Question How do stars form?

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If stars are sucked into supermassive Condensates (Black Holes). We know they form Dipolar Electromagnetic Vortices and it is possible to expel such matter along the vortices. This matter engages in the formation of stars.
M87 is an elliptical Galaxy far greater than Andromeda and the Milky way combined, M87 jets have millions of stars within the vortices.

[Submitted on 6 Feb 2024 (v1), last revised 12 Apr 2024 (this version, v2)]

Multiphase gas in elliptical galaxies: the role of Type Ia supernovae​

Rajsekhar Mohapatra, Eliot Quataert
Massive elliptical galaxies harbor large amounts of hot gas (T≳106 K) in their interstellar medium (ISM) but are typically quiescent in star formation. Active-galactic nuclei (AGNs) jets and Type Ia supernovae (SNIa) inject energy into the ISM which offsets its radiative losses and keeps it hot. SNIa deposit their energy locally within the galaxy compared to the larger few×10 kpc-scale AGN jets. In this study, we perform high-resolution (5123) hydrodynamic simulations of a local (1 kpc3) density-stratified patch of massive galaxies' ISM. We include radiative cooling and shell-averaged volume heating, as well as randomly exploding SNIa. We study the effect of different fractions of supernova heating (with respect to the net cooling rate), different initial ISM density/entropy (which controls the thermal-instability growth time tti) and different degrees of stratification (which affects the free-fall time tff). We find that the SNIa drive predominantly compressive turbulence in the ISM with a velocity dispersion σv up to 40 kms−1 and logarithmic density dispersion σs∼0.2--0.4. These fluctuations trigger multiphase condensation in regions of the ISM where min(tti)/tff≲0.6exp(6σs), in agreement with theoretical expectations that large density fluctuations efficiently trigger multiphase gas formation. Since the SNIa rate is not self-adjusting, when the net cooling drops below the net heating rate the SNIa drive a hot wind which sweeps out most of the mass in our local model. Global simulations are required to assess the ultimate fate of this gas.
 
I do not agree with this paper.
But! interesting to read.


[Submitted on 28 May 2024]

Magnetic Braneworlds: Cosmology and Wormholes​

Stefano Antonini, Luis Gabriel C. Bariuan
We construct 4D flat Big Bang-Big Crunch cosmologies and Anti-de Sitter (AdS) planar eternally traversable wormholes using braneworlds embedded in asymptotically AdS5 spacetimes. The background geometries are the AdS5 magnetic black brane and the magnetically charged AdS5 soliton, respectively. The two setups arise from different analytic continuations of the same saddle of the gravitational Euclidean path integral, in which the braneworld takes the form of a Maldacena-Maoz Euclidean wormhole. We show the existence of a holographic dual description of this setup in terms of a microscopic Euclidean boundary conformal field theory (BCFT) on a strip. By analyzing the BCFT Euclidean path integral, we show that the braneworld cosmology is encoded in a pure excited state of a CFT dual to a black brane microstate, whereas the braneworld wormhole is encoded in the ground state of the BCFT. The latter confines in the IR, and we study its confining properties using holography. We also comment on the properties of bulk reconstruction in the two Lorentzian pictures and their relationship via double analytic continuation. This work can be interpreted as an explicit, doubly-holographic realization of the relationship between cosmology, traversable wormholes, and confinement in holography, first proposed in arXiv:2102.05057, arXiv:2203.11220.
 
Star formation is important because it allows to understand the workings of the universe.


[Submitted on 26 Apr 2024]

Inefficient star formation in high Mach number environments. II. Numerical simulations and comparison with analytical models​

Noé Brucy, Patrick Hennebelle, Tine Colman, Ralf S. Klessen, Corentin Le Yhuelic
Predicting the star formation rate (SFR) in galaxies is crucial to understand their evolution and morphology. To do so requires a fine understanding of how dense structures of gas are created and collapse. In that, turbulence and gravity play a major role. Within the gravo-turbulent framework, we assume that turbulence shapes the ISM, creating density fluctuations that, if gravitationally unstable, will collapse and form stars. The goal of this work is to quantify how different regimes of turbulence, characterized by the strength and compressibility of the driving, shape the density field. We are interested in the outcome in terms of SFR and how it compares with existing analytical models for the SFR. We run a series of hydrodynamical simulations of turbulent gas. The simulations are first conducted without gravity, so that the density and velocity are shaped by the turbulence driving. Gravity is then switched on, and the SFR is measured and compared with analytical models. The physics included in these simulations is very close to the one assumed in the classical gravo-turbulent SFR analytical models, which makes the comparison straightforward. We found that the existing analytical models convincingly agree with simulations at low Mach number, but we measure a much lower SFR in the simulation with a high Mach number. We develop, in a companion paper, an updated physically-motivated SFR model that reproduces well the inefficient high Mach regime of the simulations. Our work demonstrates that accurate estimations of the turbulent-driven replenishment time of dense structures and the dense gas spatial distribution are necessary to correctly predict the SFR in the high Mach regime. The inefficient high-Mach regime is a possible explanation for the low SFR found in dense and turbulent environments such as the centers of our Milky Way and other galaxies.
 
For those that want to read.
Reseach keeps moving forward. Sometime one step back and then forward.

[Submitted on 14 May 2024]

The evolution of stellar X-ray activity and angular momentum as seen by eROSITA, TESS, and Gaia​

Keivan G. Stassun (1), Marina Kounkel (2) ((1) Vanderbilt University, (2) University of North Florida)
We have assembled a sample of ∼8200 stars with spectral types F5V-M5V, all having directly measured X-ray luminosities from eROSITA and rotation periods from TESS, and having empirically estimated ages via their membership in stellar clusters and groups identified in Gaia astrometry (ages 3-500 Myr). This is the largest such study sample yet assembled for the purpose of empirically constraining the evolution of rotationally driven stellar X-ray activity. We observe rotation-age-activity correlations that are qualitatively as expected: stars of a given spectral type spin down with age and they become less X-ray active as they do so. We provide simple functional representations of these empirical relationships that predict X-ray luminosity from basic observables to within 0.3 dex. Interestingly, we find that the rotation-activity relationship is far simpler and more monotonic in form when expressed in terms of stellar angular momentum instead of rotation period. We discuss how this finding may relate to the long-established idea that rotation-activity relationships are mediated by stellar structure (e.g., convective turnover time, surface area). Finally, we provide an empirical relation that predicts stellar angular momentum from basic observables, and without requiring a direct measurement of stellar rotation, to within 0.5 dex.
 
Star formation is important in finding how they are produced in large numbers.

[Submitted on 8 May 2024]

A Gamma-ray Emitting Collisional Ring Galaxy System in our Galactic Neighborhood​

Vaidehi S. Paliya, D. J. Saikia (IUCAA)
The astrophysical γ-ray photons carry the signatures of the violent phenomena happening on various astronomical scales in our Universe. This includes supernova remnants, pulsars, and pulsar wind nebulae in the Galactic environment and extragalactic relativistic jets associated with active galactic nuclei (AGN). However, ∼30\% of the \gm-ray sources detected with the Fermi Large Area Telescope lack multiwavelength counterpart association, precluding us from characterizing their origin. Here we report, for the first time, the association of a collisional ring galaxy system in our Galactic neighborhood (distance ∼10 Mpc), formed as a consequence of a smaller `bullet' galaxy piercing through a larger galaxy, as the multi-frequency counterpart of an unassociated γ-ray source 4FGL~J1647.5−5724. The system, also known as "Kathryn's Wheel", contains two dwarf irregular galaxies and an edge-on, late-type, spiral galaxy surrounded by a ring of star-forming knots. We utilized observations taken from the Neil Gehrels Swift observatory, Rapid ASKAP Continuum Survey, SuperCOSMOS Hα Survey, Dark Energy Survey, and Visible MultiObject Spectrograph at Very Large Telescope to ascertain the association with 4FGL~J1647.5−5724 and to explore the connection between the star-forming activities and the observed γ-ray emission. We found that star-formation alone cannot explain the observed γ-ray emission, and additional contribution likely from the pulsars/supernova remnants or buried AGN is required. We conclude that arcsecond/sub-arcsecond-scale observations of this extraordinary γ-ray emitting galaxy collision will be needed to resolve the environment and explore the origin of cosmic rays.
 
Star formation rates (SFR) is important to keep researching and their relation to Active Galactic Nuclei (AGN)

[Submitted on 15 May 2024]

Active Galactic Nuclei and STaR fOrmation in Nearby Galaxies (AGNSTRONG). I. Sample and Strategy​

Huynh Anh N. Le, Chen Qin, Yongquan Xue, Shifu Zhu, Kim Ngan N. Nguyen, Ruisong Xia, Xiaozhi Lin
We introduce our project, AGNSTRONG (Active Galactic Nuclei and STaR fOrmation in Nearby Galaxies). Our research goals encompass investigating the kinematic properties of ionized and molecular gas outflows, understanding the impact of AGN feedback, and exploring the coevolution dynamics between AGN strength activity and star formation activity. We aim to conduct a thorough analysis to determine whether there is an increase or suppression in SFRs among targets with and without powerful relativistic jets. Our sample consists of 35 nearby AGNs with and without powerful relativistic jet detections. Utilizing sub-millimeter (sub-mm) continuum observations at 450 {\mu}m and 850 {\mu}m from SCUBA-2 at the James Clerk Maxwell Telescope, we determine star-formation rates (SFRs) for our sources using spectral energy distribution (SED) fitting models. Additionally, we employ high-quality, spatially resolved spectra from UV-optical to near-infrared bands obtained with the Double Spectrograph and Triple Spectrograph mounted on the 200-inch Hale telescope at Palomar Observatory to study their multiphase gas outflow properties. This paper presents an overview of our sample selection methodology, research strategy, and initial results of our project. We find that the SFRs determined without including the sub-mm data in the SED fitting are overestimated by approximately 0.08 dex compared to those estimated with the inclusion of sub-mm data. Additionally, we compare the estimated SFRs in our work with those traced by the 4000Å break, as provided by the MPA-JHU catalog. We find that our determined SFRs are systematically higher than those traced by the 4000Å break. Finally, we outline our future research plans.