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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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Journal ArticleDOI
TL;DR: In this article, a comparison of plane-parallel non-LTE model atmospheres and comoving frame calculations is presented for massive Population III stars and stellar populations based on a recent stellar evolution tracks and up-to-date evolutionary synthesis models, with the aim to study their spectral properties, including their dependence on age, star formation history, and IMF.
Abstract: We present realistic models for massive Population III stars and stellar populations based on non-LTE model atmospheres, recent stellar evolution tracks and up-to-date evolutionary synthesis models, with the aim to study their spectral properties, including their dependence on age, star formation history, and IMF. A comparison of plane parallel non-LTE model atmospheres and comoving frame calculations shows that even in the presence of some putative weak mass loss, the ionising spectra of metal-free populations differ little or negligibly from those obtained using plane parallel non-LTE models. As already discussed by Tumlinson & Shull ([CITE]), the main salient property of Pop III stars is their increased ionising flux, especially in the He+ continuum (>54 eV). The main result obtained for individual Pop III stars is the following: due to their redward evolution off the zero age main sequence (ZAMS) the spectral hardness measured by the He/H ionising flux is decreased by a factor ~2 when averaged over their lifetime. If such stars would suffer strong mass loss, their spectral appearance could, however, remain similar to that of their ZAMS position. The main results regarding integrated stellar populations are: – for young bursts and the case of a constant SFR, nebular continuous emission – neglected in previous studies – dominates the spectrum redward of Lyman-α if the escape fraction of ionising photons out of the considered region is small or negligible. In consequence predicted emission line equivalent widths are considerably smaller than found in earlier studies, whereas the detection of the continuum is eased. Nebular line and continuous emission strongly affect the broad band photometric properties of Pop III objects; – due to the redward stellar evolution and short lifetimes of the most massive stars, the hardness of the ionising spectrum decreases rapidly, leading to the disappearance of the characteristic He ii recombination lines after ~3 Myr in instantaneous bursts; – He ii λ 1640, Hα (and other) line luminosities usable as indicators of the star formation rate are given for the case of a constant SFR. For obvious reasons such indicators depend strongly on the IMF; – due to an increased photon production and reduced metal yields, the relative efficiency of ionising photon energy to heavy element rest mass production, η , of metal-poor and metal-free populations is increased by factors of ~4 to 18 with respect to solar metallicity and for “standard” IMFs; – the lowest values of 1.6–2.2% are obtained for IMFs exclusively populated with high mass stars (). If correct, the yields dominated by pair creation SNae then predict large overabundances of O/C and Si/C compared to solar abundance ratios. Detailed results are given in tabular form and as fit formulae for easy implementation in other calculations. The predicted spectra will be used to study the detectability of Pop III galaxies and to derive optimal search strategies for such objects.

854 citations

Journal ArticleDOI
Seb Oliver1, James J. Bock2, James J. Bock3, Bruno Altieri4, Alexandre Amblard5, V. Arumugam6, Herve Aussel7, Tom Babbedge8, Alexandre Beelen9, Matthieu Béthermin7, Matthieu Béthermin9, Andrew Blain2, Alessandro Boselli10, C. Bridge2, Drew Brisbin11, V. Buat10, Denis Burgarella10, N. Castro-Rodríguez12, N. Castro-Rodríguez13, Antonio Cava14, P. Chanial7, Michele Cirasuolo15, David L. Clements8, A. Conley16, L. Conversi4, Asantha Cooray17, Asantha Cooray2, C. D. Dowell3, C. D. Dowell2, Elizabeth Dubois1, Eli Dwek18, Simon Dye19, Stephen Anthony Eales20, David Elbaz7, Duncan Farrah1, A. Feltre21, P. Ferrero12, P. Ferrero13, N. Fiolet22, N. Fiolet9, M. Fox8, Alberto Franceschini21, Walter Kieran Gear20, E. Giovannoli10, Jason Glenn16, Yan Gong17, E. A. González Solares23, Matthew Joseph Griffin20, Mark Halpern24, Martin Harwit, Evanthia Hatziminaoglou, Sebastien Heinis10, Peter Hurley1, Ho Seong Hwang7, A. Hyde8, Edo Ibar15, O. Ilbert10, K. G. Isaak25, Rob Ivison6, Rob Ivison15, Guilaine Lagache9, E. Le Floc'h7, L. R. Levenson3, L. R. Levenson2, B. Lo Faro21, Nanyao Y. Lu2, S. C. Madden7, Bruno Maffei26, Georgios E. Magdis7, G. Mainetti21, Lucia Marchetti21, G. Marsden24, J. Marshall2, J. Marshall3, A. M. J. Mortier8, Hien Nguyen3, Hien Nguyen2, B. O'Halloran8, Alain Omont22, Mat Page27, P. Panuzzo7, Andreas Papageorgiou20, H. Patel8, Chris Pearson28, Chris Pearson29, Ismael Perez-Fournon12, Ismael Perez-Fournon13, Michael Pohlen20, Jonathan Rawlings27, Gwenifer Raymond20, Dimitra Rigopoulou30, Dimitra Rigopoulou28, L. Riguccini7, D. Rizzo8, Giulia Rodighiero21, Isaac Roseboom6, Isaac Roseboom1, Michael Rowan-Robinson8, M. Sanchez Portal4, Benjamin L. Schulz2, Douglas Scott24, Nick Seymour31, Nick Seymour27, D. L. Shupe2, A. J. Smith1, Jamie Stevens32, M. Symeonidis27, Markos Trichas33, K. E. Tugwell27, Mattia Vaccari21, Ivan Valtchanov4, Joaquin Vieira2, Marco P. Viero2, L. Vigroux22, Lifan Wang1, Robyn L. Ward1, Julie Wardlow17, G. Wright15, C. K. Xu2, Michael Zemcov2, Michael Zemcov3 
TL;DR: The Herschel Multi-tiered Extragalactic Survey (HerMES) is a legacy program designed to map a set of nested fields totalling ∼380deg^2 as mentioned in this paper.
Abstract: The Herschel Multi-tiered Extragalactic Survey (HerMES) is a legacy programme designed to map a set of nested fields totalling ∼380 deg^2. Fields range in size from 0.01 to ∼20 deg^2, using the Herschel-Spectral and Photometric Imaging Receiver (SPIRE) (at 250, 350 and 500 μm) and the Herschel-Photodetector Array Camera and Spectrometer (PACS) (at 100 and 160 μm), with an additional wider component of 270 deg^2 with SPIRE alone. These bands cover the peak of the redshifted thermal spectral energy distribution from interstellar dust and thus capture the reprocessed optical and ultraviolet radiation from star formation that has been absorbed by dust, and are critical for forming a complete multiwavelength understanding of galaxy formation and evolution. The survey will detect of the order of 100 000 galaxies at 5σ in some of the best-studied fields in the sky. Additionally, HerMES is closely coordinated with the PACS Evolutionary Probe survey. Making maximum use of the full spectrum of ancillary data, from radio to X-ray wavelengths, it is designed to facilitate redshift determination, rapidly identify unusual objects and understand the relationships between thermal emission from dust and other processes. Scientific questions HerMES will be used to answer include the total infrared emission of galaxies, the evolution of the luminosity function, the clustering properties of dusty galaxies and the properties of populations of galaxies which lie below the confusion limit through lensing and statistical techniques. This paper defines the survey observations and data products, outlines the primary scientific goals of the HerMES team, and reviews some of the early results.

852 citations

Journal ArticleDOI
TL;DR: In this paper, the authors discuss the initial conditions for Population III star formation, as given by variants of the cold dark matter cosmology, and show how complementary observations, both at high redshifts and in our local cosmic neighborhood, can be utilized to probe the first epoch of star formation.
Abstract: We review recent theoretical results on the formation of the first stars in the universe, and emphasize related open questions. In particular, we discuss the initial conditions for Population III star formation, as given by variants of the cold dark matter cosmology. Numerical simulations have investigated the collapse and the fragmentation of metal-free gas, showing that the first stars were predominantly very massive. The exact determination of the stellar masses, and the precise form of the primordial initial mass function, is still hampered by our limited understanding of the accretion physics and the protostellar feedback effects. We address the importance of heavy elements in bringing about the transition from an early star formation mode dominated by massive stars, to the familiar mode dominated by low mass stars, at later times. We show how complementary observations, both at high redshifts and in our local cosmic neighborhood, can be utilized to probe the first epoch of star formation.

849 citations

Journal ArticleDOI
TL;DR: In this paper, the authors analyzed a sample of ~2600 MIPS/Spitzer 24mic sources brighter than 80muJy and located in the Chandra Deep Field South to characterize the evolution of the comoving infrared (IR) energy density of the Universe up to z~1.7.
Abstract: We analyze a sample of ~2600 MIPS/Spitzer 24mic sources brighter than ~80muJy and located in the Chandra Deep Field South to characterize the evolution of the comoving infrared (IR) energy density of the Universe up to z~1. Using published ancillary optical data we first obtain a nearly complete redshift determination for the 24mic objects associated with R 10^11 L_IR) are responsible for 70+/-15% of this energy density at z~1. Taking into account the contribution of the UV luminosity evolving as (1+z)^~2.5, we infer that these IR-luminous sources dominate the star-forming activity beyond z~0.7. The uncertainties affecting these conclusions are largely dominated by the errors in the k-corrections used to convert 24mic fluxes into luminosities.

844 citations

Journal ArticleDOI
TL;DR: In this article, a new chemical evolution model for the Galaxy that assumes two main infall episodes, for the formation of the halo-thick disk and thin disk, respectively, is presented.
Abstract: We present a new chemical evolution model for the Galaxy that assumes two main infall episodes, for the formation of the halo-thick disk and thin disk, respectively. We do not try to take into account explicitly the evolution of the halo since our model is better suited for computing the evolution of the disk (thick plus thin), but we implicitly assume that the timescale for the formation of the halo was of the same order as the timescale for the formation of the thick disk. The formation of the thin disk is much longer than that of the thick disk, implying that the infalling gas forming the thin disk comes not only from the thick disk but mainly from the intergalactic medium. The timescale for the formation of the thin disk is assumed to be a function of Galactocentric distance, leading to an inside-out picture for the Galaxy's building. The model takes into account the most up-to-date nucleosynthesis prescriptions and adopts a threshold in the star formation process, which naturally produces a hiatus in the star formation rate at the end of the thick-disk phase, as suggested by recent observations. The model results are compared with an extended set of observational constraints both for the solar neighborhood and for the whole disk. Among these constraints, the tightest is the metallicity distribution of the G-dwarf stars, for which new data are now available. Our model fits these new data very well. The model also predicts the evolution of the gas mass, the star formation rate, the supernova rates, and the abundances of 16 chemical elements as functions of time and Galactocentric distance. We show that, in order to reproduce most of these constraints, a timescale of ≤1 Gyr for the (halo) thick disk and of 8 Gyr for the thin disk's formation in the solar vicinity are required. We predict that the radial abundance gradients in the inner regions of the disk (R < 1 R☉) are steeper than in the outer regions, a result confirmed by recent abundance determinations, and that the inner gradients steepen during the Galactic lifetime. The importance and the advantages of assuming a threshold gas density for the onset of the star formation process are discussed.

843 citations


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Performance
Metrics
No. of papers in the topic in previous years
YearPapers
2023742
20221,675
20211,238
20201,489
20191,497
20181,530