Structure and kinematics of the interstellar medium in the star-forming region in the BCD galaxy VII Zw 403 (UGC 6456)

Abstract

Abstract. The structure and kinematics of ionized gas in the star-forming region in the BCD galaxy VII Zw 403 (UGC 6456) are analyzed using observations with the SCORPIO focal reducer on the 6-m Special Astrophysical Observatory telescope in three modes: direct imaging (in the Hα, [OIII], and [SII] lines), long-slit spectroscopy, and spectroscopy with a scanning Fabry-Perot interferometer. In addition to the previously known bright HII regions and the faint giant ring that surrounds the entire star-forming region, many new faint diffuse and arc structures have been detected. Fine structure of the giant ring has been revealed. We do not confirm the previously detected expansion of the bright shells around young stellar associations with a velocity of 50 − 70 km s −1 . We have estimated their expansion velocities to be no higher than 15-20 km s −1 ; the corresponding kinematic age, no younger than 3-4 Myr, agrees well with the age of the compact OB associations related to them. We associate the faint extended filamentary and diffuse regions of ionized gas identified in nearly the entire central region of the galaxy and the giant HII ring with the older (10 Myr) stellar population of the most recent starburst. Weak high-velocity [OIII] and Hα line wings (up to 300 km s −1 from the line center) have been detected in the brightest HII region. Such velocities have been observed in the galaxy for the first time. The previously published Hα luminosity measurements for the galaxy are refined.

Ionized gas rotation curves in nearby dwarf galaxies

“…In order to detect diffuse gas emission away from the regions of star formation, large optical telescopes or hours of scanning cycles at the instruments of small diameters are required. Therefore, most of the observations of dwarf galaxies with the IFP were carried out for the objects with a relatively strong star formation, such as the blue compact galaxies (Ostlin et al, 1999;Lozinskaya et al, 2006). About two dozen dIrr galaxies were also observed within the GHASP survey (Epinat et al, 2008), but an insufficient limit of these observations has often not allowed to build the rotation curves in the galaxies deprived of bright H II regions.…”

Gas and dust in the BCD galaxy VII Zw 403 (UGC 6456)

“…The HST observations have disclosed a shell-like structure of several bright HII regions; Lynds et al [5] measured the shell's expansion velocity of 50 − 70 km/s, however, Lozinskaya et al [4] did not confirm these results. Silich et al [13] found the traces of a faint giant ring sized D ≃ 500 pc in the H α emission of diffuse gas.…”

“…This paper continues a series of our investigations of ionized gas complexes, associated with the latest burst of star formation in the BCD galaxy VII Zw 403 (UGC 6456), presented by Arkhipova et al [3] and Lozinskaya et al [4].…”

“…In this paper we refine the abundances of oxygen, nitrogen and sulfur in certain HII regions from the results of previous observations of VII Zw 403 with the 6-m BTA telescope of the Special Astrophysical Observatory of Russian Academy of Sciences (SAO RAS) [3,4]. Based on the archive data of the Spitzer Space Telescope we investigate the infrared emission of the galaxy with the aim to analyze the distribution of the PAHs and find a possible correlation of q PAH with the radiation brightness of the ionized and neutral gas, as well as with the metallicity of HII regions.…”

“…In our paper [4] we have investigated the structure and kinematics of ionized gas in VII Zw 403. In addition to the previously known bright HII regions and traces of a faint giant ring, many new faint diffuse and arc-shaped structures were found, and a "fine structure" of the giant ring was identified.…”