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Articles 1 - 9 of 9
Full-Text Articles in Physical Sciences and Mathematics
Self-Regulated Fueling Of Galaxy Centers: Evidence For Star Formation Feedback, E Schinnerer, T Boker, Ds Meier, D Calzetti
Self-Regulated Fueling Of Galaxy Centers: Evidence For Star Formation Feedback, E Schinnerer, T Boker, Ds Meier, D Calzetti
Astronomy Department Faculty Publication Series
Using new, high-resolution interferometric observations of the CO and HCN molecules, we directly compare the molecular and ionized components of the interstellar medium in the center of the nearby spiral galaxy IC 342, on spatial scales of 10 pc. The morphology of the tracers suggests that the molecular gas flow caused by a large-scale stellar bar has been strongly affected by the mechanical feedback from recent star formation activity within the central 100 pc in the nucleus of the galaxy. Possibly, stellar winds and/or supernova shocks originating in the nuclear star cluster have compressed, and likely pushed outward, the infalling …
The Dynamics Of Tidal Tails From Massive Satellites, Jh Choi, Md Weinberg, N Katz
The Dynamics Of Tidal Tails From Massive Satellites, Jh Choi, Md Weinberg, N Katz
Astronomy Department Faculty Publication Series
We investigate the dynamical mechanisms responsible for producing tidal tails from dwarf satellites using N-body simulations. We describe the essential dynamical mechanisms and morphological consequences of tail production in satellites with masses greater than 0.0001 of the host halo virial mass. We identify two important dynamical coconspirators: (1) the points where the attractive force of the host halo and satellite are balanced (X-points) do not occur at equal distances from the satellite centre or at the same equipotential value for massive satellites, breaking the morphological symmetry of the leading and trailing tails and (2) the escaped ejecta in the leading …
Bar-Induced Evolution Of Dark Matter Cusps, K Holley-Bockelmann, M Weinberg, N Katz
Bar-Induced Evolution Of Dark Matter Cusps, K Holley-Bockelmann, M Weinberg, N Katz
Astronomy Department Faculty Publication Series
The evolution of a stellar bar transforms not only the galactic disc, but also the host dark matter halo. We present high-resolution, fully self-consistent N-body simulations that clearly demonstrate that dark matter halo central density cusps flatten as the bar torques the halo. This effect is independent of the bar formation mode and occurs even for rather short bars. The halo and bar evolution is mediated by resonant interactions between orbits in the halo and the bar pattern speed, as predicted by linear Hamiltonian perturbation theory. The bar lengthens and slows as it loses angular momentum, a process that occurs …
Bar-Driven Dark Halo Evolution: A Resolution Of The Cusp-Core Controversy, Md Weinberg, N Katz
Bar-Driven Dark Halo Evolution: A Resolution Of The Cusp-Core Controversy, Md Weinberg, N Katz
Astronomy Department Faculty Publication Series
Simulations predict that the dark matter halos of galaxies should have central cusps, while those inferred from observed galaxies do not have cusps. We demonstrate, using both linear perturbation theory and n-body simulations, that a disk bar, which should be ubiquitous in forming galaxies, can produce cores in cuspy cold dark matter profiles within five bar orbital times. Simulations of forming galaxies suggest that one of Milky Way size could have a 10 kpc primordial bar; this bar will remove the cusp out to ~2.5 kpc in ~1.5 Gyr, while the disk would lose only ~8% of its original angular …
Noise-Driven Evolution In Stellar Systems - Ii. A Universal Halo Profile, Md Weinberg
Noise-Driven Evolution In Stellar Systems - Ii. A Universal Halo Profile, Md Weinberg
Astronomy Department Faculty Publication Series
Disc instabilities such as arm and bar formation, minor mergers and tidal encounters drive a galaxy from equilibrium. Using the theory that describes the evolution of a galaxy halo as a result of stochastic fluctuations developed in the companion paper to this one, we show that this sort of noise evolves a halo toward a standard profile, independent of its initial profile and concentration. This process can substantially redistribute the mass in dark-matter haloes in the 10 Gyr since formation. Three different noise processes are studied: (i) a bombardment by blobs of mass that are small compared to the halo …
Noise-Driven Evolution In Stellar Systems - I. Theory, Md Weinberg
Noise-Driven Evolution In Stellar Systems - I. Theory, Md Weinberg
Astronomy Department Faculty Publication Series
We present a theory for describing the evolution of a galaxy caused by stochastic events such as weak mergers, transient spiral structure, orbiting blobs, etc. This noise excites large-scale patterns that drive the evolution of the galactic density profile. In a dark matter halo, the repeated stochastic perturbations preferentially ring the lowest-order modes with only a very weak dependence on the details of their source. The subsequent redistribution of halo mass is determined only by the mechanics of these modes. The halo profile then evolves toward a universal asymptotic form for a wide variety of noise sources. Such a convergence …
Perturbations Of Spherical Stellar Systems During Flyby Encounters, E Vesperini, Md Weinberg
Perturbations Of Spherical Stellar Systems During Flyby Encounters, E Vesperini, Md Weinberg
Astronomy Department Faculty Publication Series
We study the internal response of a galaxy to an unbound encounter and present a survey of orbital parameters covering typical encounters in different galactic environments. Overall, we conclude that relatively weak encounters by low-mass interloping galaxies can cause observable distortions in the primaries. The resulting asymmetries may persist long after the interloper is evident. We focus our attention on the production of structure in dark halos and in cluster elliptical galaxies. Any distortion produced in a dark halo can distort the embedded stellar disk, possibly leading to the formation of lopsided and warped disks. We show that distant encounters …
Fluctuations In Finite-N Equilibrium Stellar Systems, Md Weinberg
Fluctuations In Finite-N Equilibrium Stellar Systems, Md Weinberg
Astronomy Department Faculty Publication Series
Gravitational amplification of Poisson noise in stellar systems is important on large scales. For example, it increases the dipole noise power by roughly a factor of 6 and the quadrupole noise by 50 per cent for a King model profile. The dipole noise is amplified by a factor of 15 for the core-free Hernquist model. The predictions are computed by summing over the wakes caused by each star in the system — the dressed-particle formalism of Rostoker & Rosenbluth — and are demonstrated by N-body simulation. This result implies that a collisionless N-body simulation is impossible; the fluctuation noise which …
Dynamics Of An Interacting Luminous Disc, Dark Halo And Satellite Companion, Md Weinberg
Dynamics Of An Interacting Luminous Disc, Dark Halo And Satellite Companion, Md Weinberg
Astronomy Department Faculty Publication Series
This paper describes a method, based on linear perturbation theory, to determine the dynamical interaction between extended halo and spheroid components and an environmental disturbance. One finds that resonant interaction between a galaxy and passing interlopers or satellite companions can carry the disturbance inward, deep inside the halo, where it can perturb the disc. Applied to the Milky Way for example, the LMC and SMC appear to be sufficient to cause the observed Galactic warp and possibly seed other asymmetries. This is a multi-scale interaction in which the halo wake has a feature at roughly half the satellite orbital radius …