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1

A Comparison of c-C3H2 and l-C3H2 in the Spiral Arm Clouds

Kulczak-Jastrzębska M., Lis D., Gerin M.

Acta Astronomica

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2012

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Vol. 62, No. 3

313--321

EN

Using the IRAM 30-m telescope, we observed molecular absorption lines from c-C3H2 produced in diffuse clouds toward the high-mass star forming regions W51 e1/e2 and W49N to determine the abundance ratio between the cyclic and linear isomers of C3H2 (Nc/Nl). The abundance ratio is found to be 3-5 in the sources where l-C3H2 was previously detected. A possible source of uncertainty in the determination of Nc/Nl is related to the estimate of N(c-C3H2). The main goal of this paper is verification of this hypothesis.

2

Composition of the Interstellar Medium

Gnaciński P., Krogulec M.

Acta Astronomica

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2006

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Vol. 56, No. 4

373--384

EN

We present an analysis of the FeII, GeII, MgI, MgII, SI, SII, SiII and ZnII interstellar lines for 63 stars. Column density of MgII, SII, SiII and ZnII is well correlated with distance. However, the column density - distance relation should be used with care for the estimation of the distance to OB stars. For stars with large f(H2) this relation can lead to a large overestimation of the distance. The column densities of MgII, SiII and GeII (our largest samples of data) normalized to their total hydrogen column densities decrease with interstellar reddening E(B-V) as expected for elements that are incorporated into dust grains. The GeII abundance (GeII/H) is lower in dense molecular clouds. The abundances of all analyzed elements are generally lower than their Solar System values.

3

Deuterium Depletion and Magnesium Enhancement in the Local Disk

Gnaciński P.

Acta Astronomica

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2005

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Vol. 55, No. 4

407--413

EN

The local disk deuterium is known to be depleted in comparison to the local bubble. We used Hubble Space Telescope (HST) spectra to obtain column densities of Si, Mg and Fe. We compared normalized column densities of these elements in the directions with high and low deuterium abundances. We show, that the lines of sight that are depleted in deuterium, are enhanced in magnesium. This observation implicates that astration is responsible for both deuterium depletion and magnesium enhancement.

4

Interstellar Silicon Abundance

Gnaciński P.

Acta Astronomica

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2003

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Vol. 56, No. 4

379--390

EN

We present 34 measurements of silicon gas phase column densities in the interstellar medium. We have used spectra containing the Si II 1808 Å line which were obtained with the Goddard High Resolution Spectrograph (GHRS) aboard the Hubble Space Telescope (HST). Extinction curve parameters are determined for analyzed lines of sight and relation between Si/H ratio and extinction parameters is discussed. We find the abundance of gas phase silicon in diffuse clouds to be lower than the solar value by a factor of four.

5

Interstellar Carbon Abundance

Gnaciński P.

Acta Astronomica

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2000

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Vol. 50, No. 1

133--149

EN

We present 10 new measurements of carbon gas phase column density in the interstellar medium. We have used spectra made with the Goddard High Resolution Spectrograph aboard the Hubble Space Telescope containing the CII 1334.5 Å and CII* 1335.7 Å lines. The continuum reconstruction method has been used to obtain the carbon column density from the Lorentzian damped lines. Extinction curve parameters are determined in selected directions and relation between C/H ratio and extinction parameters is discussed. A correlation has been found between C/H and the strength of the 2175 Å bump. Unlike previous results, we notice that C/H changes with fractional abundance of molecular hydrogen, f(H2). The average value of C/H=3.55×10-4 for lines of sight with f(H2)<1×10-3 is the same as solar photospheric abundance from Grevese and Noels (1993) and may represent the real cosmic carbon abundance.

6

Interstellar C2 Toward X Persei (HD 24534)

Kaczmarczyk G.

Acta Astronomica

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2000

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Vol. 50, No. 1

151--162

EN

Interstellar C2 bands D-X (2313 Å) and F-X (1342 Å) in the spectrum of X Per were detected in the archive echelle spectra acquired by the Goddard High Resolution Spectrograph (GHRS) aboard the Hubble Space Telescope. The population of C2 rotational levels was determined from the rotational lines in the D-X band to obtain kinetic temperature Tk=45±15 K. The total C2 column density N(C2)=(3.4±0.5)×1013 cm-2 was calculated using the D-X band with f-value of 0.0545. The analysis of F-X band with an adopted f-value of 0.1 gave different population of rotational levels of C2. Possible reasons of this discrepancy are discussed. The FWHM of the C2 line profile was estimated to be ΔV=2.7±1.0 km/s.