Engineering topics

Fricke, K. J.

Publications and source records attributed to Fricke, K. J..

3 records

DOE OSTI2021

Lyman continuum leakage from low-mass galaxies with M ⋆ < 108 M⊙

ABSTRACT We present observations with the Cosmic Origins Spectrograph onboard the Hubble Space Telescope of nine low-mass star-forming galaxies at redshifts, z, in the range 0.3179–0.4524, with stellar masses $M_\star \, \lt $ 108 M⊙ and very high specific star-formation rates sSFR ∼150–630 Gyr−1, aiming to study the dependence of leaking Lyman continuum (LyC) emission on stellar mass and some other characteristics of the galaxy. We detect LyC emission in four out of nine galaxies with escape fractions, fesc(LyC), in the range of 11–35 per cent, and establish upper limits for fesc(LyC) in the remaining five galaxies. We observe a narrow Ly α emission line with two peaks in seven galaxies and likely more complex Ly α profiles in the two remaining galaxies. The velocity separation between the peaks Vsep varies in the range from ∼229 to ∼512 km s−1. Our additional data on low-mass galaxies confirm and strengthen the tight anticorrelation between fesc(LyC) and Vsep found for previous low-redshift galaxy samples with higher stellar masses. Vsep remains the best indirect indicator of LyC leakage. It is better than O32 on which fesc(LyC) depends weakly, with a large scatter. Finally, contrary to expectations, we find no increase of fesc(LyC) with decreasing galaxy stellar mass M⋆.

Izotov, Y. I.↗

NASA NTRS1994

Hot gas outflow in the blue compact dwarf galaxy VII Zw 403

We have observed the Blue Compact Dwarf Galaxy VII Zw 403 with the Position Sensitive Proportional Counter (PSPC) camera onboard ROSAT. We found a total X-ray luminosity of 1.94 x 10(exp 38) erg/s distributed in a central core to which are connected three elongated structures. We interpret this X-ray morphology as the result of a hot gas outflow from the core of the dwarf galaxy powered by the present starburst.

Papaderos, P.↗

NASA NTRS1990

Correlations between environmental parameters and nuclear activity

The occurrence and quantitative properties of Seyfert 1 and Seyfert 2 galaxies as a function of the galaxy environment were studied in a systematic way. For this investigation the authors selected from the Catalogue of Quasars and Active Nuclei (Veron & Veron, 1989) all Seyfert galaxies with the following properties: (1) m sub V less than or equal to 15; (2) listed classification as Sey 1, Sey 2, or Sey 3; (3) v sub rad less than or equal to 20,000 km s(sup -1). This results in a sample size of 242 Seyfert galaxies. For all these objects their galaxy environment was inspected on plates. The vicinity of each sample Seyfert galaxy was searched for companion galaxies out to at least 0.5 Mpc. Lacking redshift information, the authors adopted as a companion galaxy any galaxy in this area having a size between 20 and 200 percent of the Seyfert galaxy size. As an important environmental parameter for Seyfert activity, the authors consider the galaxy density within an environment of 500 kpc radius. They distinguish four density classes: D1: no companion (isolated Seyfert); D2: 1 companion; D3: 2 to 5 companions (group); and D4: less than or equal to 6 companions (dense group). The distribution of the various Seyfert classes among these density classes is listed in tabular form, both in absolute numbers and in percentages (given in brackets). From these statistics the environments of Sey 1, Sey 2, and Sey 3 galaxies do not differ in general with the exception that among the isolated galaxies the Seyfert 1 galaxies dominate conspicuously. No significant dependence of morphological type (de Vaucouleurs T-type) on density class is observed both for Sey 1 and Sey 2 galaxies. On the basis of an extensive search of the Seyfert literature the authors also investigated the dependence of the intrinsic parameters of the sample Seyfert galaxies on density class.

Kollatschny, W.↗