Galaxy And Mass Assembly (GAMA): Stellar-to-Dynamical Mass Relation I. Constraining the Precision of Stellar Mass Estimates

In this empirical work, we aim to quantify the systematic uncertainties in stellar mass $(M_\star)$ estimates made from spectral energy distribution (SED) fitting through stellar population synthesis (SPS), for galaxies in the local Universe, by using the dynamical mass $(M_\text{dyn})$ estimator as an SED-independent check on stellar mass. We first construct a statistical model of the high dimensional space of galaxy properties; size $(R_e)$, velocity dispersion $(\sigma_e)$, surface brightness $(I_e)$, mass-to-light ratio $(M_\star/L)$, rest-frame colour, S\'ersic index $(n)$ and dynamical mass $(M_\text{dyn})$; accounting for selection effects and covariant errors. We disentangle the correlations among galaxy properties and find that the variation in $M_\star/M_\text{dyn}$ is driven by $\sigma_e$, S\'ersic index and colour. We use these parameters to calibrate an SED-independent $M_\star$ estimator, $\hat{M}_\star$. We find the random scatter of the relation $M_\star-\hat{M}_\star$ to be $0.108\text{dex}$ and $0.147\text{dex}$ for quiescent and star-forming galaxies respectively. Finally, we inspect the residuals as a function of SPS parameters (dust, age, metallicity, star formation rate) and spectral indices (H$\alpha$, H$\delta$, $D_n4000)$. For quiescent galaxies, $\sim65\%$ of the scatter can be explained by the uncertainty in SPS parameters, with dust and age being the largest sources of uncertainty. For star-forming galaxies, while age and metallicity are the leading factors, SPS parameters account for only $\sim13\%$ of the scatter. These results leave us with remaining unmodelled scatters of $0.055\text{dex}$ and $0.122\text{dex}$ for quiescent and star-forming galaxies respectively. This can be interpreted as a conservative limit on the precision in $M_\star$ that can be achieved via simple SPS-modelling.Comment: Accepted for publication in the Astrophysical Journal on 14 June 202

Galaxy and Mass Assembly (GAMA): Stellar-to-dynamical Mass Relation. II. Peculiar Velocities

Empirical correlations connecting starlight to galaxy dynamics (e.g., the fundamental plane (FP) of elliptical/quiescent (Q) galaxies and the Tully–Fisher relation of spiral/star-forming (SF) galaxies) provide cosmology-independent distance estimation and are central to local Universe cosmology. In this work, we introduce the mass hyperplane (MH), which is the stellar-to-dynamical mass relation (M ⋆/M dyn) recast as a linear distance indicator. Building on recent FP studies, we show that both SF and Q galaxies follow the same empirical MH, then use this to measure the peculiar velocities (PVs) for a sample of 2496 galaxies at z < 0.12 from GAMA. The limiting precision of MH-derived distance/PV estimates is set by the intrinsic scatter in size, which we find to be ≈0.1 dex for both Q and SF galaxies (when modeled independently) and ≈0.11 dex when all galaxies are modeled together, showing that the MH is as good as the FP. To empirically validate our framework and distance/PV estimates, we compare the inferred distances to groups as derived using either Q or SF galaxies. A good agreement is obtained with no discernible bias or offset, having a scatter of ≈0.05 dex ≈12% in distance. Further, we compare our PV measurements for the Q galaxies to the previous PV measurements of the galaxies in common between GAMA and the Sloan Digital Sky Survey, which shows similarly good agreement. Finally, we provide comparisons of PV measurements made with the FP and the MH, then discuss possible improvements in the context of upcoming surveys such as the 4MOST Hemisphere Survey

Galaxy and Mass Assembly (GAMA): Stellar-to-dynamical Mass Relation. II. Peculiar Velocities

Acknowledgements: K.S. acknowledges support from the Australian Government through the Australian Research Council's Laureate Fellowship funding scheme (project FL180100168).Abstract Empirical correlations connecting starlight to galaxy dynamics (e.g., the fundamental plane (FP) of elliptical/quiescent (Q) galaxies and the Tully–Fisher relation of spiral/star-forming (SF) galaxies) provide cosmology-independent distance estimation and are central to local Universe cosmology. In this work, we introduce the mass hyperplane (MH), which is the stellar-to-dynamical mass relation (M ⋆/M dyn) recast as a linear distance indicator. Building on recent FP studies, we show that both SF and Q galaxies follow the same empirical MH, then use this to measure the peculiar velocities (PVs) for a sample of 2496 galaxies at z &lt; 0.12 from GAMA. The limiting precision of MH-derived distance/PV estimates is set by the intrinsic scatter in size, which we find to be ≈0.1 dex for both Q and SF galaxies (when modeled independently) and ≈0.11 dex when all galaxies are modeled together, showing that the MH is as good as the FP. To empirically validate our framework and distance/PV estimates, we compare the inferred distances to groups as derived using either Q or SF galaxies. A good agreement is obtained with no discernible bias or offset, having a scatter of ≈0.05 dex ≈12% in distance. Further, we compare our PV measurements for the Q galaxies to the previous PV measurements of the galaxies in common between GAMA and the Sloan Digital Sky Survey, which shows similarly good agreement. Finally, we provide comparisons of PV measurements made with the FP and the MH, then discuss possible improvements in the context of upcoming surveys such as the 4MOST Hemisphere Survey.</jats:p

Galaxy And Mass Assembly (GAMA): Data Release 4 and the z < 0.1 total and z < 0.08 morphological galaxy stellar mass functions

In Galaxy And Mass Assembly Data Release 4 (GAMA DR4), we make available our full spectroscopic redshift sample. This includes 248 682 galaxy spectra, and, in combination with earlier surveys, results in 330 542 redshifts across five sky regions covering ∼250 deg2. The redshift density, isthe highest available over such a sustained area, has exceptionally high completeness (95 per cent to rKiDS = 19.65 mag), and is well-suited for the study of galaxy mergers, galaxy groups, and the low redshift (z < 0.25) galaxy population. DR4 includes 32 value-added tables or Data Management Units (DMUs) that provide a number of measured and derived data products including GALEX, ESO KiDS, ESO VIKING, WISE, and Herschel Space Observatory imaging. Within this release, we provide visual morphologies for 15 330 galaxies to z < 0.08, photometric redshift estimates for all 18 million objects to rKiDS ∼ 25 mag, and stellar velocity dispersions for 111 830 galaxies. We conclude by deriving the total galaxy stellar mass function (GSMF) and its sub-division by morphological class (elliptical, compact-bulge and disc, diffuse-bulge and disc, and disc only). This extends our previous measurement of the total GSMF down to 106.75 M h−2 70 and we find a total stellar mass density of ρ∗ = (2.97 ± 0.04) × 108 M h70 Mpc−3 or ∗ = (2.17 ± 0.03) × 10−3 h−1 70 . We conclude that at z < 0.1, the Universe has converted 4.9 ± 0.1 per cent of the baryonic mass implied by big bang Nucleosynthesis into stars that are gravitationally bound within the galaxy population