Is the standard elliptical NGC 3379 a triaxial disk galaxy?

A variety of host galaxy ( bulge) parameters are examined in order to determine their predictive power in ascertaining the masses of the supermassive black holes (SMBHs) at the centers of the galaxies. Based on a sample of 23 nearby galaxies, comprised of both elliptical galaxies and spiral /lenticular bulges, we identify a strong correlation between the bulge gravitational binding energy (E g ), as traced by the stellar light profile, and the SMBH mass (M ), such that M / E 0:6 g . The scatter about the relationship indicates that this is as strong a predictor of M as the velocity dispersion (), for the elliptical galaxy subsample. Improved mass-to-light ratios, obtained with IFU spectroscopy and I-band photometry by the SAURON group, were used for those sample galaxies where available, resulting in an energy predictor with the same slope, but with reduced scatter. Alternative M predictors such as the gravitational potential and the bulge mass are also explored, but these are found to be inferior when compared with both the bulge gravitational binding energy and bulge velocity dispersion predictors, for the full galaxy sample.

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“…b Capaccioli et al (1991) give a value of 31.5 based on an estimate of the disk. c Scorza & van den Bosch (1998) give 83 for the nuclear disk.…”

Section: Galaxymentioning

confidence: 99%

Host Galaxy Bulge Predictors of Supermassive Black Hole Mass

Aller

Richstone

2007

ApJ

117

153

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“…The possibility that NGC 3379 is actually not a true elliptical, but a nearly face-on S0 galaxy, has been raised on the basis of the details of its light distribution (e.g., Capaccioli et al 1991;Statler & Smecker-Hane 1999). Interestingly, the globular clusters provide some circumstantial evidence consistent with such an interpretation: the very low specific frequency S N ' 1:2 would not be unusual for an S0 or a large disk galaxy, but is certainly on the extreme low end for true ellipticals.…”

Section: Comparison With Globular Clustersmentioning

confidence: 99%

“…Its velocity field and dynamical structure are well behaved out to R gc $ 90 00 ' 2R e (Shapiro et al 2006) and large-scale surface photometry shows no shells or other remnants of mergers or accretions (Schweizer & Seitzer 1992) and very little gas (see Statler & Smecker-Hane 1999 for a review). The possibility has been discussed that it may actually be an S0 or modestly triaxial configuration seen nearly face-on, since the right combinations of disk, bulge, and inclination angle could mimic a global r 1/4 profile (Statler & Smecker-Hane 1999;Capaccioli et al 1991;Shapiro et al 2006). The velocity field within R < R e may also be more consistent with an S0 structure (Statler & Smecker-Hane 1999).…”

Section: Introductionmentioning

confidence: 99%

The Leo Elliptical NGC 3379: A Metal‐Poor Halo Emerges

Harris¹,

Harris²,

Layden³

et al. 2007

ApJ

120

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We have used the ACS camera on HST to obtain (V, I ) photometry for 5300 red giant stars in the halo of the dominant Leo group member NGC 3379, a galaxy usually regarded as a classic normal giant elliptical. We use this data to derive the metallicity distribution function ( MDF ) for its outer-halo field stars at a location centered 33 kpc from the galaxy center. In at least two ways the MDF is distinctly unlike all the other E galaxies for which similar data exist. First, the NGC 3379 MDF is extremely broad and flat, with many stars at every interval in [m / H ]. Second, we see a metallicity gradient such that in ithe outermost parts of the field the low-metallicity stars (½m/H < À0:7) begin to dominate and the higher metallicity stars are rapidly diminishing. We find that a distinct two-stage chemical evolution model is necessary to explain the MDF shape. Our target field is centered at a projected distance of 12R e , twice as far out in units of effective radius as in any of the other galaxies yet surveyed. If NGC 3379 is indeed representative of large E/S0 galaxies, we predict that other such galaxies will reveal diffuse low-metallicity subpopulations, but that photometry at radii r ' (10Y15)R e will be necessary to get beyond the edge of the dominant metal-rich component.

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“…; Capaccioli et al 1991, hereafter CVHL) have argued, mainly on photometric grounds, that NGC 3379 could be a misclassiÐed S0 galaxy seen close to face-on. CVHL demonstrate that a deprojected spheroid]disk model for the edge-on S0 galaxy NGC 3115, seen face-on, would show deviations from the best-Ðt r1@4 law very similar to the D0.1 mag ripple-like residuals seen in NGC 3379.…”

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confidence: 99%

The Stellar Kinematic Fields of NGC 3379

Statler

Smecker-Hane

1999

The Astronomical Journal

106

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We have measured the stellar kinematic proÐles of NGC 3379 along four position angles, using absorption lines in spectra obtained with the Multiple Mirror Telescope. We derive a far more detailed description of the kinematic Ðelds through the main body of the galaxy than could be obtained from previous work. Our data extend 90A from the center, at essentially seeing-limited resolution out to 17A. The derived mean velocities and dispersions have total errors (internal and systematic) better than^10 km s~1, and frequently better than 5 km s~1, out to 55A. We Ðnd very weak (3 km s~1) rotation on the minor axis interior to 12A and no detectable rotation above 6 km s~1 from 12A to 50A or above 16 km s~1 out to 90A (95% conÐdence limits). However, a Fourier reconstruction of the mean velocity Ðeld from all four sampled PAs does indicate a D5¡ twist of the kinematic major axis, in the direction opposite to the known isophotal twist. The and parameters are found to be generally small over h 3 h 4 the entire observed region. The azimuthally averaged dispersion proÐle joins smoothly at large radii with the velocity dispersions of planetary nebulae. Unexpectedly, we Ðnd sharp bends in the major axis rotation curve, also visible (though less pronounced) on the diagonal position angles. The outermost bend closely coincides in position with other sharp kinematic features : an abrupt Ñattening of the dispersion proÐle, and local peaks in and All of these features are in a photometrically interesting region in h 3 h 4 . which the surface brightness proÐle departs signiÐcantly from an r1@4 law. Features such as these are not generally known in elliptical galaxies owing to a lack of data at comparable resolution. Very similar behavior, however, is seen the kinematics of the edge-on S0 galaxy NGC 3115. We discuss the suggestion that NGC 3379 could be a misclassiÐed S0 galaxy ; preliminary results from dynamical modeling indicate that it may be a Ñattened, weakly triaxial system seen in an orientation that makes it appear round.

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Is the standard elliptical NGC 3379 a triaxial disk galaxy?

Cited by 35 publications

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Host Galaxy Bulge Predictors of Supermassive Black Hole Mass

Host Galaxy Bulge Predictors of Supermassive Black Hole Mass

The Leo Elliptical NGC 3379: A Metal‐Poor Halo Emerges

The Stellar Kinematic Fields of NGC 3379

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