BN Objects — A Class of Very Young and Massive Stars

Henning, Th.; Gürtler, J.

doi:10.1007/978-94-009-3785-7_19

Cited by 2 publications

(2 citation statements)

References 32 publications

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“…If we try to understand the starburst in NGC 1377 as a scaled-up version of stellarsize objects (as a mental picture only), the class of Becklin-Neugebauer (BN) objects may represent the closest analogs suited to that purpose. BN objects are at the transition between massive protostars and pre-main-sequence stars exciting ultracompact HII regions, after the intense accretion phase has stopped, but before the radiation pressure has balanced the interstellar medium pressure (Henning & Gürtler 1986). The emergent infrared radiation is strongly self-absorbed like in NGC 1377, and molecular hydrogen is excited by shocks, caused by the interaction of stellar outflows with the molecular envelope.…”

Section: Summary and Discussionmentioning

confidence: 99%

The Opaque Nascent Starburst in NGC 1377:SpitzerSINGS Observations

Roussel

Hélou

Smith

et al. 2006

ApJ

122

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We analyze extensive data on NGC 1377 from the Spitzer Infrared Nearby Galaxies Survey (SINGS). Within the category of nascent starbursts, that we previously selected as having infrared to radio continuum ratios in large excess of the average, and containing hot dust, NGC 1377 has the largest infrared excess yet measured. Optical imaging reveals a morphological distortion suggestive of a recent accretion event. Infrared spectroscopy reveals a compact and opaque source dominated by a hot, self-absorbed continuum (τ ∼ 20 in the 10 µm silicate band). We provide physical evidence against non-stellar activity being the heating source. HII regions are detected through the single [NeII] line, probing

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Section: Summary and Discussionmentioning

confidence: 99%

The Opaque Nascent Starburst in NGC 1377:SpitzerSINGS Observations

Roussel

Hélou

Smith

et al. 2006

ApJ

122

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“…See van den Hoek & de Jong (1996) for such a discussion. These attempts range from stellar orbit diffusion coupled with a Galactic radial abundance gradient (see e.g., François & Matteucci 1993;Wielen, Fuchs, & Dettbarn 1996) to processes that would lead to abundance inhomogeneities from a homogeneous starting point such as chemical fractionation in grain formation (see e.g., Henning & Gürtler 1986). The models of van den Hoek & de Jong (1996) consider sequential enrichment by successive generations of stars within individual gas clouds.…”

Section: Introductionmentioning

confidence: 99%

A Stochastic Approach to Chemical Evolution

Copi¹

1997

ApJ

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Observations of elemental abundances in the Galaxy have repeatedly shown an intrinsic scatter as a function of time and metallicity. The standard approach to chemical evolution does not attempt to address this scatter in abundances since only the mean evolution is followed. In this work, the scatter is addressed via a stochastic approach to solving chemical evolution models. Three simple chemical evolution scenarios are studied using this stochastic approach : a closed box model, an infall model, and an outÑow model. These models are solved for the solar neighborhood in a Monte Carlo fashion. The evolutionary history of one particular region is determined randomly based on the star formation rate and the initial mass function. Following the evolution in an ensemble of such regions leads to the predicted spread in abundances expected, based solely on di †erent evolutionary histories of otherwise identical regions. In this work, 13 isotopes are followed, including the light elements, the CNO elements, a few a-elements, and iron. It is found that the predicted spread in abundances for a 105 region is in good M _ agreement with observations for the a-elements. For CN, the agreement is not as good, perhaps indicating the need for more physics input for low-mass stellar evolution. Similarly for the light elements, the predicted scatter is quite small, which is in contradiction to the observations of 3He in H II regions. The models are tuned for the solar neighborhood so that good agreement with H II regions is not expected. This has important implications for low-mass stellar evolution and on using chemical evolution to determine the primordial light-element abundances in order to test big bang nucleosynthesis.

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BN Objects — A Class of Very Young and Massive Stars

Cited by 2 publications

References 32 publications

The Opaque Nascent Starburst in NGC 1377:SpitzerSINGS Observations

The Opaque Nascent Starburst in NGC 1377:SpitzerSINGS Observations

A Stochastic Approach to Chemical Evolution

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