Detection of an unresolved nuclear radio source in M31

Crane, P. C.; Dickel, John R.; Cowan, J. J.

doi:10.1086/186359

Cited by 56 publications

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“…The (blue) cross indicates the centre of M 31 (α J2000 = 00 h 42 m 44. s 371, δ J2000 = 41 • 16 08. 34, Crane et al 1992). Left: velocity field measured in CO for the whole galaxy by Nieten et al (2006).…”

Section: Observationsmentioning

confidence: 99%

Molecular gas in the inner 0.7 kpc-radius ring of M 31

Melchior

Combes

2011

A&A

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The study of the gas kinematic in the central 1.5 kpc × 1.5 kpc region of M 31 has revealed several surprises. The starting point of this investigation was the detection at the IRAM-30 m telescope of molecular gas with very large line splittings up to 260 km s −1 within the beam (∼40 pc). In this region, which is known for its low gas content, we also detect an ionised gas outflow in the circumnuclear region (within 75 pc from the centre) extending to the whole area in X-ray. Relying on atomic, ionised, and molecular gas, we account for most observables with a scenario that assumes that a few hundreds Myr ago, M 31 underwent a frontal collision with M 32, which triggered some star-formation activity in the centre, and this collision explains the special configuration of M 31 with two rings observed at 0.7 kpc and 10 kpc. The inner disc (whose rotation is detected in HI and ionised gas ([NII])) has thus been tilted (inclination: 43 deg, PA: 70 deg) with respect to the main disc (inclination: 77 deg, PA: 35 deg). One of the CO velocity components is compatible with this inner disc, while the second one comes from a tilted ring-like material with 40 deg inclination and PA = −35 deg. The relic star formation estimated by previous works to have occurred more than 100 Myr ago could have been triggered by the collision and could be linked to the outflow detected in the ionised gas. Last, we demonstrate that the amplitude of the line splittings detected in CO centred on the systemic velocity with a relatively high spatial resolution (40 pc) cannot be accounted for by a possible weak bar that is roughly aligned along the minor axis. Although M 31 has a triaxial bulge, there are no bar indicators in the gas component (photometry, no strong skewness of the isovelocities, etc.).

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Section: Observationsmentioning

confidence: 99%

Molecular gas in the inner 0.7 kpc-radius ring of M 31

Melchior

Combes

2011

A&A

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“…For M BH = 4.5 × 10 7 M ⊙ (Kormendy & Bender 1999;Bacon et al 2001), L X /L Edd = 7 × 10 −10 . M31 similarly has a central radio core, with a luminosity approximately one-third of that of Sgr A * [flux density at 8.4 GHz ∼30 µJy (Crane, Dickel, & Cowan 1992), or L R ≈ 2 × 10 32 erg s −1 for an assumed distance of 800 kpc]. Unlike Sgr A * , however, here the relative fraction of radio to X-ray luminosity is significantly lower, log (L R /L X ) ≈ −4.3.…”

Section: M32 In Contextmentioning

confidence: 99%

Detection of the “Active” Nucleus of M32

Terashima

Ulvestad

2003

ApJ

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M32 hosts a 2.5×10 6 M ⊙ central black hole, but signs of nuclear activity in this galaxy have long eluded detection. We report the first conclusive detection of the nucleus of M32 in X-rays, based on high-resolution, sensitive observations made with Chandra. The 2-10 keV luminosity is merely 9.4×10 35 erg s −1 , ∼ 3 × 10 −9 of the Eddington luminosity of the black hole. Weak diffuse emission, consistent with thermal gas at a temperature of 0.37 keV, is seen in an annular region ∼100 pc from the center. We also present a deep, moderately high-resolution (0. ′′ 9), radio continuum observation obtained with the Very Large Array, which places a tight upper bound on the nuclear radio power at 8.4 GHz. We combine these new measurements with upper limits at other wavelengths to discuss implications for the nature of accretion onto the central black hole.

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“…The most constraining data on this plot are the Very Large Array (VLA) measurements (Crane et al 1992(Crane et al , 1993, the FUV point inferred from the subtraction of starlight (King et al 1995), and the more recent Chandra results (shown as a butterfly below 1.5 keV and as an upper limit above this energy; T 1 10 is due to radiative recombination. The dotted curve corresponds to the emissivity from the inner, cool region, which accounts for the prominent UV peak due to hydrogen line emission.…”

Section: Results and Conclusionmentioning

confidence: 99%

“…INTRODUCTION The discovery of an unresolved radio point source (labeled as M31*) in the nucleus of M31 (Crane, Dickel, & Cowan 1992) led to an early suggestion (Melia 1992b) that its nature may be similar to that of the supermassive black hole candidate, Sgr A*, at the center of our own Galaxy. The distance to M31 renders its nuclear environment difficult to observe with anything approaching the spatial resolution now available for the Galactic center, but certain cues suggest that in both cases we may be dealing with a massive pointlike object accreting gas from the interstellar medium, possibly from stellar winds.…”

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confidence: 99%

“…This view is supported by the arguments of Kormendy & Bender (1999) that the central supermassive black hole probably lies at the center of this UV-bright cluster. In the radio, there now exist measurements of M31*'s flux at two epochs (Crane et al 1992(Crane et al , 1993, showing that, at least at 3.6 cm, its luminosity is variable on a timescale of a year or less. But even though M31* is apparently 10 times more massive than the black hole at the Galactic center, its power at 3.6 cm is only one-third that of Sgr A* (assuming a distance to M31 of 784 kpc; Stanek & Garnavich 1998).…”

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Accretion Processes in the Nucleus of M31

Liu

Melia

2001

The Astrophysical Journal

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The hypothesized supermassive black hole in the nucleus of M31 (M31*) has many features in common with Sgr A* at the Galactic center, yet they differ in several significant and important ways. Although M31* is probably 10 times heavier, its radio luminosity at 3.6 cm is only one-third that of Sgr A*. At the same time, M31* is apparently thousands of times more luminous in X-rays than its Galactic center counterpart. Thus, a comparative study of these objects can be valuable in helping us to understand the underlying physical basis for their activity. We show here that the accretion model being developed for Sgr A* comprises two branches of solutions, distinguished by the relative importance of cooling compared to compressional heating at the radius where r C the ambient gas is captured by the black hole. For typical conditions in the interstellar medium, the initial temperature [ K] sits on the unstable branch of the cooling function. Depending on the actual 6 7T(r ) ∼ 10 -10 C value of and the accretion rate, the plasma settles onto either a hot branch (attaining a temperature as high T(r ) C as 10 10 K or so at small radii) or a cold branch, in which T drops to ∼10 4 K. Sgr A* is presumably a "hot" black hole. We show here that Very Large Array, Hubble Space Telescope, and Chandra observations of M31* reveal it to be a member of the "cold" black hole family. We discuss several predicted features in the spectrum of M31* that may be testable by future multiwavelength observations, including the presence of a prominent UV spike (from hydrogen line emission) that would be absent on the hot branch.

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Detection of an unresolved nuclear radio source in M31

Cited by 56 publications

References 0 publications

Molecular gas in the inner 0.7 kpc-radius ring of M 31

Molecular gas in the inner 0.7 kpc-radius ring of M 31

Detection of the “Active” Nucleus of M32

Accretion Processes in the Nucleus of M31

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