arXiv subjects

Panos A. Patsis

Publications and source records attributed to Panos A. Patsis.

5 recordsLinked to original sources

arXiv2026

NOEMA$^\rm{3D}$: A deep view of cold gas flows in a barred spiral galaxy at $z\sim1$

We present a deep, high-resolution CO(4-3) IRAM-NOEMA observation of a main sequence, barred, spiral galaxy at $z\approx1.12$, with an on-source integration time of $\approx37$ hours and a beam FWHM of $\approx0.\!\!^{\prime\prime}3$. We use the molecular gas data in conjunction with the available deep multi-band JWST and HST imaging, covering restframe UV to near-IR wavelengths, to quantitatively study the gas flows in the disk plane of this cosmic noon barred spiral. We find that this target is a massive ($\log(M_{\rm{baryons}}/M_\odot)\approx10.96$), baryon-dominated ($f_{\rm{dm}}(<R_e)=u^2_{\rm{circ,dm}}(R_e)/u^2_{\rm{circ}}(R_e)\sim4\%$), gas-rich ($f_{\rm{gas}}=M_{\rm{gas}}/(M_{\rm{\star}}+M_{\rm{gas}})\approx40\%$) disk, hosting a long ($a_{\rm{bar}}\approx4.2$ kpc), strong ($Q_{\rm{b}}\approx0.37$), and fast ($\mathcal{R}=R_{\rm{CR}}/a_{\rm{bar}}\approx1.05$) bar, which rotates at an angular speed of $Ω_{\rm{pattern}}\approx$ 50 km/s/kpc. This bar is driving molecular gas inflows with a net inflow rate of $\dot{M}\sim30$ $M_\odot$/yr, based on three estimates, which is of the same order as the galaxy-integrated star formation rate ($\rm{SFR}\approx36$ $M_\odot$/yr). We additionally identify evidence of a well-defined dust lane shock at the northwestern side of the bar, with gas motions parallel to this feature, in agreement with expectations for an established bar-driven flow. Our study highlights the possible role of bars as key drivers of galaxy evolution for a significant fraction of cosmic noon galaxies, offering a detailed picture of well-defined, bar-driven inflows in a high-$z$ barred spiral.

astro-ph.GA↗

arXiv2026

Morphologies arising from the gas flow in the innermost kiloparsec of barred galaxy models

Context. We study a series of response models to investigate the formation of specific morphological features in the central 1 kpc region of the gas component in barred spiral galaxies. Aims. We aim to understand how structures, such as nuclear rings and spirals, form by varying the parameters of a general gravitational potential and gas properties. Our goal is to determine how much the shape of these structures is driven by the orbital dynamics of the models compared to the influence of the hydrodynamics of the gas. In particular, we examine the effects of the bar strength, bar shape, pattern speed, and central density, as well as their mutual interdependence. Methods. We modeled the gas flow using hydrodynamical simulations run with the Eulerian RAMSES code. The underlying gravitational potential was a two-dimensional Ferrers bar and the gas was considered to be isothermal. Alongside analyzing the gas response to the imposed gravitational potentials, we carried out orbital studies for all models. This involved assessing the shapes and stability of periodic orbits and analyzing the distribution of regular versus chaotic regions within the systems. Results. The parameters of the gravitational potential alone are insufficient to accurately predict the gas dynamics in a system. The morphology of the gaseous response varies substantially with changes in sound speed, emphasizing the fundamental role of hydrodynamic processes in determining the structure of the gas within the central region. We identify the factors that affect the morphology of nuclear rings and trailing and leading nuclear spirals. The best alignment between our models and structures observed in local barred galaxies is achieved by assuming a sound speed of $c_s=20\,\rm{km\,s^{-1}}$.

astro-ph.GA↗

arXiv2026

Gasflows in Barred Galaxies with Big Orbital Loops-A Comparative Study of Two Hydrocodes

We study the flow of gas in a barred-galaxy model, in which a considerable part of the underlying stable periodic orbits have loops where, close to the ends of the bar, several orbital families coexist and chaos dominates. Such conditions are typically encountered in a zone between the 4:1 resonance and corotation. The purpose of our study is to understand the gaseous flow in the aforementioned environment and trace the morphology of the shocks that form. We use two conceptually different hydrodynamic schemes for our calculations, namely, the mesh-free Lagrangian SPH method and the adaptive mesh refinement code RAMSES. This allows us to compare responses by means of the two algorithms. We find that the big loops of the orbits, mainly belonging to the x1 stable periodic orbits, do not help the shock loci to approach corotation. They deviate away from the regions occupied by the loops, bypass them and form extensions at an angle with the straight-line shocks. Roughly at the distance from the center at which we start to observe the big loops, we find characteristic "tails" of dense gas streaming towards the straight-line shocks. The two codes give complementary information for understanding the hydrodynamics of the models.

astro-ph.GA↗

arXiv2019

Spiral arm formation mechanisms: Spiral Structure in Barred galaxies. Observational constraints to spiral arm formation mechanisms

A method which we have developed for determining corotation radii, has allowed us to map in detail the radial resonant structures of barred spiral galaxies. Here we have combined this information with new determinations of the bar strength and the pitch angle of the innermost segment of the spiral arms to find relationships between these parameters of relevance to the dynamical evolution of the galaxies. We show how (1) the bar mass fraction, (2) the scaled bar angular momentum, (3) the pitch angle, and (4) the shear parameter vary along the Hubble sequence, and we also plot along the Hubble sequence (5) the scaled bar length, (6) the ratio of bar corotation radius to bar length, (7) the scaled bar pattern speed, and (8) the bar strength. It is of interest to note that the parameters (2), (5), (6), (7), and (8) all show breaks in their behaviour at type Scd. We find that bars with high shear have only small pitch angles, while bars with large pitch angles must have low shear; we also find a generally inverse trend of pitch angle with bar strength. An inference which at first seems counter-intuitive is that the most massive bars rotate most slowly but have the largest angular momenta. Among a further set of detailed results we pick out here the 2:1 ratio between the number of spiral arms and the number of corotations ouside that of the bar. These results give a guideline to theories of disc-bar evolution.

astro-ph.GA↗

arXiv2016

The dynamics of a spinning particle in a linear in spin Hamiltonian approximation

We investigate for order and chaos the dynamical system of a spinning test particle of mass $m$ moving in the spacetime background of a Kerr black hole of mass M. This system is approximated in our investigation by the linear in spin Hamiltonian function provided in [E. Barausse, and A. Buonanno, Phys.Rev. D 81, 084024 (2010)]. We study the corresponding phase space by using 2D projections on a surface of section and the method of color and rotation on a 4D Poincaré section. Various topological structures coming from the non-integrability of the linear in spin Hamiltonian are found and discussed. Moreover, an interesting result is that from the value of the dimensionless spin $S/(m M)=10^{-4}$ of the particle and below, the impact of the non-integrability of the system on the motion of the particle seems to be negligible.

gr-qc↗