JHK Imaging and Photometry of Low z QSOs and Radio Galaxy

We describe J,H,K deep imaging of 90 arcmin fields around 4 QSOs and one Radio galaxy at redshifts in the range 0.06 to 0.30, and show their images, luminosity profiles, and NIR 2-colour diagrams of objects. We find that the QSO hosts are all resolved, and compare them with previous CCD images. The host galaxy colours are consistent with old and young stellar populations at the QSO redshift. The colours of nearby galaxies suggest that all the AGN live in groups of generally smaller companion galaxies, mostly with evolved populations at the same redshift. The two radio-loud objects live in richer cluster environments than the others. Gissel population models indicate reddening in the galaxies, star-forming regions, and possibly a systematic H-K offset. The QSO luminosity profiles are complex and reveal some of their tidal disturbance and star-formation history.Comment: 22 pages of text (latex), 2 tables )latex), and 15 figures (postscript). Accepted for publication in AJ, February 1997. Also available at http://www.dao.nrc.ca/DAO/SCIENCE/science.htm

A Supernova Factory in the Merger System Arp 299

We have imaged the nearby galaxy merger Arp 299 at arcsecond and milliarcsecond resolution, using both the Very Large Array and the Very Long Baseline Array. The large-scale radio emission from the merger contains 5 bright, compact radio sources embedded in diffuse emission, with diameters less than 200 pc. Supernova rates of 0.1 to 1 per year are required to produce the VLA-detected radio emission in these sources. Two of the compact VLA radio sources, designated Source A and Source D, also have been detected and imaged at milliarcsecond scales. Source A, which is associated with the nucleus of one of the merging galaxies, contains five milliarcsecond-scale sources, each with a radio power between 100 and 1000 times that of the Galactic supernova remnant Cassiopeia A. Four of these have flat or inverted spectra and appear to be young supernovae. Three of the VLBI-scale sources are located within 10 pc (projected) of one another, and two are separated by less than 3 pc, indicating that they all may be within the same super starcluster or complex of such clusters. The brightest VLBI-scale source, A0, has an extremely inverted pectrum, with alpha larger than +2 at gigahertz frequencies. It seems to be the youngest supernova, which has not yet broken out of its circumstellar shell. The milliarcsecond radio sources within Source A appear to constitute a upernova factory, confirming the presence of an extreme starburst that peaked at least a few million years ago.Comment: Accepted for the Astrophysical Journal, 22 pages, 10 figure

Evolution of luminous IRAS galaxies: Radio imaging

In a recent study of IRAS galaxies' optical morphologies, we found that luminous IR sources lie in the IR color-luminosity plane in groups which separate out by optical spectroscopic type and also by degree of tidal disturbance. We found that the most luminous steep-IR-spectrum sources are generally galaxies in the initial stages of a major tidal interaction. Galaxies with active nuclei were generally found to have flatter IR spectra, to cover a range of IR luminosity, and to be in the later stages of a tidal interaction. We proposed a sequence of events by which luminous IR sources evolve: they start as interacting or merging galaxies, some develop active nuclei, and most undergo extensive star-formation in their central regions. Another way to study these objects and their individual evolution is to study their radio morphologies. Radio emission may arise at a detectable level from supernovae in star-forming regions and/or the appearance of an active nucleus can be accompanied by a nuclear radio source (which may develop extended structure). Therefore, the compact radio structure may trace the evolution of the inner regions of IRAS-luminous sources. If the radio sources are triggered by the interactions, we would expect to find the radio morphology related to the optical 'interactivity' of the systems. Here, we explore using the radio emission of IRAS galaxies as a possible tracer of galaxy evolution. We present and discuss observations of the compact radio morphology of 111 luminous IRAS-selected active galaxies covering a wide range of IR and optical properties

Ultraviolet Imaging Telescope (UIT) observations of galaxies

Ultraviolet images of several galaxies were obtained during the ASTRO-1 shuttle mission in December, 1990. The images have a FWHM angular resolution of approximately 3 arcsecond and are of circular fields approximately 40 arcminutes in diameter. Most galaxies were observed in at least two and sometimes as many as four broad bands. A very few fields were observed with narrower band filters. The most basic result of these observations is that most systems look dramatically different in the UV from their well-known optical appearances. Preliminary results of these studies will be presented. Information will be available on fields observed by the UTI during the ASTRO 1 mission; when that data becomes public it can be obtained from the NSSDC. The ASTRO observatory is expected to fly again in 1994 with approximately half of the observing time from that mission devoted to guest observers. The Ultraviolet Imaging telescope is extremely well suited for galaxy studies, and the UIT term is interested in encouraging a wide range of scientific studies by guest observers. Ultraviolet Imaging telescope is extremely well suited for galaxy studies, and the UIT team is interested in encouraging a wide range of scientific studies by guest observers

Radio Emission Associated with Ultraluminous X-ray Sources in the Galaxy Merger NGC 3256

We present new 6, 3.6, and 2 cm VLA radio observations of the nearby merger system NGC 3256, with resolutions of ~100 pc, which reveal compact radio sources embedded in more diffuse emission at all three wavelengths. The two radio nuclei are partially resolved, but the two dominant compact sources that remain coincide with the two most powerful compact Ultraluminous X-ray sources (ULXs) recently reported by Lira et al. The radio/X-ray ratios for these two sources are too high by factors of >100-1000 to be normal X-ray binaries. However, their radio and X-ray powers and ratios are consistent with low-luminosity active galactic nuclei (LLAGNs), and optical emission lines suggest the presence of a nuclear disk around the northern nucleus. If the two nuclear ULXs are LLAGNs, their associated black holes are separated by only \~1kpc, about 6 times closer to one another than those found recently in the merger galaxy NGC 6240. A third ULX on the outskirts of the merger is also a radio source, and probably is a collection of supernova remnants. The remaining ULXs are not coincident with any source of compact radio emission, and are consistent with expectations for beamed X-ray binaries or intermediate-mass black holes.Comment: Accepted for ApJ (10 pages, 5 figures

Unquenching the Quark Model and Screened Potentials

The low-lying spectrum of the quark model is shown to be robust under the effects of `unquenching'. In contrast, the use of screened potentials is shown to be of limited use in models of hadrons. Applications to unquenching the lattice Wilson loop potential and to glueball mixing in the adiabatic hybrid spectrum are also presented.Comment: 6 pages, 3 ps figures, revtex. Version to appear in J. Phys.

Flavour singlet pseudoscalar masses in N_f = 2 QCD

We perform a lattice mass analysis in the flavour singlet pseudoscalar channel on the SESAM and TXL full QCD vacuum configurations, with 2 active flavours of dynamical Wilson fermions at beta = 5.6. At our inverse lattice spacing, a^-1 = 2.3 GeV, we retrieve by a chiral extrapolation to the physical light quark masses the value m_eta' = 3.7(+8)(-4) m_pi. A crude extrapolation from (N_f = 3) phenomenology would suggest m_eta' \approx 5.1 m_pi for N_f = 2 QCD. we verify that the mass gap between the singlet state eta' and the pi flavour triplt state is due to gauge configurations with non-trivial topology.Comment: 8 pages, 10 figure

The Relative Orientation of Nuclear Accretion and Galaxy Stellar Disks in Seyfert Galaxies

We use the difference (delta) between the position angles of the nuclear radio emission and the host galaxy major axis to investigate the distribution of the angle (beta) between the axes of the nuclear accretion disk and the host galaxy disk in Seyfert galaxies. We provide a critical appraisal of the quality of all measurements, and find that the data are limited by observational uncertainties and biases, such as the well known deficiency of Seyfert galaxies of high inclination. There is weak evidence that the distribution of delta for Seyfert 2 galaxies may be different (at the 90% confidence level) from a uniform distribution, while the Seyfert 1 delta distribution is not significantly different from a uniform distribution or from the Seyfert 2 delta distribution. The cause of the possible non-uniformity in the distribution of delta for Seyfert 2 galaxies is discussed. Seyfert nuclei in late-type spiral galaxies may favor large values of delta (at the ~96% confidence level), while those in early-type galaxies show a more or less random distribution of delta. This may imply that the nuclear accretion disk in non-interacting late-type spirals tends to align with the stellar disk, while that in early-type galaxies is more randomly oriented, perhaps as a result of accretion following a galaxy merger. We point out that biases in the distribution of inclination translate to biased estimates of beta in the context of the unified scheme. When this effect is taken into account, the distributions of beta for all Seyferts together, and of Seyfert 1's and 2's separately, agree with the hypothesis that the radio jets are randomly oriented with respect to the galaxy disk. The data are consistent with the expectations of the unified scheme, but do not demand it.Comment: To appear in the Astrophysical Journal, Vol 516 #1, May 1, 1999. Corrected figure placement within pape