The SAMI Galaxy Survey: flipping of the spin–filament alignment correlates most strongly with growth of the bulge
ABSTRACT

We study the alignments of galaxy spin axes with respect to cosmic web filaments as a function of various properties of the galaxies and their constituent bulges and discs. We exploit the SAMI Galaxy Survey to identify 3D spin axes from spatially resolved stellar kinematics and to decompose the galaxy into the kinematic bulge and disc components. The GAMA survey is used to reconstruct the cosmic filaments. The mass of the bulge, defined as the product of stellar mass and bulge-to-total flux ratio Mbulge = M⋆ × (B/T), is the primary parameter of correlation with spin–filament alignments: galaxies with lower bulge masses tend to have their spins parallel to the closest filament, while galaxies with higher bulge masses are more perpendicularly aligned. M⋆ and B/T separately show correlations, but they do not fully unravel spin–filament alignments. Other galaxy properties, such as visual morphology, stellar age, star formation activity, kinematic parameters, and local environment, are secondary tracers. Focussing on S0 galaxies, we find preferentially perpendicular alignments, with the signal dominated by high-mass S0 galaxies. Studying bulge and disc spin–filament alignments separately reveals additional information about the formation pathways of the corresponding galaxies: bulges tend to have more perpendicular alignments, while discs show more »

Authors:
; ; ; ; ; ; ; ; ; ;
Publication Date:
NSF-PAR ID:
10372110
Journal Name:
Monthly Notices of the Royal Astronomical Society
Volume:
516
Issue:
3
Page Range or eLocation-ID:
p. 3569-3591
ISSN:
0035-8711
Publisher:
Oxford University Press
We present the first detection of mass-dependent galactic spin alignments with local cosmic filaments with >2σ confidence using IFS kinematics. The 3D network of cosmic filaments is reconstructed on Mpc scales across GAlaxy and Mass Assembly fields using the cosmic web extractor DisPerSe. We assign field galaxies from the SAMI survey to their nearest filament segment in 3D and estimate the degree of alignment between SAMI galaxies’ kinematic spin axis and their nearest filament in projection. Low-mass galaxies align their spin with their nearest filament while higher mass counterparts are more likely to display an orthogonal orientation. The stellar transition mass from the first trend to the second is bracketed between $10^{10.4}$ and $10^{10.9}\, \mathrm{ M}_{\odot }$, with hints of an increase with filament scale. Consistent signals are found in the Horizon-AGN cosmological hydrodynamic simulation. This supports a scenario of early angular momentum build-up in vorticity rich quadrants around filaments at low stellar mass followed by progressive flip of spins orthogonal to the cosmic filaments through mergers at high stellar mass. Conversely, we show that dark matter only simulations post-processed with a semi-analytical model treatment of galaxy formation struggles to reproduce this alignment signal. This suggests that gas physicsmore »
3. ABSTRACT Galaxy internal structure growth has long been accused of inhibiting star formation in disc galaxies. We investigate the potential physical connection between the growth of dispersion-supported stellar structures (e.g. classical bulges) and the position of galaxies on the star-forming main sequence at z ∼ 0. Combining the might of the SAMI and MaNGA galaxy surveys, we measure the λRe spin parameter for 3289 galaxies over $9.5 \lt \log M_{\star } [\rm {M}_{\odot }] \lt 12$. At all stellar masses, galaxies at the locus of the main sequence possess λRe values indicative of intrinsically flattened discs. However, above $\log M_{\star }[\rm {M}_{\odot }]\sim 10.5$ where the main sequence starts bending, we find tantalizing evidence for an increase in the number of galaxies with dispersion-supported structures, perhaps suggesting a connection between bulges and the bending of the main sequence. Moving above the main sequence, we see no evidence of any change in the typical spin parameter in galaxies once gravitationally interacting systems are excluded from the sample. Similarly, up to 1 dex below the main sequence, λRe remains roughly constant and only at very high stellar masses ($\log M_{\star }[\rm {M}_{\odot }]\gt 11$), do we see a rapid decrease in λRemore »
We employ a series of high-resolution zoom-in cosmological simulations to analyse the emerging morphology of main galaxies in dark matter haloes at z ≳ 2. We choose haloes of similar masses, ${\rm log}\, M_{\rm vir}/{\rm M_\odot }\sim 11.65\pm 0.05$, at the target zf = 6, 4, and 2. The rationale for this choice allows us to analyse how the different growth rate in these haloes propagates down to galaxy scales, affecting their basic parameters. Halos were embedded in high/low overdensity regions, and two versions of a galactic wind feedback were employed. Our main results are: (1) Although our galaxies evolve in different epochs, their global parameters remain within narrow range. Their morphology, kinematics, and stellar populations differ substantially, yet all host sub-kpc stellar bars; (2) The star formation rates appear higher for larger zf; (3) Bulges and stellar spheroids were separated by stellar kinematics, discy bulges were revealed using the Sersic method and photometry.The bulge-to-total mass ratios appear independent of the last merger time for all zf. The spheroid-to-total mas ratios lie within ∼0.5–0.8; (4) The synthetic redshifted, pixelized, and PSF-degraded JWST images allow detection of stellar discs at all zf. (5) Based on the kinematic decomposition, rotational support inmore »