The Homogeneity of Interstellar Oxygen in the Galactic Disk

Cartledge, Stefan I. B.; Lauroesch, J. T.; Meyer, David M.; Sofia, U. J.

doi:10.1086/423270

Cited by 132 publications

(168 citation statements)

References 54 publications

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“…We thus complement the probably most comprehensive benchmark test for stellar atmosphere modelling of OB stars to date Sofia & Meyer (2001); ( f ) value determined from strong-line transitions (Sofia et al 2011), which is compatible with data from the analysis of the [C ii] 158 μm emission (Dwek et al 1997). Weak-line studies of C ii] λ2325 Å indicate a higher gas-phase abundance ε(C) = 8.11 ± 0.07 (Sofia 2004), which corresponds to 84 ± 28 ppm of carbon locked up in dust; (g) Meyer et al (1997), corrected accordingly to Jensen et al (2007); (h) Cartledge et al (2004); (i) Cartledge et al (2006). The uncertainty in the ISM gas-phase abundances is the standard error of the mean; ( j) difference between the cosmic standard and ISM gas-phase abundances, in units of atoms per 10 6 H nuclei; (k) photospheric values of Grevesse & Sauval (1998, GS98), Asplund et al (2009, AGSS09) and Caffau et al (2010, CLSFG10).…”

Section: Global Spectrum Synthesissupporting

confidence: 79%

“…The abundance distributions are very similar, see Fig. 15 for the example of oxygen (the gas-phase abundance distribution is based on 37 diffuse sightlines of Cartledge et al 2004). From this it follows immediately that the dust-phase is chemically also rather homogeneous, what can be expected if mixing processes are highly efficient within the ISM (Sect.…”

Section: Dust Composition Of the Local Ismmentioning

confidence: 58%

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Present-day cosmic abundances

Nieva

Przybilla²

2012

A&A

431

506

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Context. Early B-type stars are ideal indicators for present-day cosmic abundances since they preserve their pristine abundances and typically do not migrate far beyond their birth environments over their short lifetimes, in contrast to older stars like the Sun. They are also unaffected by depletion onto dust grains, unlike the cold/warm interstellar medium (ISM) or H ii regions. Aims. A carefully selected sample of early B-type stars in OB associations and the field within the solar neighbourhood is studied comprehensively. Quantitative spectroscopy is used to characterise their atmospheric properties in a self-consistent way. Present-day abundances for the astrophysically most interesting chemical elements are derived in order to investigate whether a present-day cosmic abundance standard can be established. Methods. High-resolution and high-S/N FOCES, FEROS and ELODIE spectra of well-studied sharp-lined early B-type stars are analysed in non-LTE. Line-profile fits based on extensive model grids and an iterative analysis methodology are used to constrain stellar parameters and elemental abundances at high accuracy and precision. Atmospheric parameters are derived from the simultaneous establishment of independent indicators, from multiple ionization equilibria and the Stark-broadened hydrogen Balmer lines, and they are confirmed by reproduction of the stars' global spectral energy distributions. Results. Effective temperatures are constrained to 1-2% and surface gravities to less than 15% uncertainty, along with accurate rotational, micro-and macroturbulence velocities. Good agreement of the resulting spectroscopic parallaxes with those from the new reduction of the Hipparcos catalogue is obtained. Absolute values for abundances of He, C, N, O, Ne, Mg, Si and Fe are determined to better than 25% uncertainty. The synthetic spectra match the observations reliably over almost the entire visual spectral range. Three sample stars, γ Ori, o Per and θ 1 Ori D, are identified as double-lined, indicating the presence of an early/mid B-type companion. Conclusions. A present-day cosmic abundance standard is established from a sample of 29 early B-type stars, indicating abundance fluctuations of less than 10% around the mean. Our results (i) resolve the long-standing discrepancy between a chemical homogeneous gas-phase ISM and a chemically inhomogeneous young stellar component out to several hundred parsec from the Sun, (ii) facilitate the amount of heavy elements locked up in the interstellar dust to be constrained precisely -the results imply that carbonaceous dust is largely destroyed inside the Orion H ii region, unlike the silicates, and that graphite is only a minority species in interstellar dust -, (iii) show that the mixing of CNO-burning products in the course of massive star evolution follows tightly the predicted nuclear path, (iv) provide reliable present-day reference points for anchoring Galactic chemical evolution models to observation, and (v) imply that the Sun has migrated outwards from the inne...

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Section: Global Spectrum Synthesissupporting

confidence: 79%

Section: Dust Composition Of the Local Ismmentioning

confidence: 58%

Present-day cosmic abundances

Nieva

Przybilla²

2012

A&A

431

506

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“…If we do so, we find that a CLOUDY model with log U % À4:4 gives a generally acceptable fit to the observations for most of the low ions, but with a glaring exception for N i. From the flatness of the predictions for O i and the tight error limits associated with our observation of N(O i), together with the knowledge that O usually is only mildly depleted in the ISM of our Galaxy (Cartledge et al 2001(Cartledge et al , 2004André et al 2003), we may state that the most secure measure of an overall metallicity is given by ½O/H ¼ À0:20 AE 0:07, which represents the distance the measurement is below the model prediction for a solar abundance ratio. The abundances of other elements depend more sensitively on the assumed value for log U.…”

Section: An Initial Choice For the Ionization Parametermentioning

confidence: 59%

A Near‐Solar Metallicity, Nitrogen‐deficient Lyman Limit Absorber Associated with Two S0 Galaxies

Jenkins

Bowen

Tripp³

et al. 2005

ApJ

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The UV spectrum of the bright quasar PHL 1811 at z em ¼ 0:192 reveals a foreground gas system at z ¼ 0:080923 with log N (H i) ¼ 17:98 AE 0:05. We have determined the abundances of various atomic species in this system from a spectrum covering the wavelength range 1160-1730 8 recorded at 7 km s À1 resolution by the E140M grating of the Space Telescope Imaging Spectrograph (STIS) on the Hubble Space Telescope (HST ), supplemented by coverage at shorter wavelengths by the Far Ultraviolet Spectroscopic Explorer (FUSE ). The abundances of C ii, Si ii, S ii, and Fe ii compared to that of O i indicate that a considerable fraction of the gas is in locations where the hydrogen is ionized. An oxygen abundance ½O/ H ¼ À0:19 AE 0:08 in the H i-bearing gas indicates that the chemical enrichment of the gas is unusually high for an extragalactic QSO absorption system. However, this same material has an unusually low abundance of nitrogen, ½N/ O < À0:59, indicating that there may not have been enough time during this enrichment for secondary nitrogen to arise from low-and intermediate-mass stars. From the convergence of high Lyman series lines we can determine the velocity width of H i, and after correcting for turbulent broadening shown by the O i absorption feature, we derive a temperature T ¼ 7070 þ3860 À4680 K. We determine a lower bound for the electron density n(e) > 10 À3 cm À3 by modeling the ionization by the intergalactic radiation field and an upper bound n(e) < 0:07 cm À3 from the absence of much C ii in an excited fine-structure level. The thermal pressure in the range 4 cm À3 K < p / k < 140 cm À3 K could be confined by a warm-hot intergalactic medium (WHIM) structure with /¯$ 20 that might accompany a wall of galaxies at the same redshift, seen in data from the Sloan Digital Sky Survey. An r-band image of the field surrounding PHL 1811 recorded by the ACS instrument on HST shows that two galaxies at the same redshift as the gas are S0 galaxies, separated by only 34 and 87 h À1 70 kpc from the line of sight. One or both of these galaxies may be the source of the material in the Lyman limit system, which may have been expelled from them in a fast wind, by tidal stripping, or by ram pressure stripping. Subtraction of the ACS point-spread function from the image of the QSO reveals the presence of a face-on spiral galaxy under the glare of the quasar; while it is possible that this galaxy may be responsible for the Lyman limit absorption, the exact alignment of the QSO with the center of the galaxy suggests that the spiral is the quasar host.

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“…The IDL 3 routine STISEXTRACT ( Howk & Sembach 2000) was developed in order to reliably estimate the on-order flux background in highresolution (R % 114;000) STIS echelle spectra; experimentation has shown that improvements to the CALSTIS spectral extraction algorithm included with STSDAS now reliably reproduce the central zero-flux level for saturated absorption profiles in the output spectra. However, in the interest of consistency with procedures adopted by Cartledge et al (2001Cartledge et al ( , 2003Cartledge et al ( , 2004 in publishing the krypton and oxygen abundances for these sight lines, STISEXTRACT was used for each E140H observation. The standard CALSTIS extraction algorithm was used for each medium resolution (R % 45;800) exposure.…”

Section: Observations and Data Extractionmentioning

confidence: 99%