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Date and Time of the Query: 2019-04-19 T18:34:03 PDT
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For refcode 2013ApJ...768L..21M:
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2013ApJ...768L..21M The Effect of Spatial Gradients in Stellar Mass-to-light Ratio on Black Hole Mass Measurements McConnell, Nicholas J.; Chen, Shi-Fan Stephen; Ma, Chung-Pei; Greene, Jenny E.; Lauer, Tod R.; Gebhardt, Karl Abstract. We have tested the effect of spatial gradients in stellar mass-to-light ratio (Upsilon) on measurements of black hole masses (M_blackhole_) derived from stellar orbit superposition models. Such models construct a static gravitational potential for a galaxy and its central black hole, but typically assume spatially uniform Upsilon. We have modeled three giant elliptical galaxies with gradients {alpha} = dlog (Upsilon)/dlog (r) from -0.2 to +0.1. Color and line strength gradients suggest mildly negative {alpha} in these galaxies. Introducing a negative (positive) gradient in Upsilon increases (decreases) the enclosed stellar mass near the center of the galaxy and leads to systematically smaller (larger) M_blackhole_ measurements. For models with {alpha} = -0.2, the best-fit values of M_blackhole_ are 28%, 27%, and 17% lower than the constant-Upsilon case, in NGC 3842, NGC 6086, and NGC 7768, respectively. For {alpha} = +0.1, M_blackhole_ are 14%, 22%, and 17% higher than the constant-Upsilon case for the three respective galaxies. For NGC 3842 and NGC 6086, this bias is comparable to the statistical errors from individual modeling trials. At larger radii, negative (positive) gradients in Upsilon cause the total stellar mass to decrease (increase) and the dark matter fraction within one effective radius to increase (decrease). Key words: galaxies: kinematics and dynamics
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