Milestones in the Observations of Cosmic Magnetic Fields

“More recently attempts to detect the Zeeman effect in a variety of lines have been made: the H30α recombination line by Thum and Morris (1999), the CN line by Crutcher et al. (1999), and the CCS line by Levin et al. (2001).”

“The earliest maps of radio galaxies showed that considerable polarization is present and that magnetic fields are involved in the emission process (e.g., Cooper & Price 1964; Morris et al. 1964; Högbom & Carlsson 1974).”

“Afterwards, more and better data were accumulated for the circumnuclear disk (or the so-called dust ring) in a few pc from Sgr A* (Hildebrand et al. 1990, 1993; Novak et al. 2000), the giant molecular cloud Sgr B2 at 100 pc from the center as well as some other clouds near the center (Novak et al.…”

“First polarization of stars, later photoelectric surface photometry in Magellanic Clouds (e.g., Mathewson & Ford 1970b, 1970c; Schmidt 1970) gave us some real insight of the magnetic fields in these nearby galaxies.”

“The inclination or 3D structure of the magnetic field in some cases can be obtained by comparison of the Zeeman splitting measurements (see Schleuning et al. 2000; Hildebrand et al. 2000).”

“These polarization maps are understandable after the two effects are considered and modelled (Wood & Jones 1997).”

“…of bright molecular clouds (e.g., Ward-Thompson et al. 2000), but also in thermal streamers, in the accretion disk around T Tauri stars (e.g., Tamura et al. 1999), in the envelopes of young stellar objects (Holland et al. 1996), and in other sources of dust emission (e.g., Vallée et al. 2000).”

“…Tadhunter et al. 1992; Scarrott et al. 1990) or active galaxies (Draper et al. 1993; Cimatti et al. 1993) have been used to investigate some interesting issues, such as the “unified” scheme of AGNs, emission mechanisms (Breeveld & Puchnarewicz 1998) and hot spots (Lähteenmäki & Valtaoja 1999).”

“Equipartition magnetic field values in the magnetic tubes are at least 70 µG, perhaps about 0.4mG (Bicknell & Li 2001) or even several mG (Yusef-Zadeh & Morris 1987b).”

“Optical polarization observations of more distant galaxies (e.g., Tadhunter et al. 1992; Scarrott et al. 1990) or active galaxies (Draper et al. 1993; Cimatti et al. 1993) have been used to investigate some interesting issues, such as the “unified” scheme of AGNs, emission mechanisms (Breeveld &…”

“They are believed to be manifestations of strong vertical field lines (mG strength), i.e., they are illuminated flux tubes in large-scale pervasive fields (Yusef-Zadeh & Morris 1987a; Uchida et al. 1996).”

“After the Heiles’ catalog was compiled, some new data from Berdyugin’s group (Berdyugin & Teerikorpi 1997, 2001; Berdyugin et al. 2001) and others (e.g., Serkowski & Shawl 2001) have been published.”

“The observations of M31 by Hiltner (1958) were shown to require a magnetic field aligned along the major axis.”

“Surveys of larger areas of linearly polarized radio emission were continued at several frequencies (e.g., Berkhuijsen & Brouw 1963; Wielebinski & Shakeshaft 1964; Mathewson & Milne 1965; Berkhuijsen et al. 1964; Mathewson et al. 1966; Baker & Smith 1971; Wilkinson 1973; Baker & Wilkinson 1974).”

“…of the filaments and the molecular clouds or HII regions can be identified in the observations (e.g., Uchida et al. 1996; Yusef-Zadeh et al. 1997; Reich et al. 2000), and magnetic fields can be anchored in the molecular clouds (Bicknell & Li 2001), the detailed process for particle acceleration…”

“However, magnetic fields in high redshift (z ∼ 2.0 – 3.0) objects with Lyman-α damped systems have been found to be as strong as in nearby galaxies and in some clusters of galaxies (e.g., Kronberg et al. 1990, 1992; Athreya et al. 1998).”

“The variation in the position angle of the observed polarization along with the ionospheric data (Wielebinski & Shakeshaft 1962) revealed that Faraday rotation was taking place in the Earth’s ionosphere.”

“The studies on the variance of residual RM (observed RM minus foreground Galactic RM) versus source redshift z (e.g., Oren & Wolfe 1995; Perry et al. 1993), mainly due to data quality, have produced controversial results on the cosmological evolution of the magnetic field (in the intervening…”

“After the Heiles’ catalog was compiled, some new data from Berdyugin’s group (Berdyugin & Teerikorpi 1997, 2001; Berdyugin et al. 2001) and others (e.g., Serkowski & Shawl 2001) have been published.”

“Afterwards, Costa et al. (1991), Rand & Lyne (1994), Qiao et al. (1995), van Ommen et al. (1997) and Han et al. (1999) contributed a number of new RMs, providing RM data for some 320 objects.”

“One may have noticed that the Hubble Space Telescope is equipped with polarizers, which provide high resolution polarization maps even at the ultraviolet band (e.g., Kishimoto et al. 2002), that can be used to study hidden galactic nuclei and the scattering grains.”

“Note that observation of HI absorption towards the nuclear region of other (preferably edgeon) galaxies can provide information of magnetic fields in the redshifted clouds or circumnuclear ring around the nuclear region (e.g., Sarma et al. 2002).”

“…inherently weak effect due to the weak magnetic fields (a few µG along the line of sight) is difficult to pick up against strong instrumental effects (e.g., Verschuur 1995a), and such observations rarely produced consistent results (e.g., Verschuur 1995b; Troland & Heiles 1982; Myers et al. 1995).”

“After the Heiles’ catalog was compiled, some new data from Berdyugin’s group (Berdyugin & Teerikorpi 1997, 2001; Berdyugin et al. 2001) and others (e.g., Serkowski & Shawl 2001) have been published.”

“The pattern can be explained in terms of a magnetic field with a spiral configuration and by polarization produced by dichroic extinction (see discussion by Wood 1997).”

“In the intervening years, hundreds of polarization maps of radio galaxies have been published, first at lower frequencies and now at higher frequencies and with better resolutions mostly by VLA and WSRT observations (e.g., Högbom & Carlsson 1974; Klein et al. 1994; Ishwara-Chandra et al. 1998).”

“Studies of the Faraday rotation across the Galaxy were first made by Gardner & Davies (1966) and later by Gardner et al. (1969).”

“…nearby stars from Krutter (1980), 358+118 stars from Korhonen & Reiz (1986), 1000 nearby stars from Leroy (1993), 133 stars from Bel et al. (1993), 51 stars at high Galactic latitudes from Berdyugin et al. (1995), 361 stars from Reiz & Franco (1998), and 126 stars from Goodman (unpublished data).”

“A large-scale kinetic helicity is probably a necessary ingredient for a large-scale magnetic field (Blackman & Chou 1997) and helical turbulence may provide the key to the generation of large-scale magnetic fields (Blackman 2000; Brandenburg 2001).”

“Polarimetric observations of several galaxies by Appenzeller (1967) showed optical polarization vectors but were interpreted to be due to reflection as well as interstellar absorption with a magnetic field directed along the spiral arms.”

“A large-scale kinetic helicity is probably a necessary ingredient for a large-scale magnetic field (Blackman & Chou 1997) and helical turbulence may provide the key to the generation of large-scale magnetic fields (Blackman 2000; Brandenburg 2001).”

“In NGC 1808 (Scarrott et al. 1993), the polarization orientations follow the spiral arms on kpc scales, indicative of a magnetic field coherent on a galactic scale (Scarrott 1996).”

“Many objects (or even core components) have been studied using high resolution multifrequency VLBI/VLBA polarization data (e.g., Venturi & Taylor 1999).”

“Some early papers (e.g., Piddington 1964, 1978) considered that if an intergalactic magnetic field exists with B ∼ 10−8 G, it could be compressed by galactic rotation to B ∼ 10−5 G, intensities that are actually observed in galaxies.”

“The earliest attempts to observe linearly polarized radio emission were made by Thomson (1957), Razin (1958) and Pawsey & Harting (1960).”

“…inherently weak effect due to the weak magnetic fields (a few µG along the line of sight) is difficult to pick up against strong instrumental effects (e.g., Verschuur 1995a), and such observations rarely produced consistent results (e.g., Verschuur 1995b; Troland & Heiles 1982; Myers et al. 1995).”

“Polarization of the radio continuum emission of discrete radio sources was observed by Mayer et al. (1962).”

“Due to limited sensitivity and resolution, it is still too early to observe the dust polarization at these bands in nearby Galaxies, although Greaves et al. (2000) have reported results on M82 and Siebenmorgen et al. (2001) on NGC 1808.”

“The polarized emission at a few hundred MHz mainly comes from regions within a few hundred parsecs from the Sun (e.g., Spoelstra 1984) while the polarized emission at higher frequencies from more distant regions (Junkes et al. 1987; Gaensler et al. 2001).”

“The spectrum of the halos is very steep, often about −1.5 (Deiss et al. 1997; Liang et al. 2000), see the list in Henriksen (1998).”

“The observation of polarized emission at higher radio frequencies (Muller et al. 1963) showed additional Faraday rotation due to the magnetic fields in the interstellar medium of the Milky Way.”

“…other possibilities exist as to the cause of polarization of thermal dust emission, such as dust grains in an anisotropic radiation field (e.g., Onaka 2000) or different populations of grains at different temperatures, see Goodman (1996) for a review on both the observational and theoretical…”

“The earliest attempts to observe linearly polarized radio emission were made by Thomson (1957), Razin (1958) and Pawsey & Harting (1960).”

“In galaxies with high inclinations, such as M104 and NGC 5128 (Scarrott et al. 1996), the polarization in the central regions is oriented parallel to the dust lane.”

“8 cm which showed a complex vertical magnetic field pattern and by Duncan et al. (1998) on the kpc polarized plume.”

“Additional reviews on magnetic fields in galaxies have been made by Zeldovich et al. (1983), Rees (1987), Wielebinski & Krause (1993), Beck et al. (1996), Zweibel & Heiles (1997) and Beck (2001).”

“For a long time, the data were used to probe the intervening clouds (e.g., Markkanen 1979; Gomez de Castro et al. 1997).”

“In galaxies with high inclinations, such as M104 and NGC 5128 (Scarrott et al. 1996), the polarization in the central regions is oriented parallel to the dust lane.”

“…Tadhunter et al. 1992; Scarrott et al. 1990) or active galaxies (Draper et al. 1993; Cimatti et al. 1993) have been used to investigate some interesting issues, such as the “unified” scheme of AGNs, emission mechanisms (Breeveld & Puchnarewicz 1998) and hot spots (Lähteenmäki & Valtaoja 1999).”

“54+0.18 (Yusef-Zadeh et al. 1997).”

“The integral FIR polarization observed for the first time from the core of the quasar 3C 279, is a completely different story, being related to synchrotron radiation (Klaas et al. 1999).”

“The optical polarization in most cases indicated the presence of large-scale magnetic fields in galaxies (Elvius 1978).”

“Further halos were found in the A754 (Wielebinski et al. 1977), A1367 (Gavazzi 1978) and other clusters A2255, A2256 and A2319 (e.g., Harris et al. 1980; Bridle et al. 1979; Harris & Miley 1978) though many candidates were reported (see the status presented by Hanisch 1982).”

“Surveys of larger areas of linearly polarized radio emission were continued at several frequencies (e.g., Berkhuijsen & Brouw 1963; Wielebinski & Shakeshaft 1964; Mathewson & Milne 1965; Berkhuijsen et al. 1964; Mathewson et al. 1966; Baker & Smith 1971; Wilkinson 1973; Baker & Wilkinson 1974).”

“…in the very early Universe, the symmetry braking during phase transitions or at the time of recombination (e.g., Sicitte 1997), structure formation (e.g., Totani 1999; De Araujo & Opher 1997; Battaner et al. 1997) even the big-bang nucleosynthesis, should be fully investigated (See Rees 1987).”

“Surveys of larger areas of linearly polarized radio emission were continued at several frequencies (e.g., Berkhuijsen & Brouw 1963; Wielebinski & Shakeshaft 1964; Mathewson & Milne 1965; Berkhuijsen et al. 1964; Mathewson et al. 1966; Baker & Smith 1971; Wilkinson 1973; Baker & Wilkinson 1974).”

“…in the very early Universe, the symmetry braking during phase transitions or at the time of recombination (e.g., Sicitte 1997), structure formation (e.g., Totani 1999; De Araujo & Opher 1997; Battaner et al. 1997) even the big-bang nucleosynthesis, should be fully investigated (See Rees 1987).”

“King (1986) found that the scattering of light from the bright nucleus of NGC 7331 is predominant along the major axis of the galaxy, elsewhere the polarization is consistent with being produced by the transmission of light through elongated grains partially aligned by the galactic magnetic field…”

“Their catalog includes polarization measurements by Hiltner (1956), Hall (1958), Behr (1959), Loden (1961), Appenzeller (1968), and Visvanathan (1967).”

“Many observers continued to gather data on the polarization of discrete sources (e.g., Kronberg and his students: Vallee & Kronberg 1975; Kronberg & Wardle 1977), however the process of collecting (reliable?) data in early days is slow (e.g., Tabara & Inoue 1980).”

“…Heiles 1997; Vallée 1997, 1998; Balbus & Hawley 1998; Kulsrud 1999; Weiss & Tobias 2000; Title 2000; Beck 2000, 2001; Ferrière 2001; Kronberg et al. 2001; Carilli & Taylor 2002; Han & Wielebinski 2002; Widrow 2002; Tobias 2002; Ossendrijver 2003; Han et al. 2004; Brandenburg & Subramanian 2004).”

“…polarized thermal emission from dust at mm, sub-mm or infrared wavelengths, of optical starlightpolarization due to anisotropic scattering by magnetically-igned dust grains, of radio synchrotron emission, and of Faraday rotation of polarized radio sources (see Han & Wielebinski 2002, for a review).”