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 Urbanik

Based 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 region

Diffuse CO(1-0) gas IRAM dish (Reuter et al. 1996)

Clumpy CO(1-0) gas OVRO interf. (Soida et al. in prep)

SE abnormal region

Diifuse 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.)