The nucleus of M31

Light, E. S.; Danielson, R. E.; Schwarzschild, M.

doi:10.1086/153241

Cited by 95 publications

(42 citation statements)

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“…The brightest point of M31 is displaced slightly from the center of the bulge isophotes (Light, Danielson, & Schwarzschild 1974), and the nucleus is now known to be double (Lauer et al 1993), with two brightness peaks separated by ∼0Љ .5. The brighter peak is designated P1, while the fainter (P2) lies within 0Љ .05 of the center of the outer nuclear isophotes and the bulge photocenter.…”

Section: Comparison With M31mentioning

confidence: 99%

Long-lived Lopsided Modes of Annular Disks Orbiting a Central Mass

Jacobs

Sellwood

2001

The Astrophysical Journal

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We demonstrate the existence of long-lived, large-amplitude eccentric modes in massive, annular particle disks in orbit about a central mass. The lopsided modes we have found precess slowly in the prograde direction at a rate that increases with disk mass and decreases with the amplitude of the distortion. The lopsidedness generally survives for as long as we run the calculations and may last indefinitely; we found no significant decay in over 700 disk-particle orbits in one case. These strongly nonlinear modes are readily created using a number of different perturbing rules, but we find no evidence for linear instabilities in unperturbed disks. Our results suggest that Tremaine's eccentric disk model for the nucleus of M31 may be viable, but none of our models matches all aspects of the observational data.

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Section: Comparison With M31mentioning

confidence: 99%

Long-lived Lopsided Modes of Annular Disks Orbiting a Central Mass

Jacobs

Sellwood

2001

The Astrophysical Journal

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“…However, the modeling was based on the unrealistic assumption of spherical symmetry. Upgrading the modeling to an axisymmetric (or triaxial) geometry would have been possible, but it was already known since the Stratoscope II observations (Light et al 1974), that the light distribution was not even symmetric. This asymmetry was resolved in an intriguing double structure by Lauer et al (1993) using the HST (pre-COSTAR) WFPC imaging capabilities.…”

Section: Introductionmentioning

confidence: 99%

The M 31 double nucleus probed with OASIS and HST

Bacon

Emsellem

Combes

et al. 2001

A&A

103

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Abstract. We present observations with the adaptive optics assisted integral field spectrograph OASIS of the M 31 double nucleus in the spectral domain around the Calcium triplet at a spatial resolution better than 0. 5 F W HM. These data are used to derive the two-dimensional stellar kinematics within the central 2 . Archival WFPC2/HST images in the F300W, F555W and F814W bands are revisited to perform a photometric decomposition of the nuclear region. We also present STIS/HST kinematics obtained from the archive. The luminosity distribution of the central region is well separated into the respective contributions of the bulge, the nucleus including P1 and P2, and the so-called UV peak. We then show, using the OASIS kinematical maps, that the axis joining P1 and P2, the two local surface brightness maxima, does not coincide with the kinematic major-axis, which is also the major-axis of the nuclear isophotes (excluding P1). We also confirm that the velocity dispersion peak is offset by ∼0. 2 from the UV peak, assumed to mark the location of the supermassive black hole. The newly reduced STIS/HST velocity and dispersion profiles are then compared to OASIS and other published kinematics. We find significant offsets with previously published data. Simple parametric models are then built to successfully reconcile all the available kinematics. We finally interpret the observations using new N-body simulations. The nearly Keplerian nuclear disk of M 31 is subject to a natural m = 1 mode, with a very slow pattern speed (3 km s −1 /pc for MBH = 7 10 7 M ), that can be maintained during more than a thousand dynamical times. The resulting morphology and kinematics of the mode can reproduce the M 31 nuclear-disk photometry and mean stellar velocity, including the observed asymmetries. It requires a central mass concentration and a cold disk system representing between 20 and 40% of its mass. Such a slow mode could be excited when interstellar clouds from the more external gaseous disk infall towards the centre. Nuclear disks formed from accreted gas are possible candidates for the precursors of these types of structures, and may be common in central regions of galaxies.

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“…% 3 Â 10 7 M (e.g., Kormendy & Bender 1999;Kormendy 1987;Dressler & Richstone 1988;Richstone, Bower, & Dressler 1990). Early Stratosphere II balloon observations (Light, Danielson, & Schwarzschild 1974) saw that M31 appeared to have a dense nucleus embedded on top a galaxy bulge. Nieto et al (1986) showed that the nucleus was off-center slightly from the bulge and asymmetric, which was hinted at in Light et al (1974).…”

Section: Introductionmentioning

confidence: 99%

“…Early Stratosphere II balloon observations (Light, Danielson, & Schwarzschild 1974) saw that M31 appeared to have a dense nucleus embedded on top a galaxy bulge. Nieto et al (1986) showed that the nucleus was off-center slightly from the bulge and asymmetric, which was hinted at in Light et al (1974). It was not until HST (Hubble Space Telescope) Wide Field and Planetary Camera (WFPC) and Faint Object Camera (FOC) observations that the nucleus was resolved into double components (Lauer et al 1993, hereafter L93;King, Stanford, & Crane 1995, hereafter K95;Lauer et al 1998, hereafter L98).…”

Section: Introductionmentioning

confidence: 99%

Assessing Formation Scenarios for the Double Nucleus of M31 Using Two-Dimensional Image Decomposition

Peng

2002

The Astronomical Journal

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The double nucleus geometry of M31 is currently best explained by the eccentric disk hypothesis of Tremaine, but whether the eccentric disk resulted from the tidal disruption of an inbounding star cluster, from a nuclear black hole, or from an m = 1 perturbation of a native nuclear disk remains debatable. I perform detailed two-dimensional decomposition of the M31 double nucleus in the Hubble Space Telescope V-band to study the bulge structure and to address competing formation scenarios of the eccentric disk. I deblend the double nucleus (P1 and P2) and the bulge simultaneously using five Sérsic and one Nuker components. P1 and P2 appear to be embedded inside an intermediate component (r e = 3>2) that is nearly spherical (q = 0.97 AE 0.02), while the main galaxy bulge is more elliptical (q = 0.81 AE 0.01). The spherical bulge mass (2.8 Â 10 7 M ), being coincident with the supermassive black hole mass (3 Â 10 7 M ), conjoined with a shallow bulge cusp, is consistent with the scenario that the bulge was scoured by spiraling binary supermassive black holes. In the two-dimensional decomposition the bulge is consistent with being centered near the UV peak of P2, but the exact position is difficult to pinpoint because of dust in the bulge. P1 and P2 are comparable in mass. Within a radius r = 1 00 of P2, the relative mass fraction of the nuclear components is M . : M bulge : P1 : P2 = 4.3 : 1.2 : 1 : 0.7, assuming the luminous components have a common mass-to-light ratio of 5.7. The eccentric disk as a whole (P1 + P2) is massive, M % 2.1 Â 10 7 M , comparable to the black hole and the local bulge mass. As such, the eccentric disk could not have been formed entirely out of stars that were stripped from an inbounding star cluster. Hence, the more favored scenario is that of a disk formed in situ by an m = 1 perturbation caused possibly by the passing of a giant molecular cloud or the passing/ accretion of a small globular cluster.

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The nucleus of M31

Cited by 95 publications

References 0 publications

Long-lived Lopsided Modes of Annular Disks Orbiting a Central Mass

Long-lived Lopsided Modes of Annular Disks Orbiting a Central Mass

The M 31 double nucleus probed with OASIS and HST

Assessing Formation Scenarios for the Double Nucleus of M31 Using Two-Dimensional Image Decomposition

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