A spectral and photometric study of 102 star-forming regions in seven spiral galaxies

Abstract

We present a study of complexes of young massive star clusters (YMCs), embedded in extragalactic giant H ii regions, based on the coupling of spectroscopic with photometric and spectrophotometric observations of about 100 star forming regions in seven spiral galaxies (NGC 628, NGC 783, NGC 2336, NGC 6217, NGC 6946, NGC 7331, and NGC 7678). The complete observational database has been observed and accumulated within the framework of our comprehensive study of extragalactic star forming regions. The current paper presents the last part of either unpublished or refreshed photometric and spectrophotometric observations of the galaxies NGC 6217, NGC 6946, NGC 7331, and NGC 7678. We derive extinctions, chemical abundances, continuum and line emissions of ionised gas, ages and masses for cluster complexes. We find the young massive cluster complexes to have ages no greater than 10 Myr and masses between 10 4 M ⊙ and 10 7 M ⊙ , and the extinctions A V vary between ∼ 0 and 3 mag, while the impact of the nebular emission on integrated broadband photometry mainly is not greater than 40% of the total flux and is comparable with accuracies of dereddened photometric quantities. We also find evidence of differential extinction of stellar and gas emissions in some clusters, which hinders the photometric determination of ages and masses in these cases. Finally, we show that young massive cluster complexes in the studied galaxies and open clusters in the Milky Way form a continuous sequence of luminosities/masses and colour/ages.

Unveiling the 100 pc scale nuclear radio structure of NGC 6217 with e-MERLIN and the VLA

“…15, and therefore have brightness temperatures too low to claim a clear AGN activity. However, these do not align with the star forming regions found by Gusev et al (2012) and Gusev et al (2016) in NGC 6217. The source found in the spiral arms (Panel B in Figure 2) shows an extended structure and is co-incident with a 3σ Spitzer source.…”

Propagation of star formation at sub-kiloparsec scales

“…Unfortunately, we are not able to study the H ii morphology directly on scales of < 40 pc, because our angular resolution is 1-1.5 arcsec. However, as was shown in Gusev et al (2016), the distance between photometric centres of gas emission and star clusters correlates within a single star formation region with the relation between stellar and gas absorption, depending on the age, and can be used as an evolutionary indicator. The diagrams in Fig.…”

“…This effect is clearly illustrated in Fig. 19 in Gusev et al (2016). Due to the impossibility of finding an age by U − B colour for low-massive clusters, we excluded star clusters with masses < 5 • 10 3 M ⊙ from further consideration (green dots in Fig.…”

Azimuthal propagation of star formation in nearby spiral galaxies: NGC 628, NGC 3726 and NGC 6946

“…That is, the substance in the disc of NGC 3726 rotates in a counter clockwise direction. The circle itself with radius R C3 = 9.8 ± 1.0 kpc is the corotation circle, where the rotational ve- Gusev et al 2015Gusev et al , 2016. locity of the matter in the disc coincides with the rotational velocity of the spiral pattern.…”

“…The upper panel shows the SC-HiiR pairs outside spiral arm 1 as filled squares, the SC-HiiR pairs in spiral arm A are shown as open circles. The bottom panel shows the face-on B-image of NGC 6946 from our earlier papers (seeGusev et al 2015Gusev et al , 2016.…”