O. V. Egorov

Reduction of CCD Observations Made with the Fabry-Perot Scanning Interferometer. II. Additional Procedures

We describe a software package used at the Special Astrophysical Observatory of the Russian Academy of Sciences to reduce and analyze the data obtained with the Fabry-Perot scanning interferometer. We already described most of the algorithms employed in our earlier paper [1]. In this paper we focus on extra procedures required in the case of the use of a high-resolution Fabry-Perot interferometer: removal of ghosts and measurement of the velocity dispersion of ionized gas in galactic and extragalactic objects.

Parameters of the brightest star formation regions in the two principal spiral arms of NGC 628

We study photometric properties, chemical abundances and sizes of star formation regions in the two principal arms of the galaxy NGC 628 (M74). The GALEXultraviolet, optical U BVRI, and Hsurface photometry data are used, including those obtained with the 1.5-m telescope of the Maidanak Observatory. The thirty brightest star formation regions in ultraviolet light lo- cated in the spiral arms of NGC 628 are identified and studied. We find that the star formation regions in one (longer) arm are systematically brighter and larger than the regions in the other (shorter) arm. However, both luminosity and size distribution functions have approximately the same slopes for the samples of star formation regions in both arms. The star formation regions in the longer arm have a higher star formation rate density than the regions in the shorter arm. The regions in the shorter arm show higher N/O ratio at a higher oxygen abun- dance, but they have lower ultraviolet and Hluminosities. These findings can be explained if we assume that star formation regions in the shorter arm had higher star formation rate in the past, but now it is lower than for those in the opposite arm. Results of stellar evolutionary synthesis show that the brightest regions in the longer arm are slightly younger than the ones in the shorter arm (3.5± 2.2 Myr versus 6.0± 1.1 Myr). Our results demonstrate that there is a difference in the inner structures and parameters of the interst ellar medium between the spiral arms of NGC 628, one of which is long and hosts a regular chain of bright star formation complexes and the other, shorter one does not.

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

The structure and kinematics of ionized supershells 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, [O III], and [S II] lines), long-slit spectroscopy, and spectroscopy with a scanning Fabry-Perot interferometer. In addition to the previously known bright H II regions and the faint giant ring that surrounds the entire starforming region, many new faint diffuse and arc structures have been detected. A 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 associated with them. We correlate the faint extended filamentary and diffuse regions of ionized gas identified almost in the entire central region of the galaxy and the giant H II ring with the older (10 Myr) stellar population of the most recent starburst. Weak high-velocity [O III] and Hα line wings (up to 300 km s−1 from the line center) have been detected in the brightest H II region. Such velocities have been observed in the galaxy for the first time. The previously published Hα luminosity measurements for the galaxy are refined.

Dust evolution in the dwarf galaxy Holmberg II

A detailed photometric study of star-forming regions (SFRs) in the galaxy Holmberg II has been carried out using the archival observational data from the far infrared to the ultraviolet obtained with the GALEX, Spitzer, and Herschel telescopes. Spectroscopic observations with the 6-m BTA telescope (Special Astrophysical Observatory of the Russian Academy of Sciences) are used to estimate the ages and metallicities of SFRs. The ages of SFRs have been correlated for the first time with their emission parameters in a wide spectral range and with the physical parameters determined by fitting the observed spectra. It is shown that the fluxes at 8 and 24 µm characterizing the emission from polycyclic aromatic hydrocarbons (PAHs) and hot dust grains decrease with age, but their ratio increases. This implies that the relative contribution from PAHs to the total infrared flux increases with age. It is hypothesized that the detected increase in the ratio of the fluxes at 8 and 24 µm is related to the increase in the relative PAH fraction due to the destruction of larger grains.

Optical and infrared emission of H ii complexes as a clue to the PAH life cycle

We present an analysis of optical spectroscopy and infrared aperture photometry of more than 100 H II complexes in nine galaxies. Spectra obtained with the 6-m telescope of SAO RAS are used along with archival data from Spitzer and several ground-based telescopes to infer a strength of polycyclic aromatic hydrocarbon (PAH) emission, age, properties of the UV radiation field, and metallicity of studied H II complexes. Physical properties (age, radiation field parameters, metallicity) are related to the

Polycyclic aromatic hydrocarbons in the dwarf galaxy IC 10

F_{8}/F_{24}

Stellar counter-rotation in lenticular galaxy NGC 448

ratio used as a proxy for the PAH abundance in order to reveal factors that may influence the PAH evolution in H II complexes. The well-known correlation between the

Outer regions of the merging system Arp 270

F_{8}/F_{24}

Ionized gas characteristics in the cavities of the gas and dust disc of the spiral galaxy NGC 6946

ratio and metallicity is confirmed in the studied complexes. The infrared flux ratio also correlates with the [O III]

Gas emission spectrum in the Irr galaxy IC 10

\lambda 5007/\mathrm{H\beta}