Interstellar Dust And Extinction

Mathis, J. S.

doi:10.1146/annurev.astro.28.1.37

Cited by 763 publications

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“…We used the reddening relations E(V − I c ) = 1.25E(B − V) from Dean et al (1978) and Mathis (1990). Catanzaro et al (2004) were the first to derive parameters for HR 6000 from high resolution spectra, in particular from H γ and H δ Balmer profiles observed on FEROS spectra.…”

Section: Stellar Parametersmentioning

confidence: 99%

A refined analysis of the remarkable Bp star HR 6000

Castelli

Hubrig

2007

A&A

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Aims. UVES spectra of the very young ( ∼ 10 7 years) peculiar B-type star HR 6000 were analyzed in the near-UV and visual spectral regions (3050-9460 Å) with the aim to extend to other spectral ranges the study made previously in the UV using IUE spectra. Methods. Stellar parameters T eff =12850 K, log g=4.10, and ξ=0 km s −1 , as determined from H β , H γ , H δ Balmer profiles and from the Fe i, Fe ii ionization equilibrium, were used to compute an individual abundances ATLAS12 model. We identified spectral peculiarities and obtained final stellar abundances by comparing observed and computed equivalent widths and line profiles.Results. The adopted model fails to reproduce the (b-y) and c color indices. The spectral analysis has revealed: the presence of emission lines for Mn ii, Cr ii, and Fe ii; isotopic anomalies for Hg , Ca ; the presence of interstellar lines of Na i at λλ 3302.3, 3302.9, 5890, 5896 Å, and of K i at 7665, 7699 Å; the presence of a huge quantity of unidentified lines, which we presume to be mostly due to Fe ii transitions owing to the large Fe overabundance amounting to [+0.7]. The main chemical peculiarities are an extreme overabundance of Xe, followed by those of Hg, P, Y, Mn, Fe, Be, and Ti. The most underabundant element is Si, followed by C, N, Al, S, Mg, V, Sr, Co, Cl, Sc, and Ni. The silicon underabundance [−2.9] is the lowest value for Si ever observed in any HgMn star. The observed lines of He i can not be reproduced by a single value of the He abundance, but they require values ranging from [−0.8] to [−1.6]. Furthermore, when the observed and computed wings of He i lines are fitted, the observed line cores are much weaker than the computed ones. From the present analysis we infer the presence of vertical abundance stratification for He, Mn, and possibly also P.

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Section: Stellar Parametersmentioning

confidence: 99%

A refined analysis of the remarkable Bp star HR 6000

Castelli

Hubrig

2007

A&A

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“…the extinction law), which are well known and calibrated in the near-infrared (e.g. Mathis 1990). In particular, we have chosen to simulate the dust column density conditions in the Pipe Nebula, a nearby cloud with a well-populated and smooth distribution of background stars.…”

Section: Introductionmentioning

confidence: 99%

The fidelity of the core mass functions derived from dust column density data

Kainulainen

Lada

Rathborne

2009

A&A

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Aims. We examine the recoverability and completeness limits of the dense core mass functions (CMFs) derived for a molecular cloud using extinction data and a core identification scheme based on two-dimensional thresholding. We study how the selection of core extraction parameters affects the accuracy and completeness limit of the derived CMF and the core masses, and also how accurately the CMF can be derived in varying core crowding conditions. Methods. We performed simulations where a population of artificial cores was embedded in the variable background extinction field of the Pipe nebula. We extracted the cores from the simulated extinction maps, constructed the CMFs, and compared them to the input CMFs. The simulations were repeated using a variety of extraction parameters and several core populations with differing input mass functions and differing degrees of crowding.Results. The fidelity of the observed CMF depends on the parameters selected for the core extraction algorithm for our background. More importantly, it depends on how crowded the core population is. We find that the observed CMF recovers the true CMF reliably when the mean separation of cores is larger than the mean diameter of the cores ( f > 1). If this condition holds, the derived CMF for the Pipe nebula background is accurate and complete above M > ∼ 0.8 . . . 1.5 M , depending on the parameters used for the core extraction. In the simulations, the best fidelity was achieved with the detection threshold of 1 or 2 times the rms-noise of the extinction data, and with the contour level spacings of 3 times the rms-noise. Choosing a higher threshold and wider level spacings increases the limiting mass. The simulations also show that, when f > ∼ 1.5, the masses of individual cores are recovered with a typical uncertainty of 25 . . . 30%. When f ≈ 1, the uncertainty is ∼60%. In very crowded cases where f < 1 the core identification algorithm is unable to recover the masses of the cores adequately, and the derived CMF is unlikely to represent the underlying CMF. For the cores of the Pipe nebula f ≈ 2.0 thereby justifying the use of the method in that region.

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“…The main sequence is also shown in Figure 2 for O3 to B9 stars (Vacca et al 1996, O3-B0 ; Schmidt-Kaler 1982, B1-B9) assuming a distance of 7 kpc ( §1). Mathis (1990). Each of the two lines begins at the colors for an unreddened star (M3 III, Frogel et al 1978;O6, Koornneef 1983).…”

Section: Imagesmentioning

confidence: 99%

“…A K and dereddened magnitudes can be derived for the spectroscopic targets using an adopted extinction law (Mathis 1990), the observed colors and the intrinsic colors. The latter can be estimated from the spectroscopic classifications derived in the last sections.…”

Section: Extinction To Individual Starsmentioning

confidence: 99%

The stellar content of obscured Galactic giant H II regions

Blum

2003

Symp. - Int. Astron. Union

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Near infrared images of the Galactic giant H II region W43 reveal a dense stellar cluster at its center. Broad band JHK photometry of the young cluster and K−band spectra of three of its bright stars are presented. The 2 µm spectrum of the brightest star in the cluster is very well matched to the spectra of Wolf-Rayet stars of sub-type WN7. Two other stars are identified as O type giants or supergiants by their N III and C IV emission. The close spatial clustering of O and the hydrogen WN type stars is analogous to the intense star burst clusters R136 in the Large Magellanic Cloud and NGC 3603 in the Galaxy.

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Interstellar Dust And Extinction

Cited by 763 publications

References 0 publications

A refined analysis of the remarkable Bp star HR 6000

A refined analysis of the remarkable Bp star HR 6000

The fidelity of the core mass functions derived from dust column density data

The stellar content of obscured Galactic giant H II regions

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