About

Eve Ostriker is the Lyman Spitzer, Jr., Professor of Theoretical Astrophysics and Associate Chair of the Department of Astrophysical Sciences at Princeton University. Her research focuses on theoretical and computational astrophysics, particularly in the areas of star formation, the dynamics, thermodynamics, and chemistry of the interstellar medium and circumgalactic medium, the structure and evolution of spiral galaxies, and the physics of accretion and outflows. She is actively involved in developing numerical methods and tools for computational fluid dynamics. Her work aims to understand the physics behind a wide range of astronomical systems involving gas dynamics, from the formation and collapse of clouds to the creation of solar systems, to the energy and matter exchanges within the Milky Way and other spiral galaxies, and the regulation of star formation over the last ten billion years. An important aspect of her research is understanding and quantifying the roles of supersonic turbulence that pervades the universe.

Research topics

• Physics
• Astronomy
• Astrophysics

Selected publications

• Polycyclic Aromatic Hydrocarbon and CO(2–1) Emission at 50–150 pc Scales in 70 Nearby Galaxies

  The Astrophysical Journal · 2025-04-07 · 14 citations

  articleOpen access

  Abstract Combining Atacama Large Millimeter/submillimeter Array CO(2–1) mapping and JWST near- and mid-infrared imaging, we characterize the relationship between CO(2–1) and polycyclic aromatic hydrocarbon (PAH) emission at ≈100 pc resolution in 70 nearby star-forming galaxies. Leveraging a new Cycle 2 JWST Treasury program targeting nearby galaxies, we expand the sample size by more than an order of magnitude compared to previous ≈100 pc resolution CO–PAH comparisons. In regions of galaxies where most of the gas is likely to be molecular, we find strong correlations between CO(2–1) and 3.3 μ m, 7.7 μ m, and 11.3 μ m PAH emission, estimated from JWST’s F335M, F770W, and F1130W filters. We derive power-law relations between CO(2–1) and PAH emission, with indices in the range 0.8–1.3, implying relatively weak variations in the observed CO-to-PAH ratios across our sample. We find that CO-to-PAH ratios and scaling relationships near H ii regions are similar to those in diffuse sight lines. The main difference between the two types of regions is that sight lines near H ii regions show higher intensities in all tracers. Galaxy centers show higher overall intensities and enhanced CO-to-PAH ratios compared to galaxy disks. Individual galaxies show 0.19 dex scatter in the normalization of CO at fixed I PAH , and this normalization anticorrelates with specific star formation rate and correlates with stellar mass. We provide a prescription that accounts for galaxy-to-galaxy variations, representing our best current empirical predictor to estimate CO(2–1) intensity from PAH emission, allowing one to take advantage of JWST’s excellent sensitivity and resolution to trace cold gas.

  PublisherDOI

• Prestellar Cores in Turbulent Clouds: Observational Perspectives on Structure, Kinematics, and Lifetime

  The Astrophysical Journal · 2025-11-14

  articleOpen accessSenior author

  Abstract We analyze an ensemble of simulated prestellar cores to facilitate an interpretation of structure, kinematics, and lifetime of observed cores. While our theory predicts a “characteristic” density for star formation, it also predicts that the individual critical density varies among cores; any observed sample thus contains cores at various evolutionary stages within a given density bin. By analyzing the remaining lifetime, we find cores undergoing a quasi-equilibrium collapse evolve on a timescale of twice the freefall time throughout most of their life. Our analysis shows that the central column density and the associated full width at half-maximum provide a reasonably accurate observational estimator of the central volume density, and therefore the freefall time; this does, however, require resolving the central column density plateau. Observations with a finite beam size tend to underestimate densities of evolved cores, and this makes observed lifetimes appear to decrease more steeply than the apparent freefall time. We measure from our simulations the ratio of the prestellar duration to the envelope infall time, and find this is consistent with the observed relative number of prestellar cores and embedded protostars. Yet, the absolute core lifetime in our simulations is significantly shorter than would be expected from empirical measurements of the relative numbers of prestellar cores and Class II sources; we discuss several possible reasons for this discrepancy. Finally, our simulated cores have nearly constant line-of-sight velocity dispersion within the emitting region in the sky plane, resembling observed “coherent cores.” We show that this “coherence” is a consequence of projection effects, which mask the intrinsic power-law velocity structure function. We discuss possible ways to estimate line-of-sight path lengths.

  PublisherDOI

• Prestellar Cores in Turbulent Clouds: Numerical Modeling and Evolution to Collapse

  The Astrophysical Journal · 2025-06-30 · 4 citations

  articleOpen accessSenior author

  Abstract A fundamental issue in star formation is understanding the precise mechanisms leading to the formation of prestellar cores and their subsequent gravitationally unstable evolution. To address this question, we carefully construct a suite of turbulent, self-gravitating numerical simulations, and analyze the development and collapse of individual prestellar cores. We show that the numerical requirements for resolving the sonic scale and internal structure of anticipated cores are essentially the same in self-gravitating clouds, calling for the number of cells per dimension to increase quadratically with the cloud’s Mach number. In our simulations, we follow the evolution of individual cores by tracking the region around each gravitational potential minimum over time. Evolution in nascent cores is toward increasing density and decreasing turbulence, and there is a wide range of critical density for initiating collapse. At a given spatial scale, the turbulence level also varies widely and tends to be correlated with density. By directly measuring the radial forces acting within cores, we identify a distinct transition to a state of gravitational runaway. We use our new theory for turbulent equilibrium spheres to predict the onset of each core’s collapse. Instability is expected when the critical radius becomes smaller than the tidal radius; we find good agreement with the simulations. Interestingly, the imbalance between gravity and opposing forces is only ∼20% during core collapse, meaning that this is a quasi-equilibrium rather than a freefall process. For most of their evolution, cores exhibit both subsonic contraction and transonic turbulence inherited from core-building flows; supersonic radial velocities accelerated by gravity only appear near the end of the collapse.

  PublisherDOI

• Dynamically Controlled Transport of GeV Cosmic Rays in Diverse Galactic Environments

  The Astrophysical Journal · 2025-11-13 · 3 citations

  articleOpen access

  Abstract We study transport of GeV cosmic rays (CRs) in a set of high-resolution TIGRESS magnetohydrodynamic simulations of the star-forming interstellar medium (ISM). Our models of local disk patches sample a wide range of gas surface densities, gravitational potentials, and star formation rates (SFRs), and include a spiral arm simulation. Our approach incorporates CR advection by the background gas, streaming along the magnetic field limited by the local ion Alfvén speed, and diffusion relative to the Alfvén wave frame, with the diffusion coefficient set by the balance between streaming-driven Alfvén wave excitation and damping mediated by local gas properties. We find that dynamical transport mechanisms (streaming and advection) are almost solely responsible for GeV CR transport in the extraplanar regions of galaxies, while diffusion along the magnetic field dominates within the primarily neutral ISM of galactic disks. We develop a simple 1D predictive model for the CR pressure P c , dependent only on injected CR flux and gas parameters. We demonstrate that the CR transport efficiency increases with increasing SFR, and provide a fit for the CR feedback yield ϒ c ≡ P c /Σ SFR as a function of Σ SFR , the SFR surface density. We analyze lateral CR transport within the galactic disk, showing that CRs propagate away from feedback regions in spiral arms into interarm regions by a combination of gas advection and field-aligned transport. Lastly, we develop an empirical subgrid model for the CR scattering rate that captures the impacts of the multiphase ISM on CR transport without the numerical burden of full simulations.

  PublisherDOI

• The Coevolution of Stellar Wind-blown Bubbles and Photoionized Gas. I. Physical Principles and a Semianalytic Model

  The Astrophysical Journal · 2025-08-04 · 3 citations

  articleOpen accessCorresponding

  Abstract We propose a new framework for the simultaneous feedback of stellar winds and photoionizing radiation from massive stars, distinguishing the locations where forces are applied, and consequences for internal spatiotemporal evolution of the whole feedback bubble (FB). We quantify the relative dynamical importance of wind-blown bubbles (WBBs) versus the photoionized region (PIR) by the ratio of the radius at which the WBB is in pressure equilibrium with the PIR, R eq , to the Strömgren radius, R St . ζ ≡ R eq / R St quantifies the dynamical dominance of WBBs ( ζ > 1) or the PIR ( ζ < 1). We calculate ζ and find that, for momentum-driven winds, 0.1 ≲ ζ ≲ 1 for the star-forming regions in (i) typical Milky Way–like giant molecular clouds, (ii) the most massive of individual OB stars, and (iii) dense, low-metallicity environments, relevant in the early Universe. In this regime, both WBBs and the PIR are dynamically important to the expansion of the FB. We develop a semianalytic coevolution model (CEM) that takes into account the spatial distribution of forces and the back reactions of both the WBB and PIR. In the ζ < 1 regime where the CEM is most relevant, the model differs in the total FB momentum by up to 25% compared to naive predictions. In the weak-wind limit of ζ ≪ 1, applicable to individual OB stars or low-mass clusters, the CEM has factors ≳2 differences in WBB properties. In a companion paper, we compare these models to 3D, turbulent hydrodynamical simulations.

  PublisherDOI

• The Co-Evolution of Stellar Wind-blown Bubbles and Photoionized Gas II: 3D RMHD Simulations and Tests of Semi-Analytic Models

  ArXiv.org · 2025-05-28

  preprintOpen access

  In a companion paper (Paper I) we presented a Co-Evolution Model (CEM) in which to consider the evolution of feedback bubbles driven by massive stars through both stellar winds and ionizing radiation, outlining when either of these effects is dominant and providing a model for how they evolve together. Here we present results from three-dimensional radiation magneto-hydrodynamical (RMHD) simulations of this scenario for parameters typical of massive star-forming clouds in the Milky Way: precisely the regime where we expect both feedback mechanisms to matter. While we find that the CEM agrees with the simulations to within 25% for key parameters and modestly outperforms previous idealized models, disagreements remain. We show that these deviations originate mainly from the CEM's lack of (i) background inhomogeneity caused by turbulence and (ii) time-variable momentum enhancements in the wind-blown bubble (WBB). Additionally, we find that photoionized gas acts similarly to magnetic fields ([as in Lancaster et al. 2024a) by decreasing the WBB's surface area. This causes a decrease in the amount of cooling at the WBB's interface, resulting in an enhanced WBB dynamical impact.

  PublisherOA PDFDOI

• Dynamically Controlled Transport of GeV Cosmic Rays in Diverse Galactic Environments

  ArXiv.org · 2025-09-03

  preprintOpen access

  We study transport of GeV cosmic rays (CRs) in a set of high-resolution TIGRESS magnetohydrodynamic simulations of the star-forming interstellar medium (ISM). Our local disk patch models sample a wide range of gas surface densities, gravitational potentials, and star formation rates (SFRs), and include a spiral arm simulation. Our approach incorporates CR advection by the background gas, streaming along the magnetic field limited by the local ion Alfvén speed, and diffusion relative to the Alfvén wave frame, with the diffusion coefficient set by the balance between streaming-driven Alfvén wave excitation and damping mediated by local gas properties. We find that dynamical transport mechanisms (streaming and advection) are almost solely responsible for GeV CR transport in the extra-planar regions of galaxies, while diffusion along the magnetic field dominates within the primarily-neutral ISM of galactic disks. We develop a simple 1D predictive model for the CR pressure $P_\mathrm{c}$, dependent only on injected CR flux and gas parameters. We demonstrate that the CR transport efficiency increases with increasing SFR, and provide a fit for the CR feedback yield $Υ_\mathrm{c}~\equiv~P_\mathrm{c}/Σ_\mathrm{SFR}$ as a function of $Σ_\mathrm{SFR}$, the SFR surface density. We analyze lateral CR transport within the galactic disk, showing that CRs propagate away from feedback regions in spiral arms into interarm regions by a combination of gas advection and field-aligned transport. Lastly, we develop an empirical subgrid model for the CR scattering rate that captures the impacts of the multiphase ISM on CR transport without the numerical burden of full simulations.

  PublisherOA PDFDOI

• Energy-Dependent Transport of Cosmic Rays in the Multiphase, Dynamic Interstellar Medium

  ArXiv.org · 2025-06-30

  preprintOpen access

  We investigate the transport of spectrally resolved cosmic ray (CR) protons with kinetic energies between $1-100$ GeV within the dynamic, multiphase interstellar medium (ISM), using a two-moment CR fluid solver applied to a TIGRESS MHD simulation with conditions similar to the solar neighborhood. Our CR transport prescription incorporates space- and momentum-dependent CR scattering coefficients $σ=κ^{-1}$, computed from the local balance between streaming-driven Alfvèn wave growth and damping processes. We find that advection combines with momentum-dependent diffusion to produce a CR distribution function $f(p)\propto~p^{-γ}$ with $γ\approx4.6$ that agrees with observations, steepened from an injected power law slope $γ_\mathrm{inj}=4.3$. The CR pressure is uniform in the highly diffusive, mostly neutral midplane region, but decreases exponentially in the ionized extraplanar region where scattering is efficient. To interpret these numerical results, we develop a two-zone analytic model that captures and links the two (physically and spatially) distinct regimes of CR transport in the multiphase, dynamic ISM. At low momenta, CR transport is dominated by gas advection, while at high momenta, both advection and diffusion contribute. At high momentum, the analytic prediction for the spectral slope approaches $γ=(4/3)γ_\mathrm{inj}-1$, and the predicted scaling of grammage with momentum is $X\propto p^{1-γ_\mathrm{inj}/3}$, consistent with the simulations. These results support a physical picture in which CRs are confined within the neutral midplane by the surrounding ionized gas, with their escape regulated by both the CR scattering rate in the ionized extraplanar gas and the velocity and Alfvén speed of that gas, at effective speed $v_\mathrm{c,eff}\approx(1/2)[κ_\parallel~d(v+v_\mathrm{A,i})/dz]^{1/2}$.

  PublisherOA PDFDOI

• Modeling Cosmic Ray Electron Spectra and Synchrotron Emission in the Multiphase ISM

  ArXiv.org · 2025-06-30

  preprintOpen access

  We model the transport and spectral evolution of 1-100 GeV cosmic ray (CR) electrons (CREs) in TIGRESS MHD simulations of the magnetized, multiphase interstellar medium. We post-process a kpc-sized galactic disk patch representative of the solar neighborhood using a two-moment method for CR transport that includes advection, streaming, and diffusion. The diffusion coefficient is set by balancing wave growth via the CR streaming instability against wave damping (nonlinear Landau and ion-neutral collisions), depending on local gas and CR properties. Implemented energy loss mechanisms include synchrotron, inverse Compton, ionization, and bremsstrahlung. We evaluate CRE losses by different mechanisms as a function of energy and distance from the midplane, and compare loss timescales to transport and diffusion timescales. This comparison shows that CRE spectral steepening above p = 1 GeV/c is due to a combination of energy-dependent transport and losses. Our evolved CRE spectra are consistent with direct observations in the solar neighborhood, with a spectral index that steepens from an injected value of -2.3 to an energy dependent value between -2.7 and -3.3. We also show that the steepening is independent of the injection spectrum. Finally, we present potential applications of our models, including to the production of synthetic synchrotron emission. Our simulations demonstrate that the CRE spectral slope can be accurately recovered from pairs of radio observations in the range 1.5-45 GHz.

  PublisherOA PDFDOI

• Applying a star formation model calibrated on high-resolution interstellar medium simulations to cosmological simulations of galaxy formation

  ArXiv.org · 2025-02-18 · 3 citations

  preprintOpen access

  Modern high-resolution simulations of the interstellar medium (ISM) have shown that key factors in governing star formation are the competing influences of radiative dissipation, pressure support driven by stellar feedback, and the relentless pull of gravity. Cosmological simulations of galaxy formation, such as IllustrisTNG or ASTRID, are however not able to resolve this physics in detail and therefore need to rely on approximate treatments. These have often taken the form of empirical subgrid models of the ISM expressed in terms of an effective equation of state (EOS) that relates the mean ISM pressure to the mean gas density. Here we seek to improve these heuristic models by directly fitting their key ingredients to results of the high-resolution TIGRESS simulations, which have shown that the dynamical equilibrium of the ISM can be understood in terms of a pressure-regulated, feedback modulated (PRFM) model for star formation. Here we explore a simple subgrid model that draws on the PRFM concept but uses only local quantities. It accurately reproduces PRFM for pure gas disks, while it predicts slightly less star formation than PRFM in the presence of an additional thin stellar disk. We compare the properties of this model with the older Springel and Hernquist and TNG prescriptions, and apply all three to isolated simulations of disk galaxies as well as to a set of high-resolution zoom-in simulations carried out with a novel 'multi-zoom' technique that we introduce in this study. The softer EOS implied by TIGRESS produces substantially thinner disk galaxies, which has important ramifications for disk stability and galaxy morphology. The total stellar mass of galaxies is however hardly modified at low redshift, reflecting the dominating influence of large-scale gaseous inflows and outflows to galaxies, which are not sensitive to the EOS itself

  PublisherOA PDFDOI

Recent grants

• The Physics of Feedback and Star Formation Regulation in Galactic Disks

  NSF · $416k · 2013–2017

• From Galactic Centers to Galactic Fringes: Control of Star Formation in the Dynamic Interstellar Medium

  NSF · $369k · 2009–2013

• From Galactic Centers to Galactic Fringes: Control of Star Formation in the Dynamic Interstellar Medium

  NSF · $158k · 2012–2014

• On the Formation and Destruction of Giant Molecular Clouds in Galaxies

  NSF · $385k · 2017–2021

• Structure and Dynamics of Neutral Gas in Spiral Galaxies: Numerical Models

  NSF · $243k · 2005–2010

Frequent coauthors

• Chang‐Goo Kim

  Princeton University

  89 shared

• Greg L. Bryan

  51 shared

• Jeong‐Gyu Kim

  National Astronomical Observatory of Japan

  49 shared

• Woong‐Tae Kim

  47 shared

• Erik Rosolowsky

  University of Alberta

  47 shared

• Alberto D. Bolatto

  42 shared

• Adam K. Leroy

  41 shared

• Éric Emsellem

  38 shared

Labs

• Department of Astrophysical SciencesPI

Education

• PhD, Physics

  University of California Berkeley

  1993

• A.B., Physics

  Harvard University

  1987