Masers in AGN environments

Greenhill, L. J.

doi:10.1017/s1743921307013439

Cited by 14 publications

(13 citation statements)

References 62 publications

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“…In the optical, the OHMMs show that a high fraction of (U)LIRGs are classified as active galactic nuclei (AGNs; Baan, Salzer & LeWinter 1998; Darling & Giovanelli 2006), whereas the radio and the IR emission indicate that a high fraction of (U)LIRGs can be classified as starburst (Baan & Klöckner 2006; Willett et al 2011a,b). Using observations with angular resolution at subkiloparsec scales, which is currently only possible for a few OHMM galaxies (Greenhill 2002; Lonsdale 2002; Darling 2008; Greenhill 2008, and references therein), we show that only two of the OHMMs could be associated with an AGN‐type nucleus (e.g. Pihlström et al 2005; Klöckner, Baan & Garrett 2003).…”

Section: Introductionmentioning

confidence: 93%

Optical and OH megamaser observations of the starburst galaxy IIZw 096

Migenes¹,

Coziol²,

Klöckner³

et al. 2011

Monthly Notices of the Royal Astronomical Society

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Using the Multi‐Element Radio‐Linked Interferometer Network (MERLIN), we have acquired a high spatial resolution spectral image of the OH megamaser (OHMM) in the nearby starburst ‘galaxy’ known as IIZw 096. We have also acquired optical B, V, R, I and Hα images with the 1.5‐m telescope in San Pedro Mártir. By comparing the MERLIN observations with Hubble archive images, we are able to pinpoint the location of the OH maser emission in this object; the OHMM emission seems to be associated with a faint and reddish, compact‐round structure (a few hundred parsecs) off‐centre of a merging system of galaxies. From the colour and strong Hα emission, this object is consistent with the remains of the nucleus of a very perturbed galaxy in interaction. Assuming a Keplerian bounded system the mass necessary to produce a velocity range of ≈200 km s−1 for the OHMM is of the order of 109 M⊙, which is consistent with a massive black hole. Consequently, although the OHMM was previously suspected to be of starburst origin, our analysis suggests that an active galactic nucleus (AGN) could also be present in this merging system making it a composite source. IIZw 096 is a nearby example which shows how high spatial resolution data of the OHMM emission region, and supporting optical data, can be extremely helpful in determining the nature (starburst, AGN or composite) of such phenomenon.

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Section: Introductionmentioning

confidence: 93%

Optical and OH megamaser observations of the starburst galaxy IIZw 096

Migenes¹,

Coziol²,

Klöckner³

et al. 2011

Monthly Notices of the Royal Astronomical Society

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“…This includes the determination of geometric distances and 3-dimensional velocity vectors of galaxies, masses of nuclear engines, maps of accretion disks and physics of nuclear jet-molecular cloud interaction (for recent reviews, see Falcke et al (2000); Mrk 1157: Braatz et al (2004); NGC 1068: Claussen et al (1984); Mrk 1066: this paper, for a more recent independent detection see Braatz et al (2004); Mrk 3: Braatz et al (2004); Mrk 34: this paper; NGC 4151: Braatz et al (2004). Greenhill 2002Greenhill , 2004Maloney 2002;Morganti et al 2004;Henkel et al 2005). So far, almost 1000 active galaxies have been surveyed.…”

Section: Introduction and Sample Selectionmentioning

confidence: 99%

New H$_\mathsf{2}$O masers in Seyfert and FIR bright galaxies

Henkel

Peck

Tarchi

et al. 2005

A&A

130

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Abstract.Using the Effelsberg 100-m telescope, detections of four extragalactic water vapor masers are reported. Isotropic luminosities are ∼50, 1000, 1 and 230 L for Mrk 1066 (UGC 2456), Mrk 34, NGC 3556 and Arp 299, respectively. Mrk 34 contains by far the most distant and one of the most luminous water vapor megamasers so far reported in a Seyfert galaxy. The interacting system Arp 299 appears to show two maser hotspots separated by approximately 20 . With these new results and even more recent data from Braatz et al. (2004, ApJ, 617, L29), the detection rate in our sample of Seyferts with known jet-Narrow Line Region interactions becomes 50% (7/14), while in star forming galaxies with high (S 100 µm > 50 Jy) far infrared fluxes the detection rate is 22% (10/45). The jet-NLR interaction sample may not only contain "jet-masers" but also a significant number of accretion "disk-masers" like those seen in NGC 4258. A statistical analysis of 53 extragalactic H 2 O sources (excluding the Galaxy and the Magellanic Clouds) indicates (1) that the correlation between IRAS Point Source and H 2 O luminosities, established for individual star forming regions in the galactic disk, also holds for AGN-dominated megamaser galaxies; (2) that maser luminosities are not correlated with 60 µm/100 µm color temperatures; and (3) that only a small fraction of the luminous megamasers (L H 2 O > 100 L ) detectable with 100-m sized telescopes have so far been identified. The H 2 O luminosity function (LF) suggests that the number of galaxies with 1 L < L H 2 O < 10 L , the transition range between "kilomasers" (mostly star formation) and "megamasers" (active galactic nuclei), is small. The overall slope of the LF, ∼−1.5, indicates that the number of detectable masers is almost independent of their luminosity. If the LF is not steepening at very high maser luminosities and if it is possible to find suitable candidate sources, H 2 O megamasers at significant redshifts should be detectable even with present day state-of-the-art facilities.

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“…Extended accretion discs around central supermassive black holes (such as the ones traced by megamasers in nearby galaxies; see e.g. Greenhill 2007;Vlemmings et al 2007) are fed by molecular material in the interstellar medium. Molecular clouds are known to have large scale superthermal magnetic fields, and thus the initial magnetic fields in AGN discs are likely to be comparable to or larger than the thermal equipartition values.…”

Section: Introductionmentioning

confidence: 99%

High accretion rates in magnetised Keplerian discs mediated by a Parker instability driven dynamo

Johansen

Levin²

2008

A&A

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Hydromagnetic stresses in accretion discs have been the subject of intense theoretical research over the past one and a half decades. Most of the disc simulations have assumed a small initial magnetic field and studied the turbulence that arises from the magnetorotational instability. However, gaseous discs in galactic nuclei and in some binary systems are likely to have significant initial magnetisation. Motivated by this, we performed ideal magnetohydrodynamic simulations of strongly magnetised, vertically stratified discs in a Keplerian potential. Our initial equilibrium configuration, which has an azimuthal magnetic field in equipartion with thermal pressure, is unstable to the Parker instability. This leads to the expelling of magnetic field arcs, anchored in the midplane of the disc, to around five scale heights from the midplane. Transition to turbulence happens primarily through magnetorotational instability in the resulting vertical fields, although magnetorotational shear instability in the unperturbed azimuthal field plays a significant role as well, especially in the midplane where buoyancy is weak. High magnetic and hydrodynamical stresses arise, yielding an effective α-value of around 0.1 in our highest resolution run. Azimuthal magnetic field expelled by magnetic buoyancy from the disc is continuously replenished by the stretching of a radial field created as gas parcels slide in the linear gravity field along inclined magnetic field lines. This dynamo process, where the bending of field lines by the Parker instability leads to re-creation of the azimuthal field, implies that highly magnetised discs are astrophysically viable and that they have high accretion rates.

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Masers in AGN environments

Cited by 14 publications

References 62 publications

Optical and OH megamaser observations of the starburst galaxy IIZw 096

Optical and OH megamaser observations of the starburst galaxy IIZw 096

New H$_\mathsf{2}$O masers in Seyfert and FIR bright galaxies

High accretion rates in magnetised Keplerian discs mediated by a Parker instability driven dynamo

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