Topic
Star formation
About: Star formation is a research topic. Over the lifetime, 37405 publications have been published within this topic receiving 1808161 citations. The topic is also known as: astrogenesis.
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01 Jan 1991
TL;DR: In this paper, the basic physics of the early stages of star formation are discussed. But the authors focus on the formation of the stars and do not consider the evolution of the star formation process.
Abstract: I: Physics of Giant Molecular Clouds: Origin, Structure, and Evolution. Star Forming Giant Molecular Clouds L. Blitz. The Origin and Evolution of Giant Molecular Clouds B.G. Elmegreen. Cosmic Magnetism and the Basic Physics of the Early Stages of Star Formation T.Ch. Mouschovias. II: The Physics of Star Formation. OB Associations and the Fossil Record of Star Formation A. Blaauw. Physical Conditions and Heating/Cooling Processes in High Mass Star Formation Regions R. Genzel. Newly Formed Massive Stars E. Churchwell. Masers and Star Formation N.D. Kylafis. The Physical Conditions of Low Mass Star Forming Regions J. Cernicharo. The Formation of Low Mass Stars: Observations C.J. Lada. The Formation of Low Mass Stars: Theory F.H. Shu. Numerical Studies of Cloud Collapse W.M. Tscharnutter. Binary Star Formation J.E. Pringle. Single-Stage Fragmentation and a Modern Theory of Star Formation T.Ch. Mouschovias. III: Physics of Early Stellar Evolution and Stellar Winds. Molecular Outflows: Observed Properties J. Bally, A.P. Lane. Herbig-Haro Objects B. Reipurth. The Physics of Disk Winds R.E. Pudritz, G. Gomez de Castro, A.I. Gomez de Castro. Ionized Winds from Young Stellar Objects N. Panagia. The Physics of Neutral Winds from Low Mass Young Stellar Objects A. Natta, C. Giovanardi. Eposodic Phenomena in Early Stellar Evolution L. Hartmann. Properties and Models of T Tauri Stars C. Bertout, G. Basri. The X-Ray and Radio Properties of Low-Mass Pre-Main Sequence Stars T. Montmerle. Polarization of Light and Models of the Circumstellar Environment of Young Stellar Objects P. Bastien. Index.
521 citations
TL;DR: In this article, the authors show that the observed data are consistent with a simple, local, volumetric star formation law in which the star formation rate is simply 1% of the molecular gas mass per local free-fall time.
Abstract: Star formation laws are rules that relate the rate of star formation in a particular region, either an entire galaxy or some portion of it, to the properties of the gas, or other galactic properties, in that region. While observations of Local Group galaxies show a very simple, local star formation law in which the star formation rate per unit area in each patch of a galaxy scales linearly with the molecular gas surface density in that patch, recent observations of both Milky Way molecular clouds and high-redshift galaxies apparently show a more complicated relationship in which regions of equal molecular gas surface density can form stars at quite different rates. These data have been interpreted as implying either that different star formation laws may apply in different circumstances, that the star formation law is sensitive to large-scale galaxy properties rather than local properties, or that there are high-density thresholds for star formation. Here we collate observations of the relationship between gas and star formation rate from resolved observations of Milky Way molecular clouds, from kpc-scale observations of Local Group galaxies, and from unresolved observations of both disk and starburst galaxies in the local universe and at high redshift. We show that all of these data are in fact consistent with a simple, local, volumetric star formation law. The apparent variations stem from the fact that the observed objects have a wide variety of three-dimensional size scales and degrees of internal clumping, so even at fixed gas column density the regions being observed can have wildly varying volume densities. We provide a simple theoretical framework to remove this projection effect, and we use it to show that all the data, from small solar neighborhood clouds with masses ~103 M ? to submillimeter galaxies with masses ~1011 M ?, fall on a single star formation law in which the star formation rate is simply ~1% of the molecular gas mass per local free-fall time. In contrast, proposed star formation laws in which the star formation timescale is set by the galactic rotation period are inconsistent with the data from the Milky Way and the Local Group, while those in which the star formation rate is linearly proportional to the gas mass above some density threshold fail both in the Local Group and for starburst galaxies.
518 citations
TL;DR: Simba as discussed by the authors is the next generation of the Mufasa cosmological galaxy formation simulations run with Gizmo's meshless finite mass hydrodynamics, which includes updates to Mufaa's sub-resolution star formation and feedback prescriptions, and introduces black hole growth via the torque-limited accretion model of Angles-Alcazar et al.
Abstract: We introduce the Simba simulations, the next generation of the Mufasa cosmological galaxy formation simulations run with Gizmo's meshless finite mass hydrodynamics. Simba includes updates to Mufasa's sub-resolution star formation and feedback prescriptions, and introduces black hole growth via the torque-limited accretion model of Angles-Alcazar et al. (2017) from cold gas and Bondi accretion from hot gas, along with black hole feedback via kinetic bipolar outflows and X-ray energy. Ejection velocities are taken to be ~10^3 km/s at high Eddington ratios, increasing to ~8000 km/s at Eddington ratios below 2%, with a constant momentum input of 20L/c. Simba further includes an on-the-fly dust production, growth, and destruction model. Our Simba run with (100 Mpc/h)^3 and 1024^3 gas elements reproduces numerous observables, including galaxy stellar mass functions at z=0-6, the stellar mass--star formation rate main sequence, HI and H2 fractions, the mass-metallicity relation at z=0 and z=2, star-forming galaxy sizes, hot gas fractions in massive halos, and z=0 galaxy dust properties. However, Simba also yields an insufficiently sharp truncation of the z=0 mass function, and too-large sizes for low-mass quenched galaxies. We show that Simba's jet feedback is primarily responsible for quenching massive galaxies.
518 citations
TL;DR: In this article, a subarcsecond survey of the λ = 2.7 mm dust continuum emission from young, embedded stellar systems is presented, which is the first consistent comparison of dust emission structures in a variety of systems.
Abstract: We present the results of a λ = 2.7 mm continuum interferometric survey of 24 young stellar objects in 11 fields. The target objects range from deeply embedded class 0 sources to optical T Tauri sources. This is the first subarcsecond survey of the λ = 2.7 mm dust continuum emission from young, embedded stellar systems. These multiarray observations, utilizing the high dynamic u-v range of the BIMA array, fully sample spatial scales ranging from 04 to 60'', thus allowing the first consistent comparison of dust emission structures in a variety of systems. The images show a diversity of structure and complexity. The optically visible T Tauri stars (DG Tauri, HL Tauri, GG Tauri, and GM Aurigae) have continuum emission dominated by compact (≤1'') circumstellar disks. In the cases of HL Tauri and DG Tauri, the disks are resolved. The more embedded near-infrared sources (SVS 13 and L1551 IRS 5) have continuum emission that is extended and compact. The embedded sources (L1448 IRS 3, NGC 1333 IRAS 2, NGC 1333 IRAS 4, VLA 1623, and IRAS 16293-2422) have continuum emission dominated by the extended envelope, typically ≥85% of the emission at λ = 2.7 mm. In many of the deeply embedded systems, it is difficult to uniquely isolate the disk emission component from the envelope extending inward to AU-sized scales. Simple estimates of the circumstellar mass in the optical/infrared and embedded systems are in the ranges 0.01-0.08 M☉ and 0.04-2.88 M☉, respectively. All of the target embedded objects are in multiple systems with separations on scales of ~30'' or less. Based on the system separation, we place the objects in three categories: separate envelope (separation ≥6500 AU), common envelope (separation 150-3000 AU), and common disk (separation ≤100 AU). These three groups can be linked with fragmentation events during the star formation process: separate envelopes from prompt initial fragmentation and the separate collapse of a loosely condensed cloud, common envelopes from fragmentation of a moderately centrally condensed spherical system, and common disk from fragmentation of a high angular momentum circumstellar disk.
517 citations
TL;DR: In this article, the authors carried out an H α + [N II] imaging survey for an essentially volume-limited sample of galaxies within 11 Mpc of the Milky Way, and the main product of the survey is a catalog of integrated Hα fluxes, luminosities, and equivalent widths for the galaxies in the sample.
Abstract: As part of a broader effort to characterize the population of star-forming galaxies in the local universe, we have carried out an H α + [N II] imaging survey for an essentially volume-limited sample of galaxies within 11 Mpc of the Milky Way. This first paper describes the design of the survey, the observation, data processing, and calibration procedures, and the characteristics of the galaxy sample. The main product of the paper is a catalog of integrated Hα fluxes, luminosities, and equivalent widths for the galaxies in the sample. We briefly discuss the completeness properties of the survey and compare the distribution of the sample and its star formation properties to other large Hα imaging surveys. These data form the foundation for a series of follow-up studies of the star formation properties of the local volume, and the properties and duty cycles of star formation bursts in dwarf galaxies.
516 citations