two galaxies could be measured. For M33, this provides this galaxy's three dimensional velocity, showing that this galaxy is moving with a velocity of 190 +/- 59 km\s relative to the Milky Way. For IC10, we obtain a motion of 215 +/- 42 km/s relative to the Milky Way. These measurements promise a new handle on dynamical models for the Local Group and the mass and dark matter halo of Andromeda and the Milky Way.Comment: 4 pages 1 figures, to appear in the proceedings of "Galaxies in the Local Volume", Astrophysics and Space Science, editors B. Koribalski and H. Jerjen also available at http://www.mpifr-bonn.mpg.de/staff/abrunthaler/pub.shtm

The far-infrared-radio correlation in MS0451-03

We present a multiwavelength analysis of star-forming galaxies in the massive cluster MS0451.6-0305 at z ˜ 0.54 to shed new light on the evolution of the far-infrared-radio relationship in distant rich clusters. We have derived total infrared luminosities for a spectroscopically confirmed sample of cluster and field galaxies through an empirical relation based on Spitzer Multiband Imaging Photometer for Spitzer 24 μm photometry. The radio flux densities were measured from deep Very Large Array 1.4 GHz radio continuum observations. We find the ratio of far-infrared to radio luminosity for galaxies in an intermediate-redshift cluster to be qFIR = 1.80 ± 0.15 with a dispersion of 0.53. Due to the large intrinsic dispersion, we do not find any observable change in this value with either redshift or environment. However, a higher percentage of galaxies in this cluster show an excess in their radio fluxes when compared to low-redshift clusters (27^{+23}_{-13} per cent to 11 per cent), suggestive of a cluster enhancement of radio-excess sources at this earlier epoch. In addition, the far-infrared-radio relationship for blue galaxies, where qFIR = 2.01 ± 0.14 with a dispersion of 0.35, is consistent with the predicted value from the field relationship, although these results are based on a sample from a single cluster

LADUMA: looking at the distant universe with the MeerKAT array

The cosmic evolution of galaxies’ neutral atomic gas content is a major science driver for the Square Kilometre Array (SKA), as well as for its South African (MeerKAT) and Australian (ASKAP) precursors. Among the H I large survey programs (LSPs) planned for ASKAP and MeerKAT, the deepest and narrowest tier of the “wedding cake” will be defined by the combined L-band+UHF-band Looking At the Distant Universe with the MeerKAT Array (LADUMA) survey, which will probe H I in emission within a single “cosmic vuvuzela” that extends to z = 1.4, when the universe was only a third of its present age. Through a combination of individual and stacked detections (the latter relying on extensive multi-wavelength studies of the survey’s target field), LADUMA will study the redshift evolution of the baryonic Tully–Fisher relation and the cosmic H I density, the variation of the H I mass function with redshift and environment, and the connection between H I content and galaxies’ stellar properties (mass, age, etc.). The survey will also build a sample of OH megamaser detections that can be used to trace the cosmic merger history. This proceedings contribution provides a brief introduction to the survey, its scientific aims, and its technical implementation, deferring a more complete discussion for a future article after the implications of a recent review of MeerKAT LSP project plans are fully worked out

H I Gas in the Environment of the Seyfert Galaxies NGC 6764 and Markarian 1126

Peer reviewe

Velocities and rotational excitation of interstellar H2 toward Pi Scorpii

A spectrum of Pi Sco showing numerous atomic lines and 70 absorption features from the Lyman and Werner transitions of interstellar H2 in rotational level J from zero to five is presented. Their shapes of the composite column density profiles are very nearly Gaussian with a one-dimensional rms velocity dispersion of 3 km/s. The behavior of shifts in the inferred N(H2) as a function of velocity are consistent with the overall profiles being composed of nearly symmetrical, tightly paced assemblies of about seven unresolved components. The relative overall column densities in the higher J levels of H2 are consistent with a model where these states are populated by optical pumping through the Lyman and Werner transitions, powered by UV radiation from nearby stars. The slight narrowing of the high-J profiles may be due to small clumps of H2 at radial velocities some 5-8 km/s from the core of the profile are exposed to a pumping flux about 10 times lower than that for the material near the profile's center

Velocities and rotational excitation of interstellar H2 toward Pi Scorpii

A spectrum of Pi Sco showing numerous atomic lines and 70 absorption features from the Lyman and Werner transitions of interstellar H2 in rotational level J from zero to five is presented. Their shapes of the composite column density profiles are very nearly Gaussian with a one-dimensional rms velocity dispersion of 3 km/s. The behavior of shifts in the inferred N(H2) as a function of velocity are consistent with the overall profiles being composed of nearly symmetrical, tightly paced assemblies of about seven unresolved components. The relative overall column densities in the higher J levels of H2 are consistent with a model where these states are populated by optical pumping through the Lyman and Werner transitions, powered by UV radiation from nearby stars. The slight narrowing of the high-J profiles may be due to small clumps of H2 at radial velocities some 5-8 km/s from the core of the profile are exposed to a pumping flux about 10 times lower than that for the material near the profile's center.Wetensch. publicatieFaculteit der Wiskunde en Natuurwetenschappe

Low-frequency study of 3C 31 with LOFAR

We present maps with LOFAR Low-Band Antenna (LBA) at 52MHz, LOFAR High-Band Antenna (HBA) at 145MHz, VLA P-band at 360MHz, and GMRT at 615MHz. These maps are presented at their native resolution using robust weighting. We also present LBA, HBA, and VLA maps at matched (u,v) coverage between 0.04 and 4.9 klambda. For completeness, we present again the WSRT map of Strom et al. (1983A&A...122..305S) at 609MHz, at approximately matched (u,v) coverage. For the VLA, we present one further map only from B- and C-configuration at 360MHz. (3 data files)

Low-frequency study of 3C 31 with LOFAR

Item does not contain fulltextWe present maps with LOFAR Low-Band Antenna (LBA) at 52MHz, LOFAR High-Band Antenna (HBA) at 145MHz, VLA P-band at 360MHz, and GMRT at 615MHz. These maps are presented at their native resolution using robust weighting. We also present LBA, HBA, and VLA maps at matched (u,v) coverage between 0.04 and 4.9 klambda. For completeness, we present again the WSRT map of Strom et al. (1983A&A...122..305S) at 609MHz, at approximately matched (u,v) coverage. For the VLA, we present one further map only from B- and C-configuration at 360MHz. (3 data files)

LOFAR reveals the giant: A low-frequency radio continuum study of the outflow in the nearby FR I radio galaxy 3C 31

We present a deep, low-frequency radio continuum study of the nearby Fanaroff-Riley class I (FR I) radio galaxy 3C 31 using a combination of LOw Frequency ARray (LOFAR; 30-85 and 115-178 MHz), Very Large Array (VLA; 290-420 MHz), Westerbork Synthesis Radio Telescope (WSRT; 609 MHz) and Giant Metre Radio Telescope (GMRT; 615 MHz) observations. Our new LOFAR 145-MHz map shows that 3C 31 has a largest physical size of 1.1Mpc in projection, which means 3C 31 now falls in the class of giant radio galaxies. We model the radio continuum intensitieswith advective cosmic ray transport, evolving the cosmic ray electron population and magnetic field strength in the tails as functions of distance to the nucleus. We find that if there is no in situ particle acceleration in the tails, then decelerating flows are required that depend on radius r as v α rβ (β ≈ -1). This then compensates for the strong adiabatic losses due to the lateral expansion of the tails. We are able to find selfconsistent solutions in agreement with the entrainment model of Croston &amp; Hardcastle, where the magnetic field provides ≈1/3 of the pressure needed for equilibrium with the surrounding intracluster medium. We obtain an advective time-scale of ≈190 Myr, which, if equated to the source age, would require an average expansion Mach number M≈ 5 over the source lifetime. Dynamical arguments suggest that instead either the outer tail material does not represent the oldest jet plasma or else the particle ages are underestimated due to the effects of particle acceleration on large scales.</p