Related papers: On the Spiral Structures in Heavy-Ion Collisions
We summarize some recent results from our observational campaign to study the central regions of spiral galaxies of late Hubble type (Scd - Sm). These disk-dominated, bulgeless galaxies have an apparently uneventful merger history. The…
We analyse a sample of about 2000 galaxies in 40 regular clusters, to look for evidence of segregation with respect to galaxy luminosities and morphological types. We find evidence of luminosity segregation for galaxies brighter than $M_R <…
Stellar photometry obtained using the Hubble Space Telescope is used to study the distributions of the number densities of stars of various ages in 12 irregular and dwarf spiral galaxies viewed edge-on. Two subsystems can be distinguished…
Passive spiral galaxies, despite their spiral morphological appearance, do not have any emission lines indicative of ongoing star formation in their optical spectra. Previous studies have suggested that passive spiral galaxies…
We study transient spiral structures in an isothermal, thin, galactic disc. We find no instability that can grow everywhere from infinitesimal disturbances, but spiral structure does grow in the disc due to an arbitrarily strong,…
Identifying the structure of our Galaxy has always been fraught with difficulties, and while modern surveys continue to make progress building a map of the Milky Way, there is still much to understand. The arm and bar features are important…
We investigate thin and thick stellar disc formation in Milky-Way-mass galaxies using twelve FIRE-2 cosmological zoom-in simulations. All simulated galaxies experience an early period of bursty star formation that transitions to a late-time…
Irregular (Irr) galaxies are gas-rich objects with recent or ongoing star formation. In absence of spiral density waves, star formation occurs largely stochastically. The scattered star-forming regions tend to be long-lived and migrate…
It is now generally believed that galaxies were built up through gravitational amplification of primordial fluctuations and the subsequent merging of smaller precursor structures. The stars of the structures that assembled to form the Milky…
We have investigated the pitch angle ($\psi$) of the spiral arms of galaxies in the Hubble Space Telescope COSMOS field. The sample consists of 102 face-on galaxies with a two-armed pattern at a mean redshift $\langle z \rangle \approx…
The origin and types of spiral arms are reviewed with an emphasis on the connections between these arms and star formation. Flocculent spiral arms are most likely the result of transient instabilities in the gas that promote dense cloud…
We recently reported the discovery of a regular corrugation pattern in the HI disk of the isolated, edge-on spiral galaxy IC2233. Here we present measurements of the vertical structure of this galaxy at several additional wavelengths,…
In this series of papers, we propose a theory to explain the formation and properties of rings and spirals in barred galaxies. The building blocks of these structures are orbits guided by the manifolds emanating from the unstable Lagrangian…
Our Galaxy is a barred spiral. Recent work based on the COBE NIR data implies a small bulge-bar and a disk with a short scale-length. The corotation radius of the bar is in the range 3-4.5 kpc. The stellar density distribution beyond the…
We suggest that the bulge-to-disc ratios of spiral galaxies are primarily determined by the angular momenta of their host haloes predicted in current hierarchical clustering models for structure formation. Gas with low specific angular…
The dynamical nature and formation mechanism(s) of galactic spiral arms remain long-standing problems in astrophysics. Most theoretical work is based on analytic calculations or idealised simulations, which has yielded several theories of…
Multiple observations made by several different telescopes have shown asymmetry between the number of spiral galaxies rotating in opposite directions in different parts of the sky. One of the immediate questions regarding the possible…
Spiral arm properties of 46 galaxies in the Spitzer Survey of Stellar Structure in Galaxies (S4G) were measured at 3.6mu, where extinction is small and the old stars dominate. The sample includes flocculent, multiple arm, and grand design…
At high redshifts, star formation in galaxies is more often concentrated in clumps than in spiral arms. Although clumps are actively studied, it is rarely done considering spiral arms as objects for study as well, and the connection between…
Galaxies are not distributed randomly throughout space but are instead arranged in an intricate "cosmic web" of filaments and walls surrounding bubble-like voids. There is still no compelling observational evidence of a link between the…