Showing papers by "Seppo Laine published in 2008"

Radio continuum jet in ngc 7479

Abstract: The barred galaxy NGC 7479 hosts a remarkable jetlike radio continuum feature: bright, 12 kpc long in projection, and hosting an aligned magnetic field. The degree of polarization is 6%-8% along the jet and remarkably constant, which is consistent with helical field models. The radio brightness of the jet suggests strong interaction with the ISM and hence a location near the disk plane. We observed NGC 7479 at four wavelengths with the VLA and Effelsberg radio telescopes. The equipartition strength is 35-40 μG for the total and ≥10 μG for the ordered magnetic field in the jet. The jet acts as a bright, polarized background. Faraday rotation between 3.5 and 6 cm and depolarization between 6 and 22 cm can be explained by magnetoionic gas in front of the jet, with thermal electron densities of ~0.06 cm^−3 in the bar and ~0.03 cm^−3 outside the bar. The regular magnetic field along the bar points toward the nucleus on both sides. The regular field in the disk reveals multiple reversals, probably consisting of field loops stretched by a shearing gas flow in the bar. The projection of the jet bending in the sky plane is in the sense opposite to that of the underlying stellar and gaseous spiral structure. The bending in 3D is most easily explained as a precessing jet, with an age less than 10^6 yr. Our observations are consistent with very recent triggering, possibly by a minor merger. NGC 7479 provides a unique opportunity to study interaction-triggered 15 kpc scale radio jets within a spiral galaxy.

Proposal review rankings: the influence of reviewer discussions on proposal selection

Abstract: The telescope time allocation process for NASA's Great Observatories involves a substantial commitment of time and expertise by the astronomical community. The annual review meetings typically have 100 external participants. Each reviewer spends 3-6 days at the meeting in addition to one-two weeks of preparation time, reading and grading proposals. The reviewers grade the proposals based on their individual reading prior to the meeting and grade them again after discussion within the broad, subject-based review panels. We summarize here how the outcome of the review process for three Spitzer observing cycles would have changed if the selection had been done strictly based on the preliminary grades without having the panels meet and discuss the proposals. The changes in grading during the review meeting have a substantial impact on the final list of selected proposals. Approximately 30% of the selected proposals would not have been included if just the preliminary rankings had been used to make the selection.

Image Processing Application for Cognition (IPAC) - Traditional and Emerging Topics in Image Processing in Astronomy

Abstract: A new application framework for advanced image processing for astronomy is presented. It implements standard two-dimensional operators, and recent developments in the field of non-astronomical image processing (IP), as well as original algorithms based on nonlinear partial differential equations (PDE). These algorithms are especially well suited for multi-scale astronomical images since they increase signal to noise ratio without smearing localized and diffuse objects. The visualization component is based on the extensive tools that we developed for Spitzer Space Telescope’s observation planning tool Spot and archive retrieval tool Leopard. It contains many common features, combines images in new and unique ways and interfaces with many astronomy data archives. Both interactive and batch mode processing are incorporated. In the interactive mode, the user can set up simple processing pipelines, and monitor and visualize the resulting images from each step of the processing stream. The system is platform-independent and has an open architecture that allows extensibility by addition of plug-ins. This presentation addresses astronomical applications of traditional topics of IP (image enhancement, image segmentation) as well as emerging new topics like automated image quality assessment (QA) and feature extraction, which have potential for shaping future developments in the field. Our application framework embodies a novel synergistic approach based on integration of image processing, image visualization and image QA (iQA).

Massive star formation and dust in collisional ring galaxies: From GALEX to Spitzer

Abstract: We present some first results from a GALEX and Spitzer survey of a dozen collisional ring galaxies. The combination of UV and mid-IR imaging and spectroscopy will allow us to investigate the relationship between massive star formation sites, PAH molecular–band strengths, and dust heating in these mainly simultaneous starburst rings. A deep observation of the well-known Cartwheel ring galaxy has revealed a gigantic outer UV disk which extends to at least twice the radius of the outer blue star–forming ring. A lack of UV variability in the outer Cartwheel ring rules out an intermediate-mass black hole (IMBH) as the origin of the brightest of a dozen ULX source seen by Chandra in the ring.