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MaNGA DynPop – V. The dark-matter fraction versus stellar velocity dispersion relation and stellar initial mass function variations in galaxies: dynamical models and full spectrum fitting of integral-field spectroscopy

Monthly Notices of the Royal Astronomical Society Oxford University Press (OUP) (2024)

Authors:

Shengdong Lu, Kai Zhu, Michele Cappellari, Ran Li, Shude Mao, Dandan Xu

Abstract:

Abstract Using the final MaNGA sample of 10K galaxies, we investigate the dark matter fraction fDM within one half-light radius Re for about 6K galaxies with good kinematics spanning a wide range of morphologies and stellar velocity dispersion. We employ two techniques to estimate fDM: (i) Jeans Anisotropic Modelling (JAM), which performs dark matter decomposition based on stellar kinematics and (ii) comparing the total dynamical mass-to-light ratios (M/L)JAM and (M*/L)SPS from Stellar Population Synthesis (SPS). We find that both methods consistently show a significant trend of increasing fDM with decreasing σe and low fDM at larger σe. For 235 early-type galaxies with the best models, we explore the variation of stellar initial mass function (IMF) by comparing the stellar mass-to-light ratios from JAM and SPS. We confirm that the stellar mass excess factor αIMF increases with σe, consistent with previous studies that reported a transition from Chabrier-like to Salpeter IMF among galaxies. We show that the αIMF trend cannot be driven by M*/L or IMF gradients as it persists when allowing for radial gradients in our model. We find no evidence for the total M/L increasing toward the centre. We detect weak positive correlations between αIMF and age, but no correlations with metallicity. We stack galaxy spectra according to their αIMF to search for differences in IMF-sensitive spectral features (e.g. the $\rm Na_{\rm I}$ doublet). We only find marginal evidence for such differences, which casts doubt on the validity of one or both methods to measure the IMF.
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WISDOM Project – XIX. Figures of merit for supermassive black hole mass measurements using molecular gas and/or megamaser kinematics

Monthly Notices of the Royal Astronomical Society Oxford University Press (OUP) (2024)

Authors:

Hengyue Zhang, Martin Bureau, Mark D Smith, Michele Cappellari, Timothy A Davis, Pandora Dominiak, Jacob S Elford, Fu-Heng Liang, Ilaria Ruffa, Thomas G Williams

Abstract:

Abstract The mass (MBH) of a supermassive black hole (SMBH) can be measured using spatially-resolved kinematics of the region where the SMBH dominates gravitationally. The most reliable measurements are those that resolve the smallest physical scales around the SMBHs. We consider here three metrics to compare the physical scales probed by kinematic tracers dominated by rotation: the radius of the innermost detected kinematic tracer Rmin normalised by respectively the SMBH’s Schwarzschild radius (RSchw ≡ 2GMBH/c2, where G is the gravitational constant and c the speed of light), sphere-of-influence (SOI) radius ($R_\mathrm{SOI}\equiv GM_\mathrm{BH}/\sigma _\mathrm{e}^2$, where σe is the stellar velocity dispersion within the galaxy’s effective radius) and equality radius (the radius Req at which the SMBH mass equals the enclosed stellar mass, MBH = M*(Req), where M*(R) is the stellar mass enclosed within the radius R). All metrics lead to analogous simple relations between Rmin and the highest circular velocity probed Vc. Adopting these metrics to compare the SMBH mass measurements using molecular gas kinematics to those using megamaser kinematics, we demonstrate that the best molecular gas measurements resolve material that is physically closer to the SMBHs in terms of RSchw but is slightly farther in terms of RSOI and Req. However, molecular gas observations of nearby galaxies using the most extended configurations of the Atacama Large Millimeter/sub-millimeter Array can resolve the SOI comparably well and thus enable SMBH mass measurements as precise as the best megamaser measurements.
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MaNGA DynPop – VI. Matter density slopes from dynamical models of 6000 galaxies versus cosmological simulations: The interplay between baryonic and dark matter

Monthly Notices of the Royal Astronomical Society Oxford University Press (OUP) (2024) stae838

Authors:

Shubo Li, Ran Li, Kai Zhu, Shengdong Lu, Michele Cappellari, Shude Mao, Chunxiang Wang, Liang Gao
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SDSS-IV MaNGA: Calibration of astrophysical line-widths in the Hα region using HexPak observations

Monthly Notices of the Royal Astronomical Society Oxford University Press (OUP) (2024) stae371

Authors:

Sabyasachi Chattopadhyay, Matthew A Bershady, David R Law, Kyle Westfall, Shravan Shetty, Camilo Machuca, Michele Cappellari, Kate HR Rubin, Kevin Bundy, Samantha Penny
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SDSS-IV MaNGA: Calibration of astrophysical line-widths in the H{\alpha} region using HexPak observations

(2024)

Authors:

Sabyasachi Chattopadhyay, Matthew A Bershady, David R Law, Kyle Westfall, Shravan Shetty, Camilo Machuca, Michele Cappellari, Kate HR Rubin, Kevin Bundy, Samantha Penny