Документ взят из кэша поисковой машины. Адрес оригинального документа : http://www.mrao.cam.ac.uk/projects/skads/lofar/minutes/galaxies.working_group.pdf Дата изменения: Wed Apr 8 01:02:12 2009 Дата индексирования: Tue Aug 18 11:19:34 2009 Кодировка: Поисковые слова: релятивистское движение

Meeting of the MKSP Nearby Galaxies Working Group
Cambridge 2009 March 25 09:30-12:00
Participants: P.Alexander, J.Anderson, R.Beck, C.Chyzy, A.Fletcher, J.GeisbЭsch, G.Heald, J.Riley, H.RЖttgering, A.Scaife 1. Science Case / Project Plan Version of 2007 urgently needs update. Make clear that detection of synchrotron emission from outer disks or halos is already important to learn about magnetic fields, even if no polarisation can be detected. Computing magnetic field strengths needs information about CRE energy losses, to be derived from radio spectra. New (sub)chapters are needed on: · Irregular and blue compact galaxies, interacting galaxies, galaxy groups (for the Nearby Galaxies chapter) Authors: Chris Chyzy, Marek Urbanik. · Investigate small-scale magnetic fields by Faraday depolarisation (for the Milky Way and Nearby Galaxies chapters) Authors: Andrew Fletcher, Paul Alexander, JЖrn GeisbЭsch. · Simulations of small-scale and large-scale magnetic fields in galaxies, Faraday depolarisation, and synthetic RM data cubes (new chapter) Authors: Andrew Fletcher, JЖrn GeisbЭsch, Jongsoo Kim. The topic of magnetic fields in intergalactic filaments still needs discussion. Search for individual candidates (e.g. galaxy groups or select from optical galaxy surveys) or go for statistical detection? New MKSP Working Group: Paul Alexander (chair), Tigran Arshakian, Marcus BrЭggen, Ger de Bruyn, Chris Chyzy, Torsten Enъlin, Jongsoo Kim. 2. Galaxy sample Actual sample includes 54 galaxies. Detection of pol and RM from extended disks and halos needs more than 100h integration per galaxy which will be possible only for a subsample -> strategy to choose the best cases is needed, to be done within the Working Group. Possible criteria: · Surface brightness · Radio spectrum · Mass · Inclination · Rotation velocity · Star-formation rate · Strength of warp · Degree of interaction · Galactic latitude (piggyback observing requested by the Milky Way Working Group)


3. Use Case / Commissioning Plan Needs to be written within next months by a small team (C.Chyzy, G.Heald, J.Anderson, R. Beck). A meeting will take place in April or early May in Bonn. Important question: Do we need ~10" resolution to detect extended pol, or can we smooth to ~30" in order to gain sensitivity? -> Simulations of Faraday DP is needed (see above). 4. Joint observations with the Survey KSP The MKSP needs spectral information about nearby galaxies from the SKSP surveys to choose best cases for deep integrations, and to determine magnetic field strengths (taking into account CRE losses). The Survey KSP plans pointed observations at ~210 MHz of about 60 nearby galaxies with about 9h integration time each. The present list has 384 galaxies, selection by discussions between the SKSP and the MSKP (C.Chyzy is the moderator). The Survey KSP also plans deep observations of about 10 nearby galaxies. A joint list of both KSPs will be prepared to achieve the best science. G.Heald will check the frequency span acceptable for both KSPs. 5. Observations with other telescopes Observations between the LOFAR wavelength range and the GHz range of the Effelsberg, VLA and ATCA telescopes are needed. The Cambridge group (D.Green) has a running project on nearby galaxies at 610 MHz at the GMRT (including pol) which are important for the MKSP. (Observed so far are NGC1365 and NGC4449.) Another GMRT source survey project of the Cambridge group (with Calgary) will be important to estimate the density of polarised sources at low frequencies, as needed for RM grids. At 350 MHz, theWSRT will only available for another ~2 years. A few projects on nearby galaxies are running (M31, IC342, NGC6946, NGC891), but more projects should be performed, especially on edge-on galaxies. PhD student urgently needed. 6. Other items The expected time to be allocated to the MKSP is by far too small to reach the goals. Political action is required.

Rainer Beck