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In this paper we investigate the level of star formation activity within nearby molecular clouds. We employ a uniform set of infrared extinction maps to provide accurate assessments of cloud mass and structure and compare these with…

Astrophysics of Galaxies · Physics 2015-05-19 Charles J. Lada , Marco Lombardi , João F. Alves

We leverage the 1 pc spatial resolution of the Leike et al. 2020 3D dust map to characterize the three-dimensional structure of nearby molecular clouds ($d \lesssim 400$ pc). We start by "skeletonizing" the clouds in 3D volume density space…

We investigate how the dynamical state of molecular clouds relates to host galaxy environment, and how this impacts the star formation efficiency in the Milky Way and seven nearby galaxies. We compile measurements of molecular cloud and…

Astrophysics of Galaxies · Physics 2019-09-25 Andreas Schruba , J. M. Diederik Kruijssen , Adam K. Leroy

We explore the relation between the stellar mass surface density and the mass surface density of molecular hydrogen gas in twelve nearby molecular clouds that are located at $<$1.5 kpc distance. The sample clouds span an order of magnitude…

We present a numerical study of the evolution of molecular clouds, from their formation by converging flows in the warm ISM, to their destruction by the ionizing feedback of the massive stars they form. We improve with respect to our…

Astrophysics of Galaxies · Physics 2015-06-15 Pedro Colin , Enrique Vazquez-Semadeni , Gilberto C. Gomez

Recent observational results indicate that the functional shape of the spatially-resolved star formation-molecular gas density relation depends on the spatial scale considered. These results may indicate a fundamental role of sampling…

Astrophysics of Galaxies · Physics 2015-06-04 Daniela Calzetti , Guilin Liu , Jin Koda

We examine the physical parameters that affect the accumulation of gas in molecular clouds to high column densities where the formation of stars takes place. In particular, we analyze the dense gas mass fraction (DGMF) in a set of…

Astrophysics of Galaxies · Physics 2015-06-15 Jouni Kainulainen , Christoph Federrath , Thomas Henning

One of the most important and well-established empirical results in astronomy is the Kennicutt-Schmidt (KS) relation between the density of interstellar gas and the rate at which that gas forms stars. A tight correlation between these…

We apply gravity-based and density-based methods to identify clouds in numerical simulations of the star-forming, three-phase interstellar medium (ISM), and compare their properties and their global correlation with the star formation rate…

Astrophysics of Galaxies · Physics 2020-07-29 S. Alwin Mao , Eve C. Ostriker , Chang-Goo Kim

We investigate the origin of observed local star formation relations using radiative magnetohydrodynamic simulations with self-consistent star formation and ionising radiation. We compare these clouds to the density distributions of local…

Astrophysics of Galaxies · Physics 2017-09-06 Sam Geen , Juan D Soler , Patrick Hennebelle

We describe an overall picture of galactic-scale star formation. Recent high-resolution magneto-hydrodynamical simulations of two-fluid dynamics with cooling/heating and thermal conduction have shown that the formation of molecular clouds…

Astrophysics of Galaxies · Physics 2015-07-29 Shu-ichiro Inutsuka , Tsuyoshi Inoue , Kazunari Iwasaki , Takashi Hosokawa

We study the formation of giant dense cloud complexes and of stars within them by means of SPH numerical simulations of the mildly supersonic collision of gas streams (``inflows'') in the warm neutral medium (WNM). The resulting…

New extragalactic measurements of the cloud population-averaged star formation (SF) efficiency per freefall time $\rm\epsilon_{\rm ff}$ from PHANGS show little sign of theoretically predicted dependencies on cloud-scale virial level or…

[abridged] 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, recent…

Cosmology and Nongalactic Astrophysics · Physics 2015-05-30 Mark R. Krumholz , Avishai Dekel , Christopher F. McKee

Using observed GALEX far-ultraviolet (FUV) fluxes and VLA images of the 21-cm HI column densities, along with estimates of the local dust abundances, we measure the volume densities of a sample of actively star-forming giant molecular…

Astrophysics · Physics 2009-11-13 Jonathan S. Heiner , Ronald J. Allen , O. Ivy Wong , Pieter C. van der Kruit

We present a new observational method to evaluate the star formation law as formulated by Schmidt: the power-law expression assumed to relate the rate of star formation in a volume of space to the local total gas volume density. Volume…

Astrophysics of Galaxies · Physics 2015-05-19 J. S. Heiner , R. J. Allen , P. C. van der Kruit

We present a new model to describe the star formation process in galaxies, which includes the description of the different gas phases -- molecular, atomic, and ionized -- together with its metal content. The model, which will be coupled to…

Astrophysics of Galaxies · Physics 2025-08-14 Ezequiel Lozano , Cecilia Scannapieco , Sebastian E. Nuza

Stars in galaxies form in giant molecular clouds that coalesce when the atomic hydrogen is converted into molecules. There are currently two dominant models for what property of the galactic disk determines its molecular fraction: either…

Cosmology and Nongalactic Astrophysics · Physics 2015-05-19 Michele Fumagalli , Mark R. Krumholz , Leslie K. Hunt

We test some ideas for star formation relations against data on local molecular clouds. On a cloud by cloud basis, the relation between the surface density of star formation rate and surface density of gas divided by a free-fall time,…

Astrophysics of Galaxies · Physics 2015-06-18 Neal J. Evans , Amanda Heiderman , Nalin Vutisalchavakul

We review recent advances in the analytical and numerical modeling of the star formation rate in molecular clouds and discuss the available observational constraints. We focus on molecular clouds as the fundamental star formation sites,…