Magnetic fields in perturbed galaxies: a sensitive measure of external influences or
description
Transcript of Magnetic fields in perturbed galaxies: a sensitive measure of external influences or
Magnetic fields in perturbed galaxies: a sensitive measure of
external influences or
Why to observe abnormal galaxies when we don’t yet fully understand normal ones?
Some terminology:
Regular magnetic field: a unidirectional one: RM0
Pseudo-regular field: an anisotropic random one: <Bx2> > <By2> RM=0
Prepared by Marek UrbanikBased on observations made in cooperation with
K. Chyży, M. Soida, M. Weżgowiec, K. Otmianowska-Mazur - Astronomical Observatory, Jagiellonian University, Kraków
R. Beck – Max-Planck-Institut für Radioastronomie, Bonn
B. Vollmer - CDS, Observatoire Astronomique de Strasbourg
Ch. Balkowski - Observatoire de Paris, GEPI, CNRS, and Université Paris 7
A. Chung - Smithsonian Astrophysical Observatory
J. van Gorkom - Department of Astronomy, Columbia University
J.D. Kenney - Yale University Astronomy Department
A merging pair
NGC 4038/39 4.85 GHz DSS+TP+B-vec
40%
15%
1%
10%
The fundamental work by Chyży &
Beck (2004) A&A, 417,
541
HST image credit: B. Whitmore (STScI) and NASA
Courtesy K. Chyży
A merging pair
NGC 4038/39 4.85 GHz DSS+TP+B-vec
The fundamental work by Chyży &
Beck (2004) A&A, 417,
541 A highly polarized „collisionregion”
A low-polarization hidden SF region
A highly polarized, steep spectrum outflow region
Courtesy K. Chyży
NGC 877
Drzazga, Chyży in prep.
A magnetic bridge?
VLA TP conts + PI B-vecs VLA archive data
Courtesy K. Chyży
Knapik et. al. in prep.
Note the vertically polarized plume north of the centre. Unlikely to be an AGN-borne jet as NGC 4490 is of late type.
NGC4490/85 another interacting pair
NGC 4490/85 a magnetized stream??
The vertically polarized structure north of the centre of NGC 4490 exactly corresponds in position and orientation (marked by a red line) with the HI spur seen there by Clemens et al. (1998 – ADS link here) and by Clemens & Alexander (2002 – ADS link here).
Pol. vectors – see Soida et al., 2001, A&A 378, 40
(VLA)
PV along this line and analogous along the NW arm
NGC 3627
Image credit: M. Neeser (Univ.-Sternwarte Munchen), P. Barthel (Kapteyn Astron. Institute), H. Heyer, H. Boffin (ESO),
NW normal regionDiffuse CO(1-0) gas IRAM dish (Reuter et al. 1996)
Clumpy CO(1-0) gas OVRO interf. (Soida et al. in prep)
SE abnormal regionDiifuse CO gas
Clumpy CO gas
Colour – clumpy cool gas seen by OVRO, conts – HHT 3-2 upper panel: polarized intensity
Colour – clumpy cool gas seen by OVRO, conts – IRAM 1-0 upper panel: polarized intensity
All the analyses to be found in:
Soida et al. in prep.
Data: OVRO inrerferometer (colour) – M. Soida,
IRAM – Reuter et al. 1996 A&A 306, 721
CO(3-2) HHT – Krakow (M. Soida, M. Urbanik) + Bonn (M. Dumke, M. Krause, R. Wielebinski), in prep.
A very personal remark: Without polarization observations probably these anomalies would remain unnoticed?
Stephan’s QuintetIntergalactic hot X-ray gas pool
See Trinchieri et al. 2003, A&A, 401, 173
Stephan’s Quintett Soida et al. in prep.
Genuine intergalactic (quasi) regular magnetic field
TP conts+PI B-vecs VLA 6cm
Bt = 8G Bu = 2G
Bt = 7G Bu = 1.5 G
Optical image credit: NASA, ESA, and the Hubble SM4 ERO Team
Vollmer et al. + Kraków+Bonn& USA teams, 2007,A&A 464, L37
85%
Fractions of pol. flux on both sides of a major axis
15%
NGC 4501 in the Virgo Cluster
TP+PI B-vecs, VLA 6cm
Motion?
NGC 4501 rectified: Assymmetry of the magnetic pitch angles
Data from Vollmer et al. 2007 + Kraków+Bonn & USA teams
Polarization used to constrain the model
Vollmer et al.(incl. Krakow, Bonn & USA teams, 2008), A&A 483, 89
????
NGC 4654
TP contours +PI vecs VLA 20cm
Colour - HI data: Phookun & Mundy 1995 ApJ, 453, 154, kindly provided by Dr Phookun
Radio data Vollmer et al. (incl. Krakow, Bonn & USA teams) 2007 see also A&A 464, L37
NGC 4402 blown from the bottom?
TP conts + PI vecs VLA 6cm
Vollmer et al. (incl. Krakow, Bonn & NRAO teams) 2007
Galaxy motion?
Vollmer et al. (+Krakow+Bonn+USA teams): Vollmer et al., 2010, A&A 512, A36
Edge-on „no reason” caseNGC 4535 – in southern Virgo extension – a „no reason” face-on case
Effelsberg 6 cm Weżgowiec et al., 2007, A&A 471, 93
NGC 4438
X-rays (green) M. Weżgowiec from archive NEWTON-XMM data
Motion?
Now green contours are TP while bars denote pol. int. B-vectors (VLA at 6cm) see Vollmer et al. (incl. Krakow, Bonn & USA teams), 2007, A&A 464, L37
Attempt to summarize
We have observed:1. Magnetic bridges
2. Anomalous arms
3. Compressional ridges
4. Magnetized outflows
5. Intergalactic magnetic fields
Magnetic field as seen in polarization is a very good „preselector” of anomalies to be studied in detail in other domains (X-rays, HI dynamics etc.)